MECHANISMS OF LOW-BACK-PAIN - NEUROPHYSIOLOGIC AND NEUROANATOMICAL STUDY

Idiopathic law back pain has confounded health care practitioners for decades, The cellular and neural mechanisms that lead to facet pain, d iscogenic pain, and sciatica are not well understood, To help elucidat e these mechanisms, anesthetized New Zealand white rabbits were used i n a series of neurophysiologic and neuroanatomic studies, These studie s showed the following evidence in support of facet pain: an extensive distribution of small nerve fibers and endings in the lumbar facet jo int, nerves containing substance P, high threshold mechanoreceptors in the facet joint capsule, and sensitization and excitation of nerves i n facet joint and surrounding muscle when the nerves were exposed to i nflammatory or algesic chemicals, Evidence for pain of disc origin inc luded an extensive distribution of small nerve fibers and free nerve e ndings in the superficial annulus of the disc and small fibers and fre e nerve endings in adjacent longitudinal ligaments, Possible mechanism s of sciatica included vigorous and long lasting excitatory discharges when dorsal root ganglia were subjected to moderate pressure, excitat ion of dorsal Boot fibers when the ganglia were exposed to autologous nucleus pulposus, and excitation and Boss of nerve function in nerve r oots exposed to phospholipase A(2).