Spinal tuberculosis

Synonyms: Pott's disease of the spine

What is spinal tuberculosis?

The usual sites to be involved in spinal tuberculosis are the lower thoracic and upper lumbar vertebrae.¹ The source of infection is usually outside the spine. It is most often spread from the lungs via the blood. There is a combination of osteomyelitis and infective arthritis.

Usually more than one vertebra is involved. The area most affected is the anterior part of the vertebral body adjacent to the subchondral plate. Tuberculosis may spread from that area to adjacent intervertebral discs. In adults, disc disease is secondary to the spread of infection from the vertebral body but in children it can be a primary site, as the disc is vascular in children.

It is the most common place for tuberculosis to affect the skeletal system, although it can affect the hips and knees too. The infection spreads from two adjacent vertebrae into the adjoining disc space. If only one vertebra is affected, the disc is normal; however, if two are involved the disc between them collapses, as it is avascular and cannot receive nutrients. Caseation occurs, with vertebral narrowing and eventually vertebral collapse and spinal damage. A dry soft tissue mass often forms and superinfection is rare.

How common is spinal tuberculosis? (Epidemiology)

• The epidemiology of tuberculosis is influenced by factors which include socio-economic development, lifestyle, geographic location and access to medical services.²

• Spinal tuberculosis is rare in the UK (notified cases have an incidence rate of 8.4 per 100,000 population)³ but elsewhere it represents about 50% of musculoskeletal tuberculosis.⁴

• Spinal tuberculosis accounts for around 1% of all cases of tuberculosis and around 15% of extrapulmonary tuberculosis cases.⁵

• Over 90% of tuberculosis occurs in developing countries; however, a global resurgence is also affecting developed countries.

• India, China,⁶ Indonesia, Pakistan and Bangladesh have the largest number of cases but there has been a marked increase in the number of cases in the former Soviet Union and in sub-Saharan Africa in parallel with the spread of HIV.

Risk factors

• Endemic tuberculosis.

• Poor socio-economic conditions.

• HIV infection.⁴

Spinal tuberculosis symptoms and presentation^{2 7}

Tuberculous spinal infections should be suspected in patients with an insidious, progressive history of back pain and in individuals from an endemic area, especially when the thoracic vertebrae are affected and with a pattern of bone destruction with relative disc preservation and paravertebral and epidural soft tissue masses.⁸

• The onset is gradual.

• Back pain is localised.

• Fever, night sweats, anorexia and weight loss.

• Signs may include kyphosis (common) and/or a paravertebral swelling.

• Affected patients tend to assume a protective, upright, stiff position.

• If there is neural involvement there will be neurological signs.

• A psoas abscess may present as a lump in the groin and resemble a hernia:
  

  • A psoas abscess most often originates from a tuberculous abscess of the lumbar vertebra that tracks from the spine inside the sheath of the psoas muscle.⁹

  • Other causes include extension of renal sepsis and posterior perforation of the bowel.

  • There is a tender swelling below the inguinal ligament and they are usually apyrexial.

  • The condition may be confused with a femoral hernia or enlarged inguinal lymph nodes.

• Spinal tuberculosis in children needs a particularly high index of suspicion for diagnosis.^{10 11}

Differential diagnosis⁷

• Pyogenic osteitis of the spine.

• Spinal tumours.

Investigations

• Elevated ESR.

• Strongly positive Mantoux skin test.

• Spinal X-ray may be normal in early disease, as 50% of the bone mass must be lost for changes to be visible on X-ray. Plain X-ray can show vertebral destruction and narrowed disc space.

• MRI scanning may demonstrate the extent of spinal compression and can show changes at an early stage. Bone elements visible within the swelling, or abscesses, are strongly suggestive of spinal tuberculosis rather than malignancy.

• CT scans and nuclear bone scans can also be used but MRI is best to assess risk to the spinal cord.

• A needle biopsy of bone or synovial tissue is usual.¹² If it shows tubercle bacilli this is diagnostic but usually culture is required. Culture should include mycology.

• All patients presenting with extrapulmonary tuberculosis should be offered a chest X-ray and, if possible, culture of a spontaneously-produced respiratory sample to exclude or confirm co-existing pulmonary tuberculosis. Site-specific tests to exclude or confirm additional sites of tuberculosis should also be considered.¹³

Associated diseases

• Tuberculosis co-infection with HIV has become common. It is up to 11% in some areas of the UK and over 60% in countries such as Zambia, Zimbabwe and South Africa.

• The disease is more common in certain sections of society such as those with alcohol dependency, the undernourished, ethnic minority communities and the elderly.

• The disease is also more common in patients after gastrectomy for peptic ulcer.

Distribution

• The most common area affected is T10 to L1.

• The lower thoracic region is the most common area of involvement at 40-50%, with the lumbar spine in a close second place at 35-45%.

• The cervical spine accounts for about 10%.

Spinal tuberculosis treatment and management

See also the separate Tuberculosis article.

• Medical treatment is the mainstay but surgical intervention may be required.^{12 14}

• The possibility of multiple drug-resistant TB should be considered.⁶

• Immobilisation of the spine is usually for two or three months.

• Surgery is reserved for select cases of progressive deformity or where neurological deficit is not improved by anti-tubercular treatment.¹⁵

• Multidisciplinary approaches to diagnosis and management can improve outcomes for both.¹¹

Surgical

Most patients affected by spinal tuberculosis can be successfully treated conservatively with chemotherapy, external bracing and prolonged rest. However, kyphotic deformity, spinal instability and neurological deficit are often associated with a conservative approach.¹⁶

• A Cochrane review found that routine surgery in addition to chemotherapy had not been shown to improve outcome but the problem was that the evidence was poor.¹⁷

• A study from India suggested that surgery is not mandatory.¹⁸

• In patients with spinal tuberculosis, referral for surgery should be considered if there is spinal instability or evidence of spinal cord compression.¹³

• Patients who present with a kyphosis of 60° or more (or a kyphosis which is likely to progress) require anterior decompression, posterior shortening, posterior instrumented stabilisation and anterior and posterior bone grafting in the active stage of the disease.¹⁹

Complications

• Progressive bone destruction gradually leads to vertebral collapse and kyphosis:¹²
  

  • The spinal canal can be narrowed by abscesses, granulation tissue, or direct dural invasion. This leads to spinal cord compression and neurological signs (including weakness and paralysis).

  • Kyphosis occurs because of collapse in the anterior spine and can be severe.

  • Lesions in the thoracic spine have a greater risk of kyphosis than those in the lumbar spine.

  • Neurological problems can be prevented by early diagnosis and prompt treatment. It can reverse paralysis and minimise disability.

  • A combination of conservative management and surgical decompression gives success in most patients.

  • Late-onset paraplegia is best avoided by prevention of the development of severe kyphosis.¹⁹

  • Patients with tuberculosis of the spine who are likely to have severe kyphosis should have surgery in the active stage of disease.

• A cold abscess can occur if the infection extends to adjacent ligaments and soft tissues. Abscesses in the lumbar region may descend down the sheath of the psoas to the femoral trigone region and eventually erode into the skin and form sinuses.

Prognosis

• The progress is slow and lasts for months or even years.

• Prognosis is better if caught early and modern regimes of chemotherapy are more effective.

• Poor prognosis is associated with complicated disease - ie those that exhibit instability, neurological deficit or deformity.⁷

• Diagnosis can be difficult and is often late. ^{6 11 12}

Prevention

See also Tuberculosis Prevention and Screening.

• As for all tuberculosis, BCG vaccination.

• Improvement of socio-economic conditions.

• Prevention of HIV and AIDS.