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目的:探讨基于术前CT三维重建模拟复位斜坡枢椎角（clivus-axial angle, CAA）并评估钉道治疗可复位型上颈椎畸形不稳定的可行性。方法:回顾性分析2014年1月至2019年9月52例上颈椎畸形不稳定患者资料，男28例，女24例；年龄18~64岁，平均46.7岁。术前将颈椎CT扫描数据（DICOM格式）导入Mimics15.0软件行三维重建，以通过术前颈椎过伸侧位X线片获得的CAA值作为术中复位CAA目标区间的上限，以CAA正常值140°作为下限，评估是否存在置入Magerl螺钉钉道的解剖条件，以钉道存在时的CAA值作为术中复位角度。比较CAA的术前、术后CT测量值及模拟目标值间的差异。按Gertzbein-Robbins分级评价置钉准确性，同时比较术前、术后颈椎功能障碍指数（neck disability index, NDI）及Nurick评分差异。结果:52例患者中35例经术前模拟评估存在可用钉道。以术中导航辅助下判断钉道为金标准，其中37例行Magerl螺钉固定（Magerl技术组），15例行钉棒系统固定（钉棒技术组）。Magerl技术组的模拟目标CAA值（150.1°±6.6°）与术后测量值（149.0°±6.5°）比较，差异无统计学意义（n t=1.194，n P=0.240）；术后测量值较术前（124.0°±8.9°）显著增加（n t=-13.499，n P<0.001）。钉棒技术组的模拟目标CAA值（150.4°±5.6°）与术后测量值（150.2°±6.1°）比较，差异无统计学意义（n t=0.319，n P=0.754）；术后测量值较术前（121.9°±8.3°）显著增加（n t=-12.431，n P<0.001)。52例患者均获得随访，随访时间（1.7±0.9）年（范围0.5~4年）。52例患者共置入106枚螺钉，其中Magerl技术组74枚，钉棒技术组32枚，根据Gertzbein-Robbins分级，A级88枚，B级15枚，临床可接受率为97.1%（103/106）。全部患者无一例发生椎动脉损伤、后组颅神经麻痹等并发症。术后NDI（9.7±6.4）和Nurick分级[（1.1±1.4）级]均较术前[27.4±8.7和（2.6±1.3）级]显著降低。n 结论:术前模拟判断可用钉道、提供术中复位的目标CAA值，并在计算机导航辅助下纠正CAA行单一后路融合手术治疗可复位型上颈椎畸形不稳定的方法安全可行。“,”Objective:To evaluate the feasibility of surgery for upper cervical spine anomaly instability achieved by readjusting the clivus-axial angle (CAA) and evaluating available screw trajectories based on preoperative virtual simulation reduction using 3D CT reconstruction.Methods:From January 2014 to September 2019, 52 patients (28 males, 24 females; mean age 46.7 years; range 18-64 years) with upper cervical spine anomalies were enrolled in a retrospective study. DICOM data of preoperative CT scanning of cervical spine were imported into Mimics 15.0 to reconstruct the 3D model of atlantoaxial joint. The target range of CAA was set with the value measured in fusing images of extension view of cervical spine as the upper bound; and 140°, the lower limit of normal CAA range, was set as the lower bound. The trajectories of screws were sought within the target range of CAA. The exact CAA value of the available trajectories was set as the target angle of intraoperative reduction . The preoperative, postoperative and simulated target CAA values were compared. The accuracy of screw placement was evaluated according to the Gertzbein-Robbins scale. The pre- and postoperative neck disability index (NDI) and Nurick scale were also compared.Results:Among 52 patients, available screw trajectories existed in 35 patients. With the validation under computer-assisted navigation as the gold standard, 37 patients underwent Magerl screws fixation (Magerl group) while the other 15 patients underwent screw-rods fixation (screw-rods group). In Magerl group, no significant difference was found between simulated target CAA values (150.1°±6.6°) and postoperative CAA values (149.0°±6.5°)(n t=1.194, n P=0.240); postoperative CAA values were significantly larger than preoperative CAA values (124.0°±8.9°)(n t=-13.499, n P< 0.001). In screw-rods group, no significant difference was found between simulated target CAA values (150.4°±5.6°) and postoperative CAA values (150.2°±6.1°) (n t=0.319, n P=0.754); postoperative CAA values were also significantly larger than preoperative CAA values (121.9°±8.3°)(n t=-12.431, n P< 0.001). Follow-up data were obtained in all 52 patients, with a mean follow-up time of 1.7±0.9 years (range, 0.5-4 years). A total of 106 screws were placed into 52 patients, including 74 in Magerl group and 32 in screw-rods group. According to the Gertzbein-Robbins scale, 88 and 15 were classified into grade A and B respectively; and 97.1% (103/106) of screws were acceptable. No severe complications such as vertebral artery injury and low cranial nerve palsy occurred. The postoperative NDI (9.7±6.4n vs. 27.4±8.7) and Nurick scale (1.1±1.4 n vs. 2.6±1.3) decreased significantly compared to preoperative ones, respectively.n Conclusion:Preoperative virtual simulation can evaluate available screw trajectories and provide the target CAA values for guidance of intraoperative reduction. Based on this, readjusting the CAA under computer-assisted navigation were safe and feasible, and warranted the possibility of a single posterior reduction and fusion approach for reducible upper cervical anomaly instability.