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HISTORY
Ankylosing spondylitis (AS) is
a systemic inflammatory disease that results in ossification
of joints and entheses primarily of the hip, spine, and peripheral
joints. The first signs of AS were first unearthed in the skeletal
remains of a 5000 year–old Egyptian mummy. (9)
Since then, such notable physicians as Realdo Columbo, (4) Bernard
Connor, (14)
Sir Benjamin Brodie (31)
Charles Fagge, (31)
and Carl von Rokitansky (31) all reported similar findings of
AS in cadaveric specimens and patients. However, the first well–known
description of AS was reported by W. von Bechterew in 1883.(3) Others,
such as Adolph Strumpell in 1897 (39)
and Pierre Marie in 1898 (33)
were also among the first to offer a classic description of AS.
Therefore, AS is also known as Bechterew Disease or Marie–Strumpell
Disease.
GENERAL OVERVIEW
Ankylosing spondylitis belongs
to a group of seronegative spondyloarthropathies. A chronic form
of arthritis, AS is estimated to affect 1.4 % of the general
population. (15)
Severity of the disease varies among individuals as well as remission
and exacerbation periods. Ankylosing spondylitis primarily affects
the spine and hip joints causing progressed bone fusion including
fusion of the costovertebral joints, erosion, destruction of
the vertebral endplates, osteophytes, subchondral sclerosis,
squaring of vertebral bodies, ossification of the intervertebral
disc, narrowing of joints, and osteoporosis. Fusion of the spine
mainly occurs at the lumbar level with progression cranially
to the cervical spine. Enthesopathy, or inflammation of bone
attachment to tendons, ligaments, and joint capsules also occurs.
The spine adopts a long bone persona and is easily susceptible
to fracture. As the spine undergoes chronic inflammation, the
patient develops a more pronounced curvature to lessen the severity
of pain (Fig. 1). The result is a fixed flexion deformity of the spine or otherwise
referred to as a "bamboo spine" when viewed radiographically
(Fig. 2). Such an
irregular posture contributes to a loss of horizontal gaze, physiologically
incorrect sagittal contour, physical embarrassment, respiratory
restriction, and a higher risk for trauma.
The etiology of AS is unknown.
More males seem to develop AS than females, but that may be due
to the severity of the disease in males to seek medical attention.
However, scientists believe that a genetic component exists which
could account for AS. Calin and Fries reported that 90 % of U.S.
Caucasians with AS tested positive for the HLA–B27 antigen.
(10)
Nevertheless, other studies believe that the HLA–B27 antigen
is a weaker indicator for AS than originally reported. Furthermore,
elevated ESR is also associated with AS. (48)
Diagnostic criteria were established
by Calin in 1977 that composed of five items. (11)
Sacroiliitis is predominately the first sign of AS manifesting
as low back pain. Other criteria were established, such as the
Rome criteria in 1961,(24)
the New York criteria in 1966, (43)
the Modified New York criteria in 1982. (43)
Nevertheless, physicians generally look for signs of tenderness
in the sacroiliac joints, Schober's test for lumbar flexion,
Mennell's sign, chest expansion measurements, onset of pain,
radiographic evaluation, and measurement of kyphotic deformity
by the Cobb method and the chin–brow technique.
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