FAMILY MEDICINE® COLUMN
By John C. Wolf, D.O.
Associate Professor of Family Medicine®
Ohio University College of Osteopathic Medicine

MANY, REPEATED MINOR INJURIES CAUSE STRESS FRACTURE

Question: I run about 20 miles per week. Recently my foot became very sore without having a specific injury, or at least an injury I noted at the time. I saw my family doctor who had an X-ray taken, but it turned out normal. Since my pain was rather intense, she then ordered a bone scan which showed a fracture. Why did it show my broken foot bone when the X-ray did not?

Answer: Bone scans and X-rays show different qualities of bone. X-rays pass through soft tissue skin, muscle, intestine, lungs, etc. fairly easily but are blocked by bone, teeth and other solid objects. If a person stands between the source of X-rays and some device which can measure the amount of radiation, usually X-ray film or a CAT scanner, shadows of these solid objects will appear white. Shadows of soft tissue, because it blocks less radiation, will be gray to black the darker, the less radiation blocked. If you've ever seen an X-ray, you probably remember this grey, black and white color combination.

A broken bone is very apparent on an X-ray when the broken ends are pulled apart and twisted to an unusual angle. On the other hand, when a fracture is just a hair-line crack without a change in the overall shape of the bone, it can be very difficult to detect on X-ray film. This is the type of fracture you had in one of your foot bones, and when it occurs as the consequence of repeated minor trauma of running or prolonged walking, it is called a "stress" or "march" fracture.

A second X-ray taken several weeks after the injury will show signs of healing at the fracture site even if the first X-ray did not. Since the treatment for a sprained or strained foot is different than the treatment of a fracture, waiting two or three weeks to take that second X-ray isn't acceptable. With a bone scan your doctor can more quickly discover the cause of your discomfort. In your case it was a stress fracture.

Bone scans work because in an adult the bones are not inert, dead objects, as many people think. Instead, bones are constantly being renewed with old cells taken away and new cells deposited. The rate of bone growth and bone loss is equal so that the overall appearance is one of no change from day to day.

A fracture, regardless of its cause or severity, puts the cell growth process into "high gear" with the deposit of many new cells. This change occurs only at the area of the fracture and is responsible for healing. The bone scan directly measures the bone-building activity itself. Therefore, it will show a stress fracture much, much sooner than will a plain X-ray.

Question: How did I get a fracture without an injury I recall?

Answer: Bones are quite strong. They support our weight and the force of our muscles. It takes considerable force to break a healthy one. Automobile accidents, sports injuries and falls often occur with sufficient force to break bones everyone knows this. The sort of fracture you have, a stress fracture, is also common. It results from many, repeated small shocks (frequently due to running or walking) rather than the single, major trauma of an accident.

The foot and leg take a terrible pounding. The weight of the body comes crushing down on one foot with every step. This load is then transferred on up the leg bones. The muscles of the leg and foot react to forcefully propel the body forward and, thereby, subject the other foot and leg to the same punishment.

The trauma of walking and running is apparent to all of us when we jog farther than we are accustom. That is what causes our feet and legs to get sore. Vigorous training such as your jogging can causes sufficient stress to produce fractures of the foot or lower leg bones. Competitive athletes and military recruits who spend hours each day marching in formation are also common victims of stress fractures.

People with stress fractures rarely remember a specific moment when the foot pain began. Your experience is, actually, quite typical in this regard.

Family Medicine® is a weekly column. To submit questions, write to John C. Wolf, D.O., Ohio University College of Osteopathic Medicine, Grosvenor Hall, Athens, Ohio 45701.