Trauma to the elbow often results in comminuted fractures of the olecranon. A fracture of the sternum is usually a comminuted fracture. Fractures that occur in the body may be vertical, horizontal, or comminuted (involving multiple fragments). Open reduction and internal fixation is reserved for cases that are severely angulated or comminuted. The ore is comminuted and the cobalt rich oxides are separated by froth flotation. The ore is comminuted using grinding machinery. Because the jaw can be highly comminuted, MMF and rigid internal fixation can be difficult.