Chronic Exertional Compartment Syndrome: Noninvasive Diagnosis with MRI
Abstract & Commentary
Synopsis: A prospective study was performed to determine if MRI signal intensity changes within the anterior compartment allow accurate diagnosis of chronic exertional compartment syndrome. This study reported a statistically significant difference in T2 signal intensity changes of the affected anterior compartment compared to the uninvolved superficial posterior compartment. These findings suggest that MRI allows noninvasive diagnosis of chronic compartment syndrome in selected patients.
Source: Verleisdonk EJ, et al. Skeletal Radiol. 2001;30: 321-325.
This prospective study evaluated MRI for the noninvasive diagnosis of chronic exertional compartment syndrome. The study group consisted of 21 patients with elevated postexercise intramuscular pressure within the anterior compartment of at least 50 mm Hg (average, 61 mm Hg). The control group included 12 subjects with normal postexercise intramuscular pressure within the anterior compartment (average, 19 mm Hg). In both groups, MRI was performed before and after exercise using a standardized protocol including axial spin echo T2-weighted images (TR 2400/TE 50-100 msec). All patients exercised for 10 minutes at 6.5 km/h on a treadmill with postexercise images performed within 1 minute of exercise. The T2 signal intensity was measured on pre and postexercise images by placing a region of interest (ROI) over the anterior and superficial posterior compartments.
The percent increase in average T2 signal intensity within the anterior compartment of symptomatic patients following exercise was 27.5% (13.6-38.6%) and was significantly greater than that of the superficial posterior compartment (4.25%; range, 0-10.2%). The signal intensity ratio of the anterior and superficial posterior compartments increased in the study group 20.5% (11.2-32.0%) following exercise, whereas in the control group this ratio increased only 3.9% (0-7.0%). Following fasciotomy, the signal intensity ratio of the 2 compartments increased by only 1.8% (0-8.0%) following exercise. These differences were found to be statistically significant. Resolution of symptoms after fasciotomy was used as a gold standard for the diagnosis of chronic exertional compartment syndrome. All 21 patients in the study group were free of symptoms at 3 months following surgery.
All study group patients had postexercise intramuscular pressure measurements in excess of 50 mm Hg to ensure that selected patients did have chronic exertional compartment syndrome. Verleisdonk and colleagues indicate the diagnosis of chronic exertional compartment syndrome is often made at lower postexercise pressures, and the role of MRI in such cases is unclear and deserves further investigation.
Comment by Robert C. Schenck, Jr., MD, Keir Fowler, MD, & Thomas Martin, MD
Chronic compartment syndrome (CCS) has been a recognized clinical syndrome for more than 4 decades. The diagnosis rests on appropriate clinical history and elevated intracompartmental pressures.1 Previous investigators have found MRI a useful adjunct in the diagnosis of CCS2 although not sufficient to replace invasive testing in all patients.
This prospective study suggests MRI plays an important role in the evaluation of lower extremity pain related to exercise. Although the exact pathophysiology of CCS is incompletely understood, long TR sequences (ie, T2- weighted images) reveal increased free water content within affected skeletal muscle seen as diffusely increased signal within the involved compartment. The current study offers a simple and reproducible methodology that can be readily performed on commercially available MR scanners.
The patient selection criteria used in this study, which included postexercise intramuscular pressures in excess of 50 mm Hg, produces a selection bias that would exaggerate the marked difference of T2 signal intensity changes between symptomatic patients and control subjects. Verleisdonk et al correctly state that CCS can occur in patients with intracompartmental pressures less than 50 mm Hg, and the role of MRI in this subset of patients is unclear. In patients with only moderately elevated intracompartmental pressure, the use of fluid sensitive MR sequences such as fast short tau inversion recovery (FSTIR) would likely be useful to identify subtle changes in compartmental water content. Further investigation is necessary to establish the utility of FSTIR sequences for diagnosis of chronic compartment syndrome.
Significant increases in the T2 signal intensity of anterior compartment skeletal muscle were found to normalize following fasciotomy. As such, MRI may be of benefit in patients with recurrent symptoms after successful surgery to evaluate for recurrent CCS.
Based on our experience, it is imperative to perform post-exercise imaging as soon as possible following cessation of exercise (less than 1 minute). The findings of Amendola and colleagues demonstrated rapid normalization of T1 and T2 relaxation characteristics within minutes of exercise cessation, underscoring the importance of rapid imaging after exercise.2 Although this may be problematic, the expanded diagnostic ability and avoiding pre- and post-exercise needle pressure measurements in all compartments suspected is a great advantage with MRI.
This study suggests a role for MRI in the evaluation of exercise-related lower extremity pain. MRI may obviate invasive diagnostic testing prior to fasciotomy in selected patients. Exertional compartment syndromes have been described elsewhere including the foot,3 and MRI maybe of value in these cases as well. Moreover, a tailored imaging protocol for exercise-related lower extremity pain would allow diagnosis of stress fractures, tibial stress reaction, and myofascial herniation, which have similar clinical presentations.
Dr. Schenck, Deputy Chairman, Department of Orthopaedics, University of Texas Health Science Center, San Antonio, is Associate Editor of Sports Medicine Reports. Dr. Fowler is a PGY-III resident in the Department of Radiology at the University of New Mexico School of Medicine. Dr. Martin is Associate Professor of Radiology at the University of New Mexico School of Medicine, Albuquerque, NM.
References
1. Pedowitz RA, et al. Am J Sports Med. 1990;18:35-40.
2. Amendola A, et al. Am J Sports Med. 1990;18:29-34.
3. Mollica MB, Duyshart SC. Am J Sports Med. 2002;30: 268-271.
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