The Lenticular.

Objective: The lenticular was an instrument introduced by Galen to facilitate cutting the bone of the cranium. Illustrations of the instrument first appeared in the 16th century during the Renaissance. These illustrations have been widely used, but the instrument's shape seems ill-adapted to its function. Archaeological research in Rimini, Italy, unearthed a similar instrument with a shape that seems more suitable for the function of cutting cranial bone. The object of this study was to evaluate the efficacy of these two instruments for cutting the bone of the cranium.
Methods: Replicas of the two instruments were obtained. Trepanation was performed in the left parietal region of a sheep's head. In addition, the application of the instruments in the literature was analyzed.
Results: The Roman lenticular cut the cranium with ease. The Renaissance instrument failed to cut the bone and only separated the dura mater from the bone. The lenticular had been used to cut bone up to the 13th century. In contrast, the Renaissance instrument was not used to cut bone but to smooth roughened bony surfaces and to remove spicules of bone that were in contact with the dura.
Conclusions: Analysis of illustrations in medical publications should be undertaken with the same rigor as applied to analysis of text.