经口咽前路寰椎侧块置钉固定治疗合并寰枕融合畸形颅底凹陷症的临床疗效

Atlas lateral mass screw placement by transoral approach for basilar invagination complicated with occipital-atlas fusion

目的：探讨经口咽前路寰椎侧块置钉固定治疗合并寰枕融合畸形颅底凹陷症患者的可行性及临床疗效。方法：回顾性分析2009年3月~2011年10月我院收治的55例合并寰枕融合畸形的颅底凹陷症患者，行颅底和颈椎薄层CT扫描，冠状面和矢状面图像重建，同期我院影像数据库中５５例无枕颈畸形患者上颈椎ＣＴ资料作为对照。在PACS图像系统上测量寰椎侧块的前高Ha、后高Hp、外侧高度Ho、内侧高度Hi、侧块的矢径A和横径B，观察并测量硬腭后缘投影点到寰椎侧块下缘的高度d等参数。并以寰椎侧块中下1/3的水平线与内中1/3垂线的交点作为侧块螺钉的模拟进钉点，在PACS图像工作站上寻找最合适的钉道方向，测量钉道的外倾角α和上倾角β，螺钉理论钉道长度L等。按照上述设计方案，所有患者接受了经口咽前路寰枢椎脱位松解复位，钢板内固定手术（TARP）。术后CT扫描观察钉道情况，测量螺钉的实际外倾角α2和上倾角β2，螺钉长度L2等，并与影像学测量数据对比。临床疗效采用JOA评分系统对患者术后3个月、6个月及12个月随访时脊髓功能进行评分，测量术前、术后脑干脊髓角评价脊髓压迫改善情况。结果：寰枕融合组寰椎切面的形态与对照组形状相似，测量寰椎侧块的横径为14.5±3.4mm，纵径为19.3±2.6mm，均小于对照组（P〈0.05）。侧块前、后、外、内高度均小于对照组，其中后高差别尤为明显（P〈0.05）。寰枕融合组的硬腭投影点明显偏下，投影点与侧块下缘的距离均值为4.7±1.7mm，明显小于对照组的17.6±2.4mm（P〈0.05）。该组病例手术顺利，共置入寰椎侧块螺钉110枚，其中2枚螺钉偏外指向椎动脉孔，3枚螺钉偏内部分穿破侧块内侧缘，并呈切线进入椎管内，但未引起神经症状，其余均位于侧块内。术后患者肢体麻木、肌肉无力等症状均有明显改善，JOA评分术前8.1±1.6分，术后3个月复查时恢复至15.9±0.9分（P〈0.05），末次随访时为16.0±0.8分。脑干脊髓角由术前127°±11°改善至156°±14°（P〈0.05）。结论：经口咽前路侧块螺钉技术用于合并寰枕融合的颅底凹陷症是可行的，采用该技术的经口咽前路复位钢板治疗颅底凹陷症可获得良好疗效。

Objectives： To investigate the feasibility and outcome of atlas screw placement by transoral approach for basilar invagination complicated with occipital-atlas fusion. Methods： From March 2009 to October 2011, 55 patients suffering from basilar invagination complicated with occipital-atlas fusion were included in this study, and 55 other patients without C1 disorders were acted as control. The thin slice CT scan from the skull to cervical was performed, then the sagittal and coronal image was reconstructed. All information was transformed into the PACS system, and the anterior, posterior, inner and outer height of atlas （Ha, Hp, Hi, Ho）, width and length of atlas（A, B）, the distance from the projection of patella to the lower rim of atlas（d） were measured respectively. The entry point for screw placement was decided on the cross point between the inferior 1/3 line and outer 1/3 line of lateral mass. The trajectory of screw weas designed on PACS system, then the extroversion angle αand supratroversion angle β and length （L） for screw path were measured respectively. All 55 patients underwent transoral atlas-axis release, reduction and fixation surgery （TARP）, and the actual extroversion angle α2 and supratroversion angle β2 as well as real screw length （L2） were measured on CT image after operation. The spinal function was evaluated by JOA score at 3rd, 6th, and 12th months of follow-up, and the the cervical medullary angle was used to evaluate the decompression. Results： The occipital atlas fusion group had similar cross-sectional shape of C1, and the width was 14.5±3.4mm, length was 19.3±2.6mm, both less than control group（P〈0.05）; and the values of Ha, Hp,Hi, Ho were all less than control group（P〈0.05）. The distance from the projection of bone patella to the lower rim of lateral mass was 4.7±1.7mm, less than control group（17.6±2.4mm, P〈0.05）. A total of 110 screws were placed into C1 lateral mass succesfully, except for 2 screws violating the vertebral artery forman and 3 screws penetrating the inner wall of lateral mass. Limbs numbness, weakness improved significantly after operation. The JOA scores improved from 8.1±1.6 of pre-operation to 15.9±0.9 （P〈0.05） 3 months of post-operation, and to 16.0±0.8 at final follow-up （P〈0.05）. The cervical medullary angle improved from 127°±11° to 156°±14°（P〈0.05）. Conclusions： Transoral anterior atlas screw placement for basilar invagination complicated with occipital-atlas fusion is reliable and applicable.