Ankylosing Spondylitis: Clinical Presentation, Pathology And Management As A Disease Of Bones And Joint
A General Overview
This is an inflammatory arthropathy predominantly involving the axial skeleton and in the advanced stages, the entire vertebral column undergoes bony ankylosis. This disease entity belongs to the group of seronegative spondyloarthritides (SSA).
Prevalence and epidemiology: This disease is rare, compared to rheumatoid arthritis. It is not an uncommon disease in developing nations like Nigerian and India. Male to female ration in india, especially is 7:3.
Genetic Factors: The histocompatibility antigen type HLA B27 is positive in over 90% of patient and 53% of their first degree relatives.
Environmental factors: Genitourinary infections like chronic prostatitis are associated with this disease. The presence of the HLA B27 antigen predispose such individuals to develop arthritis in response to several environmental factors. Nature of these agents and the mode of interaction with the HLA antigen are still conjectural.
Pathology: The sacro-iliac joints and vertebral joints are maximally affected, but the manubrisoternal joints, symphysis pubis, costovertebral and sternocostal joints, shoulders, hips and rarely the joints of the hands and feet may also be affected. The joints show mild synovitis. Periarticular fibrous tissue, ligaments and articular cartilage also show inflammation. Extra-articular lesions develop in various ligaments, tenoperiosteal junctions, the ascending aorta, uveal tract and the upper lobes of the lungs. Ankylosis develops in the joints on account of the tendency for calcification and ossification. Calcification and ossification of the annulus fibrosus and proliferative bony outgrowths from the vertebral borders result in ankylosis of the spine. The spinal column becomes a rigid pillar giving the radiological appearance of “bamboo spine”.
Ankylosing Spondylitis As Seen On Radiographs
The clinical severity ranges from the fully developed crippling disorder to the partial forms (forms frustes). The disease is more common in the second, third, and fourth decases. Bouts of low backache, felt mostly in the morning and aggravated by periods of rest are the early manifestations. Later, the pain becomes constant. At this stage, the obliteration of lumbar lordosis and generalized limitation of the movement of the lumbar spine due to muscular spasm are detectable. Later, ankylosis of spinal joints (poker back) occurs. The whole spine becomes a single rigid column. A simple but reliable test to diagnosie ankylosing spondylitis is the modified shober test. A 10 cm long line, is drawn perdendicularly up from the midpoint of a line joining the posterior superior iliac spines. In normal persons, this line stretches to 16 to 22cm when the patient fully bends forwards. In established ankylosing spondylitis, this line does not stretch more than 1 or 2 cm.
Tenderness over the sacroiliac joints is elicitable by deep palpation. Pain from the sacroiliac joints is elicited by the pump handle test, the pelvic compression test and hyperextension test.
Other joints may be involved in 50% of cases, the commonest being the root joints, viz, hips and shoulders and hence the term “rhizometric spondylitis”. It is rare to get affection of the peripheral small joints. When it occurs, it is asymmetrical and milder compared to rheumatoid arthritis. Later on they also may be ankylosed. The patient with advanced ankylosing spondylitis develops forward craning of the neck, high dosal kyphosis, rounding of the shoulders, obliteration of the normal lumbar lordosis, wasting of the glutei, flattening of the chest, and ballooning of the abdomen. Forward vision is impaired due to stooping posture.
Diagnosing Ankylosing Spondylitis
These include unilateral iritis (20%), aortic incompetence, heart block, pericarditis and fibrosis of the upper lobes of the lung.
Complication: Fracture dislocations of the spine and other bones and secondary amyloidosis comprise the complications. Though in the majority of cases, the picture of ankylosing spondylitis is typical, less commonly, the presentation may be atypical. These are; (1) Isolated sacroilitis, (2)asymmetrical peripheral polyarthritis, or (3) Uveitis.
Laboratory data: The ESR is elevated in the early phases of inflammation, but it returns to normal levels in the later stage when ankylosis is complete.
Radiology: Early abnormality is in the sacroiliac joints which show an appearance of widening (Pseudowidening) and erosions. As the disease progresses, the adjacent zones become sclerosed and the joint space is obliterated by bony fusion.
The vertebrae appear square due to a combination of osteitis of the borders and filling up of the anterior concavity. The fully developed stage gives the typical picture of “bamboo spine”. Ossification of teno-periosteal junctions may develop.
Diagnosis: Clinical diagnosis has to be confirmed by radiology and the diagnosis is strengthened by the demonstration of HLA B27.
Differential diagnosis: This includes osteo-arthritis, cervical spondylosis, other causes of sacroiliac arthritis and endemic fluorosis.
The treatment is aimed at improving spinal mobility, preventing ankylosing and giving symptomatic relief. The modalities of treatment include physical measures and appliances, medications, irradiation or surgery.
Physical measures and appliances: Regular spinal exercises help in correcting postural abnormalities and strengthen the spinal ligaments and paraspinal muscles. Prolonged immobility tends to accelerate ankylosis and this should be avoided. Spinal braces help in correcting postural defects partly. Prismatic spectacles enable the patient to see objects in front.
Drugs: Commonly used drugs are indomethacin, aspirin and the nonsteroidal anti-inflammatory agents. Phenylbutazone is very effective in relieving symptoms but it has to be used cautiously due to the risk of agranulocytosis. Corticosteroids are not widely used except for limited indications.
Irradiation: Doses of 600 to 700 rads given in one or two exposures over the spine gives prompty relief for considerable periods. The effect is palliative. Irradiation is employed only sparingly due to the potential risk of bone marrow damage and induction of leukemias in later life.
Surgery: Permanent deformities of the spine, hip and other joints can be corrected by orthopedic procedures. The disability has been considerably reduced by total hip replacement which has revolutionized the treatment of ankylosing spondylitis.
© 2014 Funom Theophilus Makama