WO1993010729A1

WO1993010729A1 - Middle ear ventilation tube

Info

Publication number: WO1993010729A1
Application number: PCT/SE1992/000805
Authority: WO
Inventors: Ove Densert; Stig Hansson
Original assignee: Hb Proxima
Priority date: 1991-11-28
Filing date: 1992-11-24
Publication date: 1993-06-10
Also published as: AU3099592A; SE9103546D0

Abstract

The invention relates to an implant for ventilating the middle ear intended to be implanted into the cortical bone behind the ear. The implant comprises a main body (1, 8) which is made of, or covered by a layer of, a biocompatible material, which is provided with a longitudinal bore (5, 12) and which has a length sufficient to completely penetrate the cortical bone and to come into functional contact with the space wherein the mastoid cell system is located, beneath the cortical bone, when inserted into a hole made through said cortical bone.

Description

Middle ear ventilation tube.

The present invention relates to a device for ventilating the middle ear in accordance with the preamble of the attached main claim.

Background to the invention

It is generally accepted that a negative pressure in the middle ear, i. e. a pressure lower than that of the ambient atmosphere, is a factor strongly contributing to the development of otosalpingitis (SOM) and chronical middle ear diseases involving a retraction of the entire tympanic membrane or parts thereof, with following atelectasis/collapse of the middle ear air cavity, in which the middle ear structures, including parts of the ossicular chain, may undergo progressive destruction. These later conditions also include most cases with cholesteatoma, which is a cyst-like formation (growth) of sguamous cells. When the growth expands, this may cause eroding of the nearby structures and damage to the middle ear, the facial nerve, the periphery balance system and as well as infections involving the central nervous system. Thus, although not being histologically malignant, cholesteatoma have very serious complications and require advanced surgical interventions. A negative pressure in the middle may however be a direct cause for cholesteatoma.

The Eustachian tubes, which connect the middle ear to the nasopharynx, are believed to be closed normally and to open upon swallowing and thus inter alia to serve to equalize the air pressure in the middle ear. It has been found that the air in the middle ear is continuously absorbed into the surrounding tissue. In cases where the Eustachian tubes are blocked or do not function correctly, a more or less chronic negative pressure may be created in the middle ear. Another reason for a negative pressure in the middle ear is when the Eustachian tubes do not close properly. The patient experiences this as unpleasant and tries to alleviate the feeling of discomfort by "sniffing", which leads to a negative pressure in the middle ear. This negative pressure may result in that the Eustachian tubes are closed and remain closed by the higher pressure of the ambient atmosphere.

The mutual factor which is responsible for the above middle ear conditions is the negative air pressure created in the middle ear cavity.

Several approaches have been tried in order to obtain a ventilation of and pressure equalization in the middle ear.

One approach has been to insert a tube of polyethylene between the skin and the bone wall of the external auditory eatus. A variation of this has been to bore a hole in the bone past the tympanic membrane and to insert a tube of Silastic^R opening into the external auditory meatus.

Another approach has been to insert tubes or spirals of different kinds made of plastics into the Eustachian tubes in order to keep the tubes open.

Another approach has been to construct a shunt opening into the maxillary sinus.

None of the methods described above have won widespread acceptance due to surgical problems and inadequate function but above all due to inadequate tissue compatibility. The most common way of ventilating the middle ear is still a ventilation tube inserted in the tympanic membrane. Due to a poor biocompability between the materials used and the tissue, rejections and occlusions of the tube are frequent complications of this method of treatment. A rejection of the tube within 6 - 12 months cannot be prevented and is in most cases indeed desirable.

When cholesteatoma are removed surgically, this is mostly done by obtaining access to the middle ear by removing the cortical bone behind the external ear canal and the underlying mastoid cell system. Since the basic mechanisms of cholesteatoma still remain after the surgical procedures, the negative pressure in the middle ear still creates problems which makes it technically difficult to reconstruct the sound transmission via surgery and may also lead to a recurrence of the cholesteatoma.

One important reason for obtaining a connection into the middle ear is the novel treatments of Meniere's disease by means of carefully controlled air pressure pulses which are applied to the middle ear. These novel methods are for instance described in EP-A1-0266474. Normally these pulses are transmitted to the middle ear through a tube in the tympanic membrane of the kind described above. Since it may be desirable to be able to repeat the treatment, it would be advantageous to have a more permanent connection into the middle ear.

The pathophysiological problems connected with a negative pressure in the middle ear cavity caused by an Eustachian tube dysfunction represent one of the most common and complex disorders in otology, still lacking an adequate solution.

The problems described above are solved by means of an implant intended to be implanted in the cortical bone behind the ear according to the characterizing portion of the appended main claim.

Providing a way of an efficient ventilation of the middle ear in this manner will

- ensure normal sound transmission through the middle ear,

- prevent the development of chronic middle ear conditions which may cause destruction of the middle ear ossicular chain, - prevent recurrence of an cholesteatoma growth,

- create a possibility for inspecting the post-surgical cavity for a recurrence of the cholesteatoma,

- create a permanent access to the middle ear cavity for applying local positive pressures in the treatment of Meniere's disease.

- lessen the need for repeated, costly and technically difficult surgical procedures for the reconstruction of the middle ear sound transmission function,

It should be noted that the above mode of ventilating the middle ear allows a conservation of the entire middle ear system in ear surgery of the kind described above since the device used does not encroach on or affect the middle ear structures.

Short description of the appended drawings.

Fig 1 illustrates a tubular base part intended to inserted into a hole drilled through the cortical bone.

Fig 2 illustrates a tubular intermediate part intended to penetrate the layer of skin on the cortical bone behind the ear, Figs 3 and 4 illustrate a healing cap with attachment screw for protecting the area around the intermediate part during healing.

Figs 5 and 6 illustrate a filter unit with protective cap for connection to the intermediate part.

Detailed description of a preferred embodiment of the invention.

Fig 1 shows a longitudinal section through a base part 1 for implanting in bone according to a preferred embodiment of the invention. The base part is provided with a longitudinal bore 5 extending through the entire length of the base part. The bore 5 has a conically flaring portion 6 at the distal end, distal and proximal in this context corresponding to the distal respectively proximal end of the base part when this is implanted into the bone. At the proximal end of the flaring portion 6 there are internal threads 7.

The base part 1 has the general configuration of a self- tapping screw being provided with threads 2 at its proximal end in conjunction with cut-outs 3 which are provided in order to form a cutting edge 4 for cutting threads in the bone when the base part is screwed into a bored hole extending through the cortical bone behind the ear. The base part has a length which is sufficient to allow the base part to extend into the mastoid cell system. Since the cells in the mastoid cell system are interconnected and the proximal cells are connected to the middle ear, a communication allowing air to pass will be established from the exterior of the patient through the cortical bone and the cell system to the middle ear when the tubular base part has been screwed into the bore in the cortical bone mentioned above. The base part is made of or covered with a layer of titanium or a titanium alloy in order to ensure good compatibility with the surrounding bone tissue and to avoid the development of granular tissue which possibly might block the bore in the base part and of course also to ensure a firm healing or integration of the base part into the surrounding bone tissue.

By the means of the device as described in the present application, a functional communication of the middle ear and the athmospheric pressure is provided.

In the case of surgical treatment of cholesteatoma, the situation will be somewhat different. At these operations normally the main part of the cortical bone behind the ear is removed all the way to the sinus dura angle together with the mastoid cell system in order to obtain a completely unhampered access to the middle ear for removal of the cholesteatoma. The skin and muscles are then allowed to heal over the bone cavity which is a result of the operation.

However, if the implant according to the invention is to be used, some of the cortical bone close to the sinus dura angle is left in order to create a bracket for the base part. The base part will then permit both an inspection of the cavity created by the operation and a ventilation of the middle ear, which will minimize the risks for a new retraction and the development of a new cholesteatoma. The ventilated middle ear is also a prerequisite for sound transmission through the middle ear.

The base part of course should have a length which is sufficient for a complete penetration of normal cortical bone. The base part can however also be made in several standardized lengths, the most suitable length being chosen at the operation. Fig 2 illustrates an intermediate part 8 intended to bridge the layer of skin normally covering the cortical bone behind the ear (the muscles close to the incision are normally removed in order to avoid the development of granular tissue) . The intermediate part 8 is provided with external threads 9 on its proximal end corresponding to the internal threads 7 on the base part 1. The exterior of the intermediate part widens conically directly adjacent the threads, at 10, in order to mate with the internal conically flaring portion 6 of the base part 1. A circumferential flange 11 is located on the distal end of the exterior of the intermediate part. The intermediate part is further provided with a longitudinal bore 12 which is provided with internal threads 13 at its distal end. These threads preferably correspond to the internal threads 7 on the base part 1.

The intermediate part 8 is screwed tightly into the base part 1 and the skin is allowed to heal around the intermediate part. The intermediate part 8 is also preferably made of titanium or a titanium alloy in order to ensure good tissue compatibility. When fitting the intermediate part 8 a part is chosen which has a length which is sufficient to ensure that the flange 11 is located a distance away from the surface of the skin.

A healing cap 14 intended to be mounted on the intermediate part 8 is shown in Fig 3. This cap is provided with a through-bore 16 which at its proximal end has a shape which is complementary to the shape of the distal end of the intermediate part. The healing cap thus can be press-fitted onto intermediate part 8 and firmly attached by means of a screw 17, shown in Fig 4, inserted through the bore 16 and engaged with the interior threads 13 of the part 8 by means of the threads 18. A suitable material for the healing cap is for instance high density polyethylene. When the skin has healed around the intermediate part 8, a filter unit and a protective cap^", shown in Figs 5 and 6, can be mounted on the intermediate part 8. The filter unit comprises a hollow, open-ended cylindrical main body 19 which at the proximal end is provided with a circumferential, internal flange 20 which can be snapped over the external flange 11 on the intermediate part 8. The distal end of the body 19 is provided with an air- permeable filter 21 and the outside of the body 19 is provided with a circumferential bead 22. The filter unit can be covered by a cap 23 being provided with a circumferential, internal groove 24 which is complementary in shape to the external bead 22 on the filter unit, by which means the cap can be snapped onto the filter unit. The cap 23 further is provided with a comparatively small hole 25. The function of the filter is to allow air to pass but to prevent water, bacteria etc from entering the cell system and the middle ear, thus allowing the patient to lead a normal life including bathing, showering, hair washing etc.

Should it be desirable to temporarily close and seal the opening of the implant can be mounted on the implant, for instance a cap similar to the filter unit which is airtight. The opening of course can also be sealed by means of a screw similar to the attachment screw 17.

The attachment parts of a connection between a tube from an air pressure generator for use in the Meniere treatment mentioned above and the intermediate part can be designed similarly to the design of the filter unit. It may however be more suitable to design the external flange 11 on the intermediate part as parts of a bayonet coupling or, alternatively, to utilize the internal threads in the intermediate part in order to ensure a tight connection between said tube and the intermediate part. Possible modifications of the invention

The invention can of course be modified in many ways within the scope of the appended claims.

Thus the proximal end of the bore in the base part may have a conically flaring design in order to minimize the risk that bone grows into the opening and partly occludes the bore.

The tubular implant further has been described as comprising two main parts, one base part to be implanted into the bone and one intermediate part to penetrate the skin. This is for instance advantageous if the implanting operation is to be performed in two stages, a first stage wherein the base part is allowed to integrate into the bone in an undisturbed way under the skin layer and a second stage wherein the intermediate part is inserted through an opening in the skin which then is allowed to heal around the intermediate part.

With a two part implant it will also be possible to remove the intermediate part penetrating the skin layer and allow the skin plant to heal over the base part in the bone.

It should however be noted that it is quite possible to perform the operation as a one stage operation since the implant normally will not be subjected to heavy loads. It is also quite possible to design the implant as a one- piece implant.

In the preferred embodiment the biocompatible material used is titanium or titanium alloys. However, any suitable biocompatible material can be used, such as chrome-cobalt alloys (e. g. Vitallium^R) , Zirconium, Hafnium, stainless steel, ceramic materials, materials covered with hydroxy apatite etc. The implant has been described above as being threaded. This feature is very important in the cases where the implant is to be permanent, since it will be very difficult to remove a threaded implant. A smoother implant will also have good integration properties, but may be easier to remove, should the necessity arise.

The filter unit has been illustrated as a cap covering the end of the implant. The filter of course also could be made in the form of a plug insertable into the bore in the implant, or made in any other suitable shape.

Claims

1. Implant for ventilating the middle ear intended to be implanted into the cortical bone behind the ear, c h a r a c t e r i z e d in that the implant comprises an main body (1, 8) which is made of, or covered by a layer of, a biocompatible material, which is provided with a longitudinal bore (5, 12) and which has a length sufficient to completely penetrate the cortical bone and to come into functional contact with the space beneath the cortical bone, wherein the mastoid cell system is located, when inserted into a hole made through said cortical bone.

2. Implant according to claim 1, c h a r a c t e r i z e d in that the distal end of the main body (1, 8) is provided with attachment means (11, 13) for optional accessories (14, 17, 19, 23).

3. Implant according to any one of claims 1 or 2, c h a r a c t e r i z e d in that said tubular main body comprises two parts, one base part (1) which is to be implanted in the cortical bone and one intermediate part (8) which is to extend from the base part through the skin layer.

4. Implant according to any one of the preceding claims, c h a r a c t e r i z e d in that said implant is made of, or covered by a layer of, titanium or a titanium alloy.

5. Implant according to any one of the preceding claims, c h a r a c t e r i z e d in that the distal end of the implant can be provided with a healing cap (14, 17) protecting the skin around the implant during the healing of the incision in the skin. 12

6. Implant according to any one of the preceding claims, c h a r a c t e r i z e d in that the distal end of the implant can be provided with a filter unit (19, 23) allowing air to pass but preventing the passage of dirt,

5 water, bacteria etc.

7. Implant according to claim 6, c h a r a ct e r i z e d in that the filter unit comprises a filter part (19) which is provided with a

10 filter (21) and which is provided with an internal flange (20) which can be snapped over a complementary flange (11) on the implant.