Image Interpretation: The distal fibula has a focal area of cortical irregularity with hypoechoic periosteal elevation and nearby hyperemia on power doppler consistent with an early bone stress injury.
Teaching Pearl: Bone stress injuries are common overuse injuries seen in sports medicine clinics. Radiographs remain the mainstay first step in evaluation of these injuries however they are often normal appearing. Most often MRI or bone scintigraphy have been the imaging modality of choice to further evaluate these patients but it is now known that US can be used point-of-care to look for characteristic findings of early bone stress injury. The earliest findings are often hypoechoic periosteal elevation and hyperemia. Later cortical irregularity and thickening with callous formation and hyperechoic surrounding soft tissue secondary to edema can be present. Pain with sonopalpation often becomes a very important aspect to the evaluation as well (1). While case studies specific to fibula stress fractures diagnosed by sonography are limited it has been shown as
a tool that can be used to differentiate lower leg pain secondary from muscle injury compared to bone stress (2). References:
1) Hoffman DF, Adams E, Bianchi S. Ultrasonography of fractures in sports medicine. Br J Sports Med. 2015 Feb;49(3):152-60. doi: 10.1136/bjsports-2014-094217. Epub 2014 Dec 24. PMID: 25540189. 2) Hoglund LT, Silbernagel KG, Taweel NR. DISTAL FIBULAR STRESS FRACTURE IN A FEMALE RECREATIONAL RUNNER: A CASE REPORT WITH MUSCULOSKELETAL ULTRASOUND IMAGING FINDINGS. Int J Sports Phys Ther. 2015 Dec;10(7):1050-8. PMID: 26672683; PMCID: PMC4675190.