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 μm. 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 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.