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| HE Zhong,QIN Xiaodong,YIN Rui.A study of Rule of Twelve on X-ray film in evaluating the accuracy of screw placement in the treatment of adolescent idiopathic scoliosis with all pedicle screw instrumentation[J].Chinese Journal of Spine and Spinal Cord,2020,(7):580-588. |
| A study of Rule of Twelve on X-ray film in evaluating the accuracy of screw placement in the treatment of adolescent idiopathic scoliosis with all pedicle screw instrumentation |
| Received:September 20, 2019 Revised:April 09, 2020 |
| English Keywords:The Rule of Twelve Evaluation of screw placement accuracy Adolescent idiopathic scoliosis X-ray film CT scan |
| Fund:江苏省自然科学基金（编号：BK20190119） |
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| English Abstract: |
| 【Abstract】 Objectives: Use the Rule of Twelve based on X-ray film to evaluate the accuracy of pedicle screw placement in adolescent idiopathic scoliosis(AIS) patients after scoliosis correction surgery. Methods: This study retrospectively reviewed 40 patients(34 females and 6 males) with AIS who underwent posterior correction surgery with all pedicle screw instrumentation in our hospital. The mean age was 15.2±1.9 years(11-18 years). The traditional method and the Rule of Twelve were used to evaluate the degree of pedicle screw placement on X-ray films, which was verified by CT scan. The traditional method was as follows: degree A, the screw heads were between the inner wall of the pedicle and the vertebral midline, and were not obviously inward or outward compared with adjacent screws; degree B, the screwheads were beyond the vertebral centerline or obviously inward compared with adjacent screws; degree C, the screw heads were outside the inner wall of the pedicle or obviously outward compared with adjacent screws. The Rule of Twelve was as follows: the vertebrae were divided from the concave lateral edge to the centerline and from the convex lateral edge to the centerline into 12 equal parts, and the safety range was determined according to the position of the screw on the vertebra and the degree of vertebral rotation. Degree A, the screwheads within the safety range at the rotation; degree B, the screwheads were beyond the median boundary of the safety range and were obviously inward compared with adjacent screws; degree C, the screwheads were outside the lateral boundary of the safety range and were obviously outward compared with adjacent screws. Axial CT scan: degree A, the screws in the pedicle; degree B, any part of the screws was beyond the inner walls of the pedicle; degree C, any part of the screws was beyond the outer walls of the pedicle. In addition, the accuracy of evaluating screw placement might be affected by the direction and degree of vertebral rotation, so the position(convex and concave) of the screws and the Nash-Moe rotation(0-Ⅳ degrees) of the vertebrae were recorded and analyzed. The accuracy of the two methods was compared using the chi-square test and the diagnostic test. Results: According to the CT scan, 595 out of 638(93.3%) screws were classified as degree A, 9(1.4%) as degree B, and 34(5.3%) as degree C. The Rule of Twelve showed 589(92.3%) screws were classified as degree A, 10(1.6%) as degree B, 39(6.1%) as degree C; while, the traditional method showed 582(91.2%) were classified as degree A, 19(3.0%) as degree B, 37(5.8%) as degree C. The misjudged screws were 49(7.7%) using the traditional method and 14(2.2%) using the Rule of Twelve, and there was significant difference between the two methods(P<0.001). Among these, the misjudged screws in degree B were 25(3.9%) and 5(0.8%) (P<0.001), respectively. The misjudged screws in degree C were 24(3.8%) and 9(1.4%)(P=0.006), respectively. Furthermore, for traditional method and the Rule of Twelve, the misjudgement rate of evaluating screws was higher on the concave side than on the convex side, and was higher on the vertebrae with morerotation. Conclusions: The Rule of Twelve on X-ray film can improve the accuracy in judgingscrew misplacement in AIS patients. |
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