Children heal bone in a way adults cannot imagine.

What the crush does is cause the muscle to swell inside the compartment it lives in.

The compartment is a closed space wrapped in fascia, which does not stretch.

When the pressure inside it rises past a certain point, blood stops getting into the tissue, and once blood stops getting into the tissue you are on a clock.

It is called acute compartment syndrome.

The treatment is a fasciotomy, which means opening the compartment surgically to release the pressure.