Femoral head resurfacing apparatus and methods

• US 7,241,315 B2
• Filed: 09/09/2004
• Issued: 07/10/2007
• Est. Priority Date: 07/23/2001
• Status: Expired due to Fees

• Current Assignee: Robert Evans
• Original Assignee: Robert Evans
• Inventors: Evans, Robert
• Primary Examiner(s): Rodriguez; Cris
• Assistant Examiner(s): STOKES, CANDICE CAPRI
• Application Number:
  US10/937,047
• Publication Number:
  US 20050033447A1
• Time in Patent Office: 1,034 Days
• Field of Search: 623/23.12, 623/23.14, 623/23.11, 623/22.11, 623/23.13, 623/22.23
• US Class Current: 623/23.12
• CPC Class Codes: A61B 17/175 for preparing the femur for hip prosthesis insertion
• CPC Class Codes: A61B 17/86 Pins or screws or threaded wires; nuts therefor A61B17/72 take precedence
• CPC Class Codes: A61B 17/8625 Shanks, i.e. parts contacting bone tissue
• CPC Class Codes: A61B 2090/062 penetration depth
• CPC Class Codes: A61F 2/30767 Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
• CPC Class Codes: A61F 2/3603 implanted without ablation of the whole natural femoral head endoprosthetic cartilage A61F2/30756
• CPC Class Codes: A61F 2/4637 for connecting or disconnecting two parts of a prosthesis
• CPC Class Codes: A61F 2/4657 Measuring instruments used for implanting artificial joints for surgical instruments A61B90/06
• CPC Class Codes: A61F 2/4684 Trial or dummy prostheses
• CPC Class Codes: A61F 2002/30112 Rounded shapes, e.g. with rounded corners
• CPC Class Codes: A61F 2002/30153 rectangular
• CPC Class Codes: A61F 2002/30433 using additional screws, bolts, dowels, rivets or washers e.g. connecting screws
• CPC Class Codes: A61F 2002/30505 spring biased
• CPC Class Codes: A61F 2002/30517 using a locking plate
• CPC Class Codes: A61F 2002/30563 having elastic means or damping means, different from springs, e.g. including an elastomeric core or shock absorbers
• CPC Class Codes: A61F 2002/30565 having spring elements
• CPC Class Codes: A61F 2002/30571 Leaf springs
• CPC Class Codes: A61F 2002/30578 having apertures, e.g. for receiving fixation screws
• CPC Class Codes: A61F 2002/30685 Means for reducing or preventing the generation of wear particulates
• CPC Class Codes: A61F 2002/30797 internally-threaded
• CPC Class Codes: A61F 2002/30828 : parallel
• CPC Class Codes: A61F 2002/30878 : with non-sharp protrusions, for instance contacting the bone for anchoring, e.g. keels, pegs, pins, posts, shanks, stems, struts
• CPC Class Codes: A61F 2002/30879 : Ribs
• CPC Class Codes: A61F 2002/4641 : for disconnecting
• CPC Class Codes: A61F 2002/4662 : for measuring penetration depth
• 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 2230/0004 : Rounded shapes, e.g. with rounded corners
• CPC Class Codes: A61F 2230/0019 : rectangular
• CPC Class Codes: A61F 2310/00017 : Iron- or Fe-based alloys, e.g. stainless steel
• CPC Class Codes: A61F 2310/00029 : Cobalt-based alloys, e.g. Co-Cr alloys or Vitallium
• CPC Class Codes: A61F 2310/00796 : Coating or prosthesis-covering structure made of a phosphorus-containing compound, e.g. hydroxy(l)apatite

Abstract

A femoral head resurfacing apparatus includes a cap of hemispherical shape and stabilization structure (e.g., one or more non-shear fixation bars) that inserts into slots cut into the femoral head, so that the cap remains substantially immovable other than due northerly. A method of resurfacing the femoral head of a hip joint includes removing longitudinal slots or holes of bone in the femoral head, and attaching a hemispherical cap to the head, the cap having non-shear fixation bars or other stabilizing structure for mating engagement with the slots or holes.

Claims

1. Femoral head resurfacing apparatus, comprising

(a) a cap having a substantially hemispherical shape of substantially uniform thickness;

and

(b) a plurality of non-shear fixation bars, the non-shear fixation bars comprising a plurality of gear shaped teeth to encourage bone ingrowth between the teeth, an equatorial end of each non-shear fixation bar forming a hole configured to accept a screw for attaching mounting hardware to couple the cap with the femoral head.

2. Apparatus of claim 1, an inner surface of the cap and the sides of the non-shear bars comprising hydroxyapatite porocast to provide and promote bone ingrowth-penetration into the cap to facilitate additional fixation of the cap to the femoral head.

3. Apparatus of claim 1, the cap being sized to minimize bone removal from the femoral head.

4. Apparatus of claim 1, further comprising the mounting hardware, the mounting hardware comprising one or more spring loaded absorption fixators, each fixator attaching to one of the non-shear fixation bars using the screw.

5. Apparatus of claim 1, further comprising a plurality of bone screws each having threads notched in equidistant spots from the screw head down about 70% of the length of each screw.

6. Femoral head resurfacing apparatus, comprising

(a) a cap having a substantially hemispherical shape of substantially uniform thickness, the cap configured to interface with a metal cup socket maintaining a clearance tolerance of 0.01 mm;

and

(b) a plurality of non-shear fixation bars for insertion into respective longitudinal slots cut into the femoral head, an equatorial end of each non-shear fixation bar forming a hole configured to accept a screw for attaching mounting hardware to couple the cap with the femoral head.

7. Femoral head resurfacing apparatus, comprising

(a) a cap having a substantially hemispherical shape of substantially uniform thickness;

the cap being fixed by a plurality of metal spring loaded absorption fixators, each fixator being screwed into the cap and femoral head, to prevent loosening of the cap and

(b) a plurality of non-shear fixation bars for insertion into respective longitudinal slots cut into the femoral head, wherein the cap remains substantially immovable other than due northerly.

8. Apparatus of claim 7, the spring loaded absorption fixators having ability to flex and absorb forces and stress similar to the way bone flexes.

9. Apparatus of claim 7, a southerly end of the spring loaded absorption fixators being compressed when screwed into the femoral head to deliver a force to the cap while fixed to the femoral head.

10. Apparatus of claim 7, the spring loaded absorption fixator comprising anti-back out locking means.

11. Apparatus of claim 10, the anti-back out locking means being removable by a surgeon by use of a pointed stylus instrument.

12. A method of resurfacing the femoral head of a hip joint, comprising the steps of:

removing a plurality of longitudinal slots of bone in the femoral head; and

attaching a hemispherical cap to the head, the cap forming a plurality of non-shear fixation bars for mating engagement with the slots.

13. The method of claim 12, wherein the step of attaching comprises utilizing a plurality of metal spring loaded absorption fixators, and further comprising screwing each of the fixators to the cap and to the femoral head.

14. A femoral head resurfacing cap, comprising:

a hollow cap to mate with a plurality of longitudinal slots within a femoral head of the hip joint, the cap forming non-shear bars for mating engagement with the slots; and

a plurality of spring-loaded absorption fixators for attaching the cap to the head.

15. The femoral head resurfacing cap of claim 14, further comprising a plurality of screws, each of the screws coupling one of the fixators to the cap and the head.

16. The femoral head resurfacing cap of claim 14, wherein the fixators comprise hydroxyapatite porocast to facilitate bone growth attachment to the fixators.

17. The femoral head resurfacing cap of claim 14, wherein the cap forms a hollow interior hemisphere surface to accommodate the head, the cap further comprising hydroxyapatite porocast to facilitate bone growth attachment to the cap.

18. A method for capping a femoral head with a shell, comprising the steps of:

inserting a centering device in a centering hole of the femoral head;

drilling a plurality of holes about the centering hole, a diameter of the holes being from between about 3 mm to 12 mm, a depth of the holes being about 6 mm; and

inserting fin-like dowels, which are a part of a centering hole post, into the holes to prevent migration of the shell.