Removal of fixation construct could mitigate adjacent segment stress after lumbosacral fusion: A finite element analysis
Removal of fixation construct could mitigate adjacent segment stress after lumbosacral fusion: A finite element analysis
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DOI：
10.1016/j.clinbiomech.2017.02.011
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发表时间：
2017-03-01
影响因子：
1.8
通讯作者：
Chiang, Chang Jung
中科院分区：
文献类型：
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作者：
Hsieh, Yueh-Ying;Chen, Chia-Hsien;Chiang, Chang Jung
背景资料：后路腰椎椎体间融合术和经椎弓根固定术联合应用已广泛用于治疗各种腰椎退变性椎间盘疾病。经椎弓根固定器的目的是增加稳定性和提高融合率。然而，融合椎间盘和桥接椎体分别如何影响邻近节段疾病的进展尚不清楚。方法：使用经过验证的腰骶有限元模型，分析L4-L5节段的三种变化：1)中度椎间盘退变，2)使用独立的椎弓根固定器和椎弓根螺钉固定器，3)融合后仅使用椎弓根固定器。检查节段间角、椎间盘应力和关节面载荷。还模拟了屈曲、伸展、弯曲和扭转四种运动试验。结果：相邻节段的病变在头节比尾节更严重。经固体融合固定后，相邻节段的节段间角、椎间盘应力和关节面载荷分别增加57.6%、473%和59.6%。然而，这些变化在取出固定架后分别降至30.1%、22.7%和27.0%。这是由于融合和固定机制的生物力学特征不同。解释：与融合相比，固定对桥接节段的活动施加了更严格的约束。目前的研究表明，在完全融合后取出脊柱固定物可以减少相邻节段的应力。通过微创手术，我们可以在移除固定物时减少对棘旁结构的继发性损伤，这是外科医生最关心的问题。(C) 2017年作者。Elsevier Ltd.出版。
Background data: Combined usage of posterior lumbar interbody fusion and transpedicular fixation has been extensively used to treat the various lumbar degenerative disc diseases. The transpedicular fixator aims to increase stability and enhance the fusion rate. However, how the fused disc and bridged vertebrae respectively affect adjacent-segment diseases progression is not yet clear.Methods: Using a validated lumbosacral finite-element model, three variations at the L4-L5 segment were analyzed: 1) moderate disc degeneration, 2) instrumented with a stand-alone cage and pedide screw fixators, and 3) with the cage only after fusion. The intersegmental angles, disc stresses, and facet loads were examined. Four motion tests, flexion, extension, bending, and twisting, were also simulated.Findings: The adjacent-segment disease was more severe at the cephalic segment than the caudal segment. After solid fusion and fixation, the increase in intersegmental angles, disc stresses and facet loads of the adjacent segments were about 57.6%, 473%, and 59.6%, respectively. However, these changes were reduced to 30.1%, 22.7%, and 27.0% after removal of the fixators. This was attributed to the differences between the biomechanical characteristics of the fusion and fixation mechanisms.Interpretation: Fixation superimposes a stiffer constraint on the mobility of the bridged segment than fusion. The current study suggested that the removal of spinal fixators after complete fusion could decrease the stress at adjacent segments. Through a minimally invasive procedure, we could reduce secondary damage to the paraspinal structures while removing the fixators, which is of utmost concern to surgeons. (C) 2017 The Authors. Published by Elsevier Ltd.