Ankylosing Spondylitis - finished

Question 1

Define AS

Answer 1

An uncommon Systemic inflammatory disorder characterised by:
• Pain
• Stiffness
• Fusion 
Of the spine & SIJ’s

Question 2

Epidemiology of AS

Answer 2

M:F = 3:1
HLA-B27 is present in 95% of patients
Strong familial tendency

Question 3

Pathology of AS

Answer 3

In AS the primary sites of inflammation are the entheses of the vertebral and pelvic region, and the synovium of vertebral facet joints, SIJ’s and costovertebral joints.
As as result we see 2 presentations:
- Synovitis of the facet joints, SIJ’s and costovertebral joints
- Enthesitis of the IVD’s, SIJ ligs, pubic symphysis and bony insertions of the ligs and tendons

AS pathology is a 4 stage process that involves both involvement of the entheses and the synovium as stated above.

STAGE 1: INFLAMMATION
Inflammation of the fibrocartilage in cartilagenous joints, followed by changes in the fibrous tissue of the joint capsule, cartilage that surrounds the IVD, entheses and periosteum.

We see:

• infiltration by inflammatory cells
• granulation tissue formation
• erosion of:
  
  • adjacent bone and fibrocartilage in enthesitis
  • subchondral bone and articular cartilage in synovitis

STAGE 2: FIBROSIS
Replacement of granulation tissue by fibrous scar tissue

STAGE 3: OSSIFICATION AND ANKYLOSIS
Reactive new bone formation in:
- articular bone (sclerosis)
- adjacent ligs
- other joint structures e.g. annulus fibrosis

Ossification of the fibrous tissue of the joint causes ankylosis of the joint.

STAGE 4: REMISSION

Question 4

Radiology of AS

Answer 4

Cardinal signs of AS on xray include:
- erosion and fuzziness of SIJ and periarticular sclerosis eventually leading to ankylosis

We see changes in the SIJ:

• symmetrical, bilateral, subchondral sclerosis
• starts on the iliac side of the joint then later on both sides
• ghost sign: joint is mostly osteopoenic with sclerosis of sacroiliac ligaments and subchondral bone
• star sign: ossification of the iliolumbar ligaments

We also see changes in the vertebral joints:

• Involvement of the lumbar spine after the SIJ
• Barrel vertebrae - squaring off of the vertebrae
• Ossification of the longitudinal ligaments and annulus fibrosis, creating marginal syndesmophytes and eventually creating the image of a bamboo spine.
• Trolley tracks - due to ankylosis of the facet joints
• Dagger sign - ossification of the supraspinous ligaments

Question 5

Clinical Features of AS

Answer 5

Pain
• Insidious onset
• Occurs at pelvic & spinal entheses
• Recurrent
• Worse in the morning
• Worse after inactivity
• Gradually becomes more continuous

Peripheral arthritis rare
Limited spinal ROM (dec Lx ext and rot)
Spinal deformity
Extra articular manifestations

Question 6

AS extra articular manifestations

Answer 6

6 A’s

Atlanto-axial subluxation 
Anterior uveitis 
Apical lung fibrosis 
Aortic incompetence 
Amyloidosis (kidneys) 
Autoimmune bowel disease (UC)