Stress Fractures

Stress fractures were first described in 1855 by a military surgeon who observed new recruits with foot pain and swelling. Interestingly, this was 40 years before the advent of x-rays. The recruits were made to walk long distances carrying heavy back packs and supplies. The result was that some of them sustained a condition termed "march" fractures.

In the last 10 years there has been an explosion of interest in running, aerobics, and physical fitness in general. Besides the many benefits derived from these activities, there has been a dramatic increase in the number of cases of stress fractures (march fracture, fatigue fracture, insufficiency fracture) seen. Recent studies show that stress fractures account for almost five percent of all running injuries.

Definition
A stress fracture is a crack that occurs in a bone due to excessive pressure being exerted that exceeds the bone's ability to withstand those pressures. The excessive pressure can be instantaneous as in trauma, or cumulative as in overuse problems.

Causes
The actual cause of stress fractures is poorly understood. The most popular theory is that stress fractures result from an overload on the bone caused by muscle contraction. Typically, the runner will relate a change in training routine, a different, harder, running surface, longer distances, increased speed or new running shoes. All this requires more prolonged muscular activity on the bones. This prolonged increased muscular activity causes changes in the bone physiology. It is thought that the bone responds to these pressures by actually reabsorbing or weakening first, then laying down new bone in response to the extra pressure. It is during this weakening phase that the bone can crack. In many cases I see certain bones increasing in size in response to excessive pressure over a period of time. A crack develops in the bone when even this rein forced response of the bone is insufficient to with stand the increased pressure. An example of this is in the metatarsals. There are five bones in the ball of the foot called metatarsals. All are basically supposed to work together and support the pressures placed on them. However, the first metatarsal bone often lifts up and allows for transfer of weight to the second metatarsal bone. This bone increases in size in response to the added pressure, but if the pressure continues, the bone breaks.

Other possible causes of stress fractures include: flat feet, which puts excessive pressure on the inside of the foot structure and changes the direction of pull of the muscles in the leg which govern the function of the foot; high arched feet, which are non-yielding and non-shock absorbing; short bones or abnormally functioning ones, which allow for increased areas of stress; certain types of local or systemic diseases or infections; or hormonal imbalances.

It must be pointed out that we also see stress fractures in non-athletes. This is especially true in older women with osteoporosis (decreased calcium). They often complain of pain of their feet or legs with no recollection of injury. A careful history almost always reveals a period where there was prolonged standing, walking, carrying a heavy load, or change in shoe gear that preceded their problem.

The incidence of stress fractures is interesting. They occur most frequently in the metatarsal bones although they have been reported in almost every bone of the foot. The tibia and fibula (long bones in the lower leg) are also frequently subject to stress fractures. The femur, hip and even the arm and shoulder bones have been reported as stress fracturing. An example of one who might sustain an upper extremity stress fracture is a person who participates in arm wrestling. Not surprisingly, however, the legs and feet represent the highest incidence of stress fractures.

Signs and Symptoms
A complete clinical history is essential in the diagnosis of stress fractures. Any history of physical activity must be obtained whether the patient is a well-conditioned athlete or a non-conditioned, sedentary individual. Typically, the patient describes increased pain right at the exact site of the fracture. At the beginning the pain is present only after exercise and is relieved by rest. Usually the patient, not knowing what the problem is and thinking that it will go away, continues to exercise. The pain then becomes more severe and constant, unrelieved by rest. Swelling overlying the fracture site often ensues with difficulty in wearing shoes and even walking.

Diagnosis
Besides a relevant clinical history and examination as previously described, x-rays are essential. However, if the x-rays are taken in the first 10 to 14 days, no evidence of a stress fracture may be present. Some sources state that it may even be three weeks to three months before any bone healing is seen on x-rays.

X-rays are usually normal at the onset of symptoms. Special x-ray techniques to diagnosis stress fractures can be used when necessary. These are called bone scans. The fracture on a bone scan shows up as a collection of black dots on an x-ray film. Bone scans are useful in the early diagnosis of stress fractures and confirm their presence. In a study of 62 runners with stress fractures, the initial x-rays were positive in 47 percent of the cases, whereas bone scans were positive in 96 percent. Still, the most reliable sign is localized pain.

Treatment
The treatment for stress fractures is rest. If running causes pain, other activities such as cycling or swimming may be substituted to maintain general conditioning. It is rare to apply a cast. Usually a wooden fracture shoe, ace wrap, or support stocking is all that is needed. Typically, bone takes six to eight weeks to heal. Therefore, normal activities can be gradually resumed after the patient has waited a sufficient length of time, has no pain, and swelling has subsided.

Other forms of treatment include physical therapy such as whirlpools, padding, or taping, shoe treatment, or orthotics. Caution must be exercised especially with the overzealous individual who returns too soon or too vigorously to activity. A re-fracture may occur.

The best treatment is prevention. Most stress fractures are the result of too much, too soon, overuse, poor training habits, poor muscle tone, improper running surfaces, or poorly designed shoes. When I see a patient with a stress fracture, I am certainly concerned with rendering the proper treatment to ensure a complete recovery to normal activities. I am also concerned with determining the cause of the stress fracture. If this is not determined, then the problem may recur. In my experience, most stress fractures are caused by faulty mechanics and inability of the foot and leg to absorb impact shock. Orthotics have been shown to be effective in almost every case in controlling the cause of the stress fracture and pre venting its reoccurrence.

An example of this was a recent patient who developed repeated stress fractures of the right tibia when he ran over 40 miles per week. The patient was advised to either keep his weekly mileage below that level or use orthotics. He chose the latter and has not sustained any further problems.

Summary
A stress fracture is a crack that develops in a bone usually due to a variety of factors such as faulty foot structure, leg length differences, improper shoes, poor training habits, or hard unyielding surfaces. It is usually not immediately seen on x-rays, and the patient may benefit from early detection by utilizing bone scans. The fracture causes localized pain and disability. Treatment consists of appropriate supportive therapy and adequate steps to prevent it from recurring.