The A-Spire screw is a type of compression screw which – unlike Herbert screws – does not only have two threaded parts but it is threaded in the full length. The compression effect is created by the continuously changing – reduced – pitch. This setup not only increases compression but the pullout force of the screw as well, thus the stability of the A-Spire screws are much higher than Herbert type screws. Also, A-Spire screws have conical core which compacts the bone around the screw enabling the surgeon to fix porotic bones as well.