Medial Tibial Stress Syndrome, also known as “shin splints”, is an early stage in the continuum that culminates in a stress fracture. The pain is typically posteromedial soreness and the diagnosis is usually made clinically without the need for further imaging assessment. On a microscopic level, repetitive stress leads to osteoclastic resorption exceeding osteoblastic bone regeneration. The associated edema along the periosteum and endosteum of the bone is visible on MRI. Periostitis may be directly caused by traction at muscle or fascial attachments, or may be a response to developing changes in the underlying bone. The relative roles of compressive versus torsional forces in the development of Medial Tibial Stress Syndrome and ultimately stress fractures, has been debated. Recent work appears to favor the latter. Compressive forces account for the transverse, often subchondral, stress fractures in the proximal tibia. Torsional forces may be of greater significance in the tibial shaft, and may account for the higher number of longitudinal fractures.
Clinical histories in patients with stress fractures may be atypical. This case for example had history of pain and was being labelled as normal or non-specific. Clues to the MRI diagnosis of longitudinal fracture of the tibial shaft include edema distribution along the endosteum and periosteum of one cortex, most often posteriorly or anteromedially. The axial images are frequently diagnostic, demonstrating a linear lucency on multiple sequential images, and often endosteal and periosteal callus formation. The sagittal or coronal sequences are helpful in demonstrating the length of involvement and the site of greatest edema, which indicates the most likely fracture site. A fracture line is occasionally visible on the coronal or sagittal sequences, depending on fortuitous positioning of the image slice relative to the affected cortex. MRI is well suited for distinguishing between stress fractures and pathologic fractures. Well-demarcated T1 signal abnormality, endosteal scalloping, and an adjacent soft tissue mass are each indicators of neoplasm rather than stress fracture.
Clinical histories in patients with stress fractures may be atypical. This case for example had history of pain and was being labelled as normal or non-specific. Clues to the MRI diagnosis of longitudinal fracture of the tibial shaft include edema distribution along the endosteum and periosteum of one cortex, most often posteriorly or anteromedially. The axial images are frequently diagnostic, demonstrating a linear lucency on multiple sequential images, and often endosteal and periosteal callus formation. The sagittal or coronal sequences are helpful in demonstrating the length of involvement and the site of greatest edema, which indicates the most likely fracture site. A fracture line is occasionally visible on the coronal or sagittal sequences, depending on fortuitous positioning of the image slice relative to the affected cortex. MRI is well suited for distinguishing between stress fractures and pathologic fractures. Well-demarcated T1 signal abnormality, endosteal scalloping, and an adjacent soft tissue mass are each indicators of neoplasm rather than stress fracture.
Dr.Sumer K Sethi, MD
Sr Consultant Radiologist ,VIMHANS and CEO-Teleradiology Providers
Editor-in-chief, The Internet Journal of Radiology
Director, DAMS (Delhi Academy of Medical Sciences)
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