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Introduction
  •  Epidemiology
    • incidence
      • increasing incidence of TB in United States due to increasing immunocompromised population
    • demographics
      • HIV positive population (often seen in patients with CD4+ count of 50 to 200)
    • location
      • 15% of patients with TB will have extrapulmonary involvement  
      • the spine, and specifically, the thoracic spine is the most common extrapulmonary site
      • 5% of all TB patients have spine involvement
  • Pathoanatomy
    • early infection
      • begins in the metaphysis of the vertebral body
      • spreads under the anterior longitudinal ligament and leads to
        • contiguous multilevel involvement
        • skip lesion or noncontiguous segments (15%)
        • paraspinal abscess formation (50%)
          • usually anterior and can be quite large (much more common in TB than pyogenic infections) 
      • initially does not involve the disc space (distinguishes from pyogenic osteomyelitis, but can be misdiagnosed as a neoplastic lesion)
    • chronic infection
      • severe kyphosis
        • mean deformity in nonoperative cases is 15°
          • in 5% of patients, deformity is >60°
        • infection is often diagnosed late, there is often much more severe kyphosis in granulomatous spinal infections compared to pyogenic infections
        • in adults
          • kyphosis stays static after healing of disease
        • in children
          • kyphosis progresses in 40% of cases because of growth spurt
        • classification of progression (Rajasekaran)
          • Type-I, increase in deformity until cessation of growth
            • should be treated with surgery
          • Type-II, decreasing progression with growth 
          • Type-III, minimal change during either active / healed phases. 
Presentation
  • Symptoms
    • onset of symptoms of tuberculous spondylitis is typically more insidious than pyogenic infection
      • constitutional symptoms
        • chronic illness
        • malaise
        • night sweats
        • weight loss
      • back pain
        • often a late symptom that only occurs after significant boney destruction and deformity. 
  • Physical exam
    • kyphotic deformity
    • neurologic deficits (present in 10-47% of patients with Pott's Disease)
      • mechanisms
        • mechanical pressure on cord by abscess, granulation tissue, tubercular debris, caseous tissue
        • mechanical instability from subluxation/dislocation
          • paraplegia from healed disease can occur with severe deformity
        • stenosis from ossification of ligamentum flavum adjacent to severe kyphosis
Imaging
  • CXR
    • 66% will have an abnormal CXR
    • should be ordered for any patients in which TB is a possibility
  • Spine radiographs
    • early infection
      • shows involvement of anterior vertebral body with sparing of the disc space (this finding can differentiate from pyogenic infection)
    • late infection
      • shows disk space destruction, lucency and compression of adjacent vertebral bodies, and development of severe kyphosis
    • risk factors for buckling collapse ("spine at risk signs")  
      • retropulsion
      • subluxation
      • lateral translation
      • toppling
  • MRI with gadolinium contrast
    • indications
      • remains preferred imaging study for diagnosis and treatment
      • diagnose adjacent levels
        • multiple levels involved in 16-70%
    • findings
      • low signal on T1-weighted images, bright signal on T2-weighted images
      • presence of a septate pre-/ paravertebral / intra-osseous smooth walled abscess with a subligamentous extension and breaching of the epidural space  
      • end-plate disruption 
        • sensitivity 100%, specificity 81%
      • paravertebral soft tissue shadow
        • sensitivity 97%, specificity 85%
      • high signal intensity of the disc on the T2-weighted image
        • sensitivity 81%, specificity 82%
      • spinal cord
        • edema
        • myelomalacia
        • atrophy
        • syringomyelia
  • CT 
    • indications
      • demonstrates lesions <1.5cm better than radiographs
        • inaccurate for defining epidural extension
    • findings
      • types of destruction
        • fragmentary
        • osteolytic
        • subperiosteal
        • sclerotic
  • Nuclear medicine studies
    • obtain with combination of technetium and gallium
    • shown to have highest sensitivity for detecting infection
Studies
  • CBC
    • relative lymphocytosis
    • low hemoglobin
  • ESR
    • usually elevated but may be normal in up to 25%
  • PPD (purified protein derivative of tuberculin)
    • positive in ~ 80%
  • Diagnosis
    • CT guided biopsy with cultures and staining effective at obtaining diagnosis
      • should be tested for acid-fast bacilli (AFB)
        • mycobacteria (acid-fast bacilli) may take 10 weeks to grow in culture
      • PCR allows for faster identification (95% sensitivity and 93% accuracy)
      • smear positive in 52%
      • culture positive in 83%
Differential
  • Other etiologies of granulomatous infection may have similar clinical picture as TB and include
    • atypical bacteria
      • Actinomyces israelii
      • Nocardia asteroids
      • Brucella
    • fungi
      • Coccidioides immitis
      • Blastomyces dermatitidis
      • Cryptococcus neoformans
      • Aspergillosis
    • spirochetes
      • Treponema pallidum
Treatment
  • Nonoperative
    • pharmacologic treatment +/- spinal orthosis
      • indications
        • no neurological deficit
        • drugs are the mainstay of treatment in most cases
      • pharmacologic
        • agents
          • isoniazid (H), rifampin (R), ethambutol (E) and pyrazanamide (Z) therapy
        • regimen
          • RHZE for 2 months, then RH for 9 to 18 months
      • spinal orthosis
        • indications
          • may be used for pain control and prevention of deformity
  • Operative
    • anterior decompression/corpectomy, strut grafting ± posterior instrumented stabilization ± posterior column shortening  
      • indications
        • neurologic deficit
          • worsening neurological deficit
          • acute severe paraplegia
          • with panvertebral involvement with/without subluxation/dislocation
        • spinal instability 
        • kyphosis correction
          • > 60° in adult 
          • progressive kyphosis in child 
          • ≥3 vertebrae involved with loss of ≥1.5 vertebral bodies in thoracic spine
          • children ≤ 7 years with ≥3 vertebral bodies affected in T/TL spine and ≥ 2 at risk signs are likely to have progression and should undergo correction
          • late onset paraplegia (from kyphosis)
            • cosmetic correction of kyphosis controversial
        • advanced disease with caseation preventing access by antibiotics
        • failure of nonoperative treatment after 3 to 6 months
        • diagnosis uncertain
        • panvertebral lesion
      • advantages of surgical treatment
        • less progressive kyphosis
        • earlier healing
        • decreased sinus formation
        • in patients with neurologic deficits, early debridement and decompression led to improved neurologic recovery
      • technical aspects
        • autogenous and allograft strut grafts are acceptable with good results
        • continue medical management with isoniazid, rifampin, and pyrazanamide
        • chronic implant colonization is less common in TB and other granulomatous infections compared to more common pyogenic infections
    • Halo traction, anterior decompression, bone grafting, anterior plating 
      • indications
        • cervical kyphosis 
    • Pedicle subtraction osteotomy
      • indications
        • lumbar kyphosis
    • Direct decompression / internal kyphectomy 
      • indications
        • correction of healed thoracic/thoracolumbar kyphosis
        • allows spinal cord to transpose anteriorly
Surgical Technique
  • Anterior decompression/corpectomy, strut grafting ± posterior instrumented stabilization ± posterior column shortening
    • indications (see above)
      • kyphosis
      • active disease
    • techniques
      • single-stage transpedicular
      • 2-stage 
        • anterior decompression with bone grafting
        • posterior kyphosis correction and instrumentation
      • single-stage extrapleural anterolateral
Complications
  • Deformity (kyphosis/gibbus)
    • highest risk
      • after anterior decompression and grafting alone
        • slippage and breakage of graft (especially if ≥ 2 levels)
    • lowest risk
      • after both anterior and posterior fusion
  • Retropharyngeal abscess affects swallowing/hoarseness
  • TB arteritis and pseudoaneurysm
  • Respiratory compromise if there is costopelvic impingement
  • Sinus formation
  • Pott's paraplegia
    • spinal cord injury can be caused by abscess/bony sequestra or meningomyelitis
    • abscess/bony sequestra has a better prognosis than meningomyelitis as the cause of spinal cord injury
Atypical Spinal Tuberculosis
  • definition
    • compressive myelopathy without visible spinal deformity, without typical radiological appearance
  • etiology
    • intraspinal granuloma, neural arch involvement, concertina collapse of vertebra body      , sclerotic vertebra with bridging of vertebral body
  • treatment
    • laminectomy 
      • indications
        • extradural extraosseous granuloma
        • subdural granuloma
    • decompression and myelotomy
      • indications
        • intramedullary granuloma
 

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