Stress Fractures, A Repetitive Micro-trauma
By: John Roberts
I saw a college athlete recently who complained of shin pain. He had been upping his running mileage in preparation for the upcoming cross country season. His pain was due to a stress fracture. Every year, somewhere between five and 30 percent of athletes develop a stress fracture. Briefhaupt first described the condition in 1855 when examining military recruits, a group that frequently develops stress fractures.
Everyone is familiar with bone fractures, especially those from an acute injury. Even untrained eyes can usually identify the fracture lines on an X-ray; the bone often looks like a broken stick. Stress fractures, however, can be much more difficult to diagnose.
Stress fractures, as the name implies, are caused by ongoing stress on bone tissue. This repetitive microtrauma causes disruption of the microscopic structure of the bone over time that eventually exceeds the bone’s ability to heal itself. A tiny crack subsequently develops in the bone that may or may not be visible on an X-ray. Think of bending a piece of metal over and over – it eventually weakens and breaks.
Stress fractures predictably occur in bones that are prone to repetitive stress based on the sporting activity. The fractures can involve any bone, but the most common locations and their associated sports include the hip, leg, and foot (runners & jumpers), the spine (gymnasts, divers, and volleyball players), arms (throwers), and ribs (rowers). The forces experienced by bones in the feet and legs can be up to twelve times a person’s weight. Stress fractures are one of the five most common injuries in runners and account for up to half of injuries in soldiers.
Risk factors for stress fractures can be divided into intrinsic (originating within the person), and extrinsic (coming from outside the body). Intrinsic factors include being genetically female (twice as likely as in males), weak or imbalanced muscles, prolonged rest that can lead to weak bones, leg misalignment, being tall, and having poor foot structure.
One very important intrinsic risk factor is osteopenia (decreased bone mineral density) and its more severe form, osteoporosis. This is especially worrisome in young female athletes who can develop the “female athlete triad.” This triad includes disordered eating such as anorexia and bulimia, amenorrhea (no menstrual periods) and decreased bone density. Any young woman who has a stress fracture needs to be evaluated for the female athlete triad.
Extrinsic risk factors usually include an excessive amount or intensity of training, a poor training surface (too hard or irregular), and worn out or improperly fitted shoes. Running shoes should be fitted correctly to the foot structure, preferably at a professional running shoe store, and should be changed out every 300 miles or so. Other extrinsic factors include smoking, poor nutrition, and medications, especially oral steroids.
People with stress fractures typically present with a common history. The pain usually comes on gradually and is felt at the end of the activity causing the pain. The pain then becomes more severe, causing the person to limit participation. During the early phase of the injury the pain is relieved with rest. This is usually not the case as the damage progresses. Many patients complain of pain at night and athletes frequently have a hard time pinpointing a specific location of the pain.
The physical exam often offers clues to the diagnosis. Pressing or tapping the affected area usually elicits pain. Swelling or redness may be present. Putting stress on the bone by hopping, etc. may worsen the pain.
If the history and physical exam does not identify the problem other tests need to be performed. Conventional X-rays are frequently normal. Often CT or MRI scanning is required to locate and assess the severity of the fracture. Nuclear bone scans can also be helpful. Which study to order is usually determined by the site of the possible fracture as well as other medical conditions the patient may have.
Treatment is fairly simple – break the cycle of repetitive stress on the bone. This is done by cross training to strengthen the muscles around the fracture site without putting undue stress on the fracture site. Rehabilitation usually takes four to 12 weeks depending on the site and severity of the fracture. Occasionally stress fractures do not heal and require surgical stabilization. One rule of thumb is to increase activity about ten percent a week during rehabilitation. There is some evidence in animal models that treating the pain with non-steroidal medications such as Aleve and ibuprofen may delay healing, so we usually try to stick with Tylenol and other local treatments such as icing.
– Dr. John Roberts is a retired member of the Franciscan Physician Network specializing in Family Medicine.