GB2275422A

GB2275422A - Artificial auditory ossicle

Info

Publication number: GB2275422A
Application number: GB9403283A
Authority: GB
Inventors: Yukio Taniguchi; Yasuo Hosoda
Original assignee: Asahi Kogaku Kogyo Co Ltd
Current assignee: Pentax Corp
Priority date: 1993-02-26
Filing date: 1994-02-21
Publication date: 1994-08-31
Also published as: GB9403283D0; DE4406081A1

Description

2275422 ARTIFICIAL AUDITORY OSSICLE The present invention relates to an

artificial auditory ossicle which is adapted to reconstruct an ossicular chain which has been damaged by disease or trauma, etc.

As is well known, in the event of chronic otitis media or an injured auris media, a tympanoplasty is performed to reconstruct the conductive mechanism of the middle ear.

Hitherto, tympanoplastic procedure has utilized a preserved homologous bone or a piece of cartilage in the reconstruction of the damaged ossicular chain. A variation of the procedure employs an artificial auditory ossicle in place of the homologous preserved bone or cartilage. Two types of artificial auditory ossicles have been used in the reconstructive process. The type used depends upon the severity of damage to the ossicular chain. The first is a partial substitution type in which the artificial auditory ossicle is adapted to bridge an eardrum and a stapes (i.e., stirrup)'. The second is an entire substitution type in which the artificial auditory ossicle is adapted to directly connect an eardrum arid a base of the stapes. The former type is utilized when the stapes is present and has not been injured. In the event that the stapes is absent, or only partially existing (i.e., when only the base of the stapes is present), the second type of artificial auditory ossicle is used.

Artificial auditory ossicles of metal or plastic construction have been frequently used. However, artificial auditory ossicles of ceramic construction have come into wider use due to their stability within an organism. Among the possible ceramics which can be used, hydroxyapatite is particularly advantageous in that hydroxyapatite has a high organic compatibility and is easily machined. Indeed, hydroxyapatite artificial auditory ossicles have been marketed with much success.

Two tympanoplastic procedures may be performed. In the first procedure. the eardrum is directly connected to the artificial auditory ossicle. In the second procedure, the eardrum is connected to the artificial auditory ossicle through a piece of cartilage. In the first procedure, however, it is quite possible that the artificial auditory ossicle becomes detached after the operation is completed. Recent statistics have shown that the second procedure proves to be much more successful than the first.

Nevertheless, in the second procedure, the possibility still exists that the cartilage piece provided between the eardrum and the artificial auditory ossicle will accidentally deviate from its intended position. To prevent this from occurring, it is known to adhere the piece of cartilage to the artificial auditory ossicle with an adhesive that is specially prepared for adhering living tissues. However, all such adhesives are toxic to some extent. It follows that use of such adhesives should be avoided if possible. Responsive to this problem of adhesives in hitherto known tympanoplastic procedures, the auditory ossicle has been ground, for example, by a diamond disc to adjust the length thereof. The modification allows for a flush arrangement of the auditory ossicle within the damaged portion of the ossicular chain. In practice, however, it is very difficult for a surgeon to position the auditory ossicle in a flush manner. The adjustment is time-consuming and troublesome to the surgeon.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art by providing an artificial auditory ossicle which can be immovably secured to an associated cartilage piece without the 'need-for an adhesive.

According to the present invention an artificial ossicle is provided for utilization in a tympanoplasty as a substitute for a part or whole of an auditory ossicle chain connecting an eardrum and an auris interna. The artificial auditory ossicle. includes a head portion having a planar surface in contact with a piece of cartilage which is positioned on the eardrum, a shank portion connected to the head portion and extending in a direction substantially perpendicular to the planar surface of the head portion, and a projection connected to the head portion and extending in a direction opposite to the shank portion to penetrate the cartilage piece.

According to another aspect of the present invention, an artificial auditory ossicle is provided which includes a head portion in the shape of a disc, a shank portion connected to the head portion and extending in a direction substantially perpendicular to the head portion, and a projection connected to the head portion and extending in a direction opposite to the shank portion.

Preferably, the projection of the artificial auditory ossicle has a cylindrical shape with a sharp tip at one end. It is also preferred that the tip is conical in shape so that it can easily pierce the cartilage. A projection having a diameter which gradually increases towards the tip end before tapering off to a point is preferred to a projection with a straight cylindrical shape which tapers off to a point. A projection having this shape will resist detachment of the auditory ossicle from the piece of cartilage.

The artificial auditory ossicle according to the present invention can be made of any material compatible with a living organism. For example, a metal or metal alloy, such as titanium, a titanium alloy, or stainless steel; a high polymer such as high density polyethylene or fluorinated ethylene resin; or a ceramic such as alumina, zirconia, apatite, tricalcium phosphate, or an organic glass, etc., can be used for the artificial auditory ossicle. It is a well known fact within the medical society that a ceramic, particularly hydroxyapatite, which is a calcium phosphate series compound is homologous to a main inorganic component in a living organism and, accordingly, exhibits high compatibility with living tissue.

Moreover, ceramic can be easily ground by a diamond bar to adjust the size or shape thereof.

The artificial auditory ossicle must have sufficient mechanical strength to avoid being broken during machining (i.e., grinding) or when inserted into the damaged portion of the -ossicular chain during the operation. In view of this, it is preferable that the ceramic have a high d ensity. To this end, a densely sintered body having a relative density above 95 % (preferably above 98%) is preferred. If the relative density is below 95 %, the sintered body will have pores, resulting in an insufficient mechanical strength. The high density structure also provides a good conductive function.

The manner in which the artificial auditory ossicle of the present invention is produced is not limited to any specific procedure. Namely, the artificial auditory ossicle, according to the present invention, can be produced using any of a variety of procedures. An example of a procedure in which an artificial auditory ossicle of hydroxyapatite ceramic is produced is outlined below.

A slurry of hydroxyapatite is obtained from phosphate and a calcium salt in a known wet method. The hydroxyapatite slurry thus obtained is dried by a rotary drum type of drier to produce a hydroxyapatite powder. The hydroxyapatite powder is press molded into an auditory ossicle having a desired shape by, for example, a dry type hydrostatic press. The auditory ossicle molding thus obtained is then baked in an electric furnace at 1000 OG to 2000 c to obtain an artificial auditory ossicle.

Alternatively, it is possible to produce the artificial auditory- ossicle by casting the slurry or by injection molding, etc. It is also possible to prepare a green compact which is then machined by a lathe into a desired 7 shape.

There is no particular method for forming the projection which must be followed. Preferably, the projection, which is relatively small, is integrally formed with the head portion.

An example of the present invention will be described below in detail with reference to the accompanying drawings, in which;- Fig. 1 is a side elevational view of a partial substitution type artificial auditory ossicle of one embodiment of the present invention; Fig. 2 is a side elevational view of an entire substitution type artificial auditory ossicle of another embodiment of the present invention; Fig. 3 is a side elevational view of a partial substitution type artificial auditory ossicle of still another embodiment of the present invention; Fig. 4 is a side elevational view of an entire substitution type artificial auditory ossicle of yet another embodiment of the present invention; and Fig. 5 is an explanatory view of an artificial auditory ossicle embodying the present invention incorporated in an ear of a patient.

Components that are common between the drawings bear common reference numerals.

Fig. 1 shows a side elevational view of a partial substitution type artificial auditory ossicle 10P. The latter includes a head portion 1 in the form of a disc, a cylindrical shank portion 2 which is connected to one side of the head portion 1 and extends in a direction substantially perpendicular to a planar surface of the head portion 1, and a projection 3 which is connected to the side of the head portion 1 opposite the shank portion 2. The projection 3 extends in a direction substantially perpendicular to the plane of the head portion 1. The projection 3 is solid and is circular in cross section. The projection 3 is comprised of a base portion 3a having a diameter which gradually increases from the head portion 1 towards the front end thereof, and a sharp tip 3b having a diameter which gradually decreases from the base portion 3a to a point. The sharp tip 3b is provided for easy penetration of the associated cartilage piece (not shown in Fig. 1). The base portion 3a is provided with a gradually increasing diameter to inhibit detachment of the artificial auditory ossicle 10P from the associated cartilage piece.

The cylindrical shank portion 2 is provided with a hollow portion 4 which opens at one end of the shank and extends in an axial direction thereof so that a stapes (or stirrup) can be f itted in and connected to the open end of the hollow portion 4. Namely, the partial substitution type auditory ossicle 1OP is provided with the hollow portion 4.

Fig. 2 shows an entire substitution type auditory ossicle 10T embodying the present invention. In Fig. 2, the artificial auditory ossicle 10T includes a head portion 1 in the form of a circular disc, a cylindrical shank portion 5 which is connected to one side of the head portion 1 and extends in a direction substantially perpendicular to the plane of the head portion 1, and a projection 3 which is connected to the side of the head portion 1 opposite shank portion 5. The projection 3 extends in a direction substantially perpendicular to the planar surface of the head portion 1, similar to the auditory ossicle 10P shown in Fig. 1. The shape of the projection 3 is identical to that of the projection 3 shown in Fig. 1.

The auditory ossicle 10T shown in Fig. 2 and the auditory ossicle 10P shown in Fig. 1 are different only in the shank portions thereof. Namely, the cylindrical shank portion 5 in Fig. 2 is solid and does not have a hollow portion. Furthermore, the cylindrical shank portion 5 in Fig. 2 is longer than the cylindrical shank portion 2 in Fig. - 1 since the auditory ossicle 1OT (shown in Fig. 2) is directly connected to the base of the stapes.

Figs. 3 and 4 show two different embodiments of artificial auditory ossicles 10P1 and 10T1 corresponding to Figs. 1 and 2, respectively. In both of these embodiments, the projection 3 is provided with a cylindrical base portion 3c having a uniform diameter, unlike the base portion 3a in Figs. 1 and 2 in which the diameter of the base portion 3a gradually increases towards the front end thereof. The remaining structure of the artificial auditory ossicles 1OP' and 1OT' is identical to that of the artificial auditory ossicles 10P and 10T, respectively.

Fig. 5 shows a partial substitution type artificial auditory ossicle 10P (or 1OPt) embodying the present invention incorporated in an ear of a patient, by way of example. In Fig. 5, the shank portion 2 is connected to a stapes (stirrup) 8, and the projection 3 pierces into the cartilage piece 9 which is immovably contacted with the eardrum 11. Consequently, not only can a good conductive function be obtained, but also deviation of a cartiiage. piece 9 is prevented during and after the operation. Note that numeral 12 designates an external auditory meatus. The length of the shank portion 2 is adjusted (i.e., cut) in accordance with the dimensions of the port-ion which is to be subject to the operation.

When the stapes 8 is not present, the entire substitution type artificial auditory ossicle 10T (or 1OV) is used. In this procedure, the shank portion 5 is directly connected to auris interna 13. Similar to the procedure for the partial substitution type artificial auditory ossicle 10P (or 1OP'). the length of the shank portion 5 is appropriately adjusted.

Example 1

A slurry of hydroxyapatite was obtained from a wet composition of phosphate and calcium salt in a known method. The hydroxyapatite slurry thus obtained was dried by a rotary drum type of drier manufactured by Nishimura Tekkosho Co. Ltd., to produce a hydroxyapatite powder. The hydroxyapatite powder was pressed into a green compact having a 7 mm diameter and a 20 mm length. The green compact thus obtained was machined into a shape shown in Fig. 1 by an NC lathe, taking into account the contraction which would take place during the subsequent baking operation. Thereafter, the green compact was baked at 1100'c in the electric furnace for 2 hours.

The artificial auditory ossicles thus produced were used for patients suffering from chronic otitis media or cholesteatoma tympanitis. Good results were obtained with these artificial auditory ossicles.

As -can be seen f rom the above discussion, with the present invention, the artificial auditory ossicle of the present invention is advantageous to a tympanoplasty which employs a piece of cartilage between an eardrum and an artificial auditory ossicle. The piece of cartilage can be secured without using an adhesive. Consequently, displacement or detachment of the piece of cartilage does not occur during or after the operation. Accordingly, a patient's hearing can be improved in a stable manner for a long period of time without the need for further operations.

Also, the operation is simplified with the present invention. A further benefit exists in that, if the artificial auditory ossicle is made of calcium phosphate series ceramic, the auditory ossicle can be easily cut or machined to adapt the same for a variety of patients.

1

Claims

13 CLAIMS

1. An artificial auditory ossicle for utilization in a tympanoplasty as a substitute for a part or whole of an auditory ossicle chain connecting an eardrum and an auris interna, the ossicle comprising: a head portion having a planar surface for contacting with a piece of cartilage which is positioned, in use, on the eardrum; a shank portion connected to the head portion and extending in a direction substantially perpendicular to the planar surface of the head portion; and a projection connected to the head portion and extending in a direction opposite to the shank portion for penetrating the piece of cartilage.

2. An ossicle according to claim 1 wherein said head portion is in the shape of a disc.

3. An ossicle according to claim 1 or 2 wherein said projection comprises a cylindrical base portion having a diameter which gradually increases away from the head portion, and a tip portion adjacent to the cylindrical base portion and having a diameter which gradually decreases from the base portion to a sharp tip.

4. An ossicle according to claim 1 or 2 wherein said projection comprise a cylindrical base portion having a uniform diameter, and a tip portion adjacent to the cylindrical base portion and having a diameter which gradually decreases from the base portion to a sharp tip.

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5. An ossicle according to any preceding claim wherein the shank portion is a solid cylinder for connection, in use, to the auris interna.

6. An ossicle according to any one of claims 1 to 4 wherein the shank portion is a hollow cylinder which opens at one end, wherein the open end is for connection with, in use, a stapes.

7. An ossicle according to any preceding claim wherein said artificial auditory ossicle is made of a high density calcium phosphate ceramic.

8. An ossicle according to claim 5 or 6 wherein said head portion is disc shaped and has a diameter larger then the diameter of the shank portion.

9. An artificial auditory ossicle comprising:a head portion in the shape of a disc; a shank portion connected to the head portion and extending in a direction substantially perpendicular to the head portion; and a projection connected to the head portion and extending in a direction opposite to the shank portion.

10. An artificial auditory ossicle for utilization in a tympanoplasty as a substitute for a part or whole of an auditory ossicle chain connecting an eardrum and an auris interna, substantially as hereinbefore described with reference to the accompanying drawings.