Immunohistochemical and Histological Study of Human Uncovertebral Joints Spine May 20, 2009;Volume 34, Number 12, pp 1257-1263

Brismée, Jean-Michel ScD; Sizer, Phillip S. Jr PhD; Dedrick, Gregory S. ScD;Sawyer, Barbara G. PhD; Smith, Michael P. PhD The authors are from the School of Allied Health Sciences, Texas Tech UniversityHealth Sciences Center KEY POINTS FROM THIS STUDY: 1) There is controversy with regard to the anatomic and histological makeup ofthe uncovertebral joints. Some authors claim it to be a synovial joint; othersconsider it to be disc tissue. In his original findings, Von Luschka suggested that theuncinate processes had a joint cavity that was lined with a synovial membrane that secreted synovial fluid.[Hubert von Luschka was the first to describe the uncinate joints in 1858] 2) No research has investigated the presence of pain generating neurotransmitters within the uncovertebral cartilaginous and capsular tissue. Thisstudy investigated the anatomy and innervation of the uncovertebral joints todetermine if it is synovial in nature and capable of generating pain. 3) This study used 2 unembalmed fresh male human cadavers of a mean age of83 years. Tissue from uncovertebral capsule and cartilage was harvested for eachuncovertebral surface from C2-C3 to C6-C7. 4) Chondrocytes and synoviocytes were identified at the capsular tissue of eachuncovertebral joints. [This indicates that the uncinate joints have articularhyaline cartilage and a synovial capsule]. This suggests that the uncovertebraljoint is synovial in nature. 5) Immunoreactivity indicates the uncinate capsules also have the presence ofboth the somatic and autonomic nerve fibers. These findings suggest that theuncovertebral joints are potential pain generators in the cervical spine.[Free nerve endings (pain afferents) were found]. 6) The uncinate capsules are also innervated with post-ganglionic sympatheticefferents. [Important, as this helps establish the biological plausibility ofsomato-sympathetic reflexes] 7) These capsular and synovial tissue nerve fibers lead to pain perception andreflexive responses associated with synovial pathology.[Important: probably including somato-sympathetic reflexes]. 8) Immunohistologic staining in this study found noradrenergic sympatheticpostganglionic nerve fibers. The sympathetic nervous innervation can causenonsegmental spinal pain patterns. [And has potential visceral consequences]. 9) Biomecahnically, the uncovertebral joint is a major contributor to coupledmotion at the lower cervical spinal segments and serves as a controlling factor ofoverall cervical segmental motion.[These joints are biomechanically important]. 10) A synovial or diarthrodial joint must exhibit a joint capsule, a synovialmembrane, synovial fluid, and articular cartilage. Our present findings support thenotion that the uncovertebral complex includes a synovial joint. 11) Disc degeneration always influences the uncinate joints, their biomechanicsand their degenerative potential. 12) Degenerative changes in the uncinate joints may translate into osteophyticprojections that can compress adjacent cervical segmental nerves as they coursethrough the intervertebral foramen or may cause cervical myelopathy. 13) Due to the close proximity of the uncinate process to the vertebral arterydegenerative changes in the uncovertebral joint have been clinically related tovertebral artery compression, ultimately lending to the onset and severity of clinicalvertebrobasilar insufficiency. COMMENTS FROM DAN MURPHY Many chiropractors, myself included, contend that the uncinate joint can becomesubluxated. The uncinate joint subluxation is distinct from the facet jointsubluxation. The adjustment of the uncinate joint subluxation is quite distinct fromthe facet joint subluxation.This study indicates that the uncinate joint is innervated with pain afferents and isthus a source of neck pain. Since pain perception is controlled by mechanicalintegrity (Melzacks and Walls Gate theory), and a subluxated uncinate joint is aloss of mechanical integrity, one would need to adjust the subluxated uncinate jointto best manage some cases of neck pain. Because the uncinate joints are innervated with post-ganglionic sympatheticefferents nerve fibers, it is easier to explain their involvement in cervical somato-sympathetic reflexes that may influence systemic health and wellbeing.