ATROPHY OF THE PROXIMAL PART OF THE FEMUR AFTER TOTAL HIP-ARTHROPLASTY WITHOUT CEMENT - A QUANTITATIVE COMPARISON OF COBALT-CHROMIUM AND TITANIUM FEMORAL STEMS WITH USE OF DUAL X-RAY ABSORPTIOMETRY

The purpose of this study was to compare the density of periprosthetic bone about titanium and cobalt-chromium stems that had been inserted without cement. The analysis was done, three to four years after a total hip arthroplasty, in a retrospectively matched cohort of thirty patients. Fifteen patients had a stem that was collarless, proximally coated, and made of titanium; the other fifteen had a stem of similar design that was made of cobalt-chromium. The criteria for selection in the study included an excellent clinical and radiographic result and separately calculated modified Harris and Mayo hip scores of more than 94 points. All stems had radiographic evidence of osseous ingrowth. A comparison of the bone-mineral density about the two different types of stem with dual-energy x-ray absorptiometry revealed a significant difference only along the calcar of the femur. There was no significant difference about the remaining, preponderant portion of the proximal part of the femur. Our data suggest that the difference in the modulus of elasticity between the two types of stem had little effect on the loss of bone-mineral density in most of the proximal part of the femur after arthroplasty without cement.