Introduction: There have been many techniques described to measure limb length discrepancy and methods to correct this during total hip arthroplasty; preoperative and intraoperative. These techniques have been either inconsistent, cumbersome or not readily available due to expense. There is a lack of evidence to support one particular approach. The aim of this study is to assess the accuracy of the relationship between the centre of the femoral head and tip of the greater trochanter.
Methods: A prospective observational cross-sectional study, with patients undergoing Positron emission tomography-CT (PET-CT) scan between 20th January 2016 to 31st December 2016. Exclusion criteria were patients undergoing PET-CT scan for musculoskeletal condition, those found to have existing pathology of the hip (including previous trauma) and those aged younger than 18 years and over 50 years.
Results: There was a total of 116 participants, giving 232 hips for assessment and 184 hips were measured by two observers. The mean age of the sample was 40.51 years. The mean distance of the centre of the femoral head from the tip of the greater trochanter was 8.53 mm distal (with a standard deviation of 4.97). Analysis of the right and left hip measurements gave a Pearson correlation coefficient of 0.87, suggesting a good correlation. Interobserver analysis demonstrated fair agreement with intraclass correlation coefficient of 0.52.
Conclusion: The evidence of this study and that in literature suggests that this landmark is unreliable and should no longer be used.
Keywords: Arthroplasty; Femur; Hip; Leg length; Trochanter.