BONE INGROWTH ANALYSIS AND INTERFACE EVALUATION OF HYDROXYAPATITE-COATED VERSUS UNCOATED TITANIUM POROUS BONE IMPLANTS

Fourteen titanium porous-coated implants with a cylindrical shape (length 22 mm and diameter 5 +/- 0.3 mm) were prepared. Bead size was 250-350 mu m. Seven implants were plasma-sprayed with hydroxyapatite and the other seven remained uncoated. Implants, both hydroxyapatite-coated and uncoated, were randomly selected and press fitted longitudinally into the proximal femoral cancellous bone bilaterally in seven dogs. After 12 weeks the dogs were euthanized and push-out and histomorphometric backscattered electron microscopy studies were carried out. No statistical differences in the mechanical tests were observed. Comparing hydroxyapatite-coated versus uncoated implants, the histomorphometric results showed statistical significance in the percentage of bone (p = 0.01); and in bone index, ratio between bone ingrowth and bone ongrowth (p = 0.01). The size of the bone implant interface was smaller in the hydroxyapatite-coated implants than in the uncoated (p = 0.029). Beneficial effects of hydroxyapatite applied to spherical bead titanium porous coatings were demonstrated. These morphological and histomorphometric results support the concepts involved with the use of hydroxyapatite as a coating for uncemented porous prosthetic devices.