Expandable prosthesis for spinal fusion

A spine stabilizing prosthesis for insertion between respective facing surfaces of respective vertebral portions above and below a cavity caused by removal of a portion of vertebra comprising:

• first and second bearing portions having respective remote, outer ends and respective adjacent inner ends;
• said respective remote, outer ends being formed with respective first and second rings of teeth for bearing against said respective facing surfaces;
• jacking screw adjustment means rotatively interconnecting respective adjacent inner ends of respective bearing portions so that said bearing portions and said jacking screw adjustment means can be rotated relatively about a ring axis to adjust separation of said bearing portions to bridge the cavity;
• said teeth having ramp surfaces permitting sliding engagement with said facing surfaces in one rotational direction and biting into said surfaces in an opposite rotational direction;
• and,
• said jacking screw adjustment means comprising a single shaft having a medial, tool engageable portion and opposite ends formed with respective threads which are opposite, complementary opposite threads being formed on said first and said second bearing portions, so that, with the prosthesis inserted in the cavity with bearing portions aligned with respective facing surfaces, at least one of the bearing portions can be rotated in a first sense relative to the shaft to increase the axial length of the prosthesis until spanning the cavity with the rings of teeth in sliding engagement with respective surfaces and the tool engageable portion then rotated in an opposite sense to urge the bearing portions further apart and thereby drive the teeth into anchoring engagement with the respective surfaces.