[Ultrasonographic evaluation of the sciatic nerve and thigh trauma].

This study was aimed at studying the normal morphology of the main extrapelvic trunk of the sciatic nerve, its average size and its anatomo-topographic relationships by means of high resolution US. The involvement of the sciatic nerve in traumas was also investigated. The lower gluteal region and the posterior aspect of both thighs were examined in 30 healthy subjects and in 11 patients with recent or previous traumas. The sciatic nerve is clearly demonstrated, on US images, between the biceps femoris muscle and the semimembranosus and semitendinosus muscles. The average dorsoventral diameter of the nerve is 6.4 mm at the upper third and 4.8 mm at the middle third of the thigh, while its average transverse diameter is 11.8 mm at the middle third of the thigh. In traumas, US demonstrated compression and displacement of the sciatic nerve in 6 recent hematomas and in 2 hypertrophic ossei calli of the femoral diaphysis. In 2 osteomyelitis cases with a posterior thigh fistula, US showed sciatic nerve involvement by the phlogistic process. Moreover, US allowed an old thick thrombosis of a satellite vein of the sciatic nerve to be depicted. In conclusion, the present study has demonstrated that US not only clearly depicts the sciatic nerve but also provides accurate information on its involvement in recent or previous traumas.