Injuries of the upper cervical spine-how can instability be identified?

The diagnosis of instability of the injured upper cervical spine remains controversial, due to its complicated anatomical configuration and biomechanical property. Since identifying unstable injuries of the upper cervical spine is essential for immediate stabilizing therapy, this article reviews the current classification systems of upper cervical spine injuries and their statements towards instability.

A systematic review of literature concerning upper cervical spine injuries was performed on the PubMed database from inception to December 2019. An English literature search was conducted using various combinations of keyword terms.

Numerous separate classification systems for each specific injury of the upper cervical spine were obtained. The early classifications are based primarily on injury morphology and mechanism. The recent classifications pay more attention to the investigation of ligamentous status. Various instability criteria were established as well. The determinants involve translation, vertical distraction, angulation, rotation, obliquity of fracture line, comminution, and ligamentous disruption. The status of crucial ligaments plays a key role in determining instability of upper cervical spine injuries. CT scan is more sensitive and reliable than X-ray in detecting misalignment of the upper cervical spine.

Only a few classification systems support decision-making concerning instability leading to early operative treatment. The ligamentous integrity is the key element of impacting the stability of the upper cervical spine injuries. The transverse ligament serves as the most crucial element in determining the stability of occipital condyle fractures and atlas fractures as well as atlanto-axial injury. The integrity of anterior longitudinal ligament, disc, and facet joint attributes to the stability of axis fractures. The integrity of tectorial membrane and alar ligaments determines the stability of atlanto-occipital dislocation. The development of a newly classification system concerning ligamentous instability with a high clinical and scientific impact is recommended.