A histomorphometric study of rabbit tibiofibular bones after rigid intramedullary nailing.

The effects of rigid intramedullary nailing on cortical bone structure were studied in osteotomized and non-osteotomized rabbit tibiofibular bone at time intervals ranging from three to 24 weeks postoperatively. Histological specimens were analysed morphometrically observing changes in cortical bone and the medullary cavity in transverse sections distal to the tibiofibular junction. Throughout the series, when compared to intact control bones, computerized planimetry revealed significant differences only in the osteotomized bones. At 24 weeks, the area of whole cortical bone was less and the area of the medullary cavity greater in the osteotomized bones than in respective control bones. The reason for these changes seemed to be a profound resorption of subendosteal bone. The amount of cortical osteoporosis was slight, but a steady increase could be seen towards the end of the experiment. The results suggest that the morphological changes in cortical bone detected in the present study mostly depend on the operative trauma and not so much on the protection from stress provided by the rigid intramedullary nail.