This is the 2nd post from one earlier this week on a patient referred for LBP and had (+) cluster of SIJ tests. Before reading this post, go back here to catch up.
A big detail that I left out from the first post is that this patient was referred to me for LBP, but he was already diagnoses with Ankylosing Spondylitis. I know, not fair. I knew this before the clinical exam but wanted to see myself what would pop up if this patient just came through the door and not been under medical management so far. This is a good opportunity to review AS.
Not to get into too much detail on pathology of AS, but here are some major points:
1. AS is considered a non-mechanical spine disorder (only ~1% of LBP) and in the same category as neoplasms, infections and other seronegative spondyloarthritides (such as reactive arthritis, Reiter’s syndrome, psoriatic arthritis and inflammatory bowel disease). It is a chronic inflammatory disease and could lead to spinal ankylosis. What we need to be able to differentiate as physical therapists is a ‘mechanical’ vs ‘non-mechanical’ cause of pain. Mechanical LBP is sprains, strains, IDH, SIJ pain, etc. For number sake, mechanical problems are very common and encompass ~97% of all LB symptoms.
2. Physical therapy is a major component of treatment for individuals with AS. Honestly if you missed this diagnosis, you are not doing much harm per say; but if symptoms do not improve as you expect, you need to refer out to a rheumatologist. NSAIDs are normally always prescribed (which patient is probably already taking) but new development of cytokine inhibitors to inhibit the activity of tumor necrosis factor has been a strong advancement in management. Referral at earlier stage would be better so do not overtreat.
3. The hallmark sign of AS is sacroiliitis (inflammation of the sacroiliac joints). This is why cluster of SIJ tests were positive. However, just like any other evaluation; only use the special tests for ~5-10% of your clinical exam and conclusion. You do not want to put all your eggs in a one basket.
Early Dx can be difficult in all regards but the following is commonly used criteria for Dx per Rudwaleit et al.:
2 of 4 criteria below will yield a 70% sensitivity and 81% specificity.
1. Morning stiffness of 30 minutes or more in duration.
2. Improvement in back pain with exercise but not rest.
3. Waking because of back pain during the second half of the night only.
4. Alternating buttock pain.
Here are some other diagnostic number values for AS that you can get from Lurie JD here (great article by the way!). The values from left to right are, “reliability, sensitivity, specificity, LR+, LR-“.
This post is intended to educate the physical therapist about the possibility of AS as a primary diagnosis for LBP. It is not all comprehensive but the points I made are the major ones that you need to be aware of. I would love to hear your comments about your thoughts on clinical diagnosis of AS and if you have had any experience with it.