Spinal Tuberculosis (Pott's Disease)

Spinal tuberculosis (Pott's disease) is the most common form of skeletal tuberculosis, first described by Percivall Pott in 1779. It represents a significant cause of morbidity, particularly in endemic regions, and remains important in the Australian context due to immigration patterns.

Epidemiology:

• Spinal TB accounts for 50% of all skeletal TB cases
• Second most common form of extrapulmonary TB
• Thoracolumbar junction (T10-L2) is most commonly affected
• Approximately 10-15% have skip lesions (non-contiguous involvement)
• Male to female ratio approximately 1.5:1
• Can occur at any age but peaks in second and third decades

Global Burden:

Australian Context:

Australia has low TB incidence overall, but overseas-born individuals (particularly from high-burden countries) account for the majority of cases. Spinal TB may present in immigrants, refugees, or travelers, often as reactivation of latent infection years after initial exposure.

Route of Infection

Primary Infection:

• Haematogenous spread from pulmonary focus (most common)
• Arterial dissemination to vertebral bodies
• Paradiscal arteries supply adjacent vertebrae (paradiscal type)
• Batson's venous plexus may facilitate spread

Secondary Spread:

• Subligamentous extension under ALL
• Epidural spread causing cord compression
• Paravertebral spread forming cold abscess
• Psoas tracking along muscle sheath

Anatomical Patterns of Involvement

1. Paradiscal Type (50-75%):

• Most common pattern
• Involves adjacent vertebral bodies and intervening disc
• Arterial spread via paradiscal arteries
• Late disc destruction (unlike pyogenic)
• May extend to multiple levels

2. Central Type:

• Isolated vertebral body involvement
• Concertina collapse
• May produce ivory vertebra
• Spares disc initially

3. Anterior Subligamentous Type:

• Spreads under anterior longitudinal ligament
• Multi-level involvement with anterior scalloping
• Can produce skip lesions
• Extensive yet may spare vertebral integrity initially

4. Posterior Type (2-10%):

• Involves neural arch (pedicle, lamina, spinous process)
• More common in lower lumbar spine
• May cause early neurological deficit

Pathological Changes

Bone Changes:

• Granulomatous inflammation
• Caseous necrosis
• Bone destruction and sequestration
• Minimal new bone formation (unlike pyogenic)

Soft Tissue:

• Cold abscess formation (paravertebral, epidural, psoas)
• Granulation tissue proliferation
• Fibrosis with healing

Neurological Compression:

• Early: Epidural granulation tissue, abscess
• Late: Bony compression from kyphotic deformity

History

Presenting Symptoms:

Key History Elements:

• Duration of symptoms (typically weeks to months)
• Constitutional symptoms (weight loss, night sweats, low-grade fever)
• Neurological symptoms (weakness, numbness, bowel/bladder)
• Contact history (TB exposure)
• Country of origin and travel
• Immunocompromise (HIV, diabetes, immunosuppressants)
• Previous TB treatment

Physical Examination

Spinal Assessment:

• Gibbus deformity (angular kyphosis)
• Localized tenderness
• Paraspinal muscle spasm
• Restricted range of motion
• Cold abscess (paravertebral, groin, flank)

Neurological Examination:

• Motor power (myotomes)
• Sensory level
• Reflexes
• Long tract signs (spasticity, clonus, Babinski)
• Bladder/bowel function
• Gait assessment

Systemic Examination:

• Lymphadenopathy
• Pulmonary findings (primary TB)
• Peripheral cold abscess
• Signs of other organ involvement

Red Flags

• Rapidly progressive neurological deficit
• Complete paraplegia
• Bladder/bowel dysfunction
• Respiratory compromise (cervical lesions)
• Signs of MDR-TB or treatment failure

Disease-Related Complications

Neurological Complications

Pott's Paraplegia:

• Early onset (active disease): Better prognosis
• Late onset (healed disease): Worse prognosis
• Causes: Abscess, granulation tissue, bony compression

Prognosis Factors:

• Duration of deficit (shorter = better)
• Completeness (incomplete = better)
• Age (younger = better)
• Vertebral destruction extent

Treatment-Related Complications

Medical:

• Hepatotoxicity (2-10%)
• Drug reactions
• Drug interactions
• MDR development

Surgical:

• Infection
• Neurological injury
• Hardware failure
• Pseudarthrosis
• Recurrence

Long-Term Sequelae

• Residual kyphosis
• Chronic pain
• Residual neurological deficit
• Adjacent segment disease
• Growth disturbance (paediatric)

Neurological Recovery

Prognosis by Presentation:

Favourable Factors:

• Short duration of deficit
• Incomplete paraplegia
• Younger age
• Compression by soft tissue (not bone)
• Early treatment initiation

Treatment Outcomes

Medical Treatment Alone:

• Success rate: 85-90%
• Healing time: 6-12 months
• Residual kyphosis: 30-50%

Combined Medical + Surgical:

• Neurological improvement: 70-90%
• Fusion rate: 90-95%
• Deformity correction maintained

Long-Term Prognosis

Factors Affecting Outcome:

• Extent of initial disease
• Timing of treatment
• Adequacy of ATT
• Surgical technique
• Patient compliance

Return to Activity:

• Light activities: 3-6 months
• Full activities: 6-12 months
• Depends on neurological status

Global Epidemiology

Tuberculosis remains a leading infectious cause of death worldwide, with around 1.3 million deaths annually. Spinal TB is the most common musculoskeletal manifestation, affecting roughly 1 to 2% of all cases of TB, and skeletal involvement occurs in approximately 10% of those with active disease. Burden is concentrated in South and South-East Asia, Sub-Saharan Africa and the Western Pacific. In low-incidence high-income settings, the overwhelming majority of cases are in people born in high-burden countries, frequently presenting as reactivation of latent infection years after migration. HIV co-infection, which is endemic in parts of Sub-Saharan Africa, adds substantially to both the burden and complexity of management.

Major Guidance Side-by-Side

The most important guideline divergence to recognise is duration: WHO endorses a 6-month regimen for drug-susceptible disease (supported by the MRC ambulant-chemotherapy RCT), whereas neurological/CNS-focused guidance such as the British Infection Society recommends a longer 12-month course (2 months of four drugs then at least 10 months of isoniazid and rifampicin) for spinal and CNS disease. Many spinal units extend treatment to 9-12 months in extensive or slow-responding disease.

Diagnostic Standards

A tissue diagnosis (culture, histology and nucleic-acid amplification) is the worldwide gold standard before committing a patient to prolonged therapy, and is especially important in low-prevalence settings and to detect drug resistance. Xpert MTB/RIF on bone or abscess material gives rapid results and simultaneously reports rifampicin resistance, but its sensitivity on bone is only moderate when used alone, so it should be paired with histopathology and culture rather than replacing them.

Practice Variation by Resource Setting

In resource-limited high-burden regions, empirical antitubercular therapy on clinical and radiographic grounds is common where biopsy is impractical, and a conservative "middle-path" approach (chemotherapy with selective surgery) predominates. In low-incidence settings, mandatory public-health notification, contact tracing, directly observed therapy for adherence, and multidisciplinary input from infectious diseases, spinal surgery, radiology and rehabilitation are standard.