Patent ID: 8435299

Claim:
An intervertebral spacing implant comprising: a seat having a proximal end, a distal end, and a plurality of flat surfaces between the proximal and distal ends; a plurality of branches coupled to the distal end of the seat and extending in a distal direction away from the seat, the seat and the branches forming a cage defining an internal volume, each branch having an inward side and an outward side; a spacer, having a maximum outer diameter and a connector to removably couple to a spacer-advancing instrument, configured to fit within the cage and move along the inward side of each branch upon the urging of the spacer-advancing instrument, the spacer having a thickness less than a length of the cage, the spacer and cage being sized so at least one branch will move from an unextended position to an extended position when the spacer is urged in the distal direction along the inward side of each branch by the spacer-advancing instrument; a shoulder formed on the inward side near the distal end of each branch, the shoulders adapted to removably receive the spacer between the shoulders and the distal end of each branch to maintain the at least one branch in the extended position; and an orifice, having a maximum outer diameter, formed in the seat extending from the internal volume of the cage and through the seat to the proximal end of the seat, the orifice adapted to allow the spacer-advancing instrument to pass through; wherein (a) a substantial portion of the internal volume is empty when the at least one branch is in the extended position, and the substantial portion is substantially larger than the portion of the internal volume occupied by structure of the implant, (b) the maximum outer diameter of the spacer is greater than the maximum outer diameter of the orifice, and (c) the spacer, the connector, and the shoulders are configured to removably couple the spacer-advancing instrument to the spacer and withdraw the spacer from between the shoulders and the distal end of each branch to return the at least one branch from the extended position to the unextended position.