EB: "My doctor has ordered me to stop playing until my shoulder gets replaced".

Not knowing the details I better not dispute against your doctor but (being a quack myself) there ought to be ways playing concertina safely just keeping one arm and shoulder passively in place. One attraction with the concertina in my view is that it may be played staying in bed...I actually took up concertina myself - and thus gave up the violin - in some despair when I got a paresis of the right arm for a year after a neck injury and fiddling with the left only became somewhat limited...