A feasibility study on CT quantitative scoring in assessing the reduction difficulty of atlantoaxial dislocation and basilar invagination

English Keywords:Atlantoaxial dislocation  Basilar invagination  Bidirectional traction of the cervical  Atlantodens interval  Vertical distance from dens to Chamberlain line  Reduction

English Abstract:

  【Abstract】 Objectives: To explore the feasibility of applying CT quantitative scoring analysis in evaluating the reduction difficulty of atlantoaxial dislocation and basilar invagination, and to provide guidance for surgical decision-making. Methods: From March 2018 to December 2019, 88 patients with atlantoaxial dislocation underwent cervical thin-slice CT scans after admission. The quantitative scoring was based on the defined image features, inlcuding: 0 point, flat and horizontal atlantoaxial joint; 1 point, slightly sloped atlantoaxial joint; 1.5-2 points, more obvious sloped atlantoaxial joint; 2 points, osteophytes in atlantoaxial joint; 3 points, ball-and-socket deformity, interlocking, callus in atlantoaxial joint, and anlanto-odontoid bony fusion or blocking. The total scores of assignments of lateral mass joints and atlanto-odontoid joints on both sides were calculated separately, and divided into 4 grades: gradeⅠ(0-1 point); gradeⅡ(2-3 points); grade Ⅲ(4-6 points); and grade Ⅳ(7-9 points). After one week of bidirectional traction of the skull, CT scan was performed while maintaining the traction. The atlantodens interval(ADI) and vertical distance of dens to Chamberlain line(VDDC) before and after traction were measured, and the vertical reduction rate, horizontal reduction rate, and overall reduction rate of atlantoaxial dislocation were calculated. The difference in reduction rate of each group was compared, and the value of CT image scoring in judging the reduction difficulty of atlantoaxial dislocation was analyzed. Results: Of the 88 patients, 15 cases were of grade Ⅰ, 23 of grade Ⅱ, 38 of grade Ⅲ, and 12 of grade Ⅳ. The pre-traction ADI values of grades Ⅰ, Ⅱ and Ⅲ were 7.3±3.4mm, 8.1±3.7mm and 8.8±4.1mm, respectively, and after 1 week of bidirectional cervical traction, the ADI values were 1.5±1.5mm, 2.0±1.0mm and 5.7±1.7mm, respectively, and the statistical differences before and after traction were significant(P<0.05). The ADI values in group Ⅳ before and after traction were 8.9±3.9mm and 6.8±3.6mm respectively, there was no statistically significant difference(P>0.05). The pre-traction VDDC values of grades Ⅰ, Ⅱ, Ⅲ and Ⅳ were 11.9±3.9mm, 12.2±3.6mm, 13.6±3.8mm and 12.3±3.2mm, respectively, and the VDDC values after bidirectional cervical traction were 0.8±0.5mm, 3.1±1.1mm, 5.9±1.5mm and 8.2±2.0mm, respectively, and the statistical differences before and after traction were significant(P<0.05). The overall reduction rates were (86.4±12.0)%, (67.6±8.0)%, (45.9±9.0)%, and (28.4±13.0)% after one week of bi-directional traction of the skull, and the statistical differences between groups were significant(P<0.05). Conclusions: The quantitative scoring method using CT images can help judge the difficulty of atlantoaxial reduction and provide a reference for surgical decision-making.