20 y.o. track athlete with several weeks of bilateral lower leg
pain. Lower leg radiographs appeared normal.
Bilateral shin splints with two possible early focal stress
fractures of the right tibia.
#1 - Tc99m MDP Radionuclide angiogram of the lower legs
demonstrates no definite areas of hyperemia. #2 - Blood pool phase
of the bone scan of the lower legs demonstrates no definite
abnormal areas of radiotracer localization #3 & #4 Delayed
images demonstrate linear uptake along the posteromedial
mid-to-distal tibias, right more extensive than left. At the most
cephalad and caudal aspects of the abnormality in the right tibia
there are more fusiform areas of increased tracer uptake involving
The term shin splints describes a combination of clinical and
scintigraphic findings. Patients complain of exercise-induced pain
along the medial or posteromedial aspect of the tibia. Frequently
these symptoms are bilateral and can be asymmetric. Shin splints
are believed to result from focal periostitis, microperiosteal
tears at points of periosteal stress, at the insertion of the
soleus muscle and its fascia. This fascia envelopes the soleus
muscle and extends along the posterior medial border of the tibia.
Scintigraphically this appears as mild to moderate radiotracer
uptake, often of varying intensities, along the posteromedial
aspect of the middle to distal tibia, involving at least one third
of the bone. A more focal component to the uptake can predict
further injury if the causative stress persists. Stress fractures
in this region occur predominantly at the middle third-lower third
junction of the tibia in the posteromedial cortex. Focal, fusiform
increased radiotracer localization on delayed images is the classic
finding. Intense hyperemia on the radionuclide angiogram and blood
pool phase can help distinguish stress fractures from shin splints,
which typically have normal radionuclide angiogram and blood pool
uptake. Stress fractures occur when resorption of bone outpaces
replacement during remodeling secondary to the increased activity.
It is a continuum of injury spanning an early remodeling reaction
to an overt fracture. A four-grade scintigraphic classification can
be applied. Grade I lesions show an ill-defined cortical increase
in uptake. Grade II lesions are larger, more well-defined, and
demonstrate moderate increased activity. Grade III lesions have a
wide fusiform corticomedullary region of activity, and Grade IV
lesions demonstrate an extensive transmedullary region of increased
uptake. In this case, the more focal areas of tracer uptake in the
right tibia were concerning for an early stress fracture, low
grade, in this athlete. Demonstration of hyperemia on the
angiographic and blood pool phases would have made the diagnosis of
concurrent stress fractures definitive.
Skeletal Nuclear Medicine, Collier Jr., Fogelman, Rosenthall.
Essentials of Nuclear Medicine Imaging, 4th edition, Mettler and