MRI accurately detects chronic exertional compartment syndrome: a validation study

To validate the diagnostic performance of an in-scanner exercise-based magnetic resonance imaging (MRI) examination used to screen for chronic exertional compartment syndrome (CECS). Final clinical impression and intracompartmental needle manometry (INM) served as the reference standards. Consecutive patients, referred by a sports medicine physician or orthopedic surgeon, underwent the MRI examination for lower extremity pain over the past 4 years and 9 months. Utilizing a diagnostic T2-weighted intensity ratio threshold of 1.54, established by a prior cohort of patients, sensitivity, specificity, predictive value, and diagnostic odds ratio were calculated for the anterior compartments. The means of the T2-weighted intensity ratios were compared using the Wilcoxon rank sum test. A total of 79 patients were identified, and 76 met the inclusion criteria and were evaluated. Of these, 23 met clinical diagnostic criteria. Sensitivity and specificity were 96% (95% CI: 79–99%) and 87% (95% CI: 75–94%) using the established threshold of 1.54. T2-weighted intensity ratio provided excellent discrimination with a concordance statistic of 0.96 (95% CI: 0.91–1.00). In the subset of 36 patients with INM results, 23 patients met criteria for CECS, although only 19 patients met both INM and clinical criteria. The sensitivity and specificity of the MRI examination relative to INM results were 87% (95%: 70–96%) and 62% (95% CI: 36–82%) respectively. In-scanner exercise-based MRI demonstrated reliability and reproducibility as a non-invasive screening test for CECS, thus reducing the need for invasive INM.