Dalley, 10th Edition

Chapter 2 ■ Back

108

and 70, their anteroposterior (AP) diameter increases about 10% in females and 2% in males. The thickness (height) in creases centrally about 10% in both sexes. Overt or marked disc narrowing, especially when it is greater than that of more superiorly located discs, suggests pathology ( degen erative disc disease ), not normal aging (Bogduk, 2012). Back Pain Back pain in general, and lower back pain (LBP) in particular, is an immense health prob lem, second only to the common cold as a rea son people visit their doctors. In terms of health factors causing lost workdays, backache is second only to headache. The anatomical bases for the pain, especially the nerves initially involved in sensing and carrying pain from the vertebral column itself, are rarely described. Five categories of structures receive innervation in the back and can be sources of pain: 1. Fibroskeletal structures: periosteum, ligaments, and anuli brosi of IV discs 2. Meninges: coverings of the spinal cord 3. Synovial joints: capsules of the zygapophysial joints 4. Muscles: intrinsic muscles of the back 5. Nervous tissue: spinal nerves or nerve roots exiting the IV foramina Of these, the rst two categories are innervated by (recurrent) meningeal branches of the spinal nerves, and the next two are innervated by posterior rami (ar ticular and muscular branches). Pain from nervous tissue—that is, caused by compression or irritation of spinal nerves or nerve roots—is typically referred pain , perceived as coming from the cutaneous or subcutaneous area (dermatome) supplied by that nerve (see the Clini cal Box “Herniation of Nucleus Pulposus [Herniation of IV Disc]”), but it may be accompanied by localized pain. Pain related to the meninges is relatively rare and is discussed later in this chapter.

Posterior (dorsal) ramus

Spinal nerve

Recurrent branch, meningeal nerve

Dura mater

Posterior longitudinal ligament Dura mater Arachnoid mater

Anterior (ventral) ramus

Gray ramus communicans

Communicating branch, meningeal nerve

Sympathetic trunk Sympathetic ganglion

Intervertebral disc

Anterior longitudinal ligament

Nerve bers to the periosteum, anuli brosi, and liga ments supply pain receptors. Those to the anuli brosi and ligaments also supply receptors for proprioception (the sense of one’s position). Sympathetic bers to the blood ves sels stimulate vasoconstriction. FIGURE 2.31. Innervation of periosteum and ligaments of vertebral column and meninges. Superior view

CLINICAL BOX

VERTEBRAL COLUMN Aging of Intervertebral Discs

With advancing age, the nuclei pulposi dehydrate and lose elastin and proteoglycans while gaining col lagen. As a result, the IV discs lose their turgor (full ness), becoming stiffer and more resistant to deformation. As the nucleus dehydrates, the two parts of the disc appear to merge as the distinction between them becomes increasingly diminished. With advancing age, the nucleus be comes dry and granular, and it may disappear altogether as a distinct formation. As these changes occur, the anulus brosis assumes an increasingly greater share of the vertical load and the stresses and strains that come with it. The lamellae of the anulus thicken and often develop ssures and cavities. Although the margins of adjacent vertebral bodies may ap proach more closely as the superior and inferior surfaces of the body become shallow concavities (the most probable reason for slight loss of height with aging), it has been shown that the intervertebral discs increase in size with age. Not only do they become increasing convex but also, between the ages of 20 Localized lower back pain (LBP) (perceived as coming from the back) is generally muscular, joint, or broskeletal pain. Muscular pain is usually related to re exive cramp ing (spasms) producing ischemia , often secondarily as a result of guarding (contraction of muscles in anticipation of pain). Zygapophysial joint pain is generally associated with aging (osteoarthritis) or disease (rheumatoid arthri tis) of the joints. Pain from vertebral fractures and disloca tions is no different than that from other bones and joints: The sharp pain following a fracture is mostly periosteal (membrane covering the bone) in origin, whereas pain from dislocations is ligamentous (relating to the structure of the ligament). The acute localized pain associated with an IV disc herniation undoubtedly emanates from the dis rupted posterolateral anulus brosis and impingement on the posterior longitudinal ligament. Pain in all of these latter instances is conveyed initially by the meningeal branches of the spinal nerves (see Figs. 2.30 and 2.31). Copyright © 2027 Wolters Kluwer. Unauthorized reproduction of the article is prohibited.