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

<bold>Background: </bold>There 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.<bold>Methods: </bold>One 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.<bold>Results: </bold>Average 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).<bold>Conclusion: </bold>We demonstrated no observable difference in hip stability or acetabular abduction. This study provides realistic outcomes for surgeons implementing DAA THA into their practice. [ABSTRACT FROM AUTHOR]