[Os incae (the inca bone) (author's transl)].

The os incae derives from a fusion's failure of the cartilagineous and membranous portions of the occipital bone. It may represent with different features which - sometimes - are misinterpreted as traumatic in origin. The present report is based on the revision of 3697 skull examinations performed during the years 1976-1979 in the Department of Radiology of the Pediatric Clinics and Institute of Child Health of the University of Milan on a random children population. The percentage, frequency and morphological aspects of the os incae are considered.