Methods and apparatuses for vertebral body distraction and fusion employing a coaxial screw gear sleeve mechanism

A size-adjustable implant positionable between adjacent first and second vertebral bodies for fusion of the adjacent first and second vertebral bodies, the implant comprising:

• a first member;
• a second member;
• a coaxial screw gear sleeve mechanism disposed between the first member and the second member, the coaxial screw gear sleeve mechanism including a sleeve having a helical thread with a plurality of gear teeth thereon;
• and
• wherein selective rotation of the sleeve causes an expansion of the first member relative to the second member due to a telescoping expansion of the sleeve translating relative to one of the first member and the second member simultaneously with the other of the first member and the second member translating relative to the sleeve,
• such that the coaxial screw gear sleeve mechanism is adapted to support in-vivo loads between the first member and the second member to maintain a normal height of the disc space following implantation of the device into the intervertebral disc space and during a time fusion occurs between vertebral bodies of the intervertebral disc space of the patient.

A distractible intervertebral body fusion device adapted for implantation into, and fusion of, an intervertebral disc space of a patient, comprising;

• a first bearing surface;
• a second bearing surface;
• and
• at least one coaxial screw gear sleeve mechanism disposed between the first bearing surface and the second bearing surface, the coaxial screw gear sleeve mechanism including:
• a threaded post projecting inwardly from one of the first bearing surface and the second bearing surface;
• and
• a corresponding sleeve having a threaded interior surface surrounding and mating with the threaded post and a helically geared exterior surface;
• wherein selective rotation of the sleeve causes an expansion of the first bearing surface relative to the second bearing surface due to a telescoping expansion resulting from the sleeve translating relative to one of the first bearing surface and the second bearing surface simultaneously with the threaded post translating relative to the sleeve, such that the coaxial screw gear sleeve mechanism is adapted to support in-vivo loads between the first bearing surface and the second bearing surface to maintain a normal height of the disc space following implantation of the device into the intervertebral disc space and during a time fusion occurs between vertebral bodies of the intervertebral disc space of the patient,
• wherein the threaded post is unitarily formed with the one of the first bearing surface and the second bearing surface.