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

We measured the bone mineral density in 22 patients with the cylindrical st emmed cobalt-chrome AML prosthesis (collared) and in 22 patients with the t apered stem titanium CLS prosthesis (collarless). DEXA scanning was underta ken at a mean of 40 months in the AML and 52 months in the CLS group from t he 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 zone s the BMD loss was greater in the AML group but, only statistically signifi cant in zones 6 (P<0.05) and 7 (P<0.01). Although numerous factors affect B MD changes around cementless implants, this study suggests that less bone l oss can be associated with the titanium CLS stem.