Patent ID: 7828845

Claim:
An expandable spacer for implantation between opposing endplates of adjacent vertebrae, said spacer comprising: a cylindrical body extending along a vertical axis and composed of a shape memory polymeric material and comprising a cylindrical-shaped peripheral sidewall extending about said vertical axis and defining an interior cavity and vertebral bearing surfaces defined by opposite end surfaces of the cylindrical-shaped peripheral sidewall, said vertebral bearing surfaces defining openings in communication with the interior cavity, said body provided in a first configuration sized to overlay a first portion of a vertebral endplate wherein said body upon absorption of thermal energy expands to a second configuration sized to overlay a second portion of the vertebral endplate, said second portion having a greater area than the first portion; and wherein the peripheral sidewall in the first configuration has a first lateral dimension and the opposite end surfaces of the peripheral sidewall each define a first bearing surface area; and wherein the peripheral sidewall in the second configuration has a second lateral dimension greater than the first lateral dimension and the opposite end surfaces of the peripheral sidewall each define a second bearing surface area significantly greater than the first bearing surface area.