Ultrasound is very useful to differentiate the various causes, thereby informing therapy. Bursitis is the most common finding, with varying degree of inflammation, amenable to steroid injection treatment. Cuff tears would benefit from surgical repair. For those with minimal ultrasound pathologies, doing surgery would be a mistake: depression rates are high, and that’s not amenable to surgical correction of the minimal pathologies.
Ultrasound May Be Useful for Grading Rotator Cuff Tendinopathy
Amongst the usual shoulder ultrasound findings like bursitis, effusion, tendon tears and synovitis, tendinosis (or tendinopathy) changes are the most subtle.
Even then, the inter-rater reliability is high with regards to, not merely detection of, but even measurements of fibrillar disruption, neovascularity, tendon thickness and dystrophic calcification.
This augurs well for ultrasound as the imaging modality of choice in the initial assessment of shoulder pathologies.
It is a common misconception (among doctors, no less) that MRI is preferred over Ultrasound (US) for evaluation of musculoskeletal complaints because MRI yields much higher resolution than US: it does not. In fact, spatial resolution for US on a 10 MHz linear probe is 150 microns, while a standard MRI resolves at 450 microns. That’s 3 times better on the US than MRI. In the latest ultra-high frequency probe operating at 70 MHz, resolution is down to an eye-popping 30 microns. Yes, you see skin structures and nerve fascicles at that resolution!
Misconceptions aside, US is not replacing MRI anytime soon. They each have their pros and cons, which is the subject of another day’s post. But US is increasingly replacing MRI as a non-inferior (often superior) point-of-care tool in the clinic.
Today’s post illustrates its utility in shoulder complaints. Bursitis is the commonest cause of pain, followed by rotator cuff issues. Far less commonly is it an osteoarthritic cause, for which MRI has the advantage of visualization deep into the joint as well as the bone, which US cannot penetrate. The other advantage of MRI is when multiple pathologies are suspected (eg SLAP lesions, OA, tendinopathies), whereby all lesions can be picked up in one scan. Otherwise, in specific lesions like cuff tears and tendinopathies, US, in conjunction with dynamic manoeuvres, can deliver superior sensitivity and specificity with high inter-operator reliability in trained hands.
