The mobile Condylus tertius occipitalis and fractures of the hypochordal clasp

• Published in: Anthropologischer Anzeiger Vol. 66; no. 2; p. 155
• Main Authors: Saternus, K-S, Kernbach-Wighton, G, Koebke, J
• Format: Journal Article
• Language: English
• Published: Germany 01.06.2008
• Subjects: Atlanto-Axial Joint - abnormalities; Atlanto-Axial Joint - pathology; Atlanto-Occipital Joint - abnormalities; Atlanto-Occipital Joint - pathology; Cartilage - pathology; Cranial Fossa, Posterior - abnormalities; Cranial Fossa, Posterior - pathology; Humans; Joint Loose Bodies - pathology; Odontoid Process - abnormalities; Odontoid Process - pathology; Skull Base - injuries; Skull Base - pathology; Spinal Fractures - pathology
• ISSN: 0003-5548
• DOI: 10.1127/aa/66/2008/155

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.