Instability in Patients With Lumbar Spine Disease Undergoing Posterior Approach and Lateral Approach Primary Total Hip Arthroplasty.

INTRODUCTION:Dislocation rates in patients who have fixed spinopelvic motion have been reported up to 20%. Few studies have directly compared dislocation rates in patients who have spine pathology undergoing total hip arthroplasty (THA) through different surgical approaches. This study compared postoperative dislocation rates in patients who had lumbar spine disease and underwent primary THA using a posterior or direct lateral approach. METHODS:Between 2011 and 2017, consecutive cohorts of primary THAs were retrospectively reviewed. One surgeon routinely used a posterior approach, while the other used a direct lateral approach. Chart and radiographic review were conducted to identify patients who had lumbar spine disease. Dislocations among cohorts with and without lumbar spine disease were compared by posterior and direct lateral approaches. RESULTS:The overall dislocation rate was 1.3% (15/1,198). The top four predictors of dislocation were presence of lumbar spine disease (odds ratio [OR] 5.0; P = 0.014), posterior surgical approach (OR, 6.5; P = 0.074), cases performed for fracture (OR, 4.4; P = 0.035), and women (OR, 4.6; P = 0.050). Dislocation rates among direct lateral approach patients who had lumbar spine pathology were significantly lower than posterior approach patients who had lumbar spine pathology (0.0% versus 3.6%; P = 0.011). DISCUSSION:Although dislocation rates were low in both groups, study results suggest that a direct lateral approach for primary THA may reduce postoperative dislocations for patients who have limited spinopelvic motion due to lumbar spine pathology. Furthermore, surgeons using the posterior approach might consider optimizing the femoral head to acetabular cup ratio in patients who have lumbar spine disease.