Stress fractures are often difficult to early differentiate from other soft tissue injuries.
On the other hand to confirm early the diagnosis of a stress fracture an MRI is needed. Since 1972 the literature indicates that the detection of stress fracture by ultrasound was possible before x-ray findings. Stress fracture's detection by ultrasound will be described and analysed.
During the period 1995–2009, we evaluate with a physio ultrasound 115 track and field athletes. First, we marked on patient's skin the area to be examined both on the injured leg and on the healthy one. The patients were asked to report immediately any painful sensation. We used an ultrasound probe of 1 MHz, with a diameter of 3 cm and maximum intensity of 2.00 W/cm2. We scanned the questioned area in order to spot the point of major symptoms for 30 s. In case of negative findings after a total time of 60 s the procedure was completed. If there was a positive finding of intense pain, we reduced the power density and we continued for another 30 s. We continued in the same pattern until the patient reported no discomfort.
The estimated sensitivity and specificity of this procedure was 94, 39% and 62, 5%, respectively.
The mechanical energy when radiated from a source is mainly converted to heat. According to the literature, this ultrasound procedure highly elevates the temperature in periosteum. This increase of temperature is related to high transmission velocity and high absorption factor of the ultrasound.
The interpretation of the patients' sensation is the key to diagnosis. Sensation of heat, either light heat or burning, vibration, or a pinching ache, did not indicate a positive result of the ultrasound test in contrast to intense pain or pressure. It was the latter that led us to imply the existence of stress fracture.
The ultrasound technique for stress fracture detection is a safe, non-invasive, low cost method easily performed and could be a valuable tool for the physician's regarding decision making in terms of an early diagnosis.
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