The purpose of the present invention is a new implant for medical use enabling the fixation of at least two adjacent bone elements in a rapid, secure and minimally invasive manner. Said implant is a device in two distinct parts forming a screw once said two parts are assembled. The present invention describes also a fixing method of at least two adjacent bone elements implementing said new implant forming a screw. Said method is particularly adapted for joining at least two vertebrae in order to achieve an arthrodesis; said implant forming a screw is then of a curved shape that makes it particularly well adapted for the spine surgery.