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

Whether to use total or unicompartmental knee replacement (TKA/UKA) for end-stage knee osteoarthritis remains controversial. Although UKA results in a faster recovery, lower rates of morbidity and mortality and fewer complications, the long-term revision rate is substantially higher than that for TKA. The effect of each intervention on patient-reported outcome remains unclear. The aim of this study was to determine whether six-month patient-reported outcome measures (PROMs) are better in patients after TKA or UKA, using data from a large national joint registry (NJR). We carried out a propensity score-matched cohort study which compared six-month PROMs after TKA and UKA in patients enrolled in the NJR for England and Wales, and the English national PROM collection programme. A total of 3519 UKA patients were matched to 10 557 TKAs. . The mean six-month PROMs favoured UKA: the Oxford Knee Score was 37.7 (95% confidence interval (CI) 37.4 to 38.0) for UKA and 36.1 (95% CI 35.9 to 36.3) for TKA; the mean EuroQol EQ-5D index was 0.772 (95% CI 0.764 to 0.780) for UKA and 0.751 (95% CI 0.747 to 0.756) for TKA. UKA patients were more likely to achieve excellent results (odds ratio (OR) 1.59, 95% CI 1.47 to 1.72, p < 0.001) and to be highly satisfied (OR 1.27, 95% CI 1.17 to 1.39, p <  0.001), and were less likely to report complications than those who had undergone TKA. . UKA gives better early patient-reported outcomes than TKA; these differences are most marked for the very best outcomes. Complications and readmission are more likely after TKA. Although the data presented reflect the short-term outcome, they suggest that the high revision rate for UKA may not be because of poorer clinical outcomes. These factors should inform decision-making in patients eligible for either procedure. Cite this article: Bone Joint J 2015;97-B:793–801

Artificial intelligence and machine-learning analytics have gained extensive popularity in recent years due to their clinically relevant applications. A wide range of proof-of-concept studies have demonstrated the ability of these analyses to personalize risk prediction, detect implant specifics from imaging, and monitor and assess patient movement and recovery. Though these applications are exciting and could potentially influence practice, it is imperative to understand when these analyses are indicated and where the data are derived from, prior to investing resources and confidence into the results and conclusions. In this article, we review the current benefits and potential limitations of machine-learning for the orthopaedic surgeon with a specific emphasis on data quality.

We recently published a paper comparing the incidence of adverse outcomes after unicompartmental and total knee arthroplasty (UKA and TKA). The conclusion of this study, which was in favour of UKA, was dismissed as “biased” in a review in Bone & Joint 360. Although this study is one of the least biased comparisons of UKA and TKA, this episode highlights the biases that exist both for and against UKA. In this review, we explore the different types of bias, particularly selection, reporting and measurement. We conclude that comparisons between UKA and TKA are open to bias. These biases can be so marked, particularly in comparisons based just on national registry data, that the conclusions can be misleading. For a fair comparison, data from randomised studies or well-matched, prospective observational cohort studies, which include registry data, are required, and multiple outcome measures should be used. The data of this type that already exist suggest that if UKA is used appropriately, compared with TKA, its advantages outweigh its disadvantages. Cite this article: Bone Joint J 2017;99-B:12–15

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The aim of this study was to determine satisfaction rates after hip and knee arthroplasty in patients who did not respond to postoperative patient-reported outcome measures (PROMs), characteristics of non-responders, and contact preferences to maximize response rates.

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The cemented Oxford unicompartmental knee arthroplasty (OUKA) features two variants: single and twin peg OUKA. The purpose of this study was to assess the stability of both variants in a worst-case scenario of bone defects and suboptimal cementation.

Aims. To validate the English language Forgotten Joint Score-12 (FJS-12) as a tool to evaluate the outcome of hip and knee arthroplasty in a United Kingdom population. Patients and Methods. All patients undergoing surgery between January and August 2014 were eligible for inclusion. Prospective data were collected from 205 patients undergoing total hip arthroplasty (THA) and 231 patients undergoing total knee arthroplasty (TKA). Outcomes were assessed with the FJS-12 and the Oxford Hip and Knee Scores (OHS, OKS) pre-operatively, then at six and 12 months post-operatively. Internal consistency, convergent validity, effect size, relative validity and ceiling effects were determined. Results. Data for the TKA and THA patients showed high internal consistency for the FJS-12 (Cronbach α = 0.97 in TKAs, 0.98 in THAs). Convergent validity with the Oxford Scores was high (r = 0.85 in TKAs, r = 0.79 for THAs). From six to 12 months, the change was higher for the FJS-12 than for the OHS in THA patients (effect size d = 0.21 versus -0.03). Ceiling effects at one-year follow-up were low for the FJS-12 with just 3.9% (TKA) and 8.8% (THA) of patients achieving the best possible score. Conclusion. The FJS-12 has strong measurement properties in terms of validity, internal consistency and sensitivity to change in TKA and THA patients. Low ceiling effects and good relative validity allow the monitoring of longer term outcomes, particularly in well-performing groups after total joint arthroplasty. Cite this article: Bone Joint J 2017;99-B:218–24

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Corticosteroid injections are often used to manage glenohumeral arthritis in patients who may be candidates for future total shoulder arthroplasty (TSA) or reverse shoulder arthroplasty (rTSA). In the conservative management of these patients, corticosteroid injections are often provided for symptomatic relief. The purpose of this study was to determine if the timing of corticosteroid injections prior to TSA or rTSA is associated with changes in rates of revision and periprosthetic joint infection (PJI) following these procedures.

Aims . To investigate whether pre-operative functional mobility is a determinant of delayed inpatient recovery of activities (IRoA) after total knee arthroplasty (TKA) in three periods that coincided with changes in the clinical pathway. Patients and Methods. All patients (n = 682, 73% women, mean age 70 years, standard deviation 9) scheduled for TKA between 2009 and 2015 were pre-operatively screened for functional mobility by the Timed-up-and-Go test (TUG) and De Morton mobility index (DEMMI). The cut-off point for delayed IRoA was set on the day that 70% of the patients were recovered, according to the Modified Iowa Levels of Assistance Scale (mILAS) (a 5-item activity scale). In a multivariable logistic regression analysis, we added either the TUG or the DEMMI to a reference model including established determinants. Results. Both the TUG (Odds Ratio (OR) 1.10 per second, 95% confidence intervals (CI) 1.06 to 1.15) and the DEMMI (OR 0.96 per point on the 100-point scale, 95% CI 0.95 to 0.98) were statistically significant determinants of delayed IRoA in a model that also included age, BMI, ASA score and ISAR score. These associations did not depend on the time period during which the TKA took place, as assessed by tests for interaction. . Conclusion. Functional mobility, as assessed pre-operatively by the TUG and DEMMI, is an independent and stable determinant of delayed inpatient recovery of activities after TKA. Future research, focusing on improvement of pre-operative functional mobility through tailored physiotherapy intervention, should indicate whether such intervention enhances post-operative recovery among high-risk patients. Cite this article: Bone Joint J 2017;99-B:211–17

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

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Endoprosthetic reconstruction with a distal femoral arthroplasty (DFA) can be used to treat distal femoral bone loss from oncological and non-oncological causes. This study reports the short-term implant survivorship, complications, and risk factors for patients who underwent DFA for non-neoplastic indications.

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Postoperative malalignment of the femur is one of the main complications in distal femur fractures. Few papers have investigated the impact of intraoperative malalignment on postoperative function and bone healing outcomes. The aim of this study was to investigate how intraoperative fracture malalignment affects postoperative bone healing and functional outcomes.

Aims. The aim of this study was to determine the optimal regimen for the management of pain following total knee arthroplasty (TKA) by comparing the outcomes and cost-effectiveness of different protocols implemented at a large, urban, academic medical centre. Patients and Methods. Between September 2013 and September 2015, we used a series of modifications to our standard regimen for the management of pain after TKA. In May 2014, there was a department-wide transition from protocols focused on femoral nerve blocks (FNB) to periarticular injections of liposomal bupivacaine. In February 2015, patient-controlled analgesia (PCA) was removed from the protocol while continuing liposomal bupivacaine injections. Quality measures and hospital costs were compared between the three protocols. Results. The cohort being treated with PCA-less liposomal bupivacaine injections had a significantly higher percentage of patients who were discharged to their home (p = 0.010) and a significantly shorter length of stay (p < 0.001). Patient-reported Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS) scores relating to pain being “well-controlled” and “overall pain management” also favoured this cohort (p = 0.214 and p = 0.463, respectively), in which cost was significantly lower compared with the other two cohorts (p = 0.005). Conclusion. The replacement of FNBs injections and the removal of PCAs, both of which are known to be associated with high rates of adverse outcomes, and the addition of liposomal bupivacaine periarticular injections to a multimodal pain regimen, led to improvements in many quality measures, HCAHPS pain scores, and cost-effectiveness. Cite this article: Bone Joint J 2018;100-B(1 Supple A):55–61

Aims. Risk of revision following total knee arthroplasty (TKA) is higher in patients under 55 years, but little data are reported regarding non-revision outcomes. This study aims to identify predictors of dissatisfaction in these patients. Patients and Methods. We prospectively assessed 177 TKAs (157 consecutive patients, 99 women, mean age 50 years; 17 to 54) from 2008 to 2013. Age, gender, implant, indication, body mass index (BMI), social deprivation, range of movement, Kellgren-Lawrence (KL) grade of osteoarthritis (OA) and prior knee surgery were recorded. Pre- and post-operative Oxford Knee Score (OKS) as well as Short Form-12 physical (PCS) and mental component scores were obtained. Post-operative range of movement, complications and satisfaction were measured at one year. Results . Overall, 44 patients with 44 TKAs (24.9%) under 55 years of age were unsure or dissatisfied with their knee. Significant predictors of dissatisfaction on univariate analysis included: KL grade 1/2 OA (59% dissatisfied), poor pre-operative OKS, complications, poor improvements in PCS and OKS and indication (primary OA 19% dissatisfied, previous meniscectomy 41%, multiply operated 42%, other surgery 29%, BMI > 40 kg/m. 2. 31%, post-traumatic OA 45%, and inflammatory arthropathy 5%). Poor pre-operative OKS, poor improvement in OKS and post-operative stiffness independently predicted dissatisfaction on multivariate analysis. Conclusion. Patients receiving TKA younger than 55 years old should be informed about the increased risks of dissatisfaction. Offering TKA in KL 1/2 is questionable, with a dissatisfaction rate of 59%. Cite this article: Bone Joint J 2016;98-B:1625–34

Aims. The role of high tibial osteotomy (HTO) is being questioned by the use of unicompartmental knee arthroplasty (UKA) in the treatment of medial compartment femorotibial osteoarthritis. Our aim was to compare the outcomes of revision HTO or UKA to a total knee arthroplasty (TKA) using computer-assisted surgery in matched groups of patients. Patients and Methods. We conducted a retrospective study to compare the clinical and radiological outcome of patients who underwent revision of a HTO to a TKA (group 1) with those who underwent revision of a medial UKA to a TKA (group 2). All revision procedures were performed using computer-assisted surgery. We extracted these groups of patients from our database. They were matched by age, gender, body mass index, follow-up and pre-operative functional score. The outcomes included the Knee Society Scores (KSS), radiological outcomes and the rate of further revision. Results. There were 20 knees in 20 patients in each group. The mean follow-up was 4.1 years (2 to 18.7). The mean total KSS at last follow-up was 185.7 (standard deviation (. sd. ) 5) in group 1 compared with 176.5 (. sd. 11) for group 2 (p = 0.003). The mean hip-knee-ankle angle was 180.2° (. sd. 3.2°) in group 1 and 179.0° (. sd. 2.2°) in group 2. No revision was required. Conclusion. We found that good functional and radiological outcomes followed revision of both HTO and UKA to TKA. Revision of HTO showed significantly better functional outcomes. These results need to be further investigated by a prospective randomised controlled trial involving a larger group of patients. Cite this article: Bone Joint J 2016;98-B:1620–4