1. System with a length-adjustable pin for intramedullary osteosynthesis, comprising: a pin for intramedullary osteosynthesis, comprising: an external proximal element； a distal element, a portion of which is placed in the specified external proximal element； a threaded rod attached to the specified distal element with the possibility of rotation relative to the specified a distal element； an internal magnet inserted into said external proximal element and attached to said threaded rod； threaded insert ku attached to the specified external proximal element, and the threaded rod passes through the threaded insert so that the rotation of the specified internal magnet and the threaded rod leads to relative axial movement between a) the specified internal magnet, the threaded rod and the distal element and b) the specified external proximal element. 2. The system according to claim 1, in which the threaded rod is attached to the specified distal element with the provision of mutual fixation of the specified threaded rod and the distal element in the axial direction. A system according to any one of claims 1 or 2, further comprising a control device comprising at least one external magnet. The system of claim 3, further comprising a housing in which said at least one external magnet is rotatably disposed, and which accommodates a drive mechanism for rotating said external magnet around an axis parallel to the axis of said internal magnet, so that the external of the magnet led to the rotation of the inner magnet1. Система с регулируемым по длине штифтом для интрамедуллярного остеосинтеза, содержащая:штифт для интрамедуллярного остеосинтеза, содержащий:внешний проксимальный элемент；дистальный элемент, часть которого помещена в указанный внешний проксимальный элемент；резьбовой стержень, присоединенный к указанному дистальному элементу с возможностью вращения относительно указанного дистального элемента；внутренний магнит, помещенный в указанный внешний проксимальный элемент
