Degenerative diseaes of the spine

  Introduction

Pain due to degenerative disease of the cervical and lumbar spine is very common in the general population. A wide variety of terms is used describing this, including lumbago, wear and tear, spondylosis and a slipped disc. What is clear is that parts of the spine are subject to a series of changes in both the intervertebral disc and the adjacent vertebrae. They are associated with local pain and may be associated with the compression of the spinal cord or nerve root. It is also apparent that these changes occur with age. MRI scanning has provided excellent evidence of this disc degeneration, with loss of water content, these changing often without associated pain (see Fig. 33.15). Thinning of the annulus and the appearance of radial slits allow the nucleus to bulge —and may eventually rupture through causing disc prolapse. Progressive collapse of the disc space may allow additional movement, putting extra strain on the apophyseal joints, in which secondary degenerative changes occur with associated ligamentous hypertrophy. Osteophyte formation, due to calcification of the bulging peripheral fibres of the annulus, leads to further narrowing of the spinal, or root exit, canal.

Neurological involvement can therefore occur due to cord, cauda equina or toot compression by soft disc, ligamentous hypertrophy or osteophyte formation.

Cervical degenerative disease

Two patterns emerge.

 1. Cervical radiculopathy. Neck and radicular pain in the arm with, on examination, signs of a lower motor neuron lesion usually affecting C6 or C7. Functional changes and pins and needles may be apparent, the arm pain being the predominant symptom (see Fig. 33.16).

2. Cervical myelopathy. Pain and stiffness in the neck with a gritty feeling in the tips of the fingers. Patients will complain of stiffness and a loss of dexterity, with unsteadiness of gait.

The symptoms are usually slowly progressive with, on examination, signs of an upper motor neuron lesion with a glove and stocking distribution sensory loss. The neck pain may not be a major feature. Examination will usually reveal a restricted range of cervical spine movement (see Fig. 33.17).

Commonly seen in the midcervical region, signs of radiculopathy at the affected level may be superimposed. Presence of the deltoid jerk suggests compression above the C4/5 level.

Investigation

Following a careful history and examination to define the pattern of neurological compromise and the clinically affected level, plain X-rays in flexion and extension with an MRI represent the investigations of choice. Cervical myelo­graphy is rarely performed, but CT myelography may be helpful if MRI is not available.

Plain X-rays provide details of the bony architecture and evidence of osteophyte formation. Instability can be seen and measured (see Fig. 33.18). MRI in sagittal and axial views allows detailed study of the spinal cord — including changes within the cord itself — together with views of the exiting nerve roots and root canals. MRI does not provide ‘dynamic’ information about the cervical spine and should be used in conjunction with plain X-rays in flexion and extension (see Fig. 33.19).

  Differential diagnosis

For cervical radiculopathy the diagnosis is usually apparent. The differential includes cervical rib, producing a T1 syndrome, ulnar or median nerve entrapment syndromes, meta­static disease in the cervical spine, or even direct brachial plexus involvement via an apical lung tumour (Pancoast syndrome).

For patients with a myelopathy, clearly other causes of spinal cord compromise rarely occur, but should be considered. These include an intraspinal tumour, infection or instability associated with conditions such as rheumatoid arthritis. Beware the tumour at the level of the foramen magnum leading to wasting of the small hand muscles.

Management

Radiculopathy. In over 75 per cent of patients the symptoms will resolve with conservative measures, including rest, analgesia, the use of a cervical collar and physiotherapy by an experienced therapist. Physical therapies are becoming increasingly specialised and appropriately timed treatments will usually produce good results.

Care should be taken with cervical collars. A short-term support can become a long-term crutch. Their length of use should be avoided.

Surgery is indicated according to the duration and severity of the pain, physical signs, the radiological appearances and most importantly  the patient’s wishes. A good history with physical signs and corresponding radiological changes, and providing a good decompression is achieved, will produce good results.

To effect decompression of the nerve root, either an ante­rior cervical discectomy approach can be used, or posterior foraminotomy. For soft disc prolapse causing nerve root compression, an anterior approach is most frequently used.

Myelopathy. There is much debate about how and when to proceed to surgery. The aim of the operation is to prevent further deterioration. If there is improvement, then this is to some extent a bonus and it is important that the patient and their family are advised of this. Despite decompression, in 30 per cent of patients there will be further deterioration, probably due to vascular changes within the cord itself.

Surgical decompression is, therefore, appropriate for those who are deteriorating, whose symptoms interfere with normal activity; and are accepting of the risks of the procedure.

The aim is to decompress the spinal cord and maintain or establish stability. This can be done by an anterior or a posterior approach to the spine. Anterior approach requires removal of soft disc, osteophytes and hypertrophied liga­ments, often over multiple levels. Fusion, intervertebral grafts or onlay plates can then be achieved.

A posterior cervical laminectomy provides easy access to decompress the spine over multiple levels and great care must be taken to avoid spinal cord injury. The decision between anterior and posterior approaches depends again on the pathology, the presence of instability and the experience of the surgeon.

The advantages and disadvantages of the two approaches are considered in Table 33.3.

Inflammatory disorders involving the cervical spine

Rheumatoid arthritis

This commonly affects the spine and particularly the cervical spine. Patients often present with stiffness and pain in the neck, and some patients present with neurological symptoms due to compressive myelopathy in the neck. Diseases in the joints in turn lead to soft-tissue destruction and then instability.

The three common abnormalities are:

atlantoaxial subluxation;

proximal migration of the odontoid with basilar impression;

lower cervical spine subluxations.

 Investigation with flexion and extension radiographs of the neck and MRI scan allow assessment of stability and cord compression. A certain number of patients may require decompression of the spinal cord and appropriate stabilisation. Anterior decompression (transoral), fusion and instrumentation may be appropriate with localised disease. This may be necessary in either the lower or the upper cervical spine (see Fig. 33.20a—c).

Ankylosing spondylitis

This is relatively uncommon, but can present with painful stiffness of the spine. It is more common in males, most of whom will be human leucocyte antigen (HLA) B27 positive. Other inflammatory markers will be raised. In general phy­siotherapy combined with anti-inflammatory drugs will con­trol symptoms adequately. However, severe deformities will occasionally be seen and these may require major surgery to the spine to effect correction. Occasionally patients with ankylosing spondylitis will present after minor trauma with unstable fractures. These patients should be assumed to have an unstable injury until this has been excluded. Surgical stabilisation leads to satisfactory results in most cases.

Thoracic spinal degenerative disease

This is rare. Thoracic disc is the commonest form of degenerative thoracic disease that requires surgery.

Presentation

More common in males (5:3 ratio) and usually in the lower thoracic spine, the patients may present with a history of injury but this usually occurs spontaneously.

Pain may not be a major feature. The symptoms will progress very rapidly over a few days, or may occur insidiously over years. The presenting features are those of progressive spinal cord compression with, initially, often dissociating signs, but if undiagnosed will finally progress to a paraplegia with a sensory level, to loss of sphincter function.

Investigation

Plain X-ray may reveal calcification in the disc at the affected level, with calcification of the protruding disc visible.

CT scan. As part of a CT myelogram, this will confirm the epidural compression at the level of the disc prolapse.

MRI scan remains the investigation of choice. Be aware of the level of the disease and whether it is lateral or central (see Fig. 33.21a and b).

Management

Removal of a thoracic disc represents a very different operation to that of cervical or lumbar disc. The prolapse can be hard and calcified or occasionally soft and liquid, appearing like pus. The dura may even be eroded.

A standard laminectomy is dangerous and a lateral or anterior transthoracic approach is required to excise these lesions.

If truly central, a transthoracic route, with drilling out of the vertebral body above and below the level of the disc prolapse, will allow piecemeal removal of the disc and decompression of the spine.

For the laterally placed discs a costotransversectomy with division of the paravertebral muscles and excision of the rib head provides good access, again drilling away the vertebral bodies above and below the disc to allow its removal. Check the levels very carefully by preoperative and/or peroperative imaging and warn the patient, especially about the risks of paralysis due to surgery.

Lumbar spine

Degenerative disease of the lumbar spine is almost universal with increasing age. The disc ages owing to deterioration of the proteoglycan within the disc, which becomes dehydrated as a result. Therefore the disc becomes narrower and this in turn narrows the nerve root canals where the lumbar nerve roots exit from the spinal canal. Secondary changes also occur in the facet joints with loss of joint space, sclerosis and osteophyte formation.

      Between 70 and 90 per cent of individuals will experience back pain at some point in their lives. The commonest site of pain in the spine is the intervertebral disc. Although the central part of the disc has no nerve supply, the annulus is very sensitive and is often a source of pain. Degeneration tears often occur in the annulus and these can be a source of pain.

Neurological symptoms can also occur as a result of degen­erative disease in the spine. Tears of the annulus can allow part of the nucleus pulposus to herniate through the annulus. The weakest part of the annulus is the postero-lateral corner, and as a result the nerve root is often compressed in the can also occur and this can result in compression of the cauda equina which lies in the midline throughout most of the lumbar spine. This can cause cauda equina compression with loss of bowel and bladder function. If this occurs, urgent surgical decompression is indicated.

Another effect of degeneration is that spinal stenosis can occur due to a combination of narrowing of the disc, osteophyte formation from the joints and thickening of the ligamentum flavum. The stenosis can either be central, lateral around the exiting nerve roots or a combination of the two. Most patients with spinal stenosis are elderly but some patients present young, and the majority of these has devel­opmental spinal stenosis where the spinal canal is narrow from birth.

Presenting symptoms

Back pain is usually felt in the lumbar area and may radiate to the buttocks and the back of the thighs. If the pain is coming from the upper lumbar region, it may radiate to the front of the thigh. Pure back pain very seldom radiates below the knees. Patients will often complain of spinal stiffness and of difficulty in the activities of daily living such as picking things up, shopping, sitting, walking, running and so on. Back pain can occur in any age group, but beware of the child with back pain because it is likely that there is some more serious underlying condition (see above). Other features of back pain which are worrying include night pain which prevents sleep or unremitting pain which cannot be con­trolled with pain relief. Spinal tumour or spinal infection must be excluded in these patients.

Disc prolapse

Disc prolapse occurs most commonly in middle age although it can occur in adolescence and in the elderly. The typical history is of an episode of back pain either related to lifting and/or twisting or which occurs spontaneously. Eighty per cent of disc prolapses occur in the lumbar spine, the majority at L5/S1 (see Fig. 33.22) and at L4/L5. The back pain commonly lasts for 2—6 weeks and may continue for longer. The back pain will often improve then but is followed almost immediately by sciatica or nerve root pain. The pain will usually follow one or more dermatomes, and is often associated with neurological symptoms, altered sensation and weakness in the muscles innervated by the compressed nerve roots. Serious neurological symptoms may he an indication for urgent surgery to decompress the nerve roots, but in general a period of waiting is best because 90 per cent of patients will have relief of their pain within 6 weeks. Minor degrees of weakness and numbness will usually improve with time and may resolve completely. Motor weakness is more likely to recover than sensory change.

Spinal stenosis

Spinal stenosis presents typically in the elderly patient and tends to develop gradually (Fig. 33.23). The patient may develop back pain, especially standing and walking, which is associated with neurological symptoms in the legs. Patients report pain, weakness and numbness in the legs on standing or walking, and their walking distance is usually limited. They may complain that their legs go rubbery or tend to give way. Their symptoms usually resolve with rest, especially sitting down for 5—10 minutes, and then they can continue. They often report fewer symptoms going up hill or walking using a rollator or a shopping trolley. The reason for this is that the spinal canal is made wider with spinal fiexion. This helps to differentiate these patients from those with vascular claudication who find it worse uphill. Usually the symptoms of vascular claudication will be relieved more rapidly.

Treatment

The majority of patients with back pain can be treated with physical treatments such as physiotherapy, chiropractic, or the various other treatments available. Explaining to the patient that they have a nonprogressive condition which is very common will help them to cope with the symptoms. Medications such as analgaesics and anti-inflammatories can also be used. Adjustments to work situations (e.g. seating) and to day-to-day life (e.g. less driving, more physical activity, weight loss) are often much more effective that other measures. A small proportion of patients will develop more severe symptoms which require more intensive physical treatments such as rehabilitation. Surgery to fuse or stabilise the spine is a last resort, and should only be used in selected patients where less invasive methods have been used. Combined anterior—posterior surgery probably has the best results in these patients.

Disc prolapse

Disc prolapse usually resolves within 6 weeks, and simple pain relief may be all that is required in these patients. Longitudinal studies have demonstrated that most of these disc prolapses will resolve with time.

Patients with evidence of cauda equina compression must be managed as an emergency.

 Symptoms suggestive of this are:

  very restricted straight leg raising bilaterally;

numbness in the perineum;

  inability to void or difficulty voiding urine;

inability to have or difficulty in having bowels open;

  lax anal sphincter;

  severe pain.

  Not all of these signs are necessarily present in each patient. Emergency MRI scanning or, if not available, CT scan or myelogram will confirm the diagnosis, and treatment is surgical decompression and partial discectomy.

In the patient with simple sciatica various options are available.

Epidural steroid injection — about 30 per cent success rate, low complication rate, day-case procedure.

  Chemonucleolysis (injection of chymopapain into the disc itself) — about 70 per cent success rate, day case or overnight stay. Often causes back pain in the early stages. May take some weeks to be effective. Low complication rate, occasional anaphylactic reaction to the chymopapain.

  Laser discectomy (laser coagulation of the disc) — success rate 50—70 per cent, less back pain than chemonucleolysis, day-case procedure, low complication rate.

   Microdiscectomy — success rate 80—90 per cent. Three per cent long-term complication rate (e.g. nerve damage, infection, long-term back pain). Requires hospital admis­sion for a few days. Longer convalescence.

  Standard discectomy — as for microdiscectomy, but longer scar, longer in hospital, longer recovery.

          There is no reason in most cases why closed techniques cannot be used initially and then open surgery used if other methods fail. In older individuals associated spinal stenosis is common and open techniques are more likely to be effective.

Many patients with spinal stenosis are elderly, and nonsurgical methods of treatment may be better for some. Various treatments have been used with fairly low success rates such as lumbar corset, epidural injection of steroids and traction. Physiotherapy with flexion exercises can be helpful in a minority of patients. Calcitonin has been used with some success for treating spinal stenosis, particularly in the elderly who may not be fit for surgery. One-hundred international units of calcitonin are given by intramuscular (i.m.) injection 4 days a week for 4 weeks. Success rates of 20—3 0 per cent have been reported, but to date there has not been a randomised trial to assess the treatment.

Surgery is effective in about 70 per cent of patients with spinal stenosis. Decompression of symptomatic nerve roots and central stenosis can give very effective relief.

Spondylolisthesis

Spondylolisthesis is a common condition and is usually caused either by spondylolysis or by degenerative change (Fig. 33.24). Spondylolysis is a defect in the bone in the pars interarticularis, and causes a slip between one vertebra and another in some cases. It is present in about 6 per cent of the normal population, is usually asymptomatic and is a common incidental finding. In young individuals presenting with back pain nonoperative measures such as physiotherapy are usually successful in resolving pain, and occasionally a plaster jacket can resolve symptoms. Indications for surgery include non-resolving and serious pain or progressive slip between the two vertebrae. If the spondylolysis is undisplaced and the intervertebral disc at that level is normal, direct repair by bone grafting and internal fixation can be carried out. Otherwise fusion of the motion segment is required. In children internal fixation is seldom required but in adults most surgeons use fixation with inter-pedicular screws.

Degenerative spondylolithesis is common in the elderly and occurs owing to degeneration of the disc and the asso­ciated facet joints. It can be associated with spinal stenosis, and if decompressive surgery is contemplated, it is usually best to carry out an un-instrumented fusion to prevent progression of the slip.