颅底凹陷症合并寰枢椎脱位患者枕颈角与下颈椎曲度的关系

Relationship between occiptocervical angle and subaxial cervical alignment in patients with basilar invagination and atlantoaxial dislocation

目的:评估颅底凹陷症(basilar invagination,BI)合并寰枢椎脱位(atlantoaxial dislocation,AAD)患者枕颈角(O-C2角)与下颈椎曲度(C2-7 Cobb角)之间的关系。方法:回顾性分析2009年1月~2013年6月21例于我院因BI合并AAD行后路复位枕颈融合术患者的临床资料。21例患者中男12例,女9例;年龄21~65岁(41.6±10.7岁);病程4个月~18年(4.3±3.9年)。于手术前和术后末次随访时在颈椎中立位侧位X线片上测量O-C2及C2-7 Cobb角(C2-7角),并计算O-C2角及C2-7角的变化量dO-C2角和dC2-7角,前凸为"+"值,后凸为值。根据O-C2角的大小,将21例患者术前和末次随访时分为10°≤O-C2角≤20°组、O-C2角<10°组及O-C2角>20°组。观测手术前后不同O-C2角组C2-7角的差异,分析手术前后O-C2角与C2-7角的相关性。结果:21例患者中,12例患者固定节段为C0-C3,9例患者为C0-C4。随访时间为10~32个月(18.3±6.6个月)。术后末次随访时O-C2角较术前平均增大6.3°,C2-7角较术前平均减小6°,手术前后两指标比较均存在显著性差异(P<0.05)。术前6例(28.6%)患者O-C2角在10°~20°间,12例(57.1%)<10°,3例(14.3%)>20°。OC2角<10°组C2-7角显著大于O-C2角10°~20°组及>20°组(P<0.05),O-C2角10°~20°组与>20°组比较无显著性差异(P>0.05)。末次随访时10例(47.6%)患者O-C2角在10°~20°间,4例(19.0%)>20°,7例(33.4%)<10°,O-C2角>20°组C2-7角显著小于O-C2角10°~20°组及<10°组(P<0.05),O-C2角10°~20°组与<10°组比较无显著性差异(P>0.05)。术前及术后末次随访时O-C2角与C2-7角均存在显著性负相关(术前r=-0.732,P<0.05;术后r=-0.603,P<0.05);d0-C2角及dC2-7角亦存在显著性负相关(r=-0.721,P<0.05)。结论:BI合并AAD患者枕颈角与下颈椎曲度关系密切,行后路复位枕颈融合术时需监测枕颈角的固定角度,若枕颈角过大有可能导致术后下颈椎曲度出现代偿性减小。

Objectives： To measure the occipitoaxial angle and subaxial alignment in the patients with basilar invagination（BI） and atlantoaxial disloeation（AAD）, and to elucidate the relationship between occipitoaxial angle and subaxial cervical alignment. Methods： From January 2009 to June 2013, the clinical data of 21 patients who had BI with AAD undergoing surgery at our institution were retrospectively analyzed. The patients consisted of 12 men and 9 women, and ages ranged from 21 to 65 years （mean, 41.6±10.7 years）. The duration of symptoms ranged from 4 months to 18 years（mean, 4.3±3.9 years）. O-C2 angle and C2-7 Cobb angle（C2-7 angle） were measured before surgery and at the last follow-up in plain lateral cervical X-ray, and the changes of O-C2（dO-C2） angle and C2-7（dC2-7） angle were also calculated. A plus angle indicated lordosis between oceiput and C2, and a minus angle indicated the kyphosis between occiput and C2. According to the value of O-C2 angle, all the 21 patients were divided into 10°≤O-C2≤20° group, 〈10° group and 〉20° group. The difference of C2-7 angle among these three groups, the associations between O-C2 angle and C2-7 angle before surgery and at the last follow-up were studied. Results： Among these 21 patients, C0-C3 fixation was performed in 12 patients, and C0-V4 fixation was performed in 9 patients. The mean follow-up in these 21 patients was 18.3 months with a range of 10 to 32 months. Before and after surgery, the mean change of O-C2 angle was 6.3°, and the mean change of C2-7 angle was -6°. There were significant differences between preoperative and postoperative O-C2 angle and C2-7 angle （P〈0.05）. Before surgery, 6（28.6%） patients were in 10°≤O-C2 angle≤20° group, and 12（57.1%） patients in 〈10° group, and 3 （14.3%） patients in 〉20° group. Among these groups, C2-7 angle in O-C2 angle 〈10° group was significantly larger than that in 10°≤O-C2 angle≤20° group and O-C2 angle 〉20° group（P〈0.05）. There was no difference of preoperative C2-7 angle between 10°≤O-C2 angle≤20° group and O-C2 angle 〉20° group （P〉0.05）. At the last follow-up, 10（47.6%） patients were in 10°≤O-C2 angle≤20° group, and 4（19.0%） patients in 〉20° group, and 7（33.4%） patients in 〈10° group. Among these groups, C2-7 angle in O-C2 angle 〉20° group was significantly smaller than that in 10°≤O-C2 angle≤20° group and 〈10° group（P〈0.05）. There was no significant difference between the 10°≤O-C2 angle≤20° group and 〈10° group（P〉0.05）. There was a significant negative correlation between O-C2 angle and C2-7 angle before and after surgery （r=-0.732 and r=-0.603, P〈0.05）. The dO-C2 angle was also negatively associated with the dC2-7 angle（r=-0.721, P〈 0.05）. Conclusions： There is significantly correlation between O-C2 angle and C2-7 angle in patients with BI and AD. During occiptocervical fusion surgery, attention should be paid to the fixed O-C2 angle. Subaxial alignment will show compensatory decrease if O-C2 angle is too large.