Direct anterior approach associated with lower dislocation risk after primary total hip arthroplasty in patients with prior lumbar spine fusion

Background: While there has been much interest in the increased dislocation rate in total hip arthroplasty (THA) patients with a lumbar spine fusion (LSF), there is minimal literature comparing the risk based on surgical approach. The purpose of this study was to determine if a direct anterior (DA) approach was protective against dislocation when compared to the anterolateral and posterior approaches in this high-risk patient population. Methods: A retrospective review was performed of 6554 THAs performed at our institution from January 2011 to May 2021. 294 (4.5%) patients had a prior LSF and were included in the analysis. The surgical approach, timing of LSF in relation to THA, vertebral levels fused, timing of THA dislocation, and the need for revision surgery were recorded for statistical analysis. Results: In total, 39.7.3% of patients underwent a DA approach (n = 117), 25.9% underwent an anterolateral approach ( n = 76), and 34.3% underwent a posterior approach ( n = 101). There was no difference in number of vertebral levels fused between groups (mean 2.5, all p > 0.05). There was a total of 13 (4.4%) THA dislocation events, with an average time from surgery to dislocation of 5.6 months (0.3–30.5 months). There were fewer dislocations in the DA cohort (0.9%) in comparison to both the anterolateral (6.6%, p = 0.036) and posterior groups (6.9%, p = 0.026). Conclusions: The DA approach demonstrated a significantly lower THA dislocation rate compared to both the anterolateral and posterior approaches in patients with a concomitant LSF.