Repair of Massive Allografts: Histological, Nuclear Medicine and CT-Studies

Summary

The repair of massive osteoarticular allografts was evaluated by invasive and non-invasive techniques utilizing histological biopsies, isotopes, particularly the SPECT method, and computed tomography (CT) techniques.

With regard to osteogenesis four different morphological anatomic areas were found. New bone formation began first at the host-graft junction induced by the host’s periosteum and the autogenous bone grafts. In the cortex postresorptional osteogenesis occurred as a thin appositional layer of lamellar bone. In the subchondral bone cyst-like small cavities resulting from resorption of Haversian canals revealed new lamellar bone of varying degree lining the cavity walls. However, large areas of the grafts remained necrotic and the new bone formation event (creeping substitution) was a long drawn-out process lasting years. The proportion of new bone formation averaged 36% (range 5–75%). Bone scans and SPECT (Single Photon Emission Computed Tomography) studies with ^99mTcDPD indicated slight activity only at the outer layer of the cortex corresponding to histological observations. Computed tomography (CT) studies revealed first thinning and irregular defects of the cortex and small subcortical cysts. Later these resorptive changes repaired by gradual thickening of the cortex. On CT a neocortex, a circumferential bony structure inside the normal cortex was found to develop over several years.