WO2019183647A1

WO2019183647A1 - Total ossicular prosthesis (top) /modern stapes prosthesis in cases of conductive hearing loss

Info

Publication number: WO2019183647A1
Application number: PCT/ZA2019/050007
Authority: WO
Inventors: Mashudu TSHIFULARO
Original assignee: Tshifularo Mashudu
Priority date: 2018-03-23
Filing date: 2019-02-27
Publication date: 2019-09-26
Also published as: ZA202006572B

Abstract

The invention provides a prosthetic (10) for use in the middle ear of a person. The prosthetic (10) includes a body (12) which resembles a malleus (14), incus (16) and stapes (18) and is shaped and configured to occupy similar space than a malleus, incus and stapes a hole (20) is defined through the body (12) through which, in use, a suspension wire (22) can be threaded and with one end of the wire (22) connected or cemented to the bony annulus and the other end connected or cemented to the opposed bony annulus to suspend the body in the middle ear cavity and allowing a rocking movement of the body to transmit vibrations from the tympanic membrane to the oval window or footplate. Alternatively attachment points or stubs are provided on the body to attach to remains of ligaments and tendons after the original malleus, incus and/ or stapes is surgically removed.

Description

Title: Total Ossicular Prosthesis (TOP) /Modern Stapes prosthesis In Cases Of Conductive Hearing Loss

Technical field of the invention

This invention relates to a prosthesis for use to treat conductive hearing loss in cases such as otosclerosis, trauma, congenital disease, metabolic disease and middle ear infection.

Background to the invention

The middle ear is a hollow space, the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. The middle ear, also called the tympanic cavity, or cavum tympani contains three ossicles, which amplify vibration of the eardrum into pressure waves in the fluid in the inner ear. When sound is transferred from an air medium to a liquid medium most of the sound is reflected and the middle ear allows the impedance matching to overcome the interface between air and liquid. The middle ear functions as a sound amplifier. The ossicles: malleus, incus, and stapes, are also known as the hammer, anvil, and stirrup, respectively. The ossicles directly couple sound energy from the ear drum to the oval window of the cochlea.

There are several specific ways in which the middle ear amplifies sound from air received at the tympanic membrane to the fluid in the oval window. The first of these is the "hydraulic principle". The vibratory portion of the tympanic membrane is many times the surface area of the footplate of the stapes. The collected pressure of sound vibration that strikes the tympanic membrane is concentrated down to this much smaller area of the footplate, increasing the force and thereby amplifying the sound.

The second way in which the middle ear amplifies sound is by means of the "lever principle". The shape of the articulated ossicular chain is like a lever, the long arm being the malleus, and the body of the incus being the fulcrum or pivot point and the short arm being the incus. The third way in which the middle ear amplifies sound is by "round window protection". The cochlea is a fluid filled tube, wound about on itself. One end of this tube is at the oval window, the other end is at the round window. Both of these windows, opening in the bone, lay on the deep wall of the middle ear space. Whereas the tympanic membrane and ossicular chain preferentially direct sound to the oval window, the round window is protected by middle ear structures from having sound waves impinge on its surface. The middle ear structures that protect the round window are the intact tympanic membrane and the round window niche. If there were no tympanic membrane or ossicular chain, sound waves would strike the round window and oval window at the same time which cancels the energy of the sound transmission.

Importantly, the middle-ear is able to dampen sound conduction a bit when faced with very loud sound by noise induced reflex contraction of the middle ear muscles, which inhibits the movement of the ossicles. The movement of the ossicles can be inhibited by two muscles, the stapedius and tensor tympani, which are under the control of the facial nerve and trigeminal nerve, respectively. These muscles contract in response to loud sounds, thereby reducing the transmission of sound to the inner ear. This is called the acoustic reflex. The auditory ossicles can also reduce sound pressure by uncoupling each other through particular muscles.

The ossicles mechanically convert the vibrations of the eardrum, into amplified pressure waves in the fluid of the cochlea (or inner ear) with a lever arm factor of 1.3. Since the area of the eardrum is about 17 fold larger than that of the oval window, the sound pressure is concentrated, leading to a total amplification of at least 22. The eardrum is fused to the malleus, which connects to the incus, which in turn connects to the stapes. Vibrations of the stapes footplate introduce pressure waves in the inner ear.

In summary, the amplification system and loud noise dampening system described above is a delicate sum of the function of all the parts of the inner ear. The applicant is aware that normally, for persons affected by otosclerosis, the footplate of the stapes fixates at the footplate annulus ligament and not the stapes bone itself. A stapedectomy is performed to try and restore hearing to some extent. A stapedectomy includes complete removal of the stapes, its suprastructure, stapedial tendon and incostapedial joint, most of which is still functioning properly. The removal of these functioning components interferes with the delicate amplification and loud sound dampening system of the inner ear.

It is an object of this invention to provide a prosthesis which will retain some of the natural functioning of the middle ear.

General description of the invention

According to a first aspect of the invention there is provided a prosthetic for use in the middle ear of a person, which prosthetic includes: a body which resembles a malleus, incus and stapes and is shaped and configured to occupy similar space than a malleus, incus and stapes; and wherein a hole is defined through the body through which, in use, a suspension wire can be threaded and with one end of the wire connected or cemented to the bony annulus and the other end connected or cemented to the opposed bony annulus to suspend the body in the middle ear cavity and allowing a rocking movement of the body to transmit vibrations from the tympanic membrane to the oval window or footplate.

The position of the hole is determined generally by the axis through the centre of gravity of the body, normally the part resembling the malleus.

In another preferred embodiment of the invention, instead of a hole through the body through which a suspension wire can be threaded, attachment points or stubs is provided to attach to remains of ligaments and tendons after the original malleus, incus and/ or stapes is surgically removed. The attachment points are provided to resemble or be near the natural attachment points of the malleus, incus and/ or stapes, which allows a natural rocking movement of the body to transmit vibrations from the tympanic membrane to the oval window or footplate.

Attachment points are provided for anterior malleus ligament and posterior malleus ligament. In addition attachment points are provided for any one or more of the superior malleus ligament, tensor tympani tendon and stapedius tendon.

The malleus, incus and stapes is generally in a plane and arranged in an upside down U-shape. During normal vibration transmission between the tympanic membrane and the oval window or footplate, the malleus, incus and stapes rocks about an axis located in the malleus.

The hole may be defined in the malleus resembling part of the body to provide a pivot which mimic the natural axis located in a malleus. In other words, the location of the axis mimics the suspension and rocking function of the natural anterior, lateral and superior ligaments. The location of the attachment points or stubs are similarly positioned to provide a pivot which mimic the natural axis located in a malleus.

The body may be of silver or preferably of titanium which has good bio compatibility, anti-microbial properties and good sound transmission properties. The body may be 3D modelled for a person using a CT scan and may be printed accordingly with a 3D printer.

The body may comprise of three parts each respectively representing the malleus, incus and stapes, which can be coupled, before surgery. Each part may include coupling formations.

According to another aspect of the invention, there is provided a stapes prosthesis, which stapes prostheses includes:

a generally conically shaped body of which the narrow end is configured to fit into a hole provided in the foot plate; and attachment means for attachment to the remaining part of the stapes of a patient.

It is to be appreciated that the conical shape prevents over penetration through the hole in the foot plate.

The attachment means may be of a clip-on type.

Detailed description of the invention

The invention is now described by way of example with reference to the accompanying drawings.

In the drawings:

Figure 1 shows an assembled embodiment of a prosthetic for use in the middle ear of a person, in accordance with the invention;

Figure 2 shows a stapes part of the body;

Figure 3 shows a malleus part of the body;

Figure 4 shows an incus part of the body;

Figure 5 and 6 shows an integrally formed embodiment of a prosthetic for use in the middle ear of a person, in accordance with the invention; Figures 7 and 8 shows a stapes prosthesis; and

Figure 9, 10 and 11 shows another example of the stapes prosthesis.

The prosthetic for use in the middle ear of a person is generally indicated by numeral 10. The prosthetic includes a body 12 which with three parts, respectively resembling a malleus 14, incus 16 and stapes 18, which can be coupled, before surgery with each part including coupling formations 19. The body 12 is shaped and configured to resemble and occupy similar space than a natural malleus, incus and stapes. A hole 20 is defined through the malleus part of the body through which a suspension wire 22 can be threaded and with one end cemented to the bony annulus and the other end cemented to the opposed bony annulus to suspend the body 12 in the middle ear cavity and allowing a rocking movement of the body to transmit vibrations from the tympanic membrane to the oval window or footplate. The malleus 14, incus 16 and stapes 18 is generally in a plane and arranged in an upside down U-shape. During normal vibration transmission between the tympanic membrane and the oval window, the body 12 rocks about an axis located through the malleus. The hole 20 about the suspension wire 22 provides a pivot which mimic the natural pivot axis located in a natural malleus.

The body 12 is of titanium which is 3D modelled for a specific person and then printed accordingly with a 3D printer.

The stapes 18 part is cemented to the oval window and the malleus 14 is provided attachment formations 26 for attachment to the tympanic membrane.

In another embodiment as shown in Figure 5 and 6, the prosthetic includes a body 12 which with three integral parts, respectively resembling a malleus 14, incus 16 and stapes 18.

Attachment points in the form of stubs 40, 42, 44 and 46 are provided for tympani tendon, stapedius tendon, stabilizing ligament or any combination thereof.

Figures 7 and 8 shows a stapes prosthesis 30, which includes a generally conically shaped body 32 of which the narrow end is configured to fit into a hole 33 provided in the foot plate 34. The prosthesis further includes a clip-on type attachment means 36 for attachment to the remaining part 38 of the stapes of a patient.

Figure 9 shows the stapes prosthesis 30 in an inoperative position with the remaining part 38 of the stapes of the patient.

Figure 10 and 1 1 shows the stapes prosthesis 30 in an operative position with the attachment means 36 attached to the remaining part 38 of the stapes of the patient. It shall be understood that the examples are provided for illustrating the invention further and to assist a person skilled in the art with understanding the invention and are not meant to be construed as unduly limiting the reasonable scope of the invention.

Claims

1. A prosthetic for use in the middle ear of a person, which prosthetic includes:

a body which resembles a malleus, incus and stapes and is shaped and configured to occupy similar space than a malleus, incus and stapes; and wherein a hole is defined through the body through which, in use, a suspension wire can be threaded and with one end of the wire connected or cemented to the bony annulus and the other end connected or cemented to the opposed bony annulus to suspend the body in the middle ear cavity and allowing a rocking movement of the body to transmit vibrations from the tympanic membrane to the oval window or footplate.

2. A prosthetic as claimed in Claim 1 , wherein the position of the hole is determined generally by the axis through the centre of gravity of the body.

3. A prosthetic for use in the middle ear of a person, which prosthetic includes:

a body which resembles a malleus, incus and stapes and is shaped and configured to occupy similar space than a malleus, incus and stapes; and attachment points or stubs to attach to remains of ligaments and tendons after the original malleus, incus and/ or stapes is surgically removed.

4. A prosthetic as claimed in Claim 1 , wherein the position of the attachment points are provided to resemble or be near the natural attachment points of the malleus, incus and/ or stapes.

5. A prosthetic as claimed in Claim 3 or Claim 4, wherein attachment points are provided for an anterior malleus ligament and an posterior malleus ligament.

6. A prosthetic as claimed in Claim 5, which also includes attachment points for any one or more of the superior malleus ligament, tensor tympani tendon and stapedius tendon.

7. A prosthetic as claimed in any one of previous claims wherein the body is of silver or titanium.

8. A prosthetic as claimed in any one of previous claims, wherein the body is 3D modelled for a person using a CT scan and printed accordingly with a 3D printer.

9. A prosthetic as claimed in any one of previous claims, wherein the body includes three parts each respectively representing the malleus, incus and stapes, which can be coupled, before surgery and wherein each part includes coupling formations.

10. A stapes prosthesis, which stapes prostheses includes:

a generally conically shaped body of which the narrow end is configured to fit into a hole provided in the foot plate; and

attachment means for attachment to the remaining part of the stapes of a patient.