Implantable bone screw with threaded shank

摘要

The screw comprises a drive head (10) and a threaded shank (3), the joint between which shears at an effort below that which leads to the shank breaking. The head connects with the shank through a polygonal-section rod (12) which can be inserted and withdrawn from a hole (7) of similar cross-section. The head and rod are connected by a neck (11) which shears at a given effort, while the head, neck and rod have an axial channel through them to receive a guide rod. After the drive head has sheared off the screw can be turned by replacing it with a solid head and polygonal rod inserted into the hole in the screw.