THE VIABILITY OF CRYOPRESERVED ONLAY CRANIAL BONE ALLOGRAFTS - A COMPARATIVE EXPERIMENTAL-STUDY VERSUS FRESH AUTOGRAFTS

It is well known that calvarial bone autografts are the bone grafts th at are the least reabsorbant and have the best long-term evolution in craniofacial surgery. However, they do have certain limitations: (1) r eabsorption results in repeated surgery and the need for new donor are as, (2) a limited amount of autogenous cranial bone is available (due to avoiding areas close to cranial sutures and venous sinuses, and bec ause the temporal bone is very fragile and the cranium has not fully d eveloped in children), and (3) graft extraction increases surgical tim e and morbidity. Because of this, we present an alternative to calvari al bone autografts: cryopreserved allografts. This paper is an experim ental prospective study carried out on sheep with the following goals: (1) to assess the behavior of calvarial onlay bone grafts cryopreserv ed at -80 degrees C, using fresh autografts implanted under the same c onditions as controls; (2) to compare reabsorption percentages statist ically over time; and (3) to study qualitatively any histological vari ations, The results obtained are (1) more reabsorption of allografts w hen compared to autografts (at 90 days, 21.97% versus 20.21% of grafte d volume), although this difference is not statistically significant; (2) a reduction in height in all onlay grafts as a consequence of the loss of the diploe; (3) the absence of any type of inflammation caused by a reaction to cryopreserved allografts; and (4) bone substitution performed using frozen allografts is histologically similar to that us ing fresh autografts.