System for stabilizing the vertebral column including deployment instruments and variable expansion inserts therefor

Abstract

A system for stabilizing the vertebral column without requiring the excision of bone from the superior or inferior vertebrae or the resection of the adjacent anterior or posterior longitudinal ligaments. The system includes a stabilizing device and a deployment system composed of first and second coacting tools. The stabilizing device is made up of an expandable threaded insert and an expansion screw. The threaded insert is a hollow cylindrical member having a central cylindrical threaded bore, and a self tapping helical thread extending about the outer periphery of the member. The member is split at its proximal end in communication with the bore to form a pair of slots extending parallel to its longitudinal axis. The expandable insert is arranged to be screwed by the first tool into the intervertebral space between the superior and inferior vertebrae to a desired depth and with the slots oriented in a plane generally perpendicular to the longitudinal axis of the vertebral column. The first tool includes a pair of extending fingers which fit into the slots to achieve that end. When screwed in, the self-tapping threads cut into the cortical bone of the superior and inferior vertebrae contiguous to the intervertebral space, but not substantially into the cancellous bone. The expansion screw is tapered and arranged to be screwed into the internally threaded bore in the expandable insert by the second tool. The second tool fits into the first tool. When the expansion insert is screwed into the expandable insert it causes the slots of the expandable insert to open and thereby spread the superior and inferior vertebrae apart, thereby stabilizing the being's vertebral column.