The influence of nail blocking conditions in cattle femoral fractures

To investigate the effect of different fixation strategies of the intramedullary interlocking nail (IIN) on the mechanical behavior of a polymeric implant applied for femoral fracture fixation in calves, and to evaluate the performance of a glass fiber-reinforced polymer applied in a bovine femoral fracture reduction system, five Holstein male animals with a mean weight (±SD) of 62.8 ± 20.4 kg and aged 74 ± 15 were used to generate biomechanical parameters for this study. Twelve models of the fractured bovine femur, simulating a simple oblique fracture, were developed for use during the simulations. The models were divided into three groups, with each group of four models being associated with a different fixation strategy. Models were used to simulate the loading conditions corresponding to a calf in the transition (decubitus position to static position) condition. The maximum stresses found in each set (bone/implant) were compared with the reference stresses of each nail material.

Maximum implant stresses were found in the screws and at the interface between the screw and the nail. The performance of implants was influenced by the material and fixation strategy, which can be confirmed by the stress values found in the set. The analysis indicated that the composite nail is able to withstand the loading demands in all fixation strategies.

The finite element analysis (FEA) demonstrated that all polymeric materials analyzed provided sufficient resistance to withstand the loading forces imposed to the femur when an adequate blocking strategy was applied.