Objective To evaluate the femur biomechanical changes of finite analysis with different femoral stem ex-tension implants in total knee arthroplasty (TKA). Methods The full-length femoral CT scan was performed in selected healthy volunteers. The femoral digital model was established with Mimics 10.0 and Geomagic Studio 10.0 software. The models of femoral prosthesis and stem extension implant were created by laser scanner. According to the common three hip loading modes (1 586 N, 1 690 N and 2 132 N), the maximum principal stress (MPS), the maximum principal elastic deforma-tion (MPES) and MPES distribution changes were recorded and analyzed by three-dimensional finite element analysis with ANSYS Workbench13.0 software. Results The MPS values before TKA were 98.54, 147.36 and 143.51 MPa respectively when values of femoral head loading were 1 586 N, 1 690 N and 2 132 N. With the increase in the length of the femoral pros-thesis extension rod, the MPS and MPES showed a decreasing trend. There was a positive correlation between free femur ra-tio (FFR) and MPES (P<0.05). The MPES distribution was gradually concentrated at the top point of femur stem extension implant with the increase in the length of the femoral prosthesis extension rod. Conclusion The values of MPS and MPES were gradually decreased with the increase in the length of the femoral stem extension implant. There was a positive linear correlation between FFR and MPES. The stress concentration was focused obviously at the top end of femoral stem extension implant with its length more than 120 mm.% 目的明确全膝关节置换（TKA）翻修术中不同长度股骨延长杆对股骨生物力学影响的有限元分析。方法选择健康志愿者进行股骨全长CT扫描，以Mimics 10.01和Geomagic Studio 10.0软件建立股骨数字化模型，同时采用激光扫描仪对股骨假体和延长杆进行扫描建模。按照常见的3种髋关节负荷模式（1586 N、1690 N、2132 N）采用ANSYS Workbench v13.0软件进行三维有限元分析，记录股骨最大主应力（MPS）、最大主弹性形变（MPES）和MPES分布情况并分析。结果 TKA前股骨头负荷为1586 N、1690 N、2132 N时股骨干MPS分别为98.54、147.36、143.51 MPa。随着股骨假体延长杆增长，MPS、MPES逐渐降低。自由股骨比值与MPES之间呈正相关（P<0.05）。随着延长杆长度增加，MPES逐渐集中于延长杆顶端。结论股骨MPS和MPES随着延长杆长度增加逐渐降低，自由股骨比值与MPES之间存在线性正相关，延长杆大于120 mm明显导致顶端应力集中。
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