Purpose

The protection of articular processes (AP) in the transforaminal endoscopic discectomy (TED) was proven to optimise post-operative biomechanical environments. Published studies reported a large grade of nuclectomy leading to poor prognosis, but the underlying biomechanical mechanism was unclearly illustrated. This study aimed to investigate the changes of biomechanical environments after an in-out TED with intact AP and a large grade of nuclectomy and an out-in TED with limited foraminoplasty and a smaller grade of nuclectomy.

Methods

A previously constructed and validated lumbo–sacral model was used in this study, and in-out TED with intact AP and out-in TED with limited foraminoplasty, a smaller grade of nuclectomy was simulated. Biomechanical changes in the L5–S1 segment related to the degeneration acceleration were computed under different directional loading conditions.

Results

Post-operative biomechanical changes after the out-in TED with limited foraminoplasty were slight, except for the facet contact pressure under the extension position. By contrast, significant biomechanical deterioration, both in the adjacent disc and zygapophyseal joints, is observed under extension in the model after the in-out TED with large nuclectomy.

Conclusion

A large grade of nuclectomy is regarded as an independent risk factor of adjacent segment disease in the caudal functional spinal unit after the in-out TED.

中文翻译：

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经椎间孔镜椎间盘切除术中大级别髓核切除术的负面生物力学影响增加了相邻节段疾病的风险：一项有限元研究

目的

经椎间孔内窥镜椎间盘切除术 (TED) 中对关节突 (AP) 的保护已被证明可以优化术后生物力学环境。已发表的研究报告了大量的髓核切除术导致预后不良，但其潜在的生物力学机制尚不清楚。本研究旨在探讨完整 AP 和大级别髓核切除术的 in-out TED 和有限的椎间孔成形术和较小级别的髓核切除术的 in-out TED 后生物力学环境的变化。

方法

本研究使用了先前构建和验证的腰骶模型，模拟了具有完整 AP 的 in-out TED 和具有有限椎间孔成形术的 out-in TED，模拟了较小级别的髓核切除术。L5-S1 段与退化加速度相关的生物力学变化是在不同的定向载荷条件下计算的。

结果

除了在伸展位置下的小关节接触压力外，在有限的椎间孔成形术的外进 TED 后，手术后的生物力学变化是轻微的。相比之下，在进行大核切除术的进出 TED 后，在模型的伸展下观察到相邻椎间盘和关节突关节的显着生物力学恶化。

结论

大级别的髓核切除术被认为是in-out TED后尾部功能性脊柱单元相邻节段疾病的独立危险因素。