A stress fracture is a partial or complete bone fracture that results from repeated application of stress lower than the stress required to fracture the bone in a single loading. Otherwise healthy athletes, especially runners, sustain stress injuries or fractures. Prevention or early intervention is the preferable treatment. However, it is difficult to predict injury because runners vary with regard to biomechanical predisposition, training methods, and other factors such as diet, muscle strength, and flexibility.
Stress fractures account for 0.7% to 20% of all sports medicine clinic injuries. Track-and-field athletes have the highest incidence of stress fractures compared with other athletes. Stress fractures of the tibia, metatarsals, and fibula are the most frequently reported sites. The sites of stress fractures vary from sport to sport (eg, among track athletes, stress fractures of the navicular, tibia, and metatarsal are common; in distance runners, it is the tibia and fibula; in dancers, the metatarsals).
In the military, the calcaneus and metatarsals were the most commonly cited injuries, especially in new recruits, owing to the sudden increase in running and marching without adequate preparation. However, newer studies from the military show the incidence and distribution of stress fractures to be similar to those found in sports clinics.
Fractures of the upper extremities are relatively rare, although most studies have focused only on lower-extremity injuries. The ulna is the upper-extremity bone injured most frequently. Imaging plays a key role in the diagnosis and management of stress injuries. Plain radiography is useful when positive, but generally has low sensitivity. Radionuclide bone scanning is highly sensitive, but lacks specificity and the ability to directly visualize fracture lines.
In this article, we focus on magnetic resonance imaging, which provides highly sensitive and specific evaluation for bone marrow edema, periosteal reaction as well as detection of subtle fracture lines.
Causes :-
a. There is an increased injury rate with increasing distance beyond approximately 32 km/wk.
b. Any rapid change in the training program, whether a sudden increase in mileage, pace, volume, or cross-training activity that has been inserted into the program without adequate time for physiologic adaptation to accommodate the new forces.
c. Hard or cambered training surfaces also are important precursors to lower extremity overuse injuries.
d. Failure to follow intensive training days with easy ones also can contribute to injury, a narrow width of the tibia and increased external rotation of the hip.
e. When muscles become fatigued, they transmit greater energy to the surrounding bone. Thus, it is hypothesized, the relatively lesser muscle and bone mass of the lower leg, particularly around the tibia, may explain the greater frequency of tibial stress fractures.
f. Stress fracture development and that athletes with smaller bones in relation to body size are at greater risk for bony injury. repetitive loading history of runners in a single plane leads to asymmetric cross-sectional geometry of the tibia.
g. Females are at greater risk for sustaining stress fractures than males. The female athlete triad (menstrual irregularity, disordered eating, and osteoporosis) emphasizes the susceptibility of young female athletes to stress fractures and contributes to the clinical impression that females are at an increased risk for such injuries compared with young men.
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