Shoulder Rotator Cuff MRI and IL-8: Yes Virginia There is a Santa Claus?
The concept that structural changes like a rotator cuff tear seen on MRI are causing pain is so ingrained into modern medical thought that doctors and patients alike believe this like a 5 year old believes in Santa Claus. Like the latter, however, the validity of the concept is highly questionable. Take for example a new shoulder study that shows that pain with rotator cuff tears doesn’t really depend on the size of the tear, but instead on the levels of a nasty inflammatory cytokine that’s invisible to MRI.
Patients are conditioned by their doctors to believe that what’s seen on a shoulder MRI explains their pain. As a doctor that knows better, it can be a bit frustrating at times to try and convince them otherwise. Why even try? Because study after study continues to show that shoulder MRI results often can’t predict why the patient hurts. So what does predict shoulder pain? Turns out it may have much more to do with invisible chemicals than visible structural damage.
The new study was performed in Japan where joint fluid was obtained from 38 patients before and after orthopedic rotator cuff surgery. The fluid was then analyzed using ELISA (similar to our ongoing knee arthritis micro-environment study) for various chemical messenger molecules (cytokines). Interestingly, but not surprising, larger rotator cuff tears were associated with less pain. On the other hand, more pain was accurately predicted by more IL-8 (an inflammatory cytokine) in the joint fluid.
The upshot? Everyone from physicians to patients alike believe deeply that what they see on a shoulder MRI is what’s causing the pain. However, that belief is a bit like Santa Claus – merely a strong and widely held belief without much evidence. In reality, shoulder pain in rotator cuff tear patients is determined by a chemical that’s invisible to a Rotator Cuff MRI. So while the Sun newspaper at the turn of the century told Virginia there was a Santa Claus, in shoulder imaging it’s time for doctors and patients to give up the structure=pain myth that causes hundreds of thousands of unnecessary shoulder surgeries a year!