Accuracy in hip surgery: assessment, consequence and solution

Abstract

Hip arthroplasty is the most common and successful surgical treatment for the management of hip osteoarthrosis. However, complications arising from technical error in analysing the native hip, aswell as the position of the hip prosthesis can result in a suboptimal outcome for the patient. This thesis principally examines acetabular component orientation, investigating the use of technology in this critical aspect of hip arthroplasty surgery. In the first study, navigation technology is used to assess the performance of a current cohort of training and senior orthopaedic surgeons in a simulated surgical setting. A wide range of error in orientating an acetabular cup orientation to a target position is demonstrated. The second study seeks to establish a novel method of delineating the femoral neck axis in 3D using a sample of normal hip CT scans. Using such a proximal femoral frame of reference allows a standardised approach to assessing normal and abnormal hip morphology. The articular margin of the femoral head is shown to have a wave like pattern that consists of an anterior and posterior facet. The third study compares 2D and 3D measurements of inclination and version of acetabular components, finding a critical difference between the two in version measurements and that 3D measurements are more reliable. The thesis continues by examining the current methodology of analysing the concentration of cobalt and chromium metal ions in the joint fluid from a cohort of symptomatic patients with a metal on metal hip arthroplasty. A more robust laboratory method of processing fluid samples using a digestive oxidative method is presented. The relationship between concentrations of metal ion levels in joint fluid and several clinical parameters is investigated with no clear association shown, suggesting joint fluid in itself cannot be used as a marker for a failing metal on metal hip. The thesis concludes by comparing navigation technology to conventional ‘freehand’ method in orientating an acetabular component in a group of patients undergoing metal on metal hip resurfacing. The results suggest that navigation technology may substantially improve surgeon error in this task. Technology and three dimensional imaging can play a vital role in improving the accuracy of orientating an acetabular component in hip surgery. It can be employed in the pre-operative stages to assess trainee performance, intra-operatively to reduce surgical error and post operatively to investigate surgeon accuracy on CT imaging.