A 27-year-old woman who presents with 2 months of bilateral lower leg pain. Her pain is induced by exercise and usually resolves with rest, although recently it has become persistent.
Initial radiographs of the left tibia and fibula:
Initial radiographs did not demonstrate any abnormality. The patient then underwent a Tc99m MDP bone scan:
This was followed by an MRI:
The Tc99m MDP bone scan demonstrates linear increased uptake along the anteromedial tibia bilaterally, with several more focal areas of increased uptake, in the right mid tibia and left distal tibia.
MR images demonstrate edema signal within the left greater than right subcutaneous tissue, tibial periosteum, and tibial bone marrow/cancellous bone. In addition there are subtle foci of edema signal with the medial cortex of the left distal tibia, suspicious for early stress fracture.
Medial tibial stress syndrome (or “shin splints”) and tibial stress fracture constitute a spectrum of injuries related to excessive or repetitive exertion, often seen in runners. Further questioning of this patient revealed her symptoms began several weeks after she walked 60 miles in one weekend as part of a fundraiser.
The distinction is important because while shin splints may be treated with decrease in exertion, a stress fracture requires a period of non-weight bearing or immobility (e.g. use of a walking boot or crutches) to enable healing.
Shin splints is seen on bone scan as a linear mild-moderate increased uptake, classically along the posteromedial tibia and extending at least one third the length of the bone. A stress fracture is seen as a focal or fusiform region of moderate-intense uptake, with the most common location being the junction of the middle and distal thirds of the tibia. Stress fractures will also have increased blood flow and blood pool activity on a 3-phase bone scan. Rupani HD, et al. Three-phase radionuclide bone imaging in sports medicine. Radiology 1985;156:187-96.
MRI demonstrates a spectrum of tibial stress reaction, with the most severe injuries denoted by linear edema signal with the tibial cortex. These patients require a significantly longer time to return to activity. Kijowski R, et al. Validation of MRI classification for tibial stress injuries. AJR 2012;198:878-84.