The histomorphologic changes in vascularized bone transfer and their interrelationship with the recipient sites: a 1-year study.

In 13 New Zealand White rabbits with a mean age of 6 months, vascularized bone transfers incorporated as paired auricular anterior myo-osseous flaps were harvested; they were placed in either an inlay or an onlay position relative to the zygomatic arch. The onlay bone transfers were placed either in full contact or in partial contact with the zygomatic arch. The animals were sacrificed 1 year after transfer. At 1 year, the inlay transfer simulated the adjacent zygoma in width and thickness. Onlay full contact transfers maintained significant aug mentation in thickness of the zygoma, while the onlay partial contact transfers did not; the thickness of the augmented zygoma in the onlay full contact subgroup was significantly greater than that in the onlay partial contact transfers. The onlay partial contact grafts had remodeled into the zygoma in bone contact, where the orientation of mismatched osteons within the bone transfers had transformed to match that of the native zygoma. In areas of bone contact between the onlay and the host bone, full-thickness conversion from a cortical to a trabecular architecture had occurred in both the transfer and host bones. These findings have numerous implications regarding mechanisms that could be exploited clinically to optimize the survival of a bone transfer; they also raise questions regarding alteration of the recipient bed after placement of an onlay bone transfer.