BACKGROUND:Some studies have showed that the accuracy and surgery outcome of the percutaneous pedicle screw implantation was superior to open surgery, but the relationship between the angle of pedicle screws and screw stability is stil unclear in previous studies. OBJECTIVE:To investigate the effect of different angles of implanted screws on the stability of pedicle screw. METHODS:A total of 30 vertebral specimens of adult pigs were selected and screws were implanted respectively according to different coronal and sagittal angles. The maximum pul-out strength of screws from each specimen was tested by machine. Load-displacement curves were drew and statistical y analyzed. RESULTS AND CONCLUSION:The maximum pul-out strength and maximum energy of screw with 10° and 15° coronal and sagittal angles implantation were significantly better than those of 0° angle group (P<0.05). When the stress exceeded the maximum pul-out strength, the pul-out strength of screw decreased gradual y. The curves in coronal and sagittal 10° and 15° angle groups was similar, and the slope was better than 0° angle group (P<0.05). These results confirm that the angle of the implanted screw provides effective assistance to the stability of percutaneous pedicle screw. After the looseness of the screws, the pul out strength shows a steady downward trend.