ANKYLOSING SPONDYLITIS

Essentials of Diagnosis

1. Inflammatory back pain in young adults.

2. Radiographic demonstration of sacroiliitis.

3. Reductions in spinal mobility, particularly lumbar flexion.

4. Association with anterior uveitis.5. Increased relative risk conferred by

inheritance of HLA-B27.6. Positive family history.

Criteria for diagnosing ankylosing spondylitis(Rome, 1961)

Clinical criteria 1. Low back pain and stiffness for more than 3 months which is not relieved by rest 2. Pain and stiffness in the thoracic region 3. LIMITED MOTION IN THE LUMBAR SPINE 4. LIMITED CHEST EXPANSION 5. History or evidence of iritis or its sequelae

Radiological criterion 6. X ray showing bilateral sacroiliac changes characteristic

of ankylosing spondylitis (this would exclude bilateral osteoarthrosis of the sacroiliac joints)

Clinical criteria for ankylosing spondylitis(New York, 1966) (A) Diagnosis 1. LIMITATION OF MOTION OF THE LUMBAR SPINE in all THREE PLANES-anterior

flexion,lateral flexion, and extension 2. History or the presence of PAIN at the dorso-

lumbar junction or in the lumbar spine 3. LIMITATION OF CHEST EXPANSION to 1 in. (2 5 cm.) or less, measured at the level of the

fourth intercostal space

(B) GradingDEFINITE AS:1. Grade 3-4 bilateral sacroiliitis with at least one clinicalcriterion.2. Grade 3-4 unilateral or Grade 2 bilateral sacroiliitiswith Clinical criterion I (limitation of back movementin all three planes) or with both Clinical criteria 2 and3(back pain and limitation of chest expansion)PROBABLE AS:Grade 3-4 bilateral sacroiliitis with no clinicalcriteria

SYMPTOMS AND SIGNS

The typical presenting symptom in ankylosing spondylitis is the insidious onset of inflammatory low back pain due to sacroiliitis.

The pain is dull and located in the lower lumbar regions.

Some describe a deep alternating buttock pain.

The pain worsens with rest, improves with activity, and is accompanied by morning stiffness that lasts 30 minutes or longer.

Patients often describe awakening from sleep and pacing in order to relieve nocturnal pain—a rare complaint in patients with mechanical back pain.

Involvement of the spine (spondylitis) is the major source of morbidity.

Ankylosing spondylitis can involve the lumbar, thoracic, and cervical spine.

Over time the accumulation of pathologic changes can lead to loss of spinal mobility, particularly of the lumbar spine.

Clinical tools for the measurement of spinal mobility Schober test

1. Two marks are made on the patient's back: one at the level of the sacral dimples (approximately at the fifth lumbar spinous process) and the other 10 cm above.

2. The patient then bends forward as far as possible (ie, attempts to touch toes with knees extended), and the distance between the two marks is again measured.

3. In normal individuals, the overlying skin will stretch to 15 cm; values less than this can be indicative of reduced lumbar mobility.

The modified Schober test 1. In this test marks are made 5 cm below

and 10 cm above the sacral dimples; 2. The distance between these marks

should increase from 15 cm to at least 20 cm with lumbar flexion.

3. Reductions in lumbar lateral bending and rotation are also commonly observed.

Lateral lumbar flexion.

1. The patient bends

laterally to push the middle finger down the rule without flexing forward or bending the knees.

2. The difference between start and endpoint is recorded and the mean calculated; normal: >10 cm.

Cervical rotation.

The mean of the

left and right cervical rotation is recorded; normal:>70 degrees.

Occiput to wall distance.

Patient stands, with heels and buttocks against the wall; the head is placed back asfar as possible, keeping the chin horizontal; normal = 0.

Tragus to wall distance.

1. Patient stands, with heels and buttocks against the wall.

2. The head is placed back as far as possible, keeping the chin horizontal;.

3. Normal: <15 cm.

Intermalleolar distance.

Patient stands with legs separated as far as possible.

The distance between the medial malleoli is measured.

Normal: >100 cm.

With advancing disease, as the spine fuses in flexion.

This leads to loss of lumbar lordosis, exaggeration of thoracic kyphosis, an inability to extend the neck, and compensatory hip flexion deformities .

The extent of spondylitis varies greatly, from minimal to complete fusion of the cervical, thoracic, and lumbar spine.

Involvement of the costovertebral and costochondral joints commonly leads to impaired chest expansion (<5 cm difference between full inspiration and full expiration when measured at the fourth intercostal space)

Occasionally this produces pain with deep breathing, coughing, or sneezing

Peripheral Joint Manifestations

Monarticular or asymmetric oligoarticular.

Develops in approximately one-third of patients.

Most often affects large joints of the lower extremities.

Hip disease develops in approximately 50% of patients and is a major source of morbidity.

Anteroposterior view of the pelvis in a patient with long-standingAS. There is generalized osteoporosis, and there is also ankylosis of thesacroiliac joints, pubic symphysis, and both hips. A normal rounded contour ofthe femoral head is seen through the bone ankylosis .

Enthesitis

Involvement of insertion sites around the pelvis (the ischial tuberosities, iliac crests, and greater trochanters) is common and appears on radiographs as bony "whiskering" at these sites of attachment.

Achilles tendinitis and enthesitis at the site of the insertion of the plantar fascia onto the calcaneus can cause unilateral or bilateral heel pain, although not as often as in reactive arthritis.

Ocular

The most common extra-articular manifestation of ankylosing spondylitis is acute anterior uveitis.

It is heralded by the acute or subacute onset of unilateral eye pain, photophobia, blurred vision, and increased lacrimation.

Anterior uveitis can precede the onset of ankylosing spondylitis by several years,.

Anterior uveitis is strongly associated with HLA-B27.

Osteoporosis

Spinal immobility and persistent inflammation to contribute to the increased prevalence of osteoporosis in ankylosing spondylitis and other spondyloarthropathies.

The formation of syndesmophytes in these diseases creates a unique problem in evaluation of bone mineral density.

For example, in an ankylosed spine with paravertebral calcification, anteroposterior measurement of bone density by dual energy x-ray absorptiometry can lead to spuriously increased values for bone mineral density of the spine.

Other Organs

Ascending aortitis, aortic regurgitation, conduction abnormalities, and myocardial disease--- 10% of patients with ankylosing spondylitis.

Secondary amyloidosis. Retroperitoneal fibrosis. Apical fibrobullous disease --

radiographically resembles reactivation of tuberculosis

LABORATORY FINDINGSRoutine Studies

Mild, normocytic, normochromic anemia, reflective of chronic disease.

About half of patients with active disease will have elevations of the erythrocyte sedimentation rate or C-reactive protein.

No association with rheumatoid factor, antibodies to cyclic citrullinated peptides, or antinuclear antibodies.

HLA-B27

Interpretation of the HLA-B27 test.1. Inheritance of HLA-B27 is not sufficient

to produce ankylosing spondylitis.2. Inheritance of HLA-B27 is not absolutely

essential for the development of ankylosing spondylitis.

3. Ethnicity influences the prevalence of HLA-B27 in disease populations.

HLA-B27 is present in 8% of the general white population, and 90% of whites with ankylosing spondylitis are HLA-B27–positive.

In contrast, HLA-B27 is present in 2% of the African American population and only 50% of African Americans with ankylosing spondylitis are HLA-B27–positive

IMAGING STUDIES

Sacroiliac Joints The most distinctive finding is inflammation

of both sacroiliac joints. A standard anteroposterior radiograph of the

pelvis is commonly used to evaluate these S-shaped joints.

A superior image is achieved with the Ferguson view, in which the radiograph is taken at a 15-degree angle to the prone pelvis.

Anteroposterior view of sacroiliac joint. The white cortical line is intact on the sacral side. It is ill defined on the iliac side (arrows).

Anteroposterior Ferguson view of the sacroiliac joints in a patient with AS.

The area of the sacroiliac joint inferior to the arrows is imaged by the Ferguson view and not by an anteroposterior view.

Note the bilateral, symmetric involvement with erosions and eburnation.

Sacroiliac disease.

Routine anteroposterior view shows equivocal

changes in the left sacroiliac joint.

Ferguson view demonstrates clear-cut

bilateral sacroiliitis.

The first radiographic finding is the appearance of iliac erosions.

With time erosions become more prominent and produce "pseudowidening" of the sacroiliac joint.

Progressive inflammation leads to fusion, and the end result can be complete obliteration of the sacroiliac joint by bone and fibrous tissue.

Anteroposterior Ferguson view of the sacroiliac joints in a patientwith AS. There is bilateral, symmetric involvement with succinct erosions(arrows).

Anteroposterior view of the sacroiliac joints in long-standing ASshows total ankylosis. Ossification of the ligaments connecting the posteriorsuperior aspect of the sacroiliac joints is evident (arrows).

The pattern of sacroiliac joint involvement is bilaterally symmetric in ankylosing spondylitis and enteropathic arthritis, in contrast to the unilateral changes observed in early psoriatic and reactive arthritis.

The method that is most sensitive and specific for the diagnosis of sacroiliitis is Magnetic Resonance Imaging with gadolinium- DPTA or fat suppression.

In clinical practice, a reasonable initial evaluation of patients with symptoms of inflammatory back pain is to obtain a plain radiograph of the pelvis.

If this study fails to demonstrate sacroiliitis, then magnetic resonance imaging should be considered, particularly if the patient is HLA-B27–positive.

MR image of the sacroiliac joints in a patient with undifferentiatedspondyloarthropathy. Axial T1-weighted image with fat suppression afterintravenous administration of Gd-DTPA demonstrates increased signal intensityin the subchondral bone marrow within the iliac and sacral sides of the rightjoint and early erosions of the left joint .

Spine

Romanus lesions : Radiographic appearance of vertebral "shiny corners.“

These are a reaction to inflammation at the site where the annulus fibrosus of the disks inserts onto the vertebral bodies.

With progressive erosions and formation of new periosteal bone, the lumbar vertebral bodies become "squared off" in the lateral view.

Lateral view of the lumbosacral spine showing shiny corners(arrowheads), squaring of the vertebral bodies, and early syndesmophyteformation (arrows) in a patient with AS.

Syndesmophytes

Bony bridges between vertebral bodies due to gradual ossification of the edges of the annulus fibrosus.

The vertical orientation of syndesmophytes and preservation of the disk space distinguish these from osteophytes associated with degenerative disease of the spine.

Lateral view of the lumbosacral spine showing syndesmophytes ofAS, giving it a bamboo appearance

Ankylosing spondylitis and enteropathic arthritis exhibit symmetric delicate-appearing syndesmophytes that are marginal,( completely vertical in their alignment) and arise from the margins of the vertebral body.

Psoriatic arthritis and Reactive arthritis typically have more bulky, asymmetric bony growths that tend to initially protrude laterally before progressing vertically (nonmarginal syndesmophytes).

Peripheral Joints

Radiographic changes in the peripheral joints mainly result from disease of the synovium or entheses.

Hip involvement can produce symmetric narrowing of the joint space.

Enthesitis can result in a faint periosteal reaction at bony prominences, such as the greater trochanters, calcaneus, and malleoli.

Differential Diagnosis of the Spondyloarthropathies

Sacroiliitis Hyperparathyroidism

Familial Mediterranean fever

Whipple disease

Paget disease

Paraplegia

Behçet disease

Tuberculosis

Brucellosis

Pyogenic sacroiliitis

Malignancy

Retinoid treatment

SAPHO syndrome

Vertebral hyperostosis

DISH

Ochronosis

SAPHO syndrome

Retinoid treatment

Enthesopathy

Gout

Disseminated gonococcal infection

SAPHO syndrome

Retinoid treatment

BCG-induced

Other changes

Degenerative joint disease

Osteitis condensans

Chondrocalcinosis

Gout