The relationship of sporting activity and implant survivorship after hip resurfacing.

BACKGROUND: The effect of sports on the durability of the prosthesis after hip resurfacing has not been studied, to our knowledge. The purpose of this study was to correlate sporting activity levels calculated as Impact and Cycle Scores with the survivorship of the hip resurfacing implants.

METHODS: Four hundred and forty-five patients were surveyed from one to five years after surgery. The mean age of the patients was 48.7 years, and 74% were men. The Impact and Cycle Score included two scores: an Impact Score and a Hip Cycle Score. All patients were also evaluated with the University of California at Los Angeles activity score. Twenty-three patients (twenty-seven hips) underwent revision surgery after they had completed the survey.

RESULTS: The mean duration of follow-up at the time of survey data collection was 1.9 years (range, 1.0 to 4.9 years), and the mean follow-up period was 10.2 years (range, 6.1 to 13.7 years). The mean Impact Score was 28.1 (range, 0 to 128), and the mean Hip Cycle Score was 33 (range, 0 to 144). Positive correlations were found between the University of California Los Angeles activity score and the Impact Score (r = 0.535) or Hip Cycle Score (r = 0.497). After adjustment for femoral component size, body mass index, and femoral defect size, a 10-point increment in Impact Score corresponded to a 37% increase (hazard ratio, 1.37; 95% confidence interval, 1.18 to 1.59) in the risk of revision arthroplasty, while a 10-point increment in the Hip Cycle Score increased the risk of revision by 22% (hazard ratio, 1.22; 95% confidence interval, 1.06 to 1.41).Patients with an Impact Score of < 50 had a risk of revision 3.8 times lower (hazard ratio, 3.8; 95% confidence interval, 1.6 to 8.9) than that of the patients with an Impact Score of ≥ 50, with a survivorship rate at eight years of 96.4% (95% confidence interval, 93.6% to 98.0%) compared with 88.8% (95% confidence interval, 74.7% to 95.3%). We found no association between the University of California at Los Angeles activity score and the survivorship of the implants.

CONCLUSIONS: High levels of sporting activities can be detrimental to the long-term success of hip resurfacing devices, independently from other risk factors. Patients seeking hip resurfacing are usually young and should limit their involvement in sports to levels that the implant construct will be able to tolerate.