The Lenticular Process of the Incus

Objective: Seventeenth century anatomists, including Franciscus Sylvius, identified a small bony structure between the distal end of the incus and the stapes that they believed was a separate and thus additional ossicle. The existence of the ossicle at the distal end of the long process of the incus was controversial for the next 200 years. In the 19(th) century, anatomists including Johann Friedrich Blumenbach, Samuel Thomas Soemmerring, Henry Jones Shrapnell, Eduard Hagenbach, and Joseph Hyrtl provided numerous arguments to demonstrate why the so-called additional ossicle was actually attached to the incus by a thin strut, and thus not a separate bone. The objective of this study was to review the history of the discovery and description of the lenticular process of the incus. Data Sources: Data sources included original published manuscripts and monographs obtained from the historical collections at Washington University in St. Louis and photographs of original materials from cooperating libraries. Results: A detailed study of the published evidence revealed that the lenticular process of the incus was originally thought to be a separate, or fourth, ossicle. Later studies revealed that the lenticular "ossicle" was actually attached to the incus by a thin strut. Conclusion: The ovoid end of the incus should be referred to as the "lenticular process" of the incus, attached to the long process by a thin strut or pedicle. The best nomenclature for the bony connection between the lenticular process and the long process of the incus remains uncertain.