Abstract
The Birmingham mid-head hip resurfacing arthroplasty (Smith & Nephew, Tennessee) (BMHR) is designed for use in patients with avascular necrosis of the femoral head. The BMHR has limited short-mid term follow-up results. We report the experience of 27 consecutive BMHR procedures with a minimum two year follow-up.
23 patients (20 males and 3 females) with an average operation age of 49.8 years (SD ±10.9) (22–65) were investigated. The mean follow-up period was 3.0 years (SD ±0.77). The operations were between April 2008 and November 2011 by one surgeon. Data and outcome measurements were collected prospectively and analysed retrospectively. Procedures were reviewed to determine function. We evaluated Harris Hip Scores, Short Form-36 (SF-36v2) Scores, Tegner Activity Score Scores and McMaster Universities Osteoarthritis Index Scores (WOMAC) comparatively at preoperative, six month and yearly intervals. Paired samples t-tests were applied to determine improvements where p<0.05 was deemed as significant.
There were no patient deaths. There were no revisions. Harris Hip scores for pre-operative 6, 12, 24 and 36 month intervals were: 52.30, 84.14, 83.07, 87.50 and 89.50. Average pre-operative 6, 12, 24 and 36 month SF36v2 Total scores were: 116.54, 124.32, 130.44, 135.97 and 133.18. Tegner scores for pre-operative 2.75, 3.29, 3.00, 3.67 and 3.01. WOMAC Total scores for aforementioned intervals for the posterior approach were: 59.51, 84.22, 90.30, 86.86 and 92.25.
The mean Harris Hip scores improved significantly between preoperative and 6, 12, 24 and 36 months (p<0.001). The mean SF-36v2 physical scores improved significantly between preoperative and 6, 12, 24 and 36 months (p<0.016). WOMAC scores improved significantly between preoperative and 6, 12, 24 and 36 months (p<0.017).
The presence of avascular necrosis significantly increases the revision rate for hip resurfacing surgery. The BMHR prosthesis, in this short term follow-up, appears to avoid the main cause of failure, femoral component loosening. Longer term efficacy remains to be seen. We plan to continue close supervision of these patients.
