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Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_13 | Pages 49 - 49
7 Aug 2023
Murray J Murray E Readioff R Gill H
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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.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXIX | Pages 102 - 102
1 Jul 2012
van Duren B Pandit H Tilley S Price M Gill H Murray D Thomas N
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Introduction

Traditional TKR designs exhibit abnormal and unpredictable kinematics: with posterior subluxation in extension and anterior slide with flexion. These can contribute to restricted knee flexion and reduced quadriceps efficiency. Newer designs attempt to provide “guided motion” with the aim of mimicking normal knee kinematics. The Journey (Smith & Nephew) BCS TKR incorporates both an anterior and a posterior cam/post mechanism while Triathlon PS TKR (Stryker) incorporates a posterior cam/post mechanism. This study compares the in-vivo kinematics of these two designs and compares it with normal knee.

Methods

Knee kinematics of 10 patients with Journey-BCS TKR and 11 patients with Triathlon PS TKR; all with excellent clinical outcome (average age: 65) were analysed. Patients underwent fluoroscopic assessment of the knee during a step-up and deep knee bend exercise. 2D fluoroscopic images were recorded. Data was analysed for patella tendon angle (PTA) and contact points using a 3D model fitting technique. This data was compared to normal knee kinematics (n=20).


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_IX | Pages 25 - 25
1 Mar 2012
Pandit H Jenkins C Gill H Beard D Price A Dodd C Murray D
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Introduction

The results of the mobile bearing Oxford unicompartmental knee replacement (UKR) in the lateral compartment have been disappointing with a five year survival of 82%. Therefore, it is recommended that mobile bearings should not be used for lateral UKR. This low survivorship is primarily due to high dislocation rate, all occurring in the first year. A detailed analysis of the causes of bearing dislocation confirmed the elevated lateral tibial joint line to be a contributory factor. A new surgical technique was therefore introduced in which care was taken neither to remove too much bone from distal femur nor to over tighten the knee and thus ensure that the tibial joint line was not elevated. Other modifications to the technique were also introduced including use of a domed tibial component.

Aim

The aim of this study is to compare the outcome of these iterations: the original series [series I], Series II with improved surgical technique and the domed tibial component [Series III].


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_IX | Pages 32 - 32
1 Mar 2012
Kendrick B Simpson D Bottomley N Kaptein B Garling E Gill H Dodd C Murray D Price A
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Purpose of study

To investigate the linear penetration rate of the polyethylene bearing in unicompartmental knee arthroplasty at twenty years.

Introduction

The Phase 1 Oxford medial UKR was introduced in 1978 as a design against wear, with a fully congruous articulation. In 1987 the Phase 2 implant was introduced with new instrumentation and changes to the bearing shape. We have previously shown a linear penetration rate (LPR) of 0.02 mm/year at ten years in Phase 2, but that higher penetration rates can be seen with impingement. The aim of this study was to determine the 20 year in-vivo LPR of the Oxford UKR, using Roentgen Stereophotogrammetric Analysis (RSA).


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_IX | Pages 34 - 34
1 Mar 2012
Ferguson J Pandit H Price A Marks B Gill H Murray D Dodd C
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Introduction

Obesity has been considered a relative contra-indication in unicompartmental knee arthroplasty (UKA) due to fear of high wear rates, loosening and tibial collapse. The aim of this study was to investigate the impact of high body mass index (BMI) on ten-year survivorship and five-year functional outcome after Oxford UKA, a fully congruous mobile bearing design with large contact area and low wear rate.

Methods

This prospective study examines a consecutive series of 595 knees (mean age 66 years, range: 33-88) undergoing Oxford UKA with a minimum 5-year follow-up. Patients were divided into three groups; Group I (Normal body weight), BMI <25 (n=171), Group II (overweight), BMI 25- 30 (n=264), and Group III (Obese), BMI ≥30 (n=160). The survivorship and functional outcome (as assessed by change in Oxford Knee Score [DeltaOKS]) and Knee Society Score (KSS) for all three groups were compared.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_IX | Pages 31 - 31
1 Mar 2012
Kendrick B Pandit H Jenkins C Beard D Gill H Price A Dodd C Murray D
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Purpose of Study

To assess the incidence of radiolucency in cemented and cementless Oxford unicompartmental knee replacement at two years.

Introduction

Most unicompartmental knee replacements (UKRs) employ cement for fixation of the prosthetic components. The information in the literature about the relative merits of cemented and cementless UKR is contradictory, with some favouring cementless fixation and others favouring cemented fixation. In addition, there is concern about the radiolucency that frequently develops beneath the tibial component with cemented fixation. The exact cause of the occurrence of radiolucency is unknown but it has been hypothesised that it may suggest suboptimal fixation.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_IX | Pages 27 - 27
1 Mar 2012
Pandit H Jenkins C Weston-Simons S Ferguson J Popat BM Gibbons M Price A Gill H Dodd C Murray D
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Introduction

Kozinn and Scott have made recommendations about contra-indications for unicompartmental knee replacement (UKR). They suggest that patients younger than 60, weight > 82 kilograms, patients with exposed bone in patella-femoral compartment or patients who are physically active/perform heavy labour should not be offered a UKR. In addition, chondrocalcinosis is a contra-indication. These strict selection criteria are based on the experience with fixed bearing UKAs and are more intuitive than evidence based. The Oxford UKR has a fully congruous mobile bearing and has been shown to have minimal wear. Over the past 25 years, the Oxford Group has followed a standardised protocol for patient selection for UKR. We ignore patella-femoral joint pathology, chondrocalcinosis, patient's age, weight and activity level when deciding the suitability for UKR.

Methods

Using the standardised indications, more than 1100 Oxford UKRs have been performed to date over the last 10 years. These patients are assessed pre-operatively and at regular intervals post-operatively in a dedicated research clinic. We present the results of these consecutive cases. Patients were classified into two groups: group I (satisfy Kozinn-Scott recommendations) and group II (outside recommendations).


The Journal of Bone & Joint Surgery British Volume
Vol. 87-B, Issue 11 | Pages 1493 - 1497
1 Nov 2005
Price AJ Short A Kellett C Beard D Gill H Pandit H Dodd CAF Murray DW

Polyethylene particulate wear debris continues to be implicated in the aetiology of aseptic loosening following knee arthroplasty. The Oxford unicompartmental knee arthroplasty employs a spherical femoral component and a fully congruous meniscal bearing to increase contact area and theoretically reduce the potential for polyethylene wear. This study measures the in vivo ten-year linear wear of the device, using a roentgenstereophotogrammetric technique.

In this in vivo study, seven medial Oxford unicompartmental prostheses, which had been implanted ten years previously were studied. Stereo pairs of radiographs were acquired for each patient and the films were analysed using a roentgen stereophotogrammetric analysis calibration and a computer-aided design model silhouette-fitting technique. Penetration of the femoral component into the original volume of the bearing was our estimate of linear wear. In addition, eight control patients were examined less than three weeks post-insertion of an Oxford prosthesis, where no wear would be expected. The control group showed no measured wear and suggested a system accuracy of 0.1 mm. At ten years, the mean linear wear rate was 0.02 mm/year.

The results from this in vivo study confirm that the device has low ten-year linear wear in clinical practice. This may offer the device a survival advantage in the long term.