Diseases

Introduction

Ankylosing spondylitis is an inflammatory disease involving the spine, sacroiliac joints and the hip joints. It affects patients in their second and third decades of life. Men and women are affected equally but, typically, men have a more severe disease expression.

Cause

Ankylosing spondylitis is genetically inherited. Between 88 and 96% of patients with ankylosing spondylitis are born with the HLA-B27 gene. The HLA-B27 gene appears only to increase the tendency of developing ankylosing spondylitis, while some additional factor(s), perhaps environmental, are necessary for the disease to appear or become expressed. The disease process involves inflammation of the joints in the spine, sacroiliac joints and other peripheral joints. This inflammatory processes cause cartilage destruction and bone erosion. Usually the earliest changes occur in the sacroiliac joints. In addition, the inflammation typically affects the tendon and ligaments at the bony insertions. In the spine, the inflammation occurs at the insertion of the annulus fibrosus of the intervertebral disc.

Symptoms

Symptoms are usually present for one to three years before diagnosis. These include low back pain and stiffness, which are worse in the morning and get better with activity. Fifteen to 25% of patients have peripheral joint arthritis with knee and hip pain and progressive stiffness of the involved joints.

Diagnosis

Physical examination

Physical examination of the spine reveals limitation of the lumbar motion. Decreased chest expansion and sacroiliac stress maneuver (Patrick’s test) are positive. In more severe cases, the spine becomes rigid and with kyphosis. There may be compensatory hip flexion contractures as well. Besides the skeletal manifestations, some patients may have aortic insufficiency, cardiac conduction defects, uveitis and pulmonary fibrosis.

Radiological examination

Radiograph of the sacroiliac joints reveals reactive bone growth and subsequent fusion of the joints. These changes usually start at the lower portion of iliac side first, and the involvement is usually bilaterally and symmetrically. Typically, the spine appears “bamboo” like due to syndesmophyte (new bone) formation from the margins of the vertebral bodies, shaping the vertebrae to “squaring of the vertebral bodies”. Other radiological features include osteoporosis and disc and apophyseal joint narrowing.

Occasionally, patients with ankylosing spondylitis may experience an occult fracture complication in the stiff spine with or without history of minor trauma. Plain radiographs can be difficult to interpret in such situations and MRI scans or high-resolution CT scans are more reliable in revealing these occult fractures.

Non-surgical treatment

Non-surgical treatments of ankylosing spondylitis include non-steroidal anti-inflammatory medications for pain control. New disease modifying drugs, though expensive, are available from the rheumatologist. Physiotherapy including breathing exercises, isometric exercises of the muscles and range of motion exercises can help to prevent progressive stiffness and improve function.

Surgical treatment

Surgical treatment is indicated in patients with:
1. genuine kyphotic deformity of the spine associated with pain and neurological compromise
2. loss of horizontal gaze, and
3. unstable vertebral fractures. Surgery includes corrective spinal osteotomies and fusion with spinal instrumentation

Surgery includes corrective spinal osteotomies and fusion with spinal instrumentation.

The other type of surgery commonly performed in patients with ankylosing spondylitis is total hip replacement. This is common in patients with fused or stiff hips, which affect the ambulation of the patient.

Dr. SUN, Lun-kit