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

imaging modality of choice in patients with advanced ankylosing spondylitis in whom there is suspicion of cervical spine fracture.

superior to radiographs and MRI in demonstrating injuries.

supplements scintigraphy in evaluating areas of increased uptake.

some normal variants of the SI joints may mimic features of sacroiliitis.

chronic structural changes such as joint erosions, subchondral sclerosis, and bony ankylosis are better visualized on CT than on MRI or radiographs 15-17.

may be useful in selected patients with normal or equivocal findings on sacroiliac joint radiographs.

See: cardiovascular manifestations of ankylosing spondylitis CT Plain radiograph may be normal, or may reveal cardiomegaly. See: thoracic manifestations of ankylosing spondylitis Cardiac These lesions may resemble tuberculosisВ infection and bullae may become infected. Radiographs of the lungs may demonstrate progressive fibrosis and bullous changes at the apices.

Marrow edema of acromion process, at the site of origin of deltoid muscle has been described as a very specific sign of the disease.

Shoulder joint involvement is not uncommon and demonstrates a large erosion of the anterolateral aspect of the humeral head, producing a 'hatchet' deformity.

Hands are generally involved asymmetrically, with smaller, shallower erosions and marginal periostitis. Knees demonstrate uniform joint space narrowing with bony proliferation. There can be bridging or fusion of the pubic symphysis. Whiskering of the pelvic bones primarily affects the ischial tuberosities, resulting from ossification of the ligamentous origins.

Hip involvement is generally bilateral and symmetric, with uniform joint space narrowing, axial migration of the femoral head sometimes reaching a state of protrusio acetabuli,В and a collar of osteophytes at the femoral head-neck junction. pseudoarthrosesВ may form at fracture sites.enthesophyte formation from enthesopathy.apophyseal and costovertebral arthritis and ankylosis.ossification of spinal ligaments, joints and discs (with fatty marrow within the ossified disc, best seen on MRI).linear ossification along the central spine representing interspinous ligament ossification can give a ' dagger spine' appearance on frontal radiographs.syndesmophytes are classically described as paravertebral ossification running parallel to the spine.diffuse syndesmophytic ankylosis can give a ' bamboo spine' appearance.noninfectious spondylodiscitis: Andersson lesion.early spondylitis is characterized by small erosions at the corners of vertebral bodies with reactive sclerosis: Romanus lesionsВ of the spine ( shiny corner sign).at end-stage, the SI joint may be seen as a thin line or not visible.subchondral erosions, sclerosis, and proliferation on the iliac side of the SI joints.the sacroiliac jointsВ first widen before they narrow.sacroiliitisВ is usually the first manifestation 5В and is symmetrical and bilateral.The axial skeleton is predominantly affected, although in ~20% of cases the peripheral joints are also involved. Overall, ~5% of people positive for HLA-B27 develop ankylosing spondylitis. Although approximately 90% of Caucasian individuals with ankylosing spondylitis have the HLA-B27 gene, it is important to note this gene is present in 8-9% of people of Northern European ancestry 5. Other possibly contributing genes include ERAP-1, IL23RВ and TNF-associated genes 22. HLA B27 is the gene with the strongest association. Patients are rheumatoid factor (RF) negative, hence seronegative. apical/upper lobe predominant interstitial lung diseaseВ with small cystic spaces (in ~1% of patients) 4.inflammatory bowel disease: ulcerative colitis/ Crohn disease.The disease usually manifests in young adults, with the first symptoms becoming evident in the third decade, although up to 18% of cases manifest in the second decade.

According to some research men tend towards more severe disease 28. Traditionally it was thought there was a male predilection of 3:1 or more, however the gender predilection of the disease is a matter of recent debate and research (females may be under-diagnosed).

Bamboo spine