[The "3-in-1" block: myth or reality?].

The technique described by Winnie in 1973 is supposed to provide a regional block of the femoral, femoral cutaneous, and obturator nerves by a single injection within the femoral nerve sheath. This study aimed to assess the diffusion spaces for the local anaesthetic solution used in this technique. The anatomical study included the dissection of 2 adult and 1 foetal cadavers. It was associated with a radiographic study in adult volunteers. About 20 to 60 ml of an isotonic radiographic contrast (iopamidol 150) were injected into the femoral nerve sheath located with the help of a nerve stimulator. Standard pelvic radiographs and computerised tomographic scans were carried out at the time of injection, and 30 min later. Two different unpredictable distributions were found; which were independent of the injected volume. One type consisted in an internal diffusion towards the psoas major muscle, the liquid thus reaching the three nerves. The other type was an external diffusion, in front of the iliacus muscle, the liquid never reaching the internal side of the psoas major muscle, and therefore the obturator nerve. The "3 in 1" block would therefore seem to be useful for those surgical acts requiring only a block of the femoral and femoral cutaneous nerves, i.e. those involving the anterior aspect of the thigh and knee, the femoral shaft, and the patella. On the other hand, its usefulness for surgery of the hip (dislocation, fractured neck of femur) is rather uncertain.