Acetabular Abduction and Dislocations in Direct Anterior vs Posterior Total Hip Arthroplasty: A Retrospective, Matched Cohort Study

Abstract

BackgroundThere is purported improvement in component positioning and hip stability with the use of direct anterior approach (DAA) total hip arthroplasty (THA). We sought to determine if there is a difference in acetabular component position or dislocation frequency between DAA and posterior THA. MethodsOne arthroplasty fellowship-trained surgeon introduced DAA THA into his practice. From the initiation of DAA in 4/2012-8/2015, this comparative series resulted in 66 DAA THAs. A matched cohort (age, gender, body mass index [BMI], and comorbidities) was then created for posterior THA, 66 hips. DAA THA used fluoroscopy with anterior capsular excision; posterior group used no image guidance and had capsular repair. Posterior group BMI was 27.8 and DAA group BMI was 27.6 (P = .36). Minimum 3-month follow-up occurred in both groups. ResultsAverage acetabular abduction angle in the posterior group was 41.9° (range, 32°-60°; standard deviation [sdev], 6.24) and DAA group 43.8° (range, 30°-62°; sdev 6.9), P = .12. The percentage of outliers (outside Lewinnek safe zone, 30°-50°) was 9.1% (6 of 66) in posterior group and 13.6% (9 of 66) in DAA group. There were 2 anterior dislocations in the DAA THA group and 1 anterior dislocation in the posterior THA group, resulting in P = .56. The DAA dislocation frequency in this group was overall higher at 3.0% (2 of 66) compared with the matched posterior (1.5%, 1 of 66) and unmatched posterior larger series (.8%, 3 of 360). ConclusionWe demonstrated no observable difference in hip stability or acetabular abduction. This study provides realistic outcomes for surgeons implementing DAA THA into their practice.