Exploration of the craniocervical junction in cadavers of elderly individuals.
Histologic evaluation of osseous contact zones observed between the basiocciput and anterior arch of the atlas.
Previous findings of possible osseous contact zones at the anterior rim of the foramen magnum and anterior arch of the atlas suggested the existence of real joints.
A total of 100 cadaver specimens were investigated using magnetic resonance imaging, computerized tomography, and median saw-cut and histologic sections.
Of the specimens, 42% showed osteoarthritis-related osteophytes (primarily directed cranially) of the articular surfaces of the median atlantoaxial joint. In 5 cases, a large osteophyte of the anterior arch of the atlas touched the basiocciput. In 3 cases, a third occipital condyle touched the anterior arch of the atlas and/or tip of the dens. These osseous contact zones were histologically verified as real joints (the median atlanto-occipital or occipito-odontoid joints).
Of the 8 median atlanto-occipital joints found in this study, 3 were third occipital-condyle based, and 5 osteoarthritis-based. The former were congenital in character, while the latter were acquired.