Ankylosing Spondylitis -

Seronegative Spondyloarthropathies

Definition

Chronic Seronegative Spondyloarthropathy
Affects predominantly the sacroiliac joints & the spine
- Presents similar to pauciarticular JRA
- Usually male > 8 years of age
- Joints assymetric;
  - Low back pain
  - hips, knees, ankles, toes, rarely U/E
- AM stiffness
- ESR ↑
- ANA neg
- RF neg
- HLA B27+ in 90%
  - in the normal caucasion population it is 8% prevelent
- Enthesopathy is frequent

Diagnostic Criteria

Positive XR Sacroiliitis
One or more
- History of Lumbar Spine pain
- Stiff Lumbar Spine
- Chest expansion < 1″ at 4th intercostal space

Epidemiology

0.1% in Western Europe
Regional variation +++
- M:F – 3:1 (2:1 up to 10:1)
- Average onset 25 years
Family history ↑ risk
- Genetic predisposition with parents & half first degree relatives HLA B27 positive
- But requires additional environmental trigger
Females
- Less progressive spinal disease
- More peripheral disease

Aetiology

HLA-B27
- 95% of cases
HLA-B27 highly variable in general population
- 8% of Caucasians
- 50% of American Indians
- Negative in Negroes
HLA-B27 linked to susceptibility factor
- Genetic predisposition acted upon by environmental trigger factors
- GUT & GIT infections can be trigger
- Klebsiella infections implicated recently due to higher incidence in AS

Pathologenesis

Two basic lesions
- Enthesopathy
- Synovitis of Diarthrodial Synovial Joint
Enthesopathy
- Enthesis is insertion of tendon, ligament or capsule into bone
- Enthesitis affects
  - Ligament structures of Fibrocartilaginous joints
    - Intervertebral Discs
    - Manubriosternal Joints (MSJ)
    - Symphysis Pubis
  - Capsule attachments of Synovial joints
    - Hip
    - Shoulder
  - Ligament attachments
    - Spinous processes of vertebrae
    - Iliac Crests
    - Greater Trochanter
- Inflammatory process of the enthesis
  - Initial inflammatory erosion
    - Round cell infiltration (lymphocytes & plasma cells)
    - Granulation tissue
  - Repair via healing with fibrous tissue
    - Fills defect
  - Fibrous tissue ossifies
    - Forms new enthesis above original level of cortical surface
    - Result is irregular bony prominence
    - Sclerosis of adjacent cancellous bone

Synovitis

Similar changes to RA
- Villous proliferation of synovium
- Pannus destroys articular cartilage
- Joint ankylosed by fibrous tissue or bone
- Areas of cartilage may be preserved

Axial Skeleton Pathology

Discs
- Starts TL spine then works caudal & distal (cf. psoriatic arthritis which is opposite)
- Initially erosion of enthesis
  - Anderson lesion
- Localised area of destruction
  - Romanus lesion
- Early squaring
- Forms thin vertical projection from end plate
  - Marginal Syndesmophyte*
- Fuse leading to
  - Bamboo Spine
- *Compare with
  - Claw osteophytes
    - Seen with ageing
    - Osteophyte growing over bulging disc as it migrates anteriorly
  - Shelf osteophytes (traction osteophytes/ traction spurs)
    - With instability at that level & Osteoarthritis
    - Anterior & posterior
  - Syndesmophytes
    - Ossification of anterior annulus or ALL
    - Marginal or Non-marginal
      - Non-marginal (ALL ossification) – DISH
      - Marginal (Annulus ossification) – AS
MSJ / Pubic Symphysis / SIJ / Facet / Costovertebral Joints
- Initial inflammation
- Destruction of cartilage
- Replacement by fibrous tissue
- Finally ossification & obliteration

Large Synovial Joints Synovitis

Pannus & secondary ankylosis
Enthesopathy of capsule insertion
Ossifies
- Especially hip & shoulder

History

Young male
Teenager or young adult (2nd-3rd decade)
Lower Back Pain
- 1st feature in 75%
  - Insidious onset
  - Usually dull & poorly localized
  - Worse in morning & after inactivity
  - Improved by warming up
  - May get referred buttock pain
    - May be diagnosed as sciatica
Back stiffness
Chest pain & ↓ expansion
Neck pain & stiffness
Pain & swelling of joints

Age < 40 years onset back pain

Gradual atraumatic onset

Duration > 3/12

Morning stiffness

Improves with exercise

if all 5 features then 95% sensitive, 85% specific for AS

5 important diagnostic features of Anklyosing Spondylitis

Examination

Spinal
- Altered posture
  - Loss of cervical & lumbar lordosis
  - Increased thoracic kyphosis
  - Loss of vision to several paces
- “Wall Test”
  - Occiput / Scapulae / Buttocks / Heels all against wall
  - Unable to do in AS
- Tender over spinous processes
- Stiff LS spine
  - Decreased extension earliest & most severe
  - Decreased forward flexion
    - Schober’s Test (< 4cm over 10cm)
  - Decreased lateral flexion
- Painful & tender SIJ
- SIJ Stress Tests
  - Pain on forced flexion of ipsilateral hip & hyperextension of opposite hip
  - Faber’s test (pain on downward pressure on ipsilateral knee
- Tender ASIS
Decreased chest expansion
- Due to costovertebral joint ankylosis
  - Diaphragmatic breathing
  - < 1″ at 4th ICS (should be at least 7cm in young male)
Hip & shoulder
Symptoms & Signs similar to RA

Complications

Spinal

Spinal Fracture
- With trauma » “chalkstick fracture”
- Difficult to diagnose on XR because osseous spinal ligaments » CT useful
- May result in neurological deficit (75%)
- Epidural haematoma common
Craniocervical Instability
- Mechanism similar to RA with erosive synovitis
- Atlanto-occipital instability & Basilar invagination
Pseudarthrosis
- AKA Spondylo-discitis
- Unclear whether due to pathological fracture or erosive process of disease
Cauda Equina Syndrome
- Due to Spinal Stenosis

Extraspinal

Pauciarticular Arthropathy
- Hips & Shoulders
- Insidious onset of pain & stiffness
Peripheral Enthesopathy
- Pain & tender at sites of Entheses
- Pelvis
  - Crests, Ischial tuberosity, Iliac spines, Pubic symphysis, Greater trochanter
- Thorax
  - MSJ, Costosternal joints
- Heels (very common)
  - Achilles, Plantar fascia

Extraskeletal

Acute Anterior Uveitis
Aortitis
- With subsequent aortic incompetence
Pulmonary fibrosis
Colitis
Amyloidosis
- Nephrotic syndrome
Sarcoidosis
Prostatitis

Investigations

Laboratory tests

ESR elevated in 75%
CRP better indicator of disease activity
HLA B27 usually positive
RF negative

Xrays

Spinal Disease
- Loss of normal lordosis
- Erosive changes at insertion of ligaments on the spine
- Produces classical lesions
  - An area of bony erosion at the attachment of the annulus at anterolateral body
    - Anderson Lesion
- If becomes localised area of destruction (usually in lower thoracic spine) with new bone formation
  - Romanus Lesion (difficult to distinguish from discitis)
- New bone formation from edge of annulus producing vertical projection from end plate
  - Marginal Syndesmophyte
- Eventually see fusion of the syndesmophytes & ossification of the ALL
  - Bamboo Spine
- On the A-P film may see ossification of the interspinous ligament & the intertransverse ligaments
  - Tram-Track sign
Sacroiliac Disease
- Initial blurring of subchondral bone
- Then bone erosion & sclerosis
  - Postage stamp
- More on iliac side
  - Pseudowidening of joint
Pelvis
- Erosions or Whiskering at attachments of tendons / ligaments
  - At ischial tuberosities & crests
Hips & Shoulders
- Features of RA
- Bony ankylosis will follow often

Differential Diagnosis

Seronegative Arthropathies
- Reiters
- CIBD
DISH (Forestier’s Disease)
- Non-inflammatory with no SI joint involvement
Other causes of mechanical low back pain
- Mechanical / Nonspecific
- Infection
- Neoplasia

Treatment

Non-Operative

Simple analgesia
NSAIDS
Physiotherapy
- ROM & Postural exercises
- Maintain useful, functional posture
- Does not alter natural history

Radiotherapy

Observed to improve pain & ↓ progression
Risk of inducing malignancy ↓ the usage
May have isolated indications in peripheral involvement where NSAIDS contraindicated

Operative

General principles
- Treat coexisting hip pathology first
- Flexion extension views lumber & cervical spines
- Measure brow-chin / vertical angles
- Preoperative assessment C spine stability & pulmonary function
Goals
- Enable upright posture
- Relieve compression of viscera
- Improve diaphragmatic respiration
- Improve field of vision
Spine
- Corrective osteotomy
  - Indications
    - Severe deformity difficult to look forwards
    - Respiratory compromise
- Contraindications
  - Elderly
  - Aortic calcification
  - Poor general health
- Closing Wedge Osteotomy of Posterior elements
  - Single stage posterior procedure
  - V-shaped osteotomy of posterior arch
  - Laminae undercut & canal decompressed
  - May need posterior instrumentation
- Good correction
- Aorta most at risk
Hip
- Total Hip Replacement
- Good to excellent outcome & durability
- No ↑ loosening
- Main problem is Heterotropic Ossification
  - 10-20% get Brooker III or IV
  - Usual treatment indicated