Osteopromotive membranes enhance onlay integration and maintenance in the adult rat skull

This study aimed to evaluate the effect of an osteopromotive membrane technique on onlay bone graft survival. Unicortical bone grafts were positioned bilaterally below the temporal muscle in 21 adult Lewis rats. In 14 rats, the bone graft on the right side was covered by an expanded polytetrafluoroethylene GORE-TEX(R) membrane, whereas that on the left side was left uncovered. Seven rats were killed after 12 (group 1) and 20 (group 2) weeks, respectively. The remaining animals (n=7, group 3) received membranes bilaterally, of which the right-sided membrane was removed after 12 weeks, and these animals were killed after 20 weeks. The specimens were assessed by routine histology and immunohistochemical labelling for various matrix proteins. After 12 weeks (group 1), size differences between the sides were not significant, although all control onlay bone grafts showed microscopic signs of pronounced resorption. At 20 weeks (group 2), graft integration was more complete on the membrane side. For group 3, the height was significantly more preserved on the side where the membrane was not removed. Immunolabelling demonstrated a more intense bone remodelling at the membrane sites. Membrane treatment resulted in improved graft integration and significantly greater size persistence, but complete height was not maintained.