The "muscular hernia sign": an original ultrasonographic sign to detect lesions of the forearm's interosseous membrane.

The total disruption of the forearm's interosseous membrane can lead to an Essex-Lopresti syndrome. The diagnosis must be done early for a better prognostic. Incomplete lesions can aggravate and an early diagnosis of incomplete lesions is a challenging problem. Magnetic resonance imaging is the gold standard but remains expensive, and is hard to obtain in an emergency. On the contrary, ultrasonography is cheap, accessible in an emergency, and dynamical tests can be performed easily. Twelve fresh frozen forearms were randomized in four groups. The membrane was divided into three parts (proximal, middle, and distal thirds). Each group was prepared with variable patterns of lesions. Two radiologists performed an ultrasonographic (US) examination of these forearms. They were blinded with respect to the lesional status of the forearms. Each examination consisted of two stages: static and dynamic. During the dynamic examination, the radiologist looked for the "muscular hernia sign". The results of their examinations were compared with the real lesional status. The static examination was very efficient in the proximal and middle parts of the membrane, and less reliable in the distal third. With the dynamical examination, no mistake occurred at the proximal and middle parts of the forearm, and there was only one at the distal part. The US examination of the interosseous membrane is very efficient to detect incomplete lesions, mostly, if dynamical tests are performed looking for a "muscular hernia sign".