Leg and Femoral Neck Length Evaluation Using an Anterior Capsule Preservation Technique in Primary Direct Anterior Approach Total Hip Arthroplasty

Background Achieving correct leg and femoral neck lengths remains a challenge during total hip arthroplasty (THA).  Several methods for intraoperative evaluation and restoration of leg length have been proposed, and each has inaccuracies and shortcomings.  Both the supine positioning of a patient on the operating table during the direct anterior approach (DAA) THA and the preservation of the anterior capsule tissue  are simple, readily available, and cost-effective strategies that can lend themselves well as potential solutions to this problem. Technique The joint replacement is performed through a longitudinal incision (capsulotomy) of the anterior hip joint capsule, and release of the capsular insertion from the femoral intertrochanteric line. As trial components of the prosthesis are placed, the position of the released distal capsule in relationship to its original insertion line is an excellent guide to leg length gained, lost, or left unchanged. Methods The radiographs of 80 consecutive primary THAs were reviewed which utilized anterior capsule preservation and direct capsular measurement as a means of assessing change in leg/femoral neck length. Preoperatively, the operative legs were 2.81 +/- 8.5 mm (SD) shorter than the nonoperative leg (range: 17.7 mm longer to 34.1 mm shorter).  Postoperatively, the operative legs were 1.05 +/- 5.64 mm (SD) longer than the nonoperative leg (range: 14.9 mm longer to 13.7 mm shorter). Conclusion The preservation and re-assessment of the native anterior hip capsule in relationship to its point of release on the femur is a simple and effective means of determining leg/femoral neck length during DAA THA.