Dalley, 10th Edition

Chapter 2 ■ Back

100

the articular processes of adjacent vertebrae. Accessory liga ments unite the laminae, transverse processes, and spinous processes and help stabilize the joints. The zygapophysial joints permit gliding movements be tween the articular processes; the shape and disposition of the articular surfaces determine the types of movement possible. The range (amount) of movement is determined by the size of the IV disc relative to that of the vertebral body. In the cervical and lumbar regions, these joints bear some weight, sharing this function with the IV discs, particularly during lateral exion. The zygapophysial joints are innervated by articular branches that arise from the medial branches of the poste rior rami of spinal nerves (Fig. 2.21). As these nerves pass posteroinferiorly, they lie in grooves on the posterior sur faces of the medial parts of the transverse processes. Each articular branch supplies two adjacent joints; therefore, each joint is supplied by two nerves. The laminae of adjacent vertebral arches are joined by broad, pale yellow bands of elastic tissue, the ligamenta ava (L. avus , yellow). These ligaments extend almost vertically from the lamina above to the lamina below, those of oppo site sides meeting and blending in the midline (Figs. 2.16 and 2.19). The aval ligaments bind the lamina of the ad joining vertebrae together, forming alternating sections of the posterior wall of the vertebral canal. The ligamenta ava ACCESSORY LIGAMENTS OF INTERVERTEBRAL JOINTS

Cauda equina Spinal ganglion in dural sheath Spinal nerve

Posterior ramus of spinal nerve Superior articular process Muscular branch (cut) Articular branches of posterior ramus Zygapophysial joint

Recurrent meningeal nerve Anterior ramus of spinal nerve

Anulus fibrosus Branch to anulus fibrosus of IV disc

Articular branches of posterior ramus

Transverse process Muscular branch (cut)

Lateral branch of posterior ramus

Medial branch of posterior ramus Muscular branch

Muscular branch Cutaneous branch

Articular branches

Posterolateral view

FIGURE 2.21. Innervation of zygapophysial joints. The posterior rami arise from the spinal nerves outside the IV foramen and divide into medial and lateral branches. The medial branch gives rise to articular branches that are distributed to the zygapophysial joint at that level and to the joint one level inferior to its exit. Thus, each zygapophysial joint receives articular rami from the medial branch of the posterior rami of two adjacent spinal nerves. The medial branches of both posterior rami have to be ablated to denervate a zygapophysial joint.

External occipital protuberance

Intervertebral (IV) disc Posterior longitudinal ligament

Posterior atlantooccipital membrane

Atlas

Pedicle (cut)

Axis

Lateral costo transverse ligament

Nuchal ligament

Intertransverse ligament

Ligamenta flava

Transverse process Copyright © 2027 Wolters Kluwer. Unauthorized reproduction of the article is prohibited.

Interspinous ligaments

Joint capsules of zygapophysial joints

Spinous process of C7 vertebra Supraspinous ligament

Interspinous ligament Supraspinous ligament

Anterior longitudinal ligament

(A) Lateral view

(B) Posterolateral view

FIGURE 2.20. Joints and ligaments of vertebral column. A. Ligaments in cervical region. Superior to the prominent spinous process of C7 (vertebra prominens), the spinous processes are deeply placed and attached to an overlying nuchal ligament. B. Ligaments in thoracic region. The pedicles of the superior two vertebrae have been sawn through and the vertebral arches removed to reveal the posterior longitudinal ligament. Intertransverse, supraspinous, and interspinous ligaments are demonstrated in association with the vertebrae with intact vertebral arches.