Assessing the Impact of Undiagnosed C1‒C2 Rotatory Subluxation in the Conservative Treatment of Odontoid Fractures.

Background: The presence of clear high-grade rotatory subluxation, in addition to an odontoid fracture, is a definite indication for surgery. However, the presence of a more subtle subluxation-Grades 1, 2, or 3-can often be overlooked, and as a result, prognostic associations with second cervical vertebrae (C2) fractures are rare. In light of this, we assessed the failure rate of conservative management in patients with both an odontoid fracture and a concurrent first and second cervical vertebrae (C1‒C2) rotatory subluxation.

Methods: A retrospective, cohort (nested case-control) study of patients with odontoid C2 fractures with or without C1‒C2 joint rotatory subluxation was performed. Patients were classified according to the type of odontoid fracture (Alonzo classification) and the presence of C1‒C2 subluxation (Feldings classification). The number of patients who were initially treated with collars and then underwent surgery due to conservative treatment failure was analyzed. We performed logistic regression analysis to determine the odds ratio and generate a receiver operating characteristic curve of the association between the degree of subluxation and failure of conservative treatment.

Results: One hundred fifteen patients with C2 fractures that were treated conservatively with or without C1‒C2 rotatory subluxation. Of all 115 patients, 29 (25%) experienced treatment failure and required surgery. A statistically significant correlation was found between treatment failure and the presence of rotatory subluxation (odds ratio 10), compared with patients without C1‒C2 subluxation.

Conclusions: In our series, C2 Alonzo fractures with a C1‒C2 rotatory subluxation had a 10-fold increased risk of secondary displacement and subsequent need for surgery. Further research on this association could improve the management of these conditions.