J Neurosurg Spine. 2023 May 5;39(2):175-186. doi: 10.3171/2023.3.SPINE221364. Print 2023 Aug 1.
The objective was to describe an intraoperative method that accurately predicts postoperative coronal alignment for up to 2 years of follow-up. The authors hypothesized that the intraoperative coronal target for adult spinal deformity (ASD) surgery should account for lower-extremity parameters, including pelvic obliquity (PO), leg length discrepancy (LLD), lower-extremity mechanical axis difference (MAD), and asymmetrical knee bending.
Two lines were drawn on intraoperative prone radiographs: the central sacral pelvic line (CSPL) (the line bisecting the sacrum and perpendicular to the line touching the acetabular sourcil of both hips) and the intraoperative central sacral vertical line (iCSVL) (which is drawn relative to CSPL based on the preoperative erect PO). The distance from the C7 spinous process to CSPL (C7-CSPL) and the distance from the C7 spinous process to iCSVL (iCVA) were compared with immediate and 2-year postoperative CVA. To account for LLD and preoperative lower-extremity compensation, patients were categorized into four preoperative groups: type 1, no LLD (< 1 cm) and no lower-extremity compensation; type 2, no LLD with lower-extremity compensation (PO > 1°, asymmetrical knee bending, and MAD > 2°); type 3, LLD and no lower-extremity compensation; and type 4, LLD with lower-extremity compensation (asymmetrical knee bending and MAD > 4°). A retrospective review of a consecutively collected cohort with ASD who underwent minimum 6-level fusion with pelvic fixation was performed for validation.
In total, 108 patients (mean ± SD age 57.7 ± 13.7 years, 14.0 ± 3.9 levels fused) were reviewed. Mean preoperative/2-year postoperative CVA was 5.0 ± 2.0/2.2 ± 1.8 cm. For patients with type 1, both C7-CSPL and iCVA had similar error margins for immediate postoperative CVA (0.5 ± 0.6 vs 0.5 ± 0.6 cm, p = 0.900) and 2-year postoperative CVA (0.3 ± 0.4 vs 0.4 ± 0.5 cm, p = 0.185). For patients with type 2, C7-CSPL was more accurate for immediate postoperative CVA (0.8 ± 1.2 vs 1.7 ± 1.8 cm, p = 0.006) and 2-year postoperative CVA (0.7 ± 1.1 vs 2.1 ± 2.2 cm, p < 0.001). For patients with type 3, iCVA was more accurate for immediate postoperative CVA (0.3 ± 0.4 vs 1.7 ± 0.8 cm, p < 0.001) and 2-year postoperative CVA (0.3 ± 0.2 vs 1.9 ± 0.8 cm, p < 0.001). For patients with type 4, iCVA was more accurate for immediate postoperative CVA (0.6 ± 0.7 vs 3.0 ± 1.3 cm, p < 0.001) and 2-year postoperative CVA (0.5 ± 0.6 vs 3.0 ± 1.6 cm, p < 0.001).
This system, which accounted for lower-extremity factors, provided an intraoperative guide to determine both immediate and 2-year postoperative CVA with high accuracy. For patients with type 1 and 2 (no LLD, with or without lower-extremity compensation), C7-intraoperative CSPL accurately predicted postoperative CVA up to 2-year follow-up (mean error 0.5 cm). For patients with type 3 and 4 (LLD, with or without lower-extremity compensation), iCVA accurately predicted postoperative CVA up to 2-year follow-up (mean error 0.4 cm).
描述一种能够准确预测术后冠状面对线长达 2 年随访的术中方法。作者假设成人脊柱畸形（ASD）手术的术中冠状面目标应考虑下肢参数，包括骨盆倾斜（PO）、下肢长度差异（LLD）、下肢机械轴差（MAD）和不对称性膝弯曲。
在术中俯卧位 X 线片上绘制两条线：中骶骨骨盆线（CSPL）（将骶骨二等分并垂直于触及双侧髋臼的坐骨线）和术中中骶骨垂直线（iCSVL）（相对于 CSPL 根据术前直立 PO 绘制）。比较 C7 棘突至 CSPL 的距离（C7-CSPL）和 C7 棘突至 iCSVL 的距离（iCVA）与即刻和 2 年术后 CVA 的差异。为了考虑 LLD 和术前下肢补偿，将患者分为以下四个术前组：1 型，无 LLD（<1cm）和无下肢补偿；2 型，无 LLD 但有下肢补偿（PO>1°，不对称性膝弯曲，MAD>2°）；3 型，有 LLD 但无下肢补偿；4 型，有 LLD 但有下肢补偿（不对称性膝弯曲和 MAD>4°）。对一组连续收集的 ASD 患者进行回顾性验证，这些患者接受了至少 6 级融合和骨盆固定。
共纳入 108 例患者（平均年龄 57.7±13.7 岁，融合 14.0±3.9 个节段）。术前/2 年术后平均 CVA 分别为 5.0±2.0/2.2±1.8cm。对于 1 型患者，C7-CSPL 和 iCVA 对即刻术后 CVA（0.5±0.6 vs 0.5±0.6cm，p=0.900）和 2 年术后 CVA（0.3±0.4 vs 0.4±0.5cm，p=0.185）的误差边界相似。对于 2 型患者，C7-CSPL 对即刻术后 CVA（0.8±1.2 vs 1.7±1.8cm，p=0.006）和 2 年术后 CVA（0.7±1.1 vs 2.1±2.2cm，p<0.001）更准确。对于 3 型患者，iCVA 对即刻术后 CVA（0.3±0.4 vs 1.7±0.8cm，p<0.001）和 2 年术后 CVA（0.3±0.2 vs 1.9±0.8cm，p<0.001）更准确。对于 4 型患者，iCVA 对即刻术后 CVA（0.6±0.7 vs 3.0±1.3cm，p<0.001）和 2 年术后 CVA（0.5±0.6 vs 3.0±1.6cm，p<0.001）更准确。
该系统考虑了下肢因素，为确定术后即刻和 2 年随访的冠状面 CVA 提供了高精度的术中指导。对于 1 型和 2 型患者（无 LLD，有或无下肢补偿），C7-术中 CSPL 可准确预测术后 CVA 长达 2 年随访（平均误差 0.5cm）。对于 3 型和 4 型患者（有 LLD，有或无下肢补偿），iCVA 可准确预测术后 CVA 长达 2 年随访（平均误差 0.4cm）。
