The long-term clinical relevance of calcar atrophy caused by stress shielding in total hip arthroplasty: a 10-year, prospective, randomized study.

Eighty osteoarthritic female patients were randomly allocated to 4 equal groups; the Zwey-Muller, the Corail, the Optifix, or Autophor 900S cementless total hip arthroplasties (THAs) were implanted; and bone density changes, at different sites, were prospectively studied. In zone 7, the greatest reduction of bone density values was observed at 2 years (group A: 24%, group B: 8%, group C: 14.8%, and group D: 18.5%). In all groups, a similar pattern of slow but progressive recovery of bone mineral density changes after the third year was observed, approaching baseline values at 10 years, during which all patients showed satisfactory clinical results. We suggest that the clinical and theoretical relevance of the stress-shielding phenomenon in THA has been overestimated in the literature.