Alavi Fatemeh, Nielsen Christopher J, Lewis Stephen, Rampersaud Raja, Cheung Angela M
Osteoporosis Program, University Health Network(UHN), Toronto, ON, Canada.
Department of Medicine, University Health Network(UHN), Toronto, ON, Canada.
Global Spine J. 2025 Feb 27:21925682251321789. doi: 10.1177/21925682251321789.
Biomechanical modeling study.
Despite several recognized risk factors for proximal junctional kyphosis (PJK), its causative mechanism remains unknown. There are limited biomechanical studies to elucidate the association of sagittal alignment with PJK. Our aim is to determine the association of adjacent forces with PJK development.
ASD patients operated on with posterior fusion from T9-T11 to the pelvis and had 2 year follow-up were included in this retrospective study. Patient-specific musculoskeletal models were created from EOS images. High vs low normalized vertebral forces were defined based on a threshold of 0.2 for shear and 0.5 for compression. The load ratio was defined as the ratio of immediate postoperative to preoperative vertebral forces.
A total of 35 patients (19 PJK, 16 Non-PJK) were included. PJK patients had statistically significant global malalignment with respect to global tilt (GT), T1 pelvic angle (TPA) and C2-UIV+1PA. A high-risk zone for the development of PJK is defined as high normalized shear and/or compression with a high load ratio. While none of the non-PJK patients were in the high-risk zone, 5 PJK patients were not in that zone, suggesting factors other than alignment may have contributed to this adverse event. Despite low shear for 3 of these non-PJK patients, they experienced high shear ratio.
The proposed thresholds were accurate in 86% of patients who developed PJK. These findings suggest postoperative shear at UIV+1 as an important risk factor for PJK. Keeping shear force low in alignment will help surgeons reduce PJK development.
生物力学建模研究。
尽管近端交界性后凸（PJK）存在多种公认的危险因素，但其致病机制仍不清楚。用于阐明矢状面排列与PJK之间关联的生物力学研究有限。我们的目的是确定相邻力与PJK发展之间的关联。
本回顾性研究纳入了接受从T9 - T11至骨盆后路融合手术并进行了2年随访的强直性脊柱炎（ASD）患者。根据EOS图像创建患者特异性肌肉骨骼模型。高与低标准化椎体力是根据剪切力0.2和压缩力0.5的阈值定义的。负荷比定义为术后即刻与术前椎体力的比值。
共纳入35例患者（19例PJK，16例非PJK）。PJK患者在整体倾斜（GT）、T1骨盆角（TPA）和C2 - UIV + 1PA方面存在统计学上显著的整体排列不齐。PJK发展的高风险区域定义为具有高负荷比的高标准化剪切力和/或压缩力。虽然非PJK患者均不在高风险区域，但有5例PJK患者不在该区域，这表明除排列之外的因素可能导致了这一不良事件。尽管其中3例非PJK患者的剪切力较低，但他们的剪切力比值较高。
所提出的阈值在86%发生PJK的患者中是准确的。这些发现表明UIV + 1处的术后剪切力是PJK的一个重要危险因素。在排列过程中保持剪切力低将有助于外科医生减少PJK的发生。
