The zygapophyseal joints of the spine, also known as the facet joints, are paired diarthrodial joints posterior to the intervertebral disc and neural elements. The pathophysiology of facet osteoarthritis (OA), as well as crosstalk between the disc and facets, remains largely understudied compared to disc degeneration. The purpose of this study was to characterize alterations to human facet cartilage and subchondral bone across a spectrum of degeneration and to investigate correlations between disc and facet degeneration. Human lumbar facet articular surfaces from six independent donors were subject to creep indentation mechanical testing to quantify cartilage mechanical properties, followed by microcomputed tomography (µCT) analyses for subchondral bone morphometry. The degenerative state of each articular surface was assessed via macroscopic scoring and via Osteoarthritis Research Society International histopathology scoring. Our data suggest reduced facet cartilage compressive and tensile moduli and increased permeability with increasing degenerative grade, particularly at the lower levels of the spine. µCT analyses revealed spinal level-dependent alterations to the subchondral bone, with an increase in trabecular bone at the L4−L5 level, but a decrease at the upper levels of the lumbar spine with increasing degenerative grade. Cortical bone volume fraction was generally decreased with increasing degenerative grade across spinal levels. Correlation analysis revealed several associations between quantitative measures of disc degeneration and facet OA. This study showed that alterations in the mechanical properties of facet cartilage and in the structural properties of facet subchondral bone correlated with aspects of disc degeneration and were highly dependent on spinal level.

中文翻译：

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人小面软骨力学和脊柱退化骨形态测量的水平依赖性改变

脊柱的关节突关节，也称为小关节，是椎间盘和神经元件后方的成对动关节。与椎间盘退变相比，小关节骨关节炎 (OA) 的病理生理学以及椎间盘和小关节之间的串扰在很大程度上仍未得到充分研究。本研究的目的是描述人类小关节软骨和软骨下骨在一系列退化过程中的变化，并研究椎间盘和小关节退变之间的相关性。来自六个独立捐助者的人体腰椎关节面进行了蠕变压痕机械测试，以量化软骨机械特性，然后进行显微计算机断层扫描 (µCT) 分析软骨下骨形态。每个关节面的退行性状态通过宏观评分和骨关节炎研究协会国际组织病理学评分进行评估。我们的数据表明，随着退化程度的增加，小面软骨的压缩和拉伸模量降低，渗透性增加，特别是在脊柱的较低水平。µCT 分析显示软骨下骨的脊柱水平依赖性改变，L4-L5 水平的小梁骨增加，但随着退行性程度的增加，腰椎上部水平的骨小梁减少。皮质骨体积分数通常随着脊柱退化程度的增加而降低。相关性分析揭示了椎间盘退变的定量测量与小关节 OA 之间的几种关联。