The cervical spine consists of several pairs of joints. It is an area in which stability has been sacrificed for mobility, making the cervical spine particularly vulnerable to injury because it sits between a heavy head and a stable thoracic spine and ribs. The cervical spine is divided into two areas—the cervicoencephalic for the upper cervical spine and the cervicobrachial for the lower cervical spine. The cervicoencephalic or cervicocranial region (C0 to C2) shows the relationship between the cervical spine and the occiput, and injuries in this region have the potential of involving the brain, brainstem, and spinal cord (Figure 3-1).^2,3 Injuries in this area lead to symptoms of headache, fatigue, vertigo, poor concentration, hypertonia of sympathetic nervous system, and irritability. In addition, there may be cognitive dysfunction, cranial nerve dysfunction, and sympathetic system dysfunction.^2,3

The atlanto-occipital joints (C0 to C1) are the two uppermost joints. The principal motion of these two joints is flexion-extension (15° to 20°), or nodding of the head. Side flexion is approximately 10°, whereas rotation is negligible. The atlas (C1) has no vertebral body as such. During development, the vertebral body of C1 evolves into the odontoid process, which is part of C2. The atlanto-occipital joints are ellipsoid and act in unison. Along with the atlanto-axial joints, these joints are the most complex articulations of the axial skeleton.

There are several ligaments that stabilize the atlanto-occipital joints. Anteriorly and posteriorly are the atlanto-occipital membranes. The anterior membrane is strengthened by the anterior longitudinal ligament. The posterior membrane replaces the ligamentum flavum between the atlas and occiput. The tectorial membrane, which is a broad band covering the dens and its ligaments, is found within the vertebral canal and is a continuation of the posterior longitudinal ligament. The alar ligaments are two strong rounded cords found on each side of the upper dens passing upwards and laterally to attach on the medial sides of the occipital condyles. The alar ligaments limit flexion and rotation and play a major role in stabilizing C1 and C2, especially in rotation.⁴

The atlanto-axial joints (C1 to C2) constitute the most mobile articulations of the spine. Flexion-extension is approximately 10°, and side flexion is approximately 5°. Rotation, which is approximately 50°, is the primary movement of these joints. With rotation, there is a decrease in height of the cervical spine at this level as the vertebrae approximate because of the shape of the facet joints. The odontoid process of C2 acts as a pivot point for the rotation. This middle, or median, joint is classified as a pivot (trochoidal) joint. The lateral atlanto-axial, or facet, joints are classified as plane joints. Generally, if a person can talk and chew, there is probably some motion occurring at C1 to C2. At the atlanto-axial joints, the main supporting ligament is the transverse ligament of the atlas, which holds the dens of the axis against the anterior arch of the atlas. It is this ligament that weakens or ruptures in rheumatoid arthritis. As the ligament crosses the dens, there are two projections off the ligament, one going superiorly to the occiput and one inferiorly to the axis. The ligament and the projections form a cross, and the three parts taken together are called the cruciform ligament of the atlas (Figure 3-2).

The vertebral artery—part of the vertebrobasilar system that passes through the transverse processes of the cervical vertebrae usually starting at C6 but entering as high as C4—supplies 20% of the blood supply to the brain (primarily the hindbrain) along with the internal carotid artery (80%) (Figure 3-3).^5,6 In its path, the vertebral artery lies close to the facet joints and vertebral body where it may be compressed by osteophyte formation or injury to the facet joint. In addition, in older individuals, atherosclerotic changes and other vascular risk factors (e.g., hypertension, high fat or cholesterol levels, diabetes, smoking) may contribute to altered blood flow in the arteries.⁷ The vertebral and internal carotid arteries are stressed primarily by rotation, extension, and traction movements, but other movements may also stretch the artery.^8–10 Rotation and extension of as little as 20° have been shown to significantly decrease vertebral artery blood flow.^11,12 The greatest stresses are placed on the vertebral arteries in four places: where it enters the transverse process of C6, within the bony canals of the vertebral transverse processes, between C1 and C2, and between C1 and the entry of the arteries into the skull.^13,14 These latter two areas have the greatest potential for problems (e.g., thrombosis, dissection, stroke) related to treatment and their concomitant stress on the vertebral arteries.¹⁵ Dutton¹³ reports that the most common mechanism for non-penetrating injury to the vertebral artery is neck extension, with or without side flexion or rotation.^16,17 Given the type of injury possible, symptoms may be delayed.^18,19 Symptoms related to the vertebral artery include vertigo, nausea, tinnitus, “drop attacks” (falling without fainting), visual disturbances, or, in rare cases, stroke or death.

The lower cervical spine (C3 to C7) is called the cervicobrachial area, since pain in this area is commonly referred into the upper extremity.^2,3 Pathology in this region leads to neck pain alone, arm pain alone, or both neck and arm pain. Thus, symptoms include neck and/or arm pain, headaches, restricted range of motion (ROM), paresthesia, altered myotomes and dermatomes, and radicular signs. Cognitive dysfunction and cranial nerve dysfunction are not commonly symptoms of injuries in this area although sympathetic dysfunction may be. Injury to both areas, if severe enough, may result in psychosocial issues.

There are 14 facet (apophyseal) joints in the cervical spine (C1 to C7). The upper four facet joints in the two upper thoracic vertebrae (T1 to T2) are often included in the examination of the cervical spine. The superior facets of the cervical spine face upward, backward, and medially; the inferior facets face downward, forward, and laterally (Figure 3-4). This plane facilitates flexion and extension, but it prevents simple rotation or side flexion without both occurring to some degree together. This is called a coupled movement with rotation and side flexion both occurring with either movement.²⁰ Ishii et al.^21,22 reported that between C0 and C2, as well as C7 and T1, the two movements occur in opposite directions while between C2 and C7, they occur in the same direction. These joints move primarily by gliding and are classified as synovial (diarthrodial) joints. The capsules are lax to allow sufficient movement. At the same time, they provide support and a check-rein type of restriction at end range. The greatest flexion-extension of the facet joints occurs between C5 and C6; however, there is almost as much movement at C4 to C5 and C6 to C7. Because of this mobility, degeneration is more likely to be seen at these levels. The neutral or resting position of the cervical spine is slightly extended. The close packed position of the facet joints is complete extension.

The recurrent meningeal, or sinuvertebral, nerve innervates the anterior dura sac, the posterior annulus fibrosus, and the posterior longitudinal ligament. The facet joints are innervated by the medial branch of the dorsal primary rami.²³ For C3 to C7, the main ligaments are the anterior longitudinal ligament, the posterior longitudinal ligament, the ligamentum flavum, and the supraspinal and interspinal ligaments (Figure 3-5). There are also ligaments between the transverse processes (intertransverse ligaments), but in the cervical spine, they are rudimentary.

Some anatomists^24–27 refer to the costal or uncovertebral processes as uncinate joints or joints of Luschka (Figure 3-6). These structures were described by von Luschka in 1858. The uncus gives a “saddle” form to the upper aspect of the cervical vertebra, which is more pronounced posterolaterally; it has the effect of limiting side flexion. Extending from the uncus is a “joint” that appears to form because of a weakness in the annulus fibrosus. The portion of the vertebra above, which “articulates” or conforms to the uncus, is called the échancrure, or notch. Notches are found from C3 to T1, but according to most authors,^24–27 they are not seen until age 6 to 9 years and are not fully developed until 18 years of age. There is some controversy as to whether they should be classified as real joints because some authors believe they are the result of degeneration of the intervertebral disc.

The intervertebral discs make up approximately 25% of the height of the cervical spine. No disc is found between the atlas and the occiput (C0 to C1) or between the atlas and the axis (C1 to C2). It is the discs rather than the vertebrae that give the cervical spine its lordotic shape (Figure 3-7). The nucleus pulposus functions as a buffer to axial compression in distributing compressive forces, whereas the annulus fibrosus acts to withstand tension within the disc. The intervertebral disc has some innervation on the periphery of the annulus fibrosus.^28,29

There are seven vertebrae in the cervical spine with the body of each vertebra (except C1) supporting the weight of those above it. The facet joints may bear some of the weight of the vertebrae above, but this weight is minimal if the normal lordotic posture is maintained. However, even this slight amount of weight bearing can lead to spondylitic changes in these joints. The outer ring of the vertebral body is made of cortical bone, and the inner part is made of cancellous bone covered with the cartilaginous end plate. The vertebral arch protects the spinal cord, while the spinous processes, most of which are bifid in the cervical spine, provide for attachment of muscles. The transverse processes have basically the same function. In the cervical spine, the transverse processes are made up of two parts: the anterior portion that provides the foramen for the vertebral body, and the posterior portion containing the two articular facets (see Figure 3-4, B). In the cervical spine, the spinous processes are at the level of the facet joints of the same vertebra. Generally, the spinous process is considered to be absent or at least rudimentary on C1. This is why the first palpable vertebra descending from the external occiput protuberance is the spinous process of C2.

Although there are seven cervical vertebrae, there are eight cervical nerve roots. This difference occurs because there is a nerve root exiting between the occiput and C1 that is designated the C1 nerve root. In the cervical spine, each nerve root is named for the vertebra below it. As an example, C5 nerve root exists between the C4 and C5 vertebrae (Figure 3-8). In the rest of the spine, each nerve root is named for the vertebra above; the L4 nerve root, for example, exists between the L4 and L5 vertebrae. The switch in naming of the nerve roots from the one below to the one above is made between the C7 and T1 vertebrae. The nerve root between these two vertebrae is called C8, accounting for the fact that there are eight cervical nerve roots and only seven cervical vertebrae.

In addition to the questions listed under Patient History in Chapter 1, the examiner should obtain the following information from the patient: