Presentation
Avid runner with severe right foot pain. Initial x-rays showed mid foot soft tissue swelling without acute bony abnormality.
Patient Data
Lower body bone scan performed 3 hours following the administration of 15 mCi of Tc99m-MDP IV.
Abnormal focal, intense radiotracer uptake is present in the right mid-foot, region of the navicular bone.
Less intense areas of increased radiotracer are present elsewhere in the bones of the right greater than left feet representing low grade stress injuries.
Non contrast MRI of the right foot shows intense edema in the navicular bone with an underlying T1/T2 dark fracture line.
Less intense areas of bone marrow edema are present in the talus, cuneiforms, and bases of the metatarsals representing low grade stress injuries.
Case Discussion
Bone scintigraphy is much more sensitive than radiographs for the diagnoses of stress fractures with greater than 80% of stress fractures being occult on initial x-rays.
On bone scintigraphy, focal increased uptake, in the appropriate clinical context, is consistent with a bone stress fracture. When it is intense and extends transcortical (as in this case) it is a grade 4.
MRI will show marrow edema, and when severe, a dark fracture line is present (as in this case).
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