I've only ever seen a sling in like a US movie or series. In Germany, these things basically don't exist.
We know immobilizing parts of the body causes complications in recovery. The general outcome is worse. So we try to immobilise as little as possible and tell you to keep moving your other joints.
The problem ofc: if you have a broken hand you will have inconvenient reflexes and you can make it worse.
Immobilizing the entire arm prevents that and prevents us doctors from being sued?


