Stress Fractures in Athletes
Repetitive Stress Can Cause Injury to Lower Extremity Bones
Stress fractures are partial fractures in load bearing bones that result from repetitive loading of the bone. If the repetitive stress creates more force than the bone can withstand, a stress fracture occurs.
A number of contributing factors can lead to stress fractures including sudden increase in mileage or training, poor mechanics, and inadequate shoe support. Lower extremity stress fractures are seen in the sports of track and field, distance running, jumping sports (basketball), and dance. Upper extremity stress fractures are rare but can occur in gymnasts due to the repetitive loading of the arms during tumbling.
Noncritical and Critical Stress Fractures
Stress fractures can be classified as noncritical or critical. Noncritical stress fractures are fractures that heal well with return to activity between six and eight weeks. These types of fractures tend to be seen in the medial tibia, fibula, and the second, third, and fourth metatarsals (long bones in the foot).
Critical stress fractures are those in which there is nonunion (separation within the bone at the fracture site) after a time of rest. These are fractures that tend to not heal well and require further medical treatment (surgical intervention). These fractures include anterior tibia, medial malleolus (distal end of tibia), talus, navicular, fifth metatarsal, and sesamoids (small round bones located underneath the head of the first metatarsal).
According to a recent study by Fredericson, M., Jennings, F., Beaulieu, C., and Matheson, G. published in Topics in Magnetic Resonance Imaging (October, 2006), stress fractures make-up up between .7% to 20% of injuries treated in the sports medicine clinic. Track and Field athletes had the highest incidence of stress fractures. The most common sites for stress fracture included the tibia, metatarsals, and fibula.
The location of stress fractures is unique to each sport. Fractures of the second and third metatarsals are more common in ballet dancers. Distance runners tend to have stress fractures in the tibia and fibula. Track athletes are at risk for stress fractures of the tibia, but also for the navicular and metatarsals as well.
Signs and Symptoms of Stress Fractures
Athletes with stress fractures tend to complain of a gradual onset of pain (cannot identify one specific cause) that reduces with rest and increases with activity. A dull, throbbing sensation may be felt at night directly over the fracture site when the rest of the body settles down. The athlete can usually point to the specific site on the bone that is painful (versus soft tissue pain). Last, heat may be felt directly over the stress fracture site.
Diagnostic Tools for Stress Fractures
If a stress fracture is suspected, the athlete needs to be referred to a physician for diagnosis and proper management. Because most stress fractures will not be seen on an x-ray film, the athlete may need to be referred for a bone scan or an MRI (magnetic resonance imaging).
The bone scan is a unique assessment tool in which radionucleotide material is injected into a vein and slowly absorbed into healing bones. The radionucleotide is absorbed into the fracture site of the bone at a higher concentration. Several hours after the initial injection, the body is then scanned for radioactive signals. A stress fracture will appear darker on the film than healthy bone. The body will then excrete the radionucleotide material within a 24 hour period (Anderson, M.K., Parr, G.P., & Hall, S.J., 2009).
Preventing stress fractures through a gradual increase in training and proper mechanics is ideal. When stress fractures do occur, early treatment will hasten recovery.
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