MRI findings in chronic exertional compartment syndrome of the forearm: Using signal intensity ratio as a diagnostic tool

Background: Chronic exertional compartment syndrome (CECS) of the forearm is a rare but important cause of morbidity amongst athletes involved in strenuous upper limb activities. The diagnosis remains challenging due to the absence of objective, reproducible diagnostic studies. Objectives: To assess and quantify signal intensity (SI) changes of involved muscles in patients with CECS of the forearm compared to healthy control subjects competing in similar sporting disciplines. Also, to objectively measure MRI SIs within muscle compartments when using a pre- and post-exercise regime and calculating a signal intensity ratio (SIR) between post- and pre-exercise studies. Method: The study retrospectively examined MRI scans of patients treated for CECS of the forearm and compared these to the MRI scans of asymptomatic high-level rowers. A specific, reproducible pre- and post-exercise MRI scanning protocol was utilised in both patient and control subjects between 2011 and 2020. Signal intensities were evaluated pre- and post-exercise in involved muscle groups and ratios were calculated. Results: A total of 86 SIs were measured (43 pre- and 43 post-exercise) in nine study participants (five patients and four controls). After post:pre-exercise comparisons, a statistically significant difference was found between control and patient groups (p = 0.0010). The extensor carpi radialis, flexor digitorum profundus and flexor digitorum superficialis muscles were most commonly involved. Conclusion: This study confirms that significant SI changes are apparent in patients with CECS of the forearm when making use of a standardised pre- and post-exercise MRI protocol. Furthermore, SIR may be used to accurately diagnose CECS of the forearm.