Department of Pediatric Neurosurgery, University of California, Davis, Regional Center of Pediatric Neurosurgery, Kaiser Foundation Hospitals of Northern California, Oakland, California, USA.
Neurosurgery. 2010 Mar;66(3 Suppl):161-83. doi: 10.1227/01.NEU.0000365800.94865.D4.
Atlantoaxial rotatory fixation (AARF) remains a recondite entity. Our normative study using CT motion analysis shows that there is a high degree of concordance for rotational behavior of C1 and C2 in children 0 to 18 years. C1 always crosses C2 at or near 0 degree. The predictable relationship between C1 and C2 is depicted by 3 distinct regions on the motion curve: when C1 rotates from 0 to 23 degrees, it moves alone while C2 remains stationary at 0 (the single-motion phase). When C1 rotates from 24 to 65 degrees, C1 and C2 move together (the double-motion phase), but C1 always moves faster as C2 is being pulled by yoking ligaments. From 65 degrees onward, C1 and C2 move in unison (the unison-motion phase) with a fixed, maximal separation angle of approximately 43 degrees, the head rotation being carried exclusively by the subaxial segments. Because of this high concordance among patients and a relatively narrow variance from the mean, the physiological composite motion curve can be used as a normal template for the diagnosis and classification of AARF.
Using a 3-position CT protocol to obtain the diagnostic motion curve, we identified 3 distinct types of AARF. Type I AARF patients show essentially unaltered ("locked") C1-C2 coupling regardless of corrective counterrotation, with curves that are horizontal lines in the upper 2 quadrants of the template. Type II AARF patients show reduction of the C1-C2 separation angle with forced correction, but C1 cannot be made to cross C2. Their curves slope downward from the right to left upper quadrants but never traverse the x axis. Type III AARF patients show C1-C2 crossover but only when the head is cranked far to the opposite side. Their motion curves traverse the x axis far left of 0 degree (C1 < -20). Thus, type I, II, and III AARF are in descending degrees of pathological stickiness. A fourth group of patients showing motion curve features between normal and type III AARF are designated as belonging to a diagnostic gray zone (DGZ). The AARF patients are further classified as acute if treatment is started less than 1 month from the onset of symptoms, as subacute if the delay in treatment is 1 to 3 months, and chronic if treatment delay exceeds 3 months. The treatment protocol for AARF consists of reduction using either halter or caliper traction and then immobilization with brace or halo, depending on the AARF type and chronicity. Recurrent slippage and irreducibility are treated with C1-C2 fusion.
The treatment course and outcome of AARF are analyzed according to the AARF type and chronicity. The difficulty and duration of treatment, the number of recurrent slippage, the rate of irreducibility, the need for halo and fusion, and the percentage ultimately losing normal C1-C2 rotation are significantly greater in type I patients than type III patients, with type II patients somewhere in between. Likewise, all parameters are much worse in patients with any type of chronic AARF than acute AARF. The worse subgroup is chronic type I versus the best subgroup of acute type III. Recurrent AARF patients do much worse than nonrecurrent AARF patients. Recurrence is, in turn, adversely influenced by both the severity (type) and chronicity of AARF. The symptoms of most DGZ patients will resolve with analgesics, but a few remain symptomatic or deteriorate to true AARF requiring the full treatment.
Thus, children with painful torticollis should undergo the 3-position CT protocol not only to confirm the diagnosis of AARF but also to grade its severity. Closed reduction with traction should be instituted immediately to avoid the serious consequences of chronicity. Proper typing and reckoning of the pretreatment delay are requisites for selecting treatment modalities. Recurrent dislocation and incomplete reduction should be treated with posterior C1-C2 fusion in the best achievable alignment.
寰枢关节旋转固定（AARF）仍然是一个深奥的实体。我们使用 CT 运动分析的规范研究表明，0 至 18 岁儿童的 C1 和 C2 的旋转行为具有高度的一致性。C1 总是在 0 度或接近 0 度处越过 C2。C1 和 C2 之间的可预测关系在运动曲线上描绘为 3 个不同区域：当 C1 从 0 度旋转到 23 度时，它独自移动，而 C2 保持在 0 度静止（单动相位）。当 C1 从 24 度旋转到 65 度时，C1 和 C2 一起移动（双动相位），但由于约束韧带的拉动，C1 总是移动得更快。从 65 度开始，C1 和 C2 以一致的方式移动（一致运动阶段），具有大约 43 度的固定最大分离角度，头部旋转完全由下轴段承载。由于患者之间存在这种高度一致性，以及与平均值相比相对较窄的差异，生理复合运动曲线可以用作 AARF 诊断和分类的正常模板。
使用 3 位 CT 方案获得诊断运动曲线，我们确定了 3 种不同类型的 AARF。I 型 AARF 患者的 C1-C2 连接基本上没有改变（“锁定”），无论纠正反向旋转如何，其曲线在模板的上 2 象限中为水平线。II 型 AARF 患者在强制矫正时会减少 C1-C2 分离角度，但不能使 C1 越过 C2。他们的曲线从右到左上象限向下倾斜，但从未穿过 x 轴。III 型 AARF 患者仅在头部向相反侧转动到很远的位置时才会发生 C1-C2 交叉。他们的运动曲线穿过 x 轴，位于 0 度的左侧很远（C1 < -20）。因此，I 型、II 型和 III 型 AARF 按病理粘性程度降序排列。运动曲线特征介于正常和 III 型 AARF 之间的第四组患者被指定为属于诊断灰色区域（DGZ）。AARF 患者如果在症状发作后 1 个月内开始治疗，则归类为急性，如果治疗延迟为 1 至 3 个月，则归类为亚急性，如果治疗延迟超过 3 个月，则归类为慢性。AARF 的治疗方案包括使用吊带或卡钳牵引进行复位，然后根据 AARF 类型和慢性程度使用支具或头环进行固定。复发滑脱和不可复位性用 C1-C2 融合治疗。
根据 AARF 类型和慢性程度分析 AARF 的治疗过程和结果。I 型患者的治疗难度和持续时间、复发滑脱次数、不可复位率、需要 Halo 和融合的比例以及最终失去正常 C1-C2 旋转的比例明显大于 III 型患者，而 II 型患者则介于两者之间。同样，任何类型的慢性 AARF 患者的所有参数都比急性 AARF 患者差得多。慢性 I 型患者比急性 III 型患者的最差亚组差得更多。复发 AARF 患者的情况比非复发 AARF 患者差得多。复发反过来又受到 AARF 的严重程度（类型）和慢性程度的不利影响。大多数 DGZ 患者的症状会通过止痛药缓解，但少数患者仍有症状或恶化至需要进行完整治疗的真性 AARF。
因此，患有疼痛性斜颈的儿童应进行 3 位 CT 方案检查，不仅要确认 AARF 的诊断，还要评估其严重程度。应立即进行闭合复位牵引，以避免慢性的严重后果。正确的分型和治疗前延误时间的计算是选择治疗方法的必要条件。复发性脱位和不完全复位应采用后路 C1-C2 融合，以达到最佳的可实现对齐。
