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British Medical Books Health Issues Computerized Tomography

Tuberculous Spondylitis (Pott's disease)

Incidence

  • tuberculosis is a disease of the third world
    • which amounts to about 80% of the population of the world
  • annual risk of infection 1,5 - 2,5% in the sub-Saharan Africa
  • primarily pulmonary infection
  • EPTB presents with increasing frequency
    • incidence of urogenital tuberculosis is 28%
    • miliary tuberculosis 27% and
    • spinal tuberculosis 10% to 25%
      • most common at thoracic -Th-L, than lumbar and rare at the cervical spine
      • C-spine TB is 3,5% of all spinal TB
  • new tendency - increasing HIV infection
    • →co-infection w/ TB from endogenous reactivation of the dormant TB infection
  • predisposing factors
    • socio-economic factors - nutrition, housing etc.
    • DM
    • alcoholism

Aetiology

  • caused by Mycobacterium tuberculosis
  • two types of tuberculosis are found in the spine
    • human type → originates from a primary focus in the lung & then spreads
      haematogeneously to the vertebrae
    • bovine type → ingested w/ milk into the intestinal canal & absorbed into the mesenteric
      glands & from there it spreads haematogeneously to the spinal column
  • ? lymphatic spread as well

Pathology

  • in the vertebral column the TB organism destroys the bone at the sub-chondral level
  • eventually the vertebrae collapse & form a gibbus
  • why in vertebral body ?
    • rich venous plexus (Batson)
    • sluggish circulation
    • daily trauma
  • tubercle forms & spreads along planes
    • Th-L spine - psoas abscess, ant. & post. longit. Lig
    • C-spine - axilla, along brachial plexus

Neurology

  • gradual onset & progression, mostly if > 10 yrs old
  • Frankel grading
  • seen in 40 % of patients & is d/t
    • inflammatory myelitis
    • P° from an abscess or from deformity
    • vascular causes -acute onset

Clinical

  • Symptoms
    • often present late - pain not a major symptom
    • deformity (gibbus ) - commonest presenting feature
    • most serious symptoms are paresis or paralysis
    • less common presentation includes abscesses or sinuses
    • other symptoms as coughing, fever, night sweat, weight loss etc. must be looked for
  • Full work up
  • all patients should be admitted - ideally
    • history - TB contact, previous treatment
    • examination
      • general
        • chest, lymph nodes, wasting
        • look for abscesses - axilla, hip
      • spine - most common deformity is a kyphosis
      • documentation of neurological status
    • FBC + ESR
      • Iymphocytosis & elevated ESR (may be > 100mm )
      • HIV test recommended
    • skin testing (PPD)
      • supportive for the dg. of TB
      • excludes other chronic bone infection w/ similar X-ray e.g. Salmonella typhi & fungi
    • febrile antigens (CRP)
    • 3X urine & sputum
      • for microscopy (AFB) & culture
      • 55 - 75% accurate
    • X rays - spine + chest
    • exclude other pathology in adults
      • ? myeloma (bence-jones proteins, protein electrophoresis)
      • tumour markers
      • Widal test (salmonella typhi) & serology for brucella
      • tomo's shows posterior elements well, may demonstrate cavitation
      • bone scan - identifies skip & other bony lesions
      • tissue biopsy - MC&S, TB, Fungi, Bactec, also for histology
        • 75% accuracy

X ray investigations

  • Plain X rays
  • AP, lateral spine & CXR
    • entire spine to exclude multifocal dx.
  • w/ active infection 2 vertebrae usually involved - occasionally 1 only
  • classic appearance
    • 2 vertebrae involved, loss of the adjacent end plate cortical definition (lytic lesion)
    • anterior (vertebral body) involvement mostly, posterior < 10%
    • osteoporosis
    • paraspinal abscess on the AP (especially well seen on CxR)
  • healing phase
    • calcification, sclerosis
  • angle of the gibbus measured from
    • upper end plate of the 1st uninvolved prox. vert. to lower end plate of the 1st uninvolved distal vertebra
    • prediction of the final angle of the gibbus after conservative Rx is important
      • may determine whether chemotherapy or surgery is Rx of choice
  • Tomography
    • to determine posterior element involvement
  • Bone scan
    • defines the extent of the disease, skip vertebral lesions & other bony involvement
    • 35% false negative
  • Myelography
    • useful as pre-op investigation if MRI is not available
    • may cause neurological deterioration
    • for small children - GA
  • CT scan
    • can assess posterior element damage + extent of body involvement & number of bodies involved
    • paraspinous soft tissue involvement, psoas abscess, epidural abscess
  • MRI
    • best definition of the extent of the anterior pathology, possible cord injury & soft tissue involvement

Differential dg.

  • Brucellosis
    • 2% of all brucellosis involves spine
    • risk factors - working w/ animals
      • vets
      • farmers
      • southern Free State
    • dg.: brucella AB levels
    • Rx: Streptran & Rifampicin for 3/12
  • Salmonella
    • uncommon < 1% - sickle cell predispose
    • tends to be multifocal - check proximal humerus, distal femur
    • X-ray - same as TB
    • Dg.: Widal titer - not always
    • Rx.: AB
  • Aspergillus
    • fungal infection
      • if << immune function
      • HIV
      • malignancy
      • transplant pts.
    • Rx: anti-fungal, most need surgery
  • Tumours
    • always consider

Treatment principles

  • controversial especially w/ regard to the role of surgery

Children

  • treatment is started on clinical & X ray findings
  • in general, children are treated non-operatively

Adults

  • bacteriological & histological confirmation of disease before Rx. (unless surgery is planned)
    → needle biopsy below T9, above T9 open biopsy
  • most adults with neurology need surgery + chemotherapy

Choice of treatment

  • ambulatory chemotherapy or
  • strict bed rest + chemotherapy or
  • surgery + chemotherapy

Conservative treatment

  • hospitalise
  • protect cord, column & skin - treat spine as unstable
  • restrict activity - bedrest
  • chemotherapy - 3 drugs for children:
    • rifampicin : 6 mg/kg max. 300 mg
    • isoniazide (INH): 15 mg/kg max. 600 mg
    • pyrazinamide (PZA): 20 mg/kg max. 2-3g
    • 4 for adults: + ethambuthol 15-25 mg/kg max. 1,2 g
    • in a single dose daily w/ Pyridoxine 25 mg (for peripheral neuritis)
    • continued for 9-12/12 or until ESR normal & X rays show no sign of active infection
    • 2nd line of drugs - for resistant AFB - PAS, ethionamide
  • nutrition
  • physiotherapy
  • disability grant - 1 year for non-paraplegics, permanent for those with neurologic deficit
  • brace, POP jacket
  • monitor - clinical, ESR, LFT, X ray monthly
  • discharge & follow-up

Surgical treatment

  • Definite indications
    • anterior + posterior vertebral involvement → translational instability
      • anterior decompression & graft + posterior stabilisation
    • significant neurology (Frankel A - C) or neurological deterioration while on conservative Rx
    • multiple level involvment &amp; progressive kyphotic deformity
    • doubtful dg. - must have tissue dg.
    • surgical experience & facilities basic requirements
  • Relative indications
    • severe predicted kyphosis ( > 60° )
      • factors that influence an increase in gibbus angle
        • site: thoracic > T-L lesions > lumbar spine
        • pre-treatment angle: the greater the initial angle, the less the chance to increase
        • No. of levels involved
      • prediction of kyphotic angle in degrees
  • Y = A + Bx (A= 5.5°, B= 30.5°, x = the amount of the initial loss of the vertebral body)
  • recent onset of paraparesis w/ minimal bone destruction
    • prediction of kyphotic angle in degrees


    • * loss of every whole vertebral body = 30 to 35° of gibbus
      * children - gibbus angle tends to decrease as they grow

  • recent onset of paraparesis w/ minimal bone destruction
    • strict bed rest + chemotherapy until full neurological recovery
    • if no neurological improvement after 4 to 6 weeks ---> surgery

Surgery

    • acute onset paraplegia - vascular
    • paraplegia > 6-9/12
    • total motor loss
    • incontince
    • vibration sense loss
  • Anterior approach
    • generally indicated because
      • most have vertebral body disease
      • compression of the cord is anterior
  • Procedure - anterior decompression, radical debridement + strut graft
    • all pathological bone & disc excised leaving healthy bleeding bone
    • fibula or rib strut
    • most common late complications are d/t anterior graft failure (slip, absorption & #)
  • Posterior arthrodesis
    • recommended
      • more than 2 vertebral bodies involved
      • ant + post vertebral involvement - translational instability
      • anterior strut graft failure - instability
      • in children always if anterior fusion done → to prevent progressive kyphotic deformity w/ growth
    • instrumentation commonly used
      • Harrington or Luque rods, or pedicle screw - hook systems
      • sublaminar Mersiline tape if < 5 years, sublaminar wires for older children & adults
  • Post-operative bracing
    • for 3 - 6 months
      • TLSO
      • POP jacket