External fixation compared to intramedullary nailing of tibial fractures in the rat

BACKGROUND AND PURPOSE It is not known whether there is a difference in bone healing after external fixation and after intramedullary nailing. We therefore compared fracture healing in rats after these two procedures. METHODS 40 male rats were subjected to a standardized tibial shaft osteotomy and were randomly assigned to 2 treatment groups: external fixation or intramedullary nailing. Evaluation of half of each treatment group at 30 days and the remaining half at 60 days included radiography, dual energy radiographic absorbtiometry, and mechanical testing. RESULTS Radiographically, both treatment groups showed sign of fracture healing with gradual bridging of the fracture line, while with intramedullary nailing the visible collar of callus was increased peripherally, indicative of periosteal healing. At 30 days, densitometric and mechanical properties were similar in the 2 groups. At 60 days, however, the intramedullary nailed bones had more strength, greater callus area, and higher bone mineral content in the callus segment compared to externally fixated fractures. INTERPRETATION Tibial shaft fractures in the rat treated with external fixation and intramedullary nailing show a similar healing pattern in the early phase of fracture healing, while at the time of healing intramedullary nailing provides improved densitometric properties and superior mechanical properties compared to external fixation. Clinical findings indicate that intramedullary nailing in human tibial fractures may be more advantageous for bone healing than external fixation, in a similar way.