Causes

How do fractures of the humerus commonly happen?

Like any of the big long bones of the body the force that breaks the humerus can be bending, compressing, or twisting. A combination of these forces is the most common. An impact against the upper arm that causes a bending force on the bone may be the least common mechanism of injury. This type of injury does occur in high energy trauma, such as motor vehicle accidents or falls from a height.

Indirect bending forces occur when you fall on the outstretched hand or the elbow. This is a relatively common cause of an isolated humerus fracture and occurs quite frequently in the elderly. In the elderly, the bone may be more fragile than normal due to osteoporosis.