David W. Murray

Aims: To evaluate differences in the efficacy and safety of low molecular weight heparin (LMWH) and direct oral anticoagulants (DOACs) used for venous thromboembolism (VTE) prophylaxis after elective total hip arthroplasty (THA). Methods: This systematic review and meta-analysis reviewed MEDLINE, Embase, and CENTRAL from conception to 13 December 2025, for any randomized controlled trials (RCTs) comparing the efficacy (VTE risk) and safety (bleeding risk) of LMWH and DOACs after elective THA. Pooled odds ratios (ORs) of VTE, bleeding, reoperation, and mortality risks were assessed. Results: A total of 22 RCTs involving 28,112 participants were included. The risk of VTE in the DOAC group was lower compared with the LMWH group (OR 0.62 (95% CI 0.47 to 0.82); p = 0.002), driven by a reduction in deep vein thrombosis (DVT) risk (OR 0.60 (95% CI 0.42 to 0.86); p = 0.008). The findings remained consistent in the subgroup analysis restricted to anticoagulants and dosages licensed for use in the UK. Overall bleeding risk was higher in the DOAC group (OR 1.19 (95% CI 1.03 to 1.38); p = 0.023), but no difference was seen when comparing only UK-licensed anticoagulants and doses (OR 1.06 (95% CI 0.95 to 1.18); p = 0.279). Reoperation risk (OR 1.21 (95% CI 0.75 to 1.93); p = 0.351) and mortality (OR 1.03 (95% CI 0.46 to 2.33); p = 0.937) did not differ between groups. Conclusion: DOACs reduce the risk of VTE and DVT following elective THA compared with LMWH without increasing bleeding risk, for UK-licensed agents and doses. Switching to DOACs could save the NHS £8.6 million per year. New clinical trials are needed to compare the safety and efficacy of UK-licensed DOACs and LWMH with modern postoperative rehabilitation protocols. Cite this article: Bone Joint J 2026;108-B(11):1294–1304.

Background: The cementless Oxford Unicompartmental Knee Arthroplasty (OUKA) was introduced to minimize the risk of aseptic loosening, with evidence supporting its effectiveness for up to 10 years. However, it is not known if the fixation will be reliable thereafter and there is a concern that the interference fit of the cementless components may cause periprosthetic fractures. This prospective cohort study reports the 15-year survival and functional outcomes as well as the incidence of aseptic loosening and periprosthetic fracture. Methods: One thousand consecutive cementless OUKA, implanted between 2004 and 2017 for the recommended indications of antero-medial osteoarthritis (980) or avascular necrosis (20), were independently followed. Survival was assessed using various end points. The primary outcome measure was the Oxford Knee Score (OKS). Results: The mean OKS was 42 (SD 7.8) at 10 years and 41 (SD 8.8) at 15 years. 6% of knees were revised, and 1.2% had nonrevision reoperations. The 15-year survival for all reoperations was 89% (95% CI 86-92), for revision was 90% (CI 87-93), for conversion to TKA was 94% (CI 91-96.1), and for major revision needing revision TKA components was 99.4% (CI 98.8-100). The common causes for revision were lateral compartment arthritis (2.8%), pain (1.0%), bearing dislocation (0.9%), and fractured/worn bearing (0.6%). One aseptic femoral loosening occurred within the first year. There were no periprosthetic fractures. Conclusions: At 15 years, cementless OUKA, when used with the recommended indications and techniques, has excellent functional outcomes and good survival, with only 0.4% of knees needing revisions similar to those of TKA. Fixation was reliably achieved with only 1 case (0.1%) of loosening. This was an early failure of primary fixation of a femoral component due to damage to the fixation hole at surgery. There were no fractures related to the implants. Level of Evidence: The level of evidence is Level IV , therapeutic. See Instructions for Authors for a complete description of levels of evidence.

Background: Unicompartmental knee arthroplasty (UKA) is an effective treatment for unicompartmental end-stage knee arthritis. Simultaneous bilateral UKAs for patients with bilateral knee arthritis can reduce costs, number of anesthetics, and overall rehabilitation time. It is unknown how the long-term outcomes of unilateral and simultaneous bilateral UKAs compare. Methods: In total, 1,939 unilateral and 1,939 simultaneous bilateral medial mobile-bearing UKAs (n = 3,878) from the National Joint Registry were propensity score matched. Kaplan-Meier and Cox regression were used to compare implant survival, revision indications, and mortality. Results: The 10-year implant survival in the simultaneous bilateral group was 92% (95% confidence interval [CI] 90-94) and in the unilateral group was 90% (95% CI 88-92). The simultaneous bilateral group had a lower revision risk (hazard ratio [HR] 0.73, p = 0.01). Revisions for pain were lower in the bilateral group (0.5% vs. 1.2%, p = 0.01). There were no differences in patient mortality. Subgroup analyses found similar trends in 10-year implant survival and revision risk with both cementless (simultaneous bilateral 98% CI 95-99; unilateral 95% CI 91-98; HR 0.66, p = 0.27) and cemented fixation (simultaneous bilateral 91% CI 89-93; unilateral 90% CI 88%-92%; HR 0.85, p = 0.28). Conclusions: Simultaneous bilateral UKAs had better 10-year implant survival and similar mortality to compared with single-unilateral UKAs. For patients with severe symptomatic bilateral unicompartmental knee osteoarthritis, simultaneous bilateral UKAs could be considered to be a safe and effective procedure, particularly as only one operation and postoperative recovery is required. Level of Evidence: Level IV . See Instructions for Authors for a complete description of levels of evidence.

Background: Patients with symptoms of pain and restricted function related to knee osteoarthritis are typically offered a knee replacement. However, a proportion remain dissatisfied with their outcomes, and the failure risk is disproportionately higher in the young. Knee joint distraction may be an intervention to postpone the time to knee replacement in this patient population. Objective and main outcome measure: The primary objective of the Knee Arthroplasty versus Joint Distraction Study for Osteoarthritis (KARDS) was to evaluate the effectiveness of knee joint distraction compared to knee replacement based on patient-reported pain 12 months post surgery using the Knee Injury and Osteoarthritis Outcomes Score pain score as the primary outcome. Design and methods: KARDS was an open-label, two-arm individually randomised controlled non-inferiority trial with an embedded 12-month internal pilot phase and process evaluation to evaluate recruitment feasibility. A hybrid expertise design was used to account for surgeon expertise and potential lack of individual equipoise. The trial was closed to recruitment early following cessation of elective orthopaedic surgery secondary to COVID-19 pandemic. Descriptive statistics are reported. Setting: United Kingdom National Health Service Trusts. Participants: Adult patients aged < 65 years with symptoms severe enough to warrant knee replacement, in the opinion of the treating clinician. Interventions: Participants were randomised to receive either knee joint distraction (static distraction of 5 mm, using external fixator for 6 weeks) or knee replacement. Results: Twenty-four participants were randomised from a single centre between March 2021 and October 2022 with minimum 3-month safety follow-up post surgery. Eleven participants were randomised to knee joint distraction and 13 to knee replacement. Seventeen patients were male (71%), median age 60 (47–65) years. One patient withdrew due to being medically unfit for surgery and two received a different treatment than which they were randomised (one crossover from each arm). The median Knee Injury and Osteoarthritis Outcomes Score pain score in the knee joint distraction group improved from 38.9 (22–50) at baseline to 55.6 (0–100) at 12 months, corresponding scores in the knee replacement improved from 30.6 (6–36) to 75.0 (50–100). Adverse events were more common with knee joint distraction, pin site infection being the commonest complications ( n = 4, 58%). As part of process evaluation, we conducted semistructured qualitative interviews with staff in secondary care and with study participants. Data were analysed using thematic content analysis. One overarching theme emerged: ‘An unexpected journey’, which encapsulates staff and participants’ experiences. Conclusion: Reduced research capacity and the suspension of elective surgery following the COVID-19 pandemic caused significant recruitment barriers. Despite early termination, KARDS demonstrated that patients were willing to be recruited to a trial investigating a novel treatment for knee osteoarthritis and the trial was feasible and implementable. The limited results indicated that the technique is safe with no safety concerns. Clinical and cost-effectiveness of knee joint distraction remains uncertain. The embedded KARDS process evaluation has provided helpful insights. Limitations: Reduced research capacity at sites and suspension of elective surgery services within the United Kingdom following COVID-19 caused significant recruitment barriers to KARDS. All the recruited patients in both arms of the study were White. Future work: As a commissioned piece of research with delivery significantly impacted by the National Health Service environment post-COVID and the impact on National Health Service surgical services, the research question remains highly relevant. Any future research in this field can be helped by the pilot data published here along with the lessons learnt. Funding: This synopsis presents independent research funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme as award number 17/122/06.

Aims: Mixed clinical results have been reported following the use of lateral unicompartmental knee arthroplasty (UKA) in patients with isolated lateral compartment osteoarthritis (OA) of the knee. Although this procedure may be appropriate for use in about 10% of knees needing arthroplasty, it is only used in about 1%. The aim of this study was to determine the medium-term results for the Fixed Lateral Oxford (FLO) UKA.Methods: We report the clinical results and survival for 305 consecutive FLO UKAs implanted in 279 patients between July 2015 and August 2022. A total of 283 knees (93%) satisfied the recommended surgical indications. The mean age of the patients was 70.8 years (SD 11), their mean BMI was 28.4 kg/m² (SD 5.4), and 219 (72%) were female. Isolated lateral compartment OA was the indication for 298 operations (98%). The mean follow-up was 4.3 years (1 to 8). The Oxford Knee Score (OKS) was recorded pre- and postoperatively. The revision status of all knees was known.Results: There were four revisions (1%): two were conversions to a total knee arthroplasty (TKA) for instability and progressive OA and two had the addition of a medial UKA for medial compartment OA. Three other UKAs required a reoperation. At the last follow-up, the mean OKS was 40.9 (SD 7.8), a mean increase of 20 points from the preoperative score. The cumulative rate of survival with any reoperation, including revision, as the endpoint, at seven years, was 96% (95% CI 91 to 100), with revision as the endpoint was 98% (95% CI 94 to 100) and with revision to a TKA as the endpoint was 99% (95% CI 96 to 100). No revisions required revision TKA components. When those who underwent surgery for indications which were outside the recommended indications were excluded, there were only two revisions, both with the addition of a medial UKA for progressive OA, resulting in a seven-year cumulative survival with revision as the endpoint of 99% (95% CI 93 to 100).Conclusion: This study involved the largest published cohort of fixed-bearing lateral UKAs. The good clinical outcomes and medium-term survival of the FLO UKA, particularly in patients satisfying the recommended indications, suggest that it is an excellent alternative to TKA for the treatment of patients with isolated OA of the lateral compartment of the knee.Cite this article: Bone Joint J 2025;107-B(4):432–439.

Background: Unicompartmental knee replacement (UKR) is an effective treatment for end-stage medial compartment osteoarthritis, but there can be problems with fixation. The cementless UKR was introduced to address this issue. It is unknown how its functional outcomes compare with those of the cemented version on a national scale. We performed a matched comparison of the clinical and functional outcomes of cementless and cemented UKRs. Methods: Using the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man (NJR), 14,764 Oxford UKRs with linked data regarding patient-reported outcomes were identified. A total of 6,906 UKRs (3,453 cemented and 3,453 cementless) were propensity score matched on the basis of patient, surgical, and implant factors. Results: The 10-year cumulative implant survival rate was 93.0% (95% confidence interval [CI], 90.0% to 95.1%) for cementless UKRs and 91.3% (95% CI, 89.0% to 93.0%) for cemented UKRs. The cementless UKR group had a significantly lower revision risk (hazard ratio [HR], 0.74; p = 0.02). Subgroup analyses showed a stronger effect size (HR, 0.66) among UKRs performed by high-caseload surgeons (i.e., surgeons performing ≥30 UKRs/year). In the overall cohort, the postoperative Oxford Knee Score (OKS) in the cementless group (mean and standard deviation, 39.1 ± 8.7) was significantly higher (p = 0.001) than that in the cemented group (38.5 ± 8.6). The cementless group gained a mean of 17.6 ± 9.3 points in the OKS postoperatively and the cemented group gained 16.5 ± 9.6 points, with a difference of 1.1 points between the groups (p < 0.001). The difference in OKS points gained postoperatively was highest among UKRs performed by high-caseload surgeons, with the cementless group gaining 1.8 points more (p < 0.001) than the cemented group. Conclusions: The cementless UKR demonstrated better 10-year implant survival and postoperative functional outcomes than the cemented UKR. The difference was largest among UKRs performed by high-caseload surgeons, with the cementless fixation group having an HR for revision of 0.66 and an approximately 2-point greater improvement in the OKS compared with the cemented fixation group. Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Background: This study aimed to establish an equation for calculating cup ante-inclination (AI) from radiographic cup inclination and anteversion, to validate this equation in a total hip arthroplasty (THA) cohort, and to test whether achieving previously described radiographic cup inclination and anteversion targets would also satisfy sagittal cup AI targets. Methods: A mathematical equation linking cup AI, radiographic inclination (RI), and anteversion (RA) was determined: tan(AI) = tan(RA)/cos(RI). Supine and standing anteroposterior and lateral radiographs of 440 consecutive THAs were assessed to measure cup RI and RA and spinopelvic parameters, including cup AI, using a validated software tool. Whether orientation within previously defined RI and RA targets was associated with achieving the AI target and satisfying the sagittal component orientation (combined sagittal index, 205° to 245°) was tested. Results: The cups in the THA cohort had a measured mean inclination (and standard deviation) of 43° ± 7°, anteversion of 26° ± 9°, and AI of 34° ± 10°. The calculated cup AI was 34° ± 12°. A strong correlation existed between measured and calculated AI (r = 0.75; p < 0.001), with a mean error of 0° ± 8°. The inclination and anteversion targets were both satisfied in 194 (44.1%) to 330 (75.0%) of the cases, depending on the safe zone targets that were used, and 311 cases (70.7%) satisfied the AI target. Only 125 (28.4%) to 233 (53.0%) of the cases satisfied the AI target as well as the inclination and anteversion targets. Satisfying inclination and anteversion targets was not associated with increased chances of satisfying the AI target. Conclusions: Achieving optimal cup inclination and anteversion does not ensure optimal orientation in the sagittal plane. The equation and nomograms provided can be used to determine and visualize how the 2 planes used for evaluating the cup orientation and the pertinent angles relate, potentially aiding in preoperative planning.