A novel intramedullary callus distraction system for the treatment of femoral bone defects

An intramedullary device has some advantages over external fixation in callus distraction for bone defect reconstruction. There are difficulties controlling motorized intramedullary devices and monitoring the distraction rate which may lead to poor results. The aim of this study was to design a fully implantable and non-motorized simple distraction nail for the treatment of bone defects. The fully implantable device comprises a tube-in-tube system and a wire pulling mechanism for callus distraction. For the treatment of femoral bone defects, a traction wire, attached to the device at one end, is fixed to the tibial tubercle at its other end. Flexion of the knee joint over a predetermined angle generates a traction force on the wire triggering bone segment transport. This callus distraction system was implanted into the femur of four human cadavers (total 8 femora), and bone segment transport was conducted over 60-mm defects with radiographic monitoring. All bone segments were transported reliably to the docking site. From these preliminary results, we conclude that this callus distraction system offers an alternative to the current intramedullary systems for the treatment of bone defects.