Abstract: The invention relates to an osteosynthesis aid for treating upper arm fractures close to the head with an elastically derformable helical wire which is inserted laterally into the medullary space. The helical wire consists e.g. of implant steel wire and is configured as a self-cutting helical spring. The wire is characterized in that it is reversibly deformable in the longitudinal direction by up to 90° over its entire length, for its lateral insertion into the medullary space. The helix becomes elastically braced, forming a three-point brace as it is deformed in the medullary space, and bores itself further into the spongiose bone of the head of humerus. The shape of the osteosynthesis aid advantageously enables the treatment of fractures in oestoporotically altered bone and is also characterized in that the cross-section of the helical spring is triangular, rhomibic or round.