There are usually coexisting injuries to the skull base or craniocervical ligaments, most commonly the tectorial membrane.
2,6) Additionally, the tectorial membrane is typically intact and firmly attached both to the clivus and at its inferior attachment at the posterior mid axis body.
MRI will best show typically high T1 methemoglobin extending distal to the mid-axis body, overlying the intact, uninjured tectorial membrane at the craniocervical junction.
Anderson and Montesano12 Classification of Occipital Condyle Fractures Type Description Biomechanics Type I Impaction Results from axial loading; ipsilateral alar ligament may be compromised, but stability is maintained by contralateral alar ligament and tectorial
membrane Type II Skull base extension Extends from occipital bone via condyle to enter foramen magnum; stability is maintained by intact alar ligaments and tectorial
membrane Type III Avulsion Mediated via alar ligament tension; associated disruption of tectorial
membrane and contralateral alar ligament may cause instability Table 2.
The principal stabilisers of the CCJ are the tectorial membrane, transverse ligament and the alar ligaments (1) (see Fig.
Tectorial membrane injury is manifest by discontinuity of the normal T2 hypo-intense signal of the ligament, increase of the T2 signal intensity or if the intact membrane is elevated by a REH.
Only a few of these patients proceed to have MRI studies performed, where direct demonstration of tectorial membrane injury and REH is made possible.
Figure 7) MRI can show injuries that involve the articular capsules, tectorial
membrane, and other atlantoaxial ligaments.
6,8] More specifically, type II collagen is a significant component of the osseous spiral lamina, the spiral limbus, and the tectorial