Finite element biomechanics of novel intramedullary nails with varying diameters for intertrochanteric femoral fractures with lateral wall injury.

Abstract

<h4>Objective</h4>This study aimed to compare the fixation performance differences between the traditional proximal femoral nail antirotation (PFNA), "II" proximal femoral bionic nail (PFBN), and proximal femoral total bionic nail (PFTBN) in the treatment of intertrochanteric femoral fractures complicated by lateral wall injury using finite element analysis. Additionally, it intended to explore the biomechanical effects of reamed versus unreamed techniques on these novel intramedullary nail devices.<h4>Methods</h4>Validated FEA models of intertrochanteric fractures (lateral wall injury) were constructed with 9 mm (unreamed) and 11 mm (reamed) medullary canals, followed by implantation of PFNA, "II" PFBN, or PFTBN. Under a vertical load of 2100 N, Von Mises Stress (VMS) and displacement of the femur and implants were quantified.<h4>Results</h4>Under a vertical load of 2100 N, in the unreamed condition, the PFTBN exhibited the lowest peak stress and displacement among the three devices, followed by the "II" PFBN, while the traditional PFNA showed the poorest performance. After reaming, all three implants demonstrated increased peak stress and slightly elevated peak displacement; however, PFTBN remained the most stable. Notably, reaming significantly reduced the overall peak stress of the femur. Collectively, PFTBN more effectively reduced the stress and displacement of both the femur and the implant under both reamed and unreamed conditions, with "II" PFBN showing intermediate efficacy. Both novel devices provided superior internal fixation stability compared to PFNA, which may contribute to a reduced risk of postoperative complications.<h4>Conclusion</h4>PFTBN outperforms "II" PFBN and PFNA in load/shear resistance for intertrochanteric fractures with lateral wall injury, regardless of reaming. "II" PFBN also shows superior stability to PFNA. Reaming increases nail-bone contact, mitigating femoral stress concentration and refracture risk. Both PFTBN and "II" PFBN are reliable fixation options with promising clinical utility.