It is a chronic progressive inflammatory disorder of unknown etiology, distinguished by the involvement of sacroiliac joints, synovial and spinal joints and the adjacent soft tissues. There may be associated involvement of peripheral joints and extra-articular structures.
It is often referred to as rheumatoid spondylitis (Bambo spine). The disease is characterized by long intermittent course with remissions and relapses. It is commonly seen in second or third decade, it being more common in men as compared to women (3:1).
Genetic factors play a role in the pathogenesis of the disease.About 90% of patients with ankylosing spondylitis are HLAB 27 positive though the risk of developing the disease in HLA B27 persons is 1-2% percent.
Clinical features
The earliest presenting feature of cases of ankylosing spondylitis is pain in the back and increasing stiffness of the spine. This is unrelieved by rest. The stiffness of the spine is more on awakening in the morning and person achieves some measure of relief by walking about. The stiffness becomes steadily worse so that the patient is hampered in daily activities.
Clinically patient may have four stages (i) Prodromal stage (ii) Early stage (iii) Fully developed stage and (iv) Terminal stage.
The prodromal stage is marked by fleeting and variable muscular pains with tender bony spots on the trunk. The mobility of vertebral column is normal and there are no radiological or abnormal laboratory findings.
In the early stage diffuse fluctuating pain becomes concentrated in the lumbar region. Radiation of pain to buttocks, pelvis, hips, heels and shoulders is marked. There is stiffness of the spine and region of sacroiliac joints is particularly sensitive to pressure. Prolonged periods of rest exacerbate the pain and many patients wake up in the early hours of morning with severe sacral pain.
Pain becomes increasingly severe at the lower border of the thorax with girdle type radiation exacerbated by sneezing and coughing. There is decline in general health. The spinal symptoms may be relatively mild and are often over shadowed by arthritic symptoms elsewhere in the body when one or more joint is involved.
Radiograph of sacroiliac joint at this stage may show changes. As the disease further spreads, inflammation spreads from socroiliac joints to the spine which progressively becomes stiff.
The thoracic spine tends to become fixed in a position of exaggerated kyphosis with compensating hyperlordosis of the cervical spine. Involvement of costo transverse joints of the thoracic spine leads to limited respiratory movements.
Pain in the sacro iliac joints may be elicited either with direct pressure or by maneuvers that stress the joints. There is increased osteoporosis of the ankylosed part of the spine due to inactivity. There is atrophy of muscles especially of the back and ossification at sites of muscle attachment.
‘With further progression of the disease, the spine becomes completely ankylosed. There is steadily increasing kyphosis of the thoracic spine with the result that patient acquires a humpbacked posture. The joints near the hip and shoulder show increasing inflammatory changes and patient becomes severely incapacitated.
Arthritis of peripheral joints is present in 30 per cent of patients and can occur at any stage of the disease. Extra articular manifestation like aortitis and carditis occur in 1 to 4% per cent of patients while anterior uveitis may antedate the onset of joint involvement.
Since spinal mobility is affected, these patients are liable to suffer from injury even from minor trauma and spinal fracture may occur in an already osteoporotic rigid spine. Cauda equina syndrome is another infrequent complication in patients with long standing disease.
Pathology
Sacroilititis is the earliest manifestation. In the spine the initial lesion is inflammation at the junction of annulus fibrosus of the disc cartilage and the margin of vertebral bone. The outer annular fibers are eroded and finally replaced by bone, forming the beginning of bony projection which grows by continued enchondral ossification which ultimately leads to Bamboo spine.
There is pronounced exaggeration of thoracic kyphosis, osteoporosis, narrowing of inter-vertebral spaces, bony ankylosis of inter-vertebral joints, ossification of costo vertebral and costo transverse joints and ossification of ligaments of spinal column.
The changes in inter-vertebral discs are both of degenerative and regenerative nature. Degenerative changes include chondrosis, inter vertebral osteochondrosis and osteophytosis while the reparative process means tissue proliferation.
The ossification is of focal character and occurs more frequently in the lower than in the upper part of the vertebral column, commencing in the lateral parts of the annulus fibrosus where compact bone is formed and commonly results in the picture of Bamboo spine. The ossification of anterior longitudinal ligament is particularly characteristic.
The sacroiliac and peripheral joints show evidence of chronic inflammation with cellular infiltration and hyperplasia of the synovia, destruction of articular cartilage and in late stages fibrous and bony ankylosis.
Laboratory findings
There are no specific laboratory tests which are diagnostic of ankylosing spondylitis. In patients with active disease erythrocyte sedimentation rate and C-reactive proteins are elevated.
Mild degree of anemia may be present (normocytic normochromic). Serological tests (Rheumatoid factor and anti-nuclear antibodies) are negative: IgA levels may be increased. Serum proteinpoly saccharide ratio is slightly raised.
Radiological changes
The earliest changes are seen in the sacroiliac joints. Symmetrical involvement of both sacroliac joints is characteristic. There is blurring of cortical margins of the subchondral bone, followed by erosions and sclerosis.
The juxta position of inflammatory decalcification and sclerotic foci is very typical. Progression of the disease leads to pseudo widening of the joint space and as fibrous and bony ankylosis supervene, the joint may become obliterated.
Annulus fibrosus may undergo necrosis and ossification giving rise to bony bridging. There appears bony union of all the vertebral arches with the result that a single bony element runs from the cervical to lumbar spine. Bony union arises from calcification of the various ligaments giving a typical bamboo spine appearance.
Course of the disease
It is extremely variable and can range from mild disability (pain in the back) to severe degree of incapacity. Onset of the disease in early life carries worse prognosis.
Treatment
Treatment in most of the cases is symptomatic since no cure is available, but the disease can be controlled to some extent. It comprises of drugs (NSAIDs corticosteroids, sulfasalazine), radiotherapy, physiotherapy and surgery. NSAIDs are used to give relief from pain. Out of these indomethacin, phenylbutazone. Diclofenac sodium and naproxen are the one commonly employed.
Indomethacin is a potent anti-inflammatory drug. Dose 25-50 mg 2 times a day or slow release preparation 75 mg once or twice a day. Side effects include gastric irritation, nausea, anorexia and psychosis diclofenac sodium (100-150 mg in 2-3 divided doses) is also effective. Side-effects include GI ulceration, epigastric pain, skin rash.
Sulfasalazine (2-3 g/day) is useful in reducing axial and peripheral joint symptoms as well as reverse inflammatory changes. Side-effects include skin rash, fever, nausea, loss of appetite.
Sulfasalozine is a disease modifying agent and is especially useful in patients with predominant peripheral joint involvement. Corticosteroids are of limited value and have been prescribed in acute stage. Local infiltration of steroids (intralesional or intrarticular) may be beneficial in patients with persistent synovitis not responding to treatment.
Radiotherapy
It has been employed in the past to effectively arrest the inflammatory changes of ankylosing spondylitis. But there is no change in ultimate results of the disease. Moreover patients receiving radiotherapy have risk of developing leukemia, bone marrow aplasia and increased morbidity due to malignancy.
Physiotherapy
Therapeutic exercises occupy an important place in the treatment Qf ankylosing spondylitis. Special mobilization exercises are necessary in preserving or promoting movements of the spine together with exercises for strengthening the muscles of the back.
Exercise on all fours, both stationary and crawling as well as in squatting postures are recommended. In addition to it patient must have breathing exercises to prevent rigidity of the thorax.
The muscles of patients of ankylosing spondylitis (A.S.) respond well to heat. Intensive heat treatment (warm air, thermal spa, underwater massage) are beneficial and should be employed. Heat treatment is the most favored way of treating A.S.
Surgery. In advanced cases with marked disability,vertebral osteotomy, total hip arthroplasty are often advised to improve mobility. Results are guarded as the disease often follows a progressive course.
ANKYLOSING SPONDYLITIS
1. Inflammatory disease of unknown etiology, insidious in onset. Progressive and chronic.
2. Age group – second to third decade. More often in males.
3. Starts with pain in the back and stiffness of spine. Not relieved by rest. Spinal joints in lumbar, cervical regions and sacroiliac joints involved.
4. Kyphosis of spine. Movements of spine restricted, progressive ankylosis. Bamboo spine.
5. Symptoms due to pressure on spinal nerve roots.
6. ESR and C-reactive proteins elevated in acute process. Mild degree of anemia (normocytic normochromic) Rheumatoid factors and antinuclear antibodies (ANA) are negative. Serum protein polysaccharide ratio slightly raised. IgA levels may be elevated.
7. Radiology shows narrowing of joint space (Sacroiliac joints blurring of cortical margins, erosions and sclerosis). Ankylosis of spine.
8. Treatment, Physiotherapy. Analgesics and anti-inflammatory drugs. Radiotherapy and surgery.
