Clinical Practice Guideline
for
ANKYLOSING SPONDYLITIS
Developed for the
Aerospace
Medical Association
by their constituent organization
American
Society of Aerospace Medicine Specialists
Overview:
Ankylosing spondylitis (AS), the most common of the spondyloarthritides, is a chronic inflammatory disease principally
involving the hips and axial skeleton. The
name for the disorder is derived from the Greek root "ankylos", which
means bent or crooked and "spondylos", which refers to a
vertebra. The term "ankylosis"
therefore refers to a fibrous or bony bridging of joints. In the spine this includes bridging of one or
more intervertebral discs. AS typically has an insidious onset, can have
extra-articular manifestations,
and is diagnosed based on clinical suspicion supported by imaging techniques
and associated human leukocyte antigen HLA-B27.
It also must be differentiated from other types of seronegative
spondyloarthropathies, systemic inflammatory arthritis, as well as mechanical
and degenerative causes of back pain.
AS commonly affects young adults as evidenced by the peak age of onset being
20 to 30 years. The male to female ratio
is approximately 2 to 3:1. Among Caucasians, the estimated prevalence rate of AS, as defined by
the modified New York criteria, ranges from 68 per 100,000 population older
than 20 years in the Netherlands, to 197 per 100,000 in the United States. In the general population, AS is likely to develop in
about 1% to 2% of HLA-B27–positive adults who have a disease-associated B27
subtype, although there may be regional or geographic differences. For example, in northern Norway, AS may
develop in 6.7% of HLA-B27–positive people.
The disease is much more common among HLA-B27–positive, first-degree
relatives. Of HLA-B27–positive AS
patients, roughly 10% to 30% of them have signs or symptoms of AS. The prevalence of AS in working adults with
back pain of greater than three weeks duration was 4.6% in one study. Thus, if the patient has at least one first
degree relative with AS and given that the patient is positive for HLA-B27, a
presumptive diagnosis of AS is reasonable.
AS
can also present with the nonspecific symptoms of low-grade fever, fatigue and
weight loss. Non-skeletal involvement frequently occurs, including acute
anterior uveitis; neurologic symptoms resulting from fractured spine,
atlantoaxial subluxation, cauda equina syndrome and costovertebral rigidity;
aortic regurgitation; IgA nephropathy and secondary amyloidosis; ileal and
colonic mucosal ulcerations; and osteopenia.
Diagnosis
and Treatment:
Because
AS has an insidious onset, the diagnosis is based on a high index of clinical
suspicion and supported with a judicious use of imaging, laboratory testing
along with a therapeutic trial of NSAIDs.
Signs and symptoms suggestive of inflammatory back pain include: onset
prior to age 40, insidious onset, symptoms persisting longer than three months,
morning stiffness, and improvement with exercise. The presence of four of the five above has a
sensitivity and specificity of up to 75 percent.
Range
of Motion (ROM) Measurement:
Assessment
of ROM of the lumbar spine is a key clinical finding. The modified Schober test is one accepted
method to assess lumbar spine ROM by measuring the forward flexion of the spine
in a patient with suspected AS. The test
is performed with the patient standing erect; a mark is made over the spinous
process of the 5th lumbar vertebra or the imaginary line joining the
posterior superior iliac spine and another mark is made 10 centimeters above
this mark in the midline. In a patient
with no lumbar spine motility abnormalities, the measured distance between the
two points should increase by 5 cm when the patient bends forward to touch his
toes while keeping the knees locked. The
severity of cervical flexion deformity can be assessed using the Flesche
test. While the patient is standing
erect, the heels and buttock are placed against the wall. The patient is
instructed to extend his neck in order to touch the wall. The distance between
the occiput and the wall is a measure of the degree of cervical flexion
deformity. In addition, assessment of
chest wall expansion, loss of cervical lordosis, sacroiliac joint tenderness,
hip and peripheral joint involvement are important indicators of range of
motion abnormalities.
Serological
Testing:
Testing
for C-reactive protein and HLA-B27 can help to support the clinical picture,
but caution is advised as these tests should not be used as screening tests,
that is, the value of either positive or negative results is only realized when
the test is applied in the appropriate clinical setting. A history of chronic, inflammatory low back
stiffness, elevated ESR, positive C-reactive protein with a positive HLA-B27 in
an otherwise healthy young male with a familial history of inflammatory back
stiffness supports a diagnosis of AS.
The finding of a negative HLA-B27 in the same clinical setting reduces
the likelihood of AS to 1 in 20 (5%).
Likewise, the indiscriminate use of additional serologic assays (i.e.
“the rheumatology lab panel”), in search of alternative diagnoses, is further
discouraged. Serologic studies must be
carefully chosen based on the constellation of the presenting history and
physical exam features.
Imaging
Studies:
A
CT of the sacroiliac (SI) joints will visualize bony changes better than plain
radiographs; it will not detect early acute inflammatory changes in the bone
marrow and it exposes the patient to a relatively high dose of gonadal
radiation. Ultrasound is not currently
recommended for the evaluation of AS.
Plain films can be used to follow clinical progression. Though AS usually manifests as a spinal
disease, chronic changes in peripheral joints can occur in about 25 percent of
patients. In the presence of chronic,
inflammatory back symptoms and a physical exam consistent with the same,
screening plain radiographs of the SI joints and lumbosacral spine are
recommended.
Treatment:
The
use of NSAIDs and physical therapy are the mainstays of treatment in AS. This approach is both therapeutic and
diagnostic. The goal of treatment is to
provide symptomatic relief, restore function, prevent joint damage and spinal
fusion, minimize extra-spinal and extra-articular disease, and prevent complications
of spinal disease. The majority of AS
patients using NSAIDs experience relief of symptoms. Regardless of the NSAID used, the maximum
dose is usually required, taken daily for at least two weeks, and the NSAID
must be on the list of approved medications for military aviators. Anti-TNF-alpha agents can also be used in
patients with a firm clinical diagnosis of AS with moderate to severe spinal
disease who have not responded to NSAIDs.
In advanced cases surgery may be required such as total hip replacement
and/or spinal or cervical fusion.
Smoking cessation is recommended due to the detrimental effect COPD can
have on the restrictive lung disease secondary to limited costovertebral joint
motility.
Aeromedical Concerns: In aviators with AS,
cramped cockpit conditions for prolonged periods may be poorly tolerated. There may be functional limitations in all
aircraft, especially in high performance aircraft and flying in typical
cockpits may exacerbate eventual disability.
Typical AS symptoms are incompatible with ejection and special duty that
would require parachute qualification or other skill sets that may subject a
service member to impact forces. The
cervical and lumbosacral limitations of AS may also interfere with emergency
ground egress and can limit vision due to restricted neck motion. Note: the FAA does not take emergency egress
as a factor in the consideration for medical certification. Concomitant uveitis/iritis occurs in up to
25% of cases. The development of most of
the extra-articular manifestations in AS are disqualifying in the military
services, and chronic treatment with NSAIDs and tumor necrosis factor alpha
antagonists are incompatible with flying duties in the military services.
Medical
Work-up: Documentation needs to include a detailed history
to include onset of symptoms, time course, joints and/or extra-articular
involvement, extra-articular manifestations, medications used and any
side-effects and the current activity level.
The exam needs to focus on the affected joints, involved extra-articular
tissues, the eyes, kidneys and heart.
Lab testing needs to include a CBC, comprehensive metabolic panel,
HLA-B27, serology, urinalysis, ESR, and C-reactive protein. Radiographs of involved levels of the spine
to include SI joints (Ferguson’s views) are also required. In addition, an echocardiogram and cardiology
consult are required if there is involvement of cardiac valves. All cases will should obtain a rheumatology
and ophthalmology report. If the aviator
is military, a medical evaluation board report will be necessary.
Aeromedical
Disposition:
Air Force: AS
is disqualifying for Flying Classes I, II, and III IAW AFI 48-123, but a waiver
is possible with documentation of treatment and resolution of symptoms.
Army: Ankylosing spondylitis, as with other
inflammatory spondylopathies, is disqualifying for Army aviation service. It is discussed primarily in its own
Aeromedical Policy Letter but is mentioned in several other connective tissue
policy letters. Waiver, though not
usually granted to applicants, will be considered on a case-by case basis for
applicants and aircrew for early stage mild or inactive disease who have
minimal symptoms, require minimal medications for symptom control, have had no
recurrent symptoms or extra-spinal manifestations, who continue to have normal
spinal mobility, and whose occupational environmental safety risk remains
acceptable. Disqualification or
(discontinuation of waiver) will often be recommended for individuals whose
disease involves any of the following: 1) extra-spinal manifestations; 2) use
of Class IV medications; 3) symptom or performance issues (such as chronic
pain, anxiety, frequent work absences or profiles, issues of potential impact
on aviation work performance/safety; or 4) failure to meet retention standards,
need for Permanent 3 or 4 profile, or inability to take/perform at least one
aerobic AFPT event.
Navy: An established diagnosis with symptoms is CD. Waiver is
possible in early cases with normal mobility and no complications
Civilian:
See below.
Waiver
Experience:
Air
Force: Review
of AIMWTS revealed a total 13 cases of AS submitted for consideration of a
waiver. There were no 0 FC I/IA cases,
seven FC II and six FC III cases. Of the
13 cases, eight were approved for a waiver.
Five of the cases were disqualified for AS or AS with complications of
AS. In the FC II category, three were
disqualified and in the FC III category, two were disqualified.
Army: Since 1990 there have
been 123,259 aviators of all types, including applicants enrolled in the
Aeromedical Epidemiological Data Repository.
Among them there have been 6 cases of ankylosing spondylitis, 5 in rated
aviators and one in an applicant. All
were granted waivers except for one rated aviator.
Navy: Not
available at this time.
Civilian:
This condition is acceptable in the civilian sector. See above for consideration concerning
medical treatment. The airman needs to
provide statements from the treating physician as to whether there are extra-articular
manifestations. Since the FAA mainly
concerns itself with sudden incapacitation in the cockpit, making sure that the
airman can remain seated for long periods without experiencing incapacitating
pain and extra-articular manifestations should be considered in granting an
authorization. Currently the FAA does not maintain statistics on the number of
airmen currently certificated with this condition.
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MD and David T. Clinical manifestations
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MD and David T. Diagnosis and
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Prepared
by Drs. Bradford J. Williams and Dan Van Syoc
11/10/10