Which of the following ossicles is most commonly eroded first in cholesteatoma?

Explanation

## Ossicular Erosion Patterns in Cholesteatoma **Key Point:** The incus is the most commonly and earliest eroded ossicle in cholesteatoma, followed by the stapes and malleus. ### Mechanism of Ossicular Erosion Cholesteatoma causes bone erosion through multiple mechanisms: 1. **Pressure necrosis** — mechanical pressure from expanding cholesteatoma mass 2. **Enzymatic degradation** — collagenase and proteases produced by granulation tissue 3. **Osteoclast activation** — inflammatory mediators stimulate bone resorption 4. **Bacterial toxins** — secondary infection accelerates erosion ### Order of Ossicular Involvement | Ossicle | Frequency of Erosion | Typical Sequence | |---------|----------------------|------------------| | Incus | 90–95% | 1st (most common) | | Stapes | 70–80% | 2nd | | Malleus | 10–20% | 3rd (least common) | | Footplate | Rare | Late/severe cases | **High-Yield:** Incus long process erosion is the hallmark ossicular finding in cholesteatoma and is the most frequent single ossicular defect. ### Anatomical Reason for Incus Vulnerability - The incus has the **poorest blood supply** of the three ossicles - Located directly in the path of posterosuperior retraction pockets - Lenticular process is particularly exposed to erosion - Lack of periosteal protection in the middle ear space **Clinical Pearl:** Ossicular chain reconstruction (ossiculoplasty) is often needed after cholesteatoma removal; incus reconstruction is most frequently required. [cite:Glasscock-Shambaugh Surgery of the Ear Ch 12]