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Extrapulmonary tuberculosis, part 4: Skeletal involvement

Extrapulmonary tuberculosis, part 4: Skeletal involvement

In addition to causing significant pulmonary disease, Mycobacterium tuberculosis can cause a variety of extrapulmonary manifestations. In a series of articles, we have reviewed pleural, lymph node, neurologic, and abdominal tuberculosis. In this article, we will discuss tuberculosis that affects the spine and peripheral joints.


Skeletal tuberculosis is a hematogenous infection that can affect almost any bone. The infection can begin in either bone or synovium. Usually, an active focus forms in the metaphysis in children and in the epiphysis in adults.

The most common form of osteoarticular involvement is spinal tuberculosis. Lower thoracic and lumbar vertebrae are the most common sites, followed by middle thoracic and cervical vertebrae. Usually, 2 contiguous vertebrae are involved, but several vertebrae may be affected. Infrequently, skip lesions may occur.

After spinal tuberculosis, infection of the hip joint is the next most common form of osteoarticular tuberculosis. The knee joint is the third most common site of osteoarticular tuberculosis. The other peripheral joints are rarely involved.

Most patients with skeletal tuberculosis have pain at the joint of involvement, particularly on weight bearing. Most patients have constitutional symptoms, such as fever, for weeks before the development of joint pain.

In addition to the clinical presentation and findings on plain radiographs, CT or MRI can be helpful in making the diagnosis, especially in patients who have spinal tuberculosis and paraspinal abscess. When the diagnosis is in doubt, biopsy of the involved vertebrae or bone, for histopathologic and microbiologic examination, may be required. Concomitant pulmonary involvement can help establish the diagnosis, but it is not essential.


In spinal tuberculosis, the infection begins in the cancellous area of the vertebral body, commonly in the epiphysis. The vertebral body becomes soft and is easily compressed, producing wedging or total collapse. Anterior wedging is commonly seen in the thoracic spine, where the normal kyphotic curve accentuates the pressure on the anterior part of vertebrae. Wedging is minimal in the cervical and lumbar spine, where the center of gravity is posteriorly located because of lordotic curve.

Vertebral tuberculosis develops as an exudative lesion, which can penetrate the ligaments and follow the path of least resistance along fascial planes, blood vessels, and nerves from the original bony lesion to distant sites. In the cervical region, the exudate collects behind prevertebral fascia and may protrude as a retropharyngeal abscess.

The exudative lesionmay spread down the mediastinum or spread laterally into the sternomastoid muscle and form an abscess in the neck. In the thoracic spine, the exudate may remain confined locally for several months and may appear radiographically as a fusiform or bulbous paravertebral abscess.

The pressure may force the exudate to enter the spinal canal and compress the spinal cord. The exudate formed at lumbar vertebrae most commonly enters the psoas sheath. This manifests radiologically as a psoas abscess or clinically as a palpable abscess in the iliac fossa.

Pott's paraplegia is the most serious complication of spinal tuberculosis, occurring in almost 30% of patients. The dorsal spine is most commonly involved, since the spinal canal is narrowest in the dorsal region. Early-onset paraplegia develops during the active phase of infection. Paraplegia of late onset appears many years after the disease has become quiescent.

In most cases, early-onset paraplegia is caused by cord compression resulting from inflammatory edema, caseous material, tuberculous pus, and granulation tissue. The recovery is usually favorable. Late-onset paraplegia occurs as a result of long-standing persistent mechanical pressure. It includes internal gibbus, severe kyphotic deformity, dural fibrosis, and steno-sis of the spinal canal. The prognosis in these cases is much less favorable.1,2

Clinical presentation

Spinal tuberculosis typically occurs in the first 3 decades of life. It is also being reported in middle-aged patients. The protean constitutional symptoms precede the symptoms related to the spine. Localized pain over the site of involvement is the most common early symptom. This pain may worsen on movement. Careful palpation will reveal tenderness over the affected vertebrae.

In patients who do not present until vertebral wedging and collapse have occurred, a localized knuckle kyphosis is obvious, especially in the dorsal spine. Occasionally, patients with dorsal spine disease present very late with extensive vertebral destruction. These patients have deformity of the thoracic cage with a large gibbus.

Retropharyngeal abscess may cause local pressure effects, such as dysphagia, dyspnea, and hoarseness. A flexion deformity of the hip may result from psoas abscess. The abscesses may be visible and palpable if they are superficially located.

Rarely, paraplegia may be the presenting symptom. In most cases, however, the diagnosis of tuberculosis of the spine is already established when paraplegia develops. The earliest signs of neurologic involvement are spontaneous twitching of muscles in lower limbs, clumsiness in walking because of muscle weakness, and spasticity. Paraplegia in extension, paraplegia in flexion, sensory loss, and loss of sphincteric control may subsequently occur.1,2


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