Mechanical Comparison of Anterior Spinal Instrumentation in a Burst Fracture Model

Abstract

This study demonstrates that the broad 4.5 mm dynamic compression plate provides superior stiffness in axial and torsional loading compared to the two anterior rod constructs (Zielke-Slot and Kostuik-Harrington) and the thinner ASIF T-plate in this ex-vivo testing. The Armstrong National Research Council (NRC) plate, designed specifically for anterior spinal instrumentation, has essentially the same mechanical performance characteristics as the broad dynamic compression plate. When placed on the lateral aspect of the vertebral body, these latter two plates lie well away from the anterior vascular structures. Screws are placed slightly off set in the plate, two each in the vertebral bodies immediately above and below the fracture, the screws directed transversely across the vertebral body. The broad DCP plate is easily contoured and implanted, and will allow 1.8 mm of compression to be applied to a strut graft between vertebral bodies. Anterior surgery for the treatment of burst fractures with retropulsed bone provides a means for direct decompression of the spinal canal. With an appropriate implant, additional advantages include instrumentation over a shorter distance (one above and one below the fracture) and no need for further operative procedures to implant or remove posterior implants. Due to their superior stiffness in axial and torsional load, the broad dynamic compression plate and the Armstrong NRC plate appear to fulfill most nearly the ideal attributes of an anterior spinal implant for the treatment of burst fractures of the throacic and lumbar spine.