Intramedullary nailing and cortical bone mineral content. Photon absorptiometry measurements in vitro

A transverse diaphyseal osteotomy of the tibia was stabilized using rigid intramedullary nailing in rabbits. In a 2nd group, nailing was performed without osteotomy. The rabbits were sacrificed 3 to 24 weeks postoperatively, and the nails were removed. The mineral content (BMC) was measured by dual photon absorptiometry and the mineral density (BMD) was calculated. At 24 weeks the osteotomized bones had significantly lower BMC values than did the respective nonosteotomized bones or the intact bones. The BMC of the nonosteotomized bones remained above the control level throughout the experiment. The minimum BMD values of the osteotomized bones were detected at 3 weeks, whereafter they gradually approached the control level over time. The results suggest that rigid intramedullary nailing in connection with osteotomy causes a significant decrease in cortical bone mineral mass, seen at 24 weeks postoperatively. The photon absorption method used seemed sensitive enough to detect changes in cortical bone mineral quantity in these experimental conditions.