Navigated Osteosynthesis for Unstable Atlas Fractures: Technical Note and Case Series.

Objective: Fractures of the atlas are typically considered stable or unstable based on the integrity of the transverse ligament. Whereas stable Jefferson burst fractures can be treated nonoperatively, unstable fractures with disruption of the transverse ligament often require surgical intervention. Atlas osteosynthesis has been proposed as a motion-preserving alternative to atlantoaxial fusion. Intraoperative navigation may facilitate safe placement of C1 instrumentation.

Methods: Cases of patients with unstable atlas fractures treated with navigated osteosynthesis at a single level I trauma center were identified and retrospectively reviewed. Clinical presentation, surgical management, and postoperative outcomes were assessed.

Results: Eight patients underwent navigated posterior atlas osteosynthesis for unstable C1 fractures between December 2015 and January 2024. All patients demonstrated injury to the transverse ligament (Dickman type I [n = 1] and type II [n = 7]). Patients were followed with serial radiographs showing preserved alignment, with no significant change in postoperative atlantodental interval at the most recent follow-up (+0.2 ± 0.87 mm [mean change ± standard deviation]; P = 0.53). Six patients obtained follow-up computed tomography, all of which demonstrated evidence of osseous union across fractures without hardware complication. No patients developed postoperative instability requiring fusion.

Conclusions: Atlas osteosynthesis is an attractive motion-preserving approach to the treatment of unstable atlas fractures, avoiding the morbidity of atlantoaxial fusion. Classically reserved for Jefferson fractures with Dickman type II transverse ligament injury, atlas osteosynthesis may also be a viable option for type I transverse ligament injuries. Intraoperative navigation can be particularly useful for screw placement in the setting of traumatically distorted anatomy with lateral mass displacement.