Expandable prosthesis for spinal fusion

• US 5,702,455 A
• Filed: 07/03/1996
• Issued: 12/30/1997
• Est. Priority Date: 07/03/1996
• Status: Expired due to Fees

• Current Assignee: Rahul Saggar
• Original Assignee: Rahul Saggar
• Inventors: Saggar, Rahul
• Primary Examiner(s): Weiss, John G.
• Assistant Examiner(s): Black, John M.
• Application Number:
  US08/684,770
• Time in Patent Office: 545 Days
• Field of Search: 623/17, 606/61
• US Class Current: 623/17.15
• CPC Class Codes: A61B 17/0642 for bones, e.g. for osteosynthesis or connecting tendon to bone
• CPC Class Codes: A61B 17/70 Spinal positioners or stabilisers ; Bone stabilisers comprising fluid filler in an implant
• CPC Class Codes: A61B 2017/0647 having one single leg, e.g. tacks
• CPC Class Codes: A61F 2/30744 End caps, e.g. for closing an endoprosthetic cavity
• CPC Class Codes: A61F 2/44 for the spine, e.g. vertebrae, spinal discs
• CPC Class Codes: A61F 2/4465 having a circular or kidney shaped cross-section substantially perpendicular to the axis of the spine
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2002/2835 Bone graft implants for filling a bony defect or an endoprosthesis cavity, e.g. by synthetic material or biological material
• CPC Class Codes: A61F 2002/30146 octagonal
• CPC Class Codes: A61F 2002/30235 tubular, e.g. sleeves
• CPC Class Codes: A61F 2002/30405 made by screwing complementary threads machined on the parts themselves
• CPC Class Codes: A61F 2002/30411 having two threaded end parts connected by a threaded central part with opposite threads at its opposite ends, i.e. for adjusting the distance between both end parts by rotating the central part
• CPC Class Codes: A61F 2002/30433 using additional screws, bolts, dowels, rivets or washers e.g. connecting screws
• CPC Class Codes: A61F 2002/30507 using a threaded locking member, e.g. a locking screw or a set screw
• CPC Class Codes: A61F 2002/3055 for adjusting length
• CPC Class Codes: A61F 2002/30593 hollow
• CPC Class Codes: A61F 2002/30601 telescopic
• CPC Class Codes: A61F 2002/30774 internally-threaded
• CPC Class Codes: A61F 2002/30785 parallel
• CPC Class Codes: A61F 2002/30787 inclined obliquely with respect to each other
• CPC Class Codes: A61F 2002/30789 : perpendicular with respect to each other
• CPC Class Codes: A61F 2002/30818 : castellated or crenellated
• CPC Class Codes: A61F 2002/30841 : Sharp anchoring protrusions for impaction into the bone, e.g. sharp pins, spikes
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2220/0041 : using additional screws, bolts, dowels or rivets, e.g. connecting screws
• CPC Class Codes: A61F 2230/0017 : Angular shapes
• CPC Class Codes: A61F 2230/0069 : cylindrical
• CPC Class Codes: A61F 2310/00017 : Iron- or Fe-based alloys, e.g. stainless steel
• CPC Class Codes: A61F 2310/00023 : Titanium or titanium-based alloys, e.g. Ti-Ni alloys

Abstract

A spine stabilizing prosthesis has first and second hollow, cylindrical bearing members interconnected by a hollow, cylindrical jacking screw adjustable to expand the prosthesis within a cavity to bridge respective opposite axial ends of the bearing members into pressure engagement with opposing vertebral faces. Walls of the bearing members are perforated by a plurality of bone fragment admitting apertures and forming a bone fragment receptacle so that bone can grow and fuse completely through said bearing members when the prosthesis is installed in the cavity. Respective axial ends of the bearing members are formed with rings of vertebrae engaging teeth having ramp surfaces permitting sliding engagement when rotated in one direction and biting into the facing surfaces when rotated in the opposite direction resisting rotation to permit further expansion apart of the bearing members by rotation of the jacking screw.

Claims

1. 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 members having respective remote, outer ends for bearing against said respective facing surfaces and respective adjacent inner ends;

jacking screw adjustment means rotatively interconnecting respective adjacent inner ends of respective bearing members for relative rotation to adjust separation of said bearing members to bridge the cavity;

said jacking screw adjustment means comprises a single tubular shaft having a medial, tool engageable portion and opposite open ends formed with respective threads which are opposite, complementary opposite threads being formed on said first and said second bearing portions; and

,

said bearing members having tubular, axially extending walls perforated by a plurality of bone fragment admitting apertures forming a bone fragment receptacle so that bone can grow and fuse through said bearing members and said tubular shaft when the prosthesis is installed in the cavity.

2. A prosthesis according to claim 1 wherein, said respective remote, outer ends are formed with respective first and second rings of teeth for bearing against said respective facing surfaces, said teeth having ramp surfaces permitting sliding engagement with said facing surfaces when a respective bearing member is rotated in one rotational direction and biting into said facing surfaces when rotated in an opposite rotational direction.

3. 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.

4. A prosthesis according to claim 3 wherein, said shaft is tubular.