Survival of split calvarial bone grafts in a dog model

To gain a better understanding of the strength and long term viability of split calvarial bone graft, nine mongrel dogs each received four trephine craniotomies (1.5 mm diameter). The harvested bone plugs were split through the diploe and a partial-thickness plug was returned to each craniotomy site. The unused partial-thickness plugs underwent strength testing. After 90-150 days the dogs were sacrificed, bone scans and X-rays of the graft recipient sites performed, and the grafted plugs harvested for strength testing and histologic examination. Bone scanning showed increased osteoblastic activity within the grafts, strength testing showed a progressive loss in strength over the 150 days, and histologic examination demonstrated a creeping substitution. These results imply a similar evolution in strength and remodeling to that seen in long-bone grafts, whose remodeling typically spans 1 year.