Patent ID: 8142508

Claim:
A spinal cage comprising: a wall having an internal surface and an external surface, both extending vertically and generally parallel to a vertical axis of said spinal cage and progressing circumferentially, wherein said external surface forms a closed circumference, and wherein said internal surface forms a closed perimeter defining an interior space; wherein said internal wall surface comprises at least a first internal groove within said internal wall surface, said groove extending vertically at least approximately parallel to said vertical axis; wherein said first internal groove has two respective side walls opposed to each other and generally parallel to each other, said two respective side walls defining a groove width therebetween, said first internal groove having a groove base surface connecting between said side walls; wherein at a first vertical end of said first internal groove, said side walls extend as far as said wall extends vertically; wherein at an opposed vertical end of said first internal groove, said side walls connect with a curved surface within said internal wall surface, said curved surface defining a cylindrical space within said internal wall surface having a cylindrical diameter; and wherein said cylindrical diameter is greater than said groove width and said cylindrical space is centered midway between said side walls.