Medial tibial stress syndrome (MTSS), also known as shin splints, describes a spectrum of exercise-induced stress injury that occurs at the medial tibial mid-to-distal shaft. This term is often incorrectly used to indicate any type of tibial stress injury but more correctly refers to the earlier manifestations of a tibial stress lesion before a fracture component can be identified 1.
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Epidemiology
Medial tibial stress syndrome typically occurs in runners and other athletes that are exposed to intensive weight-bearing activities such as jumpers.
Clinical presentation
Medial tibial stress syndrome is characterized by localized pain that occurs during exercise at the medial surface of the distal two-thirds of the tibial shaft.
A "one-leg hop test" is a functional test, that can be used to distinguish between medial tibial stress syndrome and a stress fracture: a patient with medial tibial stress syndrome can hop at least 10 times on the affected leg whereas a patient with a stress fracture cannot hop without severe pain 2.
Radiographic features
Plain radiograph
For medial tibial stress syndrome, plain radiographs are considered insensitive and are often normal. It may, however, demonstrate subtle periosteal reaction or callus around the cortex of the tibia medially 11.
CT
CT is not particularly sensitive for medial tibial stress syndrome (~40%) 3. It may reveal mild osteopenia as an early sign of fatigue damage of cortical bone in tibial diaphysis 3,4.
Ultrasound
Medial tibial stress syndrome may show focal hyperechoic elevation of the periosteum with irregularity over the distal tibia and increased flow on Doppler interrogation.
MRI
MRI is the most sensitive radiological examination (~88%) for medial tibial stress syndrome 3. It may demonstrate a spectrum of findings ranging from normal to periosteal fluid and marrow edema in medial tibial stress syndrome to a complete stress fracture 5. The medial cortex (+/- posterior cortex) is most commonly affected 3. The axial fluid-sensitive, fat-saturated sequences are often the most helpful.
Early stages
- periosteal edema: may be very subtle and noticeable in early stages, only on fluid-sensitive sequences (STIR, fat-suppressed T2- and PD)
- bone marrow edema: usually accompanied by periosteal edema at similar level as periosteal edema but usually on a shorter segment 14
Later stages
- bone remodeling: caused by osteoclast-mediated resorption and osteoblastic replacement and leads to changes in cortex
- normal cortex has
- T1: low signal intensity
- T2: low signal intensity
- normal cortex has
- osteopenia:
- defined as loss of cortical signal void (MRI); resorption cavity is a round or oval intracortical area of increased signal intensity (MRI)
- striation: may be seen as subtle intracortical linear hyperintensity
Classification
The Fredericson grading system can be used to grade the MRI findings with a good correlation with clinical severity and outcome 7,8.
Nuclear medicine
Bone scintigraphy is relatively sensitive (~75%) 3 and may demonstrate high uptake in the affected region, characteristically along the posteromedial tibial aspect on lateral views. On the 3-phase isotope bone scan there will be typically normal appearances on the arterial and blood pool phases but longitudinal uptake on the delayed images. (cf. stress fracture which will show early phase uptake).
Treatment and prognosis
- medial tibial stress syndrome patients can continue running at reduced levels
- it might progress to stress fractures
- stress fractures are managed by removing the causative activity
Related pathology
- tibial stress fracture: there can be some overlap depending on the definition
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