Dislocation is one of the most common complications after revision THA using the posterolateral approach. Although the cause of dislocation after revision THA is multifactorial, the historically high dislocation rates have been shown to be significantly reduced by closing the posterior capsule and by the use of large diameter (36 and 40 mm) femoral heads. The relative importance of each of these strategies on the rate of dislocation remains unknown. We undertook a study to determine if increasing femoral head diameter, in addition to posterior capsule closure would influence the dislocation rate following revision THA.

We retrospectively reviewed 144 patients who underwent a revision THA. We included all patients who underwent revision THA with closure of the posterior capsule and who had at least a 2-year minimum follow-up. We excluded patients undergoing a revision THA for dislocation or multistage revision for infection since these patients would likely have deficient posterior tissues. Forty-eight patients had a 28 mm femoral head, 47 had a 32 mm head and 49 patients had a 36 mm femoral head.

At a minimum follow-up of 2 years, there were 3 dislocations. There were no dislocations in the 28 mm group (0%), 2 in the 32 mm group (4%) and 1 in the 36 mm group (2%). All patients were successfully treated with a closed reduction. No patients had recurrent dislocation. Head size alone was not found to significantly decrease the risk of dislocation (28mm vs 32mm p=0.12; 28mm vs 36mm p=0.27; 32mm vs 36mm p=0.40).

Both large diameter heads and careful attention to surgical technique with posterior capsule closure can decrease the historically high dislocation rate after revision THA when utilizing the posterolateral approach. The additional use of a large diameter head did not have a significant impact on the already low dislocation rate. Capsular closure outweighs the effect of femoral head diameter in preventing dislocation following revision THA through a posterolateral approach.