Spinal fixator

• US 5,658,335 A
• Filed: 03/09/1995
• Issued: 08/19/1997
• Est. Priority Date: 03/09/1995
• Status: Expired due to Fees

• Current Assignee: Cohort Medical Products Group Incorporated, The Ronald Charles Allan Living Trust
• Original Assignee: Cohort Medical Products Group Incorporated
• Inventors: Allen, Ronald C.
• Primary Examiner(s): JONES, MARYBETH O
• Application Number:
  US08/401,212
• Time in Patent Office: 894 Days
• Field of Search: 623/16, 623/17, 623/18, 606/60, 606/61, 606/62, 606/63, 606/64
• US Class Current: 623/17.16
• CPC Class Codes: A61B 17/8875 Screwdrivers, spanners or wrenches
• CPC Class Codes: A61F 2/44 for the spine, e.g. vertebrae, spinal discs
• 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 2002/30112 Rounded shapes, e.g. with rounded corners
• CPC Class Codes: A61F 2002/30143 hexagonal
• CPC Class Codes: A61F 2002/30153 rectangular
• CPC Class Codes: A61F 2002/30261 parallelepipedal
• CPC Class Codes: A61F 2002/30329 Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2002/30332 Conically- or frustoconically-shaped protrusion and recess
• CPC Class Codes: A61F 2002/30387 Dovetail connection
• CPC Class Codes: A61F 2002/30398 Sliding
• CPC Class Codes: A61F 2002/304 with additional means for limiting said sliding
• 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 2002/3055 for adjusting length
• CPC Class Codes: A61F 2002/30579 with mechanically expandable devices, e.g. fixation devices
• CPC Class Codes: A61F 2002/30616 Sets comprising a plurality of prosthetic parts of different sizes or orientations
• CPC Class Codes: A61F 2002/30706 specially designed for children, e.g. having means for adjusting to their growth
• CPC Class Codes: A61F 2002/30772 Apertures or holes, e.g. of circular cross section
• CPC Class Codes: A61F 2002/30774 : internally-threaded
• CPC Class Codes: A61F 2002/30841 : Sharp anchoring protrusions for impaction into the bone, e.g. sharp pins, spikes
• CPC Class Codes: A61F 2002/4627 : with linear motion along or rotating motion about the instrument axis or the implantation direction, e.g. telescopic, along a guiding rod, screwing inside the instrument
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2220/0033 : made by longitudinally pushing a protrusion into a complementary-shaped recess, e.g. held by friction fit
• CPC Class Codes: A61F 2220/0041 : using additional screws, bolts, dowels or rivets, e.g. connecting screws
• CPC Class Codes: A61F 2230/0004 : Rounded shapes, e.g. with rounded corners
• CPC Class Codes: A61F 2230/0017 : Angular shapes
• CPC Class Codes: A61F 2230/0019 : rectangular
• CPC Class Codes: A61F 2230/0082 : parallelepipedal
• CPC Class Codes: A61F 2250/0082 : specially designed for children, e.g. having means for adjusting to their growth
• 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

An adjustable spinal fixator for insertion between adjacent vertebrae comprises a contoured housing defining convex edges to fit within the concavity of the vertebral body. An externally threaded core extends through the housing, and a pair of internally threaded nut assemblies attach to the core member. Four crown members with teeth are separately mounted within the housing and retract and variably extend with the movement of the movable nuts on the core member. Two of the crown members extend and retract from the top of the housing, and the remaining two crown members extend and retract from the bottom of the housing. The spinal fixator is positioned between adjacent vertebrae with the crown members retracted so that the teeth are below the convex edges of the housing. Following placement, the crown members are extended outwardly from the top and bottom of the housing by rotation of the core member which causes the teeth to penetrate the bone at an angle to secure the spinal fixator in position. Preferably, a bone graft surrounds the implanted spinal fixator which defines apertures for bony ingrowth. Several sizes of spinal fixators exist to accommodate differing anatomies of the spine.

Claims

1. A bone immobilization device for connecting bone to bone comprising:

housing means defining a perimeter;

at least two, separate crown means mounted inside the perimeter of the housing means, each crown means defining at least one outwardly extending tooth means; and

means including a core member extending through the housing means and having nut means movably attached to external threads thereon for retracting the at least two, separate crown means inside the perimeter and for extending the at least two, separate crown means outside the perimeter, the at least one tooth means adapted to penetrate bone.

2. The immobilization device of claim 1 wherein the nut means comprises means for mounting the at least two separate crown means, rotation of the core member causing the nut means to move on the external threads to retract into the housing means and move the at least two separate crown means beyond the perimeter, further rotation of the core member causing the nut means to move on the external threads beyond the perimeter to allow the at least two separate crown means to retract inside the perimeter.

3. The immobilization device of claim 2 wherein the external threads on the core member are separated into two, oppositely wound portions, and the core member defines an aperture for insertion of a tool for rotation of the core member.