Short-term external support promotes healing in semirigidly fixed fractures

The effect of different postoperative treatments on the healing of rabbit femoral shaft fractures fixed semirigidly by intramedullary nailing was investigated clinically, radiologically, and mechanically. A unilateral transverse midfemoral fracture was performed on all rabbits and was treated with an intramedullary nailing without previous reaming. When the operated limb was immobilized postoperatively by a splint with the knee in extension for 1 week (Group 2), nine of 10 fractures healed. When immobilized in extension for 7 weeks (Group 3), eight of 10 healed. When immobilized in flexion for 7 weeks (Group 4), five of 10 fractures were clinically healed within 7 weeks. When the limb was not immobilized by external support (Group 1), only one of 10 healed. The radiologic healing correlated with the clinical healing in each group. There were no statistically significant differences among the groups in the quantity of callus or in the biomechanical properties of the healed fractures. The results indicate that even a short term additional external support of the limb with the knee in extension was advantageous to the healing of femoral shaft fractures fixed semirigidly by intramedullary nailing.