OBJECTIVETo compare biomechanical effect of the closed fracture model with intramedullary nail fixation and the open fracture model with plate fixation in rats.

METHODSForty 8-week-old Spragu-Dawley male rats were divided into two groups randomly. Left femoral shaft closed fractures model was created in 20 rats, and treated with intramedullary nail. Other 20 rats received open osteotomy on the left femoral shaft, and were fixed by plate. Rats were sacrificed and draw the materials at 4, 6, 8 and 12 weeks in batch. Across section area and volume of callus were measured, peak load, restoration rate of peak load were tested. The biomechanical efficency of two methods of femoral shaft fracture fixation were compared.

RESULTSThe difference of surgical duration was statistically significant between two groups (P < 0.001). At 4, 6, 8 and 12 weeks, the difference of peak load, restoration rate of peak load, volume and area of callus was also statistically significant between two groups (P < 0.05).

CONCLUSIONOpen fracture model with plate fixation led to delayed healing compared with closed fracture model with intramedullary nail. However, open fracture model with plate fixation model could be a valuable research tool to study the healing consequences of cortical bone, which may provide insight into the pathogenesis and ideal treatment of fractures or nonunions.