Abstract
Introduction Modern metal-on-metal hip resurfacing (RHA) was introduced as a bone-preserving method of joint reconstruction for young and active patients; however, the large diameter of the bearing surfaces is of concern for potentially increased metal ion release.
Patients and methods 71 patients (< 65 yrs) were randomly assigned to receive either a RHA (n=38) or a conventional metal-on-metal (MoM) THA (n=33). Functional outcomes were assessed preoperatively, at 6, 12 and 24 months. Cobalt and chromium blood levels were analyzed preoperatively, at 3, 6, 12 and 24 months.
Results All functional outcome scores improved highly significant for both groups. At 12 and 24 months the UCLA Activity score was significantly higher for the RHA patients, the OHS only at 24 months. However, in spite of randomization UCLA scores also appeared to be higher in RHA patients at baseline. RHA patients were more satisfied at 12 months. Cobalt concentrations were significantly higher for RHA only at 3 and 6 months. Chromium levels remained significantly higher for RHA until 24 months. No pseudotumors were encountered in either group so far. One RHA was revised for early aseptic loosening and in two THA's a cup insert was exchanged for recurrent dislocation.
Conclusion RHA patients scored significantly higher on UCLA, OHS and satisfaction at some intervals, however, as for the UCLA preoperative levels were already in favor of RHA. Chromium blood levels were significantly higher for RHA, whereas for cobalt this was only observed up to 6 months. The true value of RHA against THA will be determined by longer follow-up and a possible shift of balance between their respective (dis)advantages.
