[Lateral approach to blockade of the sciatic nerve. Biometric data using magnetic resonance imaging].

In the present study we examined 41 volunteers using magnetic resonance imaging to obtain biometric data of the thigh used for a planned blockade of the sciatic nerve via the lateral approach. At a needle entry point 12 cm proximal to the gap of the knee joint at the posterior border of the M. vastus lateralis, the sciatic nerve lies on average at a depth of 5.2 cm (39% of the femoral diameter at this site) with an angle of 10.9 degrees to the horizontal in a dorsal direction. Here the popliteal artery lies on average at a depth of 6.4 cm (48% of the femoral diameter) with an angle of 4.7 degrees to the horizontal in a ventral direction. At the marked point in the middle between the gap of the knee joint and the trochanter major at the posterior border of the M. vastus lateralis, the sciatic nerve is at an average depth of 6.2 cm (40% of the femoral diameter at this site) with an angle of 8.2 degrees in a dorsal direction. At a marked point 5 cm distal of the trochanter major at the posterior border of the M. vastus lateralis, the sciatic nerve is at a depth of 9.1 cm at a dorsal angle of 15.5 degrees (49% of the femoral diameter). The lateral blockade of the sciatic nerve at different sites of the thigh is a technique which is easy to plan with the presented biometric data. The popliteal artery could be reached only at the distal puncture point using a deep puncture and an angle in the ventral direction.