A Herbert screw is an instrument used in the internal fixation of an unstable scaphoid fracture. It is a headless screw with thread along its entire length. The two halves of the screw have a different pitch though, which causes compression of the fracture.
Indications
Unstable scaphoid fractures include:
displacement >1 mm
scapholunate angle >60o
radiolunate angle >15o
delayed/non-union
Disadvantages
ineffective in long-standing non-united scaphoid fractures
History and etymology
It is named after Timothy James Herbert (British Orthopedic Surgeon) 2.