Prospective Evaluation of the Posterior Tissue Envelope and Anterior Capsule after Anterior Total Hip Arthroplasty

Abstract Aims Femoral exposure for direct anterior approach (DAA) total hip arthroplasty (THA) invariably requires posterior soft tissue releases. Released posterior structures cannot be repaired. The purpose of this study was to describe the frequency and anatomical consequences of DAA THA posterior soft tissue releases and to compare the appearance of the anterior capsule between a group of patients who had capsulotomy and repair versus capsulectomy. Patients and Methods 32 DAA THA patients underwent metal artifact reduction Magnetic Resonance Imaging (MRI) at discharge and 1 year follow-up. Seventeen had underwent capsulotomy and repair and 15 capsulectomy. A radiologist blinded to intraoperative data scored each MRI. Anterior capsular integrity, status of the piriformis and conjoint tendons, and muscle atrophy were graded. Descriptive statistics were performed to analyze results. Results Immediately postoperatively, 75% of piriformis tendons were intact and 38% of conjoined tendons were intact. At 1 year, 97% had an intact piriformis and conjoined tendon, although many were in continuity through scar with the capsule. The posterior capsule directly contacted bone in all patients. At 1 year, none of the patients who underwent capsulotomy with repair had persistent anterior capsule defects, while 27% in the capsulectomy group had persistent defects. Conclusion Posterior capsule and conjoined tendon releases were commonly performed during DAA THA, yet continuity with bone was frequently achieved at one year. In this study capsulotomy with repair resulted in no anterior capsular defects when compared with capsulectomy. These results may support improved THA stability observed after DAA with capsular repair despite posterior soft tissue releases. Level of Evidence Level III, prospective cohort study