Self-shearing pedicular screw has transverse aperture in central zone leaving slot for screwdriver when upper section is detached

摘要

The pedicular screw (1) consists of a lower threaded section (2) for implanting in the bone tissue, an upper threaded section (4) to receive a connecting plate and locking nut, made with a fracture zone (10), and an intermediate section (15) to receive the connecting plate while it is being locked by the nut. In the fracture zone the upper section has a transverse central aperture (9) which leaves a slot for the tip of a screwdriver blade when the upper threaded section has been detached. A variant of the design has two crossing apertures to leave a socket for a cruciform screwdriver tip.