Bone graft incorporation - Effects of osteogenic protein-1 and impaction

Impaction of cancellous bone grafts in a bone chamber in rats in a previous study led to decreased ingrowth of new bone after 6 weeks compared with un impacted grafts. The current study analyzes whether this decrease represent ed a final loss of ingrowth or just a delay, if the decrease was influenced by immunologic factors, and if it was possible to influence the inhibitory effect by adding a bone morphogenetic protein. Bone chambers with impacted or unimpacted bone grafts were implanted bilaterally in rat tibias, The me an bone ingrowth distance into the graft was measured on histologic section s. Three experiments were done: (1) the bone ingrowth into impacted and uni mpacted grafts was studied at 6 and 12 weeks; (2) the immunologic influence was studied by comparing isogeneic grafts with allogeneic grafts; and (3) the authors tried to influence the decrease in bone ingrowth in impacted gr afts by adding osteogenic protein-1. Bone ingrowth into the impacted graft was decreased at 6 weeks but not at 12 weeks. No difference was found betwe en isografts and allografts at 6 weeks. With the addition of osteogenic pro tein-1, the impacted grafts showed dramatically increased bone ingrowth, Im pacted bone grafts are incorporated at a slower rate than were structural g rafts. The delay can be reversed by adding osteogenic protein-1, making ing rowth faster than in structural bone.