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Incus

incus

The incus is the middle of the three ossicles, shaped like an anvil (Latin: incus). Its body articulates with the malleus at the incudomalleolar joint in the epitympanum. It has a short process attached by a ligament to the posterior wall of the epitympanum, and a long process that descends to end in the lenticular process, which articulates with the head of the stapes at the incudostapedial joint.

Region: Head & Skull

Clinical Relevance

Clinical Notes

The long process of the incus is the most frequently disrupted part of the ossicular chain in temporal bone trauma and chronic otitis media, as its blood supply is the most tenuous of all the ossicle components. Cholesteatoma preferentially erodes the incus long process, producing an air-bone gap on audiogram. In ossiculoplasty, an incus interposition or PORP (partial ossicular replacement prosthesis) bridging from the malleus handle to the stapes capitulum is the most commonly used reconstruction when the incus long process is absent.

Pathology

Common Injuries & Conditions

Incus Long Process Necrosis

Avascular necrosis of the poorly vascularised long process of the incus from chronic otitis media or cholesteatoma produces a progressive conductive hearing loss with a 30-60 dB air-bone gap, managed with PORP interposition from malleus to stapes.