Introduction. Unicondylar knee replacement (UKR) surgery is proven long term results in its benefit in medial compartment OA. However, its results are sensitive to component alignment with poor alignment leading to early failure. The advent of computer navigation has resulted in improved mechanical alignment, but little has been published on the outcomes of navigated UKR surgery. We present the results of 253 consecutive Computer Assisted UKR's performed by a single surgeon. Objective. Assess clinical and radiological outcomes of Computer Assisted Unicondylar Knee Replacement at 5 years follow-up. Methods. Between August 2003 and June 2007, 253 UKR's were performed by a single surgeon using the Stryker Knee navigation system. Pre-operative Knee Society Scores (KSS) were recorded. The UKR's consisted of 98 oxford UKR's and 155 MG UKR's. Tourniquet time, time to straight leg raise and time to discharge was also recorded. All patients had post op KSS scores and long leg standing radiographs. Data regarding revision surgery was also collected. Results. Pre-op mean KSS scores was 54 (24–62) and post-op scores were a mean of 89 (75–100). 92% percent of femoral components were aligned at 90+/− 4 degrees from neutral in the coronal plane whilst eighty nine percent of tibial components were aligned at 90+/− 4 degrees from neutral in the coronal plane. Mean tourniquet time was 53 minutes whilst 98% of patients had SLR at 24hours. Only two percent of patients had an overall valgus alignment of their limb at the end of the procedure on long leg radiographs. 1% of the UKRs underwent revision for loosening of the femoral component. 1 oxford UKR was revised for progression of patello-femoral disease. One MG UKR was revised for unexplained pain. Conclusion. Our single surgeon series of Computer Assisted UKR demonstrates favourable outcomes in the medium term with 98% survival at 5 years. Computer Assisted UKR allows accurate and reproducible alignment of the tibial and femoral component. We recommend the use of Computer Navigation in performing Unicondylar Knee Replacements

Utilisation of unicondylar knee arthroplasty (UKA) has been limited due in part to high revision rates. Only 8% of knee arthroplasty surgeries completed in England and Wales are UKAs. It is reported that the revision rate at 9 years for Total Knee Arthroplasty (TKA) was 3% compared to 12% for UKAs. In the last decade semi active robots have been developed to be used for UKA procedures. These systems allow the surgeon to plan the size and orientation of the tibial and femoral component to match the patient's specific anatomy and to optimise the balancing the soft tissue of the joint. The robotic assistive devices allow the surgeon to execute their plan accurately removing only ‘planned’ bone from the predefined area. This study investigates the accuracy of an imageless navigation system with robotic control for UKA, reporting the errors between the ‘planned’ limb and component alignment with the post-operative limb and component alignment using weight bearing long leg radiographs. We prospectively collected radiographic data on 92 patients who received medial UKA using an imageless robotic assisted device across 4 centres (4 surgeons). This system is CT free, so relies on accurate registration of intra-operative knee kinematic and anatomic landmarks to determine the mechanical and rotational axis systems of the lower limb. The surface of the condylar is based on a virtual model of the knee created intra-operatively by ‘painting’ the surface with the tip of a tracked, calibrated probe. The burring mechanism is robotically controlled to prepare the bone surface and remove the predefined volume of bone. The study shows the 89% of the patients' post-operative alignment recorded by the system was within 30 of the planned coronal mechanical axis alignment. The RMS error was 1.980. The RMS errors between the robotic system's implant plan and the post-operative radiographic implant position was; femoral coronal alignment (FCA) 2.6o, tibial coronal alignment (TCA) 2.9o and tibial slope (TS) 2.9o. In conclusion, the imageless robotic surgical system for UKA accurately prepared the bone surface of the tibia and femur which resulted in low errors when comparing planned and achieved component placement. This resulted in a high level of accuracy in the planned coronal mechanical axis alignment compared to that measured on post-operative radiographs

For patients suffering from osteoarthritis confined to one compartment of the knee joint, a successful unicondylar knee arthroplasty (UKA) has demonstrated an ability to provide pain relief and restore function while preserving bone and cruciate ligaments that a total knee arthroplasty (TKA) would sacrifice. Long-term survival of UKA has traditionally been inconsistent, leading to decreased utilisation in favour of alternative surgical treatment. Robot-assisted UKA has demonstrated an ability to provide more consistent implantation of UKA prosthesis, with the potential to increase long-term survivorship. This study reports on 65 patients undergoing UKA using an image-free, handheld robotic assistive navigation system. The condylar surface was mapped by the surgeon intra-operatively using a probe to capture a 3-dimensional representation of the area of the knee joint to be replaced. The intra operative planning phase allows the surgeon to determine the size and orientation of the femoral and tibial implant to suit the patients’ anatomy. The plan sets the boundaries of the bone to be removed by the robotic hand piece. The system dynamically adjusts the depth of bone being cut by the bur to achieve the desired result. The planned mechanical axis alignment was compared with the system's post-surgical alignment and to post-operative mechanical axis alignment using long leg, double stance, weight bearing radiographs. All 65 knees had knee osteoarthritis confined to the medial compartment and UKA procedures were completed using the handheld robotic assistive navigation system. The average age and BMI of the patient group was 63 years (range 45–82 years) and 29 kg/m. 2. (range 21–37 kg/m. 2. ) respectively. The average pre-operative deformity was 4.5° (SD 2.9°, Range 0–12° varus). The average post-operative mechanical axis deformity was corrected to 2.1° (range 0–7° varus). The post-operative mechanical axis alignment in the coronal plane measured by the system was within 1° of intra-operative plan in 91% of the cases. 3 out of 6 of the cases where the post-operative alignment was greater than 1° resulted due to an increase in the thickness of the tibia prosthesis implanted. The average difference between the ‘planned’ mechanical axis alignment and the post-operative long leg, weight bearing mechanical axis alignment was 1.8°. The average Oxford Knee Score (old version) pre and post operation was 38 and 24 respectively, showing a clinical and functional improvement in the patient group at 6 weeks post-surgery. The surgical system allowed the surgeons to precisely plan a UKA and then accurately execute their intra operative plan using a hand held robotically assisted tool. It is accepted that navigation and robotic systems have a system error of about 1° and 1mm. Therefore, this novel device recorded accurate post-operative alignment compared to the ‘planned’ post-operative alignment. The patients in this group have shown clinical and functional improvement in the short term follow up. The importance of precision of component alignments while balancing existing soft-tissue structures in UKA has been documented. Utilisation of robotic-assisted devices may improve the accuracy and long-term survivorship UKA procedure

Unicondylar knee arthroplasty (UKA) is a treatment for osteoarthritis when the disease only affects one compartment of the knee joint. The popularity in UKA grew in the 1980s but due to high revision rates the usage decreased. A high incidence of implant malalignment has been reported when using manual instrumentation. Recent developments include surgical robotics systems with navigation which have the potential to improve the accuracy and precision of UKA. UKA was carried out using an imageless navigation system – the Navio Precision Freehand Sculpting system (Blue Belt Technologies, Pittsburgh, USA) with a medical Uni Knee Tornier implant (Tornier, Montbonnot Saint Martin, France) on nine fresh frozen cadaveric lower limbs (8 males, 1 females, mean age 71.7 (SD 13.3)). Two users (consultant orthopaedic surgeon and post doctoral research associate) who had been trained on the system prior to the cadaveric study carried out 4 and 5 implants respectively. The aim of this study was to quantify the differences between the planned and achieved cuts. A 3D image of the ‘actual’ implant position was overlaid on the planned implant image. The errors between the ‘actual’ and the planned implant placement were calculated in three planes and the three rotations. The maximum femoral implant rotational error was 3.7° with a maximum RMS angular error of 2°. The maximum femoral implant translational error was 2.6mm and the RMS translational error across all directions was up to 1.1mm. The maximum tibial implant rotational error was 4.1° with a maximum RMS angular error was 2.6°. The maximum translational error was 2.7mm and the RMS translational error across all directions was up to 2.0mm. The results were comparable to those reported by other robotic assistive devices on the market for UKA. This technology still needs clinical assessment to confirm these promising results

NavioPFS™ is a hand-held robotic technology for bone shaping that employs computer control of a high-speed bone drill. There are two control modes – one based on control of exposure of the cutting bur and another based on the control of the speed of the cutting bur. The unicondylar knee replacement (UKR) application uses the image-free approach in which a mix of direct and kinematic referencing is used to define all parameters relevant for planning. After the bone cutting plan is generated, the user freely moves the NavioPFS handpiece over the bone surface, and carves out the parts of the bone targeted for removal. The real-time control loop controls the depth or speed of cut, thus resulting in the planned bone preparation. This experiment evaluates the accuracy of bone preparation and implant placement on cadaveric knees in a simulated clinical setting. Three operators performed medial UKR on two cadaver specimens (4 knees) using a proprietary implant design that takes advantage of the NavioPFS approach. In order to measure the placement of components, each component included a set of 8 conical divots in predetermined locations. To establish a shared reference frame, a set of four fiducial screws is inserted in each bone. All bones were cut using a 5 mm spherical bur. Exposure Control was the primary mode of operation for both condylar cuts – although the users utilised Speed Control to perform some of the more posterior burring activities and to prepare the peg holes. Postoperatively, positions of conical divots on the femoral and tibial implants and on the respective four fiducial screws were measured using a Microscribe digitising arm in order to compare the final and the planned implant position. All implants were placed within 1.5 mm of target position in any particular direction. Maximum translation error was 1.31 mm. Maximum rotational error was 1.90 degrees on a femoral and 3.26 degrees on a tibial component. RMS error over all components was 0.69mm/1.23 degrees. This is the first report of the performance of the NavioPFS system under clinical conditions. Although preliminary, the results are overall in accordance with previous sawbones studies and with the reports from comparable semi-active robotic systems that use real time control loop to control the cutting performance. The use of NavioPFS in UKR eliminates the need for conventional instrumentation and allows access to the bone through a reduced incision. By leveraging the surgeon's skill in manipulating soft tissues and actively optimising the tool's access to the bone, combined with the precision and reproducibility of the robotic control of bone cutting, we expect to make UKR surgery available to a wider patient population with isolated medial osteoarthritis that might otherwise receive a total knee replacement. In addition to accurate bone shaping with a handheld robotically controlled tool, NavioPFS system for UKR incorporates a CT-free planning system. This approach combines the practical advantages of not requiring pre-operative medical images, while still accurately gathering all key information, both geometric and kinematic, necessary for UKR planning

Knee osteoarthritis results in pain and functional limitations. In cases where the arthritis is limited to one compartment of the knee joint then a unicondylar knee arthroplasty (UKA) is successful, bone preserving option. UKA have been shown to result in superior clinical and functional outcomes compared to TKA patients. However, utilisation of this procedure has been limited due primarily to the high revision rates reported in joint registers. Robotic assisted devices have recently been introduced to the market for use in UKA. They have limited follow up periods but have reported good implant accuracy when compared to the pre-operative planned implant placement. UKA was completed on 25 cadaver specimens (hip to toe) using an image-free approach with infrared optical navigation system with a hand held robotically assisted cutting tool. Therefore, no CT scan or MRI was required. The surface of the condylar was mapped intra operatively using a probe to record the 3 dimensional surface of the area of the knee joint to be resurfaced. Based on this data the size and orientation of the implant was planned. The user was able to rotate and translate the implant in all three planes. The system also displays the predicted gap balance graph through flexion as well as the predicted contact points on the femoral and tibial component through flexion. The required bone was removed using a bur. The depth of the cut was controlled by the robotically controlled freehand sculpting tool. Four users (3 consultant orthopaedic surgeon and a post-doctoral research associate) who had been trained on the system prior to the cadaveric study carried out the procedures. The aim of this study was to quantify the differences between the ‘planned’ and ‘achieved’ cuts. A 3D image of the ‘actual’ implant position was overlaid on the ‘planned’ implant image. The errors between the ‘actual’ and the ‘planned’ implant placement were calculated in three planes and the three rotations. The maximum femoral RMS angular error was 2.34°. The maximum femoral RMS translational error across all directions was up to 1.61mm. The maximum tibial RMS angular error was 2.60°. The maximum tibial RMS translational error across all directions was up to 1.67mm. In conclusion, the results of this cadaver study reported low RMS errors in implant position placement compared to the plan. The results were comparable with those published from clinical studies investigating other robotic orthopaedic devices. Therefore, the freehand sculpting tool was shown to be a reliable tool for cutting bone in UKA and the system allows the surgeon to plan the placement of the implant intra operatively and then execute the plan successfully

Unicondylar knee arthroplasty (UKA) is growing in popularity with an increase in utilisation. As a less invasive, bone preserving procedure suitable for knee osteoarthritic patients with intact cruciate ligaments and disease confined to one compartment of the knee joint. The long term survival of a UKA is dependent on many factors, including the accuracy of prosthesis implantation and soft tissue balance. Robotic assisted procedures are generally technically demanding, can increase the operation time and are associated with a learning curve. The learning curve for new technology is likely to be influenced by previous experience with similar technologies, the frequency of use and general experience performing the particular procedure. The purpose of this study was to determine the time to achievement of a steady state with regards to surgical time amongst surgeons using a novel hand held robotic device. This study examined consecutive UKA cases which used a robotic assistive device from five surgeons. The surgeons had each performed at least 15 surgeries each. Two of the surgeons had previous experience with another robotic assistive device for UKA. All of the surgeons had experience with conventional UKA. All of the surgeons have used navigation for other knee procedures within their hospital. The system uses image free navigation with infrared optical tracking with real time feedback. The handheld robotic assistive system for UKA is designed to enable precision of robotics in the hands of the surgeon. The number of surgeries required to reach ‘steady state’ surgical time was calculated as the point in which two consecutive cases were completed within the 95% confidence interval of the surgeon's ‘steady state’ time. The average surgical time (tracker placement to implant trial acceptance phase) from all surgeons across their first 15 cases was 56.8 minutes (surgical time range: 27–102 minutes). The average improvement was 46 minutes from slowest to quickest surgical times. The ‘cutting’ phase was reported as decreasing on average by 31 minutes. This clearly indicates the presence of a learning curve. The surgeons recorded a significant decrease in their surgical time where the most improvement was in the process of bone cutting (as opposed to landmark registration, condyle mapping and other preliminary or planning steps). There was a trend towards decreasing surgical time as case numbers increase for the group of five surgeons. On average it took 8 procedures (range 5–11) to reach a steady state surgical time. The average steady state surgical time was 50 minutes (range 37–55 minutes). In conclusion, the average operative time was comparable with clinical cases reported using other robotic assistive devices for UKA. All five surgeons using the novel handheld robotic-assisted orthopaedic system for UKA reported significant improvement in bone preparation and overall operative times within the first 15 cases performed, reaching a steady state in surgical times after a mean of 8 cases. Therefore, this novel handheld device has a similar learning curve to other devices on the market

Lower limb alignment after unicondylar knee arthroplasty (UKA) has a significant impact on surgical outcomes. The literature lacks studies that evaluate the limb alignment after lateral UKA or compare it to alignment outcomes after medial UKA, making our understanding of this issue based on medial UKA studies. Unfortunately, since the geometry, mechanics, and ligamentous physiology are different between these two compartments, drawing conclusions for lateral UKAs based on medial UKA results may be imprecise and misleading. The purpose of this study was to compare the risk for limb alignment overcorrection and the ability to predict postoperative limb alignment between medial and lateral UKA. We evaluated the results of mechanical limb alignment in 241 patients with unicompartmental knee osteoarthritis who underwent medial or lateral UKA; there were 229 medial UKAs and 37 lateral UKAs. Mechanical limb alignment was measured in standing long limb radiographs pre and post-operatively, intra-operatively it was measured using a computer assisted navigation system. Between the two cohorts, we compared the percentage of overcorrection and the difference between post-operative alignment and alignment measured by the navigation system. The percentage of overcorrection was significantly higher in the lateral UKA group (11%), when compared to the medial UKA group (4%), (p= 0.0001). In the medial UKA group, the mean difference between the intraoperative “virtual” alignment provided by the navigation system, and the post-operative, radiographically measured mechanical axis, was 1.33°(±1.2°). This was significantly lower than the mean 1.86° (±1.33°) difference in the lateral UKA group (p=0.019). Our data demonstrated an increased risk of mechanical limb alignment overcorrection and greater difficulty in predicting postoperative alignment using computer navigation, when performing lateral UKAs compared to medial UKAs

Lower limb alignment after unicondylar knee arthroplasty (UKA) has a significant impact on surgical outcomes. The literature lacks studies that evaluate the limb alignment after lateral UKA or compare it to alignment outcomes after medial UKA, making our understanding of this issue based on medial UKA studies. Unfortunately, since the geometry, mechanics, and ligamentous physiology are different between these two compartments, drawing conclusions for lateral UKAs based on medial UKA results may be imprecise and misleading. The purpose of this study was to compare the risk for limb alignment overcorrection and the ability to predict postoperative limb alignment between medial and lateral UKA. We evaluated the results of mechanical limb alignment in 241 patients with unicompartmental knee osteoarthritis who underwent medial or lateral UKA; there were 229 medial UKAs and 37 lateral UKAs. Mechanical limb alignment was measured in standing long limb radiographs pre and post-operatively, intra-operatively it was measured using a computer assisted navigation system. Between the two cohorts, we compared the percentage of overcorrection and the difference between post-operative alignment and alignment measured by the navigation system. The percentage of overcorrection was significantly higher in the lateral UKA group (11%), when compared to the medial UKA group (4%), (p= 0.0001). In the medial UKA group, the mean difference between the intraoperative “virtual” alignment provided by the navigation system, and the post-operative, radiographically measured mechanical axis, was 1.33°(±1.2°). This was significantly lower than the mean 1.86° (±1.33°) difference in the lateral UKA group (p=0.019). Our data demonstrated an increased risk of mechanical limb alignment overcorrection and greater difficulty in predicting postoperative alignment using computer navigation, when performing lateral UKAs compared to medial UKAs

Introduction. Limb alignment after unicondylar knee arthroplasty (UKA) has a significant impact on surgical outcomes. The literature lacks studies that evaluate the limb alignment after lateral UKA or compare alignment outcomes between medial and lateral UKA. In this study, we retrospectively compare a single surgeon's alignment outcomes between medial and lateral UKA using a robotic-guided protocol. Methods. All surgeries were performed by a single surgeon using the same planning software and robotic guidance for execution of the surgical plan. The senior surgeon's prospective database was reviewed to identify patients who had 1) undergone medial or lateral UKA for unicompartmental osteoarthritis; and 2) had adequate pre- and post-operative full-length standing radiographs. There were 229 medial UKAs and 37 lateral UKAs in this study. Mechanical limb alignment was measured in standing long limb radiographs both pre- and post-operatively. Intra-operatively, limb alignment was measured using the computer assisted navigation system. The primary outcome was over-correction of the mechanical alignment (i.e, past neutral). Our secondary outcome was the difference between the radiographic post-operative alignment and the intra-operative “virtual” alignment as measured by the computer navigation system. This allowed an assessment of the accuracy of our navigation system for predicting post-operative limb alignment after UKA. Results. The percentage of overcorrection was significantly higher in the lateral UKA group (11%), when compared to the medial UKA group (4%), (p = 0.0001). In the medial UKA group, the mean difference between the intraoperative “virtual” alignment provided by the navigation system, and the post-operative, radiographically measured mechanical axis, was 1.33° (± 1.2°). This was significantly lower than the mean difference between these two parameters in the lateral UKA group, 1.86° (± 1.33°) (p = 0.019). Conclusions. Our data demonstrated an increased risk of “overcorrection,” and greater difficulty in predicting postoperative alignment using computer navigation, when performing lateral UKAs compared to medial UKAs

Background. Current analysis of unicondylar knee replacements (UKR) by national registries is based on the pooled results of medial and lateral implants. Using data from the National Joint Registry for England and Wales (NJR) we aimed to determine the proportion of lateral UKR implanted, their survival and reason for failure in comparison to medial UKR. Methods. By combining information on the side of operation with component details held on the NJR we were able to determine implant laterality (medial vs. lateral) for 32,847 of the 35,624 (92%) UKR registered before December 2010. Kaplan Meier plots, Life tables and Cox' proportion hazards were used to compare the risk of failure for lateral and medial UKRs after adjustment for patient and implant covariates. Results. 2,052 (6%) UKR were inserted on the lateral side of the knee. The rates of survival at 5 years were 93.1% (95%CI 92.7 to 93.5) for medial and 93.0% (95%CI 91.1% to 94.9%) for lateral replacements (p=0.49). The rates of failure remained equivalent after adjustment for patient age, gender, ASA grade, indication for surgery and implant type using Cox's proportional hazards (HR=0.87, 95%CI 0.68 to 1.10, p=0.24). For medial implants covariates found to influence the risk of failure were patient age (p< 0.001) and ASA grade (p=0.04). Age similarly influenced the risk of failure for lateral UKRs. Implant design (Mobile versus Fixed bearing) did not influence the risk of failure in either the medial or lateral compartment. Aseptic loosening/lysis and unexplained pain were the main reasons for revision in both groups. Conclusion. The mid-term survival of medial and lateral UKRs are equivalent. This supports the on-going use of pooled data by registries for the reporting on unicondylar outcomes in the future

Background. In a mobile-bearing unicondylar knee arthroplasty (UKA) stability is very important for the knee function and to prevent dislocation of the insert. A tension-guided technique to determine the position of the optimal posterior bone cut should theoretically lead to a better varus-valgus stability. The goal of this study was to measure the difference in valgus laxity in flexion and extension between a tension-guided and spacer-guided system for mobile-bearing UKA. Also clinical function was evaluated between the groups. Patients and Methods. A tension-guided UKA system (BalanSys. TM. , Mathys, Bettlach, Switzerland) was compared with a retrospective group of a spacer-guided system (Oxford, Biomet Ltd, Bridgend, UK). A total of 30 tension-guided UKAs were placed and compared to 35 spacer-guided prostheses. Valgus laxity was measured at least 6 months postoperatively in both groups using stress radiographs. The flexion stress radiographs were made fluoroscopically aided in 70 degrees of knee flexion. Laxity measurements in extension were performed on stress radiographs obtained with the Telos device. Knee Society Scores (KSS) were obtained at follow-up. Results. Valgus laxity in flexion was significantly higher in the tension-guided group compared to the spacer-guided group: 3.9° and 2.4°, respectively, p<0.001) In extension, valgus laxity was 1.8° in the tension-guided group compared to 2.7° in the spacer-guided group, which was significantly different (p<0.001). There was no significant difference between the two groups in the KSS at 6 months follow-up. (p=0.31). Discussion and conclusion. The tensor-guided system resulted in significantly more valgus laxity in flexion compared to the spacer-guided system. However, in extension the situation was reversed: the tension-guided system resulted in less valgus laxity than the spacer-guided system. Clinically, there were no differences between the groups. The valgus laxity found with the spacer-guided system better approximates the valgus laxity values of healthy elderly

Purpose. The purpose of this study was to examine the progression of osteoarthritis (OA) on patella-femoral joint (PFJ) after open wedge high tibial osteotomy (OWHTO) and unicondylar knee arthroplasty (UKA) in correlation with pain and functional outcomes. Methods. We conducted a retrospective analysis of 101 knees (89 patients), which received an OWHTO in 42 knees and UKA in 59 knees between 2003 and 2008 with minimum 5-years follow-up. Preoperative and the last follow-up radiologic evaluations were performed on the specific radiographic parameters that reflect the patella and knee alignment. Progressions of OA on PFJ at pre-operation and the last follow up were assessed and compared with modified OA grading system. The patella-femoral (PF) pain and function score were recorded using modified PF scoring system at the last follow up. Results. Among the radiologic parameters, mechanical axis (MA) and lateral patella tilt (LPT) showed statistically significant differences between OWHTO and UKA. Most of cases showed no progression or just only 1 grade step-up progression on PFJ in both groups and the amount of progression showed no statistical significant between OWHTO and UKA. In comparison of the preoperative and the final follow-up OA grades, medial PFJ in UKA group showed statistically significant differences. The PF pain and function score were comparable in both groups at the final follow up which showed no statistical differences regardless of OA progression. Conclusions. Overall, 40 ∼ 70% of cases did not occurred the progression of OA in PFJ after OWHTO and UKA. Additionally, at last follow up, the most cases showed the grade 0 or 1 OA in PFJ of both groups. Compared with HTO group, in UKA group, there were tendency of more progression of PFJ compared with preoperative OA status. Finally the degree of OA progressions did not affect the PF pain and functional outcomes

Introduction

With the introduction of minimally invasive surgery techniques and improved polyethylene wear properties, there has been a renewed interest in Unicondylar Knee Replacements (UKR). Customized, Individually Made (CIM) UKR have been in the market for some time, and have shown to provide improved coverage and fit. The purpose of this study was to assess clinical and patient-reported outcomes utilizing CIM-UKR prostheses.

Introduction:

Two fixed bearing options exist for tibial resurfacing when performing unicompartmental knee arthroplasty (UKA). Inlay components are polyethylene-only implants inserted into a carved pocket on the tibial surface, relying upon the subchondral bone to support the implant. Onlay components have a metal base plate and are placed on top of a flat tibial cut, supported by a rim of cortical bone. To our knowledge, there is no published report that compares the clinical outcomes of these two implants using a robotically controlled surgical technique. We performed a retrospective review of a single surgeon's experience with Inlay versus Onlay components, using a robotic-guided protocol.

Introduction

Historically, the outcomes of knee replacement were evaluated based on implant longevity, major complications and range of motion. Over the last recent years however, there has been an intensively growth of interest in the patient's perception of functional outcome. However, the currently used patient related outcome (PRO) scores are limited by ceiling effects which limit the possibility to distinguish between good and excellent results post knee arthroplasty. The Forgotten Joint Score (FJS) is a new PRO score which is not influenced by ceiling effects, therefore making it the ideal instrument to compare functional outcome between various types of implants. It is based on the thought that the ultimate goal in joint arthroplasty is the ability of a patient to forget their artificial joint in everyday life.

The aim of this study is to compare the FJS between patients who undergo TKA and patients who undergo medial UKA at least 12 months post-operatively. We hypothesized that the UKA which is less extensive surgical procedure will present better FJS than TKA, even 12 month postoperative.

Introduction. The purpose of this study was to characterize the recovery of physical activity following knee arthroplasty by means of step counts and flight counts (flights of stairs) measured using a smartphone-based care platform. Methods. This is a secondary data analysis on the treatment cohort of a multicenter prospective trial evaluating the use of a smartphone-based care platform for primary total and unicondylar joint arthroplasty. Participants in the treatment arm that underwent primary total or unicondylar knee arthroplasty and had at least 3 months of follow-up were included (n=367). Participants were provided the app with an associated smart watch for measuring several different health measures including daily step and flight counts. These measures were monitored preoperatively, and the following postoperative intervals were selected for review: 2–4 days, 1 month, 1.5 month, 3 months and 6 months. The data are presented as mean, standard deviation, median, and interquartile range (IQR). Signed rank tests were used to assess the difference in average of daily step counts over time. As not all patients reported having multiple stairs at home, a separate analysis was also performed on average flights of stairs (n=214). A sub-study was performed to evaluate patients who returned to preoperative levels at 1.5 months (step count) and 3 months (flight count) using an independent samples T test or Fisher's Exact test was to compare demographics between patients that returned to preoperative levels and those that did not. Results. The mean age of the step count population was 63.1 ± 8.3 years and 64.31% were female, 35.69% were male. The mean body mass index was 31.1 ± 5.9 kg/m. 2. For those who reported multiple stairs at home, the mean age was 62.6 ± 8.3 years and 62.3% were female. The mean body mass index was 30.7 ± 5.4 kg/m. 2. . As expected, the immediate post-op (2–4 days) step count (median 1257.5 steps, IQR 523 – 2267) was significantly lower than preop (median 4160 steps, IQR 2669 – 6034, p < 0.001). Approximately 50% of patients returned to preoperative step counts by 1.5 months postoperatively with a median 4,504 steps (IQR, 2711, 6121, p=0.8230, Figure 1). Improvements in step count continued throughout the remainder of follow-up with the 6-month follow-up visit (median 5517 steps, IQR 3888 – 7279) showing the greatest magnitude (p<0.001). In patients who reported stairs in their homes, approximately 64% of subjects returned to pre-op flight counts by 3 months (p=0.085), followed similar trends with significant improvements at 6 months (p=0.003). Finally, there was no difference in age, sex, BMI, or operative knee between those that returned to mean preoperative step or flight counts by 1.5 months and 3 months, respectively. Discussion and Conclusion. These data demonstrated a recovery curve similar to previously reported curves for patient reported outcome measures in the arthroplasty arena. Patients and surgeons may use this information to help set goals for recovery following total and unicondylar knee arthroplasty using objective activity measures. For any figures or tables, please contact the authors directly

Abstract. Background. The use of tourniquet in knee arthroplasty is common but in recent times, it has initiated a debate on its use. Complications from use of tourniquet are well documented in literature but there is less evidence on thigh pain, blood loss and length of stay post arthroplasty. Methods. We included 62 patients undergoing knee arthroplasty either Unicondylar knee arthroplasty or total knee arthroplasty. Patients were allocated randomly in tourniquet and without tourniquet groups. Half of the patients had UKA and other half TKA. Thigh pain was recorded using Visual analogue scale on day 1, 2 and on discharge. A drop in pre-operative and post operative haemoglobin level was recorded too. Independent sample t-test was done to compare the difference between the 2 groups mainly, drop in haemoglobin, thigh pain, knee pain and length of stay. Results. The mean drop in haemoglobin was comparable and was not statistically significant. Thigh pain on day 1 in no tourniquet group had a mean value of 0 and statistically significant difference in thigh pain at day 1,2 and discharge. In subgroup analysis between TKA and UKA the latter had improved results. Conclusions. Knee arthroplasty surgery without the use of tourniquet provides less thigh pain in the post-operative period and there isn't any significant difference in post op haemoglobin drop. None of the patient required any blood transfusion. A trend of early discharge was noted too but probably due to sample size, it wasn't statistically significant

Introduction. Recent advances in algorithms developed with passively collected sensor data from smart phones and watches demonstrate new, objective, metrics with the capacity to show qualitative gait characteristics. The purpose of this feasibility study was to assess the recovery of gait quality following primary total hip and knee arthroplasty collected using a smartphone-based care platform. Methods. A secondary data analysis of an IRB approved multicenter prospective trial evaluating the use of a smartphone-based care platform for primary total knee arthroplasty (TKA, n=88), unicondylar knee arthroplasty (UKA, n=28), and total hip arthroplasty (THA, n=82). Subjects were followed from 6 weeks preoperative to 24 weeks postoperative. The group was comprised of 117 females and 81 males with a mean age of 61.4 and BMI of 30.7. Signals were collected from the participants' smartphones. These signals were used to estimate gait quality according to walking speed, step length, and timing asymmetry. Post-operative measures were compared to preoperative baseline levels using a Signed-Rank test (p<0.05). Results. Mean walking speeds were lowest at postoperative week 2 for all three procedures (p<.001). The TKA population stabilized to preoperative speeds by week 17. For UKA cases, mean walking speeds rebounded to preoperative speed consistently by week 9 (p>.05). THA cases returned to preoperative walking speeds with a stable rebound starting at week 6 (p>.05), and improvement was seen at week 14 (p=.025). The average weekly step length was lowest in postoperative week 2 for both TKA and UKA (p<.001), and at week 3 for THA (p<.001). The TKA population rebounded to preoperative step lengths at week 9 (p=0.109), UKA cases at week 7 (p=.123), and THA cases by week 6 (p=.946). For TKA subjects, the change in average weekly gait asymmetry peaked at week 2 postoperatively (p <0.001), returning to baseline symmetry by week 13 (p=.161). For UKA cases, mean gait asymmetry also reached its maximum at week 2 (p =.006), returning to baseline beginning at week 7 (p=0.057). For THA cases mean asymmetry reached its maximum in week 2 (p <0.001) and was returned to baseline values at week 6 (p=.150). Discussion and Conclusion. Monitoring gait quality in real-world patient care following hip and knee arthroplasty using smart phone technology demonstrated recovery curves similar to previously reported curves captured by traditional gait analysis methods and patient reported outcome scores. Capturing such real-world gait quality metrics passively through the phone may also provide the advantage of removing the Hawthorne effect related to typical gait assessments and in-clinic observations, leading to a more accurate picture of patient function

The knee is one of the most commonly affected joints in osteoarthritis. Unicompartmental knee replacement (UKA) was developed to address patients with this disease in only one compartment. The conventional knee arthroplasty jigs, while usually being accurate, may result in the prosthesis being inserted in an undesired alignment which may lead to poor post-operative outcomes. Common modes of failure in UKA include edge loading due to incorrect sizing or positioning, development of disease in the other compartment due to over-stuffing or over-correction and early loosening or stress fractures due to inaccurate bone cuts. Computer navigation and robotically assisted unicompartmental knee replacement were introduced in order to improve the surgical accuracy of both the femoral and tibial bone cuts. The aim of this study was to assess accuracy and reliability of robotic assisted, unicondylar knee surgery in producing reported bony alignment. Two hundred and twenty consecutive patients with a mean age of 64 + 11 years who underwent successful medial robotic assisted unicondylar knee surgery performed by two senior total joint arthroplasty surgeons were identified retrospectively. The mean body mass index of the cohort was 33.5 + 8 kg/m. 2. with a minimum follow-up of 6 months (range: 6–18 months). Femoral and tibial sagittal and coronal alignments as well as the posterior slope of the tibial component were measured in the post-operative radiographs. These measurements were compared with the equivalent measurements collected during intra-operative period by the navigation to study the reliability and accuracy of femoral and tibial cuts. Radiographic evaluation was independently conducted by two observers. There was an average difference of 2.2 to 3.6 degrees between the intra-operatively planned and post-operative radiological equivalent measurements. For the femur, mean varus/valgus angulation was 2.8 + 2.5 degrees with 83% of those measured within 5% of planned. For the tibia mean varus/valgus angulation was 2.4 + 1.9 degrees with 93% within 5% of planned resection. There was minimal inter-observer variability between radiographic measurements. There were no infections in the evaluated group at the time of radiographic examination. Alignment for unicondylar knee arthroplasty is important for implant survival and is a more difficult procedure to instrument as it is a minimally invasive surgery. Assuming appropriate planning, robotically assisted surgery in unicondylar knee replacement will result in reliably accurate positioning of component and reduce early component failures caused by malpositioning. A mismatch between pre-planning and post-operative radiography is often caused by poor cementing technique of the prosthesis rather than incorrect bony cuts. Addressing these factors can lead to greater success and improved outcomes for patients