Anatomy

What structures are most commonly injured?

At the shoulder the humerus has a rounded end (the humeral head) that forms part of the shoulder joint. It is joined to the shaft of the bone by a region called the neck of the humerus. Most of the shaft of the bone is tubular but it flattens out at the lower end. The upper arm is so muscular that it is quite difficult to feel the actual bone. In this guide we are concerned with injuries to the tubular shaft of the humerus. Injuries affecting the head and neck of the humerus are considered in A Patient's Guide to Fractures of the Shoulder. Those affecting the lower end are covered in A Patient's Guide to Fractures of the Elbow.

Related Document: A Patient's Guide to Adult Shoulder Fractures

Related Document: A Patient's Guide to Adult Elbow Fractures

The shaft of the humerus can be broken almost anywhere along its length, although a fracture is more common at the middle of the shaft and below. There are different patterns of fracture depending on the mechanism of injury, but all involve a complete break around the entire circumference of the tubular bone. It is virtually impossible to break a tube on one side only. This is significant because it means that any break of the humerus interrupts the function of the arm. You cannot lift up or rotate the arm below the break.