Degenerative Conditions of the Lower Cervical Spine
Chronic cervical degeneration is the most common cause of progressive nerve root and spinal cord
deterioration. In 1932 Schmorl and Junghan reported that 90% of females over 60 years of age and 90% of
males over 50 years have radiographic evidence of cervical degeneration. The term cervical spondylosis
refers to the disease process which involves the intervertebral disc. The severity of the process is variable at
each level and may affect one or many levels.
Pathophysiology
Cervical spondylosis may produce pressure on the cord and/or roots. Anatomic and biomechanical factors
play a role in its production.
Anatomic factors include canal size, cervical curvature (lordosis or kyphosis), and blood supply to the cord.
Canal size may be congenitally or developmentally narrowed in association with conditions such as
achondroplasia, spine bifida, KlippelFeil syndrome, spondylolisthesis and congenital narrowing. Canal
narrowing may also be acquired secondary to rheumatoid arthritis, tumors, inflammation, ankylosing
spondylitis and cervical spondylosis. Narrowing alone is not problematic, but in the presence of a pathologic
condition which occupies space within the canal it increases the likelihood of the development of symptoms.
Lateral x-rays of the cervical spine can be used to assess the AP diameter of the spine. Pavlov's Ratio is the
relationship of the distance from the posterior aspect of the vertebral body to the anterior aspect of the
lamina to the AP width of the vertebral body. A value of 1 or greater is normal. 0.85 and lower is considered
abnormal. Edwards and LaRocca describe another measurement which incorporates measurement of both
normal and pathologic areas. A measurement of 17mm or greater at the mid vertebral body level is
considered normal. Narrow canals, less than 17mm are at risk for symptomatic spondylosis. Those with
"normal" canals can tolerate a spondylosis index of 3.3mm while those with narrow canals are only able to
tolerate an index of 2.2mm before becoming symptomatic.
There is no correlation between the sagittal curve and the degree of symptomatology; however there is
correlation between the curve and postoperative outcome. Patients with normal cervical lordosis do better
than those with kyphotic spines.
The blood supply to the spinal cord is through three longitudinal arteries and contributions from segmental
branches at each level. The anterior spinal artery may be compressed by osteophytes and or soft discs. The
two dorsolateral arteries may be compressed by infolded ligamentum flavum or facet osteophytes. The
segmental radicular vessels enter through the forarnina and may be compressed by uncovertebral or facet
osteophytes. It is felt that ischemia of the cord contributes to some degree to the signs and symptoms of
cervical spondylosis.
Histologic studies have demonstrated that clinical severity correlates with pathologic changes. In severe
cases white matter demyelination and tissue loss occur. Studies have demonstrated altered axoplasmic flow
and distortion of cord tissue. It is not known what contribution is made to the pathologic findings by the
effects of direct pressure on the neural elements and what is a result of ischemia.
Cervical spondylosis
Cervical spondylosis may present in three general categories of clinical presentation. It is important to
distinguish between the three as treatment and prognosis are different. Unfortunately the literature does not
always differentiate between them when reporting the results of various treatment modalities.
Cervical spondylotic radiculopathy
Cervical spondylotic radiculopathy is a condition in which there are signs and symptoms of compression of a
cervical nerve root. This may be caused by impingement by an uncovertebral or facet joint osteophyte or a
"soft" disc herniation.
Patients with radicular symptoms generally present with proximal pain, in the neck, interscapular region and
base of the skull, with concurrent arm weakness or sensory changes. Physical findings include motor
weakness, sensory changes and diminished reflexes in a radicular distribution.
Cervical spondylotic myelopathy
1
Cervical spondylotic myelopathy affects an older age group, typically over 55. The onset is insidious and the
course is one of intermittent symptoms and long periods of remission. Patients present with deep aching
and or burning neck pain. It is associated with motor and reflex changes commonly and sensory changes to
a lesser degree. Radicular signs and symptoms are rare. Presentation is typified by lower motor neuron
symptoms and signs at the involved level(s) and upper motor neuron findings below the level of the lesion.
Sensory changes are variable and are depend and upon the location of the offending lesion.
Cervical internal disc derangement
Cervical internal disc derangement presents with neck pain, subscapular pain and or subocciptal headache
without a radicular or myelopathic component. Discograms are positive.
In addition to intrinsic and extrinsic causes of pain in the neck and upper extremity, the differential
diagnosis should include multiple sclerosis, pancoast tumors and syringomyelia.
Long term longitudinal studies of the natural history of the various disorders is lacking. In general,
approximately 80% of patients with neck pain have a decrease in pain at 10 years, while approximately
40% are pain free and 32% have moderate to severe pain. Controversy arises regarding treatment because
the natural history is poorly delineated. It is known that patients with spondylotic myelopathy of long
duration do not return to baseline levels of functioning after surgery, while those with symptoms of short
duration do well when treated with timely surgical decompression. Further controversy arises regarding the
nature of the surgical procedure, anterior versus posterior, fusion versus no fusion, fixation versus none,
autogenous versus allograft bone graft and removal of anterior osteophytes versus not.
Anterior approaches to the cervical spine
Anterior approaches to the cervical spine have a low morbidity, leave a cosmetically acceptable scar, and
provide direct access to areas of most pathology. The potential for catastrophic complications exist to
greater degree than for posterior approaches. Surgical options include:
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Smith Robinson technique - disc excision with no decompression of the canal and a horsehsu graft.
Cloward technique - disc excision and canal decompression, and a dowel graft
Bailey/Badgley technique - disc excision without canal decompression, and onlay/chip graft.
Subtotal vertebrectomy and strut grafting with fibula (autogenous or allograft no difference in
fusion rates in some reports) with or without decompression and with or without internal fixation.
For patients with radiculopathy with symptoms traceable to an isolated root of less than one year's duration
who do not respond to conservative measures, a good result may be expected in approximately 70% in long
term follow up. Although there is some variation amongst different authors, these results are not dependent
upon the type of procedure performed.
The literature reports benefits from surgery in 70% to 80% of patients with cervical myelopathy, with better
results seen with early intervention. Again this is not technique dependent.
Posterior approaches to the cervical spine
Posterior approaches to the cervical spine avoid all of the potentially dangerous structures in the neck, are
less appealing to the eye but may be covered by hair and give results which do not appear to be different
from the anterior approaches. The kyphotic spine does not do well laminectomy, it provides little relief of the
anterior compression and destabilizes the spine. Surgical techniques include:
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Laminectomy alone
Laminotomy and foraminotomy
Laminaplasty
The surgical results in patients with OPLL are not as good as those with myelopathy due to spondylosis.
Approximately 10% of patients with OPLL are made worse with surgery, compared to 3% to 8% in
spondylotic myelopathy. Prospective, randomized clinical trials comparing different posterior approaches or
comparing anterior and posterior do not exist. The results are not significantly different when a number of
clinical series are compared. It is recommended that treatment be "individualized".
Bibliography
2
Batzdorf, U. Complex Cervical Myelopathies. in The Adult Spine: Principles and Practice. J.W. Frymoyer ed.
1991
Clark C.R. Degenerative Conditions of the Spine: Differential diagnosis and NonSurgical Treatment. in The
Adult Spine: Principles and Practice. J.W. Frymoyer ed. 1991
Dillin, W.H., Watkins, R.G. Clinical Syndromes in Cervical Myelopathy. in The Spine 3rd edition. R.H.
Rothman ed. 1992.
Ducker, T.B. Cervical Radiculopathies and Myelopathies: Posterior Approaches. in The Adult Spine: Principles
and Practice. J.W. Frymoyer ed. 1991
Hirabayashi, K., Satomi, K., Sasaki, T. Ossification of the Posterior Longitudinal Ligament in the Cervical
Spine. in The Cervical Spine. 2nd edition. H. Sherk, ed. 1989
Whitecloud III, T.S. Cervical Spondylosis: The Anterior Approach. in The Adult Spine: Principles and
Practice. J.W. Frymoyer ed. 1991
Schematic diagram depicting the measurements made on a plain lateral radiograph to determine Pavlov's
ratio. Pavlov's ratio = A/B
Schematic diagram depicting the developmental segmental sagittal diameter (DSSD, label A) and the
spondylotic segmental sagittal diameter (SSSD, label B). The spondylosis index (SI) is the difference
between the DSSD and the SSSD.
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In many cases of OPLL the pathology is as high as C2 and, therefore, the decompression needs to include
even C1.
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