Bone cement reinforcement and method

• US 4,735,625 A
• Filed: 09/11/1985
• Issued: 04/05/1988
• Est. Priority Date: 09/11/1985
• Status: Expired due to Fees

• Current Assignee: Smith & Nephew Richards Incorporated (Smith & Nephew PLC)
• Original Assignee: Richards Medical Company
• Inventors: Davidson, James A.
• Primary Examiner(s): Apley, Richard J.
• Assistant Examiner(s): Cannon, Alan W.
• Application Number:
  US06/775,012
• Time in Patent Office: 937 Days
• Field of Search: 623/16, 623/22, 623/23, 128/92, 128/92 W, 428/902, 526/348.1
• US Class Current: 623/23.62
• CPC Class Codes: A61B 17/8802 Equipment for handling bone cement or other fluid fillers
• CPC Class Codes: A61F 2/30907 Nets or sleeves applied to surface of prostheses or in cement
• CPC Class Codes: A61F 2/30965 Reinforcing the prosthesis by embedding particles or fibres during moulding or dipping
• CPC Class Codes: A61F 2/3662 Femoral shafts
• CPC Class Codes: A61F 2002/30084 Materials having a crystalline structure
• CPC Class Codes: A61F 2002/30909 Nets
• CPC Class Codes: A61F 2002/30919 Sleeves
• CPC Class Codes: A61F 2002/3631 with an integral complete or partial peripheral collar or bearing shoulder at its base
• CPC Class Codes: A61F 2002/4631 the prosthesis being specially adapted for being cemented
• CPC Class Codes: A61F 2310/00952 Coating, pre-coating or prosthesis-covering structure made of bone cement, e.g. pre-applied PMMA cement mantle

Abstract

A reinforcing technique for bone cement used in the anchoring of prosthetic devices. The reinforced bone cement includes oriented reinforcement formed of a continuous fiber-like material that is embedded in the bone cement between at least a portion of the outer surface of the prosthetic device and the surrounding bone that defines the cavity in which the device is implanted. The reinforcement is preferably a polymeric mat embedded in a thin layer of bone cement forming a precoat on the outer surface of the implant.

Claims

1. A prosthetic device with a reinforced composite precoat, comprising:

a. a prosthetic device adapted to have at least a portion implanted in a cavity formed in animal bone;

b. a relatively thin layer of cured bone cement precoated on the outer surface of the prosthetic device before implantation on at least part of the portion adapted to be implanted in the bone cavity; and

c. a reinforcing fibrous mat formed of high strength polyolefin fibers encapsulated within the cured bone cement precoating so that the fibers define a reinforcement to the cured bone cement layer prior to implantation, the fibers being oriented in at least one direction and interconnected to form a flexible network; and

d. the precoating outer layer defining a cured bone cement surface covering the fibers to provide a generally smooth outer layer so that the cured bone cement surface can be used to cary wet cement for forming a bond between the precoat and the animal bone.

2. The invention of claim 1, wherein the layer of bone cement is about 1-2 mm thick.

3. The invention of claim 1, wherein the fibers are formed of polyethylene, having a weight average molecular weight at least about 500,000, with a tenacity of at least about 20 g/denier, a tensile modulus at least about 500 g/denier, a creep value no more than bout 5% (when measured at 10% of breaking load for 50 days at 23°

C.), a porosity less than about 10% and a main melting temperature of at least 147°

C. (measured to 10°

C./min. heating rate by differential scanning calorimetry).

4. The invention of claim 1 wherein the fibers are formed of polyethylene being of a weight average molecular weight of at least about 1,000,000 and having a tensile modulus of at least about 1600 g/denier, a main melting temperature of at least about 147°

C. (measured at 10°

C./minute heating rate by differential scanning calorimetry) and an elongation-to-break of not more than 5%.

5. The invention of claim 1 wherein the fibers are formed of polypropylene being of a weight average molecular weight of at least about 750,000 and having a tenacity of at least about 8 g/denier, a tensile modulus of at least about 160 g/denier and a main melting temperature of at least about 168°

C. (measured at 10°

C./minute heating rate by differential scanning calorimetry).

6. The invention of claim 1 wherein the mat is formed of a blend of polyethylene and polypropylene fibers.

7. The invention of claim 1 wherein the fibers are formed into threads that are oriented in two general directions and woven together.

8. The invention of claim 1 wherein the mat is formed as a sock that is sized and shaped to fit over an elongated portion of a prosthesis.

9. The invention of claim 1 wherein the mat is formed rectilinear in shape.

10. The invention of claim 1, wherein the mat is impregnated with the bone cement.

11. The invention of claim 1, wherein the mat is bonded to the prosthetic device by first applying a first layer of bone cement to the device, placing the mat on the cement, and applying sufficient bone cement to the mat to bond with the first layer of cement through the fibers.

12. The invention of claim 1, wherein the mat is formed as a sock that is sized and shapted to fit over an elongated portion of the prosthesis.

13. The device of claim 1, further including a coating of a material on the outer surface of the precoat that is capable of becoming biologically attached to surrounding bone.

14. The device of claim 13, wherein the coating is formed of hydroxylapatite.