Spondyloarthritis
Spondyloarthritis (SpA) is characterised by inflammation in the axial skeleton (sacroiliitis, spondylitis), peripheral joints, and entheses. Extraskeletal manifestations can occur such as anterior uveitis, psoriasis, and inflammatory bowel disease. HLA-B27 is the major genetic risk factor.
Epidemiology
The entire group of SpA has a global prevalence of 0.1% to 1.9%. AS is the largest subgroup. The association with HLA-B27 ranges from ~50% to 95%. In the general population HLA-B27 is present in 8-10% of Caucasians, and ~1% of the population develop a spondyloarthritis. About 5% of patients with chronic low back pain have a spondyloarthritis.
Classification
Previously SpA was viewed as consisting of interrelated subgroups that included ankylosing spondylitis (AS), reactive arthritis, or undifferentiated spondyloarthritis. The current thinking distinguishes between predominant axial SpA and predominant peripheral SpA.
Validated classification criteria exist for both axial and peripheral SpA. Sacroiliitis on MRI is an important radiological finding in classification.
The term spondyloarthritis is preferred over spondyloarthropathy due to the inflammatory nature of the condition.
Sometimes the term seronegative spondyloarthritis is used which means that the patient is negative for rheumatoid factor and anti-CCP. Unlike Rheumatoid Arthritis, the distribution of the affected peripheral joints is asymmetrical, with the large joints of the lower limbs being predominantly affected in peripheral spondyloarthritis.
Classification Criteria
Inflammatory Back Pain
Features of inflammatory back pain include the early age of onset (<40 years), stiffness that is worse with rest and improved with exercise, pain at night that wakes the patient up, and the absence of radicular symptoms. Response to NSAIDs is the rule. Many but not all individuals are HLA-B27 positive.
Examination findings include an abnormal Shober test, and extraarticular manifestations such as psoriasis, uveitis, and inflammatory bowel disease.
Features that aren't suggestive of inflammatory back pain are older age (>40 years), abrupt onset, history of trauma, radicular symptoms, weight loss, night sweats, fever, history of cancer, worsening with exercise, and generalised aching.
Calin criteria | Berlin criteria | ASAS criteria |
---|---|---|
|
|
|
(at least four of five present) | (at least two of four present) | (at least four of five present) |
Axial Spondyloarthritis
Axial spondyloarthritis is a spectrum that runs from nonradiographic axial SpA (nr-axSpA) to ankylosing spondylitis. All patients with AS start as nr-axSpA, but not all patients with nr-axSpA progress to AS.
In patients with back pain ≥ 3 months and age at onset < 45 years | ||
---|---|---|
Sacroiliitis on imaging*
plus ≥1 SpA feature† |
HLA-B27
plus ≥2 other SpA features† | |
SpA features†: | or | Sacroiliitis on imaging*: |
|
| |
or | ||
Definite radiographic sacroiliitis
according to modified New York criteria | ||
*Sensitivity 82.9%, specificity 84.4%; n = 649 patients with chronic back pain and age
at onset <45 years. Imaging arm (sacroiliitis) alone has a sensitivity of 66.2% and a specificity of 97.3%. †Elevated CRP is considered an SpA feature in the context of chronic back pain. |
Peripheral Spondyloarthritis
Arthritis* or enthesitis or dactylitis | ||
---|---|---|
Plus ≥ 1 of | or | Plus ≥ 2 of the remaining: |
|
| |
*Peripheral arthritis: usually predominantly lower limb and/or asymmetric arthritis.
IBP: inflammatory back pain. |
Clinical Features
There is a predilection for the axial skeleton and entheses. Sacroiliitis is the cardinal sign. HLA-B27 confers a genetic risk. Clinical manifestations are inflammatory low back pain, stiffness, and a late finding of limitation of spinal range of motion.
Extraarticular manifestations are acute anterior uveitis, psoriasis, and inflammatory bowel disease.
Peripheral features include asymmetrical, oligoarticular, lower limb predominant arthritis +/- enthesitis (e.g. plantar fasciitis, insertional Achilles tendonitis). This is compared to small joint symmetrical arthritis in Rheumatoid Arthritis.
Imaging
Plain film radiographic features are more typical of later stage disease, however MRI can detect early disease.
Radiologic features of ankylosing spondylitis include
- Sacroiliac joint: erosions, ankylosis, juxtaarticular osteopenia, ossification of the ligamentous attachment to the ischial tuberosity or iliac crest or the greater trochanter
- Spine: erosions at vertebral corners (shiny corners), squaring of the vertebral bodies (Romanus lesion), syndesmophytes, ossification of the annulus fibrosus and longitudinal ligament, erosions of the discovertebral junction, calcification of the intervertebral discs, pseudoarthrosis, and bone oedema especially if juxaarticular
MRI is the gold standard for assessment of inflammatory changes in the SIJ and spine.
Definitions of what constitutes a positive MRI of the SIJ and spine have been published by ASAS.
Tissue | Inflammatory Changes | Structural Changes |
---|---|---|
Bone marrow | Sacroiliitis (bone marrow edema or
osteitis) in one or both parts of the SI joint (sacral or iliac) |
Subchondral sclerosis
Erosions Fatty deposition Bone bridges or ankylosis |
Bone marrow edema related to SpA
is located periarticularly | ||
Synovium | Synovitis: depicted only by T1/
Gd-DTPA sequences; STIR sequences cannot differentiate between synovitis and physiologic joint fluid; synovitis is a rare lesion |
Bone bridges or ankylosis |
Joint capsule | Capsulitis: comparable to synovitis;
both anterior and posterior joint capsule can be affected |
Bone bridges or ankylosis |
Ligaments | Enthesitis: seen in the junction of
ligaments and tendons to the bone |
Degeneration of ligament |
Tissue | Inflammatory Changes | Structural Changes |
---|---|---|
Vertebral body | Inflammation (spondylitis) in the bone marrow, mainly in the corners | New bone formation
(syndesmophytes, ankylosis), eventually erosions or destruction of the vertebral body (e.g., fracture) Fatty degeneration |
Intervertebral disc | Inflammation
(spondylodiscitis) |
Ossification of the disc |
Facet and
costovertebral joints |
Inflammation with or
without involvement of the vertebral body |
New bone formation and ankylosis in
advanced stages |
Ligaments | Enthesitis, mainly of
the supraspinal and interspinal ligaments |
Degeneration of ligaments |
Management
Essential aspects of management include early diagnosis, education, and physiotherapy. Physiotherapy plays a role in restoring and maintaining posture and movement. Home exercises must be continued for life.
Medical management includes NSAIDs, anti-TNFα drugs (adalimumab, etanercept, infliximab), and more recently IL-17 inhibitors.
For peripheral spondyloarthritis sulfasalazine and methotrexate may play a role as DMARDs, but not for axial disease. Local corticosteroid injections can be useful in oligoarticular forms of arthritis.
Core Readings
M Ehrenfeld. Spondyloarthropathies. Best Practice & Research Clinical Rheumatology 2012 (26) 135–145.
2. M Dougados and D Baeten. Spondyloarthritis. Lancet 2011; 377: 2127–37
3. Taurog JD et al Ank Spond and Axial Spondyloarthropahty. NEJM 2016;374;2563-74
4. Sieper J. Developments in therapies for sponyloarthropathies. Nature Reviews Rheumatology;2012;8:280-7
5. Braun et al 2010 update of ASA/EULAR recommendations for management of AS. Ann Rheum Dis 2011;70:896-904