Cervical spondylosis is a chronic degenerative condition of the cervical spine that affects the vertebral bodies and intervertebral disks of the neck (in the form of, for example, disk herniation and spur formation), as well as the contents of the spinal canal (nerve roots and/or spinal cord). Some authors also include the degenerative changes in the facet joints, longitudinal ligaments, and ligamentum flavum.
Spondylosis progresses with age and often develops at multiple interspaces. Chronic cervical degeneration is the most common cause of progressive spinal cord and nerve root compression. Spondylotic changes can result in stenosis of the spinal canal, lateral recess, and foramina. Spinal canal stenosis can lead to myelopathy, whereas the latter 2 can cause radiculopathy. (See image below)
Intervertebral disks lose hydration and elasticity with age, and these losses lead to cracks and fissures. The surrounding ligaments also lose their elastic properties and develop traction spurs. The disk subsequently collapses as a result of biomechanical incompetence, causing the annulus to bulge outward. As the disk space narrows, the annulus bulges, and the facets override. This change, in turn, increases motion at that spinal segment and further hastens the damage to the disk. Annulus fissures and herniation may occur. Acute disk herniation may complicate chronic spondylotic changes.
As the annulus bulges, the cross-sectional area of the canal is narrowed. This effect may be accentuated by hypertrophy of the facet joints (posteriorly) and of the ligamentum flavum, which becomes thick with age. Neck extension causes the ligaments to fold inward, reducing the anteroposterior (AP) diameter of the spinal canal.
As disk degeneration occurs, the uncinate process overrides and hypertrophies, compromising the ventrolateral portion of the foramen. Likewise, facet hypertrophy decreases the dorsolateral aspect of the foramen. This change contributes to the radiculopathy that is associated with cervical spondylosis. Marginal osteophytes begin to develop. Additional stresses, such as trauma or long-term heavy use, may exacerbate this process. These osteophytes stabilize the vertebral bodies adjacent to the level of the degenerating disk and increase the weight-bearing surface of the vertebral endplates. (See images below) The result is decreased effective force on each of these structures.
Degeneration of the joint surfaces and ligaments decreases motion and can act as a limiting mechanism against further deterioration. Thickening and ossification of the posterior longitudinal ligament (OPLL) also decreases the diameter of the canal. [1, 2, 3]
The blood supply of the spinal cord is an important anatomic factor in the pathophysiology. Radicular arteries in the dural sleeves tolerate compression and repetitive minor trauma poorly. The spinal cord and canal size also are factors. A congenitally narrow canal does not necessarily predispose a person to myelopathy, but symptomatic disease rarely develops in individuals with a canal that is larger than 13 mm.
Cervical spondylosis is a common condition that is estimated to account for 2% of all hospital admissions. It is the most frequent cause of spinal cord dysfunction in patients older than 55 years. On the basis of radiologic findings, 90% of men older than 50 years and 90% of women older than 60 years have evidence of degenerative changes in the cervical spine.
Evidence from a 2009 report indicated that cervical spondylosis with myelopathy was the most common primary diagnosis (36%) among elderly US patients admitted to the hospital for surgical treatment of a degenerative cervical spine between 1992 and 2005.  The study, which looked at 156,820 hospital admissions for elderly Medicare beneficiaries, also determined that fusion was the most common procedure (70%) performed in these patients for cervical spine degeneration, with 58% of the fusions being anterior.
Investigators in a study involving Ghanaians reported, "out of 225 patients who carried loads on their head, 143 (63.6%) had cervical spondylosis, and of the 80 people who did not carry load on their head, 29 (36%) had cervical spondylosis."
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The course of cervical spondylosis may be slow and prolonged, and patients may either remain asymptomatic or have mild cervical pain.
Long periods of nonprogressive disability are typical, and in a few cases, the patient's condition progressively deteriorates.
Morbidity ranges from chronic neck pain, radicular pain, diminished cervical range of motion (ROM), headache, myelopathy leading to weakness, and impaired fine motor coordination to quadriparesis and/or sphincteric dysfunction (eg, difficulty with bowel or bladder control) in advanced cases. The patient may eventually become chair-bound or bedridden.
No apparent correlation between race and cervical spondylosis exists.
Both sexes are affected equally. Cervical spondylosis usually starts earlier in men than in women.
Symptoms of cervical spondylosis may appear in persons as young as 30 years but are found most commonly in individuals aged 40-60 years. Radiologic spondylotic changes increase with patient age; 70% of asymptomatic persons older than 70 years have some form of degenerative change in the cervical spine.
A retrospective study by Wang et al of 1276 cases of cervical spondylosis found an aging-related increase in the incidence of the condition—including bulge or herniation at C3-C4, C4-C5, C5-C6, and C6-C7—in patients up to age 50 years and a decrease in the condition’s incidence with aging in patients older than 50 years, with the decrease particularly seen after age 60 years. Additionally, an aging-related increase in the incidence of hyperosteogenesis and spinal stenosis was found prior to age 60 years, with a decrease in incidence seen after age 60 years. 
Cervical spondylosis usually starts earlier in men than in women. When cervical spondylosis develops in a young individual, it is almost always secondary to a predisposing abnormality in one of the joints between the cervical vertebrae, probably as a result of previous mild trauma.
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