Host—bone response to porous-coated cobalt—chrome and hydroxyapatite-coated titanium femoral components in hip arthroplasty

Uncemented porous-coated cobalt-chrome femoral stems have produced satisfactory short-term clinical results, although slightly inferior to the results of cemented total hip arthroplasty. Proximal femoral bone resorption, osteolysis and fibrous ingrowth have been reported with porous-coated stems. Hydroxyapatite-coated stems and titanium stems have been introduced to avoid these findings through improved fixation. Dual-energy x-ray absorptiometry allows quantitative examination of bone density changes after uncemented total hip arthroplasty. This study examines the host-bone response to hydroxyapatite-coated titanium and porous-coated cobalt-chrome stems of identical geometry in three paired bilateral cases at 5 to 7 years. Distinctly different patterns of femoral bone mineral density changes were observed with the two stem designs. The authors conclude that dual-energy x-ray absorptiometry is a promising technique allowing noninvasive analysis of uncemented stem fixation, and that the data from this study suggest improved fixation and stress transfer with hydroxyapatite-coated titanium stems.