The mobile Condylus tertius occipitalis and fractures of the hypochordal clasp.
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.
Saternus
K-S
KS
Institute of Legal Medicine, Georg-August-University of Goettingen, Germany. ksatern@gwdg.de
Kernbach-Wighton
G
G
Koebke
J
J
D001268:Atlanto-Axial Joint / Q000002:abnormalities* / Q000473:pathology; D001269:Atlanto-Occipital Joint / Q000002:abnormalities* / Q000473:pathology; D002356:Cartilage / Q000473:pathology*; D003388:Cranial Fossa, Posterior / Q000002:abnormalities* / Q000473:pathology; D006801:Humans; D007594:Joint Loose Bodies / Q000473:pathology*; D009809:Odontoid Process / Q000002:abnormalities / Q000473:pathology; D019291:Skull Base / Q000293:injuries* / Q000473:pathology; D016103:Spinal Fractures / Q000473:pathology*