Change of shear modulus of healthy lower-leg muscles after treadmill running: towards a non-invasive diagnosis of chronic exertional compartment syndrome

Chronic exertional compartment syndrome (CECS) is an exercise-induced condition, in which high pressure develops in one or several lower leg compartments, resulting in pain, numbness, and temporary muscle paresis. Diagnosis of CECS is assisted by measurements of intracompartment pressures (ICP) at rest, 1-min and 5-min after cessation of running exercise (Pedowitz criteria). ICP is measured via needle manometry, which is an invasive procedure. We have recently shown that intramuscular pressure is correlated to shear modulus measured via shear wave elastography (SWE) (Spearman's correlation coefficient = 0.99). The objectives of this study were to quantify temporal changes in shear modulus of muscle in lower leg compartments of healthy individuals before and after running exercise, and to evaluate a Pedowitz-like criterion for diagnosis of CECS using muscle shear modulus as biomarker. Specifically, the shear modulus of the tibialis anterior (TA) and peroneus longus (PL) was measured at time intervals of 1 min for 10 min after cessation of exercise. The shear modulus of the TA, PL, Soleus and Tibialis posterior were also measured bilaterally before, and at 1- and 5-min after exercise in a procedure that resembles the Pedowitz test for ICP. The shear modulus of all compartments increased significantly in both legs 1-min postexercise and gradually decreased to prerunning values. 50% of such decrease occurred at between 3 and 5 min after cessation of exercise. Additionally, the change in shear modulus followed a similar pattern than ICP in the Pedowitz-like protocol. Therefore, SWE has the potential to diagnose CECS noninvasively.