Neurosurgery notes/Spine/Special diseases of the spine/Ankylosing diseases/Ankylosing spondylitis

Ankylosing spondylitis

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Ankylosing diseases

General

  • An systemic chronic autoimmune spondyloarthropathy characterised by
  • HLA-B27 histocompatability complex positive (90%)
  • RF negative (seronegative)
  • primarily affect axial spine

Pathoanatomy

  • Exact mechanism is unknown,
  • HLA-B27 → cytotoxic T cell autoimmune reaction → enthesitis (inflammation of insertion of tendon, ligaments, or muscle into bone) → ossification of ligaments, disc, end plates, apophyseal structures (targeting SI joints, spinal apophyseal joints and symphysis pubis) → syndesmophytes bridging the ossified nucleus pulposis → fusing (ankylosing) of spine → hyperkyphotic bamboo spine → long lever arm leads to
    • High force onto osteoporotic bone (AS accelerates osteoporosis through inflammation ??) → breakage
    • Transfer of increased stress to places of spine that still have some mobility like Craniovertebral junction → Atlanto-occipital subluxation

Genetics

  • there is a genetic predisposition, but mode of inheritance is unknown
  • HLA-B27 is located on Chr 6, B locus

Epidemiology

  • 4:1 male:female
  • affects ~0.2% of Caucasian population
  • usually presents in 3rd decade of life
  • juvenile form <16-years-old includes enthesitis
  • fewer than 10% of HLA-B27 positive patients have symptoms of AS

Modified New York criteria for the diagnosis of AS

  • Definite AS: 1 radiologic criterion + at least one clinical criterion
  • Probable AS: radiological criterion without clinical criteria, or 3 clinical criteria without radiological criterion
    • Clinical criteria Inflammatory back pain:
      • Low back pain
        • of more than 3 months,
        • improved by exercise,
        • not relieved by rest
      • Limitation of lumbar spine motion in both sagittal and frontal planes
      • Limitation of chest expansion relative to normal values for age and sex
    • Radiological criterion
        • Sacroiliitis ≥2 bilaterally or
        • Grades 3–4 unilaterally
        • Radiological criteria based on MR
         
        Grade
        Radiographic findings
        0
        Normal
        1
        Suspicious changes
        2
        Minimal abnormality: Small localised areas with erosion or sclerosis, without alteration in the joint width
        3
        Unequivocal abnormality: Moderate or advanced sacroiliitis with one or more of the following: erosions, evidence of sclerosis, widening, narrowing, or partial ankylosis
        4
        Severe abnormality: total ankylosis
         

Manifestations

  • Systemic manifestations
    • Acute anterior uveitis & iritis
    • Heart disease (cardiac conduction abnormalities)
    • Pulmonary fibrosis
    • Renal amyloidosis
    • Ascending aortic conditions (aortitis, stenosis, regurgitation)
    • Klebsilella pneumoniae synovitis
      • HLA-B27 individuals are more susceptible
  • Orthopaedic manifestations
    • bilateral sacroiliitis
    • progressive spinal kyphotic deformity
    • cervical spine fractures
    • large-joint arthritis (hip and shoulder)
 

Presentation

  • Symptoms
    • lumbosacral pain and stiffness
      • present in most patients
      • worse in morning
      • insidious onset in 3rd decade of life
    • neck and upper thoracic pain
      • occurs later in life
      • acute neck pain should raise suspicion for fracture
    • sciatic
      • Piriformis spasm from inflammation → sciatic nerve compression
    • loss of horizontal gaze
    • shortness of breath
      • costovertebral joint fusion → reduced chest expansion
  • Physical exam
    • limitation of chest wall expansion
      • < 2cm of expansion is more specific than HLA-B27 for making diagnosis
    • Schober test:
        • Used to evaluate lumbar stiffness
        • Decreased spine motion in AS
        • It measures the movement of the lumbar spine eliminating the hip flexion: 10 cm proximal and 5 cm distal to the line between the posterior superior iliac spines in the midline are marked. The distance between them in flexion should be at least 5 cm more than in extension.
        notion image
    • Kyphotic spine deformity
    • Hip flexion contracture
      • Examining patient in supine and sitting position helps differentiate sagittal plane imbalance due to hip flexion contractures or kyphotic spinal deformity
    • Sacroiliac provocative tests
      • Faber test (flexion, abduction, external rotation of hip)
          • flexion abduction external rotation of the ipsilateral hip causes pain
            • If pain occurs anteriorly on the same side of the body → hip joint disorder
            • If pain occurs posteriorly on the opposite side of the body → SI joint disorder
          notion image

Tx

  • Nonoperative
    • NSAIDS, COX-2 inhibitors, and therapy
      • indications
        • first line of treatment for pain and stiffness
        • oral steroids not recommended
      • techniques
        • physical therapy should focus on maintaining flexibility
    • TNF-alpha-blocking agents
      • indications
        • second line of medical management
      • techniques
        • includes infliximab, etanercept, adalimumab
      • outcomes
        • clinical studies show significant improvement in severity of symptoms
  • Operative

Specific types of injury

craniovertebral junction injuries
  • Atlantooccipital subluxation
    • Worst complication of AS
    • Incidence 0.5-32%
    • Tx:
      • No neurology: Halovest/rigid orthosis
        • There is high risk of progression
      • Symptomatic pt
        • ventral decompression via a transoral transpalatopharyngeal approach.
Subaxial spine injuries
  • 1/3 cases lead to death
  • 1.3%/yr
  • Mainly at
    • lower cervical spine
    • cervical–thoracic junction
  • Commonly missed:
    • pt undergoing corticosteroid therapy
    • Fractures are typically difficult to visualize on conventional X-rays of the kyphotic cervical and thoracic spine. 36% missed
  • Rate of neurological deficit: 43%, 3x more risk than general pop
  • Fractures are through the disc in 50-70% cases
    • Conservative
      • Bed rest, traction, immobilization with halo vest
        • Immobilized in the initial kyphotic position to avoid hyperextension which can lead to neurological deterioration
      • Pros
      • Cons
        • Bed rest: Higher risk of pulmonary and decubitus complication
        • Axial traction: medullary traction
        • Worsening kyphosis with loss of reduction
        • Poor fracture healing: Risk of non-union due to the long arm of fracture having constant shearing forces on fracture site
          • Non-union can inc risk of neurological aggravation
    • Surgical
      • Long segment posterior fixation
      • Posterior or combined approach do not do anterior only
      • Pros
      • Cons
Thoracolumbar spine fractures
  • 50% develop post injury neurological deficit
  • Conservative
    • Poor fracture healing
    • Mortality rate was lower for surgical patients (23% vs. 51%).