Types

What types of fractures are there?

Because of the thick layers of muscle around the shaft of the humerus, open fractures are uncommon. They do occur with high energy impact injuries and with gunshot wounds but are much less common with lower energy event such as falls and throwing injuries. Pathological fractures through abnormal bone occur frequently in osteoporosis and may also happen if there is a deposit of cancer in the shaft of the humerus. This is a rare event but may be the first sign of the cancer problem in some people.

Fractures of the shaft of the humerus that occur from bending forces may have a short oblique pattern or may have multiple fragments. Compression fractures happen when the force is primarily along the line of the bone. This can occur in a fall from a height. The fracture pattern is often transverse.

Twisting injuries result in a spiral fracture pattern in the shaft of the humerus. This can happen when the lower arm is locked or trapped in machinery and the body rotates. Direct twisting forces as in arm wrestling have been known to cause a fracture and so has throwing. Throwing grenades during military training has a particularly high incidence of spiral fracture of the humerus!

The soft tissue injured around a humerus fracture may be considerable. After the bone breaks the sharp end tear through nearby structures such as muscle and even nerves or blood vessels. The radial nerve that supplies the muscles that straighten the wrist and fingers runs next to the shaft of the humerus. It is quite vulnerable to injury. Other nerves and major blood vessels are more rarely damaged as part of a gunshot wound or a major laceration.