What Is It?
When a bone breaks or cracks, the injury is called a fracture. In the arm, a fracture most often occurs in the long and slender midsection (shaft) of one of the three arm bones (the humerus, radius and ulna).
Fractures of the humerus (upper arm bone) In otherwise healthy people, most fractures of the humerus are caused by a direct blow to the upper arm. This often is caused by a motor vehicle accident or high-impact fall. Less often, the humerus can fracture because of a severe twist of the upper arm, a fall on an outstretched arm, or an extreme contraction of upper arm muscles. If the bone fractures because of an extreme muscle contraction, the break curves around the bone and is sometimes called a "spiral fracture" or a "ball-thrower's fracture." These fairly rare injuries tend to affect arm wrestlers and throwing athletes, especially pitchers, javelin throwers and discus throwers.
If the humerus breaks because of a low-impact bump or fall, this may mean that the bone has been weakened by an illness, such as osteoporosis or cancer. These are called pathologic fractures. Cancer-related fractures of the upper arm bone tend to occur in older people (average age 62), while trauma-related fractures of the humerus tend to affect younger people.
Fractures of the radius and ulna (forearm fractures) The forearm contains two bones, the radius and the ulna. The radius is on the same side of the arm as the thumb. The ulna is on the side of the little finger. When the forearm is fractured, either the radius or ulna may be fractured alone, or both bones may be fractured. In either case, the injury is almost always caused by a direct blow to the forearm, or by falling on an outstretched arm.
In the United States, forearm fractures are the reason for more than 750,000 office visits to orthopedic surgeons every year. Among young Americans, forearm fractures are common in teen-agers who fall while roller skating, in-line skating or skateboarding, while osteoporosis is a common risk factor for older persons with a forearm fracture.