Comparative study of human cancellous bone remodeling to titanium and hydroxyapatite-coated implants.

The human cancellous bone response was compared in weight-bearing porous hydroxyapatite (HA) and titanium-coated implants placed in the distal medial femoral condyles of consenting staged bilateral knee patients. The Institutional Review Board approved study quantified the amount of bone ingrowth, the mineral apposition rate, and the bone mineral content. Results showed that the osteoconductive HA coating increased the amount of bone ingrowth by 8% (P = .018). The HA coating did not effect the mineral apposition rate of the bone but had an 8% lower bone mineral content at the implant interface (P = .042). The influence of HA coatings on human cancellous bone appears highly focal along the coating surface. Gaps of 50-500 microns filled with fibrous connective tissue were observed along the porous-coated surfaces of both implant types suggesting that HA coatings still require precision placement adjacent to human cancellous bone.