What is an avulsion fracture? From the Cleveland Clinic:
An avulsion fracture is where a small piece of bone attached to a tendon or ligament gets pulled away from the main part of the bone. Ligaments hold your bones, joints and organs in place while tendons connect muscles and bones. In an avulsion fracture, your bone moves one way and your tendon or ligament moves in the opposite direction with a broken chunk of bone in tow.