“Trans Scapula Scanning”

A new ultrasound technique for evaluating subscapularis function ?

The activity of subscapularis has always been difficult to assess objectively. The inferior border of the muscle is palpable and scannable in the posterior axilla, but this is impractical to do during functional activities. 

 

Transcapula scan of subscapularis (ssc) contracting during belly press manouver. (is) infraspinatus, the bright line above (scap) is the scapula.

Examination from the back has not been previously described as the muscle lies deep to the scapula, however I have been experimenting with a technique for scanning through the bone using standard low frequency curved ultrasound probe.

Over most of the scapula the bone is too thick, and all that is seen is a mirror image artefact of the overlying infraspinatus. At its thinnest point however, in the subjects I have looked at up to now, the sound penetrates through the scapula and the subscapularis muscle can be identified and its activity can be seen as the muscle belly thickening.

The technique requires some perfecting, and it may be that the scapula is not thin enough in every patient (as is the case for trans cranial scanning in adults, where 15% of the population do not have a sufficiently thin window in the skull)

If you have a low frequency probe, have a go and let us know how you are getting on.