Tuberculosis of Bones and Joints

Introduction & Pathogenesis - Bone's Silent Siege

• Etiology: Mycobacterium tuberculosis.
• Spread: Hematogenous from primary focus (lungs > lymph nodes).
• Pathogenesis:
  • Bacilli lodge in vascular bone: vertebral bodies, metaphysis/epiphysis, synovium.
  • Immune response → granuloma (epithelioid cells, Langhans cells, lymphocytes, caseous necrosis).
  • Enzymatic destruction: cartilage (pannus), bone (lytic lesions).
  • Results in: juxta-articular osteoporosis, cold abscess, sinus tracts.
• Common sites: Spine (Pott's disease) > Hip > Knee.

⭐ Spine (Pott's disease) is the most common site of skeletal TB.

Clinical Manifestations - TB's Crippling Clues

• General (Constitutional):
  • Low-grade fever (evening rise)
  • Weight loss, anorexia
  • Night sweats, malaise
• Local (Affected Site):
  • Pain: insidious, often worse at night (night cries in children), ↑ with activity
  • Swelling: initially doughy, may progress to cold abscess

    ⭐ Cold abscess (lacks acute inflammation signs) is a characteristic feature of musculoskeletal TB.

  • Deformity: e.g., kyphosis (Pott's spine), joint contractures
  • Stiffness & ↓ range of motion (ROM)
  • Muscle wasting (atrophy)
  • Sinus tract formation (chronic cases)
• Site-Specific Highlights:
  • Pott's Spine: Back pain, tenderness, spinal deformity (gibbus), neurological deficit (Pott's paraplegia)
  • TB Hip/Knee: Limp, pain, swelling, restricted movement. oka

Diagnostic Workup - Finding TB's Footprint

• Baseline Bloods: ↑ ESR/CRP; Anemia; Lymphocytosis.
• Immunological Tests:
  • Mantoux (TST): >10mm significant (HIV+ >5mm).
  • IGRA (e.g., QuantiFERON-TB Gold): More specific. Both indicate exposure, not active disease.
• Imaging:
  • X-ray:
    • Early: Osteopenia, soft tissue swelling.
    • Phemister's Triad (📌 PEM - Periarticular osteoporosis, Erosions peripherally/marginally, Slow joint space narrowing).
    • Late: Destruction, deformity.
  • MRI:
    • Most sensitive for early changes (synovitis, marrow edema, pre-pus).
    • Assesses soft tissue, abscesses, cord compression (spine).

    ⭐ MRI is the most sensitive imaging modality for early detection of osteoarticular TB and assessing soft tissue involvement, including pre-pus stages.

  • CT Scan: Details bony destruction, sequestra.
• Definitive Diagnosis (Gold Standard):
  • Synovial Fluid / Pus / Tissue Biopsy:
    • AFB Smear: Low sensitivity.
    • Culture (LJ medium): Takes 4-6 weeks.
    • NAAT (GeneXpert): Rapid, detects MTB & Rifampicin resistance.
    • Histopathology (Biopsy): Caseating granulomas.

Management Strategies - TB Treatment Triumph

• Goals: Eradicate infection, preserve function, prevent deformity.
• Cornerstone: Multi-drug Anti-Tubercular Therapy (ATT).
  • 📌 RIPE Regimen: Rifampicin, Isoniazid, Pyrazinamide, Ethambutol.
  • Duration: 9-12 months (paucibacillary); 12-18 months (multibacillary/spinal).
  • DOTS strategy recommended.
• Supportive Care: Rest, nutrition, analgesia, physiotherapy.

• Surgical Indications:
  • Biopsy for diagnosis.
  • Drainage of large abscesses.
  • Debridement of sequestra/infected tissue.
  • Stabilization (spine/joints).
  • Deformity correction.
  • Salvage procedures (arthrodesis/arthroplasty) for destroyed joints.

⭐ Multi-drug anti-tubercular therapy (ATT) for an extended duration (e.g., 9-18 months depending on site/severity) is the cornerstone of treatment for bone and joint TB.

High‑Yield Points - ⚡ Biggest Takeaways

• Spine (Pott's spine) is the most common site, typically thoracolumbar junction.
• Phemister's triad (juxta-articular osteoporosis, peripheral erosions, joint narrowing) is key radiologically.
• Cold abscess formation is a hallmark; may track along fascial planes.
• Diagnosis: imaging (X-ray, MRI), biopsy/aspirate for AFB, culture, histopathology (caseating granulomas).
• Treatment: Multi-drug anti-tubercular therapy (ATT) for 9-12 months is standard.
• Watch for paradoxical worsening on ATT and gibbus deformity in spinal TB.