Pott's Disease of the Spine

Synonyms: Pott's syndrome, Pott's caries, Pott's curvature, angular kyphosis, kyphosis secondary to tuberculosis, tuberculosis of the spine, tuberculous spondylitis and David's disease

Pott's disease is named after Percival Pott (1714-1788), who was a surgeon in London. Pott's disease is tuberculosis of the spinal column (must not be confused with Pott's fracture of the ankle).

• The usual sites to be involved are the lower thoracic and upper lumbar vertebrae.
• 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 commonest 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, but 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.

• Pott's disease is rare in the UK but in developing countries it represents about 2% of cases of tuberculosis and 40 to 50% of musculoskeletal tuberculosis.
• Tuberculosis worldwide accounts for 1.7 billion infections, and 2 million deaths per year.
• Over 90% of tuberculosis occurs in poorer countries, but a global resurgence is affecting richer ones.
• India, China, 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.
• About two thirds of affected patients in developed countries are immigrants, as shown from both London¹ and Paris² and spinal tuberculosis may be quite a common presentation.
• The disease affects males more than females in a ratio of between 1.5 and 2:1. In the USA it affects mostly adults but in the countries where it is commonest it affects mostly children.

Risk factors

• Endemic tuberculosis.
• Poor socio-economic conditions.
• HIV infection.

• 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.
  • 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.

• Pyogenic osteitis of the spine.
• Spinal tumours.

• 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 Pott's disease 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. If it shows tubercle bacilli this is diagnostic but usually culture is required. Culture should include mycology.

• 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.
• In the developed world, the disease is more common in certain sections of society such as alcoholics, the undernourished, ethnic minority communities and the elderly.
• The disease is also more common in patients after gastrectomy for peptic ulcer.

• The commonest area affected is T10 to L1.
• The lower thoracic region is the most common area of involvement at 40 to 50%, with the lumbar spine in a close second place at 35 to 45%.
• The cervical spine accounts for about 10%.

• Immobilisation of the spine is usually for 2 or 3 months.
• Drug treatment: this is covered in the article on the Management of Tuberculosis. Therapy may need to exceed 6 months.

Surgical

• Surgery plays an important part in the management. It confirms the diagnosis, relieves compression if it occurs, permits evacuation of pus, and reduces the degree of deformation and the duration of treatment.³
• However, 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.⁴
• A study from India suggested that surgery is not mandatory.⁵

• Progressive bone destruction leads to vertebral collapse and kyphosis:
  • The spinal canal can be narrowed by abscesses, granulation tissue, or direct dural invasion. This leads to spinal cord compression and neurological signs (Pott's 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.
  • Patients with tuberculosis of the spine who are likely to have severe kyphosis should have surgery in the active stage of disease.⁶
  • The degree of kyphosis, the area of affected vertebrae and the lack of sphincter control all correlate with the chance of recovery from paraplegia.⁷
• 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.

• 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.
• A study from London showed that diagnosis can be difficult and is often late.¹

• As for all tuberculosis, BCG vaccination.
• Improvement of socio-economic conditions.
• Prevention of HIV and AIDS.

1. Cormican L, Hammal R, Messenger J, et al; Current difficulties in the diagnosis and management of spinal tuberculosis. Postgrad Med J. 2006 Jan;82(963):46-51. [abstract]
2. Pertuiset E, Beaudreuil J, Liote F, et al; Spinal tuberculosis in adults. A study of 103 cases in a developed country, 1980-1994. Medicine (Baltimore). 1999 Sep;78(5):309-20. [abstract]
3. Ghadouane M, Elmansari O, Bousalmame N, et al; Role of surgery in the treatment of Pott's disease in adults. Apropos of 29 cases. Rev Chir Orthop Reparatrice Appar Mot. 1996;82(7):620-8. [abstract]
4. Jutte PC, Van Loenhout-Rooyackers JH; Routine surgery in addition to chemotherapy for treating spinal tuberculosis. Cochrane Database Syst Rev. 2006 Jan 25;(1):CD004532. [abstract]
5. Nene A, Bhojraj S; Results of nonsurgical treatment of thoracic spinal tuberculosis in adults. Spine J. 2005 Jan-Feb;5(1):79-84. [abstract]
6. Jain AK; Treatment of tuberculosis of the spine with neurologic complications. Clin Orthop Relat Res. 2002 May;(398):75-84. [abstract]
7. Cabrera Orduna A; Surgical management of Pott's paraplegia. Bol Med Hosp Infant Mex. 1980 Nov-Dec;37(6):1141-53. [abstract]

• Percival Pott; Brief biography on whonamedit.com.
• MRI of Pott's disease
• Tuberculosis, NICE Clinical Guideline (March 2006); Clinical diagnosis and management of tuberculosis and measures for its prevention and control
• Immunisation against infectious disease - 'The Green Book', Department of Health (various dates)