Osteogenic protein 1 device stimulates bone healing to hydroxyapaptite-coated and titanium implants

This study evaluated the effects of osteoogenic protein 1 (OP-l) placed in a gap around uncoated and hydroxyapatite (HA)-coated implants. Unloaded cylindrical titanium alloy implants were inserted in the femoral condyles of 16 skeletally mature dogs surrounded by a 3-mm gap. The gap around the implants was filled with 325 mu g OP-l in 130 mg bovine collagen type I as carrier (OP-l device) or collagen carrier alone or left empty. All groups were tested with both HA-coated and uncoated implants, and the animals were sacrificed after 6 weeks. Implant fixation was determined by push-out lest. Bone ongrowth and bone formation were evaluated by quantitative histomorphometry. OP-l device enhanced mechanical fixation of uncoated and HA-coated implants, resulting in a higher shear strength than implants with collagen matrix and control implants. Bone ingrowth and bone formation in the gap were also stimulated 3-fold for OP-l groups when compared with empty controls, but no difference was found between OP-l groups and collagen matrix groups. This study suggests that the OP-l device placed in a gap around uncoated and HA-coated implants is capable of enhancing mechanical fixation and periimplant bone formation. The collagen carrier alone also enhanced bone ongrowth and fixation significantly.