The outcome of high tibial osteotomy (HTO) deteriorates with time, and additional procedures may be required. The aim of this study was to compare the clinical and radiological outcomes between unicompartmental knee replacement (UKR) and total knee replacement (TKR) after HTO as well as after primary UKR. A total of 63 patients (63 knees) were studied retrospectively and divided into three groups: UKR after HTO (group A; n = 22), TKR after HTO (group B; n = 18) and primary UKR (group C; n = 22). The Oxford knee score (OKS), Knee Society score (KSS), hip–knee–ankle angles, mechanical axis and patellar height were evaluated pre- and post-operatively. At a mean of 64 months (19 to 180) post-operatively the mean OKS was 43.8 (33 to 49), 43.3 (30 to 48) and 42.5 (29 to 48) for groups A, B and C, respectively (p = 0.73). The mean KSS knee score was 88.8 (54 to 100), 88.11 (51 to 100) and 85.3 (45 to 100) for groups A, B and C, respectively (p = 0.65), and the mean KSS function score was 85.0 (50 to 100) in group A, 85.8 (20 to 100) in group B and 79.3 (50 to 100) in group C (p = 0.48). Radiologically the results were comparable for all groups except for patellar height, with a higher incidence of patella infra following a previous HTO (p = 0.02). Cite this article: Bone Joint J 2013;95-B:1348–53

Aims. Unicompartmental knee arthroplasty (UKA) has a higher risk of revision than total knee arthroplasty (TKA), particularly for younger patients. The outcome of knee arthroplasty is typically defined as implant survival or revision incidence after a defined number of years. This can be difficult for patients to conceptualize. We aimed to calculate the ‘lifetime risk’ of revision for UKA as a more meaningful estimate of risk projection over a patient’s remaining lifetime, and to compare this to TKA. Methods. Incidence of revision and mortality for all primary UKAs performed from 1999 to 2019 (n = 13,481) was obtained from the New Zealand Joint Registry (NZJR). Lifetime risk of revision was calculated for patients and stratified by age, sex, and American Society of Anesthesiologists (ASA) grade. Results. The lifetime risk of revision was highest in the youngest age group (46 to 50 years; 40.4%) and decreased sequentially to the oldest (86 to 90 years; 3.7%). Across all age groups, lifetime risk of revision was higher for females (ranging from 4.3% to 43.4% vs males 2.9% to 37.4%) and patients with a higher ASA grade (ASA 3 to 4, ranging from 8.8% to 41.2% vs ASA 1 1.8% to 29.8%). The lifetime risk of revision for UKA was double that of TKA across all age groups (ranging from 3.7% to 40.4% for UKA, and 1.6% to 22.4% for TKA). The higher risk of revision in younger patients was associated with aseptic loosening in both sexes and pain in females. Periprosthetic joint infection (PJI) accounted for 4% of all UKA revisions, in contrast with 27% for TKA; the risk of PJI was higher for males than females for both procedures. Conclusion. Lifetime risk of revision may be a more meaningful measure of arthroplasty outcomes than implant survival at defined time periods. This study highlights the higher lifetime risk of UKA revision for younger patients, females, and those with a higher ASA grade, which can aid with patient counselling prior to UKA. Cite this article: Bone Joint J 2022;104-B(6):672–679

Introduction. Unicompartmental knee arthroplasty (UKA) currently experiences increased popularity. It is usually assumed that UKA shows kinematic features closer to the natural knee than total knee arthroplasty (TKA). Especially in younger patients more natural knee function and faster recovery have helped to increase the popularity of UKA. Another leading reason for the popularity of UKA is the ability to preserve the remaining healthy tissues in the knee, which is not always possible in TKA. Many biomechanical questions remain, however, with respect to this type of replacement. 25% of knees with medial compartment osteoarthritis also have a deficient anterior cruciate ligament [1]. In current clinical practice, medial UKA would be contraindicated in these patients. Our hypothesis is that kinematics after UKA in combination with ACL reconstruction should allow to restore joint function close to the native knee joint. This is clinically relevant, because functional benefits for medial UKA should especially be attractive to the young and active patient. Materials and Methods. Six fresh frozen full leg cadaver specimens were prepared to be mounted in a kinematic rig (Figure 1) with six degrees of freedom for the knee joint. Three motion patterns were applied: passive flexion-extension, open chain extension, and squatting. These motion patterns were performed in four situations for each specimen: with the native knee; after implantation of a medial UKA (Figure 2); next after cutting the ACL and finally after reconstruction of the ACL. During the loaded motions, quadriceps and hamstrings muscle forces were applied. Infrared cameras continuously recorded the trajectories of marker frames rigidly attached to femur, tibia and patella. Prior computer tomography allowed identification of coordinate frames of the bones and calculations of anatomical rotations and translations. Strains in the collateral ligaments were calculated from insertion site distances. Results. Knee kinematics and collateral ligament strains were quite close to the native situation after both UKA and ACL reconstruction for all motor tasks. Nevertheless, some statistically significant differences were detected, which may be relevant clinically and biomechanically. In general, insertion of a UKA led to a knee joint which was somewhat less adducted (Figure 3), with a medial femoral condyle located slightly higher, confirming previously published findings [2]. These effects were slightly reduced both after cutting as well as after reconstructing the ACL. The joint became somewhat less stable in the AP direction after insertion of a UKA and this instability persisted not only after cutting but even after reconstructing the ACL

Aims. Robotic arm-assisted surgery offers accurate and reproducible guidance in component positioning and assessment of soft-tissue tensioning during knee arthroplasty, but the feasibility and early outcomes when using this technology for revision surgery remain unknown. The objective of this study was to compare the outcomes of robotic arm-assisted revision of unicompartmental knee arthroplasty (UKA) to total knee arthroplasty (TKA) versus primary robotic arm-assisted TKA at short-term follow-up. Methods. This prospective study included 16 patients undergoing robotic arm-assisted revision of UKA to TKA versus 35 matched patients receiving robotic arm-assisted primary TKA. In all study patients, the following data were recorded: operating time, polyethylene liner size, change in haemoglobin concentration (g/dl), length of inpatient stay, postoperative complications, and hip-knee-ankle (HKA) alignment. All procedures were performed using the principles of functional alignment. At most recent follow-up, range of motion (ROM), Forgotten Joint Score (FJS), and Oxford Knee Score (OKS) were collected. Mean follow-up time was 21 months (6 to 36). Results. There were no differences between the two treatment groups with regard to mean change in haemoglobin concentration (p = 0.477), length of stay (LOS, p = 0.172), mean polyethylene thickness (p = 0.065), or postoperative complication rates (p = 0.295). At the most recent follow-up, the primary robotic arm-assisted TKA group had a statistically significantly improved OKS compared with the revision UKA to TKA group (44.6 (SD 2.7) vs 42.3 (SD 2.5); p = 0.004) but there was no difference in the overall ROM (p = 0.056) or FJS between the two treatment groups (86.1 (SD 9.6) vs 84.1 (4.9); p = 0.439). Conclusion. Robotic arm-assisted revision of UKA to TKA was associated with comparable intraoperative blood loss, early postoperative rehabilitation, functional outcomes, and complications to primary robotic TKA at short-term follow-up. Robotic arm-assisted surgery offers a safe and reproducible technique for revising failed UKA to TKA. Cite this article: Bone Joint J 2024;106-B(7):680–687

Aims. This systematic review aims to compare the precision of component positioning, patient-reported outcome measures (PROMs), complications, survivorship, cost-effectiveness, and learning curves of MAKO robotic arm-assisted unicompartmental knee arthroplasty (RAUKA) with manual medial unicompartmental knee arthroplasty (mUKA). Methods. Searches of PubMed, MEDLINE, and Google Scholar were performed in November 2021 according to the Preferred Reporting Items for Systematic Review and Meta-­Analysis statement. Search terms included “robotic”, “unicompartmental”, “knee”, and “arthroplasty”. Published clinical research articles reporting the learning curves and cost-effectiveness of MAKO RAUKA, and those comparing the component precision, functional outcomes, survivorship, or complications with mUKA, were included for analysis. Results. A total of 179 articles were identified from initial screening, of which 14 articles satisfied the inclusion criteria and were included for analysis. The papers analyzed include one on learning curve, five on implant positioning, six on functional outcomes, five on complications, six on survivorship, and three on cost. The learning curve was six cases for operating time and zero for precision. There was consistent evidence of more precise implant positioning with MAKO RAUKA. Meta-analysis demonstrated lower overall complication rates associated with MAKO RAUKA (OR 2.18 (95% confidence interval (CI) 1.06 to 4.49); p = 0.040) but no difference in re-intervention, infection, Knee Society Score (KSS; mean difference 1.64 (95% CI -3.00 to 6.27); p = 0.490), or Western Ontario and McMaster Universities Arthritis Index (WOMAC) score (mean difference -0.58 (95% CI -3.55 to 2.38); p = 0.700). MAKO RAUKA was shown to be a cost-effective procedure, but this was directly related to volume. Conclusion. MAKO RAUKA was associated with improved precision of component positioning but was not associated with improved PROMs using the KSS and WOMAC scores. Future longer-term studies should report functional outcomes, potentially using scores with minimal ceiling effects and survival to assess whether the improved precision of MAKO RAUKA results in better outcomes. Cite this article: Bone Joint J 2022;104-B(5):541–548

Aims. Unicompartmental knee arthroplasty (UKA) has higher revision rates than total knee arthroplasty (TKA). As revision of UKA may be less technically demanding than revision TKA, UKA patients with poor functional outcomes may be more likely to be offered revision than TKA patients with similar outcomes. The aim of this study was to compare clinical thresholds for revisions between TKA and UKA using revision incidence and patient-reported outcomes, in a large, matched cohort at early, mid-, and late-term follow-up. Methods. Analyses were performed on propensity score-matched patient cohorts of TKAs and UKAs (2:1) registered in the New Zealand Joint Registry between 1 January 1999 and 31 December 2019 with an Oxford Knee Score (OKS) response at six months (n, TKA: 16,774; UKA: 8,387), five years (TKA: 6,718; UKA: 3,359), or ten years (TKA: 3,486; UKA: 1,743). Associations between OKS and revision within two years following the score were examined. Thresholds were compared using receiver operating characteristic analysis. Reasons for aseptic revision were compared using cumulative incidence with competing risk. Results. Fewer TKA patients with ‘poor’ outcomes (≤ 25) subsequently underwent revision compared with UKA at six months (5.1% vs 19.6%; p < 0.001), five years (4.3% vs 12.5%; p < 0.001), and ten years (6.4% vs 15.0%; p = 0.024). Compared with TKA, the relative risk for UKA was 2.5-times higher for ‘unknown’ reasons, bearing dislocations, and disease progression. Conclusion. Compared with TKA, more UKA patients with poor outcomes underwent revision from early to long-term follow-up, and were more likely to undergo revision for ‘unknown’ reasons, which suggest a lower clinical threshold for UKA. For UKA, revision risk was higher for bearing dislocations and disease progression. There is supporting evidence that the higher revision UKA rates are associated with lower clinical thresholds for revision and additional modes of failure. Cite this article: Bone Joint J 2023;105-B(3):269–276

Aims. The aim of this study was to describe the pattern of revision indications for unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) and any change to this pattern for UKA patients over the last 20 years, and to investigate potential associations to changes in surgical practice over time. Methods. All primary knee arthroplasty surgeries performed due to primary osteoarthritis and their revisions reported to the Danish Knee Arthroplasty Register from 1997 to 2017 were included. Complex surgeries were excluded. The data was linked to the National Patient Register and the Civil Registration System for comorbidity, mortality, and emigration status. TKAs were propensity score matched 4:1 to UKAs. Revision risks were compared using competing risk Cox proportional hazard regression with a shared γ frailty component. Results. Aseptic loosening (loosening) was the most common revision indication for both UKA (26.7%) and TKA (29.5%). Pain and disease progression accounted for 54.6% of the remaining UKA revisions. Infections and instability accounted for 56.1% of the remaining TKA revision. The incidence of revision due to loosening or pain decreased over the last decade, being the second and third least common indications in 2017. There was a decrease associated with fixation method for pain (hazard ratio (HR) 0.40; 95% confidence interval (CI) 0.17 to 0.94) and loosening (HR 0.29; 95% CI 0.10 to 0.81) for cementless compared to cemented, and units UKA usage for pain (HR 0.67, 95% CI 0.50 to 0.91), and loosening (HR 0.51; 95% CI 0.37 to 0.70) for high usage. Conclusion. The overall revision patterns for UKA and TKA for the last 20 years are comparable to previous published patterns. We found large changes to UKA revision patterns in the last decade, and with the current surgical practice, revision due to pain or loosening are significantly less likely. Cite this article: Bone Jt Open 2023;4(12):923–931

Aims. The primary aim of the study was to perform an analysis to identify the cost per quality-adjusted life-year (QALY) of robot-assisted unicompartmental knee arthroplasty (rUKA) relative to manual total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA) for patients with isolated medial compartment osteoarthritis (OA) of the knee. Secondary aims were to assess how case volume and length of hospital stay influenced the relative cost per QALY. Patients and Methods. A Markov decision analysis was performed, using known parameters for costs, outcomes, implant survival, and mortality, to assess the cost-effectiveness of rUKA relative to manual TKA and UKA for patients with isolated medial compartment OA of the knee with a mean age of 65 years. The influence of case volume and shorter hospital stay were assessed. Results. Using a model with an annual case volume of 100 patients, the cost per QALY of rUKA was £1395 and £1170 relative to TKA and UKA, respectively. The cost per QALY was influenced by case volume: a low-volume centre performing ten cases per year would achieve a cost per QALY of £7170 and £8604 relative to TKA and UKA. For a high-volume centre performing 200 rUKAs per year with a mean two-day length of stay, the cost per QALY would be £648; if performed as day-cases, the cost would be reduced to £364 relative to TKA. For a high-volume centre performing 200 rUKAs per year with a shorter length of stay of one day relative to manual UKA, the cost per QALY would be £574. Conclusion . rUKA is a cost-effective alternative to manual TKA and UKA for patients with isolated medial compartment OA of the knee. The cost per QALY of rUKA decreased with reducing length of hospital stay and with increasing case volume, compared with TKA and UKA. Cite this article: Bone Joint J 2019;101-B:1063–1070

Unicompartmental knee arthroplasty (UKA) is associated with a higher risk of revision compared with total knee arthroplasty (TKA). The outcomes of knee arthroplasty are typically presented as implant survival or incidence of revision after a set number of years, which can be difficult for patients and clinicians to conceptualise. We aimed to calculate the ‘lifetime risk’ of revision for UKA as a more relatable estimate of risk projection over a patient's remaining lifetime, and make comparisons to TKA. All primary UKAS performed from 1999 to 2019 (n=13,481) captured by the New Zealand Joint Registry (NZJR) were included. The lifetime risk of revision was calculated and stratified by age, gender and American Society of Anesthesiologists (ASA) status. The lifetime risk of revision for UKA was highest in the youngest patients (46-50 years; 40.4%) and lowest in the oldest patients (86-90 years; 3.7%). Lifetime risk of revision was higher for females (range 4.3%-43.4% cf. males 2.9%-37.4%) and patients with higher ASA status (ASA 3-4 range 8.8%-41.2% cf. ASA 1 1.8%-29.8%), regardless of age. The lifetime risk of UKA was two-fold higher than TKA (ranging from 3.7%-40.4% UKA, 1.6%-22.4% TKA) across all age groups. Increased risk of revision in the younger patients was associated with aseptic loosening in both males and females, and pain in females. Periprosthetic joint infections (PJI) accounted for 4% of all UKA revisions, in contrast to 27% for TKA; risk of PJI was higher for males than females for both procedures. The lifetime risk of revision is a more meaningful measure of arthroplasty outcomes and can aid with patient counselling prior to UKA. Findings from this study show the increased lifetime risk of UKA revision for younger patients, females and those with higher ASA status

Introduction. A key outcome measured by national joint registries are revision events. This informs best practice and identifies poor-performing surgical devices. Although registry data often record reasons for revision arthroplasty, interpretation is limited by lack of standardised definitions of revision reasons and objective assessment of radiologic and laboratory parameters. Our study aim was to compare reasons for unicompartmental knee arthroplasty (UKA) revision reported to the New Zealand Joint Registry (NZJR) with reasons identified by independent clinical review. Methods. A total of 2,272 patients undergoing primary medial and lateral UKA at four large tertiary hospitals between 2000 and 2017 were included. A total of 158 patients underwent subsequent revision with mean follow-up of 8 years. A systematic review of clinical findings, radiographs and operative data was performed to identify revision cases and to determine the reasons for revision using a standardised protocol. These were compared to reasons reported to the NZJR using Chi-squared and Fisher exact tests. Results. Osteoarthritis progression was the most common reason for revision on systematic clinical review (30%), however this was underreported to the registry (4%, p<0.001). A larger proportion of revisions reported to the registry were for ‘unexplained pain’ (30% of cases vs. 4% on clinical review, p<0.001). A reason for revision was not reported to the registry for 24 (15%) of cases. Discussion and Conclusion. We found significant inaccuracies in registry-reported reasons for revision following UKA. These included over-reporting of ‘unexplained pain’, under-reporting of osteoarthritis progression, and failure to identify a reason for revision. Efforts to improve registry capture of revision reasons for UKA should focus on increasing accuracy in these three areas. This could be addressed through standardised recording methods and tailored revision reason options for UKA for surgeons to select when recording the reasons

Aims. The aim of this prospective multicentre study was to describe trends in length of stay and early complications and readmissions following unicompartmental knee arthroplasty (UKA) performed at eight different centres in Denmark using a fast-track protocol and to compare the length of stay between centres with high and low utilization of UKA. Methods. We included data from eight dedicated fast-track centres, all reporting UKAs to the same database, between 2010 and 2018. Complete ( > 99%) data on length of stay, 90-day readmission, and mortality were obtained during the study period. Specific reasons for a length of stay of > two days, length of stay > four days, and 30- and 90-day readmission were recorded. The use of UKA in the different centres was dichotomized into ≥ 20% versus < 20% of arthroplasties which were undertaken being UKAs, and ≥ 52 UKAs versus < 52 UKAs being undertaken annually. Results. A total of 3,927 procedures were included. Length of stay (mean 1.1 days (SD 1.1), median 1 (IQR 0 to 1)) was unchanged during the study period. The proportion of procedures with a length of stay > two days was also largely unchanged during this time. The percentage of patients discharged on the day of surgery varied greatly between centres (0% to 50% (0 to 481)), with centres with high UKA utilization (both usage and volume) having a larger proportion of same-day discharges. The 30- and 90-day readmissions were 166 (4.2%) and 272 (6.9%), respectively; the 90-day mortality was 0.08% (n = 3). Conclusion. Our findings suggest general underutilization of the potential for quicker recovery following UKA in a fast-track setup. Cite this article: Bone Joint J 2020;102-B(9):1167–1175

Aims. To report mid- to long-term results of Oxford mobile bearing domed lateral unicompartmental knee arthroplasty (UKA), and determine the effect of potential contraindications on outcome. Methods. A total of 325 consecutive domed lateral UKAs undertaken for the recommended indications were included, and their functional and survival outcomes were assessed. The effects of age, weight, activity, and the presence of full-thickness erosions of cartilage in the patellofemoral joint on outcome were evaluated. Results. Median follow-up was seven years (3 to 14), and mean age at surgery was 65 years (39 to 90). Median Oxford Knee Score (OKS) was 43 (interquartile range (IQR) 37 to 47), with 260 (80%) achieving a good or excellent score (OKS > 34). Revisions occurred in 34 (10%); 14 (4%) were for dislocation, of which 12 had no recurrence following insertion of a new bearing, and 12 (4%) were revised for medial osteoarthritis (OA). Ten-year survival was 85% (95% confidence interval (CI) 79 to 90, at risk 72). Age, weight, activity, and patellofemoral erosions did not have a significant effect on the clinical outcome or survival. Conclusion. Domed lateral UKA provides a good alternative to total knee arthroplasty (TKA) in the management of lateral compartment OA. Although dislocation is relatively easy to treat successfully, the dislocation rate of 4% is high. It is recommended that the stability of the bearing is assessed intraoperatively. If the bearing can easily be displaced, the fixed rather than the mobile bearing version of the Oxford lateral tibial component should be inserted instead. Younger age, heavier weight, high activity, and patellofemoral erosions did not detrimentally affect outcome, so should not be considered contraindications. Cite this article: Bone Joint J 2020;102-B(8):1033–1040

Introduction. This study assessed outcomes of total knee joint replacements (TKJR) in patients who had undergone previous periarticular osteotomy compared with unicompartmental knee replacement (UKR). Establishing a difference in the results of total knee joint replacements following these operations may be an important consideration in the decision-making and patient counselling around osteotomy versus UKR for the management of single-compartment osteoarthritis. Method. Using data from the New Zealand Joint Registry, we identified 1,895 total knee joint replacements with prior osteotomy and 1,391 with prior UKR. Revision rates and patient-reported outcomes, as measured by the Oxford Knee Score (OKS), between these two groups were compared. Adjusted hazard ratios were also calculated to compare the groups. Results. The revision rate for total knee joint replacement following osteotomy was significantly lower than TKJR following UKR (0.88 per 100 component years versus 1.38 per 100 component years, respectively). Adjusted hazard ratio calculations found that those with TKJR with prior UKR had more than double the risk of requiring revision than those with prior osteotomy. Additionally, there was a statistically significant difference in the mean adjusted OKS scores between the two groups, with improved outcomes in the group with prior osteotomy. Conclusion. Our findings suggest that total knee joint replacement following periarticular osteotomy have a lower risk of revision and improved OKS when compared to those with prior UKR. Previous studies assessing New Zealand Joint Registry have not found a statistically significant difference between the two groups however, these results are no longer in keeping with more contemporary literature. Our study confirms the New Zealand population to be comparable with international studies with TKJR after osteotomy performing significantly better compared with prior UKR

Aims. Higher osteoblastic bone activity is expected in aseptic loosening and painful unicompartmental knee arthroplasty (UKA). However, insights into normal bone activity patterns after medial UKAs are lacking. The aim of this study was to identify the evolution in bone activity pattern in well-functioning medial mobile-bearing UKAs. Methods. In total, 34 patients (13 female, 21 male; mean age 62 years (41 to 79); BMI 29.7 kg/m. 2. (23.6 to 42.1)) with 38 medial Oxford partial UKAs (20 left, 18 right; 19 cementless, 14 cemented, and five hybrid) were prospectively followed with sequential 99mTc-hydroxymethane diphosphonate single photon emission CT (SPECT)/CT preoperatively, and at one and two years postoperatively. Changes in mean osteoblastic activity were investigated using a tracer localization scheme with volumes of interest (VOIs), reported by normalized mean tracer values. A SPECT/CT registration platform additionally explored cortical tracer evolution in zones of interest identified by previous experimental research. Results. Significant reduction of tracer activity from the preoperative situation was found in femoral and anteromedial tibial VOIs adjacent to the UKA components. Temporarily increased osteoblastic bone activity was observed in VOIs comprising the UKA keel structure at one year postoperatively compared to the preoperative activity. Persistent higher tracer uptake was found in the posterior tibial cortex at final follow-up. Multivariate analysis showed no statistical difference in osteoblastic bone activity underneath cemented or cementless components. Conclusion. Well-functioning medial mobile-bearing UKAs showed distinct changes in patterns of normalized bone tracer activity in the different VOIs adjacent to the prosthetic components, regardless of their type of fixation. Compared to the preoperative situation, persistent high bone activity was found underneath the keel and the posterior tibial cortex at final follow-up, with significant reduced activity only being identified in femoral and anteromedial tibial VOIs. Cite this article: Bone Joint J 2022;104-B(1):34–44

Abstract. Purpose. Unicompartmental knee arthroplasty (UKA) is an effective treatment for late knee osteoarthritis (OA). However, its indications remain controversial. Young age (< 60 years) has been associated with worse outcomes. The goal of this systematic review and meta-analysis is to study the effect of age on UKA outcomes. Methods. The primary objective was to compare the UKA revision rate in young patients with that of old patients, using the age thresholds of 60 and 55 years. Secondary objectives were patient-reported outcome measures (PROMs) and implant design. PubMed, Ovid, Web of Science, Google Scholar, and Cochrane library were searched in June 2021. This review was conducted in accordance with the PRISMA guidelines (PROSPERO registration number: CRD42021248322). Results. A total of 12 observational studies with 6,448 knees were included. A mean MINORS score of 19 was assigned to the review. The mean age of patients was 64.32 years, with follow-up ranging from 0.2 to 15 years. There was no significant difference in revision rate, incident or PROMs between young and old patients in the analysis for each age threshold. Further sub-analysis adjusting for implant type in mobile- and fixed-bearing prostheses also showed similar results between those above and under 60 and 55 years. Conclusion. Young age was not associated with a higher revision rate or lower functional scores. Thus, this review provides evidence that performing UKA at a younger age (< 60 years) should not be considered suboptimal. However, this finding should be applied in context, as other confounding factors need to be explored

Purpose. We may consider total knee arthroplasty on one knee and unicompartmental knee arthroplasty on another knee when the patient has different grade osteoarthritis on one knee and opposite knee. Both total knee and unicompartmental knee arthroplasty had been reported as excellent clinical results, but there can be different results and different preference if the same patient undergo operation of simulataneous total knee and unicompartmental knee. We performed total and unicompartmental knee arthroplasty and pretend to report results of the clinical and radiological results and rationale of the operation. Materials and Methods. From Marth 2007 to February 2014, 23 patients, 46 knees that underwent total knee arthroplasty and unicompartmental knee arthroplasty on knees with different osteoarthritis grade in same person enrolled in this study(Fig. 1). The mean age was 64.4 years old(range:55–75) and mean follow-up period was 25.1 months(range:13–72). Results. The tibiofemoral angle changed from 4.0 of varus to 5.4 of valgus in the total knee arthroplasty, and from 0.5 of valgus to 3.8 of valgus in the unicompartmental knee arthroplasty. The mechanical axis deviation changed from varus 28.35mm to varus 3.68mm in the total knee arthroplasty, and from 16.42 to 8.81 in the unicompartmental knee arthroplasty. The average Hospital for Special Surgery Knee-Rating Scale(HSS) improved from 55.1 preoperatively to 93.4 at last follow-up in the total knee arthroplasty, and from 65.2 to 95.2 in the unicompartmental knee arthroplasty. The average WOMAC Score improved from 61.6 preoperatively to 18.0 at last follow-up in the total knee arthroplasty, and from 55.4 to 16.2 in the unicompartmental knee arthroplasty. For patient preference, 5 patients(22%) preferred the unicompartmental knee arthroplasty, and 6 patients(26%) preferred the total knee arthroplasty, and 12 patients felt no difference between two knees. 20 patients(87%) reported being ‘very satisfied’ or ‘satisfied’ in the total knee arthroplasty, and 18 patients(79%) reported in the unicompartmental knee arthroplasty. We underwent 1 case complication of tibial implant loosening and varus malalignment. So, we converted total knee arthroplasty about 3 months later(Fig. 2). Conclusions. Total knee arthroplasty and unicompartmental knee arthroplasty in same person showed satisfactory clinical and radiological results. There was no difference in preference site and postoperative range of motion showed more regainment on unicompartmental knee arthroplasty. More complications were demonstrated in unicompartmental knee arthroplasty. Total and unicompartmental knee arthroplasty in same person seems to be a good option when the both knee have different osteoarthritis grade

Objectives. Elevated proximal tibial bone strain may cause unexplained pain, an important cause of unicompartmental knee arthroplasty (UKA) revision. This study investigates the effect of tibial component alignment in metal-backed (MB) and all-polyethylene (AP) fixed-bearing medial UKAs on bone strain, using an experimentally validated finite element model (FEM). Methods. A previously experimentally validated FEM of a composite tibia implanted with a cemented fixed-bearing UKA (MB and AP) was used. Standard alignment (medial proximal tibial angle 90°, 6° posterior slope), coronal malalignment (3°, 5°, 10° varus; 3°, 5° valgus), and sagittal malalignment (0°, 3°, 6°, 9°, 12°) were analyzed. The primary outcome measure was the volume of compressively overstrained cancellous bone (VOCB) < -3000 µε. The secondary outcome measure was maximum von Mises stress in cortical bone (MSCB) over a medial region of interest. Results. Varus malalignment decreased VOCB but increased MSCB in both implants, more so in the AP implant. Varus malalignment of 10° reduced the VOCB by 10% and 3% in AP and MB implants but increased the MSCB by 14% and 13%, respectively. Valgus malalignment of 5° increased the VOCB by 8% and 4% in AP and MB implants, with reductions in MSCB of 7% and 10%, respectively. Sagittal malalignment displayed negligible effects. Well-aligned AP implants displayed greater VOCB than malaligned MB implants. Conclusion. All-polyethylene implants are more sensitive to coronal plane malalignments than MB implants are; varus malalignment reduced cancellous bone strain but increased anteromedial cortical bone stress. Sagittal plane malalignment has a negligible effect on bone strain. Cite this article: I. Danese, P. Pankaj, C. E. H. Scott. The effect of malalignment on proximal tibial strain in fixed-bearing unicompartmental knee arthroplasty: A comparison between metal-backed and all-polyethylene components using a validated finite element model. Bone Joint Res 2019;8:55–64. DOI: 10.1302/2046-3758.82.BJR-2018-0186.R2

Unicompartmental knee arthroplasty (UKA) and high tibial osteotomy (HTO) are well-established operative interventions in the treatment of knee osteoarthritis (KOA). However, which of these interventions is more beneficial, to patients with KOA, is not known and remains a topic of much debate. Aims: (i) To determine whether UKA or HTO is more beneficial in the treatment of isolated medial compartment KOA, via an assessment of patient-reported outcome measures (PROMs). (ii) To investigate the relationship between PROMs and radiographic parameters of knee joint orientation/alignment. This longitudinal observational study assessed a total of 42 patients that had undergone UKA (n=23) or HTO (n=19) to treat isolated medial compartment KOA. The PROMs assessed, pre-operatively and 1-year post-operatively, consisted of the: self-administered comorbidity questionnaire; short form-12; oxford knee score; knee injury and osteoarthritis outcome score; and the EQ-5D-5L. The radiographic parameters of knee joint alignment/orientation assessed, pre-operatively and 8-weeks post-operatively, included the: hip-knee-ankle angle; mechanical axis deviation; and the angle of the Mikulicz line. Statistical analysis demonstrated an overall significant (p<0.001), pre-operative to post-operative, improvement in the PROM scores of both groups. There were no significant differences in the post-operative PROM scores of the UKA and HTO group. Correlation analyses revealed that pre-operatively, a more distolaterally angled Mikulicz line was associated with worse knee function (p<0.05) and overall health (p<0.05); a relationship that, until now, has not been investigated nor commented upon within the literature. UKAs and HTOs are both efficacious operations that provide a comparable degree of clinical benefit to patients with isolated medial compartment KOA. To further the scientific/medical community's understanding of the factors that impact upon health-outcomes in KOA, future research should seek to investigate the mechanism underlying the relationship, between Mikulicz line and PROMs, observed within the current study

Source of the study: University of Auckland, Auckland, New Zealand and University of Otago, Christchurch, New Zealand. Patient reported outcome measures (PROMs) are predictors of knee arthroplasty revision. Unicompartmental knee arthroplasty (UKA) is effective for patients with the correct indications, however has higher revision rates than total knee arthroplasty (TKA). Different revision thresholds for the procedures have been postulated. Our aims were to investigate: 1) if PROMs could predict knee arthroplasty revision within two years of the score at six months, five years and ten years follow-up, and 2) if revision ‘thresholds’ differed between TKA and UKA. All TKAs and UKAs captured by the New Zealand Joint Registry between 1999 and 2019 with at least one OKS response at six months (TKA n=27,708, UKA n=8,415), five years (TKA n=11,519, UKA n=3,365) or ten years (TKA n=6,311, UKA n=1,744) were included. were propensity-score matched 2:1 with UKAs for comparison of revision thresholds. Logistic regression indicated that for every one-unit decrease in OKS, the odds of TKA and UKA revision decreased by 10% and 11% at six months, 10% and 12% at five years and 9% and 5% at ten years. Fewer TKA patients with ‘poor’ outcomes (≤25) subsequently underwent revision compared with UKA at six months (5.1% vs. 19.6%, p<0.001), five years (4.3% vs. 12.5%, p<0.001) and ten years (6.4%vs. 15.0%, p=0.02). Compared with TKA, UKA patients were 2.5 times more likely to undergo revision for ‘unknown’ reasons, bearing dislocations and disease progression. The OKS is a strong predictor of subsequent knee arthroplasty revision within two years of the score from early to late term. A lower revision threshold was found with UKA when compared with a matched TKA cohort. Higher revision rates of UKA are associated with both lower clinical thresholds for revision and additional modes of UKA failure

Objectives. This study reports on a secondary exploratory analysis of the early clinical outcomes of a randomised clinical trial comparing robotic arm-assisted unicompartmental knee arthroplasty (UKA) for medial compartment osteoarthritis of the knee with manual UKA performed using traditional surgical jigs. This follows reporting of the primary outcomes of implant accuracy and gait analysis that showed significant advantages in the robotic arm-assisted group. Methods. A total of 139 patients were recruited from a single centre. Patients were randomised to receive either a manual UKA implanted with the aid of traditional surgical jigs, or a UKA implanted with the aid of a tactile guided robotic arm-assisted system. Outcome measures included the American Knee Society Score (AKSS), Oxford Knee Score (OKS), Forgotten Joint Score, Hospital Anxiety Depression Scale, University of California at Los Angeles (UCLA) activity scale, Short Form-12, Pain Catastrophising Scale, somatic disease (Primary Care Evaluation of Mental Disorders Score), Pain visual analogue scale, analgesic use, patient satisfaction, complications relating to surgery, 90-day pain diaries and the requirement for revision surgery. Results. From the first post-operative day through to week 8 post-operatively, the median pain scores for the robotic arm-assisted group were 55.4% lower than those observed in the manual surgery group (p = 0.040). At three months post-operatively, the robotic arm-assisted group had better AKSS (robotic median 164, interquartile range (IQR) 131 to 178, manual median 143, IQR 132 to 166), although no difference was noted with the OKS. At one year post-operatively, the observed differences with the AKSS had narrowed from a median of 21 points to a median of seven points (p = 0.106) (robotic median 171, IQR 153 to 179; manual median 164, IQR 144 to 182). No difference was observed with the OKS, and almost half of each group reached the ceiling limit of the score (OKS > 43). A greater proportion of patients receiving robotic arm-assisted surgery improved their UCLA activity score. Binary logistic regression modelling for dichotomised outcome scores predicted the key factors associated with achieving excellent outcome on the AKSS: a pre-operative activity level > 5 on the UCLA activity score and use of robotic-arm surgery. For the same regression modelling, factors associated with a poor outcome were manual surgery and pre-operative depression. Conclusion. Robotic arm-assisted surgery results in improved early pain scores and early function scores in some patient-reported outcomes measures, but no difference was observed at one year post-operatively. Although improved results favoured the robotic arm-assisted group in active patients (i.e. UCLA ⩾ 5), these do not withstand adjustment for multiple comparisons. Cite this article: M. J. G. Blyth, I. Anthony, P. Rowe, M. S. Banger, A. MacLean, B. Jones. Robotic arm-assisted versus conventional unicompartmental knee arthroplasty: Exploratory secondary analysis of a randomised controlled trial. Bone Joint Res 2017;6:631–639. DOI: 10.1302/2046-3758.611.BJR-2017-0060.R1

Objectives. Unicompartmental knee arthroplasty (UKA) is an alternative to total knee arthroplasty for patients who require treatment of single-compartment osteoarthritis, especially for young patients. To satisfy this requirement, new patient-specific prosthetic designs have been introduced. The patient-specific UKA is designed on the basis of data from preoperative medical images. In general, knee implant design with increased conformity has been developed to provide lower contact stress and reduced wear on the tibial insert compared with flat knee designs. The different tibiofemoral conformity may provide designers the opportunity to address both wear and kinematic design goals simultaneously. The aim of this study was to evaluate wear prediction with respect to tibiofemoral conformity design in patient-specific UKA under gait loading conditions by using a previously validated computational wear method. Methods. Three designs with different conformities were developed with the same femoral component: a flat design normally used in fixed-bearing UKA, a tibia plateau anatomy mimetic (AM) design, and an increased conforming design. We investigated the kinematics, contact stress, contact area, wear rate, and volumetric wear of the three different tibial insert designs. Results. Conforming increased design showed a lower contact stress and increased contact area. In addition, increased conformity resulted in a reduction of the wear rate and volumetric wear. However, the increased conformity design showed limited kinematics. Conclusion. Our results indicated that increased conformity provided improvements in wear but resulted in limited kinematics. Therefore, increased conformity should be avoided in fixed-bearing patient-specific UKA design. We recommend a flat or plateau AM tibial insert design in patient-specific UKA. Cite this article: Y-G. Koh, K-M. Park, H-Y. Lee, K-T. Kang. Influence of tibiofemoral congruency design on the wear of patient-specific unicompartmental knee arthroplasty using finite element analysis. Bone Joint Res 2019;8:156–164. DOI: 10.1302/2046-3758.83.BJR-2018-0193.R1

Abstract. Aims. The association between body mass index (BMI) and venous thromboembolism (VTE) is well studied, but remains unclear in the literature. We aimed to determine whether morbid obesity (BMI≥40) was associated with increased risk of VTE following total knee arthroplasty (TKA) or unicompartmental knee arthroplasty (UKA), compared to those of BMI<40. Methods. Between January 2016 and December 2020, our institution performed 4506 TKAs and 449 UKAs. 450 (9.1%) patients had a BMI≥40. CT pulmonary angiography (CTPA) for suspected pulmonary embolism (PE) and ultrasound scan for suspected proximal deep vein thrombosis (DVT) were recorded up to 90 days post-operatively. Results. When comparing those of BMI<40 to those with BMI≥40, there was no difference in incidence of PE (1.0% vs 1.1%, p=0.803) or proximal DVT (0.4% vs 0.2%, p=0.645). There was no difference in number of ultrasound scans ordered (p=0.668), or number of CTPAs ordered for those with a BMI≥40 (p=0.176). The percentage of patients with a confirmed PE or proximal DVT were 24.2% and 3.9% respectively in the BMI<40 group, compared to 20.0% (p=0.804) and 2.3% (p=0.598) in the BMI≥40 group. Conclusion. Morbid obesity was not associated with increased risk of PE or proximal DVT within 90 days of TKA or UKA. Overall, 76.3% of CTPAs and 96.2% of ultrasound scans were negative. Increasing the threshold for VTE investigation would reduce the rate of negative investigations. Establishing more effective risk stratification protocols, to guide investigation, would likely reduce unnecessary imaging

Source of the study: University of Auckland, Auckland, New Zealand. Unicompartmental knee arthroplasty (UKA) has benefits for patients with appropriate indications. However, UKA has a higher risk of revision, particularly for low-usage surgeons. The introduction of robotic-arm assisted systems may allow for improved outcomes but is also associated with a learning curve. We aimed to characterise the learning curve of a robotic-arm assisted system (MAKO) for UKA in terms of operative time, limb alignment, component sizing, and patient outcomes. Operative times, pre- and post-surgical limb alignments, and component sizing were prospectively recorded for consecutive cases of primary medial UKA between 2017 and 2021 (n=152, 5 surgeons). Patient outcomes were captured with the Oxford Knee Score (OKS), EuroQol-5D (EQ-5D), Forgotten Joint Score (FJS-12) and re-operation events up to two years post-UKA. A Cumulative Summation (CUSUM) method was used to estimate learning curves and to distinguish between learning and proficiency phases. Introduction of the system had a learning curve of 11 cases. There was increased operative time of 13 minutes between learning and proficiency phases (learning 98 mins vs. proficiency 85 mins; p<0.001), associated with navigation registration and bone preparation/cutting. A learning curve was also found with polyethylene insert sizing (p=0.03). No difference in patient outcomes between the two phases were detected for patient-reported outcome measures, implant survival (both phases 98%; NS) or re-operation (learning 100% vs. proficiency: 96%; NS). Implant survival and re-operation rates did not differ between low and high usage surgeons (cut-off of 12 UKAs per year). Introduction of the robotic-arm assisted system for UKA led to increased operative times for navigation registration and bone preparation, but no differences were detected in terms of component placement or patient outcomes regardless of usage. The short learning curve regardless of UKA usage indicated that robotic-arm assisted UKA may be particularly useful for low-usage surgeons

Unicompartmental knee arthroplasty (UKA) has a higher risk of revision than total knee arthroplasty, particularly for low volume surgeons. The recent introduction of robotic-arm assisted systems has allowed for increased accuracy, however new systems typically have learning curves. The objective of this study was to determine the learning curve of a robotic-arm assisted system for UKA. Methods A total of 152 consecutive robotic-arm assisted primary medial UKA were performed by five surgeons between 2017 and 2021. Operative times, implant positioning, reoperations and patient-reported outcome measures (PROMS; Oxford Knee Score, EuroQol-5D, and Forgotten Joint Score) were recorded. There was a learning curve of 11 cases with the system that was associated with increased operative time (13 minutes, p<0.01) and improved insert sizing over time (p=0.03). There was no difference in implant survival (98.2%) between learning and proficiency phases (p = 0.15), and no difference in survivorship between ‘high’ and ‘low’ usage surgeons (p = 0.23) at 36 months. There were no differences in PROMS related to the learning curve. This suggested that the learning curve did not lead to early adverse effects in this patient cohort. The introduction of a robotic-arm assisted UKA system led to learning curves for operative time and implant sizing, but there was no effect on patient outcomes at early follow- up. The short learning curve was independent of UKA usage and indicated that robotic-arm assisted UKA may be particularly useful for low-usage surgeons

Introduction. There has been renewed interest in the unicompartmental knee arthroplasty with reports of good long term outcomes. Advantages over a more extensive knee replacement include: preservation of bone stock, retention of both cruciate ligaments, preservation of other compartments and better knee kinematics. However, a number of authors have commented on the problem of osseous defects requiring technically difficult revision surgery. Furthermore, a number of recent national register studies have shown inferior survivorship when compared to total knee arthroplasty. The purpose of this study was to review the cases of our patients who had a revision total knee arthroplasty for failed unicompartmental knee arthroplasty. To determine the reason for failure, describe the technical difficulties during revision surgery and record the clinical outcomes of the revision arthroplasties. Methods. Between 2003 and 2009 our institute performed thirty three revisions of a unicompartmental knee arthroplasty on thirty two patients. The time to revision surgery ranged from 2 months to 159 months with a median of 19 months. Details of the operations and complications were taken form case notes. Patient assessment included range of motion, need for walking aids and the functional status of the affected knee in the form of the Oxford knee score questionnaire. Results. The reasons for failure were aseptic loosening of tibial component, persistent pain, dislocated meniscus, mal-alignment and osteoarthritis in another compartment. Of the 33 revision knee arthroplasties 18 required additional intra-operative constructs. 11 knees required a long tibial stem while 1 required a long femoral stem. 10 knees required medial wedge augmentation and bone graft was used in 6. Mean 1 year Oxford knee scores for failed unicompartmental knee replacements was 29 compared to 39 for primary total knee replacements performed at the same institute. Of the revision knee replacements 2 required further revision due to infection and loosening. Conclusion. From the evidence of our group of failed unicompartmental knee replacements, revision surgery is technically difficult and often requires intra-operative constructs. Clinical outcome of revision total knee arthroplasty following failed unicompartmental knee arthroplasty is not comparable to primary total knee arthroplasty

Objectives. Unicompartmental knee arthroplasty (UKA) is a demanding procedure, with tibial component subsidence or pain from high tibial strain being potential causes of revision. The optimal position in terms of load transfer has not been documented for lateral UKA. Our aim was to determine the effect of tibial component position on proximal tibial strain. Methods. A total of 16 composite tibias were implanted with an Oxford Domed Lateral Partial Knee implant using cutting guides to define tibial slope and resection depth. Four implant positions were assessed: standard (5° posterior slope); 10° posterior slope; 5° reverse tibial slope; and 4 mm increased tibial resection. Using an electrodynamic axial-torsional materials testing machine (Instron 5565), a compressive load of 1.5 kN was applied at 60 N/s on a meniscal bearing via a matching femoral component. Tibial strain beneath the implant was measured using a calibrated Digital Image Correlation system. Results. A 5° increase in tibial component posterior slope resulted in a 53% increase in mean major principal strain in the posterior tibial zone adjacent to the implant (p = 0.003). The highest strains for all implant positions were recorded in the anterior cortex 2 cm to 3 cm distal to the implant. Posteriorly, strain tended to decrease with increasing distance from the implant. Lateral cortical strain showed no significant relationship with implant position. Conclusion. Relatively small changes in implant position and orientation may significantly affect tibial cortical strain. Avoidance of excessive posterior tibial slope may be advisable during lateral UKA. Cite this article: A. M. Ali, S. D. S. Newman, P. A. Hooper, C. M. Davies, J. P. Cobb. The effect of implant position on bone strain following lateral unicompartmental knee arthroplasty: A Biomechanical Model Using Digital Image Correlation. Bone Joint Res 2017;6:522–529. DOI: 10.1302/2046-3758.68.BJR-2017-0067.R1

Objectives. Unicompartmental knee arthroplasty (UKA) is an alternative to total knee arthroplasty with isolated medial or lateral compartment osteoarthritis. However, polyethylene wear can significantly reduce the lifespan of UKA. Different bearing designs and materials for UKA have been developed to change the rate of polyethylene wear. Therefore, the objective of this study is to investigate the effect of insert conformity and material on the predicted wear in mobile-bearing UKA using a previously developed computational wear method. Methods. Two different designs were tested with the same femoral component under identical kinematic input: anatomy mimetic design (AMD) and conforming design inserts with different conformity levels. The insert materials were standard or crosslinked ultra-high-molecular-weight polyethylene (UHMWPE). We evaluated the contact pressure, contact area, wear rate, wear depth, and volumetric wear under gait cycle loading conditions. Results. Conforming design inserts had the lower contact pressure and larger contact area. However, they also had the higher wear rate and volumetric wear. The improved wear performance was found with AMD inserts. In addition, the computationally predicted volumetric wear of crosslinked UHMWPE inserts was less than half that of standard UHMWPE inserts. Conclusion. Our results showed that increasing conformity may not be the sole predictor of wear performance; highly crosslinked mobile-bearing polyethylene inserts can also provide improvement in wear performance. These results provide improvements in design and materials to reduce wear in mobile-bearing UKA. Cite this article: Bone Joint Res 2019;8:563–569

Aims. It remains controversial whether patellofemoral joint pathology is a contraindication to lateral unicompartmental knee arthroplasty (UKA). This study aimed to evaluate the effect of preoperative radiological degenerative changes and alignment on patient-reported outcome scores (PROMs) after lateral UKA. Secondarily, the influence of lateral UKA on the alignment of the patellofemoral joint was studied. Methods. A consecutive series of patients who underwent robotic arm-assisted fixed-bearing lateral UKA with at least two-year follow-up were retrospectively reviewed. Radiological evaluation was conducted to obtain a Kellgren Lawrence (KL) grade, an Altman score, and alignment measurements for each knee. Postoperative PROMs were assessed using the Kujala (Anterior Knee Pain Scale) score, Knee Injury and Osteoarthritis Outcome Score Joint Replacement (KOOS JR), and satisfaction levels. Results. A total of 140 knees (130 patients) were identified for analysis. At mean 4.1 years (2.0 to 8.5) follow-up, good to excellent Kujala scores were reported. The presence of mild to moderate preoperative patellofemoral joint osteoarthritis had no impact on these scores (KL grade 0 vs 1 to 3, p = 0.203; grade 0 to 1 vs 2 to 3, p = 0.674). Comparable scores were reported by patients with osteoarthritis (Altman score of ≥ 2) evident on either the medial or lateral patellofemoral joint facet (medial, p = 0.600 and lateral, p = 0.950). Patients with abnormal patellar congruence and tilt angles (≥ 17° and ≥ 14°, respectively) reported good to excellent Kujala scores. Furthermore, lateral UKA resulted in improvements to patellofemoral alignment. Conclusion. This is the first study demonstrating that mild to moderate preoperative radiological degenerative changes and malalignment of the patellofemoral joint are not associated with poor patient-reported outcomes at mid-term follow-up after lateral fixed-bearing UKA. Our data suggest that this may be explained by realignment of the patella and thereby redistribution of loads across the patellofemoral joint. Cite this article: Bone Joint J 2020;102-B(6):727–735

Aims. Unicompartmental knee arthroplasty (UKA) provides improved early functional outcomes and less postoperative morbidity and pain compared with total knee arthroplasty (TKA). Opioid prescribing has increased in the last two decades, and recently states in the USA have developed online Prescription Drug Monitoring Programs to prevent overprescribing of controlled substances. This study evaluates differences in opioid requirements between patients undergoing TKA and UKA. Patients and Methods. We retrospectively reviewed 676 consecutive TKAs and 241 UKAs. Opioid prescriptions in morphine milligram equivalents (MMEs), sedatives, benzodiazepines, and stimulants were collected from State Controlled Substance Monitoring websites six months before and nine months after the initial procedures. Bivariate and multivariate analysis were performed for patients who had a second prescription and continued use. Results. Patients undergoing UKA had a second opioid prescription filled 50.2% of the time, compared with 60.5% for TKA (p = 0.006). After controlling for potential confounders, patients undergoing UKA were still less likely to require a second prescription than those undergoing TKA (adjusted odds ratio (OR) 0.58, 95% confidence interval (CI) 0.42 to 0.81; p = 0.001). Continued opioid use requiring more than five prescriptions occurred in 13.7% of those undergoing TKA and 5.8% for those undergoing UKA (p = 0.001), and was also reduced in UKA patients compared with TKA patients (adjusted OR 0.33, 95% CI 0.16 to 0.67; p = 0.022) in multivariate analysis. The continued use of opioids after six months was 11.8% in those undergoing TKA and 8.3% in those undergoing UKA (p = 0.149). The multivariate models for second prescriptions, continued use with more than five, and continued use beyond six months yielded concordance scores of 0.70, 0.86, and 0.83, respectively. Conclusion. Compared with TKA, patients undergoing UKA are less likely to require a second opioid prescription and use significantly fewer opioid prescriptions. Thus, orthopaedic surgeons should adjust their patterns of prescription and educate patients about the reduced expected analgesic requirements after UKA compared with TKA. Cite this article: Bone Joint J 2019;101-B(7 Supple C):22–27

Introduction: There has been a lack of general agreement on how successful unicompartmental knee arthroplasty has been. The purpose of this study is to report the results of revision total knee arthroplasties performed for failure of unicompartmental knee arthroplasty and to determine the factors that led to failure of the unicompartmental knee arthroplasty. Materials and method: Between September 1992 and June 1999, 12 knees(10 patients) among 106 primary unicompartmental knee arthroplasties, had revision of a failed unicompartmental knee arthroplasty. The average age of the patients was 61 years(range, 43 to 73 years). The average follow-up period was 3.6 years. Diagnosis before initial unicompartmental knee arthroplasty included osteoarthritis in eight patients and osteonecrosis in two patients. The medial compartment was involved in all knees. The type of prosthesis used in the 12 knees before revision was one Modular II, seven Microlocs and four Allegrettoes. The initial unicompartmental knee prosthetic components had been in place for an average of 4.3 years(range, 1, 2 to 7.5 years). The clinical findings were assessed using the Hospital for Special Surgery scoring system. Radiographic measurements were done with Bauer’s method. ANOVA test was used for statistical analysis. Results: The cause of revision was wear in six, loosening in five and one deep infection. The implant type used for revison was posterior stabilized type of Press Fit Condylar prosthesis. Eight knees had a bone defect at revision. Bone defects were filled with autogenous bone graft in six knees and metal wedges were used in two knees. At the last follow-up after revision, the average HSS knee score significantly improved from 58 to 83. And the Bauer’s angle was corrected from preoperative varus 6.3 degrees to valgus 6 degrees after revision. Radiographically, three knees had partial radiolucency. There was no complication such as postoperative hematoma, deep or superficial infection and peroneal nerve palsy. Conclusion: Good or excellent results were achieved in all of the knees after revision. Successful salvage of the failed UKA could be achieved by revision arthroplasty. The design of prosthesis, proper selection of patients, and surgical technique were important factors for succes of unicompartmental knee arthroplasty

Aim. There has been a significant reduction in unicompartmental knee arthroplasty (UKA) procedures recorded in Australia. This follows several national joint registry studies documenting high UKA revision rates when compared to total knee arthroplasty (TKA). With the recent introduction of robotically assisted UKA procedures, it is hoped that outcomes improve. This study examines the cumulative revision rate of UKA procedures implanted with a newly introduced robotic system and compares the results to one of the best performing non-robotically assisted UKA prostheses, as well as all other non-robotically assisted UKA procedures. Methods. Data from the Australian Orthopaedic Association National Joint Arthroplasty Registry (AOANJRR) for all UKA procedures performed for osteoarthritis (OA) between 2015 and 2018 were analyzed. Procedures using the Restoris MCK UKA prosthesis implanted using the Mako Robotic-Arm Assisted System were compared to non-robotically assisted Zimmer Unicompartmental High Flex Knee System (ZUK) UKA, a commonly used UKA with previously reported good outcomes and to all other non-robotically assisted UKA procedures using Cox proportional hazard ratios (HRs) and Kaplan-Meier estimates of survivorship. Results. There was no difference in the rate of revision when the Mako-assisted Restoris UKA was compared to the ZUK UKA (zero to nine months: HR 1.14 (95% CI 0.71 to 1.83; p = 0.596) vs nine months and over: HR 0.66 (95% CI 0.42 to 1.02; p = 0.058)). The Mako-assisted Restoris had a significantly lower overall revision rate compared to the other types of non-robotically assisted procedures (HR 0.58 (95% confidence interval (CI) 0.42 to 0.79); p < 0.001) at three years. Revision for aseptic loosening was lower for the Mako-assisted Restoris compared to all other non-robotically assisted UKA (entire period: HR 0.34 (95% CI 0.17 to 0.65); p = 0.001), but not the ZUK prosthesis. However, revision for infection was significantly higher for the Mako-assisted Restoris compared to the two comparator groups (ZUK: entire period: HR 2.91 (95% CI 1.22 to 6.98; p = 0.016); other non-robotically assisted UKA: zero to three months: HR 5.57 (95% CI 2.17 to 14.31; p < 0.001)). Conclusion. This study reports comparable short-term survivorship for the Mako robotically assisted UKA compared to the ZUK UKA and improved survivorship compared to all other non-robotic UKA. These results justify the continued use and investigation of this procedure. However, the higher rate of early revision for infection for robotically assisted UKA requires further investigation. Cite this article: Bone Joint J 2020;102-B(3):319–328

Abstract. Background. Daycase pathways which aim to discharge patients the same day following Unicompartmental Knee Replacement have been introduced in some centres, though most continue with Standard pathways. While Daycase pathways have cost savings, recovery data comparing pathways is limited. This study aims to compare patient-reported early recovery between Daycase and Standard pathways following UKR. Method. This study was carried out in two centres that originally used the same Standard recovery pathway for UKR. In one centre, the Standard pathway was modified into a Daycase pathway. 26 Daycase-Outpatient, 11 Daycase-Inpatient, and 18 Standard patients were recruited. Patients completed the Oxford Arthroplasty Early Recovery Score (OARS) and SF-36 (Acute) measure between Days 1–42. Results. Standard patients had significantly better Day-1 scores than Daycase patients, but this difference rapidly diminished, and from Day-3 onwards both groups had near-identical scores (OARS Day-1, 59 vs 37, p=0.002, stemming from differences in Pain, Nausea/Feeling-Unwell, Function/Mobility subscores p=0.003,0.014,0.011. OARS Day-3 48 vs 49, p=0.790). Daycase-Outpatients had a higher overall OARS (p=0.002), recovering 1–2 weeks faster than Daycase-Inpatients. OARS subscores demonstrated that Daycase-Outpatients had better Pain, Nausea/Feeling-Unwell, Fatigue/Sleep scores (p=0.020,0.0004,0.019 respectively). SF-36 scores corroborate OARS scores. Conclusion. The Standard cohort had better Day-1 scores than the Daycase cohort, likely due to later mobilisation and stronger inpatient analgesia; these differences diminished by Day-3. Daycase-Outpatients recovered substantially faster than Daycase-Inpatients – likely due to the factors that delayed their discharge. The convergence of scores at 6 weeks demonstrates that both pathways have similar early recovery outcomes

A retrospective study of one hundred and nineteen unicompartmental knee arthroplasties was performed. Outcome measures were the Oxford twelve-item knee questionnaire, the Short Musculoskeletal Functional Assessment (SMFA) and the WOMAC. Regression analysis was performed in order to determine predictors of outcome. After an average follow up period of four years, the mean scores indicated a good to excellent functional outcome. The only predictor of outcome identified was gender, with women obtaining a better functional outcome than men. Other variables that did not influence functional outcome included age, weight, stage of disease, previous HTO and bilateral procedures. The purpose of this study was to determine. the functional outcome of unicompartmental knee arthroplasty and. predictors of outcome. Although unicompartmental knee arthroplasty is becoming more widely accepted as a treatment option for degenerative osteoarthritis, there are very few studies in the literature that systematically investigate the predictors of outcome for this procedure. This is a retrospective study of one hundred and nineteen unicompartmental knee arthroplasties perfomed at a university hospital by a single surgeon. The outcome measures used were the Oxford twelve-item knee questionnaire, the Short Musculoskeletal Function Assessment (SMFA) and the Western Ontario and McMaster (WOMAC) functional indices. Multiple regression analysis was performed to determine predictors of outcome from chart derived variables. After a mean follow-up of four years the mean Oxford Knee Score was thirty-nine and the mean SMFA and WOMAC functional scores were eight and seven respectively, indicating a good to excellent functional outcome. Regression analysis revealed gender as a predictor of outcome however other variables including age (range 49–84 yrs), weight (range 55–225 kgs), previous ORIF, preoperative varus/valgus (range 0–16 degrees), joint subluxation (range 0–13mm), radiographic stage of disease (Kellgren and Lawrence), as well as previous HTO and bilateral (simultaneous or staged) unicompartmental knee arthroplasty were found to not correlate with functional outcome. Good to excellent functional outcome scores can be achieved with unicompartmental knee replacement. Previous HTO or bilateral procedures as well as weight, pre-operative varus/valgus < sixteen degrees or radiographic stage of disease were not predictive of outcome

Aims. The aim of this study was to assess the influence of obesity on the clinical outcomes and survivorship ten years postoperatively in patients who underwent a fixed-bearing unicompartmental knee arthroplasty (UKA). Patients and Methods. We prospectively followed 184 patients who underwent UKA between 2003 and 2007 for a minimum of ten years. A total of 142 patients with preoperative body mass index (BMI) of < 30 kg/m. 2. were in the control group (32 male, 110 female) and 42 patients with BMI of ≥ 30 kg/m. 2. were in the obese group (five male, 37 female). Pre- and postoperative range of movement (ROM), Knee Society Score (KSS), Oxford Knee Score (OKS), 36-Item Short-Form Health Survey (SF-36), and survivorship were analyzed. Results. Patients in the obese group underwent UKA at a significantly younger mean age (56.5 years (. sd. 6.4)) than those in the control group (62.4 years (. sd. 7.8); p < 0.001). There was no significant difference in preoperative functional scores. However, those in the obese group had a significantly lower ROM (116° (. sd. 15°) vs 123° (. sd. 17°); p = 0.003). Both groups achieved significant improvement in outcome scores regardless of BMI, ten years postoperatively. All patients achieved the minimal clinically important difference (MCID) for OKS and KSS. Both groups also had high rates of satisfaction (96.3% in the control group and 97.5% in the obese group) and the fulfilment of expectations (94.9% in the control group and 95.0% in the obese group). Multiple linear regression showed a clear association between obesity and a lower OKS two years postoperatively and Knee Society Function Score (KSFS) ten years postoperatively. After applying propensity matching, obese patients had a significantly lower KSFS, OKS, and physical component score (PCS) ten years postoperatively. Seven patients underwent revision to total knee arthroplasty (TKA), two in the control group and five in the obese group, resulting in a mean rate of survival at ten years of 98.6% and 88.1%, respectively (p = 0.012). Conclusion. Both groups had significant improvements in functional and quality-of-life scores postoperatively. However, obesity was a significant predictor of poorer improvement in clinical outcome and an increased rate of revision ten years postoperatively

Aims. Commonly performed unicompartmental knee arthroplasty (UKA) is not designed for the lateral compartment. Additionally, the anatomical medial and lateral tibial plateaus have asymmetrical geometries, with a slightly dished medial plateau and a convex lateral plateau. Therefore, this study aims to investigate the native knee kinematics with respect to the tibial insert design corresponding to the lateral femoral component. Methods. Subject-specific finite element models were developed with tibiofemoral (TF) and patellofemoral joints for one female and four male subjects. Three different TF conformity designs were applied. Flat, convex, and conforming tibial insert designs were applied to the identical femoral component. A deep knee bend was considered as the loading condition, and the kinematic preservation in the native knee was investigated. Results. The convex design, the femoral rollback, and internal rotation were similar to those of the native knee. However, the conforming design showed a significantly decreased femoral rollback and internal rotation compared with that of the native knee (p < 0.05). The flat design showed a significant difference in the femoral rollback; however, there was no difference in the tibial internal rotation compared with that of the native knee. Conclusion. The geometry of the surface of the lateral tibial plateau determined the ability to restore the rotational kinematics of the native knee. Surgeons and implant designers should consider the geometry of the anatomical lateral tibial plateau as an important factor in the restoration of native knee kinematics after lateral UKA. Cite this article: Bone Joint Res 2019;8:593–600

There has been significant interest in day-case and rapid discharge pathways for unicompartmental knee replacements (UKR). Pathways to date have shown this to be a safe and feasible option; however, no studies to date have published results of rapid-discharge pathways using the NAVIO robotic system. To date there is no published experience with rapid discharge UKR patients using the NAVIO robotic system. We report an initial experience of 11 patients who have safely been discharged within 24 hours. With the primary goal of investigating factors that led to rapid discharge and a secondary goal of evaluating the safety of doing so. All patients were discharged within 24 hours; there were no post-operative complications and no readmissions to hospital. The mean length of stay was 16.9 hours (SD=7.3), with most patients seen once on average by physiotherapy. Active range of motion at 6 weeks was 0.7o to 130.5 o, with all patients mobilising independently. The average 6-month post-operative Oxford Knee Score was 43.5 out of 48. There were no readmission or complications in any of our patients. This initial feasibility study identified that patients could be safely discharged within 24 hours after UKR using the NAVIO robotic system. With growing uptake of robotic procedures, with longer operative durations than traditional procedures, it is essential to ensure a rapid discharge to reduce healthcare cost whilst ensuring that patients are discharged home in a safe manner

Abstract. Background. The Oxford Domed Lateral (ODL) Unicompartmental Knee Replacement (UKR) has some advantages over other lateral UKRs, but the mobile bearing dislocation rate is high (1–6%). Medial dislocations, with the bearing lodged on the tibial component wall, are most common. Anterior/posterior dislocations are rare. For a dislocation to occur distraction of the joint is required. We have developed and validated a dislocation analysis tool based on a computer model of the ODL with a robotics path-planning algorithm to determine the Vertical Distraction required for a Dislocation (VDD), which is inversely related to the risk of dislocation. Objectives. To modify the ODL design so the risk of medial dislocation decreases to that of an anterior/posterior dislocation. Methods. The components were modified using Solidworks. For each modification the dislocation analysis tool was used to determine the VDD for medial dislocation (with bearing 0–6mm from the tibial wall). This was compared with the original implant to identify the modifications that were most effective at reducing the dislocation risk. These modifications were combined into a final design, which was assessed. Results. Modifying the tibial component plateau, changing the femoral component width and making the bearing wider medially had little effect on VDD. Shifting the femoral sphere centre medially decreased VDD. Shifting the femoral sphere laterally, increasing tibial wall height and increasing bearing width laterally increased VDD. A modified implant with a femoral sphere centre 3mm lateral, wall 2.8mm higher, and bearing 2mm wider laterally, implanted so the bearing is ≤4mm from the tibial wall with a bearing thickness ≥4mm had a minimum VDD for medial dislocation of 5.75mm, which is larger than the minimum VDD for anterior/posterior dislocation of 5.5mm. Conclusions. A modified ODL design should decrease the dislocation rate to an acceptable level, however, further testing in cadavers is required. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

We performed a prospective, randomised controlled trial of unicompartmental knee arthroplasty comparing the performance of the Acrobot system with conventional surgery. A total of 27 patients (28 knees) awaiting unicompartmental knee arthroplasty were randomly allocated to have the operation performed conventionally or with the assistance of the Acrobot. The primary outcome measurement was the angle of tibiofemoral alignment in the coronal plane, measured by CT. Other secondary parameters were evaluated and are reported. All of the Acrobot group had tibiofemoral alignment in the coronal plane within 2° of the planned position, while only 40% of the conventional group achieved this level of accuracy. While the operations took longer, no adverse effects were noted, and there was a trend towards improvement in performance with increasing accuracy based on the Western Ontario and McMaster Universities Osteoarthritis Index and American Knee Society scores at six weeks and three months. The Acrobot device allows the surgeon to reproduce a pre-operative plan more reliably than is possible using conventional techniques which may have clinical advantages

Unicompartmental knee arthroplasty (UKA) has numerous advantages over total knee arthroplasty (TKA) and one disadvantage, the higher revision rate. The best way to minimize the revision rate is for surgeons to use UKA for at least 20% of their knee arthroplasties. To achieve this, they need to learn and apply the appropriate indications and techniques. This would decrease the revision rate and increase the number of UKAs which were implanted, which would save money and patients would benefit from improved outcomes over their lifetime. Cite this article: Bone Joint J 2018;100-B:432–5

The treatment of medial knee osteoarthritis (OA) in conjunction with anterior knee laxity is an issue of debate. Current treatment options include knee joint distraction, unicompartmental knee replacement (UKR) or high tibial osteotomy with anterior cruciate ligament (ACL) reconstruction or total knee replacement. Bone-conserving options are preferred for younger and active patients with intact lateral and patello-femoral compartment. However, still limited experience exists in the field of combining medial UKR and ACL reconstruction. The aim of this study is to retrospectively evaluate the results of combined fixed-bearing UKR and ACL reconstruction, specifically with regard to patient satisfaction, activity level, and postoperative functional outcomes. The hypothesis was that this represents a safe and viable procedure leading to improved stability and functional outcome in patients affected by isolated unicompartmental OA and concomitant ACL deficiency. Fourteen patients with ACL deficiency and concomitant medial compartment symptomatic osteoarthritis were treated from 2006 to 2010. Twelve of them were followed up for an average time of 7.8 year (range 6–10 years). Assessment included Knee Osteoarthritis Outcome Score (KOOS), Oxford Knee score (OKS), American Knee Society scores (AKSS), WOMAC index of osteoarthritis, Tegner activity level, objective examination including instrumented laxity test with KT-1000 arthrometer and standard X-rays. Wilcoxon test was utilized to compare the pre-operative and follow-up status. Differences with a p value <0.05 were considered statistically significant. KOOS score, OKS, WOMAC index and the AKSS improved significantly at follow-up (p < 0.05). There was no clinical evidence of instability in any of the knees as evaluated with clinical an instrumented laxity testing (p < 0.05). No pathologic radiolucent lines were observed around the components. In one patient a total knee prosthesis was implanted due to the progression of signs of osteoarthritis in the lateral compartment 3 years after primary surgery. UKR combined with ACL reconstruction is a valid therapeutic option for young and active patients with a primary ACL injury who develop secondary OA and confirms subjective and objective clinical improvement up to 8 years after surgery

Aims. The purpose of this multicentre observational study was to investigate the association between intraoperative component positioning and soft-tissue balancing on short-term clinical outcomes in patients undergoing robotic-arm assisted unicompartmental knee arthroplasty (UKA). Patients and Methods. Between 2013 and 2016, 363 patients (395 knees) underwent robotic-arm assisted UKAs at two centres. Pre- and postoperatively, patients were administered Knee Injury and Osteoarthritis Score (KOOS) and Forgotten Joint Score-12 (FJS-12). Results were stratified as “good” and “bad” if KOOS/FJS-12 were more than or equal to 80. Intraoperative, post-implantation robotic data relative to CT-based components placement were collected and classified. Postoperative complications were recorded. Results. Following exclusions and losses to follow-up, 334 medial robotic-arm assisted UKAs were assessed at a mean follow-up of 30.0 months (8.0 to 54.9). None of the measured parameters were associated with overall KOOS outcome. Correlations were described between specific KOOS subscales and intraoperative, post-implantation robotic data, and between FJS-12 and femoral component sagittal alignment. Three UKAs were revised, resulting in 99.0% survival at two years (95% confidence interval (CI) 97.9 to 100.0). Conclusion. Although little correlation was found between intraoperative robotic data and overall clinical outcome, surgeons should consider information regarding 3D component placement and soft-tissue balancing to improve patient satisfaction. Reproducible and precise placement of components has been confirmed as essential for satisfactory clinical outcome. Cite this article: Bone Joint J 2019;101-B:435–442

Aims. The purpose of this study was to evaluate trends in opioid use after unicompartmental knee arthroplasty (UKA), to identify predictors of prolonged use and to compare the rates of opioid use after UKA, total knee arthroplasty (TKA) and total hip arthroplasty (THA). Materials and Methods. We identified 4205 patients who had undergone UKA between 2007 and 2015 from the Humana Inc. administrative claims database. Post-operative opioid use for one year post-operatively was assessed using the rates of monthly repeat prescription. These were then compared between patients with and without a specific variable of interest and with those of patients who had undergone TKA and THA. Results. A total of 4205 UKA patients were analysed. Of these, 1362 patients (32.4%) were users of opioids. Pre-operative opioid use was the strongest predictor of prolonged opioid use after UKA. Opioid users were 1.4 (81.6% versus 57.7%), 3.7 (49.5% versus 13.3%) and 5.5 (35.8% versus 6.5%) times more likely to be taking opioids at one, two and three months post-operatively, respectively (p < 0.05 for all). Younger age and specific comorbidities such as anxiety/depression, smoking, back pain and substance abuse were found to significantly increase the rate of repeat prescription for opioids after UKA. Overall, UKA patients required significantly less opioid prescriptions than patients who had undergone THA and TKA. Conclusion. One-third of patients who undergo UKA are given opioids in the three months pre-operatively. Pre-operative opioid use is the best predictor of increased repeat prescriptions after UKA. However, other intrinsic patient characteristics are also predictive. Cite this article: Bone Joint J 2018;100-B(1 Supple A):62–7

Multiple reports suggest good outcome results following unicompartmental knee replacement (UKR). However, several authors report technically difficult revision surgery secondary to osseous defects. We reviewed clinical outcomes following revision total knee replacement for failed UKR and analysed the reasons for failure and the technical aspects of the revision surgery. Between 2003 and 2009, thirty three revisions from unicompartmental knee replacement to total knee replacement were performed in thirty two patients at a single centre. Demographics, indications for the primary and revision procedures, details of the revised prosthesis including augments and any technical difficulties or complications were noted. Patient assessment included range of motion and the functional status of the affected knee in the form of the Oxford knee score questionnaire. Statistical analysis was performed with the Student t test. All 33 revision knees were available for prospective clinical and radiological follow-up. The minimum duration of follow-up after revision surgery was 1 year (mean 3 years, range 1 – 7 years). The median interval between the original unicompartmental knee replacements to revision surgery was 19 months (range 2 – 159 months). The predominant cause of failure was aseptic loosening (50%). Other reasons included persistent pain (21%), dislocated meniscus (18%), mal-alignment (7%) and progression of symptomatic osteoarthritis in another compartment (4%). 18 of the 33 revision procedures required additional augments. During the revision surgery, 11 knees required a long tibial stem while 1 required a long femoral stem. 10 knees required medial tibial wedge augmentation; bone graft was used in 6 knees while a metal wedge augment was used in 4 to fill significant osseous defects. At the time of follow-up, range of movement averaged 103 degrees (range 70 – 120). The mean one year Oxford knee score, was 29 compared to 39 for primary total knee replacements performed during the same period in a comparable sample group of patients at our institute (p < 0.001). Three patients continued to have pain and two required re-revision; one for infection and one for loosening. Aseptic loosening was the commonest mode of failure. Of the UKRs revised to TKRs, 90% were revised within 5 years. The majority of revisions required additional constructs. Oxford Knee Scores after revision surgery were inferior to those for primary TKR. The role of UKR needs to be more clearly defined

Introduction. The efficacy of Virtual Reality (VR) as a teaching augment for arthroplasty has not been well examined for unfamiliar multistep procedures such as unicompartmental knee arthroplasty (UKA). This study sought to determine if VR improves surgical competence over traditional procedural preparation when performing a UKA. Methods. 22 Orthopaedic trainees were randomized to training sessions: 1) “VR group” with access to an immersive VR learning module that had been designed in conjunction with the manufacturer or 2) “Guide group” with access to manufacture's technique guide and surgical video. Both groups then performed a full UKA on SawBones models. Surgical competence was assessed via Objective Structures Assessment of Technical Skills (OSATS) validated rating system (max 25 points). Results. Participants equally distributed all training levels between groups. There was no difference in surgical times between VR and Guide groups (VR=43.0 vs Guide=42.4 mins; p=0.9). There was no difference in total OSATS score between groups (VR=14.2 vs Guide=15.7; p=0.59). There was also no difference between groups when sub-analysis was performed by training level. Most felt VR would be a useful tool for resident education (77%) and reported a likeliness to utilize VR for case preparation if available (86.4%). Conclusion. In a randomized controlled trial for trainees performing a complex, unfamiliar procedure (UKA), VR training demonstrated equivalent surgical competence to traditional technique guides and videos. Despite this, the majority of trainees find the technology beneficial and would use it if available. This project suggests as currently constructed, VR should be incorporated as an adjunct, rather than a replacement, to traditional surgical preparation/training methods

In recent years, reduction in the length of stay in patients undergoing UKA has gained considerable interest. This has led to development of ‘fast-track' and even day-case protocols aimed at decreasing length of stay (LOS), enhancing post-operative recovery and decreasing post-operative morbidity. One potential barrier to faster discharge and patient recovery is the need for post-operative haemoglobin checks and allogenic blood transfusion; which has been shown to increase LOS. Allogenic blood transfusion itself is not without risk, including immunological reactions, transfusion associated lung injury, infection and transmission of disease, thus reducing blood loss and the need for transfusion is imperative. Currently there is a knowledge gap regarding post-operative transfusion need and blood loss following UKA. We aimed to investigate blood loss and transfusion rates following UKA. Our primary aim was to evaluate the extent of post-operative transfusion need following UKA and identify which patients are at higher risk of needing transfusion. Following institutional approval, a retrospective analysis of all patients undergoing unicompartmental knee arthroplasty (UKA) at our level one academic university hospital was conducted. Operative records of all patients undergoing primary UKA were reviewed between March 2016 and March 2019. Patients' pre-operative haemoglobin and haematocrit, BMI, co-morbidities, application of tourniquet, tourniquet time, administration of Tranexamic Acid, need for post-operative blood transfusion, hospital length of stay, complications and re-admission were all recorded. Blood loss was estimated using the post-operative haematocrit. A total number of 155 patients were included. There were 70 females (45%) and 85 males (55%). The mean age was 66±10 years. Median pre-op blood volume was 4700mls (IQR; 4200–5100). Median blood loss was 600 mls (IQR; 400–830). Mean pre-op Haemoglobin was 135±14g/L and mean post-op Haemoglobin was 122±13g/L. No patient had a post-op Haemoglobin under 80g/L (Range 93–154). No patients in our study needed transfusion. A further comparison group of high-blood loss and low-blood loss patients was included in analysis. High-blood loss patients were defined as those losing greater than 20% of their pre-operative blood volume whilst low-blood loss patients were defined as those losing ≤20% of their blood volume. Results of these groups are presented in Table 3. No significance was found between the two groups in patient's demographics and in terms of intra-operative factors including TXA usage (p=0.68) and tourniquet time (p=0.99). There was no difference in terms of post-operative complications (p=1.0), length of stay (p=0.36) or readmission rates (p=0.59). The results of our study indicated that post-operative haemoglobin and haematocrit check proved unnecessary in all of our patients and could have been omitted from post-operative routines. We conclude that routine post UKA check of haemoglobin and haematocrit can be avoided and be saved for special circumstances depending on patient's physiology

Introduction:. Unicompartmental knee arthroplasty (UKA) is a well established method for treatment of single compartment arthritis. However, a subset of patients still present with continued pain after their procedure in the setting of a normal radiographic examination. We propose the use of magnetic resonance imaging (MRI) as a useful modality in determining the etiology of symptoms in symptomatic unicompartmental knee arthroplasties. Materials & Methods:. An IRB-approved retrospective analysis of 300 consecutive unicompartmental knee arthroplasties between 2008–2010 found 28 cases symptomatic for continued pain. Magnetic resonance imaging was performed with a 1.5 T Surface Coil unit after clinical and radiographic assessment. MRI evaluation included assessment for osteoarthritis, synovitis, osteolysis, and loosening. Validated questionnaires including PAQ, WOMAC and UCLA Activity Score were used for clinical assessment. Results:. The average age at surgery was 56.1 ± 10.9 years (34–79). Imaging results indicated progressive arthritis in 28 patients (100%), synovitis in 17 patients (61%), osteolysis in 9 patients (32.0%), and loosening in 3 patients (11%). Based on these results and other clinical findings, a revision or conversion to a TKR was advised for 10 patients and 18 were recommended for nonoperative therapies. One patient received treatment at a separate hospital, and another was lost to follow-up. At post-operative follow-up of 1.4 ± 0.9 years, 7 of the 10 patients (70%) in the operative group experienced improvement in pain and function. The mean PAQ, UCLA and WOMAC index scores for these patients were 8.0 ± 1.4 (7–9), 5.5 ± 6.4 (1–10), and 2.0 ± 2.8 (0–4), respectively. In the nonoperative group, 11 of the 18 patients (61%) experienced improvement in pain and function. Among these patients, the mean PAQ, UCLA and WOMAC index scores were 7.6 ± 3.7 (0–10), 5.9 ± 3.2 (1–10) and 8.9 ± 12.0 (0–28), respectively. Conclusion:. The use of MRI as an imaging modality for symptomatic arthroplasty patients is becoming more commonly used. This study shows how MRI with sound clinical judgment can influence treatment decisions and supports the use of high quality MRI as a diagnostic tool for the symptomatic unicompartmental knee arthroplasty

Unicompartmental knee arthroplasty (UKA) was first described over 30 years ago and allows replacement of a single compartment in patients who have isolated osteoarthritis. However, UKA is more technically challenging than total knee arthroplasty due to limited exposure as a minimally invasive procedure. In addition to component alignment and fixation, ligament balancing plays an important role in implant survival. Some failures of early UKA systems were attributed to a failure to adequately balance the knee. The development of robots to aid in performing the procedure has lead to renewed interest in this surgical technique. The use of a robot-assisted system allows the orthopaedic surgeon to verify that balancing sought pre-operatively correlates with that obtained at surgery. Some studies have shown good post-operative mechanical alignment utilizing this method. The aim of this study was to examine the variation in pre-operative templated ligament balance and that obtained during the operation. Data were prospectively collected on 51 patients (52 knees) undergoing robot-assisted unicompartmental knee arthroplasty by a single surgeon. For pre-operative planning, dynamic ligament balancing was obtained of the operative knee under valgus stress, prior to any bony cuts. Final intra-operative images with the prosthesis in place were taken without valgus stress. Positive values denoted loose ligamentous balancing while negative values indicated ligament tightness. A small variation of less than 1 mm was measured between the pre-operative plan and the final image with the implant in place. At 0 degrees the mean change was −0.26 mm (range, −4.40 to 2.20 mm), at 30 degrees −0.53 mm (range, −5.30 to 1.80 mm), at 60 degrees −0.04 mm (range, −3.10 to 2.30 mm) and at 90 degrees 0.16 mm (range, −2.70 to 2.00 mm). These results show that planned dynamic ligament balancing is accurate to within 0.52 mm. The technological advancements with robotic feedback in orthopaedic surgery can aid in the success of unicompartmental knee replacement surgery. Ensuring that pre-operative templated changes match those performed during surgery is an important predictor of outcome. With proper planning prior to surgery, the use of a robot in UKA can improve ligament balancing. This can be done at various angles, ensuring excellent ligament balancing throughout the entire range of motion. Correct component alignment reduces the risk of prosthetic failure and may increase the length of implant survival. Further fine-tuning of the accuracy of feedback between the robot and the anatomical points will improve the accuracy of UKA

Introduction. Unicompartmental knee arthroplasty (UKA) was first described over 30 years ago and allows replacement of a single compartment in patients who have isolated osteoarthritis. 1. However, UKA is more technically challenging than total knee arthroplasty due to limited exposure as a minimally invasive procedure. In addition to component alignment and fixation, ligament balancing plays an important role in implant survival. 2. Some failures of early UKA systems were attributed to a failure to adequately balance the knee. The development of robots to aid in performing the procedure has lead to renewed interest in this surgical technique. The use of a robot-assisted system allows the orthopaedic surgeon to verify that balancing sought pre-operatively correlates with that obtained at surgery. Some studies have shown good post-operative mechanical alignment utilizing this method. 3. The aim of this study was to examine the variation in pre-operative templated ligament balance and that obtained during the operation. Methods. Data were prospectively collected on 52 patients (51 knees) undergoing robot-assisted unicompartmental knee arthroplasty by a single surgeon. For pre-operative planning, dynamic ligament balancing was obtained of the operative knee under valgus stress, prior to any bony cuts. Final intra-operative images with the prosthesis in place were taken without valgus stress. Positive values denoted loose ligamentous balancing while negative values indicated ligament tightness. Results. A small variation of less than 1 mm was measured between the pre-operative plan and the final image with the implant in place. At 0 degrees the mean change was −0.26 mm (range, −4.40 to 2.20 mm), at 30 degrees −0.53 mm (range, −5.30 to 1.80 mm), at 60 degrees −0.04 mm (range, −3.10 to 2.30 mm) and at 90 degrees 0.16 mm (range, −2.70 to 2.00 mm). These results show that planned dynamic ligament balancing is accurate to within 0.52 mm. Conclusion. The technological advancements with robotic feedback in orthopaedic surgery can aid in the success of unicompartmental knee replacement surgery. Ensuring that pre-operative templated changes match those performed during surgery is an important predictor of outcome. With proper planning prior to surgery, the use of a robot in UKA can improve ligament balancing. This can be done at various angles, ensuring excellent ligament balancing throughout the entire range of motion. Correct component alignment reduces the risk of prosthetic failure and may increase the length of implant survival. Further fine-tuning of the accuracy of feedback between the robot and the anatomical points will improve the accuracy of UKA

Aims. The objectives of this study were to compare postoperative pain, analgesia requirements, inpatient functional rehabilitation, time to hospital discharge, and complications in patients undergoing conventional jig-based unicompartmental knee arthroplasty (UKA) versus robotic-arm assisted UKA. Patients and Methods. This prospective cohort study included 146 patients with symptomatic medial compartment knee osteoarthritis undergoing primary UKA performed by a single surgeon. This included 73 consecutive patients undergoing conventional jig-based mobile bearing UKA, followed by 73 consecutive patients receiving robotic-arm assisted fixed bearing UKA. All surgical procedures were performed using the standard medial parapatellar approach for UKA, and all patients underwent the same postoperative rehabilitation programme. Postoperative pain scores on the numerical rating scale and opiate analgesia consumption were recorded until discharge. Time to attainment of predefined functional rehabilitation outcomes, hospital discharge, and postoperative complications were recorded by independent observers. Results. Robotic-arm assisted UKA was associated with reduced postoperative pain (p < 0.001), decreased opiate analgesia requirements (p < 0.001), shorter time to straight leg raise (p < 0.001), decreased number of physiotherapy sessions (p < 0.001), and increased maximum knee flexion at discharge (p < 0.001) compared with conventional jig-based UKA. Mean time to hospital discharge was reduced in robotic UKA compared with conventional UKA (42.5 hours (. sd 5.9). vs 71.1 hours (. sd. 14.6), respectively; p < 0.001). There was no difference in postoperative complications between the two groups within 90 days’ follow-up. Conclusion. Robotic-arm assisted UKA was associated with decreased postoperative pain, reduced opiate analgesia requirements, improved early functional rehabilitation, and shorter time to hospital discharge compared with conventional jig-based UKA

The purpose of this study was to measure the radiological parameters of femoral component alignment of the Oxford Phase 3 unicompartmental knee replacement (UKR), and evaluate their effect on clinical outcome. Multiple regression analysis was used to examine the relative contributions of the radiological assessment of femoral component alignment in 189 consecutive UKRs performed by a single surgeon. The American Knee Society scores were compared between groups, defined as being within or outside recommended tolerances of the position of the femoral component. For the flexion/extension position 21 UKRs (11.1%) lay outside the recommended limits, and for posterior overhang of the femoral component nine (4.8%) lay outside the range. The pre-operative hip/knee/ankle (HKA) angle, narrowest canal distance from the distal femoral entry point of the alignment jig and coronal entry-point position had significant effects on the flexion/extension position. Pre-operative HKA angle had a significant influence on posterior overhang of the femoral component. However, there was no significant difference in American Knee Society scores relative to the position of the femoral component

Medium-term survivorship of the Oxford phase 3 unicompartmental knee replacement (UKR) has not yet been established in an Asian population. We prospectively evaluated the outcome of 400 phase 3 Oxford UKRs in 320 Korean patients with a mean age at the time of operation of 69 years (48 to 82). The mean follow-up was 5.2 years (1 to 10). Clinical and radiological assessment was carried out pre- and post-operatively. At five years, the mean Knee Society knee and functional scores had increased significantly from 56.2 (30 to 91) pre-operatively to 87.2 (59 to 98) (p = 0.034) and from 59.2 (30 to 93) to 88.3 (50 to 100) (p = 0.021), respectively. The Oxford knee score increased from a mean of 25.8 (12 to 39) pre-operatively to 39.8 (25 to 58) at five years (p = 0.038). The ten-year survival rate was 94% (95% confidence interval 90.1 to 98.0). A total of 14 UKRs (3.5%) required revision. The most common reason for revision was dislocation of the bearing in 12 (3%). Conversion to a total knee replacement was required in two patients who developed osteoarthritis of the lateral compartment. This is the largest published series of UKR in Korean patients. It shows that the mid-term results after a minimally invasive Oxford phase 3 UKR can yield satisfactory clinical and functional results in this group of patients

Objectives. Up to 40% of unicompartmental knee arthroplasty (UKA) revisions are performed for unexplained pain which may be caused by elevated proximal tibial bone strain. This study investigates the effect of tibial component metal backing and polyethylene thickness on bone strain in a cemented fixed-bearing medial UKA using a finite element model (FEM) validated experimentally by digital image correlation (DIC) and acoustic emission (AE). Materials and Methods. A total of ten composite tibias implanted with all-polyethylene (AP) and metal-backed (MB) tibial components were loaded to 2500 N. Cortical strain was measured using DIC and cancellous microdamage using AE. FEMs were created and validated and polyethylene thickness varied from 6 mm to 10 mm. The volume of cancellous bone exposed to < -3000 µε (pathological loading) and < -7000 µε (yield point) minimum principal (compressive) microstrain and > 3000 µε and > 7000 µε maximum principal (tensile) microstrain was computed. Results. Experimental AE data and the FEM volume of cancellous bone with compressive strain < -3000 µε correlated strongly: R = 0.947, R. 2. = 0.847, percentage error 12.5% (p < 0.001). DIC and FEM data correlated: R = 0.838, R. 2. = 0.702, percentage error 4.5% (p < 0.001). FEM strain patterns included MB lateral edge concentrations; AP concentrations at keel, peg and at the region of load application. Cancellous strains were higher in AP implants at all loads: 2.2- (10 mm) to 3.2-times (6 mm) the volume of cancellous bone compressively strained < -7000 µε. Conclusion. AP tibial components display greater volumes of pathologically overstrained cancellous bone than MB implants of the same geometry. Increasing AP thickness does not overcome these pathological forces and comes at the cost of greater bone resection. Cite this article: C. E. H. Scott, M. J. Eaton, R. W. Nutton, F. A. Wade, S. L. Evans, P. Pankaj. Metal-backed versus all-polyethylene unicompartmental knee arthroplasty: Proximal tibial strain in an experimentally validated finite element model. Bone Joint Res 2017;6:22–30. DOI:10.1302/2046-3758.61.BJR-2016-0142.R1

Aims. The interest in unicompartmental knee arthroplasty (UKA) for medial osteoarthritis has increased rapidly but the long-term follow-up of the Oxford UKAs has yet to be analysed in non-designer centres. We have examined our ten- to 15-year clinical and radiological follow-up data for the Oxford Phase III UKAs. Patients and Methods. Between January 1999 and January 2005 a total of 138 consecutive Oxford Phase III arthroplasties were performed by a single surgeon in 129 patients for medial compartment osteoarthritis (71 right and 67 left knees, mean age 72.0 years (47 to 91), mean body mass index 28.2 (20.7 to 52.2)). Both clinical data and radiographs were prospectively recorded and obtained at intervals. Of the 129 patients, 32 patients (32 knees) died, ten patients (12 knees) were not able to take part in the final clinical and radiological assessment due to physical and mental conditions, but via telephone interview it was confirmed that none of these ten patients (12 knees) had a revision of the knee arthroplasty. One patient (two knees) was lost to follow-up. Results. The mean follow-up was 11.7 years (10 to 15). A total of 11 knees (8%) were revised. The survival at 15 years with revision for any reason as the endpoint was 90.6% (95% confidence interval (CI) 85.2 to 96.0) and revision related to the prosthesis was 99.3% (95% CI 97.9 to 100). The mean total Knee Society Score was 47 (0 to 80) pre-operatively and 81 (30 to 100) at latest follow-up. The mean Oxford Knee Score was 19 (12 to 40) pre-operatively and 42 (28 to 55) at final follow-up. Radiolucency beneath the tibial component occurred in 22 of 81 prostheses (27.2%) without evidence of loosening. Conclusion. This study supports the use of UKA in medial compartment osteoarthritis with excellent long-term functional and radiological outcomes with an excellent 15-year survival rate. Cite this article: Bone Joint J 2016;98-B(10 Suppl B):41–7

Unicompartmental knee arthroplasty has been in use since the 1970s. In spite of early enthusiasm, the procedure soon fell into disfavour, particularly in the USA. Early failures were a result of improper indication, poor technique and in some cases and poor prosthetic design. A new instrument system for use with the MG unicompartmental knee arthroplasty has been designed, with guides for accurate and reproducible alignment, sizing and resection. Potential benefits include early mobilisation, rapid rehabilitation, improved range of motion and shortened hospital stay. This paper briefly reviews the literature and discusses indications and surgical techniques

Introduction:. Isolated lateral compartment osteoarthritis (OA) occurs in 5–10% of knees with unicompartmental OA. Lateral unicompartmental knee arthroplasty has been limited in its prevalence due to challenging surgical technique issues. A robotic-arm assisted surgical technique has emerged as a way to achieve precise implant positioning which can potentially improve surgical outcomes. Methods:. 63 consecutive lateral unicompartmental knee arthroplasties were performed by a single surgeon with the use of a metal backed, cemented prosthesis installed with the three-dimensional intra-operative kinematics and haptic robotic guidance. The average age of the patient was 72.7 years (range: 59–87) and the average BMI was 27.2 (range: 19.0–38.6). The follow-up ranged from 2 months to 30 months. Results:. All patients recovered flexion to an average of 130° at 6 weeks post-operatively, compared to an average of 127° pre-operatively. There was one revision to a total knee at 26 months post-operatively for progression of OA to the patellofemoral compartment. Conclusion:. Early results of robotically guided lateral UKA are encouraging and provide evidence to show that lateral UKA is a viable option for patients with lateral OA disease. Three dimensional planning, intra-operative kinematic analysis and haptic robotic guidance provide a significant advantage over manual installation for lateral compartment arthroplasty of the knee. The significant anterior to posterior translation of the lateral femoral condyle along with the “screw-home” mechanism associated with the lateral compartment makes the tracking of the lateral compartment highly complex when retaining the cruciate ligaments. Intraoperative planning and adjustment of the preoperative plan provided only with this robotic system results in optimized lateral compartment kinematics. Further mid to long term studies are needed to determine survivorship as it compares to medial unicompartmental knee arthroplasty

Unicompartmental knee arthroplasty remains controversial in some quarters and has been subject to recent negative press. The aim of the present study was to determine the differences in pre-operative status and early post-operative improvement between patients having unicompartmental knee Replacement (UKR) and Total Knee Replacement (TKR). Methods: A Prospective study. Ethical approval was obtained prior to the study. Patients undergoing knee arthroplasty by two orthopaedic surgeons were included. Decision to proceed to unicompartmental or total knee replacement was at the surgeons’ discretion and was not randomised. The Oxford and the Ameri-can Knee Society scores were used to assess outcome. (Oxford score was used as a 0–48 scale; 0 being better and 48 worse). Scores were documented pre-operatively and at six weeks post-operatively. Results: 104 patients were included in the study. 84 patients had TKR and 20 patients had UKR. Patients under going TKR had significantly worse Oxford, knee and function scores pre-operatively (32.2, 29.2 and 39.6) as compared with the UKR patients (28.5, 40.5 and 46.7) (P= 0.03, 0.001 and 0.026 respectively). TKR was associated with greater improvements in Oxford (P= 0.025), knee (P=0.0.027) and function (p=0.06) scores. However, the post operative scores were comparable; 20.4, 78.9 and 58.7 for TKR and 20.7, 80.9 and 57.9 for UKR. Conclusions: It could perhaps be expected that patients with unicompartmental disease would have better pre-operative knee status than patients with more advanced multicompartmental disease. It is therefore understandable that patients receiving total knee replacements are able to improve more post-operatively than those receiving unicompartmental devices. Unicompartmental knees achieve only marginal initial superiority in terms of knee scores at 6 weeks follow-up. This is important and if clinical superiority and prosthesis longevity are not proven at longer term follow-up it would question the use of unicompartmental arthroplasty

The Oxford mobile bearing unicompartmental knee replacement (UKR) is a validated, highly successful implant with an excellent ten-year survivorship. From November 2001 to September 2006 three hundred and eighty two patients who had a medial cemented Oxford Unicompartmental knee replacement (Biomet, Bridgend, UK) via a minimally invasive approach were prospectively entered into a database and followed up as per departmental policy in the specialist joint assessment clinic. We have noted a minority of patients have persistent postoperative pain and/or mechanical symptoms resistant to the standard postoperative therapies. We report the outcome of 22 patients who had an arthroscopy for persistent pain and/or mechanical symptoms a median of 15 months (range 4 months – 31 months) following medial unicompartmental knee replacement. The median follow up time following arthroplasty was 38 months (range 16 months – 63 months). Post arthroscopy we divided our study patients into two groups; those who had an improvement in symptoms and those who had none. These groups were then compared, with particular reference to demographics, check radiographs and arthroscopic findings. The results showed that patients with anterior or anteromedial symptoms in whom a medial rim of scar tissue was identified and debrided sixty seven percent had a significantly increased probability of symptomatic improvement (p<0.005). In addition men appeared to significantly improve more that women (p<0.043). When performed this therapeutic intervention many prevent or at least defer the need for early revision to total knee replacement in some cases and we have no complications as a result of the arthroscopic intervention. This observational study provides evidence for a role for arthroscopy in selected patients with pain following unicompartmental knee replacement

Introduction & aims. Patient specific instrumentation (PSI) is a useful tool to execute pre-operatively planned surgical cuts and reduce the number of trays in surgery. Debate currently exists around improved accuracy, efficacy and patient outcomes when using PSI cutting guides compared to conventional instruments. Unicompartmental Knee Arthroplasty (UKA) revision to Total Knee Arthroplasty (TKA) represents a complex scenario in which traditional bone landmarks, and patient specific axes that are routinely utilised for component placement may no longer be easily identifiable with either conventional instruments or navigation. PSI guides are uniquely placed to solve this issue by allowing detailed analysis of the patient morphology outside the operating theatre. Here we present a tibia and femur PSI guide for TKA on patients with UKA. Method. Patients undergoing pre-operative planning received a full leg pass CT scan. Images are then segmented and landmarked to generate a patient specific model of the knee. The surgical cuts are planned according to surgeon preference. PSI guide models are planned to give the desired cut, then 3D printed and provided along with a bone model in surgery. PSI-bone and PSI-UKA contact areas are modified to fit the patient anatomy and allow safe placement and removal. The PSI-UKA contact area on the tibia is defined across the UKA tibial tray after the insert has been removed. Further contact is planned on the tibial eminence if it can be accurately segmented in the CT and the anterior superior tibia on the contralateral compartment, see example guide in Figure 1. Contact area on the femur is defined on the superior trochlear groove, native condyle, femur centre and femoral UKA component if it can be accurately segmented in the CT. Surgery was performed with a target of mechanical alignment using OMNI APEX PS implants (Raynham, MA). The guide was planned such that the OMNI cut block could be placed on the securing pins to translate the cut. Component alignment and resections values were calculated by registering the pre-operative bones and component geometries to post-operative CT images. Results. Four UKA to TKA surgeries have been performed using revision PSI guides. The maximum difference from planned to achieved component alignments are: Femoral valgus = 2.4â□°, Tibial varus = 2.5â□°, Femoral internal rotation = 3.6â□°, Femoral flexion = 5.1â□° and tibial slope = 2.9â□°, see boxplot of results in Figure 2. All median values are within 2.5â□° of the planned alignment. A further five cases are to be analysed. Conclusions. A PSI guide designed for UKR to TKR revision surgery has been successfully used in surgery with acceptable errors. A larger study must be performed to determine the reliability and reproducibility of the design and method over a wide range of patient anatomy and UKA imaging flare

INTRODUCTION. Unicompartmental knee arthroplasty (UKA) is considered a highly successful procedure. However, complications and revisions may still occur, and some may be related to the operative technique. Computer assistance has been suggested to improve the accuracy of implantation of a UKA. The present study was designed to evaluate the long-term (more than 10 years) results of an UKA which was routinely implanted with help of a non-image based navigation system. MATERIAL AND METHODS. All patients operated on between 2004 and 2005 for implantation of a navigated UKA were included. Usual demographic and peri-operative items have been record. All patients were prospectively followed with clinical and radiological examination. All patients were contacted after the 10 year follow-up for repeat clinical and radiological examination (KSS, Oxford knee questionnaire and knee plain X-rays). Patients who did not return were interviewed by phone call. For patients lost of follow-up, family or general practitioner was contacted to obtain relevant information about prosthesis survival. Survival curve was plotted according to Kaplan-Meier. RESULTS. 57 UKAs were implanted during the study time-frame. Final follow-up (including death or revision) was obtained for 50 cases (88%). Clinical status after 10 years was obtained for 45 cases (80%). 4 prosthetic revisions were performed for mechanical reasons during the follow- up time (7%). The 10 year survival rate was 94%. No component was considered loose at the final radiographic evaluation. No polyethylene wear was detected at the final radiographic evaluation. DISCUSSION. This study confirms our initial hypothesis, namely quite satisfactory results of a navigated implanted UKA after more than 10 years. Navigation, whose precision is no longer to be demonstrated, probably contributed to the quality of the results. A more consistent anatomical reconstruction and ligamentous balance of the knee should lead to more consistent survival of the UKA. However, superiority of navigated UKA in comparison to conventional implanted UKA is difficult to prove because of the subtle differences expected in mostly underpowered studies. Longer term follow-up may be required

Introduction: Unicompartmental knee arthroplasty (UKA) remains a cost effective option for treatment of medial compartment osteoarthritis of the knee. In carefully selected patients survival rates exceed 90% survivorship at ten years. Main indications for revision include progressive osteoarthritis in other compartments, component loosening and polyethylene bearing failure. However, within those patients who have been revised, there is a cohort of patients who are revised early, usually under seven years. Mechanical mal-alignment has been cited recently as a reason for early failure and revision. The introduction of computer assisted surgery (CAS) has allowed us to more accurately restore the normal mechanical axis of the limb in UKA. Aims and Hypothesis: The aim of this study was to identify whether, within our cohort of early failures, the failure mechanism differed from patients in the late revision group and specifically to examine whether mechanical mal-alignment contributed to the mechanism of early failure. Materials and Methods: We undertook this retrospective review of a single surgeon series of 87 revised unicompartmental knee replacements carried out over 15 years. We collated the indications for revision, mechanisms of failure, and methods of revision from medical notes and compared the early and late revisions by mechanism of failure. We considered an early failure to be any UKA revised before seven years. Results: There were 50 late failure UKAs and 37 early failures. We found no significant differences between groups in age, activity or demographics at time of primary UKA. The main implants in the late failure group were 19 (38%) Miller Galante, 22 (44%) PCA Duracon, and 9 (18%) others while the early failures consisted 21 (57%) Miller Galante, 5 (14%) Oxford, 3 (8%) PCA Duracon, and 8 (22%) others. 60% of late failures were cemented while 89% of early failures were cemented. Mechanism of late failure was 46% bearing wear, 22% progression of OA, 14% malalignment and 14% loosening, while mechanism of early failure was 41% loosening, 27% bearing wear and 14% malalignment. Discussion: Many historical bearing failures were due to oxidised polyethylene following sterilization. These should now have been eliminated by modern polyethylene and sterilization techniques. Mechanical mal-alignment is also now measurable and preventable by the use of CAS. We believe that avoidance of these two pitfalls will have an impact on the rate of early revision of UKA. Conclusion: We conclude that patients who underwent early UKA revision had a different failure mechanism from late UKA revisions. In the early failure group the main mechanisms were mechanical loosening and bearing wear. In the late revision group, bearing failures, progressive osteoarthritis and component loosening were the main reasons for failure. Mechanical malalignment failed to differ between the groups

There is a renewed interest in unicompartmental knee arthroplasty. The present report describes the minimum ten-year results associated with a – unicompartmental knee arthroplasty design that is in current use. Sixty-two consecutive unicompartmental knee arthroplasties that were performed with cemented modular Miller-Galante implants in 51 patients were studied prospectively both clinically and radiographically. All patients had isolated unicompartmental disease without patellofemoral symptoms. No patient was lost to follow-up. Thirteen patients (13 knees) died after less than 10 years of follow-up, leaving 38 patients (49 knees) with a minimum of 10 years of follow-up. The average duration of follow-up was 12 years. The mean Hospital for Special Surgery knee score improved from 55 points preoperatively to 92 points at the time of the final follow-up. Thirty-nine knees (80%) had an excellent result, six (12%) had a good result, and four (8%) had a fair result. At the time of final follow-up, 39 knees (80%) had flexion to at least 120 degrees. Two patients (two knees) with well-fixed components underwent revision to total knee arthroplasty, at seven and 11 years, because of progression of patello-femoral arthritis. At the time of the final follow-up, no component was loose radiographically and there was no evidence of peri-prosthetic osteolysis. Radiographic evidence of progressive loss of joint space was observed in the opposite compartment of nine knees (18%) and in the patello-femoral space of seven knees (14%). Kaplan-Meier analysis revealed a survival rate of 98.0% +/−2.0% at ten years and of 95.7% +/− 4.3% at 13 years, with revision or radiographic loosening as the end point. The survival rate was 100% at 13 years with aseptic loosening as the end point. After a minimum duration of follow-up of 10 years, this cemented modular uni-compartmental knee design was associated with excellent clinical and radiographic results. Although the 10 year survival rate was excellent, radiographic signs of progression of osteoarthritis in the other compartments continued at a slow rate. With appropriate indications and technique, this uni-compartmental knee design can yield excellent results into the beginning of the second decade of use

This study reports the survivorship free of revision or radiographic loosening of one hundred and eight consecutive cemented Miller-Galante unicompartmental knee arthroplasties at a mean ten-year follow-up. The purpose of this study was to report our experience with the Miller-Galante (MG) unicompartmental knee arthroplasty (UKA) at a mean ten-year follow-up in order to determine if this procedure can provide durable long-term clinical results. One hundred and eight cemented MG-UKAs in eighty-two patients performed by two surgeons between 1988 and 1997 were reviewed. There were one hundred and six medial and two lateral MG-UKAs performed. Mean age at surgery was sixty-seven years (range, thirty-nine to eighty-seven). There were forty-four males and thirty-eight females. Mean follow-up was ten years (range, five to thirteen). A Kaplan-Meier survivorship analysis using an end-point of revision surgery or radiographic loosening was employed to determine probability of survival at five and ten years. Of the eighty-two patients (one hundred and eight knees), nine patients (eleven knees) died and one patient (two knees) was lost to follow-up. Eleven patients (eleven knees) were revised at a mean of four years (range, one to nine), and one patient demonstrated radiographic loosening of the tibial component at seven years. Of the eleven revisions, only two required use of revision components. Mean pre-operative and final follow-up Knee Society clinical and functional scores were forty-seven and fifty-three, and ninety and seventy-nine points, respectively. Kaplan-Meier survivorship analysis revealed a probability of survival free of revision or radiographic loosening of 93% at five years and 88% at ten years. The results of this study demonstrate that the MG-UKA can provide reliable pain relief and restoration of function in selected patients. Our experience has shown that the survivorship of the MG-UKA approaches that of tricompartmental knee arthroplasty, and suggests that UKA may offer the advantage of ease of revision

Osteoarthritis of the knee is a debilitating condition affecting millions of persons, often requiring arthroplasty to relieve pain and improve mobility. For those patients with disease in only one compartment of the knee, unicompartmental knee arthroplasty (UKA) can be a viable surgical alternative. To date, there has not been a large series reported in the literature of UKAs performed with robotic assistance. The aim of this study was to examine the clinical outcomes of patients who underwent this procedure. Five hundred and ten procedures in patients with a mean age of 63.7 years (range, 28 to 88 years) who underwent unicompartmental knee arthroplasty using a robotic-assisted system between July, 2008 and June, 2010 were identified. Clinical outcomes were evaluated using the Oxford Knee Score and patients without recent follow-up were contacted by telephone. The revision rate and time to revision were also examined. The average length of stay for patients who underwent robot-assisted UKA was 1.4 days (range, 1 to 7 days). There was minimal blood loss with most procedures. At latest clinical follow-up, most patients were doing well after UKA with a mean Oxford Knee Score of 36.1 + 9.92. The revision rate was 2.5% with 13 patients being either converted from an inlay to onlay prosthesis or conversion to total knee arthroplasty. The most common indication for revision was tibial component loosening, followed by progression of arthritis. Mean time to revision was 9.55 + 5.48 months (range, 1 to 19 months). Unicompartmental arthroplasty with a robotic system provides good pain relief and functional outcome at short-term follow-up. Ensuring correct component alignment and ligament balancing increases the probability of a favorable outcome following surgery. Proper patient selection for appropriate UKA candidates remains an important factor for successful outcomes

Many designs of unicompartmental knee replacement show early and mid-term failure due to polyethylene wear. We studied the wear rate of congruent polyethylene meniscal bearings retrieved from failed Oxford unicompartmental knee replacements. We examined 16 bearings, 0.8 to 12.8 years after implantation, measuring their thickness and comparing it with that of 14 unused bearings. The mean rate of penetration, which included the effects of wear at both upper and lower surfaces, was 0.036 mm per year (maximum 0.08). Bearings as thin as 3.5 mm wore no faster than thicker models, but ten with evidence of impingement had greater wear. The six bearings with no impingement showed a mean rate of penetration of 0.01 mm per year. In unicompartmental knee replacement, careful implantation of fully congruous meniscal bearings can avoid failure due to polyethylene wear

Background. In the United Kingdom (UK), the fastest growing population demographic is the over 85 years of age, but despite this, outcomes achieved in the octogenarian population with a Unicompartmental Knee Replacement (UKR) are underrepresented in the literature. The Elective Orthopaedic Centre, Epsom, has an established patient reported outcome measures (PROMs) programme into which all patients are routinely enrolled. We aim to investigate the outcome of medial UKR using the oxford phase 3 implant in octogenarians. Methods. We retrospectively reviewed our database for patients aged 60–89 years, who underwent a medial unicompartmental Knee Replacement (UKR) using the oxford phase 3 implant, between June 2007-December 2012 (N=395). The patients were stratified into 3 groups based on age, 60–69 (N=188), 70–79(N=149), and 80–89(N=58). Oxford Knee Scores (OKS), Euro-quol (EQ-5D) scores, revision rates, and mortality were compared. Results. We found that the octogenarian group achieved considerable improvement at 1 year with a mean OKS of 39.2 (+/−7.193) and EQ-5D score of 0.791(+/−0.241). And this improvement remained significant at 2 years. There was no difference in functional outcome when the 3 groups were compared. Revision rates for the 3 groups from youngest to oldest were, 8.5%, 4.5%, and 6.9% respectively. Odds ratio and survival analysis showed no significant difference between the groups. Conclusion. In conclusion, we found that octogenarians over a 2 year period achieved similar functional outcome as their younger counterparts. Level of Evidence. IV

Background. Unicompartmental knee arthroplasty (UKA) patients with knee partial thickness cartilage loss have inferior functional performance compared to those with full thickness loss. Therefore, the aim of the present study was to investigate on the association between postoperative patients' joint awareness and satisfaction and preoperative radiographic osteoarthritis (OA) Ahlbäck grade in subjects undergoing robotic arm-assisted UKA. Methods. This retrospective observational study includes 675 patients (681 knees) undergoing robotic arm-assisted UKA at two centres between January 2014 and May 2019. Pre-operatively, knee radiographs were performed, and Ahlbäck OA grade was measured by two independent observers. Post-operatively, patients were administered the Forgotten-Joint-Score-12 (FJS-12) and 5-Level-Likert-Scale to assess joint awareness and satisfaction. Postoperative complications and revisions were recorded. Correlations were described between FJS-12, satisfaction and OA grade by means of an adjusted multivariate statistical analysis. Results. A total of 574 patients (580 UKAs) were assessed at a mean follow-up of 3.6 years post-operatively (85.2% follow-up rate; min. 12, max. 75 months). Nine UKAs were revised. Primary or secondary medial knee OA was the preoperative diagnosis in 538 cases, osteonecrosis was present in 42 cases. Cases were divided based on their preoperative Ahlbäck grade in Group A (joint space narrowing, Ahlbäck 1, 279 cases), Group B (joint space obliteration or minor bone attrition, Ahlbäck 2 and 3, 197 cases) and Group C (moderate or severe bone attrition, Ahlbäck 4 and 5, 104 cases). Moderate to severe OA grades (Group B and C) were associated with higher probability of higher postoperative FJS-12 compared to joint space narrowing group (Odds Ratio 1.6 and 1.7, respectively, p<0.05). No associations were described between OA grade and patients' satisfaction. Conclusions. Patients with preoperative joint space obliteration and minor to severe bone attrition have higher probability of a having a forgotten joint after robotic arm-assisted UKA, compared to those without full cartilage thickness loss

INTRODUCTION. Successful clinical outcomes following unicompartmental knee arthroplasty (UKA) depend on component positioning, soft tissue balance and overall limb alignment which can be difficult to achieve using manual instrumentation. Recently, robotically guided technology has been used to improve post-operative implant positioning, and limb alignment in UKA with the expectation that this will result in greater implant longevity. This multi-center study examines the survivorship of this robotically guided procedure coupled with a novel, anatomically designed UKA implant at two years follow up. OBJECTIVES. This study examines the two year survivorship and patient satisfaction of an anatomically designed UKA implant using a new robotically guided technology that has been shown to improve implant positioning and alignment. METHODS. 788 patients (890 knees) from 6 surgeons underwent robotically guided unicompartmental arthroplasty surgery and reached a minimum two year follow-up. The tibial component was a fixed bearing, metal backed onlay design. Patients were consecutive for each respective surgeon and were also each surgeon's first series of patients for that implant system. As part of an IRB approved study, every patient was contacted and asked a series of five questions to determine implant survivorship and patient satisfaction at a two year follow up. 620 patients (701 knees) enrolled in the study; the overall enrollment rate was 79%. There were 352 males and 266 females; the average age was 70 ± 9.23 years (range: 39–93) and the average BMI was 29.35 ± 4.59 (range: 18.97–47.77). The average follow up at the time the patients were contacted was 30 ± 5.53 months (range: 22–42). RESULTS. Eight knees were reported as revised within 24 months after the index procedure, yielding a two year revision rate of 1.1%. The average time to revision was 11 months. Five patients returned to their same surgeon for the revision procedure. Seven knees were revised to a total knee arthroplasty; one knee was revised to another unicompartmental knee arthroplasty. 71% of patients reported feeling “Very Satisfied” with their overall knee function. 22% of patients reported feeling “Satisfied,” 3% of patients reported feeling “Neutral,” 3% of patients reported feeling “Dissatisfied,” and 1% of patients reported feeling “Very Dissatisfied”. CONCLUSIONS. Excellent survival and satisfaction outcomes were noted in this subset of patients at two years post-operative. This robotically guided procedure shows promise of improved survivorship rates for UKA compared to what is currently reported in implant registries and comparative studies. These promising results indicate that improved implant placement accuracy achieved with robotic assistance leads to improved implant survivorship and patient outcomes

Aims

The patient-acceptable symptom state (PASS) is a level of wellbeing, which is measured by the patient. The aim of this study was to determine if the proportion of patients who achieved an acceptable level of function (PASS) after medial unicompartmental knee arthroplasty (UKA) was different based on the status of the anterior cruciate ligament (ACL) at the time of surgery.

Purpose. Long-term clinical and radiographic results and survival rates were compared between closed-wedge high tibial osteotomy (HTOs) and fixed-bearing unicompartmental knee arthroplasty (UKA) in patients with similar demographics. Methods. Sixty HTOs and 50 UKAs completed between 1992 and 1998 were retrospectively reviewed. There were no significant differences in preoperative demographics. The mean follow-up period was 10.7 ±5.7 years for HTO and 12.0 ±7.1 years for UKA (n.s.). The Knee Society knee and function scores, WOMAC, and range of motion (ROM) were investigated. The mechanical axis and femorotibial angle were evaluated. Kaplan–Meier survival analysis was performed (failure: revision to TKA), and the failure modes were investigated. Results. Most of the clinical and radiographic results were not different at the last follow-up, except ROM; ROM was 135.3 ±12.3° in HTO and 126.8 ±13.3° in UKA (p=0.005). The 5-, 10-, 15-, and 20-year survival rates were 100%, 91.0%, 63.4%, and 48.3% for closed-wedge HTO, respectively, and 90.5%, 87.1%, 70.8%, and 66.4% for UKA (n.s.). The survival rate was higher than that for UKA until 12 years postoperatively but was higher in UKAs thereafter, following a remarkable decrease in HTO. The most common failure mode was degenerative osteoarthritic progression of medial compartment in HTO and femoral component loosening in UKA. Conclusions. Long-term survival did not differ significantly between closed-wedge HTO and fixed-bearing UKA in patients with similar preoperative demographics and knee conditions. The difference in postoperative ROM and failure mode should be considered when selecting a procedure

Young, active patients with end-stage medial osteoarthritis (OA) secondary to anterior cruciate ligament (ACL) deficiency present a treatment challenge for surgeons. Current surgical treatment options include high tibial osteotomy (HTO) with or without ACL reconstruction, unicompartmental knee arthroplasty (UKA) with ACL reconstruction, and total knee arthroplasty (TKA). A recent systematic review reported a much higher rate of complications in HTO combined with ACL reconstruction than with UKA-ACL (21.1% vs 2.8%), while survivorship between the two procedures was similar. UKA offers several advantages over TKA, namely faster recovery, lower blood loss, lower rate of postoperative complications, better range of motion, and better knee kinematics. However, UKA has classically been contraindicated in the presence of ACL deficiency due to reported concerns over increased incidence aseptic loosening tibia. However, as a majority of patients presenting with this pathology are young and active, concerns about implant longevity with TKRA and loss of bone stock have arisen. As a result, several authors have described combining ACL reconstruction with medial UKA to decrease the tibiofemoral translation-related stress on the tibial component, thereby decreasing aseptic loosening-related failures. The purpose of this study was to compare the functional outcomes and survivorship of combined medial UKA and ACL reconstruction (UKA-ACL) with those of a matched TKA cohort. We hypothesized that UKA-ACL patients would have better functional outcomes than TKA patients while maintaining similar survivorship. Material and Methods. We conducted a case-control study establishing UKA-ACL as the study group and TKA as the control group by a single senior surgeon between October 2005 and January 2015. We excluded patients who were over the age of 55 at the time of surgery and those who had less than two-year follow-up. A total of 21 patients (23 knees) were ultimately included in each group. Propensity matching was for age-, sex-, and body mass index (BMI)-matched control group of TKA cases. Surgical technique. UKA-ACL. This patient's had an arthroscopy to allow for tunnel preparation in the standard fashion and then the graft was passed and fixed on the femoral side. An MIS medial incision was then made to allow for insertion of the Oxford mobile-bearing unicompartmental prosthesis (Zimmer Biomet, Warsaw, IN). Primary choice of ACL graft was autogenous ipsilateral semitendinosus and gracilis tendons, which was available I and 6 of the cases were revision from previous Gore-Tex synthetic ligament reconstruction. Results. Preoperatively, baseline questionnaires demonstrated that the TKA group had scored significantly lower on the symptom subscore of the KOOS. There was no difference between the groups in the rest of the KOOS subscores, (the UCLA, and the Tegner. All scores (UCLA, and Tegner – TBC post stats) improved significantly after surgery in both groups. Improvement in each subscore of the KOOS surpassed the minimal clinically important difference in both the UKA-ACL and TKA groups. At latest follow-up, there was no significant difference between the groups on the KOOS, UCLA or Tegner, showing that our UKA-ACL patients fared as our TKA patients. This confirms that UKA-ACL is an important tool in dealing with young patients with end-stage medial OA and ACL deficiency and offers an option that leads to less bone loss and potentially easier future revision. For any figures or tables, please contact authors directly

We carried out a comparison of the analgesic requirements, length of stay in hospital, complications and cost effectiveness of patients who had either a continuous disposable infusion pump or standard treatment for unicompartmental knee replacement. This study began as an audit. We completed the audit loop with a prospective study after implementing our recommendations. The device is a single use disposable elastometric pump, set immediately after surgery to deliver a continuous flow of 0.5% bupivacaine at a rate of 2mls per hour for 48 hrs into the knee joint via a fine catheter with a fenestrated tip. The case notes of all patients in the study were analysed to establish their total analgesic requirements for 48hrs following surgery. Complications and length of stay in hospital were recorded This has changed our clinical practice. Results of our study of 50 patients, 25 in each group (age and sex matched) confirmed that there was a significant reduction in opiate requirements after introduction of the pain pump. Length of stay in hospital was reduced from 5.7 to 3.9 days. Patients' requirements for NSAIDs were reduced. There were no significant complications in the pain pump group. The costs of the pump (£40) were offset by the reduction in analgesic requirements and shortened length of stay in hospital. We conclude this form of analgesia is safe, effective and cost effective. Our department has now changed to using the pump for all unicompartmental knee replacements

The contraindications for unicompartmental knee replacement (UKR) remain controversial. The views of many surgeons are based on Kozinn and Scott’s 1989 publication which stated that patients who weighed more than 82 kg, were younger than 60 years, undertook heavy labour, had exposed bone in the patellofemoral joint or chondrocalcinosis, were not ideal candidates for UKR. Our aim was to determine whether these potential contraindications should apply to patients with a mobile-bearing UKR. In order to do this the outcome of patients with these potential contraindications was compared with that of patients without the contraindications in a prospective series of 1000 UKRs. The outcome was assessed using the Oxford knee score, the American Knee Society score, the Tegner activity score, revision rate and survival. The clinical outcome of patients with each of the potential contraindications was similar to or better than those without each contraindication. Overall, 678 UKRs (68%) were performed in patients who had at least one potential contraindication and only 322 (32%) in patients deemed to be ideal. The survival at ten years was 97.0% (95% confidence interval 93.4 to 100.0) for those with potential contraindications and 93.6% (95% confidence interval 87.2 to 100.0) in the ideal patients. We conclude that the thresholds proposed by Kozinn and Scott using weight, age, activity, the state of the patellofemoral joint and chondrocalcinosis should not be considered to be contraindications for the use of the Oxford UKR

Introduction. Unicompartmental Knee Replacement Arthroplasty (UKA) is a treatment option for early knee OA that appears under-utilised, partly because of a lack of clear guidance on how to best restore lasting knee function using such devices. Computational tools can help consider inherent uncertainty in patient anatomy, implant positioning and loading when predicting the performance of any implant. In the present research an approach for creating patient-specific finite element models (FEM) incorporating joint and muscle loads was developed to assess the response of the underlying bone to UKA implantation. Methods. As a basis for future uncertainty modelling of UKA performance, the geometriesof 173 lower limbs weregenerated from clinical CT scans. These were segmented (ScanIP, Simpleware Ltd, UK) to reconstruct the 3D surfaces of the femur, tibia, patella and fibula. The appropriate UKA prosthesis (DePuy, U.S.) size was automatically selected according to tibial plateau size and virtually positioned (Figure 1). Boolean operations and mesh generation were accomplished with ScanIP. A patient-specific musculoskeletal model was generated in open-source software OpenSim (Delp et al. 2007) based on the Gait2392 model. The model was scaled to a specific size and muscle insertion points were modified to corresponding points on lower limb of patient. Hip joint load, muscle forces and lower limb posture during gait cycle were calculated from the musculoskeletal model. The FE meshes of lower limb bones were transformed to the corresponding posture at each time point of a gait cycle and FE analyses were performed (Ansys, Inc. U.S) to evaluate the strain distribution on the tibial plateau in the implanted condition. Results. With the tibial component positioned above, along or below the joint line, the lower limb alignment was more varus, remained unaltered or more valgus respectively (Figure 2). With the tibial component positioned 3mm above the joint line, the peak strain in the underlying bone was 670 µstrain on medial (UKA) side and 6780 µstrain on the intact side. With the tibial component positioned 3mm below the joint line, the peak strain was 3010 µstrain on the medial side and 5330 µstrain on the intact side. Here, the strains on the medial side increased by 2640 µstrain whilst they were reduced by 1450 µstrain on the intact side compared to the unimplanted case. Conclusion. The present research has delivered a framework which can be exploited in future uncertainty modelling of UKA performance predictions. The patient-specific model incorporates loading, anatomical and material property variability, and can be applied to evaluate the performance of UKA prostheses for metrics such as stress/strain/micromotions in larger patient populations. For figures/tables, please contact authors directly.

Introduction. Robotic technology has been applied to unicompartmental knee arthroplasty (UKA) in order to improve surgical precision in prosthetic component placement, restore knee anatomic surfaces, and provide a more physiologic ligament tensioning throughout the knee range of motion. Recent literature has demonstrated high reliability of robotic-arm assisted UKA in component placement and executing a soft-tissue tensioning plan, with excellent short-term survivorship. Few studies have investigated survivorship and patients' satisfaction at longer follow-ups. Therefore, the purpose of the present study was to determine the survivorship, clinical results and patients' satisfaction of robotic-arm assisted UKAs at a mid-term follow-up, with a minimum of 5 years of follow-up. Methods. The present retrospective study includes 252 patients (260 knees) who underwent robotic-arm assisted fixed bearing metal backed UKAs at a single centre between April 2011 and July 2013. The mean age at surgery was 66.2 years (SD 8.6). Post-operatively, patients were administered the Forgotten Joint Score-12 (FJS) and asked about their satisfaction level after knee surgery (grade from 1 to 5). Post-operative complications were recorded. Failure mechanisms, revisions and reoperations were also assessed. Kaplan-Meier survival curves were calculated, considering reoperation for all causes and revision as the events of interest. Results. A total of 223 patients (231 robotic-arm assisted UKAs) were assessed at a mean follow-up of 5.8 years post-operatively (88.5% follow-up rate, min. 60 months, max. 87 months). In 219 cases, a medial robotic-arm assisted UKA was implanted, in 12 cases a lateral implant was performed. Five medial robotic-arm assisted UKAs were revised, resulting in a survivorship of 98% (C.I. 96.0%–99.1%). One case underwent revision for prosthetic joint infection, one for tibial aseptic loosening, one for post-traumatic tibial plateau fracture, and two for unexplained pain. No lateral robotic-arm assisted UKAs were revised, resulting in a survivorship of 100%. On average, the FJS and the satisfaction level resulted 75.6 (SD 26.1) and 4.2 (SD 1.0) in medial UKAs, and 81.7 (SD 15.3) and 4.4 (SD 0.8) in lateral UKAs, respectively. In medial UKAs 83% of the examined cohort reported good/excellent FJS outcomes, while 92% of the lateral UKA patients had good/excellent FJS results. In medial UKAs, male patients resulted to have better FJS (p<0.01) and higher satisfaction level (p<0.03) compared to female patients, while no outcome differences were reported in patients with BMI>30 and among different age groups. Given the small number of lateral UKAs included in the present patients' cohort, no statistical analysis was performed on this group. Conclusion. In the present study, survivorship and clinical outcomes of a large cohort of 223 patients undergoing medial and lateral robotic-arm assisted UKAs were assessed at a mean of 5.8 years of follow-up. The overall survivorship was found to be 98%, with unexplained knee pain as the most common reason for UKA revision. The present study shows that robotic-arm assisted UKA patients had lower revision rates for aseptic loosening and osteoarthritis progression compared to conventional UKA at mid-term follow-up, as reported in the literature. The good post-operative clinical scores highlight the efficacy of robotic-arm assisted UKA in restoring knee function and relieving pain. For figures, tables, or references, please contact authors directly

Introduction. In total knee arthroplasty, the alignment of leg depends on the alignment of the component. In unicompartmental knee arthroplasty, it is determined by the thickness of the implant relative to the bone excised mostly. After initial scepticism, UKA is increasingly accepted as a reliable procedure for unicompartmental knee osteoarthritis with the improvements in implant design, surgical technique and appropriate patient selection. Recently, computer assisted UKA is helpful in accuracy and less invasive procedure. But, fixed bearing or mobile bearing in UKA is still controversy. We compared the early clinical and radiological results of robot-assisted unicompartmental knee arthroplasty using a fixed bearing design versus a mobile type bearing design. Materials and Methods. A data set of 50 cases of isolated compartmental degenerative disease that underwent robot-assisted UKA using a fixed bearing design were compared to a data set of 50 cases using a mobile bearing type design. The operations were performed by one-senior author with the same robot system. The clinical evaluations included the Knee Society Score (knee score, functional score) and postoperative complications. The radiological evaluations was assessed by 3-foot standing radiographs using the technique of Kennedy and White to determine the mechanical axis and femoro-tibial angle for knee alignment. Operative factors were evaluated including length of skin incision, operation time, blood loss, hospital stay and intraoperative complications. Results. There were no statistically significant differences in operation time, skin incision size, blood loss and hospital stay. (p > 0.05) There were no significant differences in Knee Society Scores at last follow up. An average preoperative femorotibial alignment was varus alignment of −1° in both groups. Postoperative patients with fixed-bearing implants had an average +2.1° valgus and the patients with mobile bearing implants had +5.4° valgus in femorotibial alignment, which was different.(p<0.05) There was one case of medial tibia plateau fracture in fixed bearing group in 3 months postoperatively. And there were one case of liner dislocation with unstable knee in 6 weeks postoperatively and one case of femoral component loosening in 1 year postoperatively in mobile bearing group. There was no intraoperative complication. The average preoperative knee score was 45.8, which improved to 89.5 in fixed bearing group and 46.5, which improved to 91.2 in mobile bearing group at last followup. The average preoperative function score was 62.4 which improved to 86.5 in fixed bearing group and 60.7 which improved to 88.2 in mobile bearing group at last followup. Conclusion. In ourearly experience, two types of bearing of robot-assisted UKA groups showed no statistical differences in clinical assessment but there was statistical difference in postoperative radiological corrected alignment. But in aspect of early complications, we think that mobile bearing seems to be requiring more attention in surgery

Unicompartmental knee arthroplasty (UKA) has been gaining popularity in recent years due to its perceived benefits over total knee replacements, such as greater bone preservation, reduced operating-room time, better postoperative range of motion and improved gait. However there have been failures associated with UKA caused by misalignment of the implants. To improve the implant alignment a robotic guidance system called the RIO Robotic Arm has been developed by MAKO Surgical Corp (Ft. Lauderdale, FL). This robotic system provides real-time tactile feedback to the surgeon during bone cutting, designed to give improved accuracy compared to traditional UKA using cutting jigs and other manual instrumentation. The University of Strathclyde in association with Glasgow Royal Infirmary has undertaken the first independent Randomised Control Trial (RCT) of the MAKO system against the Oxford UKA – a conventional UKA used in the UK. The trial involves 139 patients across the two groups. At present the outcomes have been evaluated for 30 patients. 14 have received the MAKO unicompartmental knee arthroplasty and 16 the Oxford UKA. Both groups were seen 1 year post-operatively. Kinematic data was collected while subjects completed level walking using a Vicon Nexus motion analysis system. Three-dimensional hip, knee and ankle angles were compared between the two arthroplasty groups. Our initial findings indicate that hip and ankle angles show no significant statistical difference, however there is a significant difference (p < 0.05) in the knee angles during the stance phase of gait. Data shows higher angles achieved by the MAKO group over the Oxford. It would appear from our early findings that the MAKO RIO procedure with Restoris implants gives at least comparable functional outcome with the conventional Oxford system and may prove once our full sample is available for analysis to produce better stance phase kinematics with a more active gait pattern than the conventional Oxford procedure. Further work includes analysing the data obtained from the patients in a number of other activities. These include a full biomechanical analysis of ascending and descending a flight of stairs, sit to stand and a deep knee lunge. The high demand/high flexion tasks in particular may reveal if there's an advantage to using the MAKO procedure over the Oxford. If there is a direct correlation between alignment and patient function then this effect could be more significant in the more demanding patient tasks

To evaluate prospectively the mid-term results of the Zimmer Unicondylar Knee arthoplasty (UKA). Between 2005 and 2012, 187 unicompartmental knee arthroplasties (UKA) were performed by a single surgeon using a fixed-bearing prosthesis (Zimmer). 37 cases were excluded as either were lost to follow-up or had less than six months follow-up. The study included 150 UKAs. Deformity, if present, was correctable. Patellofemoral joint (PFJ) disease was not considered as an absolute contraindication. The average patient age at the time of surgery was 66 years (range 42–88 years); 78 of which were male. Mean follow-up time was 3.6 years (range 7–81 months). Mean Body Mass Index (BMI) was 29 (range 21–41). Clinical and conventional radiological evaluations were carried out at six months, one, two and five years postoperatively. 147 cases were medial compartment replacement and three were lateral. 86 patients had grade III OA and 64 had grade IV (Kellgren and Lawrence). 113 patients had an element of PFJ disease. The mean Knee Society knee and function scores had an improvement from 55 and 54 points pre-operatively to 95 and 94 points respectively at time of most recent evaluation. The average flexion improved from 116 degrees pre-operatively to 127 degrees. Two cases were revised, one due to progression of osteoarthritis in the lateral compartment of the knee and the other was due to arthrofibrosis. The Zimmer unicompartmental knee arthroplasty provided excellent pain relief and restoration of function in carefully selected patients. However, long-term studies are necessary to investigate the survival rate for this prothesis

Unicompartmental knee replacement (UKR) is associated with higher revision rates than total knee replacement and it has been suggested that surgeons should receive specific training for this prosthesis. We investigated the outcome of all UKR in a district general hospital over ten years. All patients who had received UKR from 2003 to 2013 were identified from theatre records, as were all revision knee arthroplasties. We contacted all patients (or their GP) with no known revision to ascertain UKR status. A life table analysis was used for three categories: all surgeons and types of UKR, Oxford UKR only and Oxford UKR by surgeons with specific training. There were 319 UKR (one loss to follow up), four types of prosthesis, 21 failures and a 5-year cumulative survival rate of 91.54%. There were 310 Oxford UKR with 17 failures and 5-year survival 93.56%. Surgeons with training in use of Oxford UKR completed 242 replacements with 10 failures and 5-year survival of 95.68%. In comparison with results for Oxford UKR in 11th annual NJR report, our results are satisfactory and support continued use of this prosthesis in a non-specialist centre. Our established programme of surveillance will monitor the survival of UKR in our hospital

Oxford Medial Unicompartmental Knee Replacement (OMUKR) is a well-established treatment option for isolated medial compartment arthritis, with good patient reported outcome measures (PROMs). We present our results of the Oxford Domed Lateral Unicompartmental Knee Replacement (ODLUKR) to establish if patients benefit as much as with OMUKR. Retrospective review of prospectively collected data of a single surgeon series of consecutive UKR from 2007 to 2014 were collated with a minimum 2 years follow-up. PROMs data were collected using pre- and post-operative Oxford Knee Scores (OKS) (best score of 48). One hundred and twenty-eight OMUKR and 27 ODLUKR were performed in the study period. There was no significant difference in the age at time of surgery, but there were significantly more women in the ODLUKR group (74% vs 53%). There was no significant difference in pre-op OKS between the groups (OMUKR = 16/48; ODLUKR = 20/48), or the improvement in OKS post-op (OMUKR = 19 points; ODLUKR = 17 points). One ODLUKR was revised to Total Knee Replacement (TKR) for pain. There were three (11.1%) bearing dislocations, which were treated with thicker bearing exchange, with no subsequent problems. There were no bearing dislocations in the OMUKR. Four OMUKR were revised to TKR due to pain. The overall implant survivorship was 96.3% for ODLUKR and 96.9% for OMUKR. ODLUKR is a good treatment option for isolated lateral compartment arthritis and gives results equivalent to OMUKR. There is, however, an increased risk of bearing dislocation so should be performed by a high volume UKR surgeon

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).

We retrospectively studied the major complications occurring after one- and two-stage bilateral unicompartmental knee replacements (UKR). Between 1999 and 2008, 911 patients underwent 1150 UKRs through a minimally invasive approach in our unit. Of these, 159 patients (318 UKRs) had one-stage and 80 patients (160 UKRs) had two-stage bilateral UKRs. The bilateral UKR groups were comparable in age and American Society of Anaesthesiology grade, but more women were in the two-stage group (p = 0.019). Mechanical thromboprophylaxis was used in all cases. Major complications were recorded as death, pulmonary embolus, proximal deep-vein thrombosis and adverse cardiac events within 30 days of surgery. No statistical differences between the groups were found regarding the operating surgeon, the tourniquet time or minor complications except for distal deep-vein thrombosis. The anaesthetic times were longer for the two-stage group (p = 0.0001). Major complications were seen in 13 patients (8.2%) with one-stage operations but none were encountered in the two-stage group (p = 0.005). Distal deep-vein thrombosis was more frequent in the two-stage group (p = 0.036). Because of the significantly higher risk of major complications associated with one-stage bilateral UKR we advocate caution before undertaking such a procedure

We report the outcome of 135 knees with anteromedial osteoarthritis in which the Oxford meniscal-bearing unicompartmental arthroplasty was inserted in a district general hospital by a single surgeon. All the knees had an intact anterior cruciate ligament, a correctable varus deformity and the lateral compartment was uninvolved or had only minor osteoarthritis. The mean follow-up was 5.82 years (2 to 12). Using revision as the end-point, the outcome for every knee was established. Five knees have been revised giving a cumulative rate of survival of the prosthesis at ten years of 94.04% (95% confidence interval 84.0 to 97.8). Knee rating and patient function were assessed using the modified Knee Society scoring system. The mean knee score was 92.2 (51 to 100) and the mean functional score 76.2 (51 to 100). The survival of the implant is comparable to that reported by the designers of the prosthesis and not significantly different from that for total knee replacement. Unicompartmental knee replacement offers a viable alternative in patients with medial osteoarthritis. Appropriate selection of patients and good surgical technique are the key factors

Introduction. The prescription of opioids has increased in the last two decades. Recently, several states have developed online Prescription Drug Monitoring Programs aimed at preventing overprescribing of controlled substances. Unicompartmental knee arthroplasty (UKA) has been shown to provide improved early functional outcomes, faster recovery, and less postoperative morbidity and pain than total knee arthroplasty (TKA). The aim of this study is to evaluate differences in opioid prescription requirements between patients undergoing TKA and UKA. Methods. We retrospectively reviewed consecutive series of primary TKA from January 2017 to July 2017 and primary UKA from January 2016 to July 2017 using standardized perioperative pain protocols. All patients that underwent any other procedure 6 months prior to and after index surgery were excluded, resulting in 740 TKA and 241 UKA. Demographic and comorbidity information was collected for all patients. Opioid prescriptions, morphine milligram equivalents (MME), sedatives, benzodiazepines, and stimulants were collected from State Controlled Substance Monitoring website 6 months prior and after index procedures. Univariate and multivariate analysis were performed for patients that had a second prescription and continued use (defined as more than 6 months postoperatively). Results. Patients undergoing UKA had a second opioid prescription filled 50.2% of the time compared to 60.5% for TKA (p=0.006). In addition, continued opioid use after 6 months was 8.3% in UKAs compared to 11.8% in TKAs (p=0.149). When controlling for potential confounders, patients undergoing UKA were less likely to require a second prescription than TKA patients (adjusted odds ratio: 0.603 (95% Confidence Interval (CI): 0.425–0.855). In addition, continued use of opioids after 6 months was also reduced compared to patients undergoing TKA (adjusted OR: 0.51, 95% CI: 0.27–0.97) in the multivariate analysis. Other independent predictors of continued opioid use include obesity (OR 1.79, 95% CI 1.07–3.00) and preoperative opioid use (OR 1.66 per script, 95% CI: 1.49–1.86). Our models for second script and continued use reported AUC scores of 0.65 and 0.85, respectively. Conclusion. Patients with UKA are less likely to require a second opioid prescription and have continued opioid use even when controlling for a variety of potential confounders. Given the reduced opioid requirements associated with UKA, this study supports that orthopaedic surgeons should adjust their prescription patterns and educate patients regarding expected analgesic needs. Due to the retrospective nature of this study we were unable to precisely quantify the amount of opioids consumed in these patient groups. An ongoing prospective study will more accurately determine the duration and quantity of opioid use after UKA compared to TKA

A total of 10474 unicompartmental knee arthroplasties was performed for medial osteoarthritis in Sweden between 1986 and 1995. We sought to establish whether the number of operations performed in an orthopaedic unit affected the incidence of revision. Three different implants were analysed: one with a high revision rate, known to have unfavourable mechanical and design properties; a prosthesis which is technically demanding with a known increased rate of revision; and the most commonly used unicompartmental device. Most of the units performed relatively few unicompartmental knee arthroplasties per year and there was an association between the mean number carried out and the risk of later revision. The effect of the mean number of operations per year on the risk of revision varied. The technically demanding implant was most affected, that most commonly used less so, and the outcome of the unfavourable design was not influenced by the number of operations performed. For unicompartmental arthroplasty, the long-term results are related to the number performed by the unit, probably expressing the standards of management in selecting the patients and performing the operation

Introduction: Unicompartmental knee Arthroplasty (UKA) is a commonly used and accepted treatment for Osteoarthritis (OA) in the medial compartment. How-ever, despite some good results. 1. there is still a reluctance to use this procedure in the lateral compartment for the same indications, as the procedure is considered technically difficult, and not as successful. 2. This study reports the clinical outcome of lateral UKAs in comparison with medial UKAs, TKAs and a normal population group using a knee score designed to highlight the shortcomings of TKA. 3. . Methods: 20 consecutive patients over 2 years following lateral UKA were functionally assessed. They were compared with 3 groups of 20 age and sex matched patients: those who had undergone medial UKA or TKA in the same time period, or normal controls from an upper limb clinic. Clinical function was assessed at least 2 years postoperatively, using the ‘total knee questionaire’. 3. This consists of 55 scaled multiple choice questions. The score is derived from the product of three scales: the importance of a specific activity, the frequency with which it is undertaken, and the ease with a patient can perform it. Results: 90% of the patients reported that they were either satisfied or very satisfied with their lateral UKA, with 95% of the patients in the medial UKA group and 75% in the TKA group reaching this level of satisfaction. The average Composite Score for the lateral UKA group was significantly better compared with the TKA group (p < 0, 05). (Kneeling – (5,72/4,45), Gardening – (7,32/5,18), Pivoting – (7,83/6,78) and Walking with heavy bags (8,2/5,97)). The Total Composite Score was significantly better (p< 0, 05) in Patients after lateral UKA (7,14) compared to patients who underwent TKA (5,99). No statistically significant differences in the Total Composite Score was found between both the lateral & medial UKA patients taken as a single group compared with the control group. Conclusion: Lateral Unicompartmental Knee Arthroplasty achieves superior knee function in comparison to Total Knee Arthroplasty, so is worth considering as an option in for early OA of the lateral compartment

Introduction Unicompartmental knee replacement (UKR) is an increasingly utilised alternative to tibial osteotomy and total knee arthroplasty in patients with single compartment degenerative disease. We report on four fractures of the medial tibial plateau following UKR. Methods We retrospectively reviewed four cases with periprosthetic tibial plateau fractures following unicompartmental knee replacement. Each arthroplasty, performed between 1999 and 2002, was done in a community teaching hospital by a single orthopaedic surgeon and a senior level assistant. All patients had medial compartment osteoarthritis confirmed both radiographically and arthroscopically prior to arthroplasty surgery. The arthroplasties were performed by four different surgeons and three different arthroplasty systems were used. All cases were reviewed using the documented chart histories and x-ray evaluation. Each surgeon was contacted individually for the relevant case history and x-rays. The study population was composed of four females, and no males with a mean age of 63.5 years (range 58 to 68). Two patients (50%) had simultaneous bilateral UKRs performed. The remaining two patients had unilateral procedures, involving one right and one left knee. Two patients were clinically obese, and one patient had had a previous ipsilateral high tibial osteotomy. Results The total number of fractures was four, involving three left knees and one right knee. Of the bilateral arthroplasties each patient sustained a unilateral fracture of the left knee. The patient with the previous tibial osteotomy sustained an ipsilateral fracture. Two fractures involved traumatic falls, the remaining fractures had no history of trauma. The mean post-operative period to fracture was 95.75 days with a range of 5 to 195 days. Two patients had revision surgery to total knee arthroplasty. One patient underwent internal fixation of the fracture with retention of the original prosthetic components and exchange of the polyethylene bearing. The remaining patient underwent revision of the tibial component with concurrent internal fixation and was subsequently revised to total knee arthroplasty as the result of failure. Subsequent to the described surgery all fractures have healed with no further surgical intervention. Conclusions This series, whilst small, demonstrates that tibial periprosthetic fracture following UKR is a previously unreported but important cause of failure. Revision surgery to total knee replacement appears to be a reasonable salvage option

Background. To evaluate the causes and modes of complications after unicompartmental knee arthroplasty (UKA), and to identify its prevention and treatment method by analyzing the complications after UKA. Materials and Methods. A total of 1,576 UKAs were performed between January 2002 and December 2014 at a single-institution. Postoperative complications occurred in 89 knees (83 patients, 5.6%), and 86 of them were found in females and 3 in males. Their mean age was 61 years (range, 46 to 81 years) at the time of initial UKA and 66 years (range, 46 to 82 years) at the time of revision surgery. We analyzed the complications after UKA retrospectively andinvestigated the proper methods of treatment (Table 1). Results. A total of 89 complications (5.6%) occurred afterUKA. Regarding the type of complications after UKA, there were bearing dislocation (n=42), component loosening (n=23), 11 cases of femoral component loosening, 8 cases of tibial component loosening, and 4 cases of both femoral and tibial component loosening, periprosthetic fracture (n=6), polyethylene wear/ destruction (n=3), progression of arthritis to the other compartment (n=3), medial collateral ligament (MCL) injury (n=2), impingement (n=2), infection (n=5), ankylosis (n=1), and unexplained pain (n=2) (Table 2). The most common complication after UKA was mobile bearing dislocation in mobile-bearing type and loosening of prosthesis in fixed-bearing type, but polyethylene wear and progression of arthritis were relatively rare. The mean interval from UKA to the occurrence of complications was 4 years and 6 months (range, 0 [during operation] to 12 years). Of those complications following UKA, 58 knees were treated with conversion TKA, 1 with revision UKA, and 21 with simple bearing change. Complications in the remaining knees were treated with arthroscopic management (n=2), open reduction and internal fixation (n=3), closed reduction and internal fixation (n=1), manipulation (n=1), and MCL repair (n=2) (Table 3). Discussion. In this single-center study, we reviewed the causes and types of complications (n=89) that occurred following UKA (n=1,576) and investigated optimal treatment methods. The incidence and type of complications were also compared among patients classified according to gender, medial/lateral UKA, and implant design and type. The strengths of this study include that all the patients were enrolled from the same institution and the sample size (UKA cases and complication cases) was relatively large compared to that in previous publications. The most common complication following UKA was bearing dislocation in the mobile-bearing knees and component loosening in the fixed-bearing knees. The incidence of polyethylene wear and progression of arthritis to the other compartment was relatively low. The results of our study are in some discrepancy with those of studies involving Western patients. This can be attributed to the differences in patient characteristics such as lifestyle and in the type and design of implant used. Conclusion. Thorough understanding of UKA, proper patient selection, appropriate implant choice are essential to reduce complications following UKA and obtain satisfactory outcomes. We suggest that complications following UKA should be treated differently according to the type and cause of complication and conversion TKA can be the most effective treatment when revision operation is determined necessary

Aim: Endpoints that are more common than revision would be more valuable in survival analysis. Assessment of unicompartmental knee replacement (UKR) by patientñs own evaluation may be sensitive as for total knee replacement (TKR). Cohort of patients treated by UKR has been studied for satisfaction and pain as endpoints and related to TKR. Materials: At the Centro di Chirurgia Protesica, Istituto Ortopedico ÒGaleazziÒ, Milano (I), more than 600 hip and knee replacements are performed per year. Among these, from February to April 2001, 109 patients have been treated for primary unilateral arthritis of the knee by the same surgeon, same OR team, and environmental conditions. 53 patients received unicompartmental knee replacement (Allegretto TM, Centerpulse) because of unicompartmental knee degeneration. 56 patients received total knee replacement (Innex TM, Centerpulse) for tri-compartmental arthritis. Patients have been preoperative evaluated for age, ASA score, KSS and Function. Postoperative recovery and physio funtions. At 18 months follow-up, cohort of UKR has been evaluated for satisfaction and pain as endpoints by telephone interview. The same has been for TKR group. Results: No differences were between the UKR and TKR cohorts for age at surgery (UKR: 68yrs, 86-45; TKR: 69yrs, 83-51); ASA score, KKS (UKR: 54,2pts, 76-25; TKR: 43,3pts, 75-10); function (UKR: 67,5pts, 95-20; TKR: 60,6pts, 95-10). No differences were for recovery period and rehabilitation program. Within the TKR group had 1 died for post op cardiopulmonary complication. At follow-up patients was judged by the author not eligible for any revision, on clinical and radiological examination. None was lost at follow-up, none revised. At 18 months follow-up, UKR cohort, 52 on 53 patients were satisþed by their knee, event rate 98% (89–100). 18 on 52 were in mild pain and drug use, event rate 34% (28–39), 4 of those in trouble with stairs. 1 patient was not satisþed. For TKR cohort, 49 on 55 patients were satisþed, event rate 89% (81–97). 24 on 49 reported pain and drug use, event rate 49% (42–56), 7 of those in stairs climb limits. 6 patients were not satisþed. Conclusion: Because of long time is needed to produce adequate number in joint replacement groups, statistical method relies on survivorship analysis for studying adverse events. However confounding factors, lost of follow-up, and revision as endpoint may mislead results (Murray DW. et al. JBJS 1993). Meanwhile, randomised clinical trial provides a cornerstone not only for evidence-based medicine but also for evidence public health, evidence based hospital administration, evidence based purchasing, and evidence based consumerism (Sackett DL et al. BMJ 1994). Our TKR cohort pain endpoint survival rate is comparable with others in literature (Murray DW, Frost SJD. JBJS 1998). Comparing TKR with UKR groups has limitation and EBM is not eligible for such groups. However, cohort study for joint replacement, performed within a short period of time, and less confounding factors, increases assessment reliability and endpoints deþ nition. Overall, our result shows lower pain and higher satisfaction events rate for UKR than TKR

Radiological measurements are an essential component of the assessment of outcome following knee arthroplasty. However, plain radiographic techniques can be associated with significant projectional errors because they are a two-dimensional (2D) representation of a three-dimensional (3D) structure. Angles that are considered within the target zone on one film may be outside that zone on other films. Moreover, these parameters can be subject to significant inter-observer differences when measured. The aim of our study therefore was to quantify the variability between observers evaluating plain radiographs following Unicompartmental knee arthroplasty. Twenty-three observers, made up of Orthopaedic Consultants and trainees, were asked to measure the coronal and sagittal alignment of the tibial and femoral components from the post-operative long-leg plain radiograph of a Unicompartmental knee arthroplasty. A post-operative CT scan using the low dose Imperial knee protocol was obtained as well and analysed with 3D reconstruction software to measure the true values of these parameters. The accuracy and spread of the pain radiographic measurements were then compared with the values obtained on the CT. On the femoral side, the mean angle in coronal alignment was 1.5° varus (Range 3.8, SD 1, min 0.1, max 3.9), whereas the mean angle in sagittal alignment was 8.6° of flexion (Range 7.5, SD 1.5, Min 3.7, Max 11.2). The true values measured with CT were 2.4° and 11.0° respectively. As for the tibial component, the mean coronal alignment angle was 89.7° (Range 11.6, SD 3.3, Min 83.8, Max 95.4), and the mean posterior slope was 2.4° (Range 8.7, SD 1.6, Min -2, Max 6.7). The CT values for these were 87.6° and 2.7° respectively. We conclude that the plain radiographic measurements had a large scatter evidenced by the wide ranges in the values obtained by the different observers. If only the means are compared, the plain radiographic values were comparable with the true values obtained with CT (that is; accuracy was good) with differences ranging from 0.3° to 2.4°. The lack of precision can be avoided with the use of CT, particularly with the advent of low-dose scanning protocols

Introduction Unicompartmental knee arthroplasty has become increasingly popular in the USA. Minimally invasive techniques for implant placement has augmented the procedure and allowed for rapid rehabilitation and return to activities of daily living. Nevertheless, with new technologies come learning curves and rediscovery of the past. Complications do occur with placement of unicompartmental knee devices. Examples of proper and improper implantation techniques and the radiographic results are presented. Methods I present the results of a review of the literature and personal experience. Results Overcorrection deformity has been identified as a precursor to early failure. When sizing and placing the implants an attempt should be made to “leave alignment alone” and there should be relative pseudo-laxity of the joint with the new implants. Problems with varus or valgus tibial cuts are well known. Posterior slope is less understood. While it is reasonable to reproduce the natural inclination of the tibia, over-correction or under-correction leads to balance abnormalities. Improper slope may be a prelude to subsidence particularly if an inset design is employed. Coalescence of the pin tracts used to fix cutting blocks and sagittal tibial cuts (along the spine) have been identified as problematic. The small surface area and stress loads on the tibia predispose this area to fracture, particularly when these stress risers are present. Patellar impingement can lead to pain and disability. It may be avoided by appropriate sizing, slight recession of the femoral component, or a modest resection of the medial facet. The posterior cruciate ligament is at risk during resection of the proximal tibia. Injury to the ligamentous complex will lead to instability problems not manifest in the more conforming articulation of a TKA. One unavoidable problem is the relatively large tibial resection required in “small” knees. While we attempt to be minimal in the tibial bone resections, six to eight millimetres appears large in a diminutive knee. The most difficult positioning problem appears to be internal-external rotation positioning. Several implant systems utilize the tibial cut to position the femur. The tibial platform matches or links the femoral varus-valgus (correct or not) to the tibial cut. The rotation is more free-hand and is not well coordinated by the landmarks used in TKA. Edge loading will result from rotational malposition. Conclusions The techniques for placement, the instrumentation, and the unicompartmental implant designs have evolved to the point where many of the problems encountered in the USA in the 1980’s have been alleviated. Attention to common positional and implantation errors will result in more satisfactory outcomes. While the less conforming articulation of these devices is forgiving, it may also penalize in the long term. Many of the problems encountered after unicompartmental knee arthroplasty could be avoided with the simple awareness that promotes improved surgical technique. In relation to the conduct of this study, one or more of the authors has received, or is likely to receive direct material benefits

Introduction. The aim of our study was to compare the radiographic alignment unicompartmental knee arthroplasty (UKA) with using conventional non-navigation technique and computer-assisted navigation technique. Our study was focused on bearing alignment on clinical outcome of knee. Materials and Methods. In our department we have performed between January 2005 and December 2012 106 UKA. All patients were examined clinically and radiologically before and after operation. There were implanted two types of UKA, 67 of UKA were performed by The PRESERVATION™ (DePuy) with navigation and 39 UKA Oxford® Partial Knee (Biomet.) were performed by conventional technique. In our study we have evaluated 104 of medial UKA divided to groups, 65 implantation of The PRESERVATION™ and 39 implantation of Oxford® Partial Knee UKA. We have evaluated 101 patients, 61 women, 40 men, average age 66,5 (50–82) years. Firstly we performed measurement of parameters determine alignment UKA. These values were written down and the deviation of norm was established. Results were divided in two groups, one with values of normal range and the second beyond normal range. Values of all UKA were matched with clinical outcome postoperatively. This assessment was performed by The Knee Society Clinical Rating System (Knee score). Results. The mean follow-up was 3,3 (max. 7,1) years. The group with navigation technique improved Knee score from mean 58 (41–79) preoperatively to 93 (62–100) postoperatively. Conventional UKA Knee score improved from 56 (39–77) preoperatively to 91 (61–100) postoperatively. Clinical outcome is comparable in both groups. Radiological assessment of alignment unicompartmental knee replacement according to our measurement results in favour of computer-assisted navigation. Conclusion. Computer-assisted navigation enables more exact alignment of the femoral and tibial component than conventional technique. In spite of the fact that difference clinical outcome is comparable

Abstract

A Prospective, randomised controlled trial demonstrates superior outcomes using an active constraint robot compared with conventional surgical technique in unicompartmental knee arthroplasty (UKA). Computer assistance should extinguish outliers in arthroplasty, with robotic systems being able to execute the preoperative plan with millimetre precision. We used the Acrobot system to deliver tailor made surgery for each individual patient. A total of 27 patients (28 knees) awaiting unicompartmental knee arthroplasty were randomly assigned to have the operation performed either with the assistance of the Acrobot or conventionally. CT scans were obtained with coarse slices through hips and ankles and fine slices through the knee joint. Preoperative 3D plans were made and transferred to the Acrobot system in theatre, or printed out as a conventional surgical aid. Accurate co-registration was confirmed, prior to the surfaces of the femur and tibia being milled. The outcome parameters included measurements of the American Knee Society (AKS) score and Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index. These measurements were performed pre-operatively and at six, 18 weeks, and 18 months post-operatively. After 18 months two UKA out of the conventional trial (n =15) had been revised into a total knee replacement (TKA), whereas there were no revisions in the Acrobot trial group (n = 13). Using an active constrained robot to assist the surgeon was significantly more accurate than the conventional surgical technique. This study has shown a direct correlation between accuracy and improvement in knee scores at 6, 18 weeks and 18 months after surgery. At 18 months there continues to be a significant improvement in the knee scores with again a marked correlation between radiological accuracy and clinical outcome with higher accuracy leading to better function based on the WOMAC and American Knee Society Score

Introduction. Unicompartmental knee arthroplasty (UKA) is becoming an increasingly popular option in single compartment osteoarthritis. As a result, diverse re-operations including revisions to total knee arthroplasty (TKA) has also increase. The objective of this study is to investigate the distribution of causes of re-operations after UKA and to analyze the types of re-operations. Method. We retrospectively reviewed 691 UKAs performed on 595 patients between January 2003 and December 2011. Except in one case, all UKAs were performed for medial compartment osteoarthritis of the knee. The UKAs were performed in 487 (81.8%) women and 108 (18.2%) men. The mean age at the time of UKA was 61.5 years (47 to 88 years). Mobile-bearing designs were implanted in 627 (90.7%) knees (626- Oxford knee and 1- Scorpio knee) and fixed designs were implanted in 64 (9.3%) knees (42- Tornier and 18- Zimmer). The mean interval between UKA and second operation was 15.4 months (10 days to 10 years) and between second and third operation was 7.7 months (5 weeks to 17 months). In the re-operation group, there were 50 knees (48 patients) with 38 female and 10 male patients. Results. In our study, the burden of a re-operation after the initial UKA was 8.7%with, the total number of re-operation of 60. There was 50 cases of second operations (n = 45 mobile, n = 5 fixed), and 10 cases of second re-operation. The most common cause of a second re- operation after a mobile-bearing UKA was the dislocation of the meniscal bearing (32%), followed by component loosening (20%), the formation of a cement loose body (14%), unexplained pain (12%), infection (6%), periprosthetic fracture (4%), and others (2%). For the fixed-bearing UKA, the causes of a second operation were loosening (4%), unexplained pain (4%), and bearing wear (2%). 10 cases required a 3rd operation at mean time interval of 7.7 months, of them 7 cases (70%) had liner exchange at their 2nd operation. Discussion and conclusion. The most common cause of a second re-operation after a mobile-bearing UKA was the dislocation of the bearing, followed by component loosening and the formation of a cement loose body. After a fixed-bearing UKA, component loosening and unexplained pain were the most common causes of re-operation. In cases which underwent a third operation, 70 percent had liner exchange with or without some minor procedure at the time of the 2ndoperation. All were converted to TKA at their 3rd operation at a mean time interval of only 7.7 months. Based on our observations, we recommend a cause-based approach to the management of primary and failed UKA to help minimize the possibility of second and third operations. Furthermore caution should be undertaken when contemplating liner exchange as treatment option in cases involving mobile-bearing UKA

Introduction: In recent years some countries have shown increasing interest and use of unicompartmental knee arthroplasty (UKA). Several studies have reported increasing use of UKA for osteoarthritis in younger patients with low revision rates. The aim of this study was to determine the outcome of UKA by combining two national databases containing prospectively collected data. Method: Over 50 000 UKA procedures were analyzed to determine the cumulative percentage revision (CPR). Any reason for revision was used as the end point. The analysis was stratified according to age, gender and type of prosthesis to determine outcomes in patients younger than 65 years. Result: In this study both countries showed declining use of UKA in terms of the proportion of knee replacement procedures and of absolute numbers undertaken per year. The seven year CPR of UKA in patients younger than 65 years was 16.2%, and at 10 years was 17.5%. No significant difference was found between gender, however outcome did vary depending on the type of prosthesis used. Conclusion: This study reports the outcomes from the two largest databases of UKA. Within 10 years of UKA a substantial number of revisions were seen in patients younger than 65 years, with varying results depending on the type of prosthesis used

Introduction: Minimally invasive surgery (MIS) has recently been proposed for unicompartmental arthroplasty to allow quick function recovery. The purpose of this study is to evaluate retrospectively the indications in which this technique would have been possible and successful. Methods: The requirements for the minimal invasive technique are: a pre-operative flexion of 100° and a lesion limited to one compartment of the knee. The preoperative status, operative findings and clinical outcome of 160 cases of unicompartmental knee arthroplasty (MG, Zimmer) were analyzed to determine whether the criteria for MIS would have been possible. Results: Preoperatively 12 knees had a flexion less than 100°. Postoperatively four of them had a limited flexion ranging from 90° to 100°. In 53 knees (33 %), peripheral osteophytes were removed on the opposite tibiofemoral joint. None of them were revised for progression of osteoarthritis. In 33 knees (21 %) a patelloplasty was associated to the procedure for peripheral osteophytes. Two of them were revised at 12 and 20 months for osteoarthritis progression. Discussion: Removal of peripheral osteophytes can be successfully associated to the unicompartmental procedure when using a conventional surgical approach. In 96 of the 160 knees (60 %) MIS was not recommended either for limited preoperative flexion or for peripheral osteophytes. In 2 knees unicompartmental arthroplasty itself was not the correct indication and total knee arthroplasty would have been the right solution. Finally, in 62 of the 160 knees (39 %) unicompartmental arthroplasty using MIS was indicated. In conclusion unicompartmental knee arthroplasty may be either performed by conventional or minimal approach based on the preoperative clinical and radiological evaluation

The role of unicompartmental knee arthroplasty (UKA) in spontaneous osteonecrosis of the knee (SONK) remains controversial, even though SONK usually involves only medial compartment of the knee joint. We aimed to compare the survival rate and clinical outcomes of UKA in SONK and medial compartment osteoarthritis (MOA) via a meta-analysis of previous studies. MEDLINE database in PubMed, the Embase database, and the Cochrane Library were searched up to January 2018 with keywords related to SONK and UKA. Studies were selected with predetermined inclusion criteria: (1) medial UKA as the primary procedure, (2) reporting implant survival or clinical outcomes of osteonecrosis and osteoarthritis, and (3) follow-up period greater than 1 year. Quality assessment was performed using the risk of bias assessment tool for non-randomised studies (RoBANs). A random effects model was used to estimate the pooled relative risk (RR) and standardised mean difference. The incidence of UKA revision for any reason was significantly higher in SONK than in MOA group (pooled RR = 1.83, p = 0.009). However, the risk of revision due to aseptic loosening and all- cause re-operation was not significantly different between the groups. Moreover, when stratified by the study quality, high quality studies showed similar risk of overall revision in SONK and MOA (p = 0.71). Subgroup analysis revealed worse survival of SONK, mainly related to high failure after uncemented UKA. Clinical outcomes after UKA were similar between SONK and MOA (p = 0.66). Cemented UKA has similar survival and clinical outcomes in SONK and MOA. Prospective studies designed specifically to compare the UKA outcomes in SONK and MOA are necessary

Purpose of the study. The aim of this study was to prospectively study the safety, functional outcomes and complications of all patients undergoing bilateral single-stage sequential (BSSS) unicompartmental knee arthroplasty (UKA) in our unit. Methods and results. 394 cemented UKAs were performed in this unit between 2006–2010. A retrospective review identified 38 patients (76 knees) who underwent BSSS UKA, performed by a single surgeon. Patient demographics were recorded as well as pre and post-operative Oxford knee scores, tourniquet times, time to mobilisation, length of in-patient stay and any complications. There were 22 women and 16 men with a mean age of 64. The mean duration of follow-up was 30 months. The mean total tourniquet time was 83 minutes. The mean time to mobilisation was 18 hours and the average length of stay was 3.5 days. This compares favourably with an institutional average length of stay of two days for a single UKA. There was a significant improvement in the mean pre- to post-operative Oxford Knee Score (from 14 to 34, p< 0.0001). One patient required operative fixation of a tibial plateau fracture after sustaining a mechanical fall two months following surgery. There were no other major complications, including thrombo-embolic events or deep infections. Two patients required excision of a superficial suture granuloma. Conclusion. BSSS UKA provide significant improvement in patient function and can be performed safely with a low complication rate. Patients can benefit from a single hospital admission and anaesthetic whilst the shorter total in-patient stay reduces costs incurred by the hospital

Aim: To study of the results of the first 100 Miller-Galante, unicompartmental knee replacements performed by one surgeon over the period from May 1990 to November 1996, with particular reference to the failure mechanisms. Method: A cohort of 100 patients has been followed up prospectively on a biennial basis. They have been assessed using the Nottingham Knee Proforma of Tew & Waugh. An up-dated review was carried out of the cases for the preparation of this presentation. Results:. Alive, knee functioning satisfactorily – 57. Dead, knee functioning satisfactorily – 21. Lost to follow up – 10. Significant symptoms, not revised – 2. Infection – 1 case not requiring revision. Revised – 9. Due for revision – 1. Of the 32 patients over the age of 74 at the time of replacement none have required revision (18 still alive). Reasons for revision:. 6 developed degeneration in another compartment. 2 had unexplained pain. 1 developed loosening of the tibial component (19 components found to be well fixed to bone at revision). 1 developed significant wear and is due for revision. Conclusions: This prosthesis remains a surgical option for treatment of unicompartmental knee osteoarthrosis. As judged on survival it appears to be superior to high tibial osteotome (HTO) but it appears to be inferior to total knee replacement (TKR). It is easier to revise than failed HTO or TKR. Careful patient selection is obviously required

Unicompartmental knee replacements offer improved function with more rapid recovery compared to TKR. There is no published experience with introducing this procedure as a day case in the UK. We report on our experience with a new protocol allowing the patient to be discharged on the day of surgery. A new combination of anaesthetic and surgical techniques are employed. Paracetamol, ibuprofen and pregabalin are given pre-operatively. Patients receive a GA and a subsartorial saphenous nerve block is administered under ultrasound control. The surgery is performed using a routine minimally invasive technique. The joint and surrounding tissues are infiltrated with a combination of LA and adrenaline. Wound closure is with subcutaeneous suture and tissue glue. Patients are mobilised on the day of surgery and if comfortable discharged on paracetamol, codeine, ibuprofen, tramadol P.R.N and buprenorphine patch. Length of stay, pain scores, presence of nausea/vomiting, dizziness, drowsiness, post-operative bleeding and patient satisfaction are all recorded. 18 out of 19 patients have been discharged on the day of surgery. All record high satisfaction. Patients can be safely discharged on the day of surgery after UKR with high levels of satisfaction. We believe we are the first unit in the UK to achieve this