Patent ID: 6905512

Claim:
A system for stabilizing a superior vertebra and immediately adjacent inferior vertebra of the vertebral column of a living being without requiring the excision of bone from the superior or inferior vertebrae or the resection of the adjacent longitudinal proximal or distal ligaments, said system comprising a variable expansion device and a deployment system, said variable expansion device comprising a hollow one-piece expandable insert and an expansion insert, said expandable insert comprising a one-piece cylindrical body having a longitudinal axis and a proximal end portion and a distal end portion, said proximal end portion having a pair of slots extending therethrough generally parallel to the longitudinal axis of the expandable insert, said slots forming two cantilevered body portions of said cylindrical body, said slots extending partially into said distal end portion, said distal end portion and at least a portion of said proximal end portion of said expandable insert having an outer surface about which an external helical self-tapping thread extends, said distal end portion and said at least a portion of said proximal end portion of said expandable insert being of a sufficient size to be screwed into the intervertebral space between the superior and inferior vertebrae by said deployment instrument, whereupon said expandable insert is located at a desired depth within the intervertebral space with said slots oriented in a plane generally perpendicular to the portion of the longitudinal axis of the being's vertebral column between the superior and inferior vertebrae, said self-tapping thread being of a sufficient height to cut into the cortical bone of the superior and inferior vertebrae contiguous to the intervertebral space but not substantially into the cancellous bone thereof such that said outer surface of said expandable insert about which said external thread extends does not substantially displace any cortical bone, said proximal end portion of said expandable insert having an internally threaded bore extending therethrough and into at least a portion of said distal end portion, said internally threaded bore communicating with said slots said expansion insert having an externally threaded outer surface and being arranged to be screwed into said bore in said proximal end portion of said expandable insert by said deployment system, said expansion insert having an outer diameter adapted to cause said cantilevered body portions to deflect outwardly when said expandable insert is in said desired depth, whereupon said slots open to spread the superior and inferior vertebrae apart, thereby stabilizing the being's vertebral column, said deployment system comprising a tool which includes a pair of projecting fingers arranged to be located within respective ones of said slots to enable said expandable insert to be screwed into the intervertebral space to said desired depth.