Ankylosing spondylitis is an seronegative arthritis in which the sacroiliac joints and axial spine undergo a progressive ossification. Ankylosing spondylitis attacks the insertions points of ligaments, tendons, fascia, and fibrous joint capsules, and yields fibrosis and ossification of the insertions. Ligamentous attachments are collectively referred to as “entheses”, hence “ensethopathy” is a common feature of ankylosing spondilitis.
The disease typically starts at the sacroiliac joint (SI joint is fused in the pelvic radiograph above), and spreads upwards, ossifying ligaments of the posterior facets of the spine and fusing vertebrae together, thus stiffening the spine and decreasing range of movement. Ossification within the anulus fibrosis (the fibro-cartilaginous ring that is wrapped around the outside of the intervertebral disk ) yields syndesmophytes , radio-dense lines that connect vertebrae. With enough syndesmophyte formation, the whole spine has an undulating contour called “Bamboo Spine”. A characteristic combination of bone erosion and formation occurs in this disease, such that the vertebrate become less concave and more ‘square’. This squaring of the vertebral bodies is typical of ankylosing spondilitis.
Onset is typically in young people, usually in their late teens or twenties, and rarely after age of 35. Clinically, the disease is usually first noticed as a persistent backache which is not relieved by rest, and improves with exercise (unlike muscular back pain). It may also present as sciatica, peripheral joint pain, a painful sacroiliac joint or chest pain. Associated symptoms are anorexia, weight loss and a low grade fever. At its extreme, ankylosing spondylitis results in an ossification of the axial spine such that mobility is greatly reduced, and the spine becomes completely stiff and flexed, and the hips may be ankylosed as well, affecting gait. The spine is also at increased risk of fractures, further deforming the person’s stance. However, only 20% of patients reach the extreme of a completely rigid spine.
Medical treatments include analgesia and an emphasis on posture and exercise to retain flexibility and range for as long as possible. Swimming is recommended.
When AS has been present for several months the back may stiffen, usually lower down; and in some patients the disease then dies out, causing no further trouble. The stiff back is often painless and does not interfere with physical activity, because the upper part of the spine, the neck, hips and limbs can remain quite normal. If you feel stiff in the early morning this is a sign of inflammation and perhaps it may be an hour or so before you have properly limbered up – it may indicate the need for anti-inflammatory drugs.
In its early stages AS causes considerable pain, but effective treatment is available to relieve this, even though the discomfort is not always banished. In some people the disease becomes much less active, or even ceases completely. In others the disease continues to be active, causing pain and stiffness. At first you will most probably be able to carry on with your work and lead a normal life. Later you may find it difficult to continue in the same job.