WO2011136825A1

WO2011136825A1 - Insulated biocompatible shape memory otologic prostheses

Info

Publication number: WO2011136825A1
Application number: PCT/US2010/049235
Authority: WO
Inventors: Glenn Knox
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-04-29
Filing date: 2010-09-17
Publication date: 2011-11-03
Anticipated expiration: 2012-10-29
Also published as: EP2563276A1; EP2563276A4

Abstract

Embodiments of this invention have been disclosed and described. A nitinol piston that is surrounded by an insulating material and coated with gold will improves the prosthetic that is covered by the two prior patents, which are held by the same inventor. The insulating material will prevent the occurrence of a reaction to nickel or nickel toxicity and the gold coating will facilitate the heat conduction that is needed. It will be apparent to those skilled in the art that various modifications may be made to this invention without departing from the spirit of the invention.

Description

TITLE OF INVENTION

INSULATED BIOCOMPATIBLE SHAPE MEMORY OTOLOGIC PROSTHESES

CROSS REFERENCES TO RELATED APPLICATIONS

This application is an improvement of the Knox, U.S. Patent number 6,197,060 and Knox, U.S. patent number

6,554,861 patents that are held by this inventor.

BACKGROUND OF THE INVENTION

The present invention relates generally to otologic prosthesis and more particularly to a nitinol improved otologic prosthesis for relieving impaired connective hearing of the middle ear.

In the prior applications, Knox, U.S. Patent number 6,197,060 and Knox, U.S. patent number 6,554,861, the inventor had devised a method and a device by which a prosthetic device can be attached to a person' s incus in the person's middle ear. The prior applications do not teach an insulating material to protect the person from possible nickel toxicity.

This is an improvement over the prior art in that the nitinol improved otologic prosthesis is encased in a protective insulating material, which is partially coated in gold. This improvement would avoid the problem of an adverse reaction to nickel that can result in an inner ear infection . BRIEF DESCRIPTION OF THE INVENTION

The present invention is an improvement of the Nitinol Stapes prosthesis (^λ060 and ^λ181) patents that are owned by the current applicant. As discussed in the prior patents this device will be used with a stapedectomy, which is a microsurgical procedure in which all or part of the stapes is replaced by the prosthesis.

A critical part of the stapedectomy is attaching the prosthesis around the lenticular process of the incus due to its minuteness and delicate nature, typically about 3.5mm to 6mm long and 0.6mm to 0.8mm diameter.

The objects of the prior patents included conceiving a prosthetic device that could be installed more easily with more confidence resulting in fewer complications and better hearing results. The prior patents also claimed a device that is relatively simple in construction, utilizes state- of-the-art materials and which can be more easily

manipulated in the middle ear.

In order to better achieve these objects the

otologic prosthesis should be manufactured of biocompatible shape memory alloy that conducts sound vibration from the eardrum, through the inner ear to the oval window of the inner ear.

An object of this improvement device is to insure that the person does not suffer an adverse reaction to the implant. Some individuals may suffer from a nickel allergy and the construction of this device eliminates that

possibility. This is accomplished by encasing the nitinol, which is an alloy of titanium and nickel, completely in a protective insulating material such as plastic or other biocompatible material, except for a portion of the shaft, which is coated in gold.

With this type of protective layer the plastic and gold protect against nickel allergy or nickel sensitivity. Additionally the plastic protects against thermal injury while the gold allows the thermal energy to reach the nitinol without the nitinol being exposed to the body.

Additionally because heat must be transferred to the implant to secure it to the incus a coating of gold is applied to the implant. Gold has been chosen because it is an excellent conductor of heat.

Any material that is introduced to the body should not harm the body and likewise the body should not harm or reject the foreign material.

The use of nitinol encased in a protective insulating layer and coated with gold satisfies this particular object in this application. These particular improvements are not contemplated or taught by the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is an enlarged, fragmentary, partially broken- away, perspective view of a human ear having one embodiment of a otologic prosthesis according to the present

invention .

Figure 2 is an enlarged perspective view of the otologic prosthesis illustrated in Figure 1.

Figure 3A-3D are perspective views of the prosthesis embodiment of Figure 1, but showing it is various phases of installation on an incus process.

Figure 4 is an elevational view of another embodiment of an otologic prosthesis according to the present invention.

Figure 5 is an elevational view of a further embodiment of the otologic prosthesis according to the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The use of implants has given rise to the development of new material and new alloys that permit the implantation of prosthetic devices in the human body. In this

application the use of nitinol, which is an alloy of nickel and titanium, is used in this otologic prosthetic device.

A primary concern in the use of any implantable device or material is the compatibility of the device to the human body. The device should not be rejected by the body but at the same time should not harm the body.

Concern has arisen over the biocompatibility of nitinol specifically as it relates to the use of nitinol for an otologic prosthesis.

One investigation notes that nitinol allergy is quite common and can result in the patient developing a middle ear inflammation response possibly necessitating the removal of the prosthetic in a subsequent operation.

Another concern is the theoretical possibility of thermal injury to the incus. One complication of stapes surgery is neurosis of the incus, which is caused by the prosthetic device being secured too tightly around the incus. It is theoretically possible that heating the incus could also increase that risk.

Nitinol is formed by alloying nickel and titanium and is used as a shape memory alloy. This alloy has superelastic properties and because of that characteristic nitinol is an excellent choice of material for this

application. However, some individuals may suffer an adverse reaction to nickel and the construction of the device in this case eliminates that occurrence.

Although this application discusses nitinol in

relationship to implants for otologic prostheses and the particular concerns as they relate to otologic implants, nitinol is a well known material that has been used in stents, heart valve tools, bone anchors, staples and septal defect devices, to name a few medical applications.

The nitinol stapes prosthesis 10 is a middle ear implant comprised of an elongated shaft 11 of nickel- titanium (nitinol) wire alloy 18 having biocompatible shape-memory properties. The nitinol is completely encased in plastic 19 or other biocompatible material except for a small band of the shaft, which is coated in gold 17. On the shaft the plastic and gold should overlap namely by having a predetermined portion of the gold 17 encased in plastic 19. Overlapping the gold and plastic will help to insure the biocompatibility seal.

Figure 1 illustrates a human ear having an outer ear structure OE, and an inner ear structure IE. The middle ear ME is separated from the outer ear OE by the tympanic membrane T. The malleus M is connected to the tympanic membrane T, and the incus I is connected to the malleus.

The otologic prosthesis 10 illustrated in Figure 1 is used in a so-called stapedectomy. When it is installed, the otologic prosthesis 10 provides a sound-conductive connection between a first otologic structure, such as the incus process I and a second otologic structure, such as the oval window 0. When installed as illustrated,

vibrations from the incus process I are transmitted to the oval window 0 in the same manner as with a conventional prosthesis .

As described in the prior applications the prosthesis 10 has an upper, or outer, end portion 12 that is reversely turned on itself to form an open ended bight 13 prior to attachment to the incus. As manufactured, the prosthesis 10 has an overall length of about 4 mm, and the reversely turned bight has a radius of approximately 0.05 mm. The diameter of the wire shaft is approximately 0.005 mm. The bight 13 is adapted to engage the incus process I as illustrated in FIG. 3D in the manner to be discussed.

The prosthesis shaft has a lower, or inner, end portion 14 remote from the bight 13 and a fastening means as provided on this end portion for securing the shaft 11 to a second otologic structure, such as the oval window 0 shown in FIG. 3D. In the embodiment of FIG. 2 the fastening means includes a cylindrical piston 15 of plastic, such as polytetrafluoroethylene (PTFE) molded about the lower end of the shaft 11.

The bight 13 is opened by means of a tool to receive the incus process I and self-closes in response to heat to grip it. In order to accelerate the self closing action, a heat sink flange 20 is provided on the shaft 11 between the bight 13 and the piston 15.

In the illustrated embodiment of Figure 2, the heat sink flange 20 is provided by a flat metal plate which is preferably disposed in a plane transverse to the plane in which the bight 13 is formed, such as orthogonal to the plane of the bight 13. The heat sink flange 20 is secured to the shaft 11 as by welding. Thus, the heat sink flange 20 is disposed with its surface area readily exposed to the surgeon for receiving electromagnetic energy, such as may be applied by means of the laser beam customarily used in stapedectomies .

When struck by a laser beam, the heat sink flange 20 conducts heat upwardly along the shaft to the bight 13 causing it to reversely turn on itself into its as

manufactured condition for gripping the incus process as illustrated in FIG. 3D. The heat sink flange 20 is also large relative to the shaft 11 to provide a readily visible target for the surgeon to aim the laser beam.

The preferred embodiment has a core of nitinol 18 in the shaft of the device. The entire implant except a gold band 17 near the bottom of the implant is also encased in an insulating material 19 such as flexible ceramic or polyethylene and a portion of the device is coated in gold including the gold band 17 near the bottom of the device. Because the nitinol 18 is encased in an insulating material 19, the likelihood of the person suffering an allergic reaction to nickel is diminished substantially because there is no direct contact of the nitinol to the human person .

A portion of the insulating material 19 is coated with gold and the gold band 17 is used to conduct the heat from the laser in order for the bight 13 to attach to the incus near the bottom of the incus. As in the prior patents the gold band 17 may possess flanges 20 in one embodiment, which would facilitate targeting by a laser or heating element. The gold conducts the heat to the nitinol core activating the shape memory. Gold is selected because it is an excellent conductor and possesses excellent

biocompatibility characteristics .

The insulating material is flexible and bends with the nitinol when the nitinol is heated. The insulator is in contact with the incus of the ear in one embodiment. The insulator 19 bonds with the nitinol but keeps the open heat from reaching the incus and thus preventing thermal injury to the ear. The entire prosthetic is coated with inert biocompatible material thus preventing allergic reactions to nickel as well as any nickel toxicity.

While the preferred embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that various modifications may be made in these embodiments without departing from the spirit of the invention. For that reason the common scope of the invention is set forth in the following claims.

Claims

CLAIMS The inventor claims:

1. A self-securing otologic prosthesis, comprising: an elongated shaft formed of biocompatible shape memory alloy; said biocompatible shape memory alloy is encased in an insulating material; one end of said shaft having a reversely turned end portion forming a first bight; said first bight capable of being deformed for receiving a first otologic structure and upon application of heat closing into gripping

engagement with said first otologic structure, and fastening means on an opposite end of said shaft remote from said first bight for operatively engaging a second otologic structure; a portion of said prosthesis is coated with gold.

2. The self securing otologic prosthesis according to claim 1 including a flange on said shaft

providing a heat sink for enabling heat to be transferred by conduction to said first bight after engagement with said first otologic structure.

3. The self-securing otologic prosthesis according to claim 1 wherein the small diameter nickel titanium metal alloy wire is encased in an insulating material which is coated.

4. The self-securing otologic prosthesis according to claim 1 wherein said fastening means includes an enlarged cylindrical body.

5. The self-securing otologic prosthesis according to claim 4 wherein said cylindrical body has a circular end portion and is of a biocompatible plastic .

6. The self-securing otologic prosthesis according to claim 1 wherein said fastener means is provided by a closed loop formed integral with said shaft.

7. The self securing otologic prosthesis according to claim 1 wherein said fastener means includes a second bight lying in a plane transverse to the plane of said first bight.

8. The self securing otologic prosthesis according to claim 1 wherein said shaft mounts a heat sink flange in a plane transverse to the plane of the first bight for receiving electromagnetic

radiation .

9. The self securing otologic prosthesis according to claim 1 wherein said first otologic structure is an incus, said first bight is formed to attach to said incus, said second otologic structure is an oval window, and said fastening means is formed to operatively engage said window.

10. The self-securing otologic prosthesis according to claim 1 wherein said first otologic structure is an incus, said first bight is formed to attach to said incus, said second otologic structure is a stapes, and said fastening means is formed to operatively engage said stapes.

11. The self-securing prosthesis according to claim 1 wherein said first otologic structure is an incus, said first bight is formed to attach to said incus, said second otologic structure is a stapes

footplate, and said fastening means is formed to operatively engage said stapes footplate.

12. The self-securing prosthesis according to claim 1 wherein said first otologic structure is a malleus, said first otologic structure is an oval window, and said fastening means is formed to operatively engage said window.

13. The self-securing prosthesis according to claim 1 wherein said first otologic structure is a malleus, said first bight is formed to attach to said malleus, said second otologic structure is a stapes footplate, and said fastening means is formed to operatively engage said stapes footplate.

14. The self-securing prosthesis according to claim 1 wherein said first otologic structure is a

malleus, said first bight is formed to attach to said malleus, said second otologic structure is a stapes, and said fastening means is formed to operatively engage said stapes.

15. The self-securing prosthesis according to claim 1 wherein the insulating material is ceramic.

16. The self-securing prosthesis according to claim 1 wherein the insulating material is polyethylene.

17. The self-securing prosthesis according to claim 1 wherein the insulating material is flexible.