A chronic, usually progressive inflammatory bone disease, ankylosing spondylitis primarily affects the sacroiliac, apophyseal, and costovertebral joints, along with adjacent soft tissue. The disease (also known as rheumatoid spondylitis and Marie-Strmpell disease) usually begins in the sacroiliac joints and gradually progresses to the lumbar, thoracic, and cervical regions of the spine. Deterioration of bone and cartilage can lead to formation of fibrous tissue and eventual fusion of the spine or peripheral joints.
Ankylosing spondylitis affects men 2 to 3 times more than it does women. Progressive disease is well recognized in men, but the diagnosis is commonly overlooked or missed in women, who tend to have more peripheral joint involvement.
Causes
· Direct cause unknown
· Familial tendency; more than 90% of patients are positive for human leukocyte antigen (HLA)-B27
· Presence of circulating immune complexes suggests immunologic activity
Pathophysiology
Spondylitis involves inflammation of one or more vertebrae. Ankylosing spondylitis is a chronic inflammatory disease that predominantly affects the joints between the vertebrae of the spine, and the joints between the spine and the pelvis. Fibrous tissue of the joint capsule is infiltrated by inflammatory cells that erode the bone and fibrocartilage. Repair of the cartilaginous structures begins with the proliferation of fibroblasts, which synthesize and secrete collagen. The collagen forms fibrous scar tissue that eventually undergoes calcification and ossification, causing the joint to fuse or lose flexibility.
Involvement of the peripheral joints or soft tissues is a rare occurrence. The disease waxes and wanes, it can go into remission, exacerbation, or arrest at any stage.
Signs and symptoms
· Intermittent low back pain most severe in the morning or after inactivity and relieved by exercise
· Mild fatigue, fever, anorexia, and weight loss
· Pain in shoulders, hips, knees, and ankles
· Pain over the symphysis pubis
· Stiffness or limited motion of the lumbar spine
· Pain and limited chest expansion
· Kyphosis
· Iritis
· Warmth, swelling, or tenderness of affected joints
· Small joints, such as toes, may become sausage-shaped
· Aortic murmur caused by regurgitation
· Cardiomegaly
· Upper lobe pulmonary fibrosis, which mimics tuberculosis, that may reduce vital capacity to 70% or less of predicted volume
Diagnostic test results
· HLA typing test shows serum findings that include HLA-B27 in about 95% of patients with primary ankylosing spondylitis and up to 80% of patients with secondary disease.
· Laboratory tests show slightly elevated erythrocyte sedimentation rate, serum alkaline phosphate levels, and creatine kinase levels in active disease.
· Serum immunoglobulin (Ig) profile shows elevated serum IgA levels.
· X-ray studies define characteristic changes, such as bilateral sacroiliac involvement (the hallmark of the disease), blurring of the joints' bony margins in early disease, patchy sclerosis with superficial bony erosions, eventual squaring of vertebral bodies, and “bamboo spine” with complete ankylosis.
Treatment
· No treatment that reliably halts progression
· Physical therapy to delay further deformity—good posture, stretching and deep-breathing exercises and, in some patients, braces and lightweight supports
· Heat, warm showers, baths, ice
· Nerve stimulation
· Nonsteroidal anti-inflammatory analgesics, such as aspirin, indomethacin, sulfasalazine
· Corticosteroids
· Tumor necrosis factor inhibitors
· Hip replacement
· Spinal wedge osteotomy
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SPINAL FUSION IN ANKYLOSING SPONDYLITIS
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