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U N I T 1 2
Musculoskeletal Function
Ankylosing Spondylitis
Ankylosing spondylitis is a chronic, systemic inflamma-
tory disease of the joints of the axial skeleton manifested
by pain and progressive stiffening of the spine.
3,4,51
The
disease usually begins in late adolescence or early adult-
hood. The incidence is greater in men than in women,
and symptoms are generally more prominent in men.
Pathogenesis.
Although the pathogenesis of ankylos-
ing spondylitis has not been established, the presence
of mononuclear cells in the acutely involved tissue
suggests an immune response. Epidemiologic findings
indicate that genetic and environmental factors play a
role in the pathogenesis of the disease. The HLA-B27
allele remains one of the best-known examples of an
association between a disease and a hereditary marker.
Approximately 90% of those with ankylosing spondyli-
tis possess the HLA-B27 allele, which also is present in
approximately 5% to 15% of the normal population.
4
Several theories have been advanced to account for the
association between HLA-B27 and ankylosing spondy-
litis. One possibility is that it predisposes to ankylosing
spondylitis by influencing the body’s endogenous flora.
52
Clinical Manifestations.
The typical musculoskeletal
lesion associated with ankylosing spondylitis is inflamma-
tion, or
enthesitis
, at sites where tendons and ligaments
attach to bones. Typically, the disease process begins
with bilateral involvement of the sacroiliac joints and
then moves to the smaller joints of the posterior elements
of the spine (Fig. 44-8). The result is ultimate destruction
of these joints with ankylosis or posterior fusion of the
spine. The vertebrae take on a squared appearance and
bone bridges fuse one vertebral body to the next across
the intervertebral disks.
51
Progressive spinal changes
usually begin with the sacroiliac area and then move up
the spine to involve the costovertebral joints and cervi-
cal spine. Occasionally, large synovial joints (i.e., hips,
knees, and shoulders) may be involved. The disease spec-
trum ranges from an asymptomatic sacroiliitis to a pro-
gressive disease that can affect many body systems.
The usual presenting symptom is back pain that may
be persistent or intermittent.
3,4,51
The pain, which becomes
worse when resting, particularly when lying in bed, may
also involve the buttocks and hip areas, and can radiate to
the thigh in a manner similar to that of sciatic pain. Mild
physical activity or a hot shower helps reduce pain and
stiffness. Sleep patterns frequently are interrupted because
of thesemanifestations.Walking or exercisemay be needed
to provide the comfort needed to return to sleep. The most
common extraskeletal involvement is acute anterior uve-
itis (iritis), which occurs in approximately 30% of persons
sometime in the course of their disease. Systemic features
of weight loss, fever, and fatigue may be apparent.
Osteoporosis may occur, especially in the spine, which
contributes to the risk of spinal fracture. Loss of motion
in the spinal column is characteristic of the disease (see
Fig. 44-8). Loss of lumbar lordosis occurs as the disease
progresses, and this is followed by kyphosis of the
thoracic spine and extension of the neck. A spine fused
in the flexed position is the end result of severe ankylos-
ing spondylitis. A kyphotic spine makes it difficult for
the patient to look ahead and to maintain balance while
walking. The image is one of a person bent over look-
ing at the floor and unable to straighten up. X-ray films
show a rigid, bamboolike spine. The heart and lungs are
constricted in the chest cavity. Abnormal weight bearing
can lead to degeneration and destruction of the hip joint,
necessitating joint replacement procedures. Peripheral
arthritis is more common in the hips and shoulders.
Diagnosis andTreatment.
The diagnosis of ankylosing
spondylitis is based on history, physical examination,
and x-ray examination.
51,53
The history and physical
examination should include measures of physical func-
tion, pain, spinal mobility, duration of morning stiff-
ness, involvement of peripheral joints and entheses,
and fatigue. Laboratory findings frequently include an
Spinal column fused
by ossification of disks,
joints, and ligaments
Enthesitis
(inflammation
and tendency
for fibrosis and
calcification at
sites of muscle
insertion) at
shoulders,
hips,
knees,
and heels
Eyes:
Uveitis
Enthesitis of
costovertebral
and costosternal
junctions with
flexion contraction
of the diaphragm
Kyphosis and
extension
of the neck
FIGURE 44-8.
Clinical manifestations of ankylosing
spondylitis.
