Optimal tether configurations and preload tensioning to prevent proximal junctional kyphosis: a finite element analysis

作者：Thomas J. Buell, Shay Bess, Ming Xu, Frank J. Schwab, Virginie Lafage, Christopher P. Ames, Christopher I. Shaffrey, Justin S. Smith · 发表于：Journal of Neurosurgery Spine · 年份：2019 · DOI：10.3171/2018.10.spine18429 · 被引用次数：71 · 研究领域：Scoliosis diagnosis and treatment、Spinal Fractures and Fixation Techniques、Spine and Intervertebral Disc Pathology

OBJECTIVE: Proximal junctional kyphosis (PJK) is, in part, due to altered segmental biomechanics at the junction of rigid instrumented spine and relatively hypermobile non-instrumented adjacent segments. Proper application of posteriorly anchored polyethylene tethers (i.e., optimal configuration and tension) may mitigate adjacent-segment stress and help prevent PJK. The purpose of this study was to investigate the impact of different tether configurations and tensioning (preloading) on junctional range-of-motion (ROM) and other biomechanical indices for PJK in long instrumented spine constructs. METHODS: Using a validated finite element model of a T7-L5 spine segment, testing was performed on intact spine, a multilevel posterior screw-rod construct (PS construct; T11-L5) without tether, and 15 PS constructs with different tether configurations that varied according to 1) proximal tether fixation of upper instrumented vertebra +1 (UIV+1) and/or UIV+2; 2) distal tether fixation to UIV, to UIV-1, or to rods; and 3) use of a loop (single proximal fixation) or weave (UIV and/or UIV+1 fixation in addition to UIV+1 and/or UIV+2 proximal attachment) of the tether. Segmental ROM, intradiscal pressure (IDP), inter- and supraspinous ligament (ISL/SSL) forces, and screw loads were assessed under variable tether preload. RESULTS: PS construct junctional ROM increased abruptly from 10% (T11-12) to 99% (T10-11) of baseline. After tethers were grouped by most cranial proximal fixation (UIV+1...