Zero Profile Spinal Fusion Cage

An intervertebral fusion cage, comprising:

• a) a proximal wall and a distal wall,
• b) first and second side walls connecting the proximal and distal walls, an upper bearing surface adapted for gripping an upper vertebral endplate and a lower bearing surface adapted for gripping a lower vertebral endplate, the upper bearing surface having at least one upper opening therethrough adapted to promote bony fusion, the lower bearing surface having at least one lower opening therethrough adapted to promote bony fusion,
• c) a first guide surface canal formed in the upper bearing surface and extending substantially from the proximal wall to the distal wall,
• d) a first rail adapted for slidable reception in the first canal and having an outward opening recess adapted for reception of a first screw head.

A method of inserting a fusion cage into an intervertebral disc space formed by upper and lower vertebral endplates, comprising the sequential steps of:

• a) inserting a trial having a guide surface canal into the disc space,
• b) drilling or awling the hole through the trial drill guides,
• c) inserting a first and the second screws into the upper and lower vertebral endplates, the first screw having a shaft and a screw head,
• d) removing the trial,
• e) inserting a fusion cage having a guide surface canal into the disc space so that the screw head is received in a distal portion of the canal, and
• f) distally translating the cage into the disc space so that the screw head becomes received in a proximal portion of the cage canal.

A spinal assembly comprising:

• i) a first bone anchor comprising:
• a) a distal shaft and
• b) a proximal screw head, and
• ii) an intervertebral fusion cage, wherein the intervertebral fusion cage comprises:
• a) a proximal wall and a distal wall,
• b) first and second side walls connecting the proximal and distal walls, an upper bearing surface adapted for gripping an upper vertebral endplate and a lower bearing surface adapted for gripping a lower vertebral endplate, the upper bearing surface having at least one upper opening therethrough adapted to promote bony fusion, the lower bearing surface having at least one lower opening therethrough adapted to promote bony fusion,
• c) a first guide surface canal formed in the upper bearing surface and extending substantially from the proximal wall to the distal wall, the canal adapted for distal reception of the proximal screw head,
• wherein the first screw head is received in the canal.

A method of inserting a fusion cage into an intervertebral disc space formed by upper and lower vertebral endplates, comprising the sequential steps of:

• g) inserting a first screw into the upper vertebral endplate, the first screw having a shaft and a screw head,
• h) inserting a trial having a guide surface canal into the disc space so that the screw head is received in the canal of the trial,
• i) removing the trial, and
• j) inserting a fusion cage having a guide surface canal into the disc space so that the screw head is received in a distal portion of the canal.