An interbody spacer assembly includes a pair of end pieces spaced apart by
a connector extending between them. The end pieces extend generally
parallel to the end plates of adjoining vertebral bodies. Fasteners
connect the end pieces to the vertebral bodies. Bone graft material or
solid bone can be placed in the interior space defined by the end pieces
and connector, which bone graft material or solid bone eventually fuses
together and to the adjoining end plates through the end pieces. The
spacer assembly has ratchets to connect the two end pieces. The ratchets
near the fasteners are more closely spaced than the ratchets further from
the fasteners, allowing the spacer assembly to more closely approximate
the lordosis of the spine.