Effect of osteogenic protein 1/collagen composite combined with impacted allograft around hydroxyapatite-coated titanium alloy implants is moderate

This study evaluated the effects of osteogenic protein 1/collagen composite (OP-1/col) mixed with impacted allograft around hydroxyapatite (HA)-coated titanium alloy implants in a canine model. The aim of the study was to tes t different doses of OP-1 growth factor in a collagen composite for stimula tory effect on allograft incorporation around an implant. Unloaded implants were inserted in each proximal. humerus of 16 skeletally mature dogs. The cylindrical implants (4 x 9 mm) coated with KA were initially surrounded by a 3-mm. gap into which allograft mixed with OP-1/col. was impacted. Two di fferent doses of OP-1 were investigated. In eight animals 325 mg OP-1 prote in and 130 mg bovine collagen type I as carrier were mixed with the allogra ft chips. This composite is identical to the clinically used OP-1 device ca lled Novus. In another eight animals a lower dose of 65 mg OP-1 protein and 130 mg bovine collagen type I was used. Control implants placed in the con tralateral humerus were surrounded by allograft mixed with collagen carrier only. The dogs were euthanized at 6 weeks. Implant fixation was determined by push-out testing. Bone ingrowth and bone formation were evaluated by qu antitative histomorphometry on serial sections of the bone-implant interfac e. Impacted allograft together with low-dose OP-1 enhanced bone volume in a zone adjacent to HA-coated titanium alloy implants. The high dose had no e ffect on bone formation. Mechanical fixation, bone ingrowth, and bone volum e in the gap near the original trabecular bone were unaffected by both low and high OP-1/col composite. In this model and observation period, the low dose of OP-1/col composite mixed with impacted allograft has a moderate eff ect on bone healing around HA-coated implants and no effect on implant fixa tion. (C) 2001 John Wiley & Sons, Inc.