Independent restoration of femoral and acetabular height reduces limb length discrepancy and improves reported outcome following total hip arthroplasty.

Background: Restoration of native hip biomechanics is viewed as a key intra-operative goal in total hip arthroplasty (THA). The transverse acetabular ligament (TAL) can aid in the restoration of acetabular height and offset, and a calliper can be utilised to restore femoral height and offset. This study aimed to determine how these techniques affected the incidence of patient perception of limb length discrepancy (LLD), and if restoration of native biomechanics correlated with improved patient outcomes.

Methods: 123 patients were questioned regarding perception of LLD at 6 weeks and 1 year following THA. Oxford hip score (OHS) and pain scores were recorded. Radiographs were analysed by a blinded clinician who measured three variables; Global hip height (surrogate for limb length), global offset and the combination of both. These measurements were then compared to the unaffected contralateral hip. Data were analysed based on hips that were restored to within ≤±10 mm of native values, and those >±10 mm. Spearman's rank test was used to assess correlation with outcome.

Results: 8 (6.5%) patients perceived a LLD at 6 weeks, reducing to 3 (2.4%) at 1 year-lower than generally reported. Those patients not restored within ±10 mm of native global height had increased pain at 1 year (r = 0.558, p = 0.047). Those not restored within ±10 mm native global offset had a poorer OHS at 1 year (r = -0.586, p = 0.035) and those patients with combined height and offset discrepancy >±10 mm had both a worse OHS (r = -0.581, p = 0.037) and increased pain (r = 0.783, p = 0.002).

Conclusion: Patient perception of LLD is complex and relates poorly to radiographic measurement, however, patients not restored to within 10 mm of native hip height and offset have demonstrated poorer outcomes.