LAS VEGAS — Imaging techniques can help to confirm stress fractures and distinguish them from other conditions, Dr. Christopher Beaulieu said at a symposium on emergency medicine sponsored by Stanford University.
“I don't call it a stress fracture unless I can point to the fracture line on the image, otherwise [it is] a stress reaction or stress response,” said Dr. Beaulieu of Stanford (Calif.) University. A stress reaction or response can be diagnosed if MR or other imaging shows periosteal or marrow edema without a fracture line.
If a stress fracture is confirmed, the patient must take time off from the offending activity to allow the bone to heal, but if a fracture has not occurred, the patient may be able to continue activities with modifications to prevent a full fracture.
Stress injuries to bone occur when the skeleton is unable to withstand submaximal forces acting over time, and they fall into two categories: stress (or fatigue) fractures and insufficiency fractures. Stress fractures occur when normal bones are subjected to abnormal forces, and they are common in new athletes and in military recruits. Insufficiency fractures occur when abnormal bones can't sustain normal forces, and they occur primarily in patients with bone conditions such as osteoporosis or Paget's disease.
A clinical history of overuse is the key to a stress fracture diagnosis. Risk factors for stress fractures include increased mileage, running on a hard surface, and a poor choice of shoes. Biomechanics and bone mineral density also contribute to stress fractures, as do female gender, amenorrhea, and poor nutrition or eating disorders.
To maximize the imaging of a possible stress fracture, use local coils and high quality T2-weighted imaging, Dr. Beaulieu said. “A high-quality localized image, a negative scan almost entirely excludes a significant bony stress injury.” A fat suppression image also helps in identifying a stress fracture.
MRI of a stress fracture in a runner shows a low-signal fracture line (red arrows).
MRI with fat suppression shows edema around the low-signal fracture. Photos courtesy Dr. Christopher Beaulieu