What Is It? Ankylosing Spondylitis (AS) is a chronic inflammatory disease characterized
by pain and progressive stiffness. It is part of a group of rheumatic diseases
termed seronegative spondyloarthropathies (vertebral joints) that share the human
antigen HLA-B27. Ankylosing spondylitis is seronegative (serum negative) because a rheumatoid factor is not detected in the patient's blood (serum).
Ankylosing spondylitis is considered to be hereditary, although environmental factors have been suggested. Most people with the HLA-B27 antigen do not develop AS. It is known to affect white males about four times as often as females. Onset typically occurs between the ages of 15 and 45.
In the early stages of the disease, the sacroiliac joints (back of the pelvis) become inflamed and painful. As the disease progresses, ossification is triggered by
the body's defense mechanism. Ossification causes new bone to grow between vertebrae
eventually fusing them together increasing the risk for fracture. Further, ossification
may affect spinal ligaments causing spinal canal stenosis (narrowing), which can
result in neurologic deficit.
Other symptoms may include:
>Low back pain that
may spread down into the buttocks and thighs. Pain varies in intensity, duration,
and is episodic. Stiffness is usually worse in the morning and improves with exercise.
>Limited motion in the lumbar spine.
>As the disease progresses, the patient
may notice the discomfort moves up the spine.
>The thoracic region may be affected
by pain, stiffness, and limited chest expansion.
>Pain, tenderness, and stiffness
in the shoulders, hips, knees, and heels.
>Cauda Equina Syndrome (specific nerve
compression) may develop causing bilateral lower extremity numbness, weakness,
and incontinence.
>Inflammation of the intervertebral disc or disc space (spondylodiscitis)
is a common complication caused by the hardening/thickening of fibrous tissue
(sclerosis) affecting vertebral end plates. The resultant abnormal vertebral motion
almost always causes pain.
>Spinal deformity: kyphosis (humpback), lordosis (swayback).
Diagnosis
General health and family medical history is important because ankylosing
spondylitis can be hereditary. Ankylosing spondylitis may or may not be associated
with nonskeletal diseases such as uveitis (eye inflammation), prostatitis (prostate
inflammation) and certain disorders affecting cardiac and pulmonary function.
A blood workup will reveal the HLA-BA27 antigen. A physical examination often
includes the following:
Schober Test: Limited motion in the lumbar spine is
symptomatic of AS. The Schober test measures the degree of lumbar forward flexion
as the patient bends over as though touching their toes. Progressive loss of spinal
motion is correlated with x-ray findings.
Gaenslen Test: Sacroiliac pain is
often found in the early stage of AS. Gaenslen's maneuver stresses the sacroiliac
joints. Increased pain during this maneuver could be indicative of joint disease.
When ankylosing spondylitis affects the thoracic spine normal chest expansion may be compromised.
The amount of chest expansion is measured from deep expiration to full inspiration.
Measurements significantly less than one inch (normal chest expansion) could indicate
AS.
General range of motion measures the degree to which a patient can perform
movements of flexion, extension, lateral bending, and spinal rotation. Asymmetry
may also be noted.
Neurologic Evaluation
A neurologic evaluation is mandatory
for patients presenting with a spine disorder. The following symptoms are assessed:
pain, numbness, paresthesias (e.g. tingling), extremity sensation, and motor function,
muscle spasm, weakness, and bowel/bladder changes.
Radiographic Evidence
Plain
radiographs (x-rays) are standard for AS. A CT Scan or MRI may be ordered to evaluate
bone and soft tissues (e.g. spinal canal) in greater detail. These tests reveal
changes in the spine affected by AS.
>Characteristic bilateral sacroiliac changes
may appear as blurry erosions (wearing away) or hardening/thickening of fibrous
tissue (sclerosis) on either side of the joint(s).
>Loss of cartilage spacing
in the facet joints, which fuse and become indistinguishable.
>Natural spinal
curvature lost and presentation of abnormal kyphosis (humpback) and/or lordosis
(swayback).
>Spinal fractures anywhere in the spinal column. A CT Scan or MRI
may detect epidural bleeding common following spinal fracture. This bleeding may
cause a semisolid swelling (hematoma) causing compression of neural elements.
Fractures may lead to neurologic deficit and/or spinal deformity.
>Lumbar vertebrae
may appear abnormally square from erosion that has occurred where bone meets fibrous
tissue during the inflammatory phase.
>'Bamboo Spine' is typical of ankylosing spondylitis and results
from ossification of the annulus fibrosus, the anterior longitudinal ligament,
and bony bridges that form across the intervertebral spaces.
