Ankylosing Spondylitis
Definition
Chronic inflammatory condition of the spine and sacro-iliac joints characterised by osseous proliferation and associated with HLA B27
Bilateral and asymmetric involvement predominate PIP, DIP & MCP joints may be involved. Osteoporosis, erosions and deformity are less marked than in RA
Osseous proliferation may be exuberant
Incidence
Affects 1 per 1,000 people in Western Europe
Prevalence ~ 1% whites
Low incidence in black Americans and Negro's
Classic Ank Spond ® Male : Female 3 or 4:1
May be the incidence is equal but female form less likely to have progressive spinal deformity.
Onset usually aged 15 - 25 years ( less than 40 years)
Aetiology
Genetic predisposition HLA B27 but only a relatively small percentage of people with HLA B27 go on to have Ankylosing Spondylitis
Virtually all patients with Ank Spond have HLA B27.
50% of first degree relatives of spondylitic patients also HLA B27 and of this group 20% ® spondylitis
Trigger ?, similar to Reiters, ulcerative colitis, ? lymphatic drainage to SI and spinal region important.
? Environmental trigger
Pathology
Primary process is enthesopathy, inflammation at fibro-osseous junctions of syndesmotic joints (inter vertebral discs, sacroiliac ligaments, symphysis pubis, manubrium sterni and bony insertions of ligaments and tendons; entheses)
Three stages of the disease
- Inflammatory reaction with round cell infiltrate, granulation tissue and bony erosion
- Replacement of granulation tissue with fibrous tissue
- Ossification of fibrous tissue ® ankylosis
Also see synovitis of diarthrodial joints
Fibroplasia ® cartilaginous metaplasia ® chondro-ossification and bony ankylosis which is typical of Ank Spond (and psoriasis) but rare in RA
SI joints, facet joints ® joint destruction, costo-vertebral joints also frequently involved ® reduced respiratory excursion
Clinical Features
Many remain undiagnosed
Insidious onset ® back-ache and stiffness
May have referred pain similar to sciatica
In woman diagnosis often delayed, progressive disease is less common and there is likely to be more peripheral joint involvement and less spinal involvement
Pain and swelling of other joints and at the point of tendon insertions (enthesopic features)
10% start as an asymmetrical poly arthritis
Morning stiffness with improvement following exercise
20% have a peripheral arthropathy ® up to 35% eventually
Loss of spinal mobility (extension first) with flattening of lumbar lordosis
Wright / Schober
Mark two points one 10cm above and one 5cm below the level of the iliac crests and flex ® should lengthern 5cm
Wall test ® heels, buttock and scapulae all should be able to touch but if decreased extension unable to do this
Chest expansion should be at least 5cm and is often markedly reduced in this disease due to costo-chondral arthrosis (not a reliable sign in the elderly or in those with COAD)
Ocular inflammation occurs in ~ 1/3 of patients (uveitis ~20% and conjunctivitis in 25%)
Aortic valve disease rarely a clinical problem present in ~ 3% and pericarditis and myocarditis may also be a feature
Occasionally pulmonary fibrosis
Associated with weight loss, fatigue, low grade fever
Spinal fractures (? stress #) often ® pseudarthrosis at the disco-vertebral junction. Epidural haematomas seen in ~ 20%
Cervical spine #'s heal well in halo
If neurological involvement 46% chance of being fixed and 29% mortality
Risk of massive epidural haemorrhage may ® ascending paralysis
Investigations
Rh factor is negative
ESR increased during active phase
HLA B27 present in 95% of cases (present in 5 - 10% normals)
95% of whites with Ank Spond have HLA B27 but only 60% of blacks
ALP & CPK increased
X-Rays
Erosions / fuzziness of the SI joints often the earliest feature ® bony ankylosis
Vertebral squaring due to flattening of the normal anterior convexity secondary to inflammation at point of annulus insertion ® ossification across the inter-vertebral discs ® bamboo spine
Peripheral joints erosive arthritis and ankylosis
Protrusio Acetabulae may be a feature
Three types of disco-vertebral lesions
- Central intra osseous discal displacement (Schmorls' node)
- Enthesopathy, peripheral lesion
- Both peripheral and central
Diagnostic Criteria
- Low back pain of more than 3/12 duration
- Pain & stiffness in the thorax
- Limited chest expansion
- Limited lumbar motion
- Past or present iritis
- Radiological sacroiliitis
- Radiological syndesmophytes
Need 4 of the five clinical criteria or the radiological criteria plus one other
Differential Diagnosis
Other sero-negative spondylo-arthropathies ® vertebral and SI joint disease (Reiters, psoriatic arthritis, ulcerative colitis & Crohns disease, Whipples disease, Behcets syndrome) all show some familial aggregation and are associated with HLA B27
Forestiers Disease
(Ankylosing Hyperostosis) Common disorder predominantly in older men ® widespread ossification of ligaments and tendon insertions (ALL in the cervical spine and in the lumbar spine ® pronounced but asymmetrical inter vertebral spur formation and bridging) Not an inflammatory disease and spinal pain and stiffness seldom severe. SI joints are not eroded and ESR normal. Associated with obesity and diabetes
Treatment
Anti inflammatory medication
Analgesics
Physiotherapy etc to preserve movement and prevent deformity
Rest and immobilisation contraindicated as ® increased osteoporosis and ankylosis
Significant hip involvement ® THR (often left with limited ROM)
Spinal osteotomy (lumbar or cervical) to "improve outlook on life"
Prognosis
Age of onset is the most important factor in determining prognosis and outcome