Total Hip Arthroplasty (THA) is a common surgical procedure to treat arthritis of the hip joint whereby diseased bony anatomy is surgically excised and replaced via implantation of hip prostheses in both the femoral and acetabular bone. The femoral canal fit is an important variable influencing survivorship of cementless THA and should be evaluated for new prosthesis. The Accolade II femoral stem is a newly designed stem incorporating a population-based design using a unique modelling and analytics system called SOMA to morphologically design this femoral component from 500 high resolution CT scans. Extrapolation of these findings in a large multi-centre clinical evaluation using radiographs has not been fully explored. This study aims to evaluate the radiographic fit of the Accolade II and Corail femoral stem in the femoral canal. The Corail stem is the most commonly used cementless femoral stem in Australia and forms the benchmark in this project due to strong survivorship in this category. This radiographic analysis forms a component of the larger prospective, multi-centre, randomised clinical study comparing these two cementless prosthesis. Objective To determine the femoral canal fit of Accolade II femoral stem compared to the Corail femoral stem, looking at metaphyseal, diaphyseal or combined engagement of the stem during the first two years postoperatively. Data collection Hip and pelvis radiographs taken pre-operatively, 6-weeks, 6-months, 1-year and 2-year follow-up have been collected and de-identified as per the multi-centre protocol. Sample size The project aims to examine the following number of x-rays: 77 from Dandenong Hospital, 28 (potentially 63) from Freemantle Hospital, 12 (potentially 19) from Rockhampton Hospital, 36 (potentially 86) from Burwood Hospital Christchurch, and 9 from The Mater in Townsville. Methodology Radiographic evaluation will be conducted on all patients with x-rays available at both 6-week and 2-year follow-up. The will allow for a continuous assessment of early and short-term follow-up. The radiographic fit at 2-years represents a plateau in recovery where the position of the cementless THA and a timepoint indicative of good survivorship. The early measurement at 6-weeks will supplement the 2-year assessment and be used to assess changes during the bedding in period. Three locations will be used to assess the fit of the femoral stem in the distal and proximal sections with a measurement of the maximum and minimum distance of: Gap in the proximal region between the stem and cortical bone on the medial side at a section 10mm above the lesser trochanter. Gap in the distal region between the stem and cortical bone on the lateral side at a distance of 60mm from the lesser trochanter. Gap in the distal region between the stem and cortical bone on the medial side at a distance of 60mm from the lesser trochanter. The fill of the stem is assessed as the ratio of the width of the stem over the width of the femoral canal. This is assessed at more definitive locations by using the anatomic axis of the femur as a guide. The locations are: Proximal (10mm above the lesser trochanter) Middle (60mm below the lesser trochanter) Distal (25mm above the distal tip of the stem) Data will be recorded on an Excel spreadsheet and each image will be measured on two separate occasions to assess intra-observer variability. The observer will be blinded to the results of their previous measurement during each evaluation to reduce bias. Double blinding in this study is not possible as the profile of each stem is unique when viewed on a radiograph. However, the reviewer will be blinded to the surgeon and site details, with all x-rays numbered in a unique order. Descriptive statistics will be used to describe the radiographic fit of each femoral stem, with the mean and standard deviation at 6-weeks and at 2-years tabulated. A repeat measures ANOVA will be used to compare both femoral stems at each time point, accounting for follow-up as an independent variable. Kappa statistics will be used to calculate the Pearson correlation for a measure of intra-observer variability. A P value of less than 0.05 is regarded as significant.
Orthopaedics, total hip arthroplasty, radiological fit, Accolade II, Corail, randomised clinical trial
School of Clinical Sciences at Monash Health / Hudson Institute of Medical Research » Surgery - Monash Medical Centre