Summary

Ankylosing Spondylitis (AS) is a chronic seronegative inflammatory spondyloarthropathy characterized by inflammation of the axial skeleton (sacroiliitis and spondylitis) and entheses. It typically affects young men (20-30s) and is strongly associated with HLA-B27 (90%). The disease hallmark is Inflammatory Back Pain (Morning stiffness >30m, Improves with exercise) leading to progressive ossification and fusion of the spine (Bamboo Spine). The most critical orthopaedic risk is the Chalk Stick Fracture: the fused spine breaks like a long bone, often with fatal neurological consequences. Management has been revolutionized by Anti-TNF biologics. [1,2,3]

Key Facts

• The "Question Mark" Posture: Loss of lumbar lordosis + Increased thoracic kyphosis = Stooped forward look.
• The 3 A's: Extra-articular features: Anterior Uveitis, Aortic Regurgitation, Apical Lung Fibrosis.
• Inflammatory vs Mechanical:
  • Inflammatory: Morning stiffness, Better with movement, Young patient.
  • Mechanical: Worse with movement, Better with rest, Old patient.

Clinical Pearls

"The Chalk Stick Fracture": An AS patient who falls from standing height and has neck pain has a fracture until proven otherwise. The spine is rigid and osteoporotic. It snaps like a piece of chalk. These are HIGHLY unstable. CT whole spine is mandatory.

"Don't intubate blindly": Their cervical spine is often fused in flexion. Trying to extend the neck for intubation can snap the cord. Awake fibre-optic intubation is often needed.

"Wall Test": Ask them to stand with heels and back against a wall. They cannot touch their head to the wall (Occiput-to-Wall distance >0) due to kyphosis.

                 INFLAMMATORY BACK PAIN
               (Morning Stiffness, Age <45)
                        ↓
             DIAGNOSIS (MRI / HLA-B27 / X-RAY)
                        ↓
             EDUCATION + SMOKING CESSATION
             + PHYSIOTHERAPY (Maintain ROM)
                        ↓
                   NSAIDs (First Line)
             (Full dose, e.g., Naproxen 500 BD)
                        ↓
               RESPONSE AFTER 4 WEEKS?
               ┌──────────┴──────────┐
              YES                   NO
               ↓                     ↓
          CONTINUE               TRY 2ND NSAID
                                     ↓
                                   FAILED?
                                     ↓
                             ASSESS BASDAI SCORE
                             (Activity Index >4?)
                                     ↓
                                 BIOLOGICS
                              (Anti-TNF: Infliximab)
                              (IL-17: Secukinumab)

1. Physio & Lifestyle

• Exercise: Crucial. "Motion is Lotion". Swimming (Extension) is excellent.
• Posture: Sleep flat, avoid high pillows (prevent neck flexion contracture).
• Smoking: Cessation is mandatory (Smoking accelerates fusion).

2. Medical

• NSAIDs: First line. Can retard radiographic progression if taken continuously.
• Biologics (Anti-TNF):
  • Examples: Infliximab, Etanercept, Adalimumab.
  • Criteria (NICE): Diagnosis confirmed + High Activity (BASDAI >4) + Failure of 2 NSAIDs.
  • Effect: Dramatic reduction in pain and CRP. May not stop fusion if already advanced.

3. Surgical

• Fracture Fixation: Long-segment fixation (2 levels above, 2 below) for Chalk Stick fractures.
• Pedicle Subtraction Osteotomy (PSO): To correct severe fixed kyphosis (allowing patient to "look horizontal" again).
• Hip Arthroplasty: Often needed for fused hips.

ASAS Classification Criteria

• The gold standard for diagnosis.
• Imaging Arm: Sacroiliitis on imaging + 1 x SpA feature.
• Clinical Arm: HLA-B27 positive + 2 x SpA features.

NICE TA383 (Anti-TNF)

• Recommends Adalimumab/Etanercept for severe active AS.
• Must show reduction in BASDAI by 50% to continue treatment at 12 weeks.

What is AS?

It is a type of inflammation that targets your spine. It makes the backbone stiff. In some people, the body tries to heal this inflammation by laying down new bone, which can fuse the vertebrae together like a bamboo cane.

Is it genetic?

There is a strong genetic link (HLA-B27 gene). If you have the gene, you are at higher risk, but it doesn't mean your children will definitely get it.

The Treatments

We have very powerful medicines now (Biologics) that act like "highly targeted missiles" to switch off the inflammation. They can prevent the stiffness and change the course of the disease.

Exercise

Exercise is your medicine. If you stop moving, you fuse. You must keep the spine flexible.

Q1: What is the "Chalk Stick Fracture"? A: A fracture of the ankylosed (fused) spine, usually following minor trauma. Because the spine has lost its flexibility and is osteoporotic, it snaps transversely like a piece of chalk. These are highly unstable fractures (often C-spine or CT junction) carrying a high risk of spinal cord injury.

Q2: Describe Schober's Test. A: A test for lumbar flexion. Mark the PSIS (Dimples of Venus) level (L5). Mark a point 10cm above it. Ask patient to touch their toes. In a normal spine, the distance increases to >15cm (stretches by >5cm). In AS, the distraction is <5cm due to loss of lumbar flexion.

Q3: Name 3 Extra-articular manifestations of AS. A: Anterior Uveitis (Acute Iritis - most common), Aortic Regurgitation (due to aortitis), Apical Pulmonary Fibrosis. (Also IgA Nephropathy, IBD).

(End of Topic)