Three-dimensional planning and virtual radiographs in revision total hip arthroplasty for instability.

Instability is one of the most challenging complications of total hip arthroplasty. The cause of instability is not always clear and treatment outcome is not always satisfactory. Treatment can be optimized by accurate identification of the cause of instability and precise surgical technique. In this case report, we illustrate the use of a three-dimensional (3-D) preoperative planner and virtual radiographic system to improve component position in revision total hip arthroplasty required because of recurrent dislocation. Using this technique, we identified common problems seen in patients with unstable hips after previous revision surgery including impingement, cup malpositioning, bone deficiency in the medial wall, and integrity of fixation screws. The computer-assisted system allowed preoperative planning with range of motion simulation and optimization of the acetabular cup position. The virtual radiographic system provided 3-D measurement of the cup position using a postoperative plane radiograph.