BACKGROUND Our understanding of the relationship between sagittal alignment and mechanical complications is evolving. In normal spines, the L1-pelvic angle (L1PA) accounts for the magnitude and distribution of lordosis and is strongly associated with pelvic incidence (PI), and the T4-pelvic angle (T4PA) is within 4° of the L1PA. We aimed to examine the clinical implications of realignment to a normal L1PA and T4-L1PA mismatch. METHODS A prospective multicenter adult spinal deformity registry was queried for patients who underwent fixation from the T1-T5 region to the sacrum and had 2-year radiographic follow-up. Normal sagittal alignment was defined as previously described for normal spines: L1PA = PI × 0.5 - 21°, and T4-L1PA mismatch = 0°. Mechanical failure was defined as severe proximal junctional kyphosis (PJK), displaced rod fracture, or reoperation for junctional failure, pseudarthrosis, or rod fracture within 2 years. Multivariable nonlinear logistic regression was used to define target ranges for L1PA and T4-L1PA mismatch that minimized the risk of mechanical failure. The relationship between changes in T4PA and changes in global sagittal alignment according to the C2-pelvic angle (C2PA) was determined using linear regression. Lastly, multivariable regression was used to assess associations between initial postoperative C2PA and patient-reported outcomes at 1 year, adjusting for preoperative scores and age. RESULTS The median age of the 247 included patients was 64 years (interquartile range, 57 to 69 years), and 202 (82%) were female. Deviation from a normal L1PA or T4-L1PA mismatch in either direction was associated with a significantly higher risk of mechanical failure, independent of age. Risk was minimized with an L1PA of PI × 0.5 - (19° ± 2°) and T4-L1PA mismatch between -3° and +1°. Changes in T4PA and in C2PA at the time of final follow-up were strongly associated (r2 = 0.96). Higher postoperative C2PA was independently associated with more disability, more pain, and worse self-image at 1 year. CONCLUSIONS We defined sagittal alignment targets using L1PA (relative to PI) and the T4-L1PA mismatch, which are both directly modifiable during surgery. In patients undergoing long fusion to the sacrum, realignment based on these targets may lead to fewer mechanical failures. LEVEL OF EVIDENCE Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

中文翻译：

---

T4-L1-髋轴：长结构成人脊柱畸形手术中的矢状脊柱重新调整目标：早期影响。


背景技术我们对矢状排列与机械并发症之间关系的理解正在不断发展。在正常脊柱中，L1 骨盆角 (L1PA) 决定了脊柱前凸的大小和分布，并且与骨盆倾角 (PI) 密切相关，而 T4 骨盆角 (T4PA) 与 L1PA 的偏差在 4° 以内。我们的目的是检查正常 L1PA 和 T4-L1PA 不匹配重新排列的临床意义。方法 前瞻性多中心成人脊柱畸形登记处查询接受 T1-T5 区域至骶骨固定并进行 2 年影像学随访的患者。正常矢状排列的定义如之前针对正常脊柱所述：L1PA = PI × 0.5 - 21°，T4-L1PA 失配 = 0°。机械故障定义为严重的近端交界后凸 (PJK)、移位的杆骨折，或 2 年内因交界故障、假关节或杆骨折再次手术。使用多变量非线性逻辑回归来定义 L1PA 和 T4-L1PA 不匹配的目标范围，从而最大限度地降低机械故障的风险。使用线性回归确定 T4PA 变化与根据 C2 骨盆角 (C2PA) 的整体矢状对齐变化之间的关系。最后，使用多变量回归评估术后初始 C2PA 与患者报告的 1 年结果之间的关联，并调整术前评分和年龄。结果 247 名患者的中位年龄为 64 岁（四分位数范围为 57 至 69 岁），其中 202 名（82%）为女性。任一方向偏离正常 L1PA 或 T4-L1PA 不匹配均与显着较高的机械故障风险相关，与年龄无关。 L1PA 为 PI × 0 时，风险降至最低。5 - (19° ± 2°) 和 T4-L1PA 在 -3° 和 +1° 之间失配。最终随访时 T4PA 和 C2PA 的变化密切相关 (r2 = 0.96)。较高的术后 C2PA 与 1 年时更多的残疾、更多的疼痛和更差的自我形象独立相关。结论 我们使用 L1PA（相对于 PI）和 T4-L1PA 不匹配定义了矢状对齐目标，这两者都可以在手术期间直接修改。在接受骶骨长融合的患者中，基于这些目标的重新对准可能会减少机械故障。证据级别 治疗级别 III。有关证据级别的完整描述，请参阅作者须知。