Bone & Joint

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Objectives

Pseudotumours (abnormal peri-prosthetic soft-tissue reactions) following metal-on-metal hip resurfacing arthroplasty (MoMHRA) have been associated with elevated metal ion levels, suggesting that excessive wear may occur due to edge-loading of these MoM implants. This study aimed to quantify in vivo edge-loading in MoMHRA patients with and without pseudotumours during functional activities.

Methods

The duration and magnitude of edge-loading in vivo was quantified during functional activities by combining the dynamic hip joint segment contact force calculated from the three-dimensional (3D) motion analysis system with the 3D reconstruction of orientation of the acetabular component and each patient’s specific hip joint centre, based on CT scans.

Trauma

Validity of synthetic bone as a substitute for osteoporotic cadaveric femoral heads in mechanical testing Pages 50 - 55

F. O’Neill F. Condon T. McGloughlin B. Lenehan C. Coffey M. Walsh

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Introduction

The objective of this study was to determine if a synthetic bone substitute would provide results similar to bone from osteoporotic femoral heads during in vitro testing with orthopaedic implants. If the synthetic material could produce results similar to those of the osteoporotic bone, it could reduce or eliminate the need for testing of implants on bone.

Methods

Pushout studies were performed with the dynamic hip screw (DHS) and the DHS Blade in both cadaveric femoral heads and artificial bone substitutes in the form of polyurethane foam blocks of different density. The pushout studies were performed as a means of comparing the force displacement curves produced by each implant within each material.

Hip

Taper junction failure in large-diameter metal-on-metal bearings Pages 56 - 63

D. J. Langton R. Sidaginamale J. K. Lord A. V. F. Nargol T. J. Joyce

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Objectives

An ongoing prospective study to investigate failing metal-on-metal hip prostheses was commenced at our centre in 2008. We report on the results of the analysis of the first consecutive 126 failed mated total hip prostheses from a single manufacturer.

Methods

Analysis was carried out using highly accurate coordinate measuring to calculate volumetric and linear rates of the articular bearing surfaces and also the surfaces of the taper junctions. The relationship between taper wear rates and a number of variables, including bearing diameter and orientation of the acetabular component, was investigated.

Knee

The role of the posterior cruciate ligament in total knee replacement Pages 64 - 70

M. A. Ritter K. E. Davis J. B. Meding A. Farris

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Objectives

The purpose of this study was to examine the effect of posterior cruciate ligament (PCL) retention, PCL recession, and PCL excision during cruciate-retaining total knee replacement.

Methods

A total of 3018 anatomic graduated component total knee replacements were examined; 1846 of these retained the PCL, 455 PCLs were partially recessed, and in 717 the PCL was completely excised from the back of the tibia.