Entwicklungsstörungen am atlanto-okzipitalen Übergang

The median atlanto-occipital joint in advanced age

STUDY DESIGN

Exploration of the craniocervical junction in cadavers of elderly individuals.

OBJECTIVE

Histologic evaluation of osseous contact zones observed between the basiocciput and anterior arch of the atlas.

SUMMARY OF BACKGROUND DATA

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.

METHODS

A total of 100 cadaver specimens were investigated using magnetic resonance imaging, computerized tomography, and median saw-cut and histologic sections.

RESULTS

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).

CONCLUSIONS

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.

Accessory joints between basiocciput and atlas/axis in the median plane

To explore the many osseous irregularities that are found in the area between the basiocciput, the anterior arch of the atlas and the tip of the dens axis we studied 99 cadaver specimens using magnetic resonance tomography (MRT), computed tomography (CT), median saw-cut sections, and histological sections. Additionally, "dry" specimens of the skull (n = 110), atlas (n = 56), and axis (n = 33) were investigated. In the median plane, the dry and cadaver specimens exhibited osteoarthritis-related osseous outgrowths and osteophytes of the articular surfaces of the median atlanto-axial joint (n = 63), and the presence of congenitally developed free ossicles (n = 22) and of third occipital condyles (n = 3). The largest osteophytes (giant osteophytes) (n = 4) of the anterior arch of the atlas formed osseous contact zones with the basiocciput that were visible histologically as real joints and were designated accessory median atlanto-occipital joints. The third occipital condyles also formed osseous contact zones, visible histologically as real joints, with the anterior arch of the atlas or with the tip of the dens, and were designated accessory atlanto-occipital or occipito-odontoid joints. Frequent free ossicles, incorporated into the accessory joint, were found by histological examination to be covered with hyaline cartilage.