Methods and Apparatuses for Vertebral Body Distraction and Fusion Employing a Coaxial Screw Gear Sleeve Mechanism

An expandable medical device, comprising:

• a first outer member;
• a second outer member;
• and
• at least one coaxial screw gear sleeve mechanism disposed between the first outer member and the second outer member, the coaxial screw gear sleeve mechanism including:
• a threaded post projecting inwardly from one of the first outer member and the second outer member;
• 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 outer member with respect to the second outer member due to a telescoping expansion resulting from the sleeve translating relative to one of the first outer member and the second outer member simultaneously with the threaded post translating relative to the sleeve.

A size-adjustable medical device, comprising:

• a first outer member;
• a second outer 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 outer member relative to the second outer member due to a telescoping expansion of the sleeve translating relative to one of the first outer member and the second outer member simultaneously with the other of the first outer member and the second outer member translating relative to the sleeve.

A size-adjustable medical device, comprising:

• a first member;
• a second member;
• and
• a size-adjustable support engaging the first and second members to provide an adjustable separation distance between the first and second members, the support comprising commonly-actuated, coaxial first and second axially rotatable joints to provide the adjustable separation distance, wherein the support comprises a first sleeve member and a second sleeve member each including a helical external thread including a plurality of superimposed teeth and an internal thread,
• wherein the first sleeve member is rotationally mounted in a first threaded lumen within the first member and the second sleeve member is rotationally mounted in a second, substantially parallel threaded lumen within the first member, and
• wherein actuating the first and second axially rotatable joints expands the implant into an expanded configuration.