Objective To investigate the effect of a self-designed star-shaped washer on the biomechanical performance of pedicle screw fixation systems under osteoporotic conditions. Methods Twelve synthetic osteoporotic vertebral models were randomly assigned to screw group or washer group according to the left and right pedicles. In the screw group, pedicle screws were inserted directly, whereas in the washer group, the washers were fixed to the vertebral models prior to the insertion of the same pedicle screws. The maximum insertion torque and tightening torque were recorded for both groups. Cyclic fatigue testing was performed to measure the failure load and the number of cycles to failure (initial load －150 to 150 N, increased by 25 N every 500 cycles until cephalocaudal displacement ＞5 mm). Independent-samples t-tests were used to compare intergroup differences, and Pearson correlation analysis was used to examine the correlations between the indexes. Results The tightening torque ([1.89±0.17] N·m vs [1.48±0.18] N·m, P＜0.001), failure load ([396.67±41.23] N vs [356.25±37.51] N, P=0.016), and number of cycles to failure (5 142±932 vs 4 352±874, P=0.036) were all significantly higher in the washer group than in the screw group. However, there was no significant difference in maximum insertion torque between the 2 groups ([0.89±0.11] N·m vs [0.85±0.12] N·m, P=0.380). Tightening torque showed positive correlation with both failure load (r=0.68, P＜0.001) and the number of cycles to failure (r=0.71, P＜0.001). Conclusion Under osteoporotic conditions, the addition of a star-shaped washer significantly improves the tightening torque, fatigue resistance, and load-bearing capacity of pedicle screws, thereby enhancing the stability of pedicle screw fixation. This method holds potential clinical value for improving spinal internal fixation systems in patients with osteoporosis.