Abstract: The intramedullary coupled pin is a rigid device for internal fixation of tubular bones in humans and animals. The device makes use of the natural marrow cavity of the bone and the musculature bridging the fracture site to cause maximum stabilization of the fractured bone. A long rod has a tip coupling on one end and a socket coupling on the other, which form the parts of the pin when cut. Each end of the rod is measured, cut and inserted into the intramedullary cavities. Then the parts of the pin are locked together at the fracture site by the coupling system of the pin. The intramedullary coupled pin is permanently implanted inside the bone because the socket system can only be unlocked by pulling the two parts of the pin directly apart.