Capsular Repair Counteracts the Risk of Dislocation in Hemiarthroplasty Conversion to Total Hip Arthroplasty

This study investigated whether decreasing the femoral head size, in addition to performing a posterior capsular closure and short external rotator repair, influences the historical rate of dislocation after conversion of a failed hemiarthroplasty (HA) to a total hip arthroplasty (THA) through a posterior approach. We reviewed 15 patients from our prospective arthroplasty database who underwent a conversion from an HA to a THA with closure of the posterior capsule, had downsizing of the femoral head, and had at least a 2-year follow-up. Patients were clinically observed to determine whether their hip dislocated postoperatively or required re-revision. Radiographs were evaluated to assess for known risk factors for dislocation, including component position and restoration of hip biomechanics. The femoral head size was downsized from a mean of 45 mm (range, 42-57 mm) preoperatively to a mean of 32 mm (range, 28-36 mm) postoperatively (P<.001). Femoral heads sized 36, 32, and 28 mm were used in the revision of 4, 5, and 6 hips, respectively. At the mean 84-month follow-up (range, 24-156 months), there were no dislocations. Attention to surgical technique and closing the posterior capsule can decrease the historically high dislocation rate associated with converting an HA to a total hip replacement using the posterolateral approach. Despite substantial reduction in size of the prosthetic femoral head, there were no postoperative dislocations with closure of the posterior capsule. Downsizing the femoral head during revision THA should be avoided; however, if not feasible, closure of the posterior capsule can offset the otherwise increased risk of dislocation.