基于X线片的十二等分法评估全椎弓根螺钉固定矫形术治疗青少年特发性脊柱侧凸的置钉准确性

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

中文关键词:  十二等分法  置钉准确率评价  青少年特发性脊柱侧凸  X线片  CT平扫

英文关键词:The Rule of Twelve  Evaluation of screw placement accuracy  Adolescent idiopathic scoliosis  X-ray film  CT scan

中文摘要:

  【摘要】 目的：利用基于X线片的十二等分法评估单纯后路全椎弓根螺钉固定矫形术治疗青少年特发性脊柱侧凸（adolescent idiopathic scoliosis，AIS）的置钉准确性。方法：回顾性分析我科行单纯后路全椎弓根螺钉固定矫形术治疗的AIS患者40例（女性34例，男性6例），年龄15.2±1.9岁（11~18岁），分别采用传统方法和十二等分法在X线片上评估椎弓根螺钉置钉准确性，并通过CT平扫验证。传统方法：A级，螺钉钉尖在椎弓根内壁和椎体中线之间，且与相邻螺钉相比无明显偏内或偏外；B级，螺钉钉尖超越椎体中线或与相邻螺钉相比明显偏内；C级，螺钉钉尖在椎弓根内壁以外或与相邻螺钉相比明显偏外。十二等分法：将椎体由凹侧外侧缘及凸侧外侧缘向分别正中线画等分线分12等份，并根据螺钉钉尖在所在椎体上的位置和椎体旋转的程度确定相应的安全范围。A级，螺钉钉尖在安全范围内；B级，螺钉钉尖超出安全范围内界或与相邻螺钉相比明显偏内；C级，螺钉钉尖超出安全范围外界或与相邻螺钉相比明显偏外。CT平扫：A级，螺钉全部在椎弓根内；B级，螺钉有任何部分超出椎弓根内壁；C级，螺钉有任何部分超出椎弓根外壁。通过卡方检验和诊断试验结果法对比两种X线片评估方法的准确性。结果：CT平扫评估，638枚螺钉中595枚（93.3%）A级，9枚（1.4%）B级，34枚（5.3%）C级；十二等分法，589枚（92.3%）A级，10枚（1.6%）B级，39枚（6.1%）C级；传统方法，582枚（91.2%）A级，19枚（3.0%）B级，37枚（5.8%）C级。使用传统方法误判螺钉49枚（7.7%）枚，十二等分法误判螺钉14枚（2.2%）枚，二者有显著差异（P<0.001），其中B级误判的螺钉分别为25枚（3.9%）和5枚（0.8%）（P<0.001），C级误判的螺钉分别为24枚（3.8%）和9枚（1.4%）（P=0.006）。此外，使用传统方法和十二等分法，评估凹侧椎弓根置钉的误判率高于凸侧，评估旋转较大椎体置钉的误判率高于旋转较小的椎体。结论：在X线片上采用十二等分法评估AIS患者的置钉情况简便、可靠，可以提高评估螺钉置钉的准确性。

英文摘要:

  【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.