ANKYLOSING SOPNDYLITIS

•僵直性脊椎炎

Definition

• AS is an inflammatory disorder of unknown etiology that primarily affects the spine, axial skeleton, and large proximal joints of the body.

Prevalence and genetic aspects

• Prevalence: 1.29/1000 persons in U.S.

• Genetic aspects: 90% AS patients: HLA- B27: (+), but 8% of normal population also have positive HLA-B27.

Family history and sex distribution

• A positive family history of AS may be found in 15% to 20% of cases.

• Male: Female: 3:1

• Age: typical: second through fourth decades

Pathology

• The axial skeleton: sacroiliac (S-I) joints and intervertebral disk spaces

• The large joints: hips, knees, shoulders

• Extraskeletal sites: inflammatory fibrous tissue include the uveal tract, aortic root wall, and heart valves

Pathology

• Fibrocartilage is the primary site of inflammation, ligamentous-bony junctions (enthesitis), periositis, and synovitis

• Initial inflammation, then fibrosis and often ossification, which lead to bony ankylosis

Clinical presentation

• Classic: intermittent or persistent low back pain and stiffness that is worse in the morning and after prolonged rest, and the pain is relieved by physical activity

• The pain centered in the lumbarsacral spine, also in the buttocks and hips

Clinical presentation

• Chest pain: thoracic spine neck or shoulder pain and stiffness

• Peripheral arthritis: Hip: major disability source of AS; Heel: local enthesopathy of the calcaneus, Achilles tentinitis is common

Extraskeletal manifestations

• Aortic valve regurgitation: in 5% of patients, complete heart block may develop

• Pulmonary: Restriction of the thoracic cage can reduced lung volumes

• Acute iritis: unilateral, secondary glaucoma

Clinical criteria for AS

• Low back pain and stiffness for more than 3 months, improved by exercise, unrelieved by rest

• Limitation of lumbar spine motion in both sagittal and frontal planes

• Limitation of chest expansion

Radiologic criterion

• Sacroiliac joints: the earlist radiographic changes of AS, grade: 1. Punched- out erosions 2. Pseudo-widening of the joint 3. Adjacent sclerosis 4.Bony bridging of the joint with complete loss of joint space

Diagnosis

• Define AS: sacroiliitis grade 2 or more bilaterally or grade 3-4 unilaterally associated with at least one clinical criterion

Physical examination

• Sacroiliac (SI) joints: Lateral compression of the pelvis: elicit pain in the involved joints

• Costovertebral involvement: decreased chest expansion,< 5 cm during inspiration in the adult

• Extraaxial joint involvement: proximal and asymmetric

Physical examination

• Spine: loss of spinal (lateral, flexion, and extension) motion occurs early: Finger to floor; occipital to wall

• Progression: loss of lordosis, kyphosis of the thoracic spine, fixed flexion of the neck

Physical examination

• Schober test: make marks between the lumbosacral junction and a point 10 cm above, then the patient makes maximum forward flexion: less than 5 cm of distraction is abnormal

Laboratory studies

• HLA-B27: not a routine examination for AS patients ( not diagnostic criteria)

• ESR: elevated but not correlate well with disease activity

• Spine: chondritis then ossification lead to bony bridging of adjacent vertebrae (syndesmophytes)

Laboratory studies

• Advanced ossification of AS is named “ bamboo spine”

• Periostitis of the vertebral body leads to early “squaring”

Treatment

• Physical therapy: maintenance of erect posture, sleeping on a firm mattress with a small pillow

• Walking and swimming are excellent ways to maintain joint mobility

Treatment

• Drugs: 1. Indomethacin: is the most commonly used drug 2. Other NSAIDs: naproxen (Naposin), sulindac, etc. 1,2: for pain relief

• 3. Sulfasalazine: relieves spinal symptoms and decreases acute-phase reactants. Side effect: 1% neutropenia

Treatment

• Systemic steroids: used with caution

• Intraarticular corticosteroids: be useful for acutely inflamed joints

• Surgery: total hip replacement, cervical and lumbar osteotomies to relieve severe kyphosis

Prognosis

• Most patients: maintain exercise and take medicine: relatively normal lives

• < 10% patients: relentless developing

• Survival curves of AS: similar to general population

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