Anatomic basis for implantation of the Ilizarov system in the leg.

Ilizarov's method of implanting an external circular fixator requires the placement of at least 8 transfixion pins. The neurovascular hazards and the need to leave the posterior and lateral compartments free motivated this study, based on serial radiographic sections after injection of the entire arterial system. Two reference pin-planes were determined, 1 posterolateral and 1 lateromedial. The sites of insertion of the pins rely on classical radiographs of the bones of the leg. The addition of beaded pins must be made on a realigned and stabilized limb. The imprecision of aim due to the bone structure and the shape of the pin leads to the definition of forbidden zones where any transfixion is dangerous. The concept of a neurovascular pyramid with its base at the distal metaphysis and of a periosseous tendinous circlet at that level implies a search for a compromise between the stability of the assembly and the dangers of the method.