J Neurosurg Spine. 2019 Mar 15;31(1):27-34. doi: 10.3171/2018.12.SPINE18752. Print 2019 Jul 1.
Relocation of the apex is often found in patients with ankylosing spondylitis (AS)-associated thoracolumbar/lumbar kyphosis after corrective surgery. This study evaluates the influence of different postoperative apex locations on surgical and clinical outcomes of osteotomy for patients with AS and thoracolumbar kyphosis.
Sixty-two patients with a mean age of 34.6 ± 9.7 years (range 17-59 years) and a minimum of 2 years of follow-up, who underwent 1-level lumbar pedicle subtraction osteotomy for AS-related thoracolumbar kyphosis, were enrolled in the study, as well as 62 age-matched healthy individuals. Patients were divided into 2 groups according to the postoperative location of the apex (group 1, T8 or above; group 2, T9 or below). Demographic data, radiographic measurements (including 3 postoperative apex-related parameters), and clinical outcomes were compared between the 2 groups preoperatively, postoperatively, and at the last follow-up. Furthermore, a subgroup analysis was performed among patients with a postoperative apex located at T6-11 and postoperatively the entire AS cohort was compared with normal controls regarding the apex location of the thoracic spine.
In the majority of the enrolled patients, the apex location changed from T12-L2 preoperatively to T6-9 postoperatively. The sagittal vertical axis (SVA) differed significantly both postoperatively (25.7 vs 59.0 mm, p = 0.001) and at the last follow-up (34.6 vs 59.9 mm, p = 0.003) between the 2 groups, and the patients in group 1 had significantly smaller horizontal distance between the C7-vertical line and the apex (DCA) than the patients in group 2 (67.5 vs 103.7 mm, p = 0.001). Subgroup analysis demonstrated similar results, showing that the patients with a postoperative apex located at T8 or above had an average SVA < 47 mm. Notably, a significant correlation was found between postoperative SVA and DCA (r = 0.642, p = 0.001). Patients who underwent an osteotomy at L3 had limited apex relocation but larger SVA correction than those at L1 or L2. However, no significant difference was found in health-related quality of life between the 2 groups.
AS patients with an apex located at T8 or above after surgery tended to have better SVA correction (within 47 mm) than those who had a more caudally located apical vertebra. For ideal postoperative apex relocation, a higher (closer to or at the preoperative apex) level of osteotomy is more likely to obtain the surgical goal.
强直性脊柱炎（AS）相关胸腰椎/腰椎后凸畸形患者行矫形手术后常出现顶椎移位。本研究评估了不同术后顶椎位置对 AS 伴胸腰椎后凸畸形患者行截骨术的手术和临床结果的影响。
纳入了 62 例年龄 34.6±9.7 岁（17-59 岁）的患者，均接受 1 节段腰椎经椎弓根截骨术治疗 AS 相关胸腰椎后凸畸形，随访时间至少 2 年。同时纳入了 62 例年龄匹配的健康对照者。根据术后顶椎位置（A 组：T8 或以上；B 组：T9 或以下）将患者分为 2 组。比较 2 组患者术前、术后及末次随访时的一般资料、影像学测量（包括术后 3 项顶椎相关参数）和临床结果。此外，对术后顶椎位于 T6-11 的患者进行亚组分析，并比较术后整个 AS 队列与正常对照组的胸椎顶椎位置。
多数患者术前顶椎位于 T12-L2，术后位于 T6-9。2 组患者术后（25.7 比 59.0mm，p=0.001）和末次随访时（34.6 比 59.9mm，p=0.003）的矢状垂直轴（SVA）均有显著差异，且 A 组患者 C7 铅垂线与顶椎的水平距离（DCA）显著小于 B 组（67.5 比 103.7mm，p=0.001）。亚组分析显示了相似的结果，即术后顶椎位于 T8 或以上的患者的平均 SVA<47mm。值得注意的是，术后 SVA 与 DCA 呈显著正相关（r=0.642，p=0.001）。行 L3 截骨术的患者顶椎移位有限，但 SVA 矫正更大，而行 L1 或 L2 截骨术的患者则相反。然而，2 组患者的健康相关生活质量无显著差异。
术后顶椎位于 T8 或以上的 AS 患者的 SVA 矫正（<47mm）优于顶椎位置更低的患者。为获得理想的术后顶椎移位，较高（接近或位于术前顶椎）的截骨水平更有可能实现手术目标。
