Open Posterior Reduction and Stabilization of a C1 Burst Fracture Using Mono-axial Screws

Study Design. Biomechanical study of a posterior reduction and stabilization of a Jefferson C1 burst fracture using mono-versus poly-axial screws. Objective. To introduce a new motion-preserving surgical method for reduction and stabilization of an isolated Jefferson fracture and investigate its effectiveness with a biomechanical study. Summary of Background Data. Jefferson fractures have been treated conservatively by immobilization, traction, or surgical fusion of C1-C2 or occiput-to-C2. Conservative treatment usually requires prolonged immobilization with a cumbersome external brace. Surgical fusion, however, eliminates the important range of motion (ROM) of C1-C2 or occiput-to-C2. Methods. Six occiput-to-C3 cadaveric specimens were tested biomechanically. After creating a Jefferson fracture, bilateral atlantal lateral mass screws were inserted on the posterior aspect of each specimen. The screws were connected with a rod and nuts. The posterior distance and the anterior distance were measured to evaluate the magnitude of reduction and resistance to loading after instrumentation placement. Measurements were performed after mono-and poly-axial head screw insertion, and then using destabilized specimens. ROM was also measured after applying a 1.5 Nm moment to six cardinal directions before the trauma, after mono-and poly-axial screw fixation and in destabilized specimens. Results. The posterior distances after mono-axial and poly-axial screw fixations were significantly reduced compared with that of the destabilized atlas. In the specimens reduced with mono-and poly axial screws, the averages were 50.2 and 50.2 mm, and in the destabilized specimen, the average was 54 mm. The anterior distance was also decreased by mono-axial screw fixation compared with the anterior distance for the destabilized specimen but was similar to that of poly-axial screw fixation. The ROMs in flexion/extension, lateral bending, and axial rotation were greatest in the destabilized model, followed by poly-axial and then mono-axial fixation. Conclusions. The current study shows that the posterior screw and rod fixation of a Jefferson fracture is feasible and effective in providing immediate reduction and stabilization especially with the mono-axial screw system.