Aims

Computer-assisted 3D preoperative planning software has the potential to improve postoperative stability in total hip arthroplasty (THA). Commonly, preoperative protocols simulate two functional positions (standing and relaxed sitting) but do not consider other common positions that may increase postoperative impingement and possible dislocation. This study investigates the feasibility of simulating commonly encountered positions, and positions with an increased risk of impingement, to lower postoperative impingement risk in a CT-based 3D model.

Aims

It is unknown whether gap laxities measured in robotic arm-assisted total knee arthroplasty (TKA) correlate to load sensor measurements. The aim of this study was to determine whether symmetry of the maximum medial and lateral gaps in extension and flexion was predictive of knee balance in extension and flexion respectively using different maximum thresholds of intercompartmental load difference (ICLD) to define balance.

Aims. In-hospital length of stay (LOS) and discharge dispositions following arthroplasty could act as surrogate measures for improvement in patient pathways, and have major cost saving implications for healthcare providers. With the ever-growing adoption of robotic technology in arthroplasty, it is imperative to evaluate its impact on LOS. The objectives of this study were to compare LOS and discharge dispositions following robotic arm-assisted total knee arthroplasty (RO TKA) and unicompartmental arthroplasty (RO UKA) versus conventional technique (CO TKA and UKA). Methods. This large-scale, single-institution study included patients of any age undergoing primary TKA (n = 1,375) or UKA (n = 337) for any cause between May 2019 and January 2023. Data extracted included patient demographics, LOS, need for post anaesthesia care unit (PACU) admission, anaesthesia type, readmission within 30 days, and discharge dispositions. Univariate and multivariate logistic regression models were also employed to identify factors and patient characteristics related to delayed discharge. Results. The median LOS in the RO TKA group was 76 hours (interquartile range (IQR) 54 to 104) versus 82.5 (IQR 58 to 127) in the CO TKA group (p < 0.001) and 54 hours (IQR 34 to 77) in the RO UKA versus 58 (IQR 35 to 81) in the CO UKA (p = 0.031). Discharge dispositions were comparable between the two groups. A higher percentage of patients undergoing CO TKA required PACU admission (8% vs 5.2%; p = 0.040). Conclusion. Our study showed that robotic arm assistance was associated with a shorter LOS in patients undergoing primary UKA and TKA, and no difference in the discharge destinations. Our results suggest that robotic arm assistance could be advantageous in partly addressing the upsurge of knee arthroplasty procedures and the concomitant healthcare burden; however, this needs to be corroborated by long-term cost-effectiveness analyses and data from randomized controlled studies. Cite this article: Bone Jt Open 2023;4(10):791–800

The purposes of this study were to evaluate the accuracy and feasibility of a robotic preparation for acetabular metal augments in patients with developmental dysplasia of the hip (DDH). Mako robotic arm reaming was used in 7 DDH to prepare the bony cavities for both Trident PSL cups and Tritanium acetabular wedge augments in six hips with Crowe 2 or 3 DDH. In CT-based planning, a properly sized cup was placed in the original acetabulum, and the same sized cup was also placed to fit the superolateral acetabular defect. The coordinates of the planned positions of cup and augment were recorded to manage the robotic arm reaming. After registration of the patient's pelvis, robotic reaming was performed first for the augment, then, for the cup by changing the target position of reaming as planned. The accuracy of the cup and augment placement was assessed on postoperative CT. To evaluate the feasibility of the robotic procedure, the OR time and blood loss were compared with those of 13 patients who received the same cup and augment systems with a conventional technique. All procedures were done without fracture or fixation failure. There were no differences in OR time or blood loss between the two procedures. Postoperative CT measurements of the distance between the cup center and the augment sphere center showed less than 2mm difference from the Mako preoperative planning. Although a longer time of follow up evaluation is mandatory, our robotic acetabular augment preparation technique is accurate and feasible

Introduction. Robotic-assisted hip arthroplasty helps acetabular preparation and implantation with the assistance of a robotic arm. A computed tomography (CT)-based navigation system is also helpful for acetabular preparation and implantation, however, there is no report to compare these methods. The purpose of this study is to compare the acetabular cup position between the assistance of the robotic arm and the CT-based navigation system in total hip arthroplasty for patients with osteoarthritis secondary to developmental dysplasia of the hip. Methods. We studied 31 hips of 28 patients who underwent the robotic-assisted hip arthroplasty (MAKO group) between August 2018 and March 2019 and 119 hips of 112 patients who received THA under CT-based navigation (CT-navi group) between September 2015 and November 2018. The preoperative diagnosis of all patients was osteoarthritis secondary to developmental dysplasia of the hip. They received the same cementless cup (Trident, Stryker). Robotic-assisted hip arthroplasty were performed by four surgeons while THA under CT-based navigation were performed by single senior surgeon. Target angle was 40 degree of radiological cup inclination (RI) and 15 degree of radiological cup anteversion (RA) in all patients. Propensity score matching was used to match the patients by gender, age, weight, height, BMI, and surgical approach in the two groups and 30 patients in each group were included in this study. Postoperative cup position was assessed using postoperative anterior-posterior pelvic radiograph by the Lewinnek's methods. The differences between target and postoperative cup position were investigated. Results. The acetabular cup position of all cases in both Mako and CT-navi group within Lewinnek's safe zone (RI: 40±10 degree; RA: 15±10 degree) in group were within this zone. Three was no significant difference of RI between Mako and CT-navi group (40.0 ± 2.1 degree vs 39.7± 3.6 degree). RA was 15.0 ± 1.2 degree and 17.0 ± 1.9 degree in MAKO group and in CT-navi group, respectively, with significant difference (p<0.001). The differences of RA between target and postoperative angle were smaller in MAKO group than CT-navi group (0.60± 1.05 degree vs 2.34± 1.40 degree, p<0.001). The difference or RI in MAKO group was smaller than in CT-navi, however, there was no significance between them (1.67± 1.27 degree vs 2.39± 2.68 degree, p=0.197). Conclusions. Both the assistance of the robotic arm and the CT-based navigation system were helpful to achieve the acetabular cup implantation, however, MAKO system achieved more accurate acetabular cup implantation than CT-based navigation system in total hip arthroplasty for the patients with OA secondary to DDH. Longer follow-up is necessary to investigate the clinical outcome

Introduction. Recent technological advancements have led to the introduction of robotic-assisted total knee arthroplasty to improve the accuracy and precision of bony resections and implant position. However, the in vivo accuracy is not widely reported. The primary objective of this study is to determine the accuracy and precision of a cut block positioning robotic arm. Method. Seventy-seven patients underwent total knee arthroplasty with various workflows and alignment targets by three arthroplasty-trained surgeons with previous experience using the ROSA® Knee System. Accuracy and precision were determined by measuring the difference between various workflow time points, including the final pre-operative plan, validated resection angle, and post-operative radiographs. The mean difference between the measurements determined accuracy, and the standard deviation represented precision. Results. The accuracy and precision for all angles comparing the final planned resection and validated resection angles was 0.90° ± 0.76°. The proportion within 3° ranged from 97.9% to 100%. The accuracy and precision for all angles comparing the final intra- operative plan and post-operative radiographs was 1.95 ± 1.48°. The proportion of patients within 3° was 93.2%, 95.3%, 96.6%, and 71.4% for the distal femur, proximal tibia, femoral flexion, and tibial slope angles when the final intra-operative plan was compared to post-operative radiographs. No patients had a postoperative complication requiring revision at the final follow-up. Conclusions. This study demonstrates that the ROSA Knee System has accurate and precise coronal plane resections with few outliers. However, the tibial slope demonstrated decreased accuracy and precision were measured on post-operative short-leg lateral radiographs with this platform

Introduction. Total knee arthroplasty (TKA) using conventional instrumentation has been shown to be a safe and effective way of treating end stage osteoarthritis by restoring function and alleviating pain. As robotic technology is developed to assist surgeons with intra-operative decision making such as joint balancing and component positioning, the safety of these advancements must be established. Furthermore, functional recovery and clinical outcomes should achieve comparable results to the gold standard of conventional instrumentation TKA. Methods. Eighty-seven subjects (89 knees) underwent robotic arm assisted TKA by one of three investigators as part of an FDA and IRB approved Investigational Device Exemption (IDE). To achieve the primary endpoint of intra-operative patient safety using a robotic arm assisted cutting tool, the investigators completed questionnaires to assess a series of complications related to soft tissue damage associated with conventional TKA. Western Ontario and McMaster Universities Arthritis Index (WOMAC) and Knee Society Knee Scores (KSS) were collected pre-operatively and at three month follow-up. Results. The average subject age was 65.8 ± 8.5 and the average BMI was 31.4 ± 5.7. 55% of the subjects were female. No subject experienced any of the rare intra-operative complications that comprise the primary safety endpoint. The average WOMAC score improvement from pre-operative to three months was 33.1 ± 20.04 (p<0.0001). The average KSS Knee score improvement was 46.1 ± 19.7 (p<0.0001). Subjects recovered their pre-operative range of motion by three months post-operative. Conclusion. Results from this prospective robotic arm assisted trial indicated greater intra-operative safety in blood loss and ligamentous damage when compared to conventional TKA. Subjects had excellent return to function and pain relief by three months as indicated by the KSS and WOMAC scores. Robotic technologies should be considered a safe and effective method in total joint restoration

INTRODUCTION. Adult reconstructive orthopedic surgery in the United States is facing an imminent logjam due to the increasing divergence of the demand for services and the ability for the community to supply those services. In combination with several other factors, a perfect storm is brewing that may leave the system overtaxed and the patient population suffering from either a lack of treatment, or treatment by less qualified providers. A key component to improving the overall efficiency of surgical care is to introduce enabling technologies that can effectively increase the throughput while simultaneously improving the quality of care. One such enabling technology that has proven itself in many industries is robotics, which has recently been introduced in surgery with even more recent applications in orthopedic surgery. A surgeon interactive robotic arm has been developed for partial knee arthroplasty (PKA) and total hip arthroplasty (THA). This study aims to analyse the efficiency of a new robotic technology for use in orthopaedic surgery. METHODS. 18 robotic arm assisted PKA's across 10 sites were recorded to accurately capture the timeline elemental tasks throughout the procedure. Two camera angles were set up to capture both surgical staff group dynamics and individual procedural steps. 17 tasks were identified and measured from video data. (Fig 1) The robotic arm specific tasks were analyzed for correlation to total surgical time (measured as first incision to last suture). The tasks for the surgeons with the shortest and longest total times were compared directly to determine areas of opportunity. RESULTS. Average total time across 18 surgeries was 55 ± 19 min (range: 30–98 min). There was no correlation between bone registration time and total time (p=0.271) and no correlation between femoral burring time and total time (p=0.230). Per task time comparison of the two surgeons exhibited an average time variation of 3.5 min per task (range: 0.7–8.4 min) (Fig 2). The robotic elements of the procedure exhibited an average time variation of 3.3 min per task while the non robotic elements of the procedure (boxed) exhibited an average time variation of 3.8 min per task. CONCLUSION. Our preliminary results indicate that introducing robotic technology in to the OR does not directly lead to an increase in total surgical time. On average, non robotic specific elements of the procedure exhibited a larger opportunity for efficiency gain. This is likely due to the fact that a large population of surgeon users are not only new to the robotic technology, but new to PKA. Further video collection and analysis will lead to an efficiency benchmarking program that aims to establish methods for best practices in achieving efficiency throughout a robotic arm assisted PKA procedure

With the approval of our institute, we reviewed all the robot-assisted hip revision during October 2019 and August 2021. MAKO joint arthroplasty system was used to perform the hip revision surgery. Seventy-one robot-assisted hip revision cases were included. Cup revisions were carried out in 68 patients while stem revisions were also carried out in 68 patients. Three types of registration techniques (extra acetabular bone surface based, liner based, metal shell based or cage surface based) on the acetabular side. The extra acetabular bone surface was the commonest used for registration (48/70, 68.6%, mean accuracy 0.37mm), followed by liner surface (11/70, 15.7%, mean accuracy 0.36mm), acetabulum cup (10/70, 14.3%, mean accuracy 0.37mm), and cage surface (1/70, 1.4%, accuracy 0.40mm). We succeeded cup registration and robotic arm guided cup insertion in all the cases. The average cup inclination and anteversion after revision were 40.87°±4.39° and 13.87°±4.24°, respectively. Cups in 62 cases (62/68, 91.2%) were within the Lewinnek safe zone while in 55 cases (55/68, 80.9%) were within the Callanan safe zone. The Mako robot-assisted system could bring favorable cup reconstruction in hip revision with acceptable surgical time and blood loss. Accurate registration could be achieved by different methods

Abstract. Objectives. Dual mobility (DM) hip implants whereby the polyethylene liner is “free-floating” are being used increasingly clinically. The motion of the liner is not well understood and this may provide insight into failure mechanisms; however, there are no published methods on tracking liner motion while testing under clinically relevant conditions. The aim was to develop and evaluate a bespoke inertial tracking system for DM implants that could operate submerged in lubricant without line-of-sight and provide 3D orientation information. Methods. Trackers (n=5) adhered to DM liners were evaluated using a robotic arm and a six-degree of freedom anatomical hip simulator. Before each set of testing the onboard sensor suites were calibrated to account for steady-state and non-linearity errors. The trackers were subjected to ranges of motion from ±5° to ±25° and cycle frequencies from 0.35Hz to 1.25Hz and the outputs used to find the absolute error at the peak angle for each principle axis. In total each tracker was evaluated for ten unique motion profiles with each sequence lasting 60 cycles. Results. Across all test conditions the angular error was consistently less than 1.1 ± 1.8° (mean ± SD) per principle axis with no relationship found between range of motion or cycle frequency and measurement error. Rotations about the trackers X and Y axes produced more repeatable results with a maximum spread of 5.5°, where as rotations about Z spread by up to 10.1°. Conclusions. The results of this study show that a system for monitoring DM liner motion without line of sight is possible, going forward this will be used to determine the effects of different loading and kinematic conditions on liner motions in a hip simulator

INTRODUCTION. Total hip arthroplasty (THA) is regarded as one of the most successful surgeries in medicine. However, recent studies have revealed that ideal acetabular cup implantation is achieved less frequently than previously thought, as little as 50% of the time. It is well known that malalignment of the acetabular component in THA may result in dislocation, reduced range of motion, or accelerated wear. This study reports accuracy of a tactile robotic arm system to ream the acetabulum and impact an acetabulur cup compared to manual instrumentation. METHODS. 12 fresh frozen cadaveric acetabulae were pre-operatively CT scanned and 3D templating was used to plan the center of rotation, and anteversion and inclination of the cup. Each specimen received THA, six prepared manually and six prepared with robotic arm guidance. Tactile, visual, and auditory feedback was provided through robotic guidance as well as navigated guided reaming and cup impaction. The robotic guidance constrained orientation of instruments thus constraining anteversion, inclination, and center of rotation for reaming, trialing, and final cup impaction. Post-operative CT scans were taken of each specimen to determine final cup placement for comparison to the pre-operative plans. RESULTS. In all cases, robotic arm guidance resulted in ±4° of anteversion and ±5° of inclination each relative to the pre-operative plan. Absolute RMS errors were 2.16 ± 1.35° for anteversion and 1.91 ± 1.55° for inclination. Cup placement with robotic guidance was significantly more accurate and precise than placement with manual instruments. With manual instrumentation the errors were, on average, 4.0 times higher in anteversion and 5.9 times higher in inclination compared to robotic instrumentation. CONCLUSION. This tactile robotic system substantially improved the accuracy of acetabular reaming and placement of the final cup compared to traditional manual techniques. With greater knowledge of ideal acetabular cup position, highly accurate techniques may allow surgeons to decrease the risk of dislocation, promote durability and improve the ability to restore appropriate leg length and offset. Tactile robotics has proven to be safe and effective in both knee and hip surgery and provides the potential to redefine the “instrument set” used for orthopedic procedures

Introduction. We report 10-year clinical outcomes of a prospective randomised controlled study on uni-compartmental knee arthroplasty using an active constraint robot. Measuring the clinical impact of CAOS systems has generally been based around surrogate radiological measures with currently few long-term functional follow-up studies reported. We present 10 year clinical follow up results of robotic vs conventional surgery in UKA. Material and methods. The initial study took place in 2004 and included 28 patients, 13 in the robotic arm and 15 in the conventional arm. All patients underwent medial compartment UKA using the ‘OXFORD’ mobile bearing knee system. Clinical outcome at 10 years was scored using the WOMAC scoring system. Results. 13 patients were initially included in the robotic arm, of these one was revised following trauma and a further two patient died leaving at total of 10 with an average age of 80 years. In the control arm, out of a total of 15 patients, 3 were revised to a total knee replacement due to pain, 1 has died and 1 lost to follow-up. Their mean age is 81. A total of 19 patients were included (conventional n=9, robotic n=10) in this follow up study. The WOMAC scores for the robotic group were lower - (p<0.05). Discussion. There is a paucity of data on 10 year outcome of computer assisted UKA and whilst most studies show no clinical benefit, our study suggests a better outcome, however our numbers now are small (n=19). In our original study 1 the primary outcome measure, tibiofemoral alignment in the coronal plane was within 2 degrees of the planned position in the robotic group whilst in the conventional group only 6 of the 15 knees achieved this level of accuracy - Fig 1. The primary hypothesis was that the use of an active constraint robot improved prosthetic position. This accuracy continues to be associated with improved functional outcome. Three revisions were performed prior to this period and were considered technical failures and have been excluded from this analysis

INTRODUCTION. Acetabular cup malpositioning has been implicated in instability and wear-related complications after total hip arthroplasty. Although computer navigation and robotic assistance have been shown to improve the precision of implant placement, most surgeons use mechanical and visual guides to place acetabular components. Authors have shown that, when using a bean bag positioner, mechanical guides are misleading as they are unable to account for the variability in pelvic orientation during positioning and surgery. However, more rigid patient positioning devices may allow for more accurate free hand cup placement. To our knowledge, no study has assessed the ability of rigid devices to afford surgeons with ideal pelvic positioning throughout surgery. The purpose of this study is to utilize robotic-arm assisted computer navigation to assess the reliability of pelvic position in total hip arthroplasty performed on patients positioned with rigid positioning devices. METHODS. 100 hips (94 patients) prospectively underwent total hip Makoplasty in the lateral decubitus position from the posterior approach; 77 stabilized by universal lateral positioner, and 23 by peg board. After dislocation but prior to reaming, one fellowship trained arthroplasty surgeon manually placed the robotic arm parallel to both the longitudinal axis of the patient and the horizontal surface of the operating table, which, if the pelvis were oriented perfectly, would represent 0 degrees of anteversion and 0 degrees of inclination. The CT-templated computer software then generated true values of this perceived zero degrees of anteversion and inclination based on the position of the robot arm registered to a preoperative pelvic CT. Therefore, variations in pelvic positioning are represented by these robotic navigation generated values. To assure the accuracy of robotic measurements, cup anteversion and inclination at times of impaction were recorded and compared to those calculated via the trigonometric ellipse method of Lewinnek on standardized 3 months postoperative X-rays. RESULTS. Mean alteration in anteversion and inclination values were 1.7 degrees (absolute value 5.3 degrees, range −20 – 20 degrees) and 1.6 degrees (absolute value 2.6 degrees, range −8 – 10 degrees) respectively. 22% of anteversion values were altered by >10 degrees; 41% by > 5 degrees. There was no difference between positioners (p=0.36) and regression analysis revealed that anteversion differences were correlated with BMI (p=0.02). Robotic navigation acetabular cup anteversion (mean 21.8 degrees) was not different from postoperative X-ray anteversion (mean 21.9 degrees)(p=0.50), nor was robotic navigation acetabular cup inclination (mean 40.6 degrees) different from postoperative X-ray inclination (mean 40.5 degrees)(p=0.34). DISCUSSION AND CONCLUSION. Rigid pelvic positioning devices present 5 to 20 degrees of variability in acetabular cup orientation, particularly with regards to anteversion. Compounding this with 20 degree safe zones and prior author demonstrations that human error is prone to 10 degrees of anteversion inaccuracy in a fixed pelvis model, there is a clear need to pay particular attention to anatomic landmarks or computer assisted techniques to assure accurate acetabular cup positioning. Patient positioning by itself should not be trusted

This paper illustrates the concept of a versatile surgical assistance system which combines an optical navigation system and a robotic arm. The integrated system offers precise positioning and guiding of surgical instruments according to pre-operative planning. A unique feature results from its capability to track small motions of the patient in real time, eliminating the need to rigidly fix the anatomical structure to be operated. The modular system architecture facilitates the adaptation of a common basic hardware platform to various surgical applications by adding associated software modules as well as appropriate surgical tools mounted to the robotic arm. The arm can be regarded as a controlled machine actuator of a navigation system. Its operation is mainly controlled by interactive operating modes which are based on a versatile haptic interface. The system supports the surgeon in those parts of a procedure where human skills are limited, but always lets him take full control, for example by directly grasping and moving the arm at its wrist if he wants to push the arm aside

Fluid film lubricating ability of a total hip prosthesis depends on the profile accuracies including surface-roughness or the sphericity of a head or a cup. Therefore, surface polishing is important. It was, however, difficult to polish the central portion of a cup or head using the conventional rotating machine. In the present study, we developed a polishing method combining a pendulum machine and a robotic arm. The effect of the accuracy improvement by this method was evaluated by the friction measurements on some test specimens. Nine balls and a cup of Co-Cr-Mo alloy that were polished by a conventional process using a rotating machine were prepared for the prototype. The average diameter of the balls was 31.9648 mm with the sphericity of 0.0028 μm. The inside diameter of the cup was 31.9850 mm with the sphericity of 0.0044 μm. We combined a robotic arm and a pendulum apparatus to enable the further polishing. The ability of both automatic centering and change in the sliding direction was accomplished by this system. The sliding direction has been changed 180 times every ten degrees. The total distance of polishing was 120 m under vertical load of 100 N in a bath of saline solution containing abrasive grains of silicate of the diameter of 2μm. The surface roughness of the central portion of the cup, which is important area for the fluid film lubrication decreased from Ra 20.2 μm before the polishing to Ra 18.7 μm after the polishing. A pendulum type friction tester was used for the assessment of the improvement of the lubricating ability by the polishing. The measurement was run over at 10 times under the conditions of the load of 600 N in a bath of saline solution. As the result, the frictional coefficients decreased from 0.1456–0.1720 before polishing to 0.1250–0.1300 after polishing. The polishing effect was, however, observed only at the specimens that radial clearances did not exceed the value of 50 μm. The present results indicated that the surface polishing of the central portion of hip prostheses must improve the lubrication ability and the radial clearance before the finishing process should be chinked as possible

Introduction. Background: Trochanteric bursitis is a common and poorly understood complication following total hip arthroplasty (THA). The purpose of this study was to evaluate the incidence of symptomatic trochanteric bursitis and the change in hip offset among THA patients before and after the introduction of robotic assistance. Methods. Retrospective chart review of THAs performed by a single over a 3-year period between 1/5/2013 and 6/28/2016. Between 1/5/2013 and 11/11/2014 101 consecutive patients were identified that underwent manual posterior-lateral THA that utilized traditional cup positioning method based on AP Pelvis radiograph. The subsequent six-month period during a complete transition to robotic arm assistance for posterior-lateral THA was excluded to eliminate any learning curve or selection bias. Between 6/2015 and 6/2016 109 consecutive patients that underwent robotic arm-assisted. Medical records were reviewed for symptomatic trochanteric bursitis within two years of surgery. Hip offset was measured on preoperative and postoperative AP pelvis radiographs and postoperative joint reactive forces were calculated using Martell's Hip Analysis Suite. Results. The rate of symptomatic trochanteric bursitis was 21% in the manual THA population and 10.4% in the population of THAs performed with robotic assistance (P=0.02). The post-operative change in hip offset was significantly higher in patients undergoing traditional THA than patients undergoing robotic arm-assisted THA (5.95 mm vs 4.40 mm; p = 0.0071). Discussion/Conclusion. Transition to robotic arm-assisted THA was associated with decreased incidence of symptomatic trochanteric bursitis and a decreased post-operative change in hip offset

There is an increasing prevalence of haptic devices in many engineering fields, especially in medicine and specifically in surgery. The stereotactic haptic boundaries used in Computer Aided Orthopaedic Surgery Unicomparmental Knee Arthroplasty (CAOS UKA) systems for assistive milling control can lead to an increase in the force required to manipulate the device; this study presented here has seen a several fold increase in peak forces between haptic and non-haptic conditions of a semi-active preoperative image system. Orthopaedic Arthroplasty surgeons are required to apply forces ranging from large gripping forces to small forces for delicate manipulation of tools and through a large range of postures. There is also a need for surgeons to move around and position themselves to gain line of sight with the object of interest and to operate while wearing additional clothing such as the protective headwear and double gloves. These factors further complicate comparison with other ergonomic studies of other robotics systems. While robotics has been implemented to reduce fatigue in surgery one area of concern in CAOS is localised user muscle fatigue in high volume use. In order to create the conditions necessary for the generation of fatigue in a realistic user experience, but in the time available for the participants, an extended period of controlled and prolonged cutting and manipulation of the robotic arm was needed. This pragmatic test requirement makes the test conditions slightly artificial but does indicate areas of high potential for fatigue when interacting with the system in high volume instances. The surgeon-robotic system interaction was captured using 3 dimensional motion analysis and a force transducer embedded in the end effector of the robotic arm and modelled using an existing upper body model in Anybody software. The kinematic and force information allowed initial calculations of the interaction between the user and the Robotic system. Validation of the model was conducted using Electromyography assessment of activity and fatigue. Optimisation of the model sought to create an efficient cutting regime to reduce cutting time with reduced muscle force in an attempt to reduce users discomfort/fatigue while taking into account anthropometric variations in the users and minimising overall energy requirements, burr path length and maximum muscle force. From the assessment of a small group of three surgeons with experience of the Robotic system there was little to no experience of above normal localised fatigue during small volume use of the system. Observation of these surgeons operating the robot state otherwise with examples of reactions to discomfort. There is also anecdotal evidence that fatigue becomes more problematic in higher volume work loads

INTRODUCTION. we have previously reported that bone preparation is quite precise and accurate relative to a preoperative plan when using a robotic arm assisted technique for UKA. However, in that same study, we found a large variation between intended and final tibial implant position, presumably occuring during cement curing. In this study, we reviewed a subsequent cohort of patients in which the tibial and femoral components were cemented individually with ongoing evaluation of tibial component position during cement curing. METHODS AND MATERIALS. Group 1 comprised the simultaneous cementing techniquegroup of patients, previously reported on, although their x-rays were re-analyzed. Group 2 consisted of the individual cementing technique cohort. All implants were identical, specifically a flat, inlay all-polyethylene tibial component. Postoperative x-rays from each cohort of patients were evaluated using image analysis software. Statistical evaluation was performed. RESULTS. In Group 1, average bone preparation was 5.13 + 2.70 degrees of varus and 7.40 + 2.59 degrees of posterior slope. Final implant position was 3.56 + 1.93 degrees of varus and 5.19 + 3.37 degrees of slope. The variance from intended position was 2.31 + 1.74 degrees of varus and 3.80 + 2.90 degrees of slope. For Group 2, average bone preparation was 5.26 + 3.70 degrees of varus and 5.49+ 2.39 degrees of posterior slope. Final implant position was 6.58 + 3.40 degrees of varus and 6.11 + 2.39 degrees of slope. The variance from intended position was 1.82 + 1.42 degrees of varus and 1.39 + 1.48 degrees of slope. ANOVA revealed no differences between groups regarding bone prep in the coronal plane, final implant slope, or variation from intended coronal position. However, bone prep in the sagittal plane showed statistically significant more slope for Group 1 (p = 0.03), increased slope in Group 2 (p=0.004), and greater variation from intended sagital position for Group 1. CONCLUSIONS. Independent cementing of implants showed decreased variation in final tibial component position. However, some implants showed up to 6 degrees of malposition from the intended position. We believe this to be a shortcoming of the inlay style of tibial component for UKA, which even cannot be overcome with the precision and accuracy of a robotic arm assistant

The paper presents the design of a mechatronic assistance system which started from the novel concept to integrate an optical navigation system and a robotic arm, combining the specific advantages of each of the two components. The integrated system offers precise positioning and guiding of surgical instruments according to pre-operative planning. A unique feature results from its capability to track small motions of the patient in real time, eliminating the need to rigidly fix the anatomical structure to be operated. The robot arm can be regarded as a controlled machine actuator of a navigation system. Its operation is mainly controlled by interactive operating modes which are based on a versatile haptic interface. The system supports the surgeon in those parts of a procedure where human skills are limited, but always lets him take full control, for example by directly grasping and moving the arm at its wrist if he wants to push the arm aside. In 2003 several clinical trials have been performed to demonstrate the technical and medical feasibility of the approach. Our mechatronic assistance system has been world’s first system to support the implantation of the acetabular cup in robot assisted hip surgery. The next steps have been concentrated on further developments in some key areas. Improvements of the man-machine interface in order to make the operation of the system faster, easier, and more robust, extension of the system application also to the femoral part of total hip replacement, including support for resurfacing implants, investigation of novel tool systems for bone preparation and prosthesis implantation that fully exploit the advantages of mechatronic, slip-away-safe tool guidance, further improvements for less invasive operating techniques. It has turned out that apart from proving the basic system functionality it is a time consuming task to design all system components in a way that they are robust and easy to handle to be acceptable for daily clinical application. After a partial redesign of the system architecture presently the implementation of improved modules to support both the acetabular and the femoral part in total hip replacement surgery by the mechatronic assistance system is in progress

Background. Use of a robotic tool to perform surgery introduces a risk of unexpected soft tissue damage due to the uncommon tactile feedback for the surgeon. Early experience with robotics in total hip and knee replacement surgery reported having to abort the procedure in 18–34 percent of cases due to inability to complete preoperative planning, hardware and soft tissue issues, registration issues, as well as concerns over actual and potential soft tissue damage. These can result in significant morbidity to the patient, negating all the desired advantages of precision and reproducibility with robotic assisted surgery. The risk of soft tissue damage can be mitigated by haptic software prohibiting the cutting tip from striking vital soft tissues and by the surgeon making sure there is a clear workspace path for the cutting tool. This robotic total knee system with a semi-active haptic guided technique was approved by the FDA on 8/5/2015 and commercialized in August of 2016. Two year clinical results have not been reported to date. Objective. To review an initial and consecutive series of robotic total knee arthroplasties for safety in regard to avoidance of known or delayed soft tissue injuries and the necessity to abort the using the robot to complete the procedure. Report the clinical outcomes with robotic total knee replacement at or beyond two years to demonstrate no delayed effect on expected outcome. Methods. The initial consecutive series of 65 Triathlon. TM. total knee replacements using a semi-active haptic guided system that were performed after commercialization that would be eligible for two year follow-up were reviewed. Pre-operative planning utilizing CT determined the implant placement and boundaries and thus the limit of excursion from any part of the end effector saw tip. Self-retaining retractors were also utilized. Operative reports, 2, 6, and 12 week, and yearly follow-up visit reports were reviewed for any evidence of inadvertent injury to the medial collateral ligament, patellar tendon, or a neurovascular structure from the cutting tool. Operative notes were also reviewed to determine if the robotic procedure was partially or completely aborted due to any issue. Knee Society Knee Scores (KS-KS) and Functional Scores (KS-FS) were recorded from pre-operative and yearly. Any complications were recorded. Results. 40 cases had two year follow-up. The average follow-up for this series was 1.51 years. No cases were unable to be completed robotically. No case had evidence for acute or delayed injury to the medial collateral ligament, patellar tendon, or neurovascular structure. The only complication was a revision total knee for tibial component loosening after a fall induced periprosthetic tibial fracture. Average pre-operative KS-KS and KS-FS improved from 46.9 and 52.1 to 99.2 and 88.6 at one year follow-up, 100.5 and 86.9 at two year follow-up. Conclusions. A semi-active haptic guided robotic system is a safe and reliable method to perform total knee replacement surgery. This series of initial robotic arm assisted surgery had no intraoperative or delayed soft tissue injuries. Preliminary short-term outcomes at up to two years show excellent outcomes