Leg length discrepancy in computer navigated total hip arthroplasty - how accurate are we?

The success of total hip arthroplasty (THA) depends on the restoration of 2 important parameters - hip offset and leg length. Leg length discrepancy (LLD) after THA is associated with back pain, gait disorder, general patient dissatisfaction and aseptic loosening. Hence it is of utmost importance to minimise LLD.

This is a retrospective study where we compared the reproduction of leg lengths between navigated THA group (152 patients) and nonnavigated THA group (57 patients). The leg lengths were measured radiologically using Ranawat technique on AP pelvic radiograph.

In the navigated group, the leg lengths of the reconstructed hips were restored to within 6 mm of the opposite leg in 146 patients (96.05%) while 6 patients (3.94%) had LLD of more than 6 mm. In the nonnavigated group, 29 patients (51%) had their leg lengths restored within 6 mm of the opposite leg while the remaining 28 patients (49%) had their LLD greater than 6 mm. Statistical analysis of the 2 pairs of LLD measurements (navigated hip and nonnavigated group) using Mann-Whitney U-test revealed significant difference between these two groups (p<0.001).

Based on our results we conclude that computer navigation is an excellent tool to facilitate the successful reproduction of leg length in THA.