1 Chronic lumbar ligamentous strain

This term is one of many used to describe the condition of persistent backache without demonstrable pathology. The condition is common in unskilled manual workers of both sexes and tends to recur with physical activity and to be work related. Depressive illness is a common association. The onset of the pain may also be dated from a specific injury, occasionally from an operation or from a past medical illness. The pain is diffuse, radiates widely but usually without definite anatomical features and tends to be worse on stooping and lifting. Usually, clinical examination yields no abnormal objective physical signs. Pain on straight leg-raising is variable. In nearly half the patients presenting with chronic back pain, a precise pathological diagnosis is not possible. In contrast to the diffuse pain of chronic back strain, patients with focal pathology usually have more localised pain at or near the site of the lesion. X-rays, CT and MRI are normal or a minor degree of spondylosis is seen. A rehabilitative approach is generally recommended, and often helpful.

A history of pain after lifting at work is common with chronic and recurring back pain. The WorkCover context complicates the situation considerably. Most patients still get better with rest, gentle activity and time. In those cases that pass into chronic pain, the significance of neurosis or malingering in the pathogenesis of this litigation-linked condition can rarely be determined with absolute assurance. True malingering in the sense of complete fabrication of a set of symptoms and signs is uncommon; exaggeration of symptoms and signs in the absence of demonstrable organic disease and persistence of symptoms and signs while litigation is pending is common.

2 Degenerative disc disease, spondylosis and osteoarthritis

With disc degeneration, especially following recurrent disc prolapse, gradual flattening of the disc and displacement of the posterior facet joints occur, eventually gives rise to osteoarthritis in those joints (Fig 5.2). A past history of lumbar pain is common, with subsequent recurrent attacks of pain over a period of several years. The onset of such attacks is often related to exertional trauma, such as repetitive bending or lifting a weight, or strain from sitting in an uncomfortable position during a long journey. Sciatic radiation of the pain to the buttock and sometimes down the backs of the legs, on one or both sides, is common. With the development of osteoarthritis of the facet joints, pain becomes constant and nocturnal. On examination, tender areas may be felt over the spine. There is limitation of all lumbar spine movements and residual neurological signs of disc prolapse, such as an absent ankle jerk, may be present. Most instances of chronic recurring back pain fall into this category; however, it is surprising how many patients have minimal symtoms despite impressive changes on scans.

Figure 5.2 Pathological sequence in degenerative back disease

A: normal lumbar vertebrae and disc; B: herniation of the nucleus pulposus; C: disc space degeneration and flattening with early osteoarthritis of the facet joint; D: advanced lumbar degenerative spine disease with facet joint osteophyte formation and compression of the nerve root. Forward slip and arthritis may also lead to narrowing of the spinal canal.

3 Spondylolisthesis

This term refers to displacement of one vertebra upon its neighbour. The two most common forms are lytic and degenerative. The lytic form occurs most commonly at L5/S1 due to lysis of the pars interarticularis of L5, allowing anterior displacement of L5 on S1. The posterior elements of L5 do not migrate forward. Therefore, there is no narrowing of the spinal canal, neither centrally nor in its lateral recesses. However, vertical narrowing of the foramen may occur as the condition progresses, which may lead to L5 nerve root impingement. The cause of the spondylolisthesis is debated, and may include non-union of the adjacent growth centres or stress fractures in early to mid-childhood.

The degenerative form of spondylolisthesis occurs as a late outcome of spondylosis, with a decline in structural integrity resulting in a ‘slip’. Since the centre of gravity of the body tends to lie anterior to the spinal column, the upper vertebra tends to slide forwards on the lower one, although the reverse may occur. There may be associated scoliosis. The slip may be stable or unstable, which has significant bearing on the symptoms. In this form of spondylolisthesis, the posterior elements migrate forwards, resulting in canal stenosis between the lower edge of the upper lamina and the upper edge of the lower vertebral body. This can lead to severe neurological symptoms or signs.

4 Osteoporosis

This condition is most common in elderly women; gonadal involution is the most important causal factor. Longstanding steroid therapy is an important cause, while nutritional problems may also contribute. Fractures, especially crush fractures of the vertebrae, can occur with minimal trauma. Trabecular bone stiffness varies with the cube of its density — there is almost 50% loss in strength with 30% decrease in the density. Vertebral compression fractures lead to backache, kyphosis and shortening in height. Plain X-ray reveals loss of bone density, wedging or biconcave indentation of vertebrae. Bone densitometry is a more sensitive and effective method of quantifying change in bone mineral density.

5 Secondary carcinoma of the vertebral body

The most common tumours of the vertebral bodies are metastatic lesions arising from tumours of the lung, breast, prostate, thyroid or kidney. The predominant symptom of localised destruction of the vertebral body is constant pain that steadily increases in severity. There may be associated neurological disorders because of involvement of the spinal cord or nerve roots. Plain X-ray may reveal osteolytic or osteosclerotic vertebral destruction by tumour, with preservation of an adjacent normal intervertebral disc (Fig 5.3). Metastases from carcinoma of the prostate are more commonly osteosclerotic. Considerable destruction of bone substance is necessary before radiological signs occur; X-rays are thus commonly negative in the presence of metastases. CT is more sensitive and MRI better again. Bone scans can be diagnostic. Furthermore, focal metastatic deposits can be difficult to differentiate from localised Paget’s disease.

Figure 5.3 Verterbral collapse

A: infection — the vertebral body appears intact because the infection usually lies adjacent to the disc; B: metastatic disease of vertebra leads to collapse with apparent preservation of the adjacent disc. Both conditions lead to kyphosis.

6 Spinal infection

Bacterial infections can occur in the discs of the spine, resulting in discitis. The patient can present in an acute septic state or with acute progressive back pain without overt features of sepsis. Subacute and chronic forms also occur, with gradual progression being a typical feature. Nocturnal pain may be prominent. The infection may spread, resulting in an epidural abscess that can cause rapidly progressive neurological damage. Paraspinal myositis with abscess formation may also occur. MRI, FBE, ESR and CRP may be diagnostic. Plain X-ray and CT may be falsely reassuring until late in the disease. Bone scan is useful if MRI is not available.

Tuberculosis of the spine is less common than in the past but should not be forgotten in the differential diagnosis of chronic back pain.

7 Referred pain

Abdominal and thoracic causes of back pain must not be forgotten. Patients with conditions as wide-ranging as lung carcinoma, pancreatitis, gallstones, abdominal aneurysms, gynaecological problems and rectal carcinoma can, on occasions, present with back pain as the major symptom. This will only be picked up by attention to associated symptoms and careful physical examination.

8 Less common causes

These include Paget’s disease, ankylosing spondylitis, tuberculosis and osteomyelitis.

Paget’s disease can cause back pain in older patients. The bones most commonly affected are the pelvis, vertebra, femur, tibia and skull. There may be a history of an increase in hat size. Most cases of Paget’s disease are asymptomatic. On X-ray the features are thickening and reduced density of the cortex, coarsening of the bony trabeculae and, later, a general increase in density of the affected bones.

Ankylosing spondylitis is an insidious, chronic inflammatory disorder of the spine and sacroiliac joints characterised by pain and stiffness with increasing lumbar kyphosis. The condition often starts in the sacroiliac joints and is manifest early by local tenderness of these joints. In the early phase, differential diagnosis can be difficult. Sciatica is a common symptom. On plain X-ray the earliest sign is osseous erosion at the anterior aspects of the vertebral bodies followed by a reparative process that leads to prominence of the anterior corners — ‘squaring off’. Erosion and fuzziness of the sacroiliac joints is also common. End-stage disease with bridging syndesmophytes gives rise to the characteristic picture of a bamboo spine.