22 Cervical and lumbar spine

Essential facts

1. Intervertebral disc degeneration is a normal finding in people over the age of 40 years; radiographic abnormalities of disc space narrowing and bone spurs around the discs and facet joints have little clinical relevance.

2. Cervical cord compression can present in young to middle-aged patients due to disc herniation, but it is more likely to occur in older patients due to bone thickening around degenerate joint margins.

3. Atlanto-axial involvement occurs in 50% of patients with rheumatoid arthritis (RA) who have neck problems, but all levels can be affected, from occiput to cervico-thoracic junction.

4. Mechanical pain or ‘simple back pain’ occurs in 80% of the population; 80% will resolve spontaneously within 6 weeks and in 80% no clear cause can be identified.

5. Radiological investigation of back pain is most helpful in patients aged over 50 years (looking for metastases), in those aged under 20 years (looking for adolescent disc herniation, spondylolysis or benign tumour), or if inflammatory spinal disease is suspected.

6. The following are ‘red flag’ features of back pain: violent trauma; constant, progressive non-mechanical pain; thoracic pain; presentation under 20 or over 55 years of age; previous history of carcinoma; use of systemic steroids; drug abuse or HIV infection; systemically unwell; weight loss; lumbar stiffness; widespread neurological signs; and structural deformity.

7. Some 90% of disc herniations resolve spontaneously by dehydration and resorption of herniated material; the diagnosis is clinically obvious and there is no benefit in rushing to special investigations.

Spinal anatomy

The spine consists of 7 cervical, 12 thoracic and 5 lumbar vertebrae, plus the sacrum and coccyx. Since adopting the upright posture, the human spine has acquired secondary lordotic curves in the cervical and lumbar regions either side of the primary thoracic kyphosis. The degenerative conditions of the spine tend to occur in these lordotic areas, and the thoracic spine is rarely the source of back pain. At each level of the spine there is a motion segment, comprising two adjacent vertebrae, the intervertebral disc, a pair of zygo-apophyseal synovial joints (facet joints) and the supporting ligament complexes. The spinal cord occupies the adult spinal canal down as far as the L1–2 level, and below this the lumbar and sacral nerves form the cauda equina (horse’s tail), which floats in the cerebrospinal fluid occupying the lower end of the theca (meningeal sac).

Degenerative conditions of the cervical spine

Cervical pathology is largely due to degenerative disease. Intervertebral disc degeneration is the norm over the age of 40 years and radiographic evidence of disc space narrowing and bone spurs around the margins of the discs and facet joints has little clinical relevance. The presence of disc herniations or osteophytes can cause nerve pain that is felt down the arm (brachialgia) with altered sensation in the corresponding dermatome and weakness in the corresponding myotome. The commonest level affected is C5/6; this affects the sixth cervical nerve (C6) so that there is numbness in the dermatome affecting the index finger and thumb, weakness of the biceps muscle and a reduced biceps reflex. The C6/7 level is the second commonest and presents with seventh cervical nerve compression symptoms and signs (Fig. 22.1). Pain is reproduced by lateral rotation to the symptomatic side (Spurling’s sign) or with axial compression produced by pressure on the patient’s head.

FIGURE 22.1 T2-weighted magnetic resonance images showing two consecutive sagittal views and an axial view. There is a herniated disc at C6/7 occluding the exit foramen for the right 7th cervical nerve

Most cervical nerve compression symptoms improve with time, but there is a place for physiotherapy, non-steroidal anti-inflammatory drugs (NSAIDs) and epidural steroid injections. The best investigation is magnetic resonance imaging (MRI) (Fig. 22.2). Because pathology is common, even in subjects who have no symptoms, the scan findings must be carefully correlated with the clinical findings. In cases where the symptoms fail to improve with time and conservative treatment, a cervical discectomy can be performed. This procedure is carried out through an anterior approach, which gives excellent access to the intervertebral disc. The disc is excised completely and, after decompression of the affected nerve, the level is usually fused using a bone graft from the iliac crest or a bone substitute, such as tricalcium phosphate (Fig. 22.3). The procedure is usually straightforward and excellent results can be achieved. There is a risk of damage to the recurrent laryngeal nerve, which can induce hoarseness. The airway needs careful observation afterwards and a drain is used to reduce the risk of haematoma formation.

FIGURE 22.2 Magnetic resonance imaging of T2 sagittal and axial views through cervical stenotic segment showing a disc and osteophyte complex causing flattening and compression of the spinal cord

FIGURE 22.3 Post-operative lateral radiograph of the cervical spine after anterior discectomy and spinal fusion using a ceramic block as a bone substitute and a cervical plate and screws to secure the ‘graft’ and immobilize the C6/7 level

Cervical myelopathy

Cervical cord compression can present in young to middle-aged patients due to disc herniation, but is much more likely to occur in older patients due to bone thickening around degenerate joint margins. The stenosis develops insidiously without any pain. Unfortunately, its silent, gradual onset is often responsible for the patients presenting very late. They may have upper motor neurone weakness of all four limbs. The hands become clumsy, especially for fine tasks, such as button-fastening and writing. Rapid fist clenching is impaired (‘dysdiadochokinesia’ or clumsiness in performing alternating rapid hand movements). The Hoffmann sign may be present – thumb flexion in response to flicking the middle finger distal interphalangeal joint into extension. Lower-limb involvement results in spasticity and an ataxic, scissoring gait. Sensation is impaired, reflexes are brisk, plantar reflexes are extensor, and there may be clonus of ankles and knees (rhythmical contraction of muscle in response to a suddenly applied and sustained stretch stimulus). MRI confirms the presence of cord compromise due to canal narrowing. Surgical decompression is indicated to prevent the loss of hand and lower-limb function. Operations for single- or double-level stenosis are usually carried out anteriorly, but multi-level stenosis may be better treated by a posterior approach involving removal of the laminae. The Japanese are genetically prone to develop ossification of the posterior longitudinal ligament (OPLL), so stenosis is common in Japan and their surgeons have led the way in devising new techniques, such as laminoplasty and skip laminectomy, to allow decompression with minimal compromise of spinal stability.

Rheumatoid arthritis of the cervical spine

Cervical rheumatoid disease (RA) occurs in patients with severe peripheral joint involvement. Proliferation of synovial pannus causes erosion and destruction of the small joints in the cervical spine. In 50% of patients with rheumatoid disease of the neck, the atlanto-axial articulation is involved, but the disease can affect all levels from occiput to cervico-thoracic junction. Pannus around the odontoid peg damages the transverse ligament and creates atlanto-axial instability. The patient may be aware of mechanical clunking in movements involving flexion and extension of the neck, and may become reliant upon a collar or in the worst cases hold their own head to limit the unpleasant movements that are accompanied by pain and sometimes by electric shock sensations up into the head and down the back (‘Lhermitte’s phenomenon’, which is not pathognomonic of spinal cord compression and can also occur in demyelinating disorders, such as multiple sclerosis). However, in others, the neck instability and spinal cord damage may be silent and impaired limb function may be erroneously attributed to the peripheral joint disease until the spinal cord damage is irreversible.

Cord dysfunction develops and manifests as impairment of hand function and heavy legs. If unchecked, the patient becomes a wheelchair-user and the condition may even cause sudden death (see Chapter 1). Plain radiographs look unremarkable, but flexion/extension views (Fig. 22.4) unmask the instability and show excessive movement of the atlas on the axis (>3 mm). The condition is treated by posterior fusion of C1/2 with bone grafting and internal fixation using wires, screws or a combination of these methods.

FIGURE 22.4 Plain lateral radiographs of a rheumatoid cervical spine showing atlanto-axial instability before and after reduction, posterior cable wiring and bone grafting

Much less commonly there is occipito-cervical joint involvement with ‘cranial settling’, a condition where the skull base descends on to the cervical spine and the odontoid peg penetrates through the foramen magnum causing pressure on the medulla oblongata. This condition presents with brainstem dysfunction, including dysarthria, dysphagia and diplopia due to cranial nerve disturbance. It is potentially fatal and requires occipito-cervical fusion employing metal plates and screws from the skull extending the full length of the cervical spine. Sometimes the odontoid peg and pannus have to be removed before the posterior stabilization can be performed safely; this is done through a trans-oral approach to C1 and C2.

The Ranawat grading of myelopathy is the most commonly used method for assessing the severity of cervical spine involvement and the outcome after treatment (Box 22.1). Operative treatment does not reverse the neurological effects fully, but it is often possible to produce improvement by one Ranawat grade. Although myelopathy is the most compelling reason to operate on the cervical spine, patients without neurological compromise may require operative treatment for painful instability.

Box 22.1

Ranawat grading of cervical myelopathy