计算机辅助设计寰枢椎椎弓根内固定数字化导向模板精确置钉

Computer aid designed digital targeting template of pedicle of vertebral arch for atlantoaxial nailing

目的 提高寰枢椎后路经椎弓根手术置钉的安全性和准确性.方法 可复性寰枢椎脱位及寰枢椎不稳13例,人院即行螺旋CT薄层扫描,取患者Dicom图像经计算机三维重建后进行后路椎弓根螺钉入路安全三维通道计算机辅助设计,建立椎弓根置钉导向管与三维互补模板.在激光快速成型机上按CAD设计图以聚苯乙烯为原料,利用逆向工程原理制作相应患者个体化的骨骼模型实物和手术辅助导板,外涂树脂固化剂,经高压消毒带进手术室,利用手术导向模板辅助寰枢椎后路椎弓根螺钉置入.结果 13例患者手术顺利,可复性寰枢椎脱位及寰枢椎不稳均解剖复位,固定良好.寰枢椎椎弓根螺钉置钉位置准确,未发生任何并发症.术中出血量平均50～100 ml,手术时间平均2.0～2.5 h,平均随访12个月,5例患儿的骨融合情况仍在随访中.结论 术中在数字化椎弓根内固定导向模板引导下置钉,提高了寰枢椎椎弓根内固定置钉的安全性和准确性.

Objective To improve the safety of atlantoaxial pedicle screw fixation. Methods The slice scanning CT images (Dicom format series) of 13 patients with atlantoaxial instability or reducible atlantoaxial dislocation were imputed into computer for three dimensional reconstruction, then the three dimensional computer virtual models was obtained. The safety passageway for atlantoaxial pedicle screw were designed, a guide tube was built around this passageway, a complementation template for posterior arch and spinous process, a connection rode to merge above two part, therefore, we get a digital targeting template of pedicle of vertebral arch for atlantoaxial nailing. This CAD template was input to Laser rapid prototyping machine with polystyrene as raw material. Based on reverse engineering theory, rapid prototyping entity of patient's skeleton model and atlantoaxial targeting template was gained which enwrapped a layer of resin firming agent and could resist high-temperature sterilization, these entities were used during operation, thus computer aided atlantoaxial pedicle screw fixation was performed. A routine posterior midline longitudinal skin incision was made. The atlas posterior arch, axis lamina of vertebral arch, axial lateral mass and spinous process were stripped carefully, in order to make room to place the surgical template. The screw was inserted along the guide tube. X-ray was repeated after the surgery, which showed excellent position of the internal fixation. Results The operations of 13 patients were completed smoothly with no complicating disease occurred. The atlantoaxial appears anatomical reduction, the internal fixation was placed well and strong e-nough. The average amount of bleeding during operation was 50-100 ml, Length of operation was 2.0-2.5 hour. A follow-up of 12 months averagely were carried out in all of the patients and 5 children were followed to observe bone fusion. Conclusion The safety and degree of accuracy of atlantoaxial pedicle screw fixation are improved by targeting template with the help of the proposed computer technique.