THE INFLUENCE OF BONY ARCHITECTURE ON FIXED MEMBRANOUS BONE-GRAFT SURVIVAL

The aim of this study was to examine the influence of membranous bone graft architecture on graft survival. Eighteen adult New Zealand rabbi ts underwent full-thickness harvesting of their zygoma, which was then divided into two parts, resulting in a wider, thicker anterior graft and a tapered posterior graft. The grafts were then rigidly fixed, one to each nasal bone, using titanium lag screws. On postgrafting days 1 5 and 45, 3 animals each were killed. The remaining 12 animals were ki lled on day 90. The graft, graft-host interface, and contralateral zyg oma were assessed volumetrically, histologically (nondecalcified), and stereologically. Volumetrically, the anterior (thicker, wider) grafts demonstrated 100% survival while the posterior (thinner, more narrow) grafts demonstrated 80% survival (p = 0.004). Histologically, the ant erior grafts demonstrated less resorption and porosity and greater lab eling activity. At the graft-host interface, the anterior grafts exhib ited a 2.5-fold increase in full incorporation of the grafts, and the posterior grafts had almost twice the incidence of nonincorporation. S tereological measurements, including interlabel width (20.3 mu m anter iorly, 18.9 mu m posteriorly), confirmed the enhanced survival of the anterior grafts. Using multiple forms of analyses, this study demonstr ates that membranous bone graft architecture influences graft survival . To assist in understanding these differences, we also analyzed the n ormal contralateral zygoma. While the anterior and posterior halves ha d a relatively constant amount of bicortical bone, the thicker grafts had a proportionally greater trabecular component (i.e., increased dip loe-to-cortical ratio). in the rabbit model, differences in membranous bone thickness imply differences in the cancellous portion of the gra ft, thereby influencing ultimate graft survival.