A Vertical Measurement System to Predict the Change in Leg Length in Total Hip Arthroplasty.

The management of leg lengths in total hip arthroplasty continues to challenge orthopaedic surgeons. The aim of this study is to test the reliability of a measuring device used to measure the resected femoral head and how the resulting intra operatively calculated change in leg length compares to the radiographically measured change in leg length. Four orthopaedic surgeons measured 20 femoral heads and the intra class coefficients of the raters were between 0.955 and 0.990 with a mean difference less 1 mm, indicating the reliability of the device. The 'actual' radiographic leg length correction of 50 patients and the 'predicted' intra operatively calculated correction was analysed with a linear regression model and 47 measurements were within 2 mm and the remaining 3 within 4 mm.