Tuberculosis is a global bacterial infection caused by Mycobacterium tuberculosis, primarily known for attacking the lungs. The bacteria can circulate through the bloodstream to infect other organs and tissues, a condition known as extrapulmonary tuberculosis (EPTB). Skeletal tuberculosis (osteoarticular TB) is a specific and potentially severe type of EPTB where M. tuberculosis establishes an infection in the bones or joints. Because its symptoms are often subtle and slow to develop, diagnosis and treatment are frequently delayed.
Understanding Skeletal Tuberculosis and Disease Progression
Skeletal tuberculosis is typically a secondary infection resulting from the reactivation and spread of a primary infection, often dormant in the lungs or lymph nodes. The bacteria travel to the bone tissue through hematogenous spread, using the bloodstream to reach the highly vascularized metaphysis of long bones or the vertebrae. Once M. tuberculosis reaches the bone, it triggers a localized inflammatory response and the formation of granulomas.
The spine is the most frequent site of skeletal involvement, accounting for approximately half of all musculoskeletal TB cases (historically known as Pott’s disease). The infection commonly starts in the anterior part of the vertebral body and spreads to the adjacent intervertebral disc space. This destructive process involves caseous necrosis, a form of cell death characteristic of TB, which destroys bone and joint tissue. This destruction severely weakens the vertebrae, leading to collapse and spinal deformity.
Identifying Common Signs and Symptoms
Symptoms of skeletal tuberculosis are often insidious, developing slowly and vaguely, which makes early recognition difficult. The most common complaint is localized back pain, which is typically chronic and worsens gradually. This pain is often accompanied by stiffness in the affected spinal segment, limiting the patient’s range of motion.
When the spine is involved, vertebral destruction can lead to kyphosis (a hunchback deformity). If vertebral collapse causes compression of the spinal cord or nerve roots, neurological complications can arise, including muscle weakness, numbness, or paralysis. Other large joints, such as the hips and knees, can also be affected, presenting with joint swelling, pain, and difficulty walking.
Systemic symptoms (generalized signs of infection) may be present but are often mild or absent in skeletal TB. These non-specific symptoms include a low-grade fever, unexplained weight loss, fatigue, and night sweats. The subtle nature of these symptoms often contributes to a significant delay in diagnosis, sometimes taking months or years.
Confirming the Diagnosis
Confirming skeletal tuberculosis requires a multi-step process because the clinical presentation is not specific enough to differentiate it from other bone or joint conditions. Imaging studies are essential for assessing bone and soft tissue damage. While X-rays may reveal late-stage destruction, computed tomography (CT) scans and magnetic resonance imaging (MRI) provide a much clearer and earlier picture of the infection.
MRI is the preferred imaging method as it shows early changes in the bone marrow and soft tissues, including abscess formation. However, a definitive diagnosis relies on laboratory confirmation by identifying M. tuberculosis in a tissue sample. This necessitates a tissue biopsy, where a sample is taken directly from the affected bone or joint, sometimes guided by CT or ultrasound.
The tissue sample is used for culture, the gold standard for microbiological diagnosis, and for molecular testing, such as polymerase chain reaction (PCR). Molecular tests detect the bacteria’s genetic material and provide a rapid diagnosis, useful for initiating timely treatment. Testing is necessary to distinguish skeletal TB from other conditions, like bacterial arthritis or bone tumors, which can have similar imaging findings.
Medical and Surgical Treatment
The primary treatment for skeletal tuberculosis is a prolonged course of anti-tubercular medication. The standard regimen involves a combination of multiple first-line drugs: isoniazid, rifampin, pyrazinamide, and ethambutol. This multi-drug approach is necessary to effectively kill the bacteria and prevent drug resistance.
The duration of this pharmacological treatment is significantly longer than for uncomplicated pulmonary TB, often lasting six to nine months, or sometimes 12 months or more. Patient compliance with the full course of medication is important to ensure a complete cure and avoid recurrence.
Surgical intervention is generally reserved for specific, complicated cases, as the medical regimen is effective for most patients.
Indications for Surgery
The main indications for surgery include:
- The presence of neurological deficits, such as spinal cord compression, requiring immediate decompression.
- Correction of severe spinal deformities, such as kyphosis.
- Draining large abscesses that are not responding to medication alone.