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Ankylosing spondylitis

Dr Avush Goel and Dr Frank Gaillard ® et al.

Ankylosing spondylitis (less commonly known as Bechterew disease and Marie Striimpell disease) is aseronegative spondyloarthropathy, which as the name suggests, results in fusion (ankylosis) of the spine andsacroiliac ISP joints, although involvement is also seen in large and small joints.

Epidemiology

There is male predilection of 3:1 or more. It usually manifests in adults, with the first symptoms becomingevident in the third decade, although up to 18% of cases manifest in the second decade.

Pathology

Genetics

Patients are rheumatoid factor (RF) negative (hence seronegative). Approximately 90% of Caucasian

individuals have the HLA-B27 gene 5.

Associations

•anterior uveitis

•psoriasis•ulcerative colitis/Crohn disease

•upper lobe predominant interstitial lung disease with small cystic spaces (occurs in ~1% of patients) 4

•aortic valve disease/aortitis

•amyloidosis (rare)

Radiographic features

Features predominantly affect the axial skeleton although can involve the peripheral joints in -20% of cases.

Plain radiograph

Sacroiliac joints

•sacroiliitis is usually the first manifestation 5 and is symmetrical and bilateral

•joints widen before they narrow•subchondral erosions, sclerosis and proliferation on the iliac side of SI joints

•at endstage, the SI joint may be a thin line or not visible

See: grading of sacroiliitis.

Spine

early spondylitis is characterised by small erosions at the corners of vertebral bodies with reactivesclerosis (Romanus lesions of the spine: shiny corner sign!vertebral body squaringdiffuse syndesmophyitic ankylosis can give a "bamboo spine" appearanceinterspinous ligament calcification can give a "dagger spine" appearanceossification of spinal ligaments, joints and discs (with fatty marrow within ossified disc, best seen onMRT)

pseudoarthroses may form at fracture sitesenthesophyte formation from enthesopathynon-infectious spondylodiscitis: Andersson lesion

Hips

Hip involvement is generally bilateral and symmetric, with uniform joint space narrowing, axial migration ofthe femoral head, and a collar of osteophytes at the femoral head-neck junction.

Knees

Knees demonstrate uniform joint space narrowing with bony proliferation.

Hands

Hands are generally involved asymmetrically, with smaller, shallower erosions and marginal periostitis.

Shoulders

Shoulder joint involvement is not uncommon and demonstrate large erosion of anterolateral aspect of humeralhead producing 'hatchet' deformity.

Chest

Radiographs of the lungs may demonstrate progressive fibrosis and bullous changes at the apices. These lesionsmay resemble tuberculosis infection and bullae may become infected.

CT

may be useful in selected patients with normal or equivocal findings on sacroiliac joint radiographsjoint erosions, subchondral sclerosis, and bony ankylosis are better visualised on CTsome normal variants of the SI joints may mimic features of sacroiliitissupplements scintigraphy in evaluating areas of increased uptakesuperior to radiographs and MRI in demonstrating injuries

o imaging modality of choice in patients with advanced ankylosing spondylitis for whom there issuspicion of cervical spine fracture

sagittal reformats should be obtained as axial images poorly assess the transverse fracture plane

MRI

may have a role in early diagnosis of sacroiliitissynovial enhancement on MR correlates with disease activity measured by inflammatory mediatorsenhancement of the interspinuous ligamants is indicative of an enthesitisincreased T2 signal correlates with edema or vascularised fibrous tissuesuperior to CT in detection of cartilage, bone erosions, and subchondral bone changesuseful in following treatment results in patients with active ankylosing spondylitis

Bone scintigraphy

•may be helpful in selected patients with normal or equivocal findings on sacroiliac joint radiographs

•qualitative assessment of accumulation of radionuclides in the SI joints may be difficult due to normaluptake in this location, thus quantitative analysis may be more useful

•ratios of SI joint to sacral uptake of 1.3:1 or higher is abnormal

Treatment and prognosis

Treatment includes NSAIDs, physiotherapy and, for more severe cases, anti-TNF-alpha therapy.

Complications

•fractureo diffuse paraspinal ossification and inflammatory osteitis creates a fused, brittle spine, susceptible to

fracture, even with minor traumao more common at the thoracolumbar and cervicothoracic junctionso recognition of minimally displaced fractures is difficult due to osteopenia and deformity, and it

is important to specifically search for disk space widening and discontinuity of the ossifiedparaspinal ligaments

also known as "carrot stick fractures" 15

•Andersson lesion: inflammatory spondylodiscitis that occurs in association with ankylosing spondylitisand results in a disc pseudarthrosis

•rare neurological complications include transverse myelitis and/or cauda equina syndrome 16, 17

Differential diagnosis

•general spine: enteropathic arthritis

•cervical spine: juvenile rheumatoid arthritis tJRAl

•diffuse idiopathic skeletal hyperostosis

See also

•differential diagnosis of erosive arthritis

•polyarticular arthropathy

Related articles

Arthritides

•autoimmuneo seronegative spondvloarthritides

ankylosing spondylitisbamboo spinedagger signhatchet signshiny corner sign

enteropathic arthritispsoriatic arthritis[+]reactive arthritis (Reiter syndrome)undifferentiated spondvloarthritissigns[+]

o Jaccoud arthropathyo juvenile idiopathic arthritiso lvme arthritiso rheumatoid arthritis[+]o systemic lupus erythematosus

•degenerative[+]•depositional[+]• infectious[+]•miscellaneous disorders[+]•related articles [+]

References