Abstract:[Objective] To explore the risk factors of proximal femoral nail anti-rotation (PFNA) failure for internal fixation of femoral intertrochanteric fractures. [Methods] A retrospective study was performed on 110 patients who received PFNA for femoral intertrochanter- ic fractures in our hospital from January 2017 to January 2020. The patients were divided into failure group and success group according to whether internal fixation failure occurred during follow-up. Univariate comparison and binary multiple logistic regression analysis were con- ducted to explore the risk factors of the internal fixation failure. [Results] All the 110 patients had PFNA fixation performed smoothly, and were followed up for 12~16 months. During follow-up, 12 patients were proved internal fixation failure, accounting for 10.91%, while the re- maining 98 patients got successful fixation, accounting for 89.09%. Patients were divided into two groups according to whether internal fixa- tion failure occurred. There were no significant differences in gender, age, body mass index, side of injury, tip-apex distance (TAD) be- tween the two groups (P>0.05) . However, the failure group had a significantly higher ratio of incomplete lateral wall (P<0.05) , significantly higher ratio of poor fracture alignment (P<0.05) , significantly higher ratio of the negative support of medial cortex (P<0.05) , and signifi- cantly higher ratio of poor spiral blade placement than the success group (P<0.05) . As result of multivariate logistic regression, the incom- plete lateral wall (OR=14.424, P=0.007) , poor fracture alignment (OR=6.578, P=0.033) , negative support of medial cortex (OR=17.17, P= 0.005) , and poor spiral blade placement (OR=8.403, P=0.005, P=0.038) were the independent risk factors for internal fixation failure. [Conclusion] Incomplete lateral wall, poor reduction alignment, negative medial cortical support, and poor position of spiral blade are risk factors for PFNA failure.