“Floating” Lateral Mass Fractures of the Cervical Spine: A Retrospective Review of 60 Consecutive Cases
Authors: Bransford Richard , Manoso Mark , Bellabarba Carlo , Moore Timothy , Agel Julie 
Published: May 2015

Introduction

A rare subset of lateral mass fractures is the floating lateral mass fracture with fractures of the adjacent pedicle and lamina, which involves injury to two adjacent motion segments. Our objective is to describe this important subset in regards to the mechanism of injury, anatomical injury pattern, associated vascular injuries, neurological deficits, key radiographic features, and the type of stabilization required.

Material and Methods

A retrospective study of all floating lateral mass fractures treated at two level I trauma centers from 2007 to 2012 was performed. All medical records and spinal imaging studies were reviewed to identify patient demographics, mechanism of injury, associated spinal and skeletal injuries, vascular injuries, neurological deficits, the radiographical injury pattern, surgical treatment perioperative complications, and postoperative results. Plain radiographs and CT scans were used to assess axial alignment, degree of rotational instability, segmental kyphosis, and sagittal displacement. CT angiography was used to evaluate and grade vertebral artery injuries. When available, MRI evaluation was used to evaluate soft tissue injuries.

Results

Following institutional review board approval, 60 consecutive cases were identified from the trauma registry at two level I trauma institutes. The mean follow-up was 9 months (range, 0–42 months). Mean age was 36 years (range, 16–69 years). The most common levels were C6 (45%) and C5 (30%). The most common mechanisms of injury were high-speed motor vehicle accident (58%) and sports injury (18%). Rotational displacement manifested as anterolisthesis in 80% at the level below the lateral mass injury,13% at the level above, and 7% at both. Facet joint widening occurred at the level above and below in 63%, below only in 17%, above only in 12%, and no widening in 7%. Vertebral artery injuries occurred in 22%. MR (31 patients) demonstrated injury to the lower disc in 74%, above 10%, and a herniation in 32%. Neurological deficits occurred as radiculopathy in 60% and spinal cord injury in 31% (ASIA A2, B3, C2, and D4). External immobilization was initially chosen in eight patients (13%). All patients, who were treated nonoperatively, developed subluxation of greater than 3 mm in less than 3 weeks, and six of the eight underwent surgery. Ultimately, operative treatment was performed in 58 of the 60 patients. A single level ACDF was performed in nine (15%) patients. Six of the nine were followed at a minimum of 6 months, and five (83%) patients developed 3 mm of subluxation at the level above the fusion. A two-level anterior fusion alone was performed in 33 (57%) patients. Posterior fusion alone was performed in six (10%) patients. A combined anterior and posterior fusion was performed in seven (9%) patients. There were no wound infections or postoperative neurological deteriorations.

Conclusion

A floating lateral mass fracture results from a high-energy injury and involves two motion segments. Vertebral artery injuries and neurological deficits are common. Two-level anterior or posterior fusions are effective means of treatment, as conservative management or single level fusions are ineffective at providing anatomical alignment.