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PH-MS10

Tuberculosis and other specific infections of bone and joint

How granulomatous (“specific”) infections destroy bone slowly: tuberculosis of the spine with gibbus, cold and psoas abscesses, tuberculous joints, skeletal syphilis from sabre tibia to gumma, and brucellar and fungal bone infection.

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  • 3D normal anatomy

By the end, you can

  • Explain how caseating granulomas destroy bone differently from pyogenic infection, and why their abscesses are cold.
  • Describe how Pott disease spreads between vertebrae and leads to a gibbus, cold and psoas abscesses and paraplegia.
  • Relate the slow, marginal destruction of a tuberculous hip or knee to its X-ray appearances and its outcome.
  • Describe the skeletal lesions of congenital and acquired syphilis and how periostitis and gummas form them.
  • Outline brucellar spondylitis and fungal bone infection, including mycetoma, and how each is told apart.
  • Recognise the classic appearances and tests examiners ask about, and explain how antituberculous drugs, surgery, penicillin, antibiotics and antifungals act.

What it is

Specific infections of bone and joint are those that cause granulomatous inflammation, distinctive enough to point to the organism: above all tuberculosis, and also syphilis, brucellosis and fungi. Unlike pyogenic (“non-specific”) infection, they destroy bone slowly, with little pus, little new bone and cold abscesses.

4 types to tell apart
Tuberculosis of the spine (Pott disease)
The commonest form of skeletal tuberculosis: destruction of neighbouring vertebral bodies, with a gibbus, cold abscesses and sometimes paraplegia.
Tuberculosis of joints and other bones
Usually one large weight-bearing joint (hip or knee), with slow marginal destruction; also tendon sheaths and, after injury, the bones of the hand and wrist.
Skeletal syphilis
Congenital (osteochondritis and periostitis in infancy; sabre tibia and saddle nose later) or acquired (periostitis in secondary syphilis, gummas in tertiary syphilis).
Brucellar and fungal bone infection
Brucellosis favours the sacroiliac joints and lumbar spine; fungi cause rare granulomatous bone infection, and mycetoma destroys the foot over years.

Normal function

The vertebral column and its blood supply

Seen from the side, the column curves gently: forward in the neck and lower back, backward in the chest. The weight of the body passes down the front column, the stack of vertebral bodies, such as , and the discs between them, such as the between L4 and L5; the vertebral arches behind them carry the joints and enclose the spinal cord.

Each vertebral body is mostly spongy bone filled with red marrow, richly supplied by segmental arteries that branch to the endplates above and below each disc. Its veins join a valveless plexus round the column that also drains the pelvis and abdomen, so organisms can reach the vertebrae from many sites. The adult disc has no blood vessels and is fed through the endplates.

Strong ligaments bind the bodies: the anterior longitudinal ligament down their front, the posterior longitudinal ligament behind them in the canal. The psoas major arises from the sides of the lumbar bodies and discs and runs down to the thigh. Organisms that survive inside macrophages, such as mycobacteria and Brucella, are not cleared by neutrophils; T cells and macrophages wall them off in granulomas, as in the lung.

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