BACKGROUND AND PURPOSE: Large-size hip articulations may improve range of motion (ROM) and function compared to a 28-mm THA, and the low risk of dislocation allows the patients more activity postoperatively. On the other hand, the greater extent of surgery for resurfacing hip arthroplasty (RHA) could impair rehabilitation. We investigated the effect of head size and surgical procedure on postoperative rehabilitation in a randomized clinical trial (RCT). Methods We followed randomized groups of RHAs, large-head THAs and standard THAs at 2 months, 6 months, 1 and 2 years postoperatively, recording clinical rehabilitation parameters.

RESULTS: Large articulations increased the mean total range of motion by 13° during the first 6 postoperative months. The increase was not statistically significant and was transient. The 2-year total ROM (SD) for RHA, standard THA, and large-head THA was 221° (35), 232° (36), and 225° (30) respectively, but the differences were not statistically significant. The 3 groups were similar regarding Harris hip score, UCLA activity score, step rate, and sick leave.

INTERPRETATION: Head size had no influence on range of motion. The lack of restriction allowed for large articulations did not improve the clinical and patient-perceived outcomes. The more extensive surgical procedure of RHA did not impair the rehabilitation. This project is registered at ClinicalTrials.gov under # NCT01113762.