Ankylosing Spondylitis

Definition

 

A HLA B27 positive, seronegative spondyloarthropathy with sacroiliac joint & spine involvement

Mainly affects the cartilaginous joints of the axial skeleton

 

Diagostic Criteria (1966 New York)

 

1. Positive X-ray Sacroiliitis

 

Sacroilitis Ankylosing Spondylitis

 

2. One or more of

- lumbar spine pain 

- lumbar spine stiffness

- chest expansion < 1" at 4th intercostal space

 

Epidemiology

 

1/1000 Caucasian

 

FHx in 15 - 20% patients

 

M:F = 3:1

 

Females

- less progressive spinal disease

- more peripheral disease

 

Average onset 25 years

 

Aetiology

 

HLA-B27

 

Autosomal Dominant

- 95% of cases

 

B27 linked to susceptibility factor

- ? Trigger

- ? GIT infection with Klebsiella

 

Pathology

 

Two basic lesions

1. Enthesitis

2. Synovitis of Diarthrodial Synovial Joint

 

Enthesitis

 

Enthesis is insertion of tendon, ligament or capsular into bone

 

A.  Discs / Manubriosternal joints / Symphysis pubis

B.  Hip / Shoulder

C.  Spinous processes of vertebrae / Crests / GT

D.  Pelvis Crests / GT /  Ischial tuberosities / Iliac spines / Pubic symphysis

E.  Heels / Achilles / Plantar fascia

 

Synovitis

 

Similar changes to RA

- villous proliferation of synovium / pannus destroys cartilage 

- joint ankylosed by fibrous tissue

- converted to bone

 

TL spine

 

A. Spondylodiscitis / Anderson lesion 

- erosion of enthesis at anterolateral annulus at endplate

 

B.  Romano's lesion

- lesions heal by forming new bone / early squaring 

 

C.  Marginal syndesmophyte

- with repeated episodes forms thin vertical bone due to ossification of annulus fibrosis

 

Ankylosing Spondylitis Marginal Syndesmophytes

 

D.  Bamboo spine

- fusion / bony disc casing 

 

 Ankylosing SpondylitisAnkylosing Spondylitis CT Spine SagittalAnkylosing Spondylitis CT Spine Coronal

 

Extraskeletal Manifestations

 

Acute Anterior Uveitis 20-40%

Aortitis + secondary Aortic Regurgitation 90%

Pulmonary fibrosis

 

Symptoms

 

Lower back pain

- insidious onset

- usually dull & poorly localised

 

Back stiffness

- worse in am & after inactivity

- improved by warming up

- improves with exercise

 

Neck pain & stiffness

 

Signs

 

1.  Altered posture

- increased thoracic kyphosis

- loss of cervical & lumbar lordosis

 

2.  Positive "Wall Test"

- cannot put heels / buttocks and Occiput on wall

 

3.  Reduced ROM

- decreased extension earliest & most severe

- decreased flexion

- Schober's Test < 4cm

- decreased lateral flexion

 

4.  Pain & tender SIJ

- SIJ Stress Tests / FABER  

- pain on downward pressure on knee in fig 4 

 

5.  Decreased chest expansion 

- <1" at 4th ICS

- secondary to costovertebral joint ankylosis

 

Bloods

 

ESR

- increased in 75% / elevated for life-time

 

HLA-B27

- positive 90%

 

X-ray

 

Sacro-iliac joint

- erosion / sclerosis / finally ankylosis

 

Spine

- marginal erosions / squaring of anterior body concavity

- marginal syndesmophytes

- bamboo spine

 

Ankylosing Spondylitis AP C SpineAnkylosing Spondylitis Latera C SpineAnkylosing Spondylitis Lateral C spine 2

 

Hip & Shoulder

- concentric joint space narrowing

- bony ankylosis

- protrusio

 

DDx

 

Seronegative Seroarthropathies

- Reiters / Psoriasis / Enterocolitis

 

DISH 

- °Inflammatory / no SIJ involvement

- non-marginal syndesmophytes

 

Scheuermann's

- end plate changes

 

Management

 

Non-operative

 

Simple analgesia

NSAID

Physio

Maintain ROM & posture especially extension

 

Operative Management

 

Issues

 

1.  Spinal fracture

2.  Kyphotic deformity

3.  THR

 

Spinal Fractures

 

Ankylosing Spondylitis Thoracic Fracture CTAnkylosing Spondylitis Thoracic Fracture CT CoronalAnkylosing Spondylitis Fracture MRI Spine

 

Pathology

- fused spine acts as long bone

- fracturs at cervico-thoracic junction / thoraco-lumbar junction

 

Non operative management

- stable, minimally displaced lesion

- no neurological deficit

 

Operative Indications

- unstable fractures

- incomplete neurological deficit

- failure of bracing

 

Ankylosing Spondylitis Thoracic Fracture Stabilisation APAnkylosing Spondylitis Thoracic Fracture Stabilisation Lateral

 

Kyphosis

 

Indication for corrective osteotomy

 

A.  Severe cervical kyphotic deformity

- difficulty in looking forward / opening mouth

 

B.  Respiratory compromise

- chin on chest position

 

Contra-indication

- elderly

- aortic calcification

 

A.  Cervical

 

Use brow-chin angle to calculate osteotomy size

 

Closing wedge extension osteotomy 

- fulcrum must be posterior elements of C7-T1

- avoids vertebral artery at C6

- canal is relatively wide at this level

- C8 nerve root most mobile & expendable

- decompress C8 nerve roots

- short-acting GA when close osteotomy

- wake up test

- HTB post-operatively

 

Belanger et al JBJS Am 2005

- 26 patients

- average 38o correction

- 1 quadriplegia who died due to subluxation at osteotomy site

- 2 delayed unions

- 5 patients had irritation of C8 nerve root

 

B.  Thoracolumbar

 

Options

 

Smith-Peterson Osteotomy with instrumentation

- osteotomies in SP above & below central vertebra

- centre of correction is disc / must be healthy

- 10o per level / maximum 30o

- major risk is to aorta

 

Pedicle subtraction osteotomy

- 30 - 40o per level

- centre of correction vertebral body

- more dangerous / increased correction with better union

 

THR

 

Good functional outcome

- no increased loosening seen

- must restore centre of rotation

 

Main complication is HO

- 20% > Brooker III

- indomethacin indicated