Correlation Between Sonographic and Pathologic Findings in Muscle Injury: Experimental Study in the Rabbit

Objective: To evaluate the serial sonographic findings of experimental muscle injury and to correlate those findings with the pathologic findings at each period.

Methods: A muscle injury was artificially inflicted in 18 legs of 9 rabbits. Sonographic follow-up images were obtained 1, 3, and 7 days and 2, 3, 4, 6, and 8 weeks after infliction of muscle injury. Pathologic specimens were obtained for comparison with sonographic findings on each date.

Results: There was high echogenicity in the central portion after 3 days. It changed to low echogenicity after 7 days. There were linear echogenic lines in the central portion after 4 weeks, and these lines increased in number after 6 weeks. The peripheral portion exhibited high echogenicity up to 7 days. This high echogenicity was normalized after 2 weeks. Pathologic specimens showed hematomas, fibrin, and necrotic muscle fibers in the central portion up to 3 days after injury. Fibrin occupied most of the central portion after 2 weeks. Regenerating muscle fibers appeared within the fibrin clot after 4 weeks, and they became more prominent after 6 weeks. Necrotic muscle fibers, hemorrhage, and inflammatory cells of the peripheral portion disappeared after 2 weeks.

Conclusions: Serial sonography of muscle injury was well correlated with the pathologic specimen up to 7 days after injury. After 4 weeks, regenerating muscle fibers showed a good correlation with the finding on sonography. Therefore, sonography can be helpful in diagnosis of muscle injury as well as in evaluation of the regenerating muscle fibers.