Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

Featured on Channel NewsAsia

Ankylosing Spondylitis

Basics
Description
  • AS is a seronegative spondyloarthritis.
  • It is an inflammatory oligoarthritis of the spine and peripheral joints.
  • Primarily affects the spine, especially the SI joint, as well as the hips and shoulders
  • May affect any spinal level
  • Affects synovial and fibrous joints, causing chronic synovitis with joint, destruction, erosions, and sclerosis, which eventually leads to joint fibrosis and ankylosis
  • Ocular, cardiac, and mucocutaneous manifestations also may be seen.
Epidemiology
  • Primarily affects young males in the 3rd and 4th decades of life.
  • Manifestations after age 40 are rare.
  • Cause is unknown.
  • Associated with the HLA genes of the major histocompatibility complex, in particular HLA-B27.
Incidence
  • The incidence in North America is 0.3% .
  • In patients with the HLA-B27 gene, the incidence increases 100-fold.
  • In 1st-degree relatives of patients with AS, the incidence increases 20-fold.
Prevalence
It should be noted that, although a link exists between AS and HLA-B27, <5% of patients with the HLA-B27 gene develop AS.
 
Risk Factors
  • HLA-B27 gene
  • Positive family history
Genetics
  • Strong positive family history
  • Concordance rate in identical twins is 63% compared with a 23% concordance in fraternal twins .
  • Associated with several genes of the major histocompatibility complex, including HLA-B27, HLA-DRB1, and HLA-B60
  • Other genes implicated include CYP2D6 and IL-1B.
Pathophysiology
  • Inflammatory arthropathy, affecting the SI joint 100% of the time .
  • Affects both synovial and fibrous joints of the spine and the periphery
  • Inflammation of the tendons and ligaments also are seen.
  • The inflammatory process leads to joint destruction and ankylosis.
  • Onset usually is insidious, with flares and remissions.
  • The disease affects both males and females but is more severe in males.
  • Severity also is proportional to age at onset, with early onset showing a more severe course.
Etiology
  • Exact cause is unknown.
  • May be associated with viral or bacterial infection
  • Klebsiella has been implicated, but studies to investigate the bacterial relationship with AS have been inconclusive .
  • Some evidence suggests a link between AS and inflammation of the small intestine.
Associated Conditions
  • Plantar fasciitis
  • Achilles tendinitis
  • Inflammatory uveitis
  • Aortic insufficiency, cardiomegaly, and conduction defects
Diagnosis
Signs and Symptoms
  • The diagnosis of AS is made clinically and radiographically, and is suggested by the following signs and symptoms, which should be present for at least 3 months:
    • Pain relieved by exercise, and not made better with rest
    • Morning stiffness
    • Limited spine motion
    • Fatigue
    • Decreased chest expansion
    • Weight loss
    • Chest pain secondary to costosternal involvement
    • Apical fibrosis of the lungs
    • Kyphosis and/or flattening of lumbar spine
    • Upper extremities are rarely involved.
History
  • Insidious onset of discomfort of the lumbosacral spine, buttocks, and hips.
  • Onset age <40 years
  • Persistence of symptoms for >3 months
  • Morning stiffness
  • Improvement of pain and stiffness with exercise
Physical Exam
  • Early in the disease, patients may be asymptomatic.
  • Careful neuromuscular, pulmonary, and optic examinations are essential.
  • Careful examination of the lumbar spine will show loss of motion in flexion and extension.
  • Pain with palpation of the SI joint
Tests
Lab
  • HLA-B27 gene
  • The ESR is elevated in 80% .
  • Antinuclear antibodies and rheumatoid factor are not useful.
Imaging
  • Radiography:
    • Radiographs may be negative in the early stages of AS.
    • Radiographic changes of the SI joint are pathognomonic for AS.
    • Radiographic findings usually are symmetric.
    • Early signs are erosions and sclerosis of the SI joint, which lead to a blurring of the joint margins and pseudo widening of the SI joint.
    • Late changes are calcification with osseous bridging of the SI joint.
    • Bamboo spine is seen in the lumbar spine as a result of inflammation of the annulus fibrosis, with erosion of the corners of the vertebral bodies and subsequent osteophyte bridging of the adjacent bodies.
    • AP, lateral, and oblique radiographs should be studied carefully because fracture lines may be difficult to detect.
  • CT scans with 3D reconstructions are sensitive for detecting fractures.
  • MRI can be used to detect epidural hematomas.
Differential Diagnosis
  • The differential diagnosis should include any of the seronegative arthropathies:
    • Reactive arthritis (formerly known as Reiter syndrome): Nongonococcal urethritis and arthritis
    • Psoriatic arthritis
    • Crohn disease
    • Ulcerative colitis
    • Infection of the SI joint
    • Osteoarthritis
    • Rheumatoid arthritis
    • Herniated nucleus pulposus
Treatment
Initial Stabilization
  • The mainstay of treatment is exercise.
  • Back exercise and flexibility training reduce pain and improve function.
  • NSAIDs
General Measures

In general, recreational activities and the pursuit of a healthy, active lifestyle should be encouraged.
 
Special Therapy
Physical Therapy
  • Hyperextension exercises are helpful in preventing kyphosis.
  • Flexibility training provides pain relief and improves quality of life.
Medication (Drugs)
First Line
  • NSAIDs
  • The selection is empiric: No specific drugs, including the COX-2 inhibitors, have shown superiority.
Second Line
  • Many other medications have been used:
    • Corticosteroids
    • Sulfasalazine
    • Antibiotics
    • Pamidronate
    • Thalidomide
    • TNF-α blockers
Surgery
  • The role of surgery for patients with AS is primarily to treat the complications that develop as a result of the disease.
    • Most commonly, total hip arthroplasty
    • Stabilization for vertebral fractures
    • Spinal osteotomy for the correction of the kyphotic deformity (seen in late-stage AS).
Follow-up
Prognosis
  • Patients with early-onset disease and inflammation of peripheral joints have a relatively poor prognosis.
  • No cure exists for this disorder, but with aggressive preventive measures, much of the disability associated with it can be avoided.
Complications
  • Spinal fractures may occur with minimal trauma because the ossified spine is brittle and is therefore overall less elastic than the normal spine.
    • Epidural hematomas may occur with a cervical spine fracture.
      • If unrecognized, the hematoma may compress the spinal cord and cause irreversible paralysis.
  • Spinal fractures should be braced or internally fixed urgently to reduce risk of subsequent paralysis.
  • Uveitis develops in 25% of patients and may require topical steroids.
Patient Monitoring
  • Patients should be seen on a routine basis (every 6 months) to monitor posture, reinforce the importance of exercises, and adjust analgesics.
  • Patients should be monitored for uveitis and the development of cardiac and pulmonary problems.

Miscellaneous
Codes
ICD9-CM
720.0 AS
 
Activity
  • Activity should not be prohibited, but patients should be told about the increased risk and danger of spine fracture and should avoid situations placing them at risk for this injury.
  • Patients should avoid contact sports and other activities such as skydiving and bungee jumping.
Prevention
  • Patients should be discouraged from smoking.
  • Patients should be counseled about a 10–20% risk of transmitting the disease to their children.
FAQ
Q: What is the cause of AS?
A: The exact cause is unknown, but it appears that AS (much like rheumatoid arthritis) is an autoimmune inflammatory disease that affects the spine and other joints in the body.
 
Q: What are the treatment options for patients with AS?
A: Exercise is the cornerstone of treatment. Physical therapy and anti-inflammatory drugs also are used.
 
Q: If a patient with AS presents to the emergency department with neck pain after a fall and evidence of AS but no evidence of a fracture, what should be the next step?
A: Advanced imaging with MRI or CT to evaluate for a nondisplaced fracture.

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