[Imaging Manifestations of Stress/Fatigue Fractures] [Medical Imaging]

Author: Bow Wang, M.D.

Mr. H, a 14-year-old table tennis player, had been undergoing high-intensity training and competitions for a long time. Recently, he experienced severe pain in the proximal lateral aspect of his right lower leg, near the knee. He consulted with National Cheng Kung University Hospital [Interventional Medical Center] [Bow Wang, M.D.]. X-ray examination revealed no obvious fracture in the proximal lateral tibia, but there was localized bone sclerosis and whitening (left red circle in the image above). Further examination with magnetic resonance imaging (MRI) was arranged by Bow Wang, M.D.. Under T2WI/FS, localized bone marrow edema with a linear fracture line was found (right red circle in the image above). Bow Wang, M.D. diagnosed him with a stress fracture and referred him to a clinician for follow-up education, treatment, and rehabilitation.

The images above, from left to right, show the X-ray findings of a stress fracture of the proximal second toe. The left image shows that the initial X-ray of the pain did not reveal a clear bone fracture. Follow-up X-rays one month after injury (center image) and three months after injury (right image) revealed the gradual formation of callus (circled in red in the center and right images), leading to a diagnosis of a stress fracture. According to literature, X-ray examination has extremely low sensitivity for detecting early-stage stress fractures, only 15%-35%, while its sensitivity for detecting late-stage fractures is 30%-70%. The magnetic resonance imaging (MRI) (MRI) has a higher detection sensitivity, reaching 95-100%. The ultrasound also has the capability and role to detect small fractures in specific locations.

Ref: https://radiologyassistant.nl/musculoskeletal/unsorted/stress-fractures

Early magnetic resonance imaging (MRI) (MRI) images of fatigue/stress fractures, including periosteal edema and medullary edema. As the injury becomes more severe, edema can be seen to increase, and in the most severe cases, a linear fracture line can be seen on MRI images. computed tomography (CT) (CT) is not considered a first- or second-line imaging modality for the diagnostic evaluation of suspected stress injury; however, CT may play a specific role when MRI results are inconclusive. Ref: Nattiv, A., et al. (2013). Correlation of MRI grading of bone stress injuries with clinical risk factors and return to play: a 5-year prospective study in collegiate track and field athletes. Am J Sports Med, 41(8), 1930-1941.

Stress fractures can be classified as low-risk or high-risk. This risk classification helps assess the treatment required and predict the time needed for patients to regain their athletic ability (return to competition). Generally, stress fractures caused by compressive stress are considered low-risk and can be healed through activity regulation and reduced weight-bearing. In contrast, fractures caused by tensile stress, especially in areas with insufficient blood supply, are considered high-risk, leading to delayed healing and potentially progressing to complete fractures.Ref : Marshall, R. A., et al. (2018). Imaging Features and Management of Stress, Atypical, and Pathologic Fractures. RadioGraphics, 38(7), 2173-2192

The most common low-risk stress fractures include the posteromedial tibia, calcaneus, third and fourth metatarsals, and medial femoral neck. High-risk stress fractures include the superior lateral femoral neck, patella, anterior tibial cortex, medial malleolus, talus neck, dorsal scaphoid cortex, proximal metaphysis of the fifth metatarsal, and the big toe recess. These fractures may require more aggressive management, including prolonged recovery, reduced local weight-bearing, and in the most severe cases, surgical intervention may be necessary. Ref: McInnis, K. C., et al. (2016). High-Risk Stress Fractures: Diagnosis and Management. Pm r, 8(3 Suppl), S113-124.