Medical implant system for fixing a hearing device

FIELD

0001The present disclosure relates to medical implant systems and components for fixation of hearing devices to bone.

PRIORITY

0002The present application claims priority from: <ul id="ul0001" list-style="dash"><li>Australian Provisional Patent Application No. <patcit id="pcit0001" dnum="AU2009903789"><text>2009903789</text></patcit> entitled "Implant Device" filed on 13 August 2009; and</li><li>Australian Provisional Patent Application No. <patcit id="pcit0002" dnum="AU2009905020"><text>2009905020</text></patcit> entitled "Implant Device" filed on 14 October 2009.</li></ul>

BACKGROUND

0003Bone-anchored medical implant systems are used to connect or fixate hearing devices to a user, directly to the bone or skull of the user. Some applications include hearing implants such as the Baha® hearing implant system marketed by Cochlear Bone Anchored Solutions AB in Sweden. The Baha® implant comprises an external unit which transforms sound into mechanical vibrations which are conducted via an abutment and a bone fixture of the implant, into the bone of the skull. The vibrations are transmitted mechanically via the skull bone directly to the inner ear of a person with impaired hearing and allows for the hearing organ to register the sound. A hearing device of the Baha® type is connected to an anchoring element or fixture, in the form of an implanted titanium screw, forming the bone fixture, installed in the bone behind the external ear and the sound is transmitted via the skull bone to the cochlea (inner ear), irrespective of any disease, injury or other disfunction of the middle ear. In some bone conduction or anchoring arrangements, the skin is penetrated, which makes the vibratory transmission very efficient. This arrangement can also be used in connection with facial prostheses such as Vistafix™, marketed by Cochlear Limited, Australia.

0004The implants which are used on the market today are often provided in two pieces. One piece consists of the screw-shaped anchoring element (fixture or anchor) and the other piece consists of the abutment for skin penetration. This two-piece design allows the surgical implantation to be carried out as a two-step procedure. In the first step the fixture is inserted and maintained unloaded during a healing period of some months or so. After this healing period the second step of the surgical procedure, i.e. the connection of the abutment by means of an abutment screw, is carried out. This two-part design allows the implants to be up-graded if necessary without removing the fixture or anchor. Furthermore, if the abutment is damaged then it can also be replaced without need of removal of the bone anchored screw or fixture.

0005A problem with percutaneous implant devices is the risk of infections and inflammation at the tissue-implant interface. The infections are a result of bacterial colonization occurring at the area around the interface. This problem can be persistent and cause infections. Cleaning of the interface is of course very important to keep the area free from problems, however, even regular cleaning and disinfection is not always entirely successful.

0006The bacteria can enter the implant-tissue interface by two different routes - the external route on the external surface of the abutment, and the internal route which starts at the top of the abutment and travels via the internal parts (screw connection) of the implant system and may exit at the abutment-fixture-soft tissue junction or interface. The external route is the most open one, but the bacteria may also invade from the internal route, known as the internal micro-leakage pathway.

0007<patcit id="pcit0003" dnum="US5735790A"><text>US-A-5735790</text></patcit> discloses a device for interconnecting an implant anchored in the skull bone of a person with impaired hearing, which acts as or supports a first coupling part and a second coupling part interconnectable therewith and connected to a vibration exciting apparatus, whereby said coupling parts are constituted by a substantially cup-shaped female part and a male part, which is insertable therein under mutual flexing, the female part being designed as a rigid cup-shaped seat, whereas the male part is designed to be resilient in radial direction in order to permit a snap-in introduction into the female part.

0008<patcit id="pcit0004" dnum="US2006050913A"><text>US-A-2006050913</text></patcit> discloses a hearing-aid interconnection system with a skin-penetrating hearing-aid abutment and a fixture anchored in a skull bone. A first press fit is formed between a first contact surface of the abutment and a first fixture contact surface of the fixture. The first abutment contact surface extends around the first fixture contact surface. A second press fit is formed between a second contact surface of the abutment and a second fixture contact surface of the fixture. The second fixture contact surface extends around the second abutment contact surface

SUMMARY

0009The present invention provides a medical implant system for coupling a hearing device to a user as set forth in claim 1. Preferred embodiments are defined in the dependent claims.

DRAWINGS

0010<ul id="ul0002" list-style="none"><li><figref idref="f0001">Figure 1</figref> - shows an example of a medical implant system to which various aspects of the present disclosure may be applied;</li><li><figref idref="f0001">Figure 2</figref> - shows a cross section of the medical implant system of <figref idref="f0001">Figure 1</figref>;</li><li><figref idref="f0002">Figure 3</figref> - shows a perspective view of the medical implant system of <figref idref="f0001">Figure 1</figref>;</li><li><figref idref="f0002">Figure 4</figref> - shows a cross section exploded view of the components of the medical implant system of <figref idref="f0001">Figure 1</figref>;</li><li><figref idref="f0003">Figure 5A</figref> - shows one embodiment of an abutment screw of one aspect of the disclosure;</li><li><figref idref="f0003">Figure 5B</figref> - shows a cross section of the abutment screw of <figref idref="f0003">Figure 5A</figref>;</li><li><figref idref="f0003">Figure 5C</figref> - shows a close up view of the deformable element of <figref idref="f0003">Figure 5B</figref>;</li><li><figref idref="f0003">Figure 6</figref> - shows a cross section of the abutment screw of <figref idref="f0003">Figure 5A</figref> in an abutment;</li><li><figref idref="f0003">Figure 7</figref> - shows a close-up cross section view of a seal provided between the abutment screw of</li><li><figref idref="f0003">Figure 5A</figref> and the abutment;</li><li><figref idref="f0004">Figure 8</figref> - shows a cross section of an alternative embodiment of the abutment screw of <figref idref="f0003">Figure 5A</figref>;</li><li><figref idref="f0004">Figure 9A</figref> - shows a cross section of yet a further alternative of the abutment screw of <figref idref="f0003">Figure 5A</figref>;</li><li><figref idref="f0004">Figure 9B</figref> - shows a perspective view of the abutment screw of <figref idref="f0004">Figure 9A</figref>;</li><li><figref idref="f0004">Figure 10</figref> - shows a close-up cross section view of a seal provided between the abutment screw of <figref idref="f0004">Figure 9A</figref> and the abutment;</li><li><figref idref="f0005">Figure 11</figref> - shows a perspective view of one embodiment of an abutment;</li><li><figref idref="f0005">Figure 12</figref> - shows a cross section of the abutment of <figref idref="f0005">Figure 11</figref>;</li><li><figref idref="f0005">Figure 13</figref> - shows a close-up view of a seal provided between the abutment screw and the abutment of <figref idref="f0005">Figure 11</figref>;</li><li><figref idref="f0006">Figure 14</figref> - shows a cross section of one embodiment of a fixture;</li><li><figref idref="f0006">Figure 15</figref> - shows a perspective view of one embodiment of an abutment for use with the fixture of <figref idref="f0006">Figure 14</figref>;</li><li><figref idref="f0007">Figure 16</figref> - shows a perspective view of another embodiment of an abutment for use with the fixture of <figref idref="f0006">Figure 14</figref>;</li><li><figref idref="f0007">Figure 17</figref> - shows a perspective view of yet another embodiment of an abutment for use with the fixture of <figref idref="f0006">Figure 14</figref>;</li><li><figref idref="f0008">Figure 18</figref> - shows the abutment of any one of <figref idref="f0006 f0007">Figures 15 to 17</figref> in place in the fixture of <figref idref="f0006">Figure 14</figref>;</li><li><figref idref="f0008">Figure 19</figref> - shows a close-up view of the seal provided by the arrangement of <figref idref="f0008">Figure 18</figref>;</li><li><figref idref="f0009">Figure 20</figref> - shows a different embodiment of an abutment;</li><li><figref idref="f0009">Figure 21</figref> - shows the abutment of <figref idref="f0009">Figure 20</figref> engaging with a fixture;</li><li><figref idref="f0009">Figure 22</figref> - shows a close-up of a seal provided by the arrangement of <figref idref="f0009">Figure 21</figref>;</li><li><figref idref="f0010">Figure 23</figref> - shows an embodiment of a medical implant system with a seal provided between the abutment and the abutment screw;</li><li><figref idref="f0010">Figure 24</figref> - shows another embodiment of a medical implant system with a seal provided between the abutment and the fixture;</li><li><figref idref="f0011">Figure 25</figref> - shows another embodiment of a medical implant system with a seal provided between the abutment and the abutment screw as well as between the abutment and the fixture;</li><li><figref idref="f0012">Figure 26A</figref> - shows a flow chart of a method of implanting a medical implant system;</li><li><figref idref="f0012">Figure 26B</figref> - shows a specific example of the method of <figref idref="f0012">Figure 26A</figref>;</li><li><figref idref="f0012">Figure 27A</figref> - shows a cross section of the arrangement of the first step of the method of <figref idref="f0012">Figure 26B</figref>;</li><li><figref idref="f0013">Figure 27B</figref> - shows a cross section of the arrangement of the second step of the method of <figref idref="f0012">Figure 26B</figref>; and</li><li><figref idref="f0013">Figure 27C</figref> - shows a cross section of the arrangement of the third step of the method of <figref idref="f0012">Figure 26B</figref>;</li></ul>

DESCRIPTION

0011<figref idref="f0001">Figure 1</figref> shows a side view of a medical implant system 100. The implant system has an abutment 10 that enables a hearing device to be coupled through a percutaneous connection to a bone anchoring device. Abutment 10 is connected to fixture 20. Fixture 20 has a base collar 21 and a screw thread 22. In use, screw thread 22 is screwed into bone of the user to fixate and retain fixture 20 to the user's skull for example.

0012As can be seen in <figref idref="f0001">Figure 2</figref>, which shows a cross section view along the line A-A' of <figref idref="f0001">Figure 1</figref>, abutment 10 is connected to and retained to fixture 20 by abutment screw 30. Abutment screw 30 has head 31, a well 32 within the head 31 to receive an insertion tool or the like, and an apical outer screw thread 34 on an elongate main body 33. In some examples, abutment screw 30 may be an M 1.8 titanium screw and the well 32 in head 31 may be a tubular hex configuration for receiving and cooperating with the insertion tool (not shown). The apical outer screw thread 34 engages with inner screw thread 23 of the fixture 20 upon turning of the insertion tool.

0013<figref idref="f0002">Figure 3</figref> shows a perspective view of the medical implant system 100. In this view, the abutment interior 13 is visible, showing the abutment interior base 14. Also visible in this view is abutment screw 30 with head 31 and hexagonal well 32. The fixture 20 with base collar 21 and outer screw thread 22 is also visible.

0014<figref idref="f0002">Figure 4</figref> shows a cross section view of the three main constituent parts of the medical implant system 100 separated. There shown are abutment screw 30, abutment 10 and fixture 20.

0015<figref idref="f0003">Figure 5A</figref> shows one embodiment of abutment screw 30 according to one aspect of the present disclosure. In particular, abutment screw head base 35 includes a deformable element in the form of a flange 36, which is angled downwards and outwards away from the head at a flange angle of about 10 degrees (in one example). <figref idref="f0003">Figure 5B</figref> shows a cross section view of the abutment screw 30 of <figref idref="f0003">Figure 5A</figref>. In this view, the deformable element in the form of the flange 36 is clearly visible.

0016In one embodiment, the outer portion of the flange 36 has a flat portion 37 (see <figref idref="f0003">Figure 5C</figref> showing a close up view) which in use, rests on a corresponding contact surface, in this case, the abutment interior base 14 as shown in <figref idref="f0003">Figure 6</figref>. The deformable element is able to deform to form a seal. In one example, when the abutment screw 30 is screwed down into the inner screw thread 23 of fixture 20, flat portion 37 comes into contact with the corresponding contact surface or abutment interior base 14. When the abutment screw 30 is screwed further downwards, the deformable element or flange 36 with flat portion 37 is pressed downwards and outwards against the corresponding contact surface or abutment interior base 14 and thereby deformed to provide a seal between the abutment screw 30 and the corresponding contact surface, in this case abutment interior base 14. In other words, the deformable element deforms to provide a seal between the abutment screw 30 and the abutment 10, upon tightening of the abutment screw 30.

0017In other examples, the deformable element may deform upon application of downward pressure on the, or a part of the, implant system, such as on the screw head 31.

0018In various examples, the type of deformation may be plastic, elastic or a combination of both.

0019<figref idref="f0003">Figure 7</figref> shows a close up view of this engagement between the abutment screw 30 and the abutment 10, and in particular, shows how the deformation of the deformable element as flange 36 and the flat portion 37 is deformed and pressed into the surface of the abutment interior base 14, to provide a seal. In some cases, the corresponding contact surface, in this case the abutment interior base 14, may itself also deform slightly to further increase the seal formed therebetween.

0020As the contact surface increases by this deformation, any surface imperfections between the contacting surfaces might be compensated for, which reduces any gaps or holes for microbes (including fungi and bacteria) to pass through.

0021This thereby provides a seal to reduce the risk of bacterial infection via the micro leakage pathway, starting at the abutment and abutment screw interface.

0022While the screw head 31 of abutment screw 30 may in some embodiments, have a screw thread as shown in <figref idref="f0003">Figures 5A, 5B, 5C and 6</figref>, which may assist in providing the deformable element as flange 36, in other embodiments, head 31 need not have a screw thread and the deformable element may be provided by any suitable structure including simply providing an annular relief 38 above flange 36 to allow the deformation, as shown in <figref idref="f0004">Figure 8</figref>.

0023In another embodiment, as shown in a cross section view in <figref idref="f0004">Figure 9A</figref>, the deformable element may be provided on the base of the head 31 by way of an annular ring 39 surrounding the outer edge of the abutment screw head base 35. <figref idref="f0004">Figure 9B</figref> shows a perspective view of this arrangement. As in the previous example, when abutment screw 30 is tightened into position, the deformable element in the form of annular ring 39, is deformed so as to form a seal between the abutment screw 30 and the abutment 10. <figref idref="f0004">Figure 10</figref> shows a close up view of this seal formed by the deformation of the deformable element. Again, in some cases, the abutment interior base 14 may also be slightly deformed.

0024In another embodiment, the deformable element may be provided on the abutment itself. <figref idref="f0005">Figure 11</figref> shows a perspective view of abutment 10 showing abutment interior 13 providing an abutment receiving well for receiving the abutment 10, and abutment interior base 14. Without abutment screw 30, the through bore 16, into which abutment screw 30 is inserted in use, is visible. In this embodiment, the deformable element is provided by an annular ring 17 surrounding the through bore 16. <figref idref="f0005">Figure 12</figref> shows a cross section view of abutment 10 with annular ring 17 surrounding through bore 16. Again, as abutment screw 30 is inserted into through bore 16 and tightened, the base 35 (in this case providing the corresponding contact surface) of head 31 will be compressed over deformable element, in this case, annular ring 17, so as to deform it to provide a seal between abutment screw 30 and abutment 10. This again provides a barrier to bacteria entry into the micro leakage path and reduces risk of infection. In this case, the base 35 of head 31 may be planar rather than angled as in a previous example.

0025<figref idref="f0005">Figure 13</figref> shows a close up view of the seal so formed, showing the deformation of deformable element, in this case, annular ring 17. In one example, the height of annular ring 17 is about 0.05mm and the width of annular ring 17 is about 0.05mm. Of course, any other suitable dimensions may be used, including but not limited to about 0.01mm to about 0.1mm, about 0.04mm, about 0.06mm, about 0.03mm and about 0.07mm or any combination thereof.

0026The above embodiments have provided examples of forming the seal between the abutment screw 30 and the abutment 10. In other embodiments and aspects, the seal may alternatively, or also, be formed between the fixture 20 and the abutment 10.

0027In one embodiment of this aspect, as shown in <figref idref="f0006">Figure 14</figref>, fixture 20 is provided with an annular corner 26 on lip 25 of the abutment receiving well, which defines the fixture interior 24. The abutment base 12 of abutment 10 is received in fixture interior 24 to be retained by tightening the abutment screw 30 as previously described. <figref idref="f0006">Figures 15</figref>, <figref idref="f0007">16 and 17</figref> show various examples of abutment 10 configurations that may be used in this aspect.

0028In this example, the fixture interior 24 of the fixture 20 has a bottom geometrical configuration, for instance a lobe shaped geometrical configuration 27, and the protruding bottom part of the abutment 10 has a corresponding geometrical configuration 18 as illustrated in <figref idref="f0006">figures 15</figref>, <figref idref="f0007">16 and 17</figref>, to prevent rotation between these two parts when coupled together.

0029The abutment 10 might have a substantially curved, conical outer surface with the upper edge having the wider diameter and the bottom, fixture-connecting part having a smaller diameter, as illustrated. A common feature in these particular embodiments for the three different examples of abutments 10 illustrated in <figref idref="f0006">Figures 15</figref>, <figref idref="f0007">16 and 17</figref> is the bottom tapered outer surface 12 which cooperates with the annular corner 26 of the fixture 20 when the two parts are coupled together as shown in <figref idref="f0008">Figure 18</figref>. This provides a concave outer contour of the connection between the abutment and the fixture.

0030In this example, the deformable element is provided by the annular corner 26. When the abutment 10 is placed in the fixture 20 and the abutment screw 30 is tightened as previously described, the abutment base 12, (in this case acting as the corresponding contact surface) is pressed down onto annular corner 26, which deforms to provide a seal between abutment 10 and fixture 20. <figref idref="f0008">Figure 19</figref> shows a close up view of the seal formed therebetween.

0031The deformable element may also deform upon application of other force, such as by downward pressure on abutment 10, rather than, or in conjunction with, tightening of the abutment screw 30.

0032In some embodiments, the outer surface of the abutment 10 and/or the fixture 20 might be modified in order to improve the skin tissue integration. Different types of structured or coated surfaces might be used, for instance hydroxyapatite (HA) coated surfaces. In this case it should be understood that the coating might be applied on the fixture and the abutment separately, or applied on a pre mounted implant device.

0033In a further embodiment of this aspect, the deformable element may be provided on the abutment 10 as shown in <figref idref="f0009">Figure 20</figref>. In this embodiment, the deformable element is provided by abutment annular corner 19 on the abutment base 12. In this embodiment, the lip 25 of fixture 20 may be a more conventional rounded shape, which provides the corresponding contact surface for the deformable element, in this case, abutment annular corner 19. As in the previous example, abutment 10 is placed in the fixture 20 and when abutment screw 30 is tightened, abutment 10 is pressed down onto fixture 20. In this arrangement, deformable element (abutment annular corner 19) will be deformed against the lip 25 to form a seal between the abutment 10 and the fixture 20. <figref idref="f0009">Figure 22</figref> is a close up view of the seal formed therebetween.

0034<figref idref="f0010">Figure 23</figref> shows an example of another embodiment of a medical implant system 100, comprising abutment 10, fixture 20 and abutment screw 30. In this example, the system is designed so as to provide a seal between the abutment 10 and the abutment screw 30. In this case, this seal is provided by the same arrangement as described earlier with reference to <figref idref="f0003">Figures 5A, 5B, 5C, 6 and 7</figref>. That is, that the deformable element is provided on the abutment screw 30 in the form of an angled flange that upon tightening of abutment screw 30 (or application of other force), deforms against the corresponding contact surface (in this case abutment interior base 14) to form the seal.

0035<figref idref="f0010">Figure 24</figref> shows another embodiment of a medical implant system 100 comprising abutment 10, fixture 20 and abutment screw 30. In this example, the system is designed to provide a seal between abutment 10 and fixture 20. In this case, the seal is provided by the same arrangement as described earlier with reference to <figref idref="f0006 f0007 f0008">figures 14 to 19</figref>. That is, that the deformable element is provided on the fixture 20 in the form of an annular corner 26 provided on the lip 25 of fixture 20, that upon tightening of abutment screw 30 9or application of other force), deforms against the corresponding contact surface (in this case abutment base 12) to form the seal.

0036<figref idref="f0011">Figure 25</figref> shows yet another embodiment of a medical implant system 100 comprising abutment 10, fixture 20 and abutment screw 30. In this example, the system is designed to provide a seal between the abutment 10 and the abutment screw 30 as well as between the abutment 10 and fixture 20. In this case, the first seal is provided by the same arrangement as described above with reference to <figref idref="f0010">Figure 23</figref> That is, that the deformable element is provided on the abutment screw 30 in the form of an angled flange that upon tightening of abutment screw 30 (or application of other force), deforms against the corresponding contact surface (in this case abutment interior base 14) to form the seal. The second seal is provided by the arrangement described above with reference to <figref idref="f0010">Figure 24</figref>. That is, that the deformable element is provided on the fixture 20 in the form of an annular corner 26 provided on the lip 25 of fixture 20, that upon tightening of abutment screw 30 9or application of other force), deforms against the corresponding contact surface (in this case abutment base 12) to form the seal. Accordingly, the arrangement of <figref idref="f0011">Figure 25</figref> is a combination of both the arrangements of <figref idref="f0010">Figures 23 and 24</figref>.

0037In yet further embodiments, any combination of any two or more of the seals previously described may be used, including two different seals provided between the abutment 10 and the abutment screw 30 as shown in <figref idref="f0003 f0004">Figures 5 to 10</figref> as well as <figref idref="f0005">Figures 11 to 13</figref>.

0038It will be appreciated that the various deformable elements described may be provided by any suitable means, including by turning, during or after the usual component production process.

0039The provision of the deformable element(s) in the various components of the medical implant system 100 provide for a unique method of implanting the medical implant system.

0040The steps of one possible method of implanting the medical implant system 100 are shown in <figref idref="f0012">Figure 26A</figref>. At step 200, the abutment 10 is located in the abutment receiving well of fixture interior 24 of the already implanted fixture. At step 201, the abutment screw 30 is inserted in the through bore 16 of the abutment 10 and into the fixture 20. In step 202, force is applied to the implant system until the deformable element(s) deforms to provide the seal(s) between the various components of the medical implant system, thereby reducing the risk of infection in the user or patient. In one example, the force may be applied by way of pressure on the abutment.

0041In another example, as shown in <figref idref="f0012">Figure 26B</figref>, the same steps 200 and 201 may be used, however, in step 202', the force may be applied by way of tightening the abutment screw 30. In one example, the abutment screw is tightened using a torque of greater than about 15Ncm, and including about 15Ncm to about 20Ncm, and about 20Ncm to about 30Ncm. In one particular example, the torque used is about 25Ncm.

0042In some embodiments, the, or part of, the surfaces of one or more of the components, such as the abutment screw 30 may be coated with a friction-reducing material such as diamond like carbon (DLC). In these embodiments, the required torque or other force will be reduced.

0043<figref idref="f0012">Figures 27A</figref>, <figref idref="f0013">27B and 27C</figref> illustrate these steps 200, 201 and 202'. In <figref idref="f0012">Figure 27A</figref>, the abutment 10 is located inside fixture 20. In this example, fixture 20 has already been implanted and anchored in the bone 50 of the patient's skull, in a previous procedure and allowed to heal. This example method therefore begins with the location of the abutment 10 in fixture 20. This is done through an opening created in the tissue 5 of the patient.

0044In <figref idref="f0013">Figure 27B</figref>, the abutment screw 30 is inserted into the abutment 10 and the fixture 20 and in <figref idref="f0013">Figure 27C</figref>, the abutment screw 30 is tightened using an insertion tool 40. This tightening causes any deformable elements in the system to deform and form seals to reduce the risk of bacteria entering into the micro leakage path and thus reducing risk of infection.

0045The seals may be provided as previously described, between the abutment screw 30 and the abutment 10, the abutment 10 and the fixture 20, or both, with the locations of these discernible from the dotted lines superimposed on <figref idref="f0013">Figure 27C</figref>.

0046Throughout the specification and the claims that follow, unless the context requires otherwise, the words "comprise" and "include" and variations such as "comprising" and "including" will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers.

0047While the various aspects and embodiments disclosed herein have been described in the context of various examples, it will be understood that many variations and modifications may be made within the scope of the following claims.