[Implanting an osteosynthesis screw in the first sacral vertebra].

An original screwing technique is presented for the first sacral vertebra. A pediculocorporal position is proposed based on anatomical and experimental studies. The screw is placed obliquely medially in the horizontal plane, with the tip, in the sagittal plane, coming just under the first sacral end-plate which can be perforated in cases when a definitive implant for arthrodesis needs to be particularly solid.