Patent ID: 8337562

Claim:
A device for distracting a body tissue space between opposing tissue surfaces, comprising: an upper plate having an outer surface configured to contact one of the opposing tissue surfaces and a hub having a mating surface generally opposite said outer surface, said mating surface including a mating feature thereon; a lower plate having an outer surface configured to contact the other of the opposing surfaces, said lower plate having opposite spaced apart side walls configured to releasably engage said upper plate thereon and a support surface between said opposite side walls, said opposite side walls and said support surface defining a cavity, said hub of said upper plate being received between said opposite side walls of said lower plate and facing said support surface; an expansion member sized to be received into said cavity and supported on said support surface, and upon receipt therein to displace said upper plate from said lower plate, said expansion member having a complementary mating interface for interlocking engagement with said mating feature on said hub; and a releasable engagement feature between said upper plate and said lower plate configured to hold said upper and lower plates together until said upper plate is displaced by said expansion member.