Finite element analysis of full-thread versus half-thread hollow nail in FNS fixation of Pau-wels type Ⅲ femoral neck fractures among young adults

Xu Bin; Yang Yan; Chai Hao; Wang Guosheng

doi:10.3969/j.issn.1009-4237.2025.12.008

Abstract：Objective To compare the biomechanical properties of full-threaded vs.half-threaded hollow nail combined with femoral neck system(FNS)in managing Pauwels type III femoral neck fractures among young and middle-aged patients by finite element(FE)analysis.Methods A healthy 28-year-old female volunteer was enrolled,who underwent 64-slice spiral CT scan to obtain the femoral imaging data and establish a femoral neck frac-ture model(Pauwels angle set at 70°).Three internal fixation models were constructed in SolidWorks 2021,respec-tively group A(single FNS),group B(FNS+half-threaded hollow nail),and group C(FNS+full-threaded hollow nail).The assembled models were imported into FE analysis software,where a vertical load of 1000 N was applied to simulate the single-leg standing posture.Von-Mises stress peak values and displacement measurements were re-corded for the femur,proximal bone fragments,and internal fixation devices.Results The femur model in group C exhibited the lowest peak stress of 93.883 MPa with uniform distribution,showing no significant stress concentra-tion.The proximal fracture fragment demonstrated the lowest peak stress(24.764 MPa)and displacement value(1.483 mm)among all groups.Regarding the internal fixation devices,group C recorded the highest peak stress(431.45 MPa),while group A had the lowest(273.04 MPa).Both the femur and fracture fragments showed mini-mal overall displacement in group C,measuring 1.592 mm and 1.483 mm,respectively.Conclusion The fixation of Pauwels type III femoral neck fractures with FNS combined with full-threaded hollow nail has better biomechanical stability,more reasonable stress distribution and less fracture displacement,which can be used as the preferred inter-nal fixation for this type of fracture.