Bone Fusion &
It is possible that over time, some of the small bones in the spine (vertebrae) fuse, making the back less flexible and slowly give rise to a hunch.1 It is also probable that all the bones of the spine fuse completely. When this happens, the vertebrae become brittle and prone to fractures.2
Unfortunately, the disease is not limited to the spine. Besides the spine, there is the involvement of some joints in the pelvic bone (sacroiliac joints) and entheses (tissues present in our joints).
The outcome of this condition is, therefore, impaired spinal mobility, postural abnormality, buttock pain, hip pain, peripheral arthritis, enthesitis (inflammation of entheses), and inflammation of fingers (dactylitis-“sausage digits”).
Impaired spinal mobility
Ankylosing Spondylitis (AS) may also affect organs other than the spine and joints. There is a possibility of developing digestive disorders (inflammatory bowel disease – up to 50%), inflammation of the eye (acute anterior uveitis – 25% to 35%), and psoriasis (approximately 10%).1
Inflammation of the eye
AS is also associated with an increased risk of cardiovascular disease, pulmonary complications, vertebral fragility fractures, atlantoaxial subluxation, spinal cord injury, and, rarely, cauda equina syndrome (disease of the lower back).1
Spinal fusion, the characteristic feature of AS, slowly occurs over a period of about 2 years and progresses further.3 Nevertheless, the rate of progression and severity of the spinal disease is not the same and varies among different people. In some patients, it does not progress beyond sacroiliitis (inflammation of one or both of your sacroiliac joints). In some others, there is complete ankylosis at a young age.4
- Wenker KJ, et al. Ankylosing spondylitis. [Updated 2018 Nov 14]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470173/.
- A patient’s guide to ankylosing spondylitis. Available from https://www.umms.org/ummc/health-services/orthopedics/services/spine/patient-guides/ankylosing-spondylitis. Accessed on 17 December 2019.
- Progression of spinal fusion in ankylosing spondylitis. Available from https://clinicaltrials.gov/ct2/show/NCT00085995. Accessed on 17 December 2019.
- Braun J, et al. Staging of patients with ankylosing spondylitis: a preliminary proposal. Ann Rheum Dis. 2002;61 Suppl 3(Suppl 3):iii9–iii23.