后路寰枢椎椎弓根钉固定技术治疗寰枢椎不稳或脱位的临床疗效及影像学评估

The treatment of posterior arthrodesis with pedicle screw fixation for the atlantoaxial instability or dislocation

目的：探讨后路寰枢椎椎弓根钉固定技术治疗寰枢椎不稳或脱位的临床疗效及影像学评估。方法：2005年2月至2009年6月,采用后路寰枢椎椎弓根钉固定技术治疗寰枢椎不稳或脱位24例,其中齿状突陈旧性骨折7例,先天性游离齿突4例,新鲜齿突骨折9例（AndersonⅡC型）,寰椎横韧带损伤4例。术前CT及三维重建评估寰枢椎椎弓根螺钉的进钉点、进钉方向等参数。枢椎椎弓根螺钉进钉点为枢椎下关节突中点,探及椎弓根上内侧缘,钉道内侧倾约25°,头侧倾约25°。寰椎椎弓根螺钉进钉点为枢椎椎弓根螺钉进钉点外侧1 mm纵垂线与其后弓下缘以上2 mm的交点处,钉道内侧倾约5°,头侧倾约5°。螺钉直径3.5 mm/4.0 mm,寰椎椎弓根螺钉长22～30 mm,枢椎椎弓根螺钉长22～28 mm。术后摄X线、CT及三维重建评估椎弓根螺钉的情况。结果：24例患者共置入寰、枢椎椎弓根螺钉95枚,1枚寰椎椎弓根螺钉植入困难,改用椎板钩。术后CT扫描发现1枚螺钉穿入寰椎椎管,1枚螺钉穿入枢椎横突孔,患者均未发生脊髓和椎动脉损伤。随访时间6～29个月,平均16个月。患者神经系统症状有不同程度改善,新鲜齿突骨折均骨性愈合,植骨于术后3~6个月骨性融合;无内固定物松动、断裂。结论：后路寰枢椎椎弓根钉固定技术是治疗寰枢椎脱位或不稳的有效方法,术前应充分评估患者寰枢椎椎弓根的影像学特点及植入椎弓根螺钉的风险。

Objective：To explore the clinical efficacy and imaging assessment of posterior arthrodesis with pedicle screw fixation in the treatment of atlantoaxial instability or dislocation. Methods：24 cases of atlantoaxial instability or dislocation were treated with posterior atlantoaxial pedicle screw fixation from February 2005 to June 2009,of these cases there were 7 cases of odontoid process old fracture,4 cases of congenital odontoid process freeing,9 cases of odontoid process type ⅡC fresh fracture and 4 cases of atlas transverse ligament injury. The parameters were assessed by preoperative CT and three-dimensional reconstruction such the entry point and angle of atlantoaxial pedicle screws. The entry point of C 2 pedicle screw was located in the mid-point of inferior articular process of axis,using the medial border of the C 2 lamina as a landmark,25° in a medial inclination and 25° in a cephalad direction.The entry point of C 1 was placed in longitudinal vertical outside the entry point of C 2 pedicle screw about 1mm and the point of intersection above 2 mm inferior border of posterior arch,5° in a medial inclination and 5° in a cephalad direction.The diameter of screws was 3.5/4.0 mm,and the screw length of C 1 and C 2 pedicle screws were 22～30 mm and 22～28 mm. Postoperatively,the placement of the inserted screws were evaluated by means of X-ray,CT-scan and three-dimensional reconstruction. Results：A total of 95 screws were successfully placed in atlas and axis. Laminar hook was implanted instead of one atlas pedicle screw because of implant failure intraoperative. Postoperative CT scan,one screw perforated the atlas spinal canal ,one penetrated the axial transverse foramen,without any clinical response. There were no neural or vascular injury was observed. All patients were followed up from 6 to 29 months,averaged 16 months.The clinical symptom was improved in some extend. Bony fusion was observed in all 24 cases within 3 to 6 months without complications of internal fixation failure and loose. Conclusion：The transpedicular fixation is an effective method for the treatment of atlantoaxial instability or dislocation,and it is necessary to fully assess imaging characteristics of atlantoaxial pedicle and risks of atlantoaxial pedicle screw implantation before surgery.