A screw formed of cortical bone for use in the human body with an implant
having a screw hole for receiving at least a portion of a screw
therethrough, includes a shaft with a thread along at least a portion of
its length. The thread has an outer diameter dimensioned to pass through
the screw hole in the implant. The trailing end of the screw is
configured to cooperatively engage at least a portion of the screw hole
of the implant so as to prevent the screw from linear motion along the
mid-longitudinal axis of the shaft in a direction opposite to the
direction of insertion when the screw is threaded through the screw hole
to attach the implant to a bone portion of the human body. The screw is
formed substantially of cortical bone of a single cortical thickness.