The accessory atlantoaxial ligament.
OBJECTIVE
The stability of the joints connecting the cranium to the upper cervical spine is of vital importance. The ligaments of this region, for the most part, have been thoroughly investigated, with the exception of the accessory atlantoaxial ligament.


METHODS
Ten cadaveric specimens were examined to observe the anatomy of this ligament.


RESULTS
This ligament was found in all specimens, and in each, it not only connected the atlas to the axis but also continued cephalically to the occipital bone. The approximate dimensions of this structure were 3 cm x 5 mm. Functionally, this ligament became maximally taut with a rotation of the head of 5 to 8 degrees. Laxity was observed with cervical extension, and maximal tautness was seen at 5 to 10 degrees of cervical flexion.


CONCLUSIONS
The accessory atlantoaxial ligament seems to participate in craniocervical stability and perhaps should be renamed the accessory alar ligament or accessory atlantoaxialoccipital ligament; both of these terms better denote its anatomic characteristics. Perhaps in the future, better magnetic resonance imaging techniques and machines will be able to identify this structure so as to appreciate its integrity after upper cervical spine trauma.
Department of Cell Biology, University of Alabama at Birmingham, Birmingham, Alabama 35233, USA. rstubbs@uab.edu
R Shane
RS
Tubbs
E George
EG
Salter
W Jerry
WJ
Oakes
D000368:Aged; D001268:Atlanto-Axial Joint / Q000033:anatomy & histology* / Q000601:surgery; D019416:Head Movements / Q000502:physiology; D006801:Humans; D008023:Ligaments, Articular / Q000033:anatomy & histology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009777:Occipital Bone / Q000033:anatomy & histology / Q000601:surgery; D009809:Odontoid Process / Q000033:anatomy & histology / Q000601:surgery; D012016:Reference Values