HOST-BONE RESPONSE TO POROUS-COATED COBALT-CHROME AND HYDROXYAPATITE-COATED TITANIUM FEMORAL COMPONENTS IN HIP-ARTHROPLASTY - DUAL-ENERGY X-RAY ABSORPTIOMETRY ANALYSIS OF PAIRED BILATERAL CASES AT 5 TO 7 YEARS

Uncemented porous-coated cobalt-chrome femoral stems have produced sat isfactory short-term clinical results, although slightly inferior to t he results of cemented total hip arthroplasty. Proximal femoral bone r esorption, osteolysis, and fibrous ingrowth have been reported with po rous-coated stems. Hydroxyapatite-coated stems and titanium stems have been introduced to avoid these findings through improved fixation. Du al-energy x-ray absorptiometry allows quantitative examination of bone density changes after uncemented total hip arthroplasty. This study e xamines the host-bone response to hydroxyapatite-coated titanium and p orous-coated cobalt-chrome stems of identical geometry in three paired bilateral cases at 5 to 7 years. Distinctly different patterns of fem oral bone mineral density changes were observed with the two stem desi gns. The authors conclude that dual-energy x-ray absorptiometry is a p romising technique allowing noninvasive analysis of uncemented stem fi xation, and that the data from this study suggest improved fixation an d stress transfer with hydroxyapatite-coated titanium stems.