An early comparison of clinical and mechanical aspects of hybrid and uncemented hip resurfacing

Hip resurfacing is a popular operation for hip joint arthritis. It has been performed using hybrid and uncemented components. We aim to compare the two techniques functionally and mechanically over a 2 year post-operative period. We studied anteroposterior (AP) radiographs from 30 patients who had undergone hybrid hip resurfacing and 30 patients who had undergone uncemented hip resurfacing using the transgluteal approach to the hip. We measured the acetabular offset, femoral offset, stem/shaft angle, medialization of the cup, head/neck ratio, cup height, leg length and the implant seating pre-operatively, immediately post-operatively, 1 and 2 years post-operatively. Harris Hip Scores were performed pre-operatively and at 1 year post-operatively. There was no significant loss of offset and no femoral neck thinning at 2 years post-operatively with no loss of leg length. We note a smaller femoral offset and a reduction on average of 2.87 mm in seating of the femoral cap in the uncemented group when compared to the hybrid group at the 1 year postoperative review. Thus, we attribute to movement of the femoral component in the first year postoperatively, and as such restoration of the femoral offset to the pre-operative level. Both groups showed an equal significant improvement in the Harris Hip Scores at the 1 year postoperative period when compared to the pre-operative score. We conclude that uncemented hip resurfacing is statistically as good as the hybrid hip resurfacing, with a stable uncemented femoral component relying on biological cancellous fixation rather than cement fixation. We also note that in both groups, no evidence of neck thinning was noted at the 2 year postoperative period.