Presentation
Left mid-foot pain, worse on mobilizing. No history of trauma.
Patient Data
On blood flow images, there is mildly increased blood flow to the left foot compared to the right. On blood pool images, there is focal hyperemia in the left foot, in the region of the distal metatarsals.
On delayed phase planar imaging, there is focal intense tracer accumulation in the left distal 2nd metatarsal bone. This is confirmed on the 3D volume rendered reconstruction of the SPECT/CT data. Given the pattern uptake and clinical history, findings are in keeping with a stress fracture of the left 2nd metatarsal.
Elsewhere in the feet and ankles, there is mild-moderately increased periarticular uptake in both ankles, subtalar joints and mid-feet in keeping with osteoarthritis. On review of the whole body planar image, there is further evidence of osteoarthritis in both knees, the left hip, wrists and hands and the acromioclavicular joints.
Case Discussion
On bone scan, stress fractures are typically seen as 'three phase positive' with increased blood flow and hyperemia to the affected area on early phase imaging, and focal intense increased tracer accumulation (osteoblastic activity) on the delayed phase imaging. The underlying anatomical imaging may be normal, however SPECT/CT is very useful in accurately localizing the abnormality. In this case, the focal uptake of tracer in the distal shaft/metadiaphysis of the 2nd metatarsal was diagnostic of a stress fracture. In contrast, if the uptake was periarticular in location (especially if abnormal uptake was present on both sides of the joint), a diagnosis of active arthritis would have been more likely.