HEALING OF SEGMENTAL AND SIMPLE FRACTURES IN RATS

We studied the healing of segmental and simple middiaphyseal fractures in male Wistar rats. In one group we produced two standardized partia l osteotomies with an 8 mm intermediary fragment in the femoral diaphy sis and in the other group a simple partial osteotomy. The osteotomies were then manually broken, retaining the periosteal and muscular atta chment on the medial side. The fractures were stabilized with a 1.6 mm steel pin, and the animals were allowed free movement. After 4, 8, an d 12 weeks, 8 rats in each group were killed, and callus formation, me chanical parameters and bone blood flow were evaluated. There were no differences in callus production between the simple and segmental frac tures throughout the experimental period. The mechanical parameters in creased in both groups, and the healing patterns were the same. No dif ferences were found in the total bone blood flow, but the callus blood flow in the segmental fractures was lower after 8 and 12 weeks than t hat in the simple fractures. Our findings indicate that closed segment al fractures treated by intramedullary nailing can regain strength in the same manner as simple fractures.