Periprosthetic bone mineral density changes with femoral components of differing design philosophy

We measured the bone mineral density in 22 patients with the cylindrical stemmed cobalt-chrome AML prosthesis (collared) and in 22 patients with the tapered stem titanium CLS prosthesis (collarless). DEXA scanning was undertaken at a mean of 40 months in the AML and 52 months in the CLS group from the time of implant insertion. In both groups the greatest mean loss of BMD was found in Gruen zone 7 and the least change in Gruen zone 5. In all zones the BMD loss was greater in the AML group but only statistically significant in zones 6 (P<0.05) and 7 (P<0.01). Although numerous factors affect BMD changes around cementless implants, this study suggests that less bone loss can be associated with the titanium CLS stem.