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Ankylosing spondylitis (AS) is a form of arthritis that involves primarily the spine and joints of the extremities, such as the shoulders, hips and knees. It strikes young adults (usually men in their 30s), causing pain, stiffness, eye inflammation, and possible disability in severe cases. It makes hip, shoulders, ribs, back and neck stiff and sore and can cause a stiff, inflexible backbone.

AS is a member of the family of diseases that attack the spine called spondylarthropathies. The cause of AS is not known, but all of the spondylarthropathies share a common genetic marker, called HLA-B27, in most affected individuals. It has a strong familial tendency and a male predilection. It is more common in westerners, but has low incidence in Japenese and Negroid population.

Disease Pathology: There is a preferential involvement of ligaments and tendons known as Enthesopathy. There are two basic affections-

  1. Synovitis of diarthrodial or synovial joints
    • Synovitis of the Sacro illiac joint in the back and the facet joints of veretebare causes destruction of articular cartilage and periarticular bone
    • The costovertebral joints (Rib articulating with back bone)  are commonly affected which causes reduced respiratory excursion
    • When other joints are affected the same changes occur
  2. Inflammation of fibro-osseus junctions of syndesmotic joints
    • This affects the intervertebral discs, SI joint ligaments, manubriosternal joint, pubic symphysis and the bony insertions of large tendons

These changes in the joint occur in three stages-

  1. Inflammatory reaction with round cell infiltration, granulation tissue and destruction of bone.
  2. Replacement of the granulation tissue with fibrous tissue
  3. Ossification of the fibrous tissue leading to ankylosis of joints

Symptoms of Ankylosing Spondylitis: The usual symptoms start with low back pain and often the diagnosis is delayed because symptoms are often attributed to more common back problems. A dramatic loss of flexibility in the lumbar spine is an early sign of AS. Although most symptoms begin in the lumbar and sacroiliac areas, they may involve the neck and upper back as well.The usual symptoms include:

  • Insidious onset of backache and stiffness in an adolescent or young adult, recurring at a number of intervals over a number of years
  • Pain may be referred into the buttock and be confused with sciatica
  • Early in the disease process there is little to find on clinical examination apart from slight loss of the lumbar lordosis, limitation of extension of the spine and SI joint tenderness
  • Later patients have the characteristic posture because of Loss of lumbar lordosis, thoracic kyphosis, forward thrust of the neck and flexed hips and knees
  • In advanced cases the entire spine may be completely ankylosed or fused thus severely restricting the movements of back.
  • Chest expansion is often markedly reduced
  • Peripheral joints (shoulders, hips and knees) are involved in over 30% of cases

Extraskeletal manifestations : Often there is involvements of other organs that is other than bone, joint, ligaments and tendons-

  • Eyes: uveitis and conjunctivitis in 20%
  • Heart: aortic valve disease, carditis (rare)
  • Lungs: pulmonary fibrosis (rare)
  • GU: prostatitis

Investigations:

X-rays

  • The cardinal sign and earliest feature is sacroiliitis, with the iliac side affected first followed by ankylosis
  • Vertebral bodies become squared and later syndesmophytes form between the bodies, bridging several levels which can lead to "Bamboo" or "Rugger Jersey" spine
  • Peripheral joints may show erosive arthropathy or ankylosis

Special Investigations

  • Inflammatory markers are raised early in the disease
  • HLA-B27 present in 90% of cases, but it is important to note that only a fraction of people with the HLA-B27 antigen develop ankylosing spondylitis

Treatment

The majority of patients despite the disease can lead an active life. The severity of joint involvement and the degree of systemic symptoms vary greatly from one individual to another. Early, accurate diagnosis and therapy may minimize years of pain and disability

Aims of treatment are:

  1. General measures to maintain a satisfactory posture and preserve movement
    • Physiotherapy and exercise are to be encouraged
    • The aim is to remain as mobile as possible for as long as possible
  2. NSAID's to help with pain and stiffness
    • These can help the patient to perform exercise but do not themselves affect the course of the disease
  3. Surgery to correct deformity and restore mobility
    • Corrective osteotomies of the lumbar and cervical spine can be performed if the deformity is severe enough, but are potentially hazardous
    • Total joint replacement, especially THR may be needed, but they have a higher infection  and failure rates.

 Careful evaluation needed following cervical spine injury as they can have unstable fractures with a risk of developing non-union. Proper sleep and walking positions, coupled with abdominal and back exercises, help maintain posture. Continuing care is critical. AS is a lifelong problem, and people often fail to continue treatment, in which case permanent posture and mobility losses occur.