CAOS 2019:Papers with Abstracts

Abstract. Introduction
Patient specific instrumentation is a novel aid the industry has been implementing in our hospitals during the last years. However, the cost of the process and the impossibility to discuss face to face with the manufacturer the needs of the particular cases may favor the in-hospital production of these devices.

We present the design and manufacturing process of three patient-specific devices to treat complex common situations in orthopaedic surgery, such as intramedular tumor resections, long bone pseudarthrosis and malunions of articular fractures.

Material and Methods
CT scans of the region of interest were performed to all the patients. Horos® software was used to isolate the affected bone region, whereas Meshmixer® software was used to create the patient specific guides. An Ultimaker 2+® 3D printer was used to print the guide, in a biocompatible material (SmartFil® Medical). The printing parameters included a nozzle of 0.6 mm and a layer height of 0.1 mm.
There was one case of a low-grade chondrosarcoma in which we created a guide to resect enough cortical bone to make an extended curettage of the lesion. Phenol and PMMA were used as adjuvants after the curettage. We used the same guide to obtain an exact replica of allograft which was later placed in position.
We had a femur diaphyseal atrophic pseudarthrosis in a patient with achondroplasia, in which the guide permitted the resection of the affected bone with a saw and posterior osteosynthesis with an anterior LCP plate.
Finally, in an intraarticular malunion of a distal radius Die-Punch fracture we used the guide to make an osteotomy of the affected articular portion and correct the articular surface. Bone autograft was added prior to the osteosynthesis with a plate.

Mean design time was 6.3 hours. Mean printing time was 5.2 hours. The price of the filament used for each guide was under 10 USD. The mean time from the CT-Scan and the surgery being performed was 2.7 months. In all cases the patient specific guides fitted in the bone and permitted the planned resection/osteotomy.
All the surgeries fulfilled their purpose.

Patient specific guides are easy to design in a local setting with the aid of free software. Design time still needs dedication although it permits the manufacturing of the guides following surgeon needs. The use of self-designed and printed guides is safe and accurate, with a low cost for the institutions.
Abstract. Accurate, robust, and real-time segmentation of bone surfaces is an essential objective for ultrasound (US) guided computer assisted orthopedic surgery (CAOS) procedures. In this work, we present a convolutional neural network (CNN)-based technique for segmenting spine surfaces from in vivo US scans. Proposed design utilizes fusion of feature maps extracted from multimodal images to abate sensitivity to variations caused by imaging artifacts and low intensity bone boundaries. In particular, our multimodal inputs consist of B-mode US images and their corresponding local phase filtered counterparts. Validation studies performed on 261 in vivo US scans obtained from 10 subjects achieved a mean localization accuracy of 0.1 mm with an F-score of 97%. Comparison against state-of-the-art CNN networks show an improvement of 89% in bone surface localization accuracy.
Abstract. Despite the increasing use of 3D printing in orthopedic surgery, there is no established method for the validation of a printed bone model. A printing error could potentially lead to complications, especially when the model is used for surgery planning. We aimed to validate a series of 33 acetabular fractures with a novel method by detailed analysis of model errors.
After applying a surface filter on both the patients model and the 3D printed model, a two-step registration consisting of landmark-based pre-registration and ICP-registration, was slightly varied and conducted 100 times, yielding a mean surface deviation and standard deviation for each model surface point.
We furthermore showed that more than 30 random ICP-registration points lead to a sufficiently good registration, and that the variation of the pre-registration is small enough to guarantee a stable ICP registration result.
Deviations caused by failed registration are unveiled by a large standard deviation of the 100 registration routines. For the fracture series, the mean surface deviation error between the printed model and the patient model was less than 1 mm (median = 0.7 mm; 95% CI = 0.68-0.72 mm). The largest errors were found in areas with remaining support structure material, on printbed-facing model sides and on abrasive surface regions. By visualizing the residual registration error, it was possible to clearly detect surface deviations and to quantify them.
Abstract. Minimal invasive surgery has gained popularity among hip surgeons and patients. Based on early studies, the method is described as a very promising alternative, with low dislocation rates, resulting in a non-traumatic procedure and early functional return. However, complication rates arising of the recent studies raise concern about the applied technique. The aim of the study is to present the clinical results and intra- and post-operative complications of the AMIS procedure in patients with osteoarthritis of the hip, managed with total hip arthroplasty with positioning table, in a 5 years follow up. One senior hip arthroplasty surgeon performed all surgeries. Three hundred eighteen consecutive patients (195 females, 123 males) were clinically and radiologically evaluated, postoperatively 2, 6 and 12 months. Mean patient age was 69.7 years (24 to 88). There was significant improvement according to Harris-Hip Score, ODI, SF-36 scales. The mean incision length was 7.5cm (6 to 8cm). The mean operating time was calculated at 85 minutes. The patients were discharged on the second post-operative day, able to walk with partial weight bearing. One month post-operative, the patients were advised for full weight bearing walking without crutches. Intraoperative complications included two femoral perforations. Postoperative complications included two patients with femoral fractures; one with dislocation; two with superficial infections; three with wound complications; three with femoral stem aseptic loosening; one with ceramic inner fracture and two acetabular component protrusion in the same patient, among which only the last patient had reoperation in both hips. Anterior Minimal Invasive Surgery of the hip is a non-traumatic procedure, associated with reduced pain, faster recovery and no major complications, but requires higher experience level from the hip surgeon.
Abstract. The sagittal geometry of the articular surfaces of the femoral condyles, also called J-Curves because of the letter J-shaped profiles, is one of the main factors affecting knee kinematics in the normal knee
[1] as well as artificial knee [2]. For example, Clary et al. [2] showed that large changes in the J-curves’ radii cause abrupt changes in the center of rotation, leading to decreased anterior-posterior stability. In literature, the sagittal profile has been described mathematically by different geometric figures, such as arcs, circles, involutes of a circle, and Archimedean and logarithmic spirals [3]. The circular approximation has been often followed in the different concepts of knee implant designs, such as single- radius-, dual-radius-, or multiple-radius-designs. Single-radius-designs have a fixed flexion-extension axis. Dual-radius-designs consist of a larger distal and smaller posterior radius aiming a higher congruence during low flexion (high loading) and lower congruence at high flexion angles (high mobility). Multi-radius-designs try to mimic a physiological roll-glide ratio. However, the description of these circles is usually not standardized. A summary of different measurement methods was given by Nuno and Ahmed [4].
Thereby, the radii are very sensitive regarding the length of the fitting arc [5] and position of the sagittal plane [3]. Nuno and Ahmed [3] found that medial and lateral condyles can be adequately described by two-circular arcs and proposed a quantitative description. However, the posterior limits of their arcs were not considered individually, the anterior limits were defined based on soft-tissue measurements (anterior margins of the menisci), and the sagittal plane was positioned at the posterior extreme points, which might be inadequate in arthritic knees.
The goal of this study was to automatically analyse the medial and lateral sagittal profiles of the femoral condyles mathematically by two-circular arcs in a standardized and robust fashion.
Abstract. An important factor which influences the clinical outcome of total knee arthroplasty (TKA) is the internal/external rotational alignment of the femoral and tibial components. A rotational error of few degrees has been found to be clinically important and linked to anterior knee pain [1] and patellofemoral problems [2]. A commonly used reference to align the tibial component rotationally is the tibial tuberosity (TT). However, Howell et al. [3] showed that the medial/lateral TT position varies strongly between patients and represents an unreliable landmark during (passive) kinematic component alignment. Thereby, passive kinematics differs from active kinematics [4,5]. For example, under weight-bearing conditions the magnitude of internal/external rotation is greater and occurs earlier [6]. In the active situation, a relative internal rotation of the tibial component increases the Q-angle with a change in the force vector of the extensor mechanism.
An established radiographic measure to quantify the relative rotational alignment of the femur and tibia in extension is the tibial tuberosity-trochlear groove (TT-TG) distance. It has been measured recently at different flexion angles under non-weight-bearing conditions [7]. However, Izadpanah et al. [8] reported that it also depends on weight-bearing. Hence, the complex function of the extensor mechanism in terms of the relationship between TT position, TT-TG distance, and internal/external rotation under weight-bearing conditions is still unknown and accordingly component rotational alignment targets.
The aim of the study was to investigate the relationship between TT position, TT-TG distance, and internal/external rotation of the knee in the active (weight-bearing) situation.
Abstract. Morphological knowledge about the patella is fundamental to understand normal and pathological knee joint mechanics and guide the design of patellar prosthesis. In literature there are a large number of parameters and measurement methods described to characterize the patellar morphology. However, the majority rely on manual measurements, sample sizes are often small and the number of morphological parameters is limited. The goal of this study was to identify morphological parameters of the patella, develop a standardized and fully automatic workflow for their extraction, and to provide accurate statistical numbers for a large number of patients.

An anonymized dataset of 412 knee geometries from consecutively scheduled total knee arthroplasty patients (gender: 248 female, 164 male) were available. A total number of 8 morphological parameters were identified and later used for the calculation of 3 additional aspect ratios. A fully automatic workflow was developed for parameter extraction based on the three-dimensional surface data. The workflow was applied to all datasets and the results were stored in a database for statistical analysis.

The workflow could process all 412 patellar geometries fully automatic without any algorithmic adjustment or user interaction. The processing time was in the range of 30 s per case. The results of the statistical analysis were in very good agreement with the literature. The numbers clearly demonstrated gender-specific differences, however, it is still unknown whether these are sexual dimorphism or can be eliminated by a scaling. Extensive statistical analysis on gender-specific differences and their normalization is part of future work.
Abstract. Osteoarthritis is the degeneration of bone-cartilage. Healthy cartilage absorbs mechanical stress and provides smooth limb movement. Cartilage has poor healing capabilities due to the absence of blood, lymphoid tissue, and nerve that makes treatment of the damaged cartilage difficult, making surgical intervention an inevitable solution. Mosaicplasty is a popular surgical practice involving transplantation of small cylindrical bone-cartilage plugs to refill the lesion. A lack of custom-shaped donor harvesting mechanism makes it impossible to fill the lesion with a single graft. The success of transplanting a customized autograft to replace the osteochondral lesion lies in effective extraction of the autograft from the donor site. Currently, no method exists to harvest such grafts since it requires access to the root side of donor. In this paper, we propose a robotic cartilage-bone removal mechanism to harvest a custom-shaped autograft. Our method involves drilling a profile determined from the lesion to be removed and slicing off the desired cartilage-bone graft from the root. We designed a new graft removal mechanism capable of inserting a thin wire saw and slicing through the root of the prepared profile to extract an intact autograft. The device can be attached to a standard 6- DOF robotic arm that can provide profile drilling and gross positioning of the graft removal device.
Abstract. Total knee arthroplasty is a successful procedure. However, there is still area for improvement as up to 15-20% of patients remain unsatisfied. Robotic-assisted surgery (RAS) may improve patient outcomes by providing a reproducible way of obtaining neutral mechanical alignment of the limb, which has been shown to reduce early revisions and correlate with patient reported outcomes after surgery.
We prospectively enrolled 106 patients undergoing robotic-assisted TKA by a single surgeon performing a measured-resection femur-first technique using the OMNIBotic system. Patients completed a KOOS and New Knee Society Score (KSS) pre-operatively and at 3, 6, 12, and 24 months (M) postoperatively. Changes in the five KOOS sub-scales were compared to available literature data from the FORCE – TJR cohort, as well as to individual studies reporting on conventional and computer-assisted TKA.
When compared to FORCE-TJR 6-month (M) and 2-year (Y) data, the RAS cohort had significantly higher improvements at 6M for pain (40.5 vs. 31.1, p<.001) and at 2Y for all five KOOS sub-scores. The larger improvement was due to the RAS cohort having lower baseline KOOS scores than the FORCE-TJR cohort, except for the Sports-Recreation sub-score, which was similar pre- operatively but significantly higher post-operatively for the robotic cohort. Rates of dissatisfaction with knee pain level and function using the KSS after RAS were 3.0%, 1.0%, and 2.7% at 6, 12, and 24M postoperatively, respectively.
Despite having poorer joint function and higher pain pre-operatively, robotic-assisted TKA patients achieved excellent self-reported outcomes, with significantly higher levels of improvement through two years post-surgery when compared with large national cohort studies. Further controlled clinical studies are warranted to determine if these results translate to other groups of surgeons, centers and patients.
Abstract. This study investigated global variations in the surgical methods used with a contemporary CAOS system in TKA. Individual surgical profiles were identified from a database of technical reports on all TKA cases performed using a CAOS system. The profiles were divided into groups based on geographic regions (US, EU, and APAC), implant types (CR and PS), and application years. Differences were found in the surgeons’ preferences of surgical parameters and methods, reflecting the existence of variabilities in how surgeons perform TKA.
Abstract. BACKGROUND: The typical goal of TKA is to obtain a neutral mechanical axis of the leg. The NAVIO® Surgical System (Smith & Nephew, Pittsburgh, PA, USA) is aimed at reducing technical errors and outliers. The aim of this study is to assess the surgeons’ learning curve and limb alignment in TKA.
The first sixty-nine patients who underwent TKA with the NAVIO system by two experienced surgeons were included in this study. Pre- and postoperative mechanical limb alignment and balancing was measured by the NAVIO system. Registration time, planning time and cutting time was monitored preoperatively by the NAVIO™ system. All data was analyzed retrospectively.
The mean preoperative mechanical limb alignment was 3.18° varus (SD 4.28°, range 15.08° varus to 4.30° of valgus). The mean intraoperative planned angle was 0.59° varus (SD 0.97°, range 2.50° varus to 0.99° valgus). The mean postoperative alignment was 1.17° varus (SD 1.78°, range 4.52° varus to 4.33° valgus. The mean extra surgical time (EST) for registration and planning decreased from 23.4min (SD 3.7min) to 13.2min (SD 2.0) throughout the learning curve with a range of 10min05sec to 28min19sec.CONCLUSION: The NAVIO robotic system is a valuable tool in assisting total knee arthroplasty. It allows the surgeon to accurately determine optimal implant position for each patient and minimize statistical outliers in alignment.
Abstract. Despite the advantages of real time alignment assessment and visual feedback while balancing offered by robotic assisted total knee arthroplasty, few clinical studies have reported patient outcomes. The purpose of this study is to report the midterm patient reported outcomes and survivorship of a computer-navigated TKA system with a robotic cutting guide. This patient cohort is the first IRB approved series of patients treated in the United States with this robotic knee system. This study serves as a midterm follow-up study on for this cohort, upon which learning curve, intra-operative efficiency, and deformity management were previously reported
Recipients of 152 consecutive total knee arthroplasties using a computer- navigated TKA system performed by a single surgeon between June 2010 and January 2012 were surveyed between 5-7 years post-operatively. 94 patients were reachable for outcome measures and survivorship data was obtained in 98 patients. Mean patient age at follow up was 74.6 +/- 8.6 years. Implant survivorship was 99.0% at an average of 6.5 years. Mean patient reported knee outcome scores were 62.7 (KSS-SF) and 79.5 (KOOS-JR). Overall satisfaction rate was reported as “satisfied or very satisfied” in 80.2%, “neutral” in 11.0%, and “dissatisfied or very dissatisfied” in 7.7% of patients.
Robotic assisted total knee arthroplasty using a computer-navigated TKA system with a robotic cutting guide appears to provide a durable outcome with sustainable midterm patient reported outcomes and excellent survivorship. Further follow up is required to determine if there are long term outcome and survivorship benefits of robotic assisted total knee arthroplasty.
Abstract. INTRODUCTION: Computer-assisted hip navigation offers more accurate placement of hip components, potentially avoiding impingement, edge-loading, and dislocation; major causes of failure leading to revision THA. As such, the use of computer navigation may be particularly beneficial in the revision THA population. The purpose of this study was to determine if the use of computer-assisted hip navigation reduced the rate of dislocation in patients undergoing revision THA.

METHODS: A retrospective review of 72 patients undergoing computer-navigated revision THA between February 2016 and May 2017 was performed. Demographics, indications for revision, type of procedure performed, and postoperative complications were collected for all patients. Clinical follow-up was recorded at 3-months, 1-year and 2-years.

RESULTS: All 72 patients (48% female; 52% male) were included in the final analysis. Mean age of patients was 70.4 ± 11.2 years. Mean BMI was 26.4 ± 5.2 kg/m2. The most common indications for revision THA were instability (31%), aseptic loosening (29%), osteolysis/eccentric wear (18%), infection (11%), and miscellaneous (11%). At 3-months, 1-year, and 2-years there were no dislocations in any patients (0%). Compared to preoperative dislocation values, there was a significant reduction in the rate of dislocation with the use of computer-assisted hip navigation (31% vs. 0%; p<0.05).

DISCUSSION: Our study demonstrates a significant reduction in the rate of dislocation following revision THA with the use of computer navigation. Although the cause of postoperative dislocation is often multifactorial, the use of computer-assisted surgery may help to curtail femoral and acetabular malalignment in revision THA.
Abstract. INTRODUCTION: Pelvic positioning during total hip arthroplasty (THA) can affect the functional position of the acetabular component. A comprehensive understanding of pelvic orientation prior to THA is necessary to allow for proper cup positioning and mitigate the risks of complications associated with component malpositioning. Measurements using anteroposterior (AP) radiographs have been described as an effective means of accurately predicting pelvic functional orientation. The purpose of our study was to describe the accuracy of assessing pelvic tilt using AP radiographs alone.

METHODS: An online survey was created and sent to a cohort of fellowship-trained adult reconstruction surgeons. The survey consisted of 65 standing AP pelvis radiographs. Participants were asked to score each radiograph as 1) anterior pelvic tilt > 10 degrees, 2) posterior pelvic tilt > 10 degrees, or 3) neutral. Responses were then compared to measurements of pelvic tilt made on lateral standing pelvic radiographs. Categorical and continuous variables were compared using chi-squared, unpaired, two-tailed student’s T tests, and ANOVA.

RESULTS: 135 surgeons completed the survey. The average correct predictive value of pelvic tilt between all surgeons was 53.2%. 51.2% of responding surgeons performed greater than 100 cases per year. 50% of surgeons reported that they were “not so familiar” or “somewhat familiar” with the principles of spinopelvic mobility. 43.5% of surgeons reported that they did not routinely use spinopelvic mobility principles in THA planning.

DISCUSSION: The standing AP pelvis radiograph is poorly predictive of pelvic tilt. Pre-operative evaluation of spinopelvic parameters requires AP and lateral pelvic views for detailed assessment and accurate pre-operative planning.
Abstract. Introduction
This study performed a healthcare utilization analysis between robotic-arm assisted and manual TKA techniques at three intervals to better understand intra-episode trends that can lead to optimized care pathways. Specifically, we compared: (1) index costs; and (2) discharge dispositions; as well as (3) 30-; (4) 60-; and (5) 90- day: a) total episode-of-care costs, b) post-operative healthcare utilization, and c) readmissions.

The Medicare 100% Standard Analytical Files was queried for robotic and manual TKAs (rTKA and mTKA) performed between January 1, 2016 and March 31, 2017. Based on strict inclusion and exclusion criteria, and 1:5 propensity score matching, 519 robotic and 2,595 manual TKA patients were analyzed. Total episode payments, healthcare utilization, and readmissions, at 30-, 60-, and 90-day time points were compared between cohorts with a generalized Linear Model, Binomial Regression, log link, Mann-Whitney, and Pearson's Chi Squared tests with p<0.05 for statistical significance.

The robotic vs. manual cohort average total episode payment was $17,768 vs. $19,899 (p<0.0001) at 30-days; $18,174 vs. $20,492 (p<0.0001) at 60-days; and $18,568 vs. $20,960 (p<0.0001) at 90-days. At 30 days, 47% fewer rTKA patients utilized SNF services (13.5 vs. 25.4%, p<0.0001 and had lower SNF costs at 30- ($6,416 vs. $7,732; p = 0.0040), 60- ($6,678 vs. $7,901, p=0.0072), and 90-days ($7,201 vs. $7,947, p=0.0230). rTKA patients also utilized fewer home-health visits and costs at each time point (p<0.05). Additionally, 31.3% fewer rTKA patients utilized emergency room services at 30-days postoperatively. The robotic cohort had significantly fewer 90-day readmissions (5.20 vs. 7.75%; p=0.0423).

Robotic TKA is associated with significantly lower 30-, 60-, and 90-day post- operative costs and healthcare utilization. These results are of marked importance given the emphasis to contain and reduce healthcare costs for total joints arthroplasties. This analysis provides initial economic insight into robotic-arm assisted TKA with promising results.
Abstract. Introduction
One way to potentially help contain the rising healthcare costs is the utilization of technological advances, such as robotic-assistive technology, for total knee arthroplasty (TKA). Therefore, the purpose of this study was to perform a cost analysis between robotic-arm assisted TKA and manual TKA (mTKA) techniques. Specifically, we compared: 1) 90-day EOC costs, as well as several variables within the episode, including 2) index costs; 3) index lengths-of-stay (LOS); 4) discharge disposition; and 5) readmission rates.

A retrospective claims analysis was performed on Medicare FFS beneficiaries who underwent rTKA and mTKA procedures between January 1, 2016 and March 31, 2017. Patients were matched rTKA to mTKA in a 1-to-5 ratio, yielding 519 rTKAs and 2,595 mTKAs. The overall 90-day EOC costs, including the index procedures, LOS, discharge dispositions, and readmissions were compared between cohorts.

Overall 90-day EOC costs ($18,568 vs. $20,960) as well as index facility costs ($12,384 vs. $13,024; p=0.0001) were found to be less than that for rTKA vs. mTKA. rTKA also accrued $1,744 fewer costs than mTKA (5,234 vs. $6,978; p=<0.0001) utilized fewer days in inpatient (4 vs. 7; p<0.0001) and SNF care (15 vs. 16; p=0.0642) as well as a 90-day readmission reduction of 33% (p=0.0423).

The results from this study show rTKA to be associated with significantly lower 90-day EOC costs. These lower rTKA patient costs are likely attributable to the significantly lower index costs, increased likelihood of being discharged to home, shorter LOS, and decreased readmission rates, when compared to mTKA patient costs.
Abstract. Background:
The purpose of this study was to evaluate hospital admissions for revision surgeries associated with robotic-arm assisted unicompartmental knee arthroplasty (rUKA) vs. manual UKA (mUKA) procedures.

Patients ≥18 years of age who received either a mUKA or a rUKA procedure were candidates for inclusion and were identified by the presence of appropriate billing codes. Procedures performed between March 1st, 2013 and July 31st, 2015 were used to calculate the rate of surgical revisions occurring within 24-months of the index procedure. Following propensity matching, 246 rUKA and 492 mUKA patients were included. Revision rates and the associated costs were compared between the two cohorts. The Mann-Whitney U test, was used to compare continuous variables, and fisher’s exact tests was used to analyze discrete categorical variables.

At 24-months following the primary UKA procedure, patients who underwent rUKA had fewer revision procedures (0.81% [2/246] vs. 5.28% [26/492]; p=0.002), shorter mean LOS (2.00 vs. 2.33 days; p>0.05), and incurred lower mean costs for the index stay plus revisions ($26,001 vs. $27,915; p>0.05) than mUKA patients. Length of stay at index, and index costs were also lower for rUKA patients (1.77 vs. 2.02 days; p=.0047) and ($25,786 vs. $26,307; p>0.05).

Study results demonstrate that patients who underwent rUKA had fewer revision procedures, shorter LOS, and incurred lower mean costs (although not statistically different) during the index admission and at 24-months post-operative. These results could be important for payers as the prevalence of end-stage knee OA increases alongside the demand for cost-efficient treatments.
Abstract. INTRODUCTION: Unicompartmental knee arthroplasty (UKA) is effective for alleviating symptoms of arthritis in a single knee compartment; however, errors in alignment and instability may predispose to failure. Robotic technology has improved precision, but its impact on functional recovery after UKA remains unknown. The purpose of this study was to compare early functional recovery, pain, and radiographic alignment in UKA performed with either robotic assistance or conventional methods.
METHODS: All consecutive patients undergoing UKA by a single physician from January 2015 to March 2018 were retrospectively reviewed. Lower Extremity Functional Scale (LEFS), KOOS Jr, and VAS (0-10) outcomes scores were collected preoperatively, 1, 6, and 12 weeks postoperatively. Radiographic alignment was assessed at the initial postoperative visit.
RESULTS: There were 161 patients, 65 conventional and 96 robotic. At baseline, there was no difference in average age, BMI, or outcomes scores between the two groups. Average preoperative pain was significantly higher in conventional patients (6.1 vs. 5.4; p=0.04). At 3 weeks post-op, conventional UKA patients still had significantly higher pain levels (3.9 vs. 3.1; p=.02). Both groups showed significant improvement in LEF (p<.0001) scores over time (p<.0001). Significant improvement in KOOS Jr. scores from pre-op (52.3) to 6 and 12-weeks postoperatively (67.6, 69.8; p<0.001). When comparing PCS of the VR/SF-12, the robotic-assisted group had significantly higher improvement compared to the conventional group at 6-weeks (40.6 vs. 35.6; p=0.02).
CONCLUSION: Robotic assisted UKA resulted in fewer radiographic outliers, and more rapid recovery with less early postoperative pain although functional differences tended to equilibrate by 3 months postoperatively.
Abstract. This study investigated surgeons’ perceptions of their experience while adopting a novel CAOS enhanced mechanical instrument system for TKA, including ease of usage, task complexity, and demands of surgical time and physical activity. A group of 9 surgeons from multiple countries with no experience in the investigated system used the CAOS enhanced mechanical instrument system during their surgical practice. After performing each TKA case, the surgeon independently completed a 6-section questionnaire formulated to survey his/her experience with the case. The results demonstrated high level of surgeons’ experiences with the adoption of the CAOS enhanced conventional instrumentation, with particularly satisfying experiences in minimum demand of time in landmark acquisition and disruption of the existing surgical process.
Abstract. This study accessed the alignment outliers of intraoperatively measured bony resection during total knee arthroplasty on 10,144 cases performed using a modern CAOS system. The impacts from geographic regions, surgeon’s adoption of the technology (learning or proficient phases), and historical progression of the CAOS application (software versions) were evaluated. The comprehensive analysis demonstrated that the CAOS system is a robust and accurate solution to assist the surgeons to achieve his/her surgical resection goals across its application history.
Abstract. This study applied an advanced statistical tool (multilevel modeling) to assess the accuracy of bony resection during total knee arthroplasty on 10144 cases performed using a modern CAOS system. An extensive list of factors was included for the modeling, including geographic region, inter-surgeon difference, surgeon’s adoption of the technology (learning or proficient phases), and historical progression of the CAOS application (software versions). The comprehensive analysis demonstrated that the CAOS system is an accurate and precise solution to assist the surgeons to achieve his/her surgical resection goals.
Abstract. This study investigated if CAOS TKA cases in higher risk patients would impact the outcomes of surgery. An average of 14-month postoperative outcomes on 58 TKAs from a prospective multicenter study were analyzed. The patients were grouped into challenging and standard case groups according to the criteria of age, BMI, comorbidities, and alignment deformity. Both groups demonstrated significant postoperative improvement in all outcome measures. Compared to the standard patients, the challenging patients achieved significantly higher improvement after TKA in KSS Knee score, while demonstrating the same level of improvements in all other outcome measures. Similarly, the two groups generally exhibit equivalent postoperative outcomes. The data demonstrated consistent postoperative results by CAOS TKA irrespective of patient conditions.
Abstract. The cup orientation plays a major role in the long-term implant stability following Total Hip Arthroplasty (THA). Because of the patient specific spine-hip kinematics, the safe zone introduced by Lewinnek is more and more controversial. Several solutions have been recently developed to take into account such parameter for THA but are all either invasive, difficult to use or expensive. A non-invasive ultrasound (US) based device has been recently proposed which allows the acquisition of the pelvic tilt in different daily positions. The goal of this study is to analyze the in-vivo intra and inter-observer precision of this device. Measurements were realized by three physicians on three healthy subjects having a low, medium and high Body Mass Index (BMI). Among the three physicians, there were an expert, an intermediate, and a novice user. For each subject, the pelvic tilt was measured ten times by the three physicians in the supine, standing and sitting positions. The inter and intra-observer precisions have been analyzed using the intraclass correlation coefficient (ICC) and according to the BMI, the positions and the user expertise level. The inter-observer precision was therefore excellent whatever the BMI. It was also excellent regarding the supine and the sitting positions and good concerning the standing position. The in-vivo intra-observer precision was excellent for all measurements and whatever the user’s expertise, the BMI and the positions. This study shows therefore that the precision of our system meets the clinical requirement. Introduction
Abstract. The accurate placement of orthopaedic implants according to a biomechanically derived preoperative plan is an important consideration in the long-term success of these interventions. Guidance technologies are widely described however, high cost, complex theatre integration, intraoperative inefficiency and functional limitations have prevented the widespread use. A novel, intraoperative mechatronics platform is presented, capable of the rapid, intraoperative manufacture of low-cost patient-specific guides. The device consists of a tableside robot with sterile drapes and some low cost, sterile disposable components. The robot comprises a 3D optical scanner, a three-axis sterile computer numerical control (CNC) drill and a two-axis receptacle into which the disposable consumables may be inserted. The sterile consumable comprises a region of rapidly setting moldable material and a clip allowing it to be reversibly attached to the tableside robot. In use, patient computed tomography (CT) imaging is obtained at any point prior to surgery and a surgical plan is created on associated software. This plan describes the axis and positioning of one or more guidewires which may, in turn, locate the prosthesis into position. Intraoperatively, osseous anatomy is exposed, and the sterile disposable is used to rapidly create a mould of the joint surface. Once set, the mould is inserted into the robot and an optical scan of the surface is taken followed by automatic surface registration, bringing the optical scan into the same coordinate frame of reference as the CT data and plan. The CNC drill is orientated such that the drill axis and position exactly matches the planned axis and position with respect to the moulded surface. A guide hole is drilled into the mould blank, which is removed from the robot and placed back into the patient with the moulded surface ensuring exact replacement. A wire is subsequently driven through the guide hole into the osseous anatomy in accordance with the preoperative plan. The guide blank may be slid off the wire and discarded allowing the procedure to continue in the normal manner. A Pre-clinical prototype robot was constructed and used to insert guide wires into a 12 cadaveric shoulder arthroplasty specimens according to a ‘pre-operative’ plan. A ‘postoperative’ CT scan was used to assess accuracy with respect to the ‘pre-operative’ plan. Initial average end to end accuracy was 1.2 mm with respect to planned vs achieved glenoid point of entry and 2.2deg version, 1.6deg inclination with respect to planned vs achieved wire angle. These data demonstrate accuracy within the bounds of relevant literature with a significant margin for potential improvement.
Abstract. Currently, pre-operative analysis of soft-tissue balance is limited to measures of passive laxity rather than active laxity. By including active laxity data, a more comprehensive surgical plan can be delivered, however there are no measures for active laxity currently in routine use. Therefore, the validation of a proxy measure based on routine collected imaging is valuable. This study aimed to determine whether coronal knee laxity can be predicted from pre-operative alignment and bony morphology of the knee. Fifty-eight patients with pre-operative CT and stressed x-ray imaging for activity laxity were analysed to identify anatomical landmarks and determine varus-valgus laxity ranges for a range of flexion angles with the joint subjected to lateral forces. Correlations between anatomical and alignment parameters, vs laxity ranges and midpoints were determined using pairwise complete Pearson linear correlation analyses. Of the 17 anatomical/alignment measurements studied, 8 correlated significantly with the knee laxity range’s midpoint at 20 ̊ flexion, with the strongest correlation being with supine coronal alignment (r = 0.95, p < 0.001); the findings were similar at 45-90 ̊. Compared to knee laxity midpoint, knee laxity range was not as strongly correlated with anatomical and alignment parameters, with only 3 anatomical parameters correlated significantly with laxity range at 20 ̊ flexion and none at 45-90 ̊ flexion. These results suggest morphological measurements and anatomical characteristics may help define functional coronal laxity range of the knee.
Abstract. Preoperative planning is an integral part of total joint arthroplasty, aiming to restore the joint mimicking the native functionality (Choplin 2008).Dimensions of bone and prosthetic implants are usually evaluated by preoperative radiographs to restore leg length discrepancy and femoral offset (Amirouche et al 2015).Nevertheless, even when using dedicated software, the femoral component is precisely selected only in 34% of the cases, resulting in a significant variability in 50% of the patients with 10mm in postoperative leg length discrepancy (Strøm e Reikerås 2018) With the aim of reducing postoperative complications, in this work a computer algorithm has been developed that uses preoperative x-rays and performs automatic extraction of anatomical landmarks together with an automatic selection of the component that closely restore the native hip. In a first phase, the Fuzzy logic based algorithm extracts the axis of the femoral neck, the femoral axis of the middle diaphysis,both the trochanters and the center of the femoral head.Then,by checking the geometrical data of commercially available hardware selects the component closer to the native anatomy. In a second phase,by a kinematic approximation the algorithm uses the segmentation of the intramedullary canal to position the implant,assuming a press-fit insertion and thus anticipating potential contact region and, consequently, leg length discrepancy and offset. The algorithm has been tested on a set of x-ray images. The correlation diagram is used to determine the femur length bt means of the diameter of the femoral head. A sample of 16 femoral radiographs in Antero-posterior view was used to validate the algorithm. The head size was used to evaluate the error between the dimension calculated and the one manually measured on the radiograph, resulting in the order of + 2.00 mm.The prediction of the fixation by means of press-fit technique gives an average contact height of 21.49 mm and an angular deviation of 4.13 ° of the neck axis, applying a force of 9.25 kN (Sakai 2011).Compared to existing methods, the proposed algorithm allows to calculate the femoral sizes necessary for dimensioning the implant from 2D radiographs in the frontal view only and to predict the prosthesis-bone contact in terms of height and interference reached after hammering.It has to be noted that the study, based on coronal x-rays, does not actually account for pelvic tilt (Bono 2018), that will be include in a further research.
Abstract. Polyethylene particles produced in metal backed tibias (MBT) are understood to contribute to bone loss and component loosening. This, and better surgical techniques (including computer navigation) and increasing costs have renewed interest in all poly tibias (APT). We investigated peri-APT bone mineral density (BMD) in patients; expecting to find no differences between two post-operative values.
Patients over 65 years, with BMI ≤ 37.5 and no previous joint replacements were recruited to have TKA using the Columbus APT with computer navigation (OrthoPilot). The study cohort (n=26) had a mean age of 71.9 (sd 4.35), a BMI of 31.2 (sd 3.8). The BMD examinations were performed six weeks and 18 months post-operatively. Six regions-of-interest (ROI) were identified on anterior/posterior and lateral scans. For each ROI at each time point, relative BMD differences (RDs) were determined between limbs and RDs at the two time points were compared.
No differences were found between the two RDs for any ROI. No revisions or complications were reported. At 18 months post-operatively, 78.3% of the cohort were “very satisfied” with the outcome of their surgery and Oxford Knee Scores improved significantly compared to pre-operatively (p<0.005). Mean knee range of motion was 102° (sd 10.7◦) and mean leg alignment was 2.0° valgus (1°varus-6°valgus).
Results from BMD suggest that implants were well fixated. Patients reported excellent satisfaction and function. We believe that using APTs and computer navigation is a viable and cheaper option to MBT for patients who are less active, have lower BMI and good bone quality.
Abstract. Templating is an important and established step in the preoperative planning process of total hip arthroplasty (THA) in order to select the size and position of the implant. In severely arthritic cases, the unaffected contralateral side is sometimes used as a reference to reconstruct morphological parameters of the planned implantation (ipsilateral) side, for example the femoral offset, the leg length or the antetorsion. Recent studies have shown that a significant side-to-side asymmetry of important proximal femoral parameters already exists in healthy subjects questioning the validity of the contralateral side as a reference. However, if preoperative asymmetry is larger than asymmetry in healthy subjects, preoperative planning can still make use of the contralateral side to target a postoperative result within the range of physiological asymmetry. Therefore, the specific objective of this study was to quantify the preoperative side-to-side asymmetry of five important morphological parameters of the proximal femur. Significant side-to- side differences between the ipsilateral side and the contralateral side were detected for the antetorsion, the offset, the neck length and the femoral length. The antetorsion is significantly higher for the ipsilateral side whereas offset, neck length and femoral length are significantly smaller. Mean and maximum difference in antetorsion is almost twice as high for the THA patients in comparison to healthy subjects. The same trend can be observed for the femoral length, less pronounced also for the caput-collum-diaphyseal angle. The comparison of proximal femoral side-to-side differences for subjects before THA and healthy subjects leads to the conclusion that contralateral templating can be a reasonable basis for THA planning of severely arthritic hips if the contralateral side shows no signs of osteoarthritis or developmental dysplasia.
Abstract. Objectives: In total hip arthroplasty (THA), accurate acetabular component position promotes prosthetic hip joint stability and longevity, and minimizes polyethylene wear. Image-based mechanical navigation is known to improve accuracy and reproducibility of accurate cup position intraoperatively via the posterior approach and the superior capsular approach. The purpose of this study was to assess the accuracy of acetabular component position using image-based mechanical navigation via the direct anterior approach (DAA). Methods: We prospectively followed 96 patients who underwent THA with one fellowship-trained arthroplasty surgeon over a nine-month period. Thirty-three patients underwent DAA THA with the anterior HipXpert device (Group 1), and 63 patients underwent posterior approach THA with the lateral HipXpert mechanical navigation device, serving as an operative control group (Group 2). Standard postoperative plain film radiographic measurements of acetabular component inclination and anteversion were assessed. Results: The average inclination angle was 38.6 degrees and 40.6 degrees in Groups 1 and 2, respectively. The average anteversion angle was 27.6 degrees and 30.1 degrees in Groups 1 and 2, respectively. There were no postoperative hip dislocations and no study patients underwent revision THA at an average follow-up of 12 months. There were no patient outliers in Groups I or II with inclination angles or anteversion angles outside 10 degrees of the preoperatively planned values. Conclusion: The anterior HipXpert mechanical navigation device enhances accurate acetabular component position and may reduce outlier component placement. Acetabular socket position is as accurate using the anterior device as it is using the lateral device.
Abstract. Introduction:
Robotic-arm assisted surgery allows for the execution of well-aligned knee arthroplasty regardless of pre-existing deformity. This case series is presented to show the utility of robotic-arm assisted TKA in achieving well-balanced, well-aligned results in a variety of challenging scenarios.

We present seven challenging cases of robotic-arm assisted total knee arthroplasty. There were two conversion TKAs following a previous surgery. One case featured a previous tibial plateau fracture treated with a plate and screws construct while another featured a prior femoral nail with significant bony overgrowth. Five cases of severe deformity were also identified, with one tibial nonunion, two valgus knees and one patient with two varus knees due psoriatic arthritis treated with staged bilateral TKAs. Patient clinical history, physical examinations, intraoperative surgical techniques and postoperative courses were recorded.

All cases were able to utilize effective preoperative planning to obtain precise intraoperative bone cuts and component positioning. Each of the seven cases achieved well-balanced, well-aligned arthroplasties. There were no intraoperative or postoperative complications. At latest follow up, all patients showed significant improvements in pain and ambulation compared to preoperative exams.

Robotic-arm assisted surgery allows for the integration of preoperative CT scans to establish and execute a surgical plan with precision. Despite the complexity of these cases, excellent results were achieved without the need for revision-type components. These cases display the ability of robotic-arm assisted surgery to achieve consistent well-aligned results with minimal bone loss in challenging total knee arthroplasty cases.
Abstract. Purpose
Innovative technologies such as robotic assistance and intraoperative load sensors for total knee arthroplasty (TKA) aim to reduce outliers, as well as to address patient dissatisfaction. There is currently no information available that assesses the findings of using these technologies together during TKA.
Intraoperative data on alignment, gap spacing, and quantitative balance was prospectively collected in a cohort of 79 consecutive TKAs performed with robotic assistance. An instrumented trial component was utilized that captured medial and lateral tibio-femoral loads, allowing the quantitative assessment balance.
Of the 79 knees, 58 (73%) had varus alignment and 21 (37%) had valgus. We divided these groups into correctable and fixed deformities. Correctable varus knees: At trial reduction 30% of the knees demonstrated quantitative imbalance at trial reduction. Fixed varus knees. At trial reduction 55% (of knees were deemed imbalanced. Correctable valgus knees: At trial reduction, 35% were imbalanced. Fixed valgus knees: Half of the knees (n=2) were imbalanced at trial reduction. The imbalance in all groups was addressed with combinations of bone and soft tissue adjustments so that at final implantation 99% of cases (n=78) were quantitatively balanced
While the robot was both precise and accurate with its cuts to create appropriate gap spaces, only 57% were quantitatively balanced. Ultimately, almost all knees were balanced with final implants, but that state required the use of additional techniques, including soft tissue and bony modifications. More data is needed to determine if these technologies will equate to increased clinical success.
Abstract. Accurate reproduction of glenohumeral anatomy during anatomic total shoulder arthroplasty (aTSA) has been shown to correlate with positive clinical outcomes. Preoperative planning and computer assisted surgery (CAS) can improve upon glenoid placement, but such systems for aTSA have experienced limited commercial success. Postoperative surgical reports from the first 574 clinical cases of a commercially available CAS aTSA system were collected and analyzed for implant selection, implant placement, and incision start to incision close operative time, and compared to similar date cohorts for non-navigated cases. Navigated aTSA cases had a significantly longer incision time than non-navigated cases. Augmented glenoid components were used in a much higher percentage of navigated cases than non-navigated cases, suggesting that augmented glenoid components provide utility for correcting pathologic glenoid wear. The average resultant version of the implanted component increased with the size of augment used, suggesting there may not be a clear consensus on optimal retroversion. term clinical follow up will need to be collected to determine if preoperative planning combined with more precise and accurate glenoid component positioning leads to improved clinical outcomes and implant longevity.
Abstract. Placement of the glenoid component in reverse total shoulder arthroplasty (rTSA) is of paramount importance and can affect a patient’s range of motion postoperatively. Preoperative planning and computer assisted surgery (CAS) can improve upon glenoid placement, but such systems for rTSA have experienced limited commercial success. Postoperative surgical reports from the first 1702 clinical cases of a commercially available CAS rTSA system were collected and analyzed for implant selection, implant placement, and incision start to incision close operative time, and compared to similar date cohorts for non-navigated cases. Navigated rTSA cases had a significantly longer incision time than non-navigated cases. Augmented glenoid components were used in a much higher percentage of navigated cases than non-navigated cases, suggesting that augmented glenoid components provide utility for correcting pathologic glenoid wear. The average resultant version and inclination of the implanted component increased with the size of augment used, suggesting there may not be a clear consensus on optimal version or inclination. Long term clinical follow up will need to be collected to determine if preoperative planning combined with more precise and accurate glenoid component positioning leads to improved clinical outcomes and implant longevity.
Abstract. SterEOS is a software developed by EOS Imaging® allowing the measurement of 3D orthopaedic parameters on two bi-planar radiographs. The goal of this preliminary study was to assess the reliability of the pelvic measurements. Two observers, a novice and an intermediate user, measured three times these parameters on pre and postoperative EOS images coming from ten patients. Intra- and inter-observer precision have been evaluated with intra-class coefficient (ICC) and Bland-Altman graphs. On preoperative EOS images, a high intra- and inter-observer precision (ICC>0.8) was obtained for the measurement of the femoral head diameter, the femur length, the pelvic version and the pelvic obliquity. The offset, the femoral neck length, the pelvic incidence and the sacral slope measurement had a high intra-observer precision but a lower inter-observer precision. The measurement of the acetabulum inclination and anteversion, the CCD angle, the femur torsion, the pelvic rotation and the anterior pelvic plane inclination had a low intra- and inter-observer precision. Similar results were found on postoperative EOS images. Our results are partially consistent with the literature since authors found high intra- and inter-observer precision for all pelvic parameters. Further studies are therefore needed to evaluate the impact of the observer experience on the reliability of those measurements.
Abstract. The outcome of total hip arthroplasty (THA) depends on multiple alignment and design parameters. Unsuitable parameter settings could lead to impingement, dislocation, increased wear, and loosening. This work introduces a method for calculating a patient-specific target zone based on range of motion (ROM) related and load related criteria. Possible bone or prosthesis impingement are analyzed. The resulting hip force is calculated and compared to the pre-operative situation. The edge loading risk is analyzed. Pelvic tilt is considered for the calculation of the ROM and the load. THA parameters fulfilling all criteria are included in the target zone.
The above described method has been applied to 30 cases retrospectively. All cases had been planned and navigated on the basis of CT data. From each patient, pre- and post-operative CT and EOS data and Harris Scores were acquired. The pre-operative data served as the input data for the target zone calculator. We hypothesized that cases with post-operative THA parameters inside the target zones have higher scores than other cases.
The patients whose implants are within the target zones had higher scores than the remaining patients. Especially patients inside both target zones (combined target zone) had higher scores. The results also show that for 19 out of 30 patients, conventional CT-based planning and navigation does not provide optimal placement regarding the combined target zone. A further validation of the method with a larger sample size is part of our ongoing work.
Abstract. To date, there are no studies aimed at characterizing the active cutting time for a robotic-assisted PKA procedure and the impact of workflow. This study quantified the active cutting time for three medial PKA workflows using the same robotic-assisted system.
Three surgeons each prepared six cadaveric knees for PKA with robotic-assisted technology using one of three workflows: A) burr-only, using a legacy cutting system and burr design; B) burr-only, using a new cutting system and burr design; or C) planar, using a new cutting system, burr design and saw. For a burr-only workflow, the femur and tibia were prepared with a burr. For a planar workflow, the femur and tibia were prepared with a burr and saw. The total mean trigger time to complete all femoral or tibial bony resections was measured and statistically compared between workflows using ANOVA and Tukey Pairwise Comparison.
There was statistically significant less time required to prepare the femur and tibia in B and C, compared to A (p≤0.05). Less time was required in C than B, but this was not statistically significant (p>0.05). Workflow A took an average of 429±104 seconds (range, 314 to 529 seconds), B took an average of 302±40 seconds (range, 244 to 363 seconds), and C took an average of 236±50 seconds (range, 196 to 332 seconds).
The new burr design, when used with both burr-only and planar workflows, has the potential to be more efficient (30 and 45% faster, respectively) compared to the legacy burr using the burr-only workflow, for a medial PKA. Bone resection time should be investigated in a clinical setting.
Abstract. While manual total knee arthroplasty (MTKA) has demonstrated excellent clinical results, occasionally intraoperative damage to soft tissues can occur. Robotic-arm assisted technology is designed to constrain a sawblade in a haptic zone to help ensure that only the desired bone cuts are made. The objective of this cadaver study was to quantify the extent of soft tissue damage sustained during TKA through a robotic-arm assisted (RATKA) haptically guided approach and conventional MTKA approach. Four surgeons each prepared 3 RATKA and 3 MTKA specimens for cruciate retaining TKAs. RATKA was performed on one knee, with MTKA on the other. Postoperatively, 2 additional blinded surgeons, assessed and graded damage to 14 key anatomic structures. A Kruskal-Wallis hypothesis test was performed to assess for statistical differences of soft tissue damages between RATKA and MTKA cases. A p-value <0.05 was used as the threshold for statistical significance, and p-values were adjusted for ties. Significantly less damage occurred to the PCL in the RATKA than the MTKA specimens (p<0.0001). RATKA specimens had less damage to the dMCL (p=.149), ITB (p=0.580), popliteus (p=0.248), and patellar ligament (p=0.317). The results of this study indicate that RATKA may result in less soft-tissue damage than MTKA, especially to the PCL.
Abstract. In many orthopedic surgeries, the surgeon relies on a C-arm fluoroscopy machine with the images usually displayed on a bedside monitor. The mental effort that surgeons expend transferring information from the imaging display back to the surgical site can lead to distraction causing errors that could directly influence quality of surgery. Depth Camera Augmented Fluoroscopy (DeCAF) uses an Intel RealSense depth camera to provide real-time visualization of the surgical site by overlaying x-ray images from the C-arm onto live video of the patient’s surface anatomy. Using geometric data acquired via the depth camera, the device facilitates transforming a real-time video feed aligned with the camera coordinate system to a perspective aligned with the x-ray source. The x- ray overlay is attained while restricting incursion on the surgeon’s work area and allowing the C-arm to be used in its normal position to minimize radiation exposure. DeCAF successfully facilitates an x-ray video overlay feature while eliminating key limitations such as size, radiation exposure and acquisition time associated with other similar devices. Future work will involve evaluating overlay accuracy, the addition of second depth camera to aid in filling in areas with missing details, and a design iteration involving bagging of the camera with a sterile cover to ensure compliance with asepsis requirements prior to evaluating the system in the operating room.
Abstract. Several orthopedic applications require a three-dimensional model of the bone. Ultrasound is a radiation-free and cheap alternative to the state-of-the-art imaging modalities if its limitations in terms of image quality and viewing range can be overcome. This work presents in-vitro as well as in-vivo experiments evaluating the IPASM search, a method for combined segmentation, registration as well as extrapolation. The algorithm is capable to reconstruct the distal surface of a phantom femur with an average surface distance error of roughly 1mm in case of in-vitro as well as below 2mm for in-vivo records, even if the shape varies strongly from the initial model.
Abstract. We demonstrated a miniature handheld robot in assisting the surgeon to create a tunnel during pedicle screw fixation. The robot is aimed at stabilizing the drill during penetrating the surface of a vertebra and reducing the drill drifting from the entry point caused by involuntary tremor. The handheld robot is consisted of a hexapod platform. The master control was designed to cooperate with the 6-DOF parallel slave robot. The human machine interface has been investigated for the drill to target the planned trajectory with the operator’s handle motion.
Abstract. The integration of augmented-reality (AR) in medical robotics has been shown to reduce cognitive burden and improve information management in the typically cluttered environment of computer-assisted surgery. A key benefit of such systems is the ability to generate a composite view of medical-informatics and the real environment, streamlining the pathway for delivering patient-specific data. Consequently, AR was integrated within an orthopaedic setting by designing a system that captured and replicated the user- interface of a commercially available surgical robot onto a commercial head mounted see through display. Thus, a clinician could simultaneously view the operating-site and real- time informatics when carrying out an assisted patellofemoral-arthroplasty (PFA). The system was tested with 10 surgeons to examine its usability and impact on procedure- completion times when conducting simulated PFA on sawbone models. A statistically insignificant mean increase in procedure completion-time (+23.7s, p=0.240) was found, and the results of a post-operative qualitative-evaluation indicated a strongly positive consensus on the system, with a large majority of subjects agreeing the system provided value to the procedure without incurring noticeable physical discomfort. Overall, this study provides an encouraging insight into the high levels of engagement AR has with a clinical audience as well as its ability to enhance future generations of medical robotics.
Abstract. Total knee replacements (TKR) are often deemed successful when patients recover and maintain their functionality both in the short and long term. The other main indicator for success is the revision rate following TKR. This study analyses the long term results of navigated TKR based on patient related outcomes in terms of patient satisfaction, Oxford Knee Score (OKS) and also knee revision rates.
The retrospective data of all patients who underwent navigated Columbus TKR from the author’s institution from 2005 to 2011 was analysed and compared to the national database. The overall cohort size was 1679 with a mean age of 68.81yrs (sd 8.46). The OKS, satisfaction scores, complication and revision rates were compiled and evaluated up to ten years post-operatively. Patient reported outcomes were recorded six weeks, one, two, five and ten years post-operatively.
The results from the OKS and satisfaction scores demonstrated marked improvement throughout recovery to the ten year time point. The OKS had a mean improvement of 16.6 from the pre-operative score at the 10 year time point and the satisfaction scores improved at each follow-up and remained high at the 10 year time point. A total of 61 complications and 36 revisions recorded, with infection being the major cause for revisions.
This survey has identified and established that the majority of patients undergoing knee arthoplasty using the Columbus total knee system and computer navigation function reasonably well in the long term and the revision and complication rates in this hospital are compare well with national levels..
Abstract. The survival rate of navigation-assisted total knee arthroplasty when mechanical revision was considered as the end-point was 98% after 10 years and 96% after 15 years. These figures compare favorably with previously published literature about conventional implantation. Longer follow-up is required to prove superiority of any technique.
Abstract. The survival rate of navigation-assisted mobile bearing total knee arthroplasty after 13 years when mechanical revision was considered as the end-point was significantly improved when compared to conventionally implanted mobile bearing total knee arthroplasty. Longer follow-up is required to prove superiority of any technique.
Abstract. The survival rate of navigation-assisted total knee arthroplasty was superior to conventionally implanted after 12 years for knees with initial severe coronal deformation when mechanical revision was considered as the end-point. Longer follow-up is required to prove superiority of any technique.
Abstract. In a prospective, non-randomized trial, 222 hips across seven centers received the same THA system of a tapered wedge stem and novel additively manufactured titanium porous clusterhole acetabular shell in primary THA. 113 hips were implanted with a robotic-assisted surgical system while 109 hips were implanted manually. The robotic-assisted cohort yielded a similar mean skin-to-skin surgical time of 80.35 minutes compared to 79.35 minutes for the manual cohort (p=0.8895), along with a shorter hospital stay of 0.96 days compared to 1.59 days (p<0.0001). The robotic-assisted cohort resulted in a lower blood loss of 199.8 cc compared to 310.1 cc for the manual cohort (p<0.0001). Standard deviation for incision length was 81% of the value in robotic-assisted cases when comparing with manual cases (2.2 cm vs. 2.7cm). Robotic-assisted THA cases demonstrated improved clinical outcomes with a higher 6-week postoperative HHS (81.0 vs. 78.4), physical VR-12 (39.5 vs. 35.9), and LEAS (9.2 vs. 8.0). The EQ-5D treatment effect size at 6-weeks postoperative for robotic-assisted cases exceeded a large effect with a value of 0.91, while the effect size for manual cases was 0.59. Robotic-assisted 3-D patient specific planning and haptically guided robotic-assisted surgical execution demonstrated an improved operative experience relative to blood loss, and incision length. The robotic cohort also yielded improved early clinical and functional outcomes when comparted to manual techniques at six weeks. These early, enhanced robotic-assisted THA results support surgeons using robotics with the goals of decreased patient pain, greater range of motion, and increased joint stability.
Abstract. Achieving proper soft tissue balance during total knee arthroplasty (TKA) can reduce post- operative instability and stiffness as well as improve patient reported outcomes. The objective of this study was to compare final intra-operative coronal balance throughout the knee range of motion in navigated robotic-assisted TKA when performed with quantifiable feedback from a robotic ligament tensioning tool versus with standard trials and navigation measurements alone.
The study included a prospective cohort of 52 patients undergoing robotic-assisted TKA using a measured resection technique. The cohort was divided into two sequential groups: a non-sensor-assisted group (n=25) and a subsequent sensor-assisted group (n=27). Once bony cuts and soft tissue balancing was performed in the non-sensor cohort, the final tibiofemoral gaps were measured throughout the knee range of motion using a robotic-assisted tensioner with the surgeon blinded to the measurements. For the sensor cohort, the surgeon preformed soft-tissue releases or re-cuts in order to balance the knee using the gap measurement data from the robotic tensioner. The robotic-assisted tensioner was then used to measure the final medial and lateral gap measurements.
The average mediolateral gap difference throughout the range of flexion was 1.9 ± 0.7 mm with maximum difference of 7.8 mm for the non-sensor cohort. The sensor cohort had an average mediolateral difference of 1.5 ± 0.6 mm and a maximum difference of 3.8 mm. The difference between the two groups was statistically significant from 60 to 90 degrees of flexion. 38-41% of knees were balanced to within 1 mm mediolaterally in the non-sensor group compared to 48-70% for the sensor group when measured at various flexion angles. 65-76% of knees were balanced to within 2 mm for the non-sensor group compared to 78-86% for the sensor-assisted group. The number of knees requiring subsequent soft tissue releases was similar in each group. Soft tissue balancing with the aid of a robotic tensioning tool resulted in significantly more accurate soft tissue balance than when using navigation measurements and standard trials alone in this single surgeon study.
The outcome of knee replacement depended on alignment, balancing of soft tissue, symmetrical and
rectangular gaps adjustment, and accurate implant placement. Many techniques have been used to
improve these factors including navigator assisted knee replacement, which has precise bone cut
and accurate soft tissue balancing. However, cementation may change gaps and alignment that can
affect outcome of knee replacement.

To compare gaps and alignment after cementation in computer assisted total knee replacement

Prospective collecting data all cases performed computer assisted total knee replacement with
cruciate retaining - mobile bearing implant design. Gaps and mechanical axis was collected and
compered between complete trial prosthesis and final cementation.

Lateral extension gap and flexion contracture significantly increase after cementation when
compared with trial implantation [0.6 mm (P = 0.021), 2.7o (P = 0.00)]. The mechanical axis was not
deviated after cementation (P = 1.00).

Cementation is able to influence gap and alignment. It may be useful to control and recheck gap and
alignment with navigation system during cementation. Clinical correlation needs further
Abstract. The importance of accurate cup positioning during total hip arthroplasty (THA) to minimise post- operative complications has been well defined. However it remains unclear if following navigated THA there is a relationship between the active range of movement, the inclination and anteversion of the implant, and the theoretical range of movement as measured intra-operatively using imageless navigation. Fifteen male patients undergoing primary THA using the Orthopilot (Aesculap AG, Tuttlingen, Germany) imageless navigation system were recruited. The Orthopilot system flexion value was recorded. Three months post-THA patients underwent 3D biomechanical analysis (Vicon Motion Systems, Oxford, UK) during which patients performed a standing active hip flexion movement and a sitting task. Inclination and anteversion calculated according to Pradhan’s formula were taken from post-operative radiographs. There was no observed correlation with the theoretical hip flexion and the standing peak active or sitting peak hip flexion values in this series. However, Orthopilot flexion considers only the interaction of the implant components and not the soft tissues surrounding the hip joint which may limit clinical flexion. There does not appear to be any relationship between the inclination and anteversion angles and the range of movement observed post- operatively during a standing active hip flexion task and sitting task. It was observed that peak active hip flexion between the operated and non-operated limbs was not significantly different at three months, which indicates a good level of symmetry at this time point.
Abstract. Brown-Sequard syndrome (BSS) is most commonly seen in patients with spinal trauma and extramedullary spinal neoplasm. Pure BSS caused by cervical disc herniation is extremely rare. Operative treatment is generally recommended those patients with BSS to improve neurological function. Here, we report a rare case of spontaneous healing of BSS caused by cervical disc herniation. Two years follow-up showed complete disappearance of symptoms without recurrence. To our knowledge, no similar cases have been reported before. Therefore, for appropriate patients, conservative treatment can be considered for a few months before deciding on surgical treatment.
Abstract. PURPOSE: Indications for total hip arthroplasty (THA) are expanding to include increasingly younger patients, yet limited outcomes research has focused on this population. This study compares outcomes between the anterior and posterior approach, as well as between conventional and technology-assisted THA in patients under 35-years of age.

METHODS: Retrospective analysis of 139 primary THAs in 125 patients younger than 35-years old was conducted. Patients were divided into two cohorts: (1) anterior-THA and (2) posterior-THA. A posterior-THA sub-group analysis was performed to compare: (1) technology-assisted THA (tech-THA) versus (2) conventional-THA (con-THA). Demographics, perioperative data, radiographic and clinical outcomes were analyzed using Chi squared and unpaired student t-tests for categorical and continuous variables, respectively.

RESULTS: Of the 139 cases performed, 40 were anterior-THA and 99 were posterior-THA. The anterior-THA cohort had shorter mean surgical time (95.0±25.7 vs. 118.3±43.3 minutes; p<0.01), shorter hospital admissions (1.9±1.4 vs. 2.7±1.2 days; p<0.01), and lower estimated blood loss (343.4±164.1 vs. 438.0±272.8 mL; p<0.01) compared to the posterior-THA cohort. There were no significant differences in component positioning, limb length discrepancy, clinical outcomes or postoperative complications between cohorts. In the sub-group analysis, cup placement within Lewinnek’s Safe Zone was achieved in 78% of tech-THA versus 49% of con-THA (p<0.01). Need for revision THA was significantly higher among the con-THA group (9.4% vs. 0%; p<0.01).

CONCLUSION: There is no significant difference in outcomes between anterior- and posterior-THA among patients under 35-years of age, however, the anterior approach may promote earlier hospital discharge. Technological-assistance can improve component positioning and may reduce the rate of revision for posterior-THA in patients under 35-years old.
Abstract. Introduction:
Robotic-arm assisted (RAA) total knee arthroplasty (TKA) has been shown to potentially have certain pre- and intra-operative advantages over manual techniques. Although there are many studies on the alignment advantages when using the robotic-arm assisted (RAA) system for total knee arthroplasty (TKA), there have been questions regarding patient-reported outcomes. Therefore, the purpose of this study was to use this index to compare: 1) total; 2) physical function; and 3) pain scores for manual vs. RAA patients.

We compared 53 consecutive robotic-arm assisted to 53 consecutive manual TKAs. No differences in pre-operative scores were found between the cohorts. Patients were administered a modified WOMAC satisfaction survey pre-operatively, and at 1-year post-operatively. Univariate analyses and multivariate models with stepwise backward linear regression were utilized to evaluate the associations between outcome scores and surgical technique, age, sex, as well as body mass index (BMI).

The RAA cohort had significantly improved mean total (6±6 vs. 9±8 points, p=0.03) and physical function scores (4±4 vs. 6±5 points, p=0.02) when compared to the manual cohort. The mean pain score for the RAA cohort [2±3 points (range, 0 to 14 points)], was also lower than that for the manual cohort [3±4 points (range, 0 to 11 points) (p=0.06)].
On backward linear regression analyses, RAA was found to be significantly associated with more improved total (beta coefficient [β]-0.208, SE [standard error] 1.401, p<0.05), function (β=0.216, SE=0.829, p<0.05), and pain scores (β-0.181, SE=0.623, p=0.063). The RAA technique was found to have the strongest association with improved scores.

With newer surgical technologies constantly being introduced, it is imperative to continue to evaluate these new modalities, particularly in their abilities to improve patient satisfaction outcomes. This study suggests that RAA patients may have short term improvements at minimum 1-year post-operative. However, longer-term follow up with greater sample sizes are needed to further validate these findings.
Abstract. This is a prospective data collection across seven centers in a non-randomized, post- market study where an additive manufactured cementless acetabular shell was used in primary total hip arthroplasty. There was a total of 254 hips/246 patients across seven centers. Clinical outcomes including all-cause survivorship, the Harris Hip Score (HHS), Lower Extremity Activity Scale (LEAS), Veterans Rand 12 (VR-12), EuroQol 5D (EQ- 5D) and radiographs were collected pre- and postoperatively. Radiographs were analyzed for presence of radiolucencies, migration and overall cup stability. All-cause survival rate was 99.61% and there were no reported radiolucencies greater than 2mm for any zone. There was a reduction in radiolucencies from the 6-week to 1-year postoperative timeframe. All cups reviewed at 1-year were stable with no radiolucencies in 96% of hips. These early results demonstrate the favorable properties of this shell and the use of additive manufacturing in orthopaedic surgery.
Abstract. Proper positioning of the acetabular cup deters dislocation after total hip arthroplasty (THA). The concept of a safe zone (SZ) for acetabular component placement was first characterized by Lewinnek et al. and furthered by Callanan et al. The SZ concept remains widely utilized and accepted in contemporary THA practice; however, components positioned in this SZ still dislocate. This study sought to characterize current mass trends in cup position identified across a large study sample of THA procedures completed by multiple surgeons. This retrospective, observational study reviewed acetabular cup position in 1,236 patients who underwent THA using computer-assisted navigation between July 2015 and November 2017. The overall mean cup position of all recorded cases was 21.8° (±7.7°, 95% CI = 6.7°, 36.9°) of anteversion and 40.9° (±6.5°, 95% CI = 28.1°, 53.7°) of inclination. For both anteversion and inclination, 65.5% (809/1236) of acetabular cup components were within the Lewinnek SZ and 58.4% (722/1236) were within the Callanan SZ. Acetabular cups were placed a mean of 6.8° of anteversion (posterior/lateral approach: 7.0°, anterior approach: 5.6°) higher than the Lewinnek and Callanan SZs whereas inclination was positioned 0.9° higher than the reported Lewinnek SZ and 3.4° higher than the Callanan SZ. Our data shows that while the majority of acetabular cups were placed within the traditional SZs, the mean anteversion orientation is considerably higher than those suggested by the Lewinnek and Callanan SZs. The implications of this observation warrant further investigation.
Abstract. Background: Acetabular cup positioning is vital to the long-term survivorship of total hip arthroplasty (THA). Malalignment has been linked to dislocation, wear and osteolysis. Although there are many studies demonstrating the reduction in variability of cup positioning with computer-assisted techniques, there are relatively few reporting long-term patient reported outcomes and revision rates. Aim: The aim of this study was to review whether those patients who underwent navigated THA had better long-term survivorship or better patient reported outcomes. Methods: We compared revision rates and Oxford hip scores of 152 THAs (47 navigated and 105 non-navigated) performed at a single site between 2003 and 2008, with a minimum follow-up of 10 years. Results: 9 of the non-navigated and none of the navigated hips were revised at 10 year follow-up (p=0.057). There were no observable differences in 10-year Oxford hip scores between the navigated and non-navigated hips, 44.82 and 43.38 respectively. Conclusion: With respect to the rate of revision, although statistical significance was not achieved, it can be shown from our data that there was a clinically significant reduction in revision rates with navigated vs. non-navigated techniques. More data with higher patient numbers in the navigated cohort may be required to validate the results of our study.
Abstract. Computer-assisted navigation has the potential to improve the accuracy of cup positioning during total hip arthroplasty (THA) and prevent leg length discrepancy (LLD). The purpose of this study was to compare acetabular cup position and post- operative LLD after primary THA using posterolateral approach. Between August 2016 to December 2017, 57 THAs using imageless navigation were matched with 57 THA without navigation, based on age, gender and BMI. Post-operative weight-bearing radiographs were assessed using for anteversion, inclination and LLD. Goal for functional cup placement was 40° inclination and 20° anteversion based on preoperative weight bearing pelvic images. Functional LLD was measured as compared to pre- operative radiographs and contralateral side. Proportion of cups within Lewinnek’s safe zone, proximity to a pre-operative target of and the LLD >5 mm was assessed. The mean age was 54.9 ± 9.6 years (30 – 72) and 57.6 ± 12.5 years (20 – 85) in control and navigated groups, respectively. Mean cup orientation in the navigated group was 20.6°± 3.3° (17 - 25) of anteversion and 41.9°± 4.8° (30 - 51) of inclination, vs. 25.0°± 11.1° (10 - 31) and 45.7°± 8.7° (29 – 55) in control group, where were statistically significant (p=0.005 and p=0.0001), respectively. In the navigated group, significantly more acetabular cups were placed within Lewinnek’s safe zone (anteversion: 78% vs. 47%, p=0.005; inclination: 92% vs. 67%, p=0.002). There was no significant difference in mean LLD in navigation and control groups (3.1 ± 1.5 mm vs. 4.6 ± 3.4 mm, p=0.36), although fewer LLDs >5 mm were reported in the navigated group (7.1%) than in controls (31.4%, p=0.007). The use of this image-less computer-assisted navigation improved the accuracy with which acetabular cup components were placed and may represent an important method for limiting post-operative complications related to cup malpositioning and LLD.
Abstract. This study reports on mid-term survivorship and outcomes of medial bicompartmental robotic assisted primary knee arthroplasty.
Forty-six knees in 43 patients with a mean 6 year follow up were consented to participate in this retrospective data collection. All patients received primary treatment for knee osteoarthritis with fixed metal backed medial femoral and patellar implants. Demographic data along with post-operative outcomes were collected including; the KSS patient portion, implant survivorship, and patient satisfaction.
All patients were included in the survivorship analysis. 45 knees in 42 patients were available for analysis of KSS and patient satisfaction. The mean follow-up was 6.1 years (range 2.1 - 7.6 years). Sixty-three percent of patients were male and 37% female. Average age at the time of surgery was 67 years and average BMI was 29. There were 3 revisions and 1 arthroscopic surgery resulting in 97.8% all cause survivorship. 86.7% of patients reported walking more than 10 blocks and 95.6% of patients reported walking without the use of assistive devices for support. All patients were able to go up and down stairs, 48.9% required use of a rail. 82.2% of patients reported being satisfied with their knee at 5 years.
In this study we found 97.8% survivorship at a mean 6 year follow up with 82.2% of patients being very satisfied or satisfied with the implant. Longitudinal follow up at 7 and 10 years will continue to evaluate long term outcomes on the variations of robotic assisted knee arthroplasty.
Abstract. The purpose of the study is to investigate minimum ten years clinical results of primary and revision THA using CT-based navigation. Forty-nine primary THAs and 2 revision THAs were performed on 42 patients and followed for at least 10 years. The mean age at surgery was 58 years and the mean follow up was 130 months. During surgery, navigation was used for acetabular reaming and cup implantation in all cases. We evaluated Japanese Orthopaedic Association (JOA) clinical outcome scores, revision surgery and complications. In one primary THA case, navigation procedure was aborted because of registration failure. This case experienced femoral periprosthetic fracture at 4.5 years and dislocation at 8.5 years postoperatively. In another primary THA case, revision THA was performed because of aseptic loosening of cup at 4.5 years postoperatively. Except these two cases, there were no complications such as fracture, dislocation, infection, nerve palsy, deep vein thrombosis or loosening. Preoperatively, mean JOA clinical score was 44 points. Ten years postoperatively, it was improved to 96 points. When the aborted case is eliminated, there were no dislocations at ten years. The survivorship rate at ten years was 98% when revision surgery for any reason was considered as the end point. In conclusion, ten years clinical results of THA using CT-based navigation system were acceptable.
Abstract. Patient Specific Instruments (PSIs) have been introduced into the surgical workflow as a modern way to assist the surgeon in performing femur and tibia resection in Total Knee Arthroplasty (TKA). These PSIs are based on an accurate reconstruction of the surface of the knee’s bones.
In this work, we propose two 3D-3D image-based registration methods to reconstruct an extended field-of-view of the knee joint using only a motorized ultrasound transducer. Those methods are: (1) a dense voxel-based registration method, which needs to preprocess the ultrasound images and form an ultrasound volume. Then, computing the Mutual Information (MI) for each relative displacement to align every pair of volumes, (2) a sparse point-based registration method, which takes into account the point set located on the surface of the bone in ultrasound images. This method detects bony features using ORB detector and matches the corresponding points to find the best transformation using Coherent Point Drift (CPD).
The preliminary qualitative results performed in vitro show that from a set of consecutive ultrasound volumes, an extended field-of-view can be reconstructed using only ultrasound images without any external trackers. Results of the voxel-based approach show that MI is more robust against noise comparing to other similarity measures. On the other hand, results of point-based approach show that is much faster in computation with a low false-positive rate compared to other feature-detectors like SIFT and SURF. Furthermore, experiments show that CPD is less affected by noisy data compared to the classical ICP, which is promising to continue evaluating our work in vivo.
Abstract. Purpose: In younger patients during total hip arthroplasty, the presence of morphologic deformities, previous surgeries, and retained hardware, can pose technical challenges making reconstruction difficult. The purpose of our study is to assess the outcome of robotic-assisted THA compared to conventional THA in patients younger than 35 years old.

Methods: A retrospective analysis of 123 patients younger than 35 years old that underwent primary unilateral THA between January 2013 and April 2018 was conducted. Patients were divided into two cohorts: (1) robotic-assisted THA and (2) conventional-THA (c-THA). Demographics, operative details, and postoperative outcomes were carefully studied. Radiographic analysis included measurement of postoperative acetabular anteversion and inclination angles as well as postoperative leg length discrepancies. Chi square and unpaired student t-tests were performed for all categorical and continuous variables, respectively.

Results: Of the total 123 patients, 30 patients (32 hips) were in the robotic-THA cohort, and 93 patients (100 hips) were in the conventional-THA cohort. Patients in the robotic-THA cohort were younger (26.6±6.2 vs. 29.0±5.3; p=0.03), had a higher mean BMI (29.8±8.2 vs. 25.7±5.9; p=0.03) at surgery. The most common indication for THA was DDH and osteonecrosis. The acetabular component was positioned within Lewinnek’s safe zone more often in the robotic-THA cohort compared to the c-THA cohort (94% vs 65%; p<0.01) (Figures 1 and 2). Leg length discrepancies were similar between both cohorts. Patients in the c-THA group were more likely to experience clinically significant higher rates of dislocation (2.9% vs. 0), revision (6.8%), any postoperative complication (7.8%), and 90-day readmission (2.9) following THA.

Conclusion: Robotic THA can help improve outcomes in younger THA recipients. Future studies with larger cohorts and longer follow-up times should evaluate outcomes in this historically technically demanding patient population.
Abstract. Surgical navigation systems have been used in orthopaedics for many years. These solutions however often mean additional time and complexity because, essentially, of the markers. We want to introduce a new solution based on depth camera which could be used intraoperatively to estimate the 3D pose of surgical instruments without specific markers. The goal of this paper is to assess, on synthetic data, an algorithm called Clustered Viewpoint Feature Histogram (CVFH) to estimate the pose of an orthopaedic cut guide used during knee surgeries. A specific simulator has been developed for this study which allows the simulation of a point cloud associated to the cut guide. The Average Distance Distinguishable (ADD) metric has been measured 1000 times according to several cut guide orientations and several noise levels. The success rate has also been analyzed. It is commonly considered that the pose is correctly estimated if ADD is less than 10% of the largest dimension of the object. The ADD metric and the success rate vary from 2.12 ± 4.46 mm to 2.82 ± 5.73mm and from 96.0% to 92.4% for respectively a low (0 mm) and a high noise (10mm). The results are very promising. However, more parameters have to be assessed. Similarly, the accuracy and reliability of such method have to be evaluated in a real clinical environment.
Abstract. Conventional radiographic analysis in spinal deformity only quantifies the static skeletal body structure and no conclusions can be drawn with respect to functional abilities. The aim of this work was to introduce subject-specific, skeletal full spine multi- body models in a spinal deformity population for quantifying their full dynamic function. To accomplish this, the creation of a subject-specific model as well as its use with optical motion capture was validated.
As such, this work puts within reach the extension of the current state-of-the-art clinical management from static based concepts with concepts that integrate dynamic functional data.
Abstract. Ultrasound (US) bone segmentation is a key component in many US-based computer assisted orthopaedic systems. Although numerous US bone segmentations techniques exist, there remains no direct way of comparing their performances. This is primarily due to the lack of an accessible US bone image database, and secondly due to a lack of standard vali- dation practices. To address this issue, we are beginning a multi-institutional international collaboration across multiple research centres with the aim of creating an open database for US bone segmentation consisting of several thousand US images and corresponding bone surface segmentations. Our collaboration also aims to address outstanding issues in US bone segmentation, such as determining the reliability of manual segmentations and establishing a set of evaluation metrics which should be reported in future segmentation studies. Finally, we strongly encourage interested researchers to join and contribute to this project as this will help to create a more diverse database and knowledgeable collaboration.
Abstract. Confidence-weighted structured phase symmetry (CSPS) is a state-of-the-art bone seg- mentation technique for ultrasound (US), which has been recently proposed for automatic diagnosis for developmental dysplasia of the hip (DDH). However, CSPS relies on complex image phase feature analysis which is computationally expensive, and in our preliminary tests we have found it to be sometimes inaccurate. We evaluate a simpler alternative segmentation technique which we previously published, called Shadow Peak (SP), which uses intensity analysis to perform fast and accurate US bone segmentation. On average, SP segmentation ran 15 times faster for 2D US images, when tested on 15 hip images of pediatric patients. Furthermore, SP improves the segmentation F-score to 94%, compared to 72% when using CSPS segmentation.
Abstract. Accurate identification of the location the vertebra and corresponding pedicle is critical during pedicle screw insertion for percutaneous spinal fusion surgery. Currently, two dimensional (2D) fluoroscopy based navigation systems have extensive usage in spinal fusion surgery. Relying on 2D projection images for screw guidance results in high misplacement rates. Furthermore, fluoroscopy-based guidance exposes the surgical staff and patient to harmful ionizing radiation. Real-time non-radiation-based ultrasound (US) is a potential alternative to intra-operative fluoroscopy. However, accurate interpretation of noisy US data and manual operation of the transducer during data collection remains a challenge. In this work we investigate the potential of using multi-modal deep convolutional neural network (CNN) architectures for fully automatic identification of vertebra level and pedicle from US data. Our proposed network achieves 93.54% vertebra identification accuracy on in vivo US data collected from 27 subjects.
Abstract. Total knee arthroplasty (TKA) is a reliable surgical procedure, yet up to a fifth of primary implant patients remains unsatisfied. Musculoskeletal modeling (MSM) has the potential to explore the relationship between implant alignment and functional outcome [3]. Consequently, implant alignment can be quantitatively optimized to restore the pre- TKA joint behavior and, therefore, achieve the most favorable functional outcome for the specific patient. For this reason, we developed a method to optimize the implant alignment, with the aim of restoring the native kinematics and ligament elongations of the patient before undergoing TKA. Subject-specific optimization towards ligament elongations demonstrated to accurately emulate the pre-TKA ligament behavior, in contrast to the mechanically aligned approach. However, the values of the optimized implant positions resulting from the pre-TKA kinematic optimization were extreme in some cases. The presented modelling approach is a promising starting point for allowing surgeons to evaluate the patient-specific implant alignment and restore the patient- specific biomechanics.
Abstract. The use of haptic-based robotic-arm assisted total knee arthroplasty (hRATKA) has demonstrated a decrease in soft tissue damage. Hampp et al. [4] compared the soft tissue damage in a cadaveric study between manual total knee arthroplasty (MTKA) and hRATKA and found that the hRATKA specimens had significantly less damage to the PCL than the MTKA specimens [4]. The purpose of this study is to look at the effect of the posterior cruciate ligament (PCL) on kinematics, as defined by anterior-posterior (AP) tibial translation, during stair climb. Using a 6 degree-of-freedom (6-DOF) joint motion simulator, the stair climb profile was run on four cadaveric knee specimens with the PCL intact and the PCL cut. In the PCL deficient condition, there was more posterior tibial motion than when the PCL was intact, and this was more noticeable during the high flexion portion of the profile. These findings speak to the importance of soft tissue preservation, and the development of haptic-based robotic-arm assisted TKA can help prevent soft tissue damage to the PCL.
Abstract. In order to elucidate the accuracy of pelvis osteotomy patient specific surgical guide (PSG) setting comparing between the preoperative planning and intraoperative computed tomography (CT), and to determine the usefulness of PSG comparing between the preoperative planning and postoperative CT in curved periacetabular osteotomy (CPO), we performed experimental study using fresh cadaver samples. A total of 18 hips from 9 fresh cadaveric samples used. All hips were imaged from the whole pelvis to the femoral condyles using helical CT to design the preoperative planning and to produce PSG. PSG consisted of osteotomy guide part and rotation guide part of the bone fragments. CPO with PSG was performed in 9 hips (PSG group) while CPO without surgical guide was performed in other 9 hips (manual group). The absolute errors between the preoperative planning and PSG setting for CPO were acceptable. The absolute errors in PSG group between the preoperative planning and the surgery was significantly smaller in the flexion angle, the anteroposterior direction, and the osteotomy lines of the ilium than in manual group. The PSG for CPO is useful for the osteotomy of the pelvis and for the rotation of the acetabular bony fragment.
Abstract. Surgeon physical stress in the operating room is a known potential cause of musculoskeletal overuse injuries, specifically in surgeons who perform total knee arthroplasty (TKA). Injuries have been attributed to ergonomically challenging postures. This study compared surgeon lower back and shoulder posture between manual TKA (MTKA) and robotic assisted TKA (RATKA).
Two surgeons performed a total six MTKA and six RATKA on a set of cadaveric knees. Movement and EMG sensors were secured to each surgeon to monitor lower back and shoulder movements, as well as muscle activities. Data was analyzed and activities were assessed as low, medium, or high risk, providing a score between 0-lowest and 16-highest. Risk data was compared between MTKA and RATKA for three separate surgical tasks: 1-bone cut preparation & cutting (MTKA = placement of cutting jigs, bone cutting, RATKA = array placement, bone registration, bone cutting), 2-knee balancing and 3-trialing.
Overall, there were more high-risk shoulder than lower back activities in MTKA and RATKA. More high-risk movement and EMG stimulation were measured in the dominant shoulder than the non-dominant. When lower back and shoulder data were combined, highest risk task was bone cut preparation & cutting (MTKA: 13 vs. 6 vs. 6 and RATKA: 11 vs. 8 vs. 6), with a higher risk for MTKA than RATKA.
Poor posture can be a potential cause for surgeon work-related injuries. This study evaluated which tasks presented highest risk to surgeon ergonomic safety while performing TKA, and found lower overall ergonomics risk for performing RATKA vs. MTKA. Although this study provides data indicating reduced ergonomic risk with RATKA, additional studies in the operating room need to be performed.
Abstract. The purposes of this study were to assess 1) number of bone recuts with manual TKA (MTKA) vs RATKA and 2) influence of robotics on surgeon’s posture and workload during recutting.
Two surgeons each performed three MTKAs and three RATKAs. Occurrence, time and type of post-resection recuts were recorded. Movement sensors were placed on surgeons to measure lower back, shoulder, and cervical movements. Data was analyzed for average angle, percent of time in high-risk range of motion (ROM), number of times in high-risk sustained positions, and repetitions per minute. Surgeons were surveyed to assess physical and mental effort on a 1-10 scale (1 as lowest effort).
Six TKAs required recuts, five MTKA and one RATKA. 5 were on tibia and 1 (MTKA) was on femur. Compared to RATKA, MTKA had: increased time to perform recut (4.8-minutes vs. 3.7-minutes), increased occiput and T3 (38.9 vs 17.0° and 16.0 vs 3.0°) average angles, increased lower back ROM, sustained positions, and repetitions (14 vs 0%, 1 vs 0, and 1.9 vs 0), increased non-dominant shoulder ROM and repetitions (22 vs 0% and 2 vs 1), reduced dominant shoulder ROM (56 vs 19%), increased mental (4.2 vs 2.8) efforts and increased physical (3.3 vs 1.7) efforts.
Results indicate RATKA may reduce incidence of post-resection bone recuts. Increased time and required efforts for MTKA may be due to setting up surgical cutting instruments. Whereas, for RATKA, recut changes are made on the robotic surgical screen and the robotic-arm is used to help perform the recut.
Abstract. Implant malalignment during TKA may lead to suboptimal outcomes. Accuracy studies are typically performed with experienced surgeons; however, it is important to study less experienced surgeons when considering teaching hospitals where younger surgeons are operating. Therefore, the purpose of this study was to assess whether computer-assisted TKA (CATKA) allows for more accurate and precise implant position to plan when compared to manual TKA (MTKA) when the surgery is performed by less experienced surgeons.
Two surgeons, currently in their fellowship training and having minimal CATKA experience, performed a total six MTKA and six CATKA on paired cadaveric knees. Computed tomography (CT) scans were obtained for each knee pre- and post- operatively. CT scans were analyzed to compare post-operative implant position to the pre-operative planned position. Mean system errors and standard deviations were compared between CATKA and MTKA for the femoral component sagittal, coronal, and axial planes and the tibial component in the sagittal and coronal planes. A 2-Variance testing was performed using an alpha=0.05.
CATKA had greater accuracy and precision to plan than MTKA for: femoral axial plane (1.1o±1.1o vs. 1.6o±1.3o), coronal plane (0.9o±0.7o vs. 2.2±1.0o), femoral sagittal plane (1.5o±1.3o vs. 3.1o±2.1o), tibial coronal plane (0.9o±0.5o vs. 1.9o±1.3o) and tibial sagittal plane (1.7o±2.6o vs. 4.7o±4.1o). There was no statistical difference between surgical groups or between the two surgeons performing the cases.
With limited CATKA experience, the fellows showed increased accuracy and precision to plan for femoral and tibial implant positions. Furthermore, these results are comparable to what has been reported for an experienced surgeon performing CATKA.
Abstract. Orthopaedic surgery is a mentally and physically demanding procedure for surgeons. Studies reported 44-66% of surgeons surveyed have had a work-related injury attributed to poor surgeon posture. The purpose of this study was to understand how surgical variables may affect a surgeon’s posture and workload when performing TKA. Variables included: influence of level of surgical experience, type of surgical procedure, and specific surgical tasks.
Two experienced surgeons, with a median 22-years surgical experience, and 2 surgeons, currently in their fellowship training, each performed 3 manual TKAs (MTKA) and 3 robotic assisted TKAs (RATKA) using a cadaveric setup. Kinematic sensors were placed on the occiput and T3 to measure flexion of the head and neck. Surgeons were surveyed to assess their physical and mental effort using a 1-10 scale (1 being least effort).
Compared to the fellows, experienced surgeons had reduced occiput and T3 angles for MTKA (28.0 vs. 38.7°, 4.2 vs. 15.7°) and RATKA (18.0 vs. 29.2°, 4.8 vs. 13.2°) as well as reduced mental and physical effort. Considering surgical procedure, all surgeons had reduced occiput angles for RATKA compared to MTKA. Considering surgical task, surgical application (MTKA vs. RATKA) had greater influence on cervical angles for the fellows group.
All three factors influenced the surgeon’s posture and workload. Occiput angle was reduced by approximately 10° during RATKA, which is attributed to the surgeon standing in a more upright position, to visualize the robotic screen during cutting and trialing. Robotics may help newer surgeons better visualize knee balancing during TKA, easing the process of balancing and trialing.
Abstract. This paper describes the development, functionality, and initial testing of a wearable sensor system and companion smartphone app intended to support the rehabilitation of Achilles injury patients by providing 1) real time biofeedback, which can help patients adhere to rehabilitation restrictions; 2) exercise support to encourage patients to correctly perform all rehabilitation activities; 3) data summaries to clinicians in order to allow appropriate interventions when necessary. The wearable system is composed of insole pressure sensors, a calf muscle activation sensor, and inertial measurement units, whose data are communicated to the smartphone app via a Bluetooth enabled microcontroller. Initial testing demonstrated the quality of the data recorded by the sensors and the ability of those data to be used to identify functional activities like walking and stairclimbing.
Abstract. Introduction
Clinical benefits of intra-operative 3D imaging and surgical navigation are widely described in the literature. However, existing guidance systems are often reported as complex and time consuming1,2,4. The Surgivisio / eCential system is an innovative intra-operative C-arm combining 2D fluoroscopy, 3D imaging and real time navigation capabilities within unified an all-in-one platform3.
The aim of this cadaveric experimentation is to evaluate the usability of the system, and to assess pedicle screw placement using this novel device.
Material and methods
Surgivisio / eCential device offers an all-in-one solution with a unique workflow and user interface. The embodiment used here is dedicated to any spinal procedures requiring insertion of a trocar inside a pedicle.
The usability of the system is assessed by measuring the ability of the user to navigate the trocar and place k-wires percutaneously inside a group of pedicles.
The accuracy of screw placement is evaluated using post-operative 3D image of the implanted screw exported on an internally developed image visualization tool. The screw placement is assessed according to Gertzbein grading scale by the operator and two other evaluators.
For each vertebrae group, fixation of the patient reference to the end of 3D reconstruction was done in less than 10 minutes. The percutaneous navigation and placement of 6 k-wires in a vertebrae group could be performed in 28 minutes for the first 2 groups and in 22 minutes for the third group.
Pedicle screw implantation
100% of screws was graded 0 on Gertzbein scale by all evaluators.
Abstract. Aims:
Approximately 20% of patients are dissatisfied with their total knee arthroplasty (TKA). Purpose of this study was to determine if patient satisfaction could be improved following TKA using computer technology to obtain the target alignment and precisely balanced gaps.

Patients & Methods:
75 consecutive patients undergoing primary robotic-arm assisted TKA (RA-TKA) with real-time intraoperative alignment and gap balancing information were compared with a prospective cohort of 75 consecutive patients undergoing primary TKA with manual jig-based instruments during the same time period. There were no differences between groups with age, gender, BMI, and ASA scores. TKA’s were performed by a single surgeon using same implant design, anesthesia and surgical protocols. Patient satisfaction survey using Knee Society (KSS) and Likert scoring system was obtained at 1-year follow-up.

Likert scoring system demonstrated 95% of patients in the computer technology group were either very satisfied or satisfied versus 75% in the manual instruments TKA group (p=0.005) at 1-year follow-up. Second question of the KSS which deals with pain at rest was significantly better in RA-TKA group (p=0.04). Fifth question which deals with recreational activities was also significantly improved in the RA-TKA group, p=0.02. RA-TKA group had a better average overall satisfaction score of 7.1 versus 6.4 in the manual instrument group, p=0.03.

Using intraoperative computer technology to achieve the target alignment with flexion/extension gap balancing to within 1mm, a significant improvement in patient satisfaction was demonstrated compared to TKA using conventional manual jig-based instruments.
Abstract. Introduction:
There is a lack of data concerning the use of the robotic device for patients with other potentially complex surgical factors. Therefore, the purpose of this series was to present cases in which the robotic-arm assisted TKA (RATKA) application was used in the setting of extra-articular deformities to educate the surgeon community on this potentially useful method to address these complex cases.

Three cases of patients who underwent RATKA in the setting of pre-operative extra-articular deformities were identified. One had femoral and tibial fracture malunion, another had proximal tibial fracture nonunion, and another with a healed tibial plateau fracture. Patient clinical histories, intra-operative surgical techniques, and post-operative outcomes were obtained. Specific focus was placed on the surgical management of the patient’s pre-existing deformity.

The robotic software was able to appropriately consider the extra-articular deformity in the pre-operative and real-time updated intra-operative plans. Doing so, the surgeon achieved a balanced and aligned TKA. No intra-operative or post-operative complications occurred. Antero-posterior and lateral radiographs demonstrated well fixed and aligned femoral and tibial components with no signs of loosening or osteolysis. On physical exam, all patients had excellent range of motion with mean flexion of 122 degrees (range: 120 to 125 degrees of flexion) at final follow-up.

Utilizing pre-operative CT-scans with a 3D plan for robotic-arm assisted surgery allowed for appropriate assessment of the deformity pre-operatively and execution of a plan for a balanced and aligned total knee arthroplasty. We have demonstrated excellent results utilizing robotic-arm assisted TKA in these complex cases.
Abstract. In Total knee arthroplasty (TKA), not only knee joint affect when we restored limb alignment, but also other joints involved. Ankle joint is one of them. By changing in talar tilt, many studies shown this will lead to increase pain and disturb function of ankle. Patients may end up with unsatisfied result of TKA. Anatomical cut of tibia is use in order to avoid this problem.
To compare between pre- and post-operative talar tilt angle (TTA) and ankle clinical assessment by foot function index (FFI) and ankle-hindfoot index (AHI) after anatomical tibial cut (varus 3° with anatomical axis) and conventional tibial cut (perpendicular with anatomical axis) in computer-assisted total knee arthroplasty
This study was retrospective study. We collected data of 70 knees from 54 patients. 32 knees were done by anatomical cut. The rest were conventional cut. We evaluated at pre- and post-operative for TTA. At 12-month follow-up for TTA & ankle clinical assessment.
In conventional group, TTA was changed 2.33°(p<0.001) then 0.920(p=0.02) at follow up. In anatomical group, TTA was changed 2°(p=0.037) then 1.38°(p=1.56). Changing of TTA was not significantly different at post-operatively (p=0.76) and follow-up (p=0.98) between 2 groups. FFI& AHI were not significantly different between both groups.
Abstract. This study aimed to investigate whether use of a computed tomography (CT)-based navigation system reduce the risk of dislocation after total hip arthroplasty (THA) in patients with osteonecrosis of the femoral head (ONFH). A total of 271 hips from 192 consecutive patients that underwent primary THA for ONFH were included. There were 110 hips in non-navigation group, and 161 hips in navigation group. After applying exclusion criteria, 209 hips from 149 patients were selected for this study. Clinical outcomes and complication rates were evaluated, and implant alignments were also calculated. To identify whether the navigation system was useful to prevent dislocation, the inverse probability of treatment weighted Cox regression analysis using a propensity score in relationship to sex, age at surgery, body mass index, and femoral head size was performed. No significant difference was observed in clinical scores between both groups. Dislocation was significantly lower in the navigation group (3 hips, 2.7%) than in the non-navigation group (11 hips, 11.2%; p = 0.012), whereas periprosthetic joint infection and aseptic loosening did not differ between the groups. Variance of cup angle was smaller in the navigation group than in the non-navigation group (p < 0.001). Use of the CT- based navigation system (HR; 0.26, 95% CI, 0.07–0.98; p = 0.047) turned out to be the predictor for preventing dislocation. In conclusion, use of the CT-based navigation system provided a precise placement of components, and thus help prevent dislocation in patients with ONFH in the propensity score analysis.
Abstract. Complication following UKA in medial compartment OA knee often related to rotatory malposition of the femoral component The purpose of this study was to study outcome following Femoral component rotation angle after unicompartmental knee arthroplasty using the anatomical tibial component cutting technique with computer-assisted surgery by CT-scan measurement in Rajavithi hospital
Retrospective descriptive study of 16 patients performed medialUKA in Rajavithi Hospital Bangkok Thailand.Single orthopedic surgeon and using computer-assisted with anatomical tibia cutting technique(tibial resection in 3-degree varus).
The femoral component rotation was assessed in an axial cut CT scan. measure angle between Epicondylar axis and Posterior condylar axis
The authors analyzed 16 knees with mean age about 56 years, male 2 Female 14 and the mean BMI was 24 kg/m 2 (average body weight 63 kg)
Mean of Femoral component rotation angle in this study is 2.94-degree internal rotation(internal rotation compare with Epicondylar axis). A range of femoral component internal rotation was 0-6 degree .mean varus-valgus angle was 1.81-degree varus and mean flexion-extension angle was 5.56-degree flexion
Femoral component rotation angle in unicompartmental knee arthroplasty(UKA) in medial compartment osteoarthritis knee with using of the computer-assisted with anatomical tibia cutting technique have a favorable result (Mean = 2.94-degree internal rotation 1.81-degree varus and 5.56-degree flexion).
Abstract. CT-fluoro matching (CFM) registration is one of the registrations for CT-based navigation developed by Brainlab company, in which the contours of the intraoperative fluoroscopic 2D X-ray images were matched to the contours of 3D pelvic and femoral models created based on the preoperative CT images. Brainlab company stopped to provide CT-based navigation and shifted to imageless navigation for THA. Therefore, clinical efficacy of this CFM registration is not well known. We analyzed the accuracy of implant position and postoperative complications after CT-based navigation assisted THA of 45 cases (43 females, 2 males, average age: 72.7 y.o.) using CFM registration and cementless implants (SQRUM cups and J-Taper high offset stems [Kyocera, Japan]). The differences (average ± standard deviation of absolute values, [95% confidence interval]) between the pre- and post- operative angles of cup inclination, anteversion, and stem antetorsion were 2.2 ± 1.50, [1.8~2.60], 3.7 ± 3.10, [2.9~4.60], 5.9 ± 4.50, [4.6~7.10], respectively. The differences (average ± standard deviation of absolute values, [95% confidence interval]) between the intra- and post-operative angles of cup inclination, anteversion, and stem antetorsion were 2.2 ± 1.70, [1.7~2.60], 2.3 ± 2.10, [1.7~2.80],4.6 ± 3.00, [3.7~5.40], respectively. These values were clinically acceptable when we compared with the previous accuracy studies of CT-based navigation using surface matching registration. There was no dislocation after THA in this study. From these results, CFM registration is useful for THA. However, this CT-based navigation with CFM registration will be discontinued in near future. Novel CT-based navigation systems should be developed based on this CFM registration procedure.
Abstract. Vertebroplasty (VP) is the gold standard for vertebral compression fracture (VCF) treatment. VP could be improved by using intra operative cone bean computed tomography (CBCT) although duration is largely increased. We report first series of 51 patients whom underwent VP integrating intraoperative navigation to CBCT, in order to cut down time consumption. During a 8 month period, 51 patients were prospectively enrolled. The mean age was 71 years old (36-94). There were 17 male and 35 female. We stored 65 VP (14 thoracic and 51 lumbar). After percutaneous pins fixation to the spinous process of the “Butterfly” acquisition reference frame, 180° rotation of the C-arm CBCT (Surgivisio®, eCential, Grenoble France) generated a 3D volume. Optically localized, sterile self- calibrated trocar was navigated in order to reach the vertebral body center by an unilateral pedicular approach. Cement (Vertaplex HV®, Stryker) was injected under fluoroscopic lateral view by the same machine, using standard 2D X-ray modes. Considering the 38 patients who underwent 1 level VP, mean time procedure was 00:30:09 [00:21:00 to 00:54:00; SD 00:10:23]. The mean DAP was 5,41318 Gy.cm2 and mean exposure duration 3,68 seconds. The mean efficient dose (E) was 1,32 mSv. In all cases cement placement was classified as excellent or mild, without any leakage. This new C-arm CBCT with integrated navigation is efficient to dramatically decrease operating time in comparison to literature (00:46:00 to 00:52:08). The reduction of radiation dose is already demonstrated in literature for navigated VP.
Abstract. Femoral component recreation of the trochlear groove is a major factor in determining post-operative patello-femoral tracking. Significant variation arises in recreation of the trochlear groove when a standardised implant design is applied to variable patient anatomy and alignment. However, the impact of variation on patient outcome is not well understood. This study sought to understand whether the accuracy of recreation of the trochlear groove drives patient outcome following total knee arthroplasty (TKA). 430 TKA patients were analysed; patients had pre- and post-operative CT scans and postoperative Knee Injury & Osteoarthritis Outcome (KOOS) scores at 6 months post- surgery. Based on the pre- and post-operative CT scans, femoral trochlear groove positioning and the post-surgery “build-up” of the medial and lateral apex either side of the groove were modeled and measured. Correlations between changes to this native morphology and KOOS scores were statistically tested. Patients who had increased implant build-up on the trochlear lateral apex had a worse outcome (correlation with KOOS Pain score: r = -0.2, p = 0.03), and this was found to be driven by impairment when straightening and pain when bending. The results suggest that reducing the proximal lateral apex of the trochlear groove post-implantation leads to improved patient outcomes when straightening the knee, with implications for both implant design and target component placement.
Abstract. A promising measure of dynamic outcomes in Total Knee Arthroplasty (TKA) is the simulation of joint dynamics. These simulations are potentially useful for pre-operative planning, but are not yet validated for patient-specific variations in anatomy, which forms the aim of this paper. 284 patients from a database of total knee arthroplasty patients were analysed using a pre-operatively defined simulation predicting post-operative knee dynamics; each patient had previously undergone pre- and post-operative CT imaging and had been assessed using the Knee Injury and Osteoarthritis Outcome (KOOS) score at 6 months following surgery. A significant correlation was found between the simulated contact force and laxity in mid-flexion (r=-0.452, p<0.0001), and between the medio- lateral difference in contact force and difference in distal-vs-posterior femoral collateral ligament offset (r=-0.473, p<0.0001). A significant difference of 5 KOOS pain points (p=0.02) was found for patients with unusually low or high simulated contact force compared to normal. These results indicate the preoperative simulation is capable of distinguishing patient-specific kinematics prior to surgery, thereby demonstrating the utility of this simulation for making pre-surgical predictions of patient-specific kinematics and patient-reported outcomes.
Abstract. During the last few years, total knee arthroplasty has evolved from basic surgery to restore basic function, to a fast-track procedure to relief pain and get the patients back to a high level of activity.. However, the way physiotherapy is performed, remained the same. This paper presents the results of 185 patients that used a mobile health application to track their recovery. Adherence and clinical results were evaluated and reported. Our study demonstrated an excellent patient acceptance and compliance of the outpatient autonomous recovery app. Patient satisfaction was outstanding, and functional recovery was securely within conventional range.
Abstract. Proximal tibial resection is an important surgical step in total knee arthroplasty (TKA). Normally, an anterior surface of tibia used as anatomical landmark (extramedullary method), this method based on visual judgment. (D.C. Marchant, 2005) calculated ratio for center of the ankle, ratio of lateral distance to total inter-malleolar distance was observed at 0.57 in normal ankle sample. However, there is no study documenting about accuracy of ratio for center of the ankle as a landmark for proximal tibial resection in computer assisted TKA (CAS TKA).
This was prospective study on 65 patients with osteoarthritis knees scheduled to receive CAS TKA from January to December 2018. Proximal tibial resection was simulated by extramedullary method and ratio for center of the ankle respectively. Tibial resection alignment were recorded by CAS.
Tibial resection alignment within 3 degrees was 84.6 and 92.3% for extramedullary method and ratio for center of the ankle method. The average total tibial resection alignment was 0.84 and 0.66 degrees of valgus (p = 0.497), the average tibial resection alignment within 3 degrees from mechanical axis was 0.33 and 0.55 degrees of valgus (p = 0.513) and the average tibial resection alignment more than 3 degrees from mechanical axis was 3.60 and 1.5 degrees of valgus (p = 0.049) for extramedullary method and ratio for center of the ankle method respectively.
Ratio for center of the ankle demonstrated result in numeric value and anatomical landmark of lateral and medial malleoli was simple to identified. Our results shown the tibial resection alignment with ratio for center of the ankle method had higher accuracy and lower average degrees of outlier than extramedullary method.
Abstract. Background: Under very limited circumstances euthanasia can be performed in Belgium since 2002 (Verwilghen, 2012). If a patient has medical condition with no hope on improvement, with physical and/or psychological suffering, he can ask for terminating his life. The written demand is on voluntary bases, well considered, repeated and was not induced due to external pressure from other people. Neuromonitoring has been used in spine surgery during the last four decades. (Lall, et al., 2012) (Gonzales, Jeyanandarajan, Hansen, Zada, & Hsieh, 2009) With the development of new modalities, new applications were introduced in spine surgery in order to avoid neurological damage during surgical procedures.
Method: A patient with a partial recovered ASIA A C7 quadriplegia suffering from wounds caused by his spinal instrumentation had intraoperative neuromonitoring. In case he became dependent for his personal care, he wanted to have euthanasia executed on him.
Conclusion: So far there is no literature on the use of neuromonitoring to avoid euthanasia in cases where spinal surgery is needed, but surgery has an inherent risk of causing damage to nerval structures, which can cause loss of recovered nerve function after spinal cord injury. This potential loss of independence was an unbearable physical and psychological suffering the patient would not want to go through again. By using neuromonitoring, the key muscles were observed during the surgery. No neurological events were seen during the prodecure. He had some general weakness after the surgery but kept his autonomy, so no euthanasia was needed.
Abstract. In reverse total shoulder arthroplasty stability is primarily controlled by the soft-tissue constraints rather than the congruency of the articulating surfaces. However, assessing the tension in these stabilizing structures currently remains highly subjective intra- operatively. In an attempt to quantify this feel during surgery, an intra-articular load sensor is introduced in this paper. In an in-vitro setting, the load sensor was used in eight reverse total shoulder arthroplasties on full torso specimens. The specimens were mounted on an inclined chair, such that the scapula could freely move to mimic surgical conditions. The resulting load vectors were captured through the range of motion under three different conditions, subjectively categorized by the surgeon as having a low, normal and high tightness. In neutral rotation and under a subjectively optimal condition assessed as neither too tight nor too loose, glenohumeral loads in the range of 10-20lbs were observed. For the same subjectively assessed optimal shoulder, loads up to 30lbs were observed under maximum internal/external humeral rotation. This contrasts the subjectively assessed loose and tight conditions, where lower resp. higher loads were observed that additionally affected the range of motion. On the other hand, stability was potentially missing under loose conditions as no increase in load was observed near the limits of the range of motion, indicating the lack of soft tissue restraint. In conclusion, this series of in- vitro experiments has shown the relevance and potential clinical value of assessing a shoulder’s stability and mobility using intra-articular load measurements during the trialing phase.
Abstract. INTRODUCTION: Most dislocations have been shown to occur within Lewinnek’s proposed safe zone (LSZ) for cup inclination (40°±10°) and anteversion (15°±10°). Using a functional and dynamic simulation that accounts for individual patient anatomy and variations in pelvic tilt, we created a patient-specific target orientation for the acetabular cup. The purposes of this study were to: (1) compare pre-operative acetabular cup parameters using this novel dynamic imaging sequence to the LSZ, and (2) describe rates of dislocation in patients whose pre-operative acetabular cup parameters were determined using dynamic imaging sequences.
METHODS: We retrospectively reviewed 1,500 consecutive, primary THAs that underwent dynamic sitting and standing pre-operative acetabular cup planning. Using these inputs, we modeled an optimal cup position for each patient. Inclination, anteversion, pelvic tilt, pelvic incidence, lumbar flexion angles, and rates of dislocation were analyzed.

RESULTS: Mean age of patients was 63 years. Mean pelvic tilt was 4.7o when supine, -0.3o when standing, and -0.7o when flex-seated. Mean pelvic incidence was 54o and mean lumbar flexion was 43o. Mean inclination was 40° and mean anteversion was 24°. Only 56% of the dynamically planned cups were within the LSZ (p<0.05). Mean inclination and anteversion difference between dynamic and LSZ was 1.3o and 8.9o, respectively. Only 0.5% of dynamically planned cups dislocated post-operatively, all were within LSZ.
DISCUSSION: Acetabular cup positioning in patient-specific safe zones reduces the rate of dislocation after THA. Historical target parameters for cup inclination and anteversion significantly differ to target values obtained with the use of functional imaging.
Abstract. With the increasing spread of computer assisted surgery, more and more modern operating rooms are equipped with navigation systems, each coming with its own tracking camera. Since those cameras are part of the closed monolithic navigation system, they can’t be used for other applications than the one intended by the supplier. With the novel service oriented device connectivity standard (IEEE 11073-SDC), introduced by the OR.NET initiative (, needless double procurements could be avoided and multiple systems could use the same camera that – similar to OR lights – could be installed as a standard equipment in each OR. This would decrease the cost-to-benefit ratio also of new applications that would currently as such not justify to acquire a proprietary tracking camera.
While the integration of a tracking camera to an open medical device IT network can open up for new applications, it should on the other hand not impair the usability and the safety of the navigation system. Therefore, a low latency must be guaranteed between tracking camera and navigational display.
This paper evaluates the integration of an atracsys fusionTrack 500 tracking camera into the OR.NETwork. The response time from a change in the real world to the reception of the corresponding data package is measured to determine the feasibility of an integra- tion without impairing current navigational tasks.
The results show that, as long as the underlying network infrastructure is not at its capacity limit, latencies below 60 ms are achieved. Therefore, the integration of a tracking camera for navigational tasks is feasible.
Abstract. The paper presents an approach for computer-assisted implantation of artificial hip joints. It is based on a novel solution combining pre-operative planning and intra- operative navigation in a way that the natural anatomy of the joint before surgery can be restored as close as possible, or with exactly planned modifications. A surgical workflow has been developed which highly focusses on the registration and restoration of patient specific parameters instead of using generalized criteria like the Lewinnek safe zone. The feasibility of the approach has successfully been demonstrated by a laboratory setup of Sawbone models.
Abstract. Kinematic alignment (KA) aims to restore the pre-arthritic geometry of the joint and has been shown to produce similar or improved outcomes compared to mechanical alignment (MA). However, there are significant challenges when attempting to restore outlier joint anatomy. This study sought to investigate how achieved TKA alignment correlates with 12 month patient outcomes. The study considered three categories of achieved TKA alignments: KA, MA, or conservative KA (restricting coronal component alignments to within 5° and combined coronal alignment to within 3° of neutral). 369 patients were analysed; each patient had pre- and post-operative CT scans and a 12-month postoperative Knee Osteoarthritis & Outcome Score (KOOS). From CT scans, component positions were measured, and patients were categorized to one of the three categories. The conservative KA group were least likely (76%) to reach the threshold KOOS Pain score set by the Patient Acceptable State Score (PASS); the full KA group was most likely (95%) to reach the threshold, whilst the MA group was in between these two groups (88%). These results demonstrated an increase in pain when the achieved alignment formed a compromise between a restorative and a reconstructive approach, and further suggests that conservative approaches to kinematic alignment may require a high level of discretion.
Abstract. To investigate the accuracy of a novel 3D CT scan-based preoperative planning software linked to patient-specific instrumentation (PSI) for placing acetabular components planning in patients with acetabular dysplasia undergoing total hip arthroplasty (THA). A total of 30 consecutive patients were prospectively enrolled and the accuracy of placement of the acetabular component was measured using post- operative CT scans. There was good reproducibility of preoperative and postoperative position of reconstructed rotation center. The mean absolute deviation from the planned inclination and anteversion was 6.2° and 4.8°, respectively. In 90% of cases the planned target of +/-5° was achieved for both inclination and anteversion. And 95% of cases of planned target of +/-3mm were achieved for vertical height of rotation center. Accurate placement of the acetabular component can be achieved using patient-specific guides and is superior to free hand techniques.
Abstract. The aim of this study was to investigate the accuracy in performing a femoral resection and the existence of a learning curve in conducting TKA using the KneeAlign2 system. 86 primary TKAs were enrolled in this prospective study. These patients were divided in two groups.Group1: patients operated by surgeon of experience using the KneeAlign2 system more than 30 cases.Group2: patients operated by surgeons of experience using the KneeAlign2 system less than 30 cases. The radiographic results (alignment of the femoral component) and operation time were compared between the groups. There were no significant differences between the groups .The KneeAlign2 system provides usefulness in performing an accurate distal femoral resection at TKA. As the learning curve does not be observed, this portable navigation system is easy to handle even for less experienced surgeons.
Abstract. Background: Balancing is important to outcomes, but has been difficult to achieve due to the high sensitivity of the condylar forces to even small changes in ligament lengths. The first goal was to measure the effects of alignment and component placement errors on balancing. The second goal was to study equivalence between the collateral ligament forces, distraction forces, and condylar contact forces.
Methods: The test rig flexed and extended synthetic knees, while condylar forces and ligament forces were measured. For ideal femoral component placement, the sagittal contours exactly matched anatomic. 2mm placement errors relative to anatomic were distal (too little distal femoral resection), proximal, anterior, and posterior. Condylar forces for anatomic placement were defined as reference, while forces for the different placement errors were measured relatively.
Results: Condylar forces were significantly influenced by 2mm errors in femoral component placement. For distal placement error in combination with kinematic alignment, there were only small changes in the contact forces. Other placement errors produced large contact errors. For mechanical alignment medial forces were similar to kinematic, but lateral forces reduced to almost zero. The medial and lateral ligament and contact forces, distraction forces, and lift-off moments were highly correlated.
Conclusions: The ideal situation was kinematic alignment, which could reproduce the condylar contact forces seen in intact anatomic knees. The least condylar force errors occurred when the femoral component was placed too distally, for the kinematic alignment bone cuts. Different balancing parameters can be used interchangeably.
Abstract. Haptic robotic-arm assisted technology improves accuracy in unicompartmental knee replacement through utilizing a preoperative 3-D plan, optical navigation for real-time intraoperative feedback on soft tissue laxity, and robotic arm for precise bone preparation. This technology became clinically available for total knee arthroplasty (TKA) in 2016. We present outcomes from the early adoption of this technique.
A retrospective chart review compared data from the first 120 robotic-arm assisted TKAs performed December 2016 through July 2018 to the last 120 manually instrumented TKAs performed May 2015 to December 2016, prior to robotic technology adoption.
Robotic surgery was associated with significantly increased anesthesia (212 vs 187 mins, p < 0.01) and operative (135 vs 112 minutes, p < 0.01) time. The robotic group had a lower hospital length-of-stay (2.7 vs. 3.4 days, p < 0.001). Discharge to home was not statistically different between robotic and manual groups (89% vs. 83%, p = 0.2). Robotic technology was associated with decreased variability in implant positioning, with smaller variances in the lateral distal femoral angle (LDFA; 3.5 vs 6.6 degrees, p < 0.01) and posterior tibial slope (1.8 vs. 5.3 degrees, p < 0.01). Mean limb alignment, as measured by tibiofemoral angle, was slightly less valgus in the robotic group (3.9 vs 4.4 degrees, p = 0.09). Postoperative range of motion was significantly increased for robotic-arm assisted TKA patients, with less flexion contracture at 2-weeks (1.8 vs. 3.3 degrees, p < 0.01), 7-weeks (1.0 vs. 1.8 degrees, p < 0.01), and 3-months (0.6 vs 2.1 degrees, p = 0.02) post-surgery. Postoperative Knee Society scores were similar between groups.
Preliminary findings demonstrate robotic-arm assisted TKA is safe and efficacious with outcomes comparable, if not superior, to that of manually instrumented TKA.
Abstract. Studies have shown that dissatisfaction following TKA may stem from poor component placement and iatrogenic factors related to variability in surgical execution. A CT-based robotic assisted system allows surgeons to dynamically balance the joint prior to bone resection. This study aimed to determine if this system could improve TKA planning, reduce soft tissue releases, minimize bone resection, and accurately predict component size.
Six hundred and sixty-six cases undergoing primary robotic assisted TKA we enrolled in a prospective, multicenter study. Seven surgeons participated from seven US centers. Patient demographics and intraoperative surgical details were collected. Initial and final 3-dimensional alignment, component position, bone resection depths, use of soft tissue releases, knee balancing gaps, and component size were collected intraoperatively. Descriptive statistics were applied to determine the changes in these parameters between initial and final values.
In this study, 513 varus knees, 86 valgus knees, and 26 neutral knees were captured and stratified for analysis. Native deformity ranged from 12 degrees of valgus to 19 degrees of varus. 85% of all patients in this study did not require a soft tissue release. Complex deformities who required a soft tissue release were corrected on average to 3.36 degrees while cases without releases were corrected to 1.1 degree on average. All surgeons achieved their planned sizes on the tibia and femur more than 97.5% of the time within one size, and 100% of the time within two sizes. Flexion and extension gaps during knee balancing were within 2mm (mean 1mm) for all knees.
New tools may allow for enhanced execution and predictable balance for TKA, which may improve patient outcomes. In this study, preoperative planning via CT scan allowed surgeons to assess bony deformities and subtly adjust component position to reduce soft tissue trauma. Patient follow up is needed to determine clinical outcomes.
Abstract. The purpose of this work was to determine the number of soft tissue releases and component orientation of valgus cases performed with Robotic-Arm Assisted total knee arthroplasty (RATKA).
This study was a retrospective chart review of cases performed by a single surgeon from July 2016 to December 2017. 72 RATKA cases were defined as having a valgus deformity pre-operatively. Patient demographics and intraoperative surgical details were collected, including initial and final 3D component alignment, knee balancing gaps, full or partial releases. Post- operatively, radiographs, adverse events, and reduced WOMAC pain and KOOS Jr scores were collected at 6 months post-operatively.
Pre-operatively, knee deformities ranged from 1o to 12° with fixed flexion contracture. All knees were corrected within 2.5 degrees of mechanical neutral. Medial and lateral gaps were balanced in extension 100% of cases and flexion 93% of cases.
Radiographic evidence suggested well seated and well-fixed components. No revision and re- operation is reported. Patient reported outcomes measures collected at 6-month follow up indicated an improvement in WOMAC pain score from 9.6 to 3.2 and improvement in KOOS Jr from 44.7 to 74.4 points.
In this retrospective case review, soft tissue releases were not needed to address valgus knees ranging from 1-12° of deformity. The surgeon was able to balance the knee with bone resections and avoid disturbing the soft tissue envelope. While this study has a number of limitations, RATKA for valgus knees should continue to be investigated in a multicenter study.
Abstract. Component position and overall limb alignment following Total Knee Arthroplasty (TKA) have been shown to influence device survivorships and clinical outcomes. However, these parameters are often assessed through 2D radiographs after surgery, which can be prone to inaccuracy. The purpose of this paper is to develop a new method for 3D CT based overall limb alignment and component position measurements. The technique utilizes a new mathematical model to calculate prosthesis alignment from the coordinates of anatomical landmarks used in RATKA. The hypothesis is that the proposed technique demonstrated good accuracy, as well as low intra and inter-observer variability.
Two groups of patients (n=120 per group) underwent RATKA and conventional TKA at 4 imaging locations between October 2016 and August 2018, where they were recruited and consented for this prospective, non-randomized, multicenter study. CTs were collected 6 weeks post-operatively and analyzed using RATKA landmarks and the proposed technique. Measurements of 30 randomly selected cases were compared to the surgeons’ operative plan and component target positions for accuracy analysis. Two surgeons performed the same measurements separately for inter-observer variability analysis. One of the two surgeons repeated the measurements 30 days later to assess intra-observer variability.
Average measurement error of overall limb alignment, femoral and tibial component positions were less than 1 degree. Bland Altman plots analysis showed great reproducibility between observers. Correlation analysis showed low variability within observer, with slopes between 0.8 to 1.0 and R-squared > 0.8.
The proposed method demonstrated great accuracy to plan and low intra and inter-observer variability. This can be a great tool for RATKA studies where component accuracy is assessed using post-operative CTs.
Abstract. For cup implantation in dysplastic acetabulum, the vertical height of the cup center (V-HCC) should be carefully and precisely controlled in order to achieve sufficient host bone-cup coverage (BCC), but excessively superior placement of the cup should be avoided. Using computer software, pelvis models were separately reconstructed in 51 patients (61 hips) with severe osteoarthritis secondary to Crowe type I-III hips. Acetabular height and doom thickness were measured on the mid-acetabular coronal cross section. V-HCC was defined as the vertical distance from the cup center to the interteardrop line (ITL). In the cup implantation simulation, the cup was placed at the initial preset position, with a V-HCC of 15 mm, and moved proximally by 3-mm increments. At each level, the BCC was automatically calculated by computer. There were no significant between-group differences in maximum thickness of the acetabular doom; however peak bone stock values were obtained at heights of 41.63 mm ± 5.14 mm (Crowe type I), 47.58 mm ± 4.10 mm (Crowe type II), and 55.78 mm ± 3.64 mm (Crowe type III) above the ITL. At 15 mm of HCC, BCC was 79%±7% (Crowe type I), 74%±9% (Crowe type II), and 61%±6% (Crowe type III). In order to achieve 80% of the BCC, the evaluation distance was 1.33 ± 1.62 mm (95% CI 0.67–2.01), 3.32 ± 2.94 mm (95% CI 1.94–4.69), and 9.68 ± 3.91 mm (95% CI 7.60–11.77) for Crowe type I, II, and III hips, respectively. Acetabular bone stock for cup placement correlates with the degree of hip dysplasia in patients. During acetabular reconstruction in Crowe type I, II, or III hips, slightly superior placements, <25 mm from the ITL, retained sufficient bone coverage.
Abstract. In order to help orthopedists, evaluate the morphological characteristics of the acetabulum of patients with osteoarthritis, a 3-dimensional (3D) acetabular morphologic parameters measurements software dedicated to the hip was developed. The system includes three modules: 1) Identify the anterior pelvic plane (APP) of the pelvis model; 2) Identify the circular rim of the acetabular wall; 3) Automatically and interactively measure the 3D morphological parameters of the dysplastic acetabulum. The automatic parameter measurement function of this software could fast and accurately measure the 3D morphological parameters of the dysplastic acetabulum. These automatically measured parameters were close to those measured manually with error generally less than 2mm. This software was used to measure acetabular morphological parameters in 61 patients. Two types of dysplastic acetabula were identified by the thickness of the medial wall on the lower margin of the acetabulum Tb: type I was a thin acetabulum (35 cases, Tb≤10.0 mm) and type II was a thick acetabulum (26 cases, Tb >10.0 mm). the result of the acetabular morphological characteristic analysis, it can be found that the thickness of the medial wall is an important morphological characteristic for the THA preoperative surgical planning, and the thickened medial wall could be a misleading factor for the suboptimal placement of the cup.