any structural anomaly of the anvil-shaped, central bone of the three auditory ossicles which articulates with the head of the malleus anteromedially and the stapes inferomedially; its parts include: a body which articulates with the head of the malleus, and to which the superior ligament of the incus is attached (to the roof of the middle ear cavity); a long crus down to the lentiform process (lenticular process) which articulates with the stapes; and a short crus to which the posterior ligament of the incus is attached