Pott's Disease (Tuberculous Spondylitis / Spinal Tuberculosis)

Epidemiology

• Global TB incidence exceeds 10 million cases/year with 1.3 million deaths/year; 1.2 million cases occur in children annually
• Musculoskeletal TB accounts for ~10% of all TB cases; spinal involvement is present in half of these (i.e., ~5% of all TB)
• The spine is involved in 40% of mycobacterial osteomyelitis cases overall
• Males and females are almost equally affected; incidence increases with age
• Site distribution: Thoracolumbar junction > lumbar spine > cervical spine

Pathogenesis

1. Primary infection - usually pulmonary TB (occasionally gastrointestinal or lymph node)
2. Hematogenous spread to the vertebral body (metaphyseal equivalent - subchondral bone near the disc)
3. Alternatively, direct extension from tracheobronchial lymph nodes into adjacent vertebrae
4. An infectious endarteritis causes bone necrosis and collapse
5. Infection spreads beneath and along the anterior and posterior longitudinal ligaments, leading to subligamentous spread to adjacent vertebral bodies - this explains the "skip lesions" seen on imaging
6. In adults, the intervertebral disc is initially spared (avascular in adults; a key distinction from pyogenic infection); in children, the disc may be involved early
7. Abscesses form, expand with necrotic debris, may track along fascial planes, and can drain spontaneously forming sinus tracts (cold abscesses)

Pathology

• Histology: Caseating granulomas with acid-fast bacilli (Langhans giant cells, epithelioid macrophages, lymphocytes, central caseous necrosis)
• Progressive anterior vertebral body destruction leads to:
  • Gibbus deformity (sharply angulated kyphosis) - the hallmark deformity
  • Vertebral collapse and compression fractures
  • Paravertebral/cold abscess formation
  • Epidural extension - more likely to cause permanent neurologic damage than the bony deformity alone
• Disc destruction + vertebral collapse = permanent scoliosis/kyphosis

Robbins & Cotran: Mycobacterial osteomyelitis (Pott disease) - vertebral destruction with kyphosis

Clinical Features

Constitutional symptoms (early, predominant)

• Weakness, malaise, night sweats, fever, weight loss
• ESR is invariably elevated (though normal in >50% in some series)
• Anemia and hypoproteinemia

Local symptoms

• Back pain in 70% at presentation - often months to years after symptom onset
• Progressive pain is a late symptom associated with bone collapse
• Cold abscess / intermittent draining sinuses
  • Psoas abscess - tracks down from thoracolumbar disease under the psoas fascia to present as a swelling in the femoral triangle; reducible, gives impulse on coughing, painless, lateral to the femoral artery
  • Retropharyngeal abscess - from cervical involvement; can cause hoarseness (recurrent laryngeal nerve), dysphagia, respiratory stridor; rarely, sudden death from erosion into great vessels

Neurological deficits

• Pott's paraplegia - spinal cord compression caused by:
  1. The kyphotic deformity itself (mechanical)
  2. Epidural abscess (pus or caseous granulation tissue extruding from infected vertebra) - the more common cause
  3. Pial arteritis with cord infarction (rare)
• ~30% of patients in less-developed countries present with neurologic deficits; less common in developed countries
• Neurological signs may wax and wane
• Motor function and rectal tone are good prognostic predictors

Key Distinguishing Feature vs. Pyogenic Spondylodiscitis

Investigations

• CBC: anemia; raised ESR and CRP (though ESR may be normal in >50%)
• Tuberculin skin test: contraindicated in suspected reactivation (risk of intense skin reaction/slough)
• Interferon-gamma release assay (IGRA) preferred

• Plain X-ray (early): subtle decrease in disc space height, localized osteopenia
• CT: bone destruction, paraspinal abscess
• MRI with and without contrast (preferred): best for demonstrating epidural abscess, cord compression, extent of disease, and skip lesions - entire spine should be imaged

MRI of Pott's spine showing kyphotic deformity at the thoracolumbar junction (Campbell's Operative Orthopaedics 2026)

• Culture of biopsy specimen or PCR/rapid molecular testing (also detects drug resistance)
• Percutaneous CT-guided biopsy is usually adequate
• Open biopsy if needle biopsy is dangerous or nonproductive

Treatment

Medical Management (first-line for most cases)

• Multi-drug anti-tuberculous therapy (ATT):
  • HRZE regimen: Isoniazid (H) + Rifampicin (R) + Pyrazinamide (Z) + Ethambutol (E), +/- Streptomycin
  • Duration: 6 months in immunocompetent patients; 18-24 months in HIV/immunocompromised or drug-resistant cases
• With early diagnosis and medical treatment, 80% of cases achieve bony fusion
• Drug-resistant TB (MDR-TB) benefits more from surgical treatment
• Outcomes are generally good; neurologic deficits often improve

Surgical Treatment

1. Neurologic deficit (compressive myelopathy)
2. Severe kyphosis (>40-60° depending on level)
3. Pain from spinal instability
4. Failure of medical therapy
5. Large paraspinal or epidural abscess
6. More than four levels of vertebral involvement

• ATT for at least 2-4 weeks preoperatively to suppress infection
• Nutritional support
• Manage comorbidities (hypertension, diabetes)
• Full-spine MRI to identify all involved levels including skip lesions

• Anterior debridement + fusion (Hodgson-Stock operation, 1956) - gold standard historically; allows direct debridement of anterior disease
• Posterior stabilization with instrumented fusion
• Combined anterior-posterior approach for severe deformity
• Cervical approach: Drainage of retropharyngeal abscess via posterior triangle or anterior cervical approach; allows bony reconstruction
• External stabilization alone (+ long-term ATT) may give excellent results in some patients, particularly when surgery is refused

Complications

Summary Mnemonic - POTT'S

• P - Paraplegia (Pott's paraplegia - the feared complication)
• O - Osteomyelitis (tuberculous, anterior vertebral body)
• T - Thoracolumbar (most common site)
• T - Tuberculosis (hematogenous spread from pulmonary focus)
• S - Skip lesions + Subligamentous spread + Spared disc (early)

Recent evidence note: A 2026 systematic review (PMID 42140478) on chronic spinal infections confirms that TB remains the dominant etiology globally, with emerging concerns about drug-resistant strains influencing both diagnostic and treatment algorithms.