Primary internal fixation of unilateral C1 lateral mass sagittal split fractures: a series of 3 cases.

STUDY DESIGN: Retrospective case review of adult patients who sustained C1 lateral mass sagittal split fractures treated with primary internal fixation.

OBJECTIVE: To present the outcomes of patients treated with primary C1 open reduction and internal fixation of this previously described injury.

SUMMARY OF BACKGROUND DATA: The majority of C1 fractures can be effectively treated nonoperatively with external immobilization unless there is an injury to the transverse atlantal ligament. We have previously described an uncommon fracture variant involving a unilateral sagittal split of the C1 lateral mass with high propensity for late deformity and pain, despite lack of compromise to the transverse atlantal ligament.

METHODS: A retrospective review of all patients with C1 fractures between September 2002 and October 2008 identified 3 consecutive patients from a level I trauma center (Harborview Medical Center, Seattle, WA) with this unique C1 lateral mass fracture treated with primary internal fixation without fusion. Patients' charts and radiographs were reviewed.

RESULTS: One patient died within 2 weeks of injury owing to associated injuries. The 2 survivors had follow-up averaging 14 months. Both went on to stable healing with satisfactory alignment. Rotational range of motion averaged an arc of 120 degree at final follow-up. No patient went on to develop the previously described "cock-robin" deformity from subluxation of the lateral mass with settling of the occiput onto the C2 lateral mass.

CONCLUSIONS: Patients with a unilateral sagittal split of the C1 lateral mass can be successfully managed with primary open reduction and internal fixation with a transversely oriented construct using C1 lateral mass screws. Internal fixation of the atlas without fusion prevents progressive, painful deformity and the need for complex occipitocervical reconstruction procedures that have been reported with nonoperative management of these injuries.