Herbert Screw

Herbert screws inserted in the trochlea of the humerus.

A Herbert screw is a special purpose screw used to compress small fractures fragments. One end of the screw (upper ends in x-ray and photograph above) has cancellous threads while the other end has larger diameter cortical screw threads. The cancellous screw is inserted first and crosses the proximal fracture, screwing into the bone of the distal fragment. As it is screwed in, the proximal cortical portion engages the proximal bone fragment. Each turn of the screw causes the distal end to travel farther into bone than the proximal end, compressing the fracture.