Define Tuberculosis of Bones & Joints. Describe its investigations, management and complications.

Definition & General Features

Tuberculosis of bones and joints (osteoarticular TB) is a chronic granulomatous infection by Mycobacterium tuberculosis, usually secondary to a pulmonary or lymph-node focus and spread haematogenously. After the spine, the hip and knee are the commonest sites. It is a disease of insidious onset with constitutional symptoms (evening pyrexia, night sweats, weight loss) and a monoarticular, destructive but ‘cold’ course.

Pathology & Stages

Infection starts in the synovium or in the juxta-articular bone, producing a caseating granulomatous pannus that erodes cartilage from the margins. Because there is little reactive new bone, TB causes osteoporosis and destruction rather than sclerosis. Clinically it evolves through stages: synovitis → early arthritis (cartilage loss) → advanced arthritis with marked destruction, deformity and, ultimately, fibrous ankylosis.

Clinical Features (hip & Knee)

There is pain (often referred to the knee in hip disease), a limp, muscle wasting and progressive restriction of movement, with night cries in children (painful spasm on relaxation during sleep). The hip passes through a sequence of apparent deformities — early flexion, abduction and external rotation (stage of synovitis), later flexion, adduction and internal rotation (stage of destruction). A cold abscess or discharging sinus may develop.

Investigations

Raised ESR; positive Mantoux/IGRA; radiographs show juxta-articular osteoporosis, marginal erosions and reduced joint space (Phemister’s triad). MRI shows synovitis, effusion, abscesses and early bone involvement. Synovial biopsy/aspiration for histology (caseating granuloma), AFB, culture and GeneXpert confirms the diagnosis and drug sensitivity.

Management

The basis of treatment is anti-tuberculous chemotherapy (multi-drug regimen for a prolonged course), with rest and splintage of the joint in a functional position to relieve pain and prevent deformity, followed by guarded mobilisation. Surgery (synovectomy, joint debridement, abscess drainage, and later arthrodesis or arthroplasty for a destroyed joint) is reserved for advanced disease, deformity or failure of drug treatment. Good nutrition and general care aid recovery.

Complications

Untreated or advanced osteoarticular TB leads to progressive joint destruction with deformity and shortening, fibrous ankylosis in a non-functional position, cold abscesses and chronic discharging sinuses (with risk of secondary pyogenic infection), and, in the spine, paraplegia. Early diagnosis and full chemotherapy prevent most of these, which is why constitutional symptoms with a chronic monoarthritis should prompt investigation for TB rather than prolonged empirical treatment.

Principles of Anti-tuberculous Therapy

Skeletal TB is treated with the same multi-drug regimen as other forms of tuberculosis, for a prolonged course. An intensive phase of four drugs (isoniazid, rifampicin, pyrazinamide and ethambutol) is followed by a continuation phase of isoniazid and rifampicin, the total duration commonly extended for bone and joint disease. Adherence is critical to prevent drug resistance; directly observed therapy and drug-sensitivity testing (including GeneXpert for rifampicin resistance) are important. Adequate nutrition and treatment of coexisting conditions (HIV, diabetes) improve outcome.

Spine is the commonest skeletal site.

• Osteoarticular TB: after spine, hip and knee commonest; monoarticular, insidious, ‘cold’.
• Causes osteoporosis and destruction, not sclerosis; Phemister’s triad on X-ray.
• Stages: synovitis → early → advanced arthritis → fibrous ankylosis.
• Confirm by biopsy/culture; MRI for extent. TB arthritis is cold, pyogenic is hot.
• Treat with ATT + rest/splintage; reconstructive surgery only once disease is quiescent.