Summary

Ankylosing Spondylitis (AS) is a chronic inflammatory seronegative spondyloarthropathy that primarily affects the axial skeleton (sacroiliac joints and spine). It is characterized by Inflammatory Back Pain (morning stiffness, improving with exercise) and progressive ossification of the spinal ligaments, leading to the classic "Bamboo Spine" fusion. It is strongly associated with the HLA-B27 gene (>90% positive). Management has been revolutionised by Biologics (Anti-TNF and IL-17 Inhibitors), which can halt radiographic progression if started early. A critical pitfall is missing a spinal fracture in an AS patient; the fused spine is brittle ("Chalk Stick") and breaks easily with minor trauma. [1,2]

Key Facts

• Definition: Chronic inflammation of the entheses (ligament insertions) causing fusion.
• Demographics: Young Males (onset <45 years). M:F 3:1.
• Genetics: HLA-B27 positive in >90% of white patients.
• Key Symptom: Inflammatory Back Pain (Stiffness >30 mins, Wakes at night, Better with movement, Worse with rest).
• Extra-Articular: Acute Anterior Uveitis (40%), Aortic Regurgitation, Apical Pulmonary Fibrosis.
• Imaging: Sacroiliitis is the prerequisite for diagnosis.

Clinical Pearls

"The Carrot Stick Spine": A fused spine is effectively a long bone (like a femur). It loses all flexibility. Even a minor fall can cause a catastrophic fracture (usually usually Cervical). These are unstable and often have neurological deficits. Have a pitifully low threshold for CT/MRI in any AS patient with new pain. X-rays often miss the fracture in the osteoporotic/fused bone.

"It's not just back pain": Ask about the eye (Redness/Pain? - Uveitis), the gut (Bloody stool? - IBD), and the skin (Psoriasis?). The Spondyloarthropathies are a family.

"NSAIDs are different here": In mechanical back pain, NSAIDs are just painkillers. In AS, NSAIDs are undoubtedly Disease Modifying. Continuous NSAID use retards radiographic progression.

"The Wall Test": Ask the patient to stand with heels, buttocks, and shoulders touching the wall. Can they touch the back of their head to the wall? If not (Tragus-to-Wall distance >0), they have significant cervical kyphosis.

        INFLAMMATORY BACK PAIN
                ↓
    CONFIRM DIAGNOSIS (MRI/B27)
                ↓
    ┌─────────────────────────┐
    │     FIRST LINE          │
    │ - Education / Smoking   │
    │ - Physiotherapy (Swim)  │
    │ - NSAIDs (Continuous)   │
    └─────────────────────────┘
                ↓
        PERSISTENT ACTIVITY?
        (BASDAI Score > 4)
                ↓
    ┌─────────────────────────┐
    │     BIOLOGICS           │
    │ - Anti-TNF (Adalimumab) │
    │ - IL-17 (Secukinumab)   │
    └─────────────────────────┘
                ↓
        DEFORMITY / # ?
                ↓
             SURGERY
        (Osteotomy / Fixation)

1. Conservative

• Exercise: Crucial. Swimming (extension) is best. Keep the spine mobile.
• Smoking Cessation: Smoking accelerates fusion and lung fibrosis.
• NSAIDs: Indomethacin/Naproxen. 70% of patients respond well. continuous use reduces fusion rate.

2. Biologics (The Game Changers)

• Anti-TNF agents (Infliximab, Etanercept, Adalimumab):
  • Rapidly reduce pain and CRP.
  • Halt radiographic progression if started early.
• IL-17 Inhibitors (Secukinumab):
  • For TNF-failures.

3. Surgical

• Vertebral Osteotomy: Wedge resection of bone (usually L2/L3) to correct severe fixed kyphosis (chin-on-chest deformity), allowing patient to look forward. High risk (aortic rupture/paralysis).
• Total Hip Replacement: Common due to hip involvement.
• Fracture Fixation: Long-segment screw fixation required for spinal fractures (due to long lever arm).

BASDAI (Bath Ankylosing Spondylitis Disease Activity Index)

• A subjective score (1-10) of:
  1. Fatigue.
  2. Spinal Pain.
  3. Joint Pain.
  4. Enthesitis.
  5. Morning Stiffness severity.
  6. Morning Stiffness duration.
• Score > 4: Indicates active disease eligible for Biologics.

Key Studies

1. Wanders et al. (2005): Continuous vs On-demand NSAIDs. Continuous group had less radiographic progression.
2. Braun et al. (2002): Infliximab efficacy. Landmark trial.
3. ASAS Classification: Defined "Axial Spondyloarthritis" to include "Non-radiographic" disease (MRI positive but X-ray normal), allowing earlier treatment.

What is AS?

It is a condition where your immune system attacks the ligaments of your spine. Over time, this inflammation turns to bone, potentially fusing the vertebrae together like a bamboo cane.

Will I end up hunched over?

Not necessarily. In the old days, yes. But with modern "Biologic" drugs, we can switch off the inflammation completely in many people preventing the fusion.

What can I do?

Keep moving! Exercise is medicine. Swimming is best because it forces you to arch your back and keeps your chest open. Do not smoke - it makes the fusing happen faster.

Why do I need eye checks?

The same inflammation can attack the eye (Iritis). If you ever get a painful red eye, see an eye doctor immediately (that day). Steroid drops cure it quickly, but delay can cause blindness.