Pennington Zach, Mikula Anthony L, Hamouda Abdelrahman, Elsamadicy Aladine A, Grossbach Andrew J, Paganucci Gabriella L, Freedman Brett, Nassr Ahmad, Sebastian Arjun, Fogelson Jeremy L, Elder Benjamin D
1Department of Neurosurgery, Mayo Clinic, Rochester, Minnesota.
2Department of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut.
J Neurosurg Spine. 2025 Aug 8:1-10. doi: 10.3171/2025.5.SPINE25303.
Proximal junctional kyphosis (PJK) affects 5%-61% of patients following thoracolumbar fusion. Many patients are asymptomatic, but a plurality require surgical revision at a cost of $75,000 per case. This analysis sought to analyze the degree to which bone quality and paraspinal muscle sarcopenia influence PJK failure mode.
Patients undergoing thoracolumbar instrumented fusion with an upper instrumented vertebra (UIV) at the thoracolumbar junction (T10-L2) were identified and data were gathered on surgery, bone quality, pre- and postoperative sagittal alignment, and paraspinal muscle cross-sectional area (CSA). PJK was defined as a ≥ 10° increase in proximal junctional angle from the first postoperative radiograph. PJK was classified as discoligamentous failure (type 1), bone failure (type 2), or screw-bone interface failure (type 3) according to the Yagi-Boachie system. Bone quality was assessed by Hounsfield units (HUs) and the vertebral bone quality (VBQ) score at the UIV.
One hundred fifty patients were identified (median age 67 years, 53.3% female), 46 of whom experienced PJK (22 type 1, 13 type 2, 11 type 3). The median time to onset was most rapid for type 2 events (2.6 months). There were no differences between patients experiencing PJK versus controls regarding bone quality (HUs or VBQ score) or paraspinal muscle CSA on univariate comparison. However, subdivision by PJK type showed patients experiencing bone failure (type 2) PJK had significantly lower HUs at the UIV and UIV+1 relative to those experiencing type 1 PJK or no PJK (all p < 0.05). The VBQ score trended toward being significant, with a higher VBQ score (worse bone quality) in those suffering type 2 PJK, but did not reach statistical significance (p = 0.07). Patients experiencing discoligamentous failure PJK (type 1) had small multifidus CSA (390 mm2) relative to patients experiencing type 2 (516 mm2) or type 3 (440 mm2) PJK and patients who did not experience PJK (481 mm2), although the difference did not reach statistical significance. On time-to-event analysis, low HUs of the UIV/UIV+1 predicted type 2 (hazard ratio [HR] 0.81, 95% CI 0.70-0.93; p = 0.002) and type 2/3 PJK (HR 0.87, 95% CI 0.78-0.96; p = 0.006) but not type 1 PJK. Low UIV multifidus CSA trended toward being a significant predictor of type 1 PJK (HR 0.85, 95% CI 0.69-1.05; p < 0.10).
The combination of underlying bone quality and paraspinal musculature CSA at the UIV appeared to influence failure mode among patients who underwent lumbosacral instrumented fusion terminating at the thoracolumbar junction.
近端交界性后凸（PJK）影响5% - 61%的胸腰段融合术后患者。许多患者无症状，但多数患者需要手术翻修，每例费用达75,000美元。本分析旨在分析骨质量和椎旁肌少肌症对PJK失败模式的影响程度。
确定在胸腰段交界（T10 - L2）行上固定椎（UIV）的胸腰段器械融合术的患者，并收集手术、骨质量、术前和术后矢状面排列以及椎旁肌横截面积（CSA）的数据。PJK定义为术后第一张X线片近端交界角增加≥10°。根据矢木 - 博阿奇系统，PJK分为椎间盘韧带性失败（1型）、骨失败（2型）或螺钉 - 骨界面失败（3型）。通过豪斯菲尔德单位（HUs）和UIV处的椎体骨质量（VBQ）评分评估骨质量。
共确定150例患者（中位年龄67岁，53.3%为女性），其中46例发生PJK（22例为1型，13例为2型，11例为3型）。2型事件的中位发病时间最快（2.6个月）。单因素比较时，发生PJK的患者与对照组在骨质量（HUs或VBQ评分）或椎旁肌CSA方面无差异。然而，按PJK类型细分显示，发生骨失败（2型）PJK的患者在UIV和UIV + 1处的HUs显著低于发生1型PJK或未发生PJK的患者（所有p < 0.05）。VBQ评分有显著趋势，2型PJK患者的VBQ评分较高（骨质量较差），但未达到统计学意义（p = 0.07）。发生椎间盘韧带性失败PJK（1型）的患者相对于发生2型（516 mm²）或3型（440 mm²）PJK的患者以及未发生PJK的患者（481 mm²），多裂肌CSA较小，尽管差异未达到统计学意义。在事件发生时间分析中，UIV/UIV + 1处的低HUs预测2型（风险比[HR] 0.81，95%可信区间0.70 - 0.93；p = 0.002）和2/3型PJK（HR 0.87，95%可信区间0.78 - 0.96；p = 0.006），但不能预测1型PJK。UIV多裂肌CSA低有成为1型PJK显著预测因素的趋势（HR 0.85，95%可信区间0.69 - 1.05；p < 0.10）。
UIV处潜在的骨质量和椎旁肌组织CSA的组合似乎会影响在胸腰段交界终止的腰骶段器械融合术患者的失败模式。
