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 partial osteotomies with an 8 mm intermediary fragment in the femoral diaphysis and in the other group a simple partial osteotomy. The osteotomies were then manually broken, retaining the periosteal and muscular attachment 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, and 12 weeks, 8 rats in each group were killed, and callus formation, mechanical parameters and bone blood flow were evaluated. There were no differences in callus production between the simple and segmental fractures throughout the experimental period. The mechanical parameters increased in both groups, and the healing patterns were the same. No differences 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 that in the simple fractures. Our findings indicate that closed segmental fractures treated by intramedullary nailing can regain strength in the same manner as simple fractures.