BACKGROUND Adjacent segment disease (ASD) is a well-known complication after interbody fusion. Pedicle screw-rod revision possesses sufficient strength and rigidity. However, is a surgical segment with rigid fixation necessary for ASD reoperation? This study aimed to investigate the biomechanical effect of different instrumentation on lateral lumbar interbody fusion (LLIF) for ASD treatment. METHODS A validated L2~5 finite element (FE) model was modified for simulation. ASD was considered the level cranial to the upper-instrumented segment (L3/4). Bone graft fusion in LLIF with bilateral pedicle screw (BPS) fixation occurred at L4/5. The ASD segment for each group underwent a) LLIF + posterior extension of BPS, b) PLIF + posterior extension of BPS, c) LLIF + lateral screw, and d) stand-alone LLIF. The L3/4 range of motion (ROM), interbody cage stress and strain, screw-bone interface stress, cage-endplate interface stress, and L2/3 nucleus pulposus of intradiscal pressure (NP-IDP) analysis were calculated for comparisons among the four models. RESULTS All reconstructive models displayed decreased motion at L3/4. Under each loading condition, the difference was not significant between models a and b, which provided the maximum ROM reduction (73.8 to 97.7% and 68.3 to 98.4%, respectively). Model c also provided a significant ROM reduction (64.9 to 77.5%). Model d provided a minimal restriction of the ROM (18.3 to 90.1%), which exceeded that of model a by 13.1 times for flexion-extension, 10.3 times for lateral bending and 4.8 times for rotation. Model b generated greater cage stress than other models, particularly for flexion. The maximum displacement of the cage and the peak stress of the cage-endplate interface were found to be the highest in model d under all loading conditions. For the screw-bone interface, the stress was much greater with lateral instrumentation than with posterior instrumentation. CONCLUSIONS Stand-alone LLIF is likely to have limited stability, particularly for lateral bending and axial rotation. Posterior extension of BPS can provide reliable stability and excellent protective effects on instrumentation and endplates. However, LLIF with the use of an in situ screw may be an alternative for ASD reoperation.

中文翻译：

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腰椎外侧椎体融合术后相邻节段疾病的策略的生物力学评估：是否需要延长椎弓根螺钉？

背景技术相邻节段疾病（ASD）是椎间融合后的众所周知的并发症。椎弓根螺钉翻新具有足够的强度和刚度。但是，对于ASD再次手术，是否需要使用刚性固定的手术部分？这项研究的目的是调查不同的仪器对外侧腰椎椎间融合术（LLIF）进行ASD治疗的生物力学效果。方法对经过验证的L2〜5有限元（FE）模型进行仿真。ASD被认为是上器械段的颅骨水平（L3 / 4）。LLIF双侧椎弓根螺钉（BPS）固定的植骨融合发生在L4 / 5。每组的ASD段均接受a）LLIF + BPS的后延伸，b）PLIF + BPS的后延伸，c）LLIF +侧向螺钉，以及d）独立的LLIF。L3 / 4的运动范围（ROM），计算了椎间融合器的笼间应力和应变，螺钉-骨界面应力，笼-终板界面应力以及椎间盘内压力的L2 / 3髓核（NP-IDP）分析，以比较这四个模型。结果所有重建模型在L3 / 4处的运动减少。在每种加载条件下，模型a和b之间的差异都不显着，这提供了最大的ROM减少（分别为73.8％至97.7％和68.3％至98.4％）。模型c还显着减少了ROM（64.9％至77.5％）。模型d提供了最小的ROM限制（18.3％至90.1％），其弯曲伸长率比模型a限制了13.1倍，横向弯曲超过了10.3倍，旋转超过了4.8倍。模型b产生比其他模型更大的保持架应力，尤其是对于屈曲而言。在所有载荷条件下，模型d中的保持架最大位移和保持架-端板界面的峰值应力最高。对于螺丝钉-骨界面，侧向器械的应力要比后侧器械的应力大得多。结论独立的LLIF可能具有有限的稳定性，特别是对于横向弯曲和轴向旋转。BPS向后延伸可以为仪器和端板提供可靠的稳定性和出色的保护效果。但是，使用原位螺钉的LLIF可能是ASD重新手术的替代方法。结论独立的LLIF可能具有有限的稳定性，特别是对于横向弯曲和轴向旋转。BPS向后延伸可以为仪器和端板提供可靠的稳定性和出色的保护效果。但是，使用原位螺钉的LLIF可能是ASD重新手术的替代方法。结论独立的LLIF可能具有有限的稳定性，特别是对于横向弯曲和轴向旋转。BPS向后延伸可以为仪器和端板提供可靠的稳定性和出色的保护效果。但是，使用原位螺钉的LLIF可能是ASD重新手术的替代方法。