Failure of onlay bone grafts to integrate over the calvarial suture: observations in adult isogeneic rats.

Bone grafting constitutes an important tool in cranio-maxillofacial skeletal reconstruction and augmentation. Much effort has been directed to improve graft survival and volumetric maintenance. The effects of the sutural tissue proper on graft incorporation has not yet been explored. The purpose of this report was to analyze the effects of positioning an onlay graft over a non-growing sutural region. Twelve adult rats received femoral or tibial uni- or bicortical grafts placed over the temporal suture. The findings were assessed by routine microscopy and immunohistochemistry after 4, 12, and 20 weeks. The sutural tissue expanded between the graft and the host bed in an umbrella-like pattern, which locally inhibited graft incorporation. Of the tested cartilage and bone proteins and proteoglycans, labelling was distinct only for osteopontin and fibromodulin, indicating a moderate remodelling activity in the area. The importance and consequences of the findings are discussed.