What is the main difference between a compound fracture and a contusion?

Injury Type. A contusion is essentially an area of injured tissue with ruptured capillaries - what is commonly referred to as a "bruise." a compound fracture is also called an "open fracture" and it is a broken bone that has erupted through the skin.
Very different. A contusion is the bio equivalent of a bone bruise from blount force trauma a compound fracture is where a bone breaks and protrudes thought the skin.