Hairline fracture
| Stress fracture | |
|---|---|
| Synonyms | Hairline fracture |
| Classification and external resources | |
| Specialty | Orthopedics |
| ICD-10 | M48.4, M84.3 |
| ICD-9-CM | 733.93, 733.94, 733.95 |
| DiseasesDB | 7842 |
| eMedicine | radio/783 orthped/446 pmr/134 |
| MeSH | D015775 |
Stress fracture, also known as a hairline fracture, or fissure fracture, is a fatigue-induced fracture of the bone caused by repeated stress over time. Instead of resulting from a single severe impact, stress fractures are the result of accumulated trauma from repeated submaximal loading, such as running or jumping. Because of this mechanism, stress fractures are common overuse injuries in athletes.
Stress fractures can be described as a very small sliver or crack in the bone; and are sometimes referred to as "hairline fractures". Stress fractures most frequently occur in weight-bearing bones, such as the tibia (bone of the lower leg), metatarsals, and navicular bones (bones of the foot). Less common are fractures to the femur, pelvis, and sacrum.
Stress fractures most commonly present as pain with weight bearing that increases with exercise or activity. The pain usually subsides with rest but may be constantly present with a more serious bone injury. There is usually an area of localized tenderness on or near the bone and generalized swelling to the area. Percussion or palpation to the bone may reproduce symptoms.
Bones are constantly attempting to remodel and repair themselves, especially during a sport where extraordinary stress is applied to the bone. Over time, if enough stress is placed on the bone that it exhausts the capacity of the bone to remodel, a weakened site—a stress fracture—on the bone may appear. The fracture does not appear suddenly. It occurs from repeated traumas, none of which is sufficient to cause a sudden break, but which, when added together, overwhelm the osteoblasts that remodel the bone.
Stress fractures commonly occur in sedentary people who suddenly undertake a burst of exercise (whose bones are not used to the task). They may also occur in athletes completing high volume, high impact training, such as running or jumping sports. Stress fractures are also commonly reported in soldiers who march long distances.
Muscle fatigue can also play a role in the occurrence of stress fractures. In a runner, each stride normally exerts large forces at various points in the legs. Each shock—a rapid acceleration and energy transfer—must be absorbed. Both muscles and bones serve as shock absorbers. However, the muscles, usually those in the lower leg, become fatigued after running a long distance and lose their ability to absorb shock. As the bones now experience larger stresses, this increases the risk of fracture.
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