Original paper

The mobile Condylus tertius occipitalis and fractures of the hypochordal clasp

Saternus,K.-S.;Kernbach-Wighton, G.; Koebke, J.

Abstract

The Condylus tertius is defined as a small bony hunch on the anterior surface of the clivus.Its presence means an enormous functional impairment of the upper head joint,looking at the 3 -point-contact between the skull base and the upper cervical vertebrae.In 10 of the 2000 forensic examined bodies,analyses of neck vertebra + skull base revealed this feature.The origin of these findings is discussed,as stated in the literature of embryology,to be a suboccipital hypochordal plate.So in one of the cases the condylus was found at the hypochordal plate itself whereas the so-called socket was lying at the margin of the clivus.In three cases there was found a free body between the apex of the Dens and the Clivus forming a mobile Condylus tertius.In our opinion its position varies over the anterior arch of the atlas and the apex of the dens as a result of rotatory forces between the atlas and axis and physiological strain.Examples are given to elucidate this.There is a difference in the differentiation of the deposited material according to functional demand.A pressure bed (i.e.a Condylus tertius)is formed when a bony structure is deposited on the clivus.This functional prospect relativises the hypothesis of a purely constitutional genesis of the Condylus tertius.A fracture of the hypochordal clasp being joined with a bony connection to the anterior atlantic arch is described for the first time.

Keywords

ondylus tertiusskull basebiomechanicsfunctional adaptationhypochordal platefracture of the hypochordal plate