Abstract. Background. Oxidized zirconium (OxZr) has been introduced as an alternative bearing for femoral components in Total Knee Arthroplasty (TKA). It has a ceramic-like zirconium oxide outer layer with a low coefficient of friction. Early studies have found OxZr TKA to have a low incidence of early failure in young high demand patients. Currently no study has reported on the outcome of these implants beyond ten years. Objectives. The purpose of our study was to present an in-depth 15-year survival analysis of cemented Profix II OxZr TKA. Study Design & Methods. Data was collected prospectively and survival analysis undertaken with multiple strict end points. Complication rates were recorded and patient reported outcomes were measured. Results. 617 Profix II OxZr TKAs were performed over four years. Forty-nine patients underwent reoperation. Aseptic tibial loosening was the most common cause of failure (32.7%) on average occurring 2.8 years post primary procedure. There was one recorded failure due to loosening of the zirconium femoral component. Revision rate at 15-years was 6.38%. Cumulative survivorship was 91.52% with failure considered to be reoperation for any reason. WOMAC score improved in 86% of patients by year 1. The average score improved by 21.2 points and met the standard for minimum clinically important difference. Conclusions. This study presents the first 15-year survival analysis of cemented Profix II OxZr TKA. Our data supports current literature on the long-term survivorship of oxidised zirconium total knee replacements

Aims. To perform an incremental cost-utility analysis and assess the impact of differential costs and case volume on the cost-effectiveness of robotic arm-assisted unicompartmental knee arthroplasty (rUKA) compared to manual (mUKA). Methods. This was a five-year follow-up study of patients who were randomized to rUKA (n = 64) or mUKA (n = 65). Patients completed the EuroQol five-dimension questionnaire (EQ-5D) preoperatively, and at three months and one, two, and five years postoperatively, which was used to calculate quality-adjusted life years (QALYs) gained. Costs for the primary and additional surgery and healthcare costs were calculated. Results. rUKA was associated with a relative 0.012 QALY gain at five years, which was associated with an incremental cost per QALY of £13,078 for a unit undertaking 400 cases per year. A cost per QALY of less than £20,000 was achieved when ≥ 300 cases were performed per year. However, on removal of the cost for a revision for presumed infection (mUKA group, n = 1) the cost per QALY was greater than £38,000, which was in part due to the increased intraoperative consumable costs associated with rUKA (£626 per patient). When the absolute cost difference (operative and revision costs) was less than £240, a cost per QALY of less than £20,000 was achieved. On removing the cost of the revision for infection, rUKA was cost-neutral when more than 900 cases per year were undertaken and when the consumable costs were zero. Conclusion. rUKA was a cost-effective intervention with an incremental cost per QALY of £13,078 at five years, however when removing the revision for presumed infection, which was arguably a random event, this was no longer the case. The absolute cost difference had to be less than £240 to be cost-effective, which could be achieved by reducing the perioperative costs of rUKA or if there were increased revision costs associated with mUKA with longer follow-up. Cite this article: Bone Jt Open 2023;4(11):889–898

Abstract. INTRODUCTION. To preserve knee function and reduce degenerative, meniscal tears should be repaired where possible. Meniscal wrapping with collagen matrices has shown promising clinical outcome (AAOS meniscal algorithm), however there is limited basic science to support this. AIM. to model the contact pressures on the human tibial plateau beneath a (1) a repaired radial meniscal tear and (2) a wrapped and repaired radial meniscal tear. METHODOLOGY. Complete anterolateral radial tears were formed across 4 lateral human menisci, before repairing with ‘rip-stop’ H sutures using 2mm Arthrex Meniscal Suture tape. This was then repeated with the addition of a ChondroGide collagen matrix wrapping. From this experimental setup a finite element (FE) analysis model was construted. FE models of the two techniques (i) suture alone and (ii) suture and collagen-matrix wrap, were then modelled; bone was linear elastic, articular cartilage was a hyperelastic Yeoh model, and a linear elastic and transversely isotropic material model for the meniscus. The contact areas of the articulating surfaces, meniscus kinematics, and stress distribution around the repair were compared between the two systems. RESULTS. Meniscal suture-tape repair had higher local stresses and strains (σ_max=51 MPa ε_max=25%) around the repair compared to with Collagen wrapping (σ_max=36.6MPa ε_max=15%). Radial displacement and pressure on the meniscal contact surfaces were higher in the suture only repair. CONCLUSION. Collagen-matrix wrapping strengthens the repair, reducing local peak stresses and strains around the suture-tape. This could reduce the chance of suture-tape pull-out and subsequent repair failure

Aims. The aim of this study was to estimate the incremental use of resources, costs, and quality of life outcomes associated with surgical reconstruction compared to rehabilitation for long-standing anterior cruciate ligament (ACL) injury in the NHS, and to estimate its cost-effectiveness. Methods. A total of 316 patients were recruited and randomly assigned to either surgical reconstruction or rehabilitation (physiotherapy but with subsequent reconstruction permitted if instability persisted after treatment). Healthcare resource use and health-related quality of life data (EuroQol five-dimension five-level health questionnaire) were collected in the trial at six, 12, and 18 months using self-reported questionnaires and medical records. Using intention-to-treat analysis, differences in costs, and quality-adjusted life years (QALYs) between treatment arms were estimated adjusting for baseline differences and following multiple imputation of missing data. The incremental cost-effectiveness ratio (ICER) was estimated as the difference in costs divided by the difference in QALYs between reconstruction and rehabilitation. Results. At 18 months, patients in the surgical reconstruction arm reported higher QALYs (0.052 (95% confidence interval (CI) -0.012 to 0.117); p = 0.177) and higher NHS costs (£1,017 (95% CI 557 to 1,476); p < 0.001) compared to rehabilitation. This resulted in an ICER of £19,346 per QALY with the probability of surgical reconstruction being cost-effective of 51% and 72% at a willingness-to-pay threshold of £20,000 and £30,000 per QALY, respectively. Conclusion. Surgical reconstruction as a management strategy for patients with long-standing ACL injury is more effective, but more expensive, at 18 months compared to rehabilitation management. In the UK setting, surgical reconstruction is cost-effective. Cite this article: Bone Joint J 2024;106-B(1):38–45

Abstract. Background. There is a trend towards minimising length of stay (LOS) after total knee arthroplasty (TKA), as longer LOS is associated with poorer outcomes and higher costs. Patient factors known to influence LOS after TKA include age and ASA grade. Evidence regarding body mass index (BMI) in particular is conflicting. Some studies find that increased BMI predicts greater LOS, while others find no such relationship. Previous studies have generally not examined socioeconomic status, which may be a confounder. They have generally been conducted outside the UK, and prior to the Covid-19 pandemic. Methods. We conducted a retrospective cohort study of 1031 primary TKAs performed 01-04-2021 to 31-12-2021, after resumption of elective surgery in our centre. A multivariate regression analysis was performed using a Poisson model over pre-operative variables (BMI, age, gender, ASA grade, index of multiple deprivation, and living arrangement) and peri-operative variables (AM/PM operation, operation side, duration, and day of the week). Results. Mean LOS was 2.6 days. BMI had no effect on LOS (p > 0.05). Longer LOS was experienced by patients of greater age (p < 0.001), increased ASA grade (p < 0.001), living alone (p < 0.01), PM start time (p < 0.001), and longer operation duration (p < 0.01). Male patients had shorter LOS (p < 0.001). Index of multiple deprivation had no effect (p > 0.05). Conclusion. BMI had no effect on LOS after TKA. Being female and living alone are significant risk factors which should be taken in to account in pre-operative planning

Abstract

Patellofemoral Arthroplasty (PFA) is an alternative to TKA for patellofemoral osteoarthritis that preserves tibiofemoral compartments. It is unknown how implant positioning affects biomechanics, especially regarding the patella. This study analysed biomechanical effects of femoral and patellar component position, hypothesising femoral positioning is more important.

Nine cadaveric knees were studied using a repeated-measures protocol. Knees were tested intact, then after PFA implanted in various positions: neutral (as-planned), patellar over/understuffing (±2mm), patellar tilt, patellar flexion, femoral rotation, and femoral tilt (all ±6°). Arthroplasties were implemented with CT-designed patient-specific instrumentation. Anterior femoral cuts referenced Whiteside's line and all femoral positions ensured smooth condyle-to-component transition. Knee extension moments, medial patellofemoral ligament (MPFL) length-change, and tibiofemoral and patellofemoral kinematics were measured under physiological muscle loading. Data were analysed with one-dimensional statistical parametric mapping (Bonferroni-Holm corrected).

PFA changed knee function, altering extension moments (p<0.001) and patellofemoral kinematics (p<0.05), but not tibiofemoral kinematics. Patellar component positioning affected patellofemoral kinematics: over/understuffing influenced patellar anterior translation and the patellar tendon moment arm (p<0.001). Medially tilted patellar cuts produced lateral patellar tilt (p<0.001) and vice versa. A similar inverse effect occurred with extended/flexed patellar cuts, causing patellar flexion and extension (p<0.001), respectively. Of all variants, only extending the patellar cut produced near-native extension moments throughout. Conversely, the only femoral effect was MPFL length change between medially/laterally rotated components.

PFA can restore native knee biomechanics. Provided anterior femoral cuts are controlled and smooth condyle-to-component transition assured, patellar position affects biomechanics more than femoral, contradicting the hypothesis.

Abstract

Aims

A functional anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) has been assumed to be required for patients undergoing unicompartmental knee arthroplasty (UKA). However, this assumption has not been thoroughly tested. Therefore, this study aimed to assess the biomechanical effects exerted by cruciate ligament-deficient knees with medial UKAs regarding different posterior tibial slopes.

Abstract. Introduction. The role of patellar resurfacing in total knee arthroplasty remains controversial. We questioned the effect of patellar resurfacing on the early and late revision rates after total knee arthroplasty. Materials and Methods. We analysed the data of cumulative revisions of primary knee replacement from the NJR 19th Annual Report. NJR included secondary patellar resurfacing as a revision. We compared differences in the 3-year and 15-year revision rates between the patellar resurfacing and non-resurfacing for the different combinations of total knee replacements using a paired t-test. We performed subgroup analysis for the five combinations with the highest volumes. Results. Twenty-seven implant combinations had the 15-year revision rates reported. Patellar resurfacing group had lower mean 3-year revision rate of 1.68 (SD 0.7) compared to 2.02 (SD 0.9) in non-resurfacing group (p=0.05). However, 15-year revision rate was similar between the two groups (mean 5.7, SD 2.1 vs. mean 5.7, SD 2.2; p = 0.46). High volume implants showed that two combinations (NexGen CR and PS) had similar revision rates at 3 and 15 years between resurfacing and non-resurfacing groups. Three combinations (PFC Sigma CR and PS and Genesis 2 CR) had higher revision rate in non-resurfacing group at 3 years (p=0.01) and the difference persisted at 15 years (p=0.05). Conclusions. Although revision rate in total knee arthroplasty was higher without patellar resurfacing at 3 years, at 15 years the difference was not significant. However, the higher revision without patellar resurfacing can be prosthetic combination specific which surgeons need to be aware of

Abstract

Abstract

Abstract

Abstract. Introduction. Revision total knee arthroplasty (RTKA) is a complex procedure with higher rates of re-revision, complications and mortality compared to primary TKA. We report the effects of the establishment of a Revision Arthroplasty Network (The East Midlands Specialist Orthopaedic Network; EMSON). Methodology. The Revision Arthroplasty Network was established in January 2015 and covered the Nottinghamshire and Lincolnshire areas of England. This comprises a collaborative weekly multidisciplinary meeting where upcoming RTKA procedures are discussed, and a plan agreed. Using the Hospital Episode Statistics database, RTKA procedures carried out between 2011 and 2018 from the five EMSON hospitals were compared to all other hospitals in England. Age, sex, and Hospital Frailty Risk scores were used as covariates. The primary outcome was re-revision surgery within 1 year of the index revision. Secondary outcomes were re-revision surgery within two years, any complication within one and two years and median length of stay. Results. 33,828 RTKA procedures were performed across England; 1,028 (3.0%) were conducted within EMSON. Re-revision rates within 1 year were 11.6% and 7.4% pre- and post-intervention respectively within the network. This compares to a pre-post change from 11.7% to 9.7% for the rest of England. In comparative interrupted time-series analysis, there was a significant immediate improvement in re-revision rates for EMSON hospitals compared to the rest of England at 1 year (p = 0.024) and 2 years (p=0.032). Conclusion. Re-revision rates for RTKA improved significantly at one and two years with the introduction of EMSON, when compared to the rest of England

Aims

Classifying trochlear dysplasia (TD) is useful to determine the treatment options for patients suffering from patellofemoral instability (PFI). There is no consensus on which classification system is more reliable and reproducible for the purpose of guiding clinicians’ management of PFI. There are also concerns about the validity of the Dejour Classification (DJC), which is the most widely used classification for TD, having only a fair reliability score. The Oswestry-Bristol Classification (OBC) is a recently proposed system of classification of TD, and the authors report a fair-to-good interobserver agreement and good-to-excellent intraobserver agreement in the assessment of TD. The aim of this study was to compare the reliability and reproducibility of these two classifications.

Abstract

Aims

The aims of this study were to assess mapping models to predict the three-level version of EuroQoL five-dimension utility index (EQ-5D-3L) from the Oxford Knee Score (OKS) and validate these before and after total knee arthroplasty (TKA).

Abstract

Abstract

Introduction. Identifying knee osteoarthritis patient phenotypes is relevant to assessing treatment efficacy. Biomechanical variability has not been applied to phenotyping, yet features may be related to outcomes of total knee arthroplasty (TKA), an inherently mechanical surgery. This study aimed to i) identify biomechanical phenotypes among TKA candidates based on demographic and gait mechanic similarities, and ii) compare objective gait improvements between phenotypes post-TKA. Methods. TKA patients underwent 3D gait analysis one-week pre (n=134) and one-year post-TKA (n=105). Principal component analysis was applied to frontal and sagittal knee angle and moment gait waveforms, extracting major patterns of variability. Demographics (age, sex, BMI), gait speed, and frontal and sagittal pre-TKA angle and moment principal component (PC) scores previously found to differentiate sex, osteoarthritis (OA) severity, and symptoms of TKA recipients were standardized (mean=0, SD=1, [134×15]) to perform multidimensional scaling and machine learning based hierarchical clustering. Final clusters were validated by examining inter-cluster differences at baseline and gait changes (Post. PCscore. –Pre. PCscore. ) by k-way Chi-Squared, and ANOVA tests. Results. Four (k=4) TKA candidate groups yielded optimum clustering metrics, interpreted as 1) high-functioning males, 2) older stiff-kneed males, 3) slower stiff-kneed females, and 4) high-functioning females. Pre-TKA, higher-functioning clusters (1 & 4) had more dynamic loading/un-loading kinetic patterns during stance (flexion moment PC2, 3<2<4<1, P<0.001; adduction moent PC2; 3,2<4<1; P<0.001). Post-TKA, higher-functioning clusters demonstrated less gait improvement (flexion angle ΔPC2, 1,2,4<3, P<0.001; flexion moment ΔPC2, 4<2,3, P<0.001; adduction moment ΔPC2, 1<3, P=0.01). Conclusions. TKA candidates can be characterized by four clusters, interpreted as 1) high-functioning males, 2) older stiff-kneed males, 3) slower stiff-kneed females, and 4) high-functioning females, differing by demographics and biomechanical severity features. Functional gains after TKA were cluster-specific; stiff-gait clusters experienced more improvement, while higher-functioning clusters demonstrated some functional decline. Results suggest the presence of cohorts who may not benefit functionally from TKA. Cluster profiling may aid in triaging and developing osteoarthritis management and surgical strategies that meet individual or group-level function needs. For figures, tables, or references, please contact authors directly

Introduction. Robotic assisted Total Knee Arthroplasty (rTKA), provides surgeons with preoperative planning and real-time data allowing for continuous assessment of ligamentous tension and range-of-motion. Using this technology, soft tissue protection, reduced early post-operative pain and improved patient satisfaction have been shown. These advances have the potential to enhance surgical outcomes and may also reduce episode-of-care (EOC) costs for patients, payers, and hospitals. The purpose of this study was to compare robotic assisted vs. manual total knee arthroplasty: 1) 90-day episode-of-care (EOC) costs; 2) index costs; 3) lengths-of-stay (LOS); 4) discharge disposition; and 5) readmission rates. Methods. TKA procedures were identified using the Medicare 100% Standard Analytic Files including; Inpatient, Outpatient, Skilled Nursing (SNF) and Home Health. Members included patients with rTKA or manual TKA (mTKA) between 1/1/2016-3/31/2017. To account for potential baseline differences, propensity score matching (PSM) was performed in a 1-to-5 ratio, robotic to manual based on age, sex, race, geographic division, and comorbidities. After PSM, 519 rTKA and 2,595 mTKA were identified and included for analysis. Ninety-day episode-of-care cost, index cost, LOS, discharge disposition and readmission rates were assessed. Results. Overall 90-day EOC costs were $2,391 less for rTKA patients ($18,568 vs. $20,960; p<.0001). Index facility cost and LOS were also less for rTKA patients by $640 ($12,384 vs. $13,024; p=.0001) and 0.7 days (p<.0001). Additionally, rTKA patients were discharged to SNF less frequently (12.52% vs. 21.70%; p<.0001) and home with health aid (56.65% vs. 46.67%; p<.0001) or self-care (27.55% vs. 23.62%; p=.0566) more frequently and had a 90-day readmission reduction of 33% (p=.0423). Conclusion. Robotic assisted TKA resulted in an overall lower 90-day episode-of-care cost when compared to manual TKA. The 90-day EOC cost savings of rTKA were driven by reduced facility costs, LOS and readmissions, and an economically beneficial discharge destination