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

Abstract

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.

Vertebral spinal osteophytes

“…Extra body mass increases weight on the vertebral column, contributing to mechanical stress associated with degenerative changes of osteoarthritis. Additional etiological factors are hypervitaminosis A (Seawright et al 1965;Yee et al 1985) and secretion of bone morphogenetic factor for stimulation of bony tissue growth (Hanamura et al 1980;von Ludinghausen et al 2005;Urist et al 1979;Yee et al 1985). Recent studies suggest excessive mechanical stress, particularly at a young age, may predispose one to osteophyte formation later in life (O'Neill et al 1999;Schmitt et al 2004).…”

“…These additional contact points between the osteophyte and basiocciput were histologically confirmed to be real joints, designated accessory median atlanto-occipital joints(von Ludinghausen et al 2005).Recently, von Ludinghausen et al (2006) investigated 100 cadavers, of which 42 showed osteophytes of the articular surfaces of the median atlantoaxial joint. In five cases, a large osteophyte on the anterior arch of the atlas made contact with the basiocciput in a similar manner as described in their 2005 study(von Ludinghausen et al 2005).…”

The supraodontoid space or “apical cave” at the craniocervical junction: A microdissection study

“…These structures are easily compressed. Because the supraodontoid space continually changes dimension with flexion/extension of the head as the clivus approaches the atlas (Werne, 1957), it would appear to be advantageous to have compressible structures here, although a number of unyielding anomalous tissues have been known to be present in the apical cave (von Lüdinghausen et al, 2005). The soft tissues may also serve to protect the delicate neurovascular structures supplying the tissues of the CCJ where 50% of the movement of the cervical spine occurs.…”

“…These are often associated with anomalous median bony elements at the CCJ and are commoner in advancing age (von Lüdinghausen et al, 2005). Engelman et al (1989) have shown that various normal structures (fat pads, ossiculum terminale, Bergmann's ossicle, and os odontoideum), anomalous structures (''spikes, crowns, and coulisses '' von Lüdinghausen et al, 2005'' von Lüdinghausen et al, , 2006 and pathological structures (ossified ligaments, Rheumatoid tissues, separated dens) may occupy the space. In addition, the authors have found various tissues, such as fat, fibrous tissue, fibrofatty tissue, cartilage, fibrocartilage, bone, and combinations of these tissues occupying the apical cave.…”

Unusual case of occipital vertebra in a medieval skeleton

“…To our knowledge the present case is the first description in the literature of a basilar process connected both to the anterior arch of the atlas and to the dens of the axis. Indeed, an occipital vertebra joined to the first two cervical vertebrae represents an extremely rare trait that has been reported so far only in a very few cases of median third condyle (Von Lüdinghausen et al ., 2005, 2006). Because no histological examination was carried out, there cannot be any definitive answer as to whether these extra connections represent true articulations.…”