We measured intramuscular oxygenation in the anterior tibial muscle of 176 patients with exercise-induced leg pain by noninvasive near-infrared spectroscopy before, during, and after an exercise test that elicited the symptoms. Clinical investigation was performed after each test. Intramuscular pressure was measured in patients with nonconclusive findings. Chronic anterior compartment syndrome (CACS) was diagnosed in 47 patients, and other causes for the leg pain were diagnosed in 129 patients by clinical means. The mean level of oxygenation decreased to 33 ± 19% in patients with CACS and to 34 ± 19% in patients without CACS compared with baseline level (100%) at rest before exercise. The level of oxygenation was below 20% during the exercise test in 12 of 47 (26%) patients with CACS and in 30 of 129 (23%) patients without CACS. The time required for reoxygenation after the cessation of exercise was 61 ± 34 s in patients with CACS and 46 ± 20 s in patients without CACS (P < 0.05). We conclude that the magnitude of intramuscular deoxygenation during exercise is an unreliable measure to diagnose CACS. However, the time for reoxygenation returning to baseline level following an exercise test is a valuable adjunct in diagnosing CACS.

IntroductionClassifying symptoms by patient pain drawing (PPD) may be helpful in diagnosing chronic anterior compartment syndrome (CACS). We have investigated the sensitivity and interobserver reliability of the PPD to diagnose CACS among patients with exercise-induced leg pain (EILP).MethodsThis study included 88 consecutive patients (48 men, 40 women; mean age 33, range 13–66, years). Two observers independently diagnosed the causes of leg pain based solely on PPD. The causes of leg pain in patients were diagnosed into seven categories (CACS, chronic lateral compartment syndrome, chronic posterior compartment syndrome, medial tibial syndrome, peroneal tunnel syndrome, muscle rupture and miscellaneous). The true diagnosis was based on a complete clinical examination including laboratory measurements of intramuscular pressure and intramuscular oxygenation by near-infrared spectroscopy during and after an exercise test that elicited the symptoms.ResultsThe sensitivity of PPD to diagnose CACS was 69%. The positive predictive value was 53%. The interobserver reliability based solely on PPD in diagnosis of CACS was 92% (κ=0.81). Based on PPD, the causes of EILP were correctly diagnosed into the seven categories in 69% of all cases. The interobserver reliability in diagnosis of EILP reached 88%. Multiple pain locations on PPD were observed in 4% of patients with CACS and 24% of patients without CACS. No patient had chronic compartment syndrome in the lateral or posterior compartments.ConclusionsThis study indicates that PPD is a reliable tool to make accurate predictions in diagnosing CACS and other causes of EILP. Patients with CACS reported significantly less co-morbidity compared to patients with other causes of EILP. PPD should be combined with patient's history, clinical findings during an exercise test that elicits the symptoms and signs, as well as with the results from laboratory tests.