BACKGROUND Excision of excessive amount of facet joint during lumbar discectomy or decompression can cause segmental instability of the lumbar spine. This study was performed to assess the segmental instability, facet joint loading and intradiscal pressure following graded lumbar facetectomy. This biomechanical study was performed using a verified and validated L3-S1 finite element model. METHODS Nine scenarios were analysed. Intact model as control, 30%, 45%, 60% and complete facet joint excision in unilateral and bilateral setting. The effect of progressive graded facetectomy of L4-L5 on the segmental mobility, facet loading and intradiscal pressure was assessed. FINDINGS In comparison with control 30% excision of the facet joint mainly caused increase in mediolateral mobility. With 45% excision of the facet joint there was increase in both anteroposterior and mediolateral mobility, this was worse in bilateral and unilateral models respectively. This worsened with larger facet excision scenarios. Facet load increased significantly on extension with excision of 45% & 60% unilaterally and 100% bilaterally. Flexion produced rise in intradiscal pressure in all scenarios. INTERPRETATION The increased spinal mobility, facet loading and intradiscal pressure with more than 30% facetectomy highlights the importance of preserving the facets during decompression thereby safeguarding accelerated degeneration of these segments and iatrogenic segmental instability. The findings from this study could also potentially explain the correlation between spinal instability, disc degeneration and facet joint arthrosis as noted in clinical studies.

中文翻译：

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分级单侧和双侧小平面切除术后的腰椎稳定性：有限元模型研究。

背景技术在腰椎间盘切除术或减压过程中切除过多的小面关节会导致腰椎节段性不稳定。进行这项研究以评估腰椎小平面切除术后的节段性不稳定性，小关节负荷和椎间盘内压力。这项生物力学研究是使用经过验证的L3-S1有限元模型进行的。方法分析了九种情景。完整模型作为对照，在单侧和双侧环境中分别进行30％，45％，60％和完整的小关节切除。评估了L4-L5渐进式小平面切除术对节段运动性，小平面负荷和椎间盘内压的影响。结果与对照组相比，小关节的30％切除主要导致中外侧活动性增加。切除小关节的45％后，前后移动性均增加，这在双边和单侧模型中均较差。随着小平面切除方案的增加，这种情况恶化了。扩展时，小面负荷显着增加，单侧切除45％和60％，双侧切除100％。在所有情况下，屈曲都会导致椎间盘内压力升高。解释随着30％以上的小平面切除术，脊柱活动度，小平面负荷和椎间盘内压力增加，突出了在减压过程中保留小平面的重要性，从而保护了这些节段的加速变性和医源性节段不稳定性。这项研究的发现也可能解释脊髓不稳定之间的相关性，