A REPORT OF NINETEEN CASES OF THE ATLANTO-OCCIPITAL FUSION / 解剖学报

ABSTRACT

The mode of the atlanto-occipital fusion in 19 Chinese skulls was studied andanalysed. According to various degrees of fusion it may be divided into the following 5types: Type Ⅰ: The atlanto-occipital joints, anterior and posterior atlanto-occipital mem-branes of both sides were ossified (36.8%). Type Ⅱ: The atlanto-occipital joints, the anterior atlanto-occipital membrane andthe lateral parts of the posterior atlanto-occipital membrane were all ossified (21.1%). Type Ⅲ: The atlanto-occipital joints of both sides, the anterior and posterioratlanto-occipital membranes of one side were ossified (26.3%). Type Ⅳ: The atlanto-occipital joints and the lateral parts of the anterior atlanto-occipital membrane were ossified (5.3 %). Type Ⅴ: Only the atlanto-occipital joints were ossified (10.5%). In addition to the above, a case showing the atlanto-axial joints consisted of fivejoints and a case showing the anterior atlanto-axial joint and the lateral atlanto-axialjoints bounded by one articular capsule were found. The unusual courses of the vertebral artery to the cranial cavity was found eitherthrough the lateral part of the occipital bone, or the anterior condylar foramen and theposterior surface of the transverse process of the atlas.