Changes in bone mineral density adjacent to two biomechanically different types of cementless femoral stems in total hip arthroplasty.

We have compared the differences in bone mineral density (BMD) adjacent to two biomechanically different cementless femoral stems used for total hip arthroplasty. Measurements were performed 12 to 38 months after surgery in a cross sectional study of 29 patients. Of these, 15 had arthroplasties using an "off the shelf" type cementless femoral stem (Spotorno), while 14 had a custom made cementless stem (Evolution-K). Dual X-ray absorptiometry (DXA) measurements revealed that the patients who had a Spotorno stem had a significantly lower BMD in the operated leg compared to the non-operated side in both Gruen zones 1 and 7, whereas no significant differences were found in these areas in the Evolution-K group. For both types of prosthesis there was a significant and similar decrease in BMD of the proximal tibia on the operated side.