Bone stress injuries of the ankle and foot: an 86-month magnetic resonance imaging-based study of physically active young adults.

Background: No comprehensive studies of bone stress injuries in the ankle and foot based on magnetic resonance imaging findings have been published.

Purpose: Using magnetic resonance imaging findings to assess incidence, location, and type of bone stress injuries of the ankle and foot in military conscripts with ankle and/or foot pain.

Study Design: Case series; Level of evidence, 4.

Methods: All patients with ankle or foot pain, negative findings on plain radiography, and magnetic resonance images obtained of the ankle or foot were included in this 86-month study. Magnetic resonance images with bone stress injury findings were re-evaluated regarding location and injury type. Based on the number of conscripts within the hospital catchment area, the person-based incidence of bone stress injuries was calculated.

Results: One hundred thirty-one conscripts displayed 378 bone stress injuries in 142 ankles and feet imaged, the incidence being 126 per 100 000 person-years. This incidence represents the stress injuries not diagnosable with radiographs and requiring magnetic resonance images. Of injuries, 57.7% occurred in the tarsal and 35.7% in the metatarsal bones. Multiple bone stress injuries in 1 foot were found in 63% of the cases. The calcaneus and fifth metatarsal bone were usually affected alone. Injuries to the other bones of the foot were usually associated with at least 1 other stress injury. The talus and calcaneus were the most commonly affected single bones. High-grade bone stress injury (grade IV-V) with a fracture line on magnetic resonance images occurred in 12% (talus, calcaneus), and low-grade injury (grade I-III) presented only as edema in 88% of the cases.

Conclusion: Multiple, various-stage bone stress injuries of the ankle and foot may occur simultaneously in physically active young adults. When considering injuries that were missed by plain radiographs but detected by magnetic resonance imaging, the bones most often affected were the tarsal bones, of which the talus and calcaneus were the most prominent single bones and most common locations for higher grade (IV-V) bone stress injuries. With use of magnetic resonance imaging, early detection and grading of bone stress injuries are available, which enable early and appropriate injury management.