The impingement-dislocation risk of total hip replacement: effects of cup orientation and patient maneuvers.

Hip dislocation is one of the most frequent complications after total hip arthroplasty. Impingement and dislocation might be caused due to misalignment of the acetabular cup during surgery, or performing dislocation-prone activities afterwards. A finite element model was developed to predict the impingement and dislocation behavior of the prosthetic joint, for different combinations of cup orientation and patient maneuver. Four dislocation-prone activities of daily life and 25 cup orientations were analyzed to determine how close they are to the impingement and subsequent dislocation events. The angular margin results obtained indicated that the sit-to-stand and standing while bending at the waist are prone to dislocation, in particular when the cup anteversion angle is small.