Cavanaugh John M, Lu Ying, Chen Chaoyang, Kallakuri Srinivasu
Bioengineering Center, Wayne State University, 818 West Hancock, Detroit, MI 48202, USA.
J Bone Joint Surg Am. 2006 Apr;88 Suppl 2:63-7. doi: 10.2106/JBJS.E.01411.
Facet joints are implicated as a major source of neck and low-back pain. Both cervical and lumbar facet syndromes have been described in the medical literature. Biomechanical studies have shown that lumbar and cervical facet-joint capsules can undergo high strains during spine-loading. Neuroanatomic studies have demonstrated free and encapsulated nerve endings in facet joints as well as nerves containing substance P and calcitonin gene-related peptide. Neurophysiologic studies have shown that facet-joint capsules contain low-threshold mechanoreceptors, mechanically sensitive nociceptors, and silent nociceptors. Inflammation leads to decreased thresholds of nerve endings in facet capsules as well as elevated baseline discharge rates. Recent biomechanical studies suggest that rear-end motor-vehicle impacts give rise to excessive deformation of the capsules of lower cervical facet joints. Still unresolved is whether this stretch is sufficient to activate nociceptors in the joint capsule. To answer this question, recent studies indicate that low stretch levels activate proprioceptors in the facet-joint capsule. Excessive capsule stretch activates nociceptors, leads to prolonged neural afterdischarges, and can cause damage to the capsule and to axons in the capsule. In instances in which a whiplash event is severe enough to injure the joint capsule, facet capsule overstretch is a possible cause of persistent neck pain.
小关节被认为是颈部和下背部疼痛的主要来源。医学文献中已经描述了颈椎和腰椎小关节综合征。生物力学研究表明，在脊柱负荷过程中，腰椎和颈椎小关节囊会承受高应变。神经解剖学研究已经证明小关节中有游离的和被包裹的神经末梢，以及含有P物质和降钙素基因相关肽的神经。神经生理学研究表明，小关节囊包含低阈值机械感受器、机械敏感伤害感受器和静息伤害感受器。炎症会导致小关节囊内神经末梢的阈值降低以及基线放电率升高。最近的生物力学研究表明，追尾机动车碰撞会导致下颈椎小关节囊过度变形。目前仍未解决的问题是，这种拉伸是否足以激活关节囊内的伤害感受器。为了回答这个问题，最近的研究表明，低拉伸水平会激活小关节囊内的本体感受器。过度的关节囊拉伸会激活伤害感受器，导致神经放电后持续时间延长，并可能对关节囊和囊内轴突造成损伤。在挥鞭样损伤事件严重到足以损伤关节囊的情况下，小关节囊过度拉伸可能是持续性颈部疼痛的一个原因。
