Ankylosing Spondylitis

Definition
Ankylosing Spondylitis is a chronic, inflammatory disorder of the axial skeleton resulting in the formation of new bone at the attachments of ligaments & tendons (enthesopathy).
Commonly affects sacroiliac joints as well as entire spine. Less commonly can affect shoulders, hips, peripheral joints and extra-articular surfaces.
Synonyms
Marie-Strumpell’s Disease
Rheumatoid Spondylitis
Secondary Ankylosing Spondylitis
Can occur in conjunction with the following
  1. Psoriasis
  2. Crohn’s Disease
  3. Ulcerative Colitis
  4. Reiter’s Syndrome (Reactive Arthritis)
Also consider Diffuse Idiopathic Skeletal Hyperexostosis (DISH) in your differential diagnosis’s.

Aetiology

Demographics

Gender
More common in males than females [3:1].
Age
Onset usually between 15-30 years of age.
Prevalence
Around 0.2% of the general population.

Pathophysiology

Poorly Understood Aetiology
Ankylosing Spondylitis has a strong genetic predisposition. Approximately 90% of AS patients express the HLA-B27 genotype. However, Only 5% of individuals with the HLA-B27 genotype go on to develop the disease.
Inflammation begins in ligamentous insertions (ensthesopathy). This then results in bony ankylosis, except in mild cases

History, Signs & Symptoms

History & Symptoms

History of Stiffness
  1. Progressive morning stiffness or pain of insidious onset for over 3 months
    • Pain and stiffness improves throughout the day
    • Symptoms are relieved with mild to moderate activity or hot shower
    • Stiffness is worse after periods of inactivity
  2. Night pain may be present in buttocks or thighs or lumbar spine
  3. Gradual ascending pattern of stiffness from the lumbosacral spine to thoracic & finally cervical spine

Physical Exam

Observation & Palpation
  1. Limited active range of movement(especially lumbar – potential loss of lumbar lordosis)
    • Lumbar Spine: decreased flexion, rotation, extension may not be possible
    • Cervical Spine: decreased in most range of movement, “stiff’ passive ROM
  2. Tenderness over the sacroiliac joint
General Exam
  1. Measure chest expansion with inspiration (may be limited)
  2. General stiffness or increased resistance wit passive spinal motion
  3. (+) Schober’s Test (decreased lumbar flexion ROM when measured with tape measure)
Imaging
  1. Ankylosing spondylitis is typically diagnosis with radiographic findings
  2. Sacroiliac joints
    • Moderate to advanced sacroiliitis (most consistent early sign)
    • Possibly ankylosis
    • May be unilateral at first but becomes bilateral
    • Pseudo-widening & erosions
  3. Spine
    • Marginal syndesmophytes
    • Vertebral squaring & demineralisation
    • Late finding “Bamboo spine”
    • “Trolley track” sign in lumbar spine
Laboratory Findings
  1. (+) HLA-B27 (90-95% of the time)
  2. Increased ESR & C-reactive protein
  3. Rh factor & ANA are within normal limits
  4. Elevated serum Ig levels
  5. Elevated alkaline phosphatase when active bone remodelling is occurring

Management

  1. Osseous manipulation & mobilisation – aim to promote movements in joints
  2. Exercise: aim to minimise deformity. Include spinal extension & general ROM, gym ball exercises, deep breathing exercises as well as postural training.
  3. Massage therapy
  4. Avoid: smoking, slouching or stooping, firm mattress & thin pillows
  5. Pharmacological
    • NSAIDs, oral methotrexate therapy if unresponsive
    • Corticosteroids have limited therapeutic value

Prognosis

  1. No cure available at present for ankylosing spondylitis.
  2. Commonly, the earlier the onset the more serious the outcome.
  3. Proper treatment can lead to minimal or no disability.
  4. Debilitating ankylosis is very rare.
  5. Prognosis is bleak if refractory iritis or secondary amyloidosis is present.