GB2268409A

GB2268409A - Bone implant

Info

Publication number: GB2268409A
Application number: GB9313550A
Authority: GB
Inventors: Gerald Frederick Mills
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-07-01
Filing date: 1993-07-01
Publication date: 1994-01-12
Anticipated expiration: 2013-07-01
Also published as: GB9313550D0; GB2268409B; GB9213942D0

Abstract

A bone implant (1), particularly for dental use, has a body (2) defining a seat (9) which opens in at least one end of the body to receive a prosthesis, and a plurality of fingers (3) which radiate from the other end of the body (2) and can be bent to follow the contour of the bone to anchor the implant (1) to the bone in use. A respective barb (8) projects from the end of each finger (3) to engage the bone and secure the implant when it is first fitted. <IMAGE>

Description

BONE IMPLANT The present invention relates to bone implants.

Conventional bone implants for general medical or dental use have a blade or root which is implanted in a relatively. deep cavity in the bone. The use of these implants is precluded, however, in cases where the drilling or other preparation of the cavity would damage a sinus or nerve tissue or where the bone quality is poor.

The object of the present invention is to provide a bone implant which does not require such a deep cavity as a conventional blade- or root-type implant and thus avoids the drawbacks or obstacles to use of these conventional implants.

Accordingly, the present invention provides a bone implant, particularly but not exclusively for dental 'use, comprising a body defining a seat which opens in at least one end of the body to receive a prosthesis and a plurality of flexible fingers which extend from the body adjacent its other end and can be bent to follow the contour of the bone to anchor the implant to the bone in use, at least two fingers on opposite sidesof the body having respective barbs at or adjacent their free ends for engaging the bone to secure the implant when it is first fitted. Preferably, there is a barb on each finger.

The implant is made from a biocompatible material, preferably titanium or an alloy thereof, and may be covered by a biocompatible material, such as GORTEX (trade mark) or a resorbable material, for promoting the growth or regeneration of bone over the implant.

The covering material may be bonded or applied to the surface of the implant as a coating during manufacture or may be placed over the implant once it is emplaced in the bone.

The body may be rigid, with a seat of predetermined fixed orientation, or it may comprise parts which can be adjusted angularly relative to one another to enable the orientation of the prosthesis to be selected and which can then be locked or clamped rigidly together prior to the fitting of the implant to set the selected orientation.

In its rigid embodiment, the body is preferably in the form of a right prism, for example a hexagonal right prism, with a respective finger extending from each side but it may be cylindrical or of some other shape as appropriate. The seat in the body may be a central blind hole or through-hole and may be threaded, plain or in the form of a shaped socket, in dependence on the type of prosthesis to be received therein.

In its angularly adjustable embodiment, the body is hollow and houses a nut which defines the seat and with which a screw-threaded post carried by or connectible with the prosthesis is engageable through a hole or slot in the said one end of the body, the post, the body and the nut having complementary part-spherical surfaces which cooperate in the manner of a ball joint so that the post and the nut can be moved angularly relative to the body into a selected orientation, the nut then being tightened on the post to clamp the latter relative to the body in the selected orientation.Preferably, the body is dome-shaped, with the hole or slot at its apex, and has a part-spherical concavity which opens towards the said other end and in which the nut is captive, and the nut is of a shape, for example elliptical or hexagonal, such that it positively engages the surface of the cavity of the body to prevent it from moving relative to the body when it is tightened in the selected orientation.

Preferably, the fingers project radially from the body and are substantially flat with holes through which bone can grow to ensure a firm anchorage as a result of osteointegration. The fingers may have strengthening ribs along their opposite edges and/or along their median lines; in the latter case, the holes may be in rows on each side of the median ribs. The ribs also increase the surface of the fingers in contact with the bone and afford some degree of keying or mechanical bonding between the bone and the fingers.

The strengthening ribs are preferably upstanding from those surfaces of the fingers which face in the direction of the said one end of the body, that is, the surfaces of the fingers opposite those which are in contact with the bone upon initial fitting of the implant, as described below. In this case, the ribs may also hold the covering of bone-regenerating material away from the surfaces of the fingers so that bone can grow through the holes into the channels or valleys between the ribs, beneath the covering material.

The barbs may comprise prongs which project from the free ends of the contact surfaces of the fingers (that is, those surfaces which are in contact with the bone upon initial fitting of the implant) or they may normally lie in or parallel to the planes of the respective fingers and be bendable out of those planes for engagement with the bone upon fitting of the implant. The bendable barbs may comprise pre-cut or pre-stamped portions of the fingers and be attached thereto by integral hinges or zones of flexure.

To facilitate the bending of the fingers, and the trimming thereof if necessary, the fingers may have transverse zones in which the ribs are interrupted, flattened or of reduced height, where the fingers join the body and at intervals along their length.

The invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a plan view of a bone implant according to one embodiment of the present invention; Figure 2 is a cross-section on the line II-II of Figure 1; Figure 3 is a fragmentary plan view, on an enlarged scale, of one of the fingers of a bone implant according to a variant of the present invention, and Figure 4 is a cross-section similar to Figure 2, of a second embodiment of the invention.

With reference to Figures 1 and 2, a bone implant 1 for dental use comprises a rigid hub-like body 2 which is in the form of a hexagonal right prism and six flexible fingers 3 which project radially from the sides of the body adjacent one end thereof. The body 2 and the fingers 3 are made in one piece from titanium or an alloy thereof. The implant 1 is covered by a biocompatible bone-regenerating material, such as GORTEX (trade mark), which promotes the growth of bone over the implant in use. This latter material may be applied to the implant as a coating or may simply be placed over the implant as a cover once it is emplaced at the implant site in use.

The fingers are substantially flat but have strengthening ribs 4, 5 along their edges and their median lines respectively. The ribs 4, 5 are upstanding from those surfaces of the fingers 3 which face the opposite end of the body 2. The ribs 4, 5 have narrow transverse zones or nodes 6 of reduced height where the fingers 3 join the body 2 and at intervals along the length of the fingers 3 to facilitate the bending or trimming of the fingers 3 in use.

On each side of the median rib 5, each finger 3 has a row of holes 7 through which bone can grow during the process of osteointegration of the emplaced implant 1 in use. In addition, each finger 3 has a barb 8 at or adjacent its free end, on the surface opposite the ribs 4, 5.

In Figure 2, each barb 8 comprises a curved prong which projects from the end of the said surface of the finger but, in the variant of Figure 3, each barb comprises a bendable portion 18 of the finger 3, adjacent its free end, the portion 18 being pre-stamped from the finger and being connected thereto by an integral hinge 28.

The bendable portion 18 normally lies in the plane of the respective finger 3 and can be bent out of that plane to form a projecting barb when the implant 1 is to be fitted.

The body 2 defines a central seat 9 which receives a prosthesis (not shown) in use. This seat 9 may be in the form of a blind hole or a through-hole, may be threaded along a part or the whole of its length, or may be plain. The seat may also be of a size or shape suitable to accommodate a conventional blade- or root-type implant so that the implant 1 of the invention can be used to reinforce the latter.

In the embodiment of Figures 1 and 2, the seat 9 in the rigid body 2 is at a predetermined, fixed orientation, normally coaxial with the axis of the body, but, in the embodiment of Figure 4, the body 20 permits a degree of angular adjustment so that the orientation of the prosthesis can be selected and set prior to the fitting of the implant. As illustrated, the embodiment of Figure 4 has the bendable barb portions 18 of Figure 3.

In Figure 4, the body 20 is dome-shaped and has a part-spherical cavity 21 opening towards the end from which the fingers 3 radiate and housing a captive nut 22. The nut 22 defines the seat 9 and a screw-threaded post 23 to which the prosthesis can be attached isengaged therein through a hole at the apex of the body 20. As shown, the body 20, the nut 22 and the post 23 have complementary part-spherical surfaces which cooperate in the manner of a ball joint to enable the nut 22 and the post 23 to be moved angularly relative to the body 20 into a selected orientation for the prosthesis which is to be attached to the post 23 in use. The nut 22 is then tightened on the post 23 to clamp the latter against the body 20 in the selected orientation.The nut 22 is hexagonal or-elliptical in shape so that it positively engages the surface of the concavity 21 when it is tightened to prevent movement by the post 23 away from the selected orientation.

In use, subperiostal flaps of tissue are raised, for example, at the crest of the lower jaw to expose the cortical bone of the jaw at the implant site and an implant 1 of appropriate size is placed on the bone, the fingers 3 being bent to follow the contour of the bone and effectively to embrace the bone. The position of the implant 1 is marked on the bone by means of a titanium scribe and, the implant 1 being taken away, the cortical bone is then removed or perforated, following the outline of the implant or over the general area to be occupied thereby, to expose the underlying cancellous bone or to allow the migration of cancellous bone cells.After a final check that the hole through the cortical bone is correctly aligned relative the desired position of the implant 1, the fingers 3 are bent slightly beyond their desired position and the implant 1 is then pushed home onto the cancellous bone so that the barbs 8 are drawn along the surface of the bone and engage the latter mechanically to secure the implant 1 immediately upon fitting. If necessary, screws (not shown) may be inserted into thebone through at least some of the holes 7 to afford additional initial anchorage.

Once the implant 1 is in place, the flaps of tissue are replaced around it and a suitable healing period is allowed, during which the implant is anchored by osteointegration as the cancellous bone grows through the holes 7 and over the ribs 4, 5 of the fingers 3.

After the healing period, the central seat 9, or the post 23 in the embodiment of Figure 3, is exposed and a prosthesis with appropriate transmucosal fittings is inserted in the seat 9, or fitted to the post 23, in a conventional manner. Once the prosthesis is fitted, the implant 1 may be subjected to progressive loading, again in a conventional manner.

As stated above, the covering material promotes the growth of bone around the implant but, if the covering is of a non-resorbable material, this material must be removed after the healing period when the central seat 9 or the post 23 is exposed for the fitting of the prosthesis. If the covering material is not in the form of an integral coating on the implant 1, it is placed over the implant 1 before the tissue is replaced after initial fitting, as described above. In this case, the covering material may be retained by a cover screw which is fitted into the central seat 9 or a cap which is fitted onto the post 23, to prevent any slippage of the material. In these cases, it may be necessary to allow a little tissue relief around the body 2, 20 of the implant 1.

The implant 1 of the invention may be used to reinforce a conventional blade- or root-type implant. In this case, the conventional implant is fitted first and the implant 1 of the invention is emplaced around it in the manner described above. The two implants may be joined together using a conventional cover screw as used with the blade- or root-type implant.

The implant 1 of the invention has a number of advantages compared with conventional, submerged bladeor root-type implants. Firstly, the implant 1 does not require a deep cavity in the bone but requires only that the bone be drilled as far as the cancellous layer. This means that the implant 1 is not so dependent on the bone density and quality as conventional implants and can be used in all areas of the mouth, even where a sinus or bundle of nerves precludes the use of a conventional implant.

Secondly, the divergent configuration of the fingers 3 allows a greater discharge of forces to the bone than is possible with conventional implants. The fingers 3 themselves can easily be removed or shortened to allow several implants 1 to be fitted side by side along the jaw. The fingers 3 may be formed with a plurality of bendable barb portions 80 at intervals along their lengths so that barbs will still be present even if the fingers are shortened.

Thirdly, the covering material which promotes the growth of bone may lead to new bone growth which is thicker and denser than the bone which was removed to enable the implant to be fitted, so that the quality of bone is better after implantation than before. This makes the implant 1 particularly suitable for reinforcing conventional implants which are already in position but are at risk because of poor bone density or quality. The implant 1 can be made to fit existing implants and to use their fittings.

The configuration of the implant 1 of the invention allows it to be produced by a relatively cheap stamping process, requiring only minor machining at the finishing stage.

Since the implant 1 can be used anywhere in the mouth and is not dependent on the nature of the underlying bone, the implants can be prepared in advance in various sizes and with various, standard commercially-made superstructures for use in predetermined positions in the mouth. This greatly reduces the laboratory time and costs compared with conventional implants which have to be made to individual requirements.

Claims

1. A bone implant, particularly but not exclusively for dental use, comprising a body defining a seat which opens in at least one end of the body to receive the prosthesis, and a plurality of flexible fingers which extend from the body adjacent its other end and can be bent to follow the contour of the bone to anchor the implant to the bone in use, at least two fingers on opposite sides of the body having respective barbs at or adjacent their free ends for engaging the bone to secure the implant when it is first fitted.

2. An implant according to Claim 1, in which it is made from titanium or an alloy thereof and is covered by a biocompatible or resorbable material for promoting the growth or regeneration of bone over the implant.

3. An implant according to Claim 2, in which the covering material is bonded or applied to the surface of the implant as a coating during manufacture.

4. An implant according to Claim 2, in which the covering material is placed over the implant once it is emplaced in the bone.

5. An implant according to any one of the preceding claims, in which the body is rigid with a seat of predetermined, fixed orientation.

6. An implant according to Claim 5, in which the body is in the form of a right prism, with a central hole constituting the seat and with a respective finger extending from each side of the prism.

7. An implant according to any one of Claims 1 to 4, in which the body comprises parts which can be adjusted angularly relative to one another to enable the orientation of the prosthesis to be selected and which can then be locked or clamped rigidly together prior to the fitting of the implant to set the selected orientation.

8. An implant according to Claim 7, in which the body is hollow and houses a nut which defines the seat and with which a screw-threaded post carried by or connectible with the prosthesis is engageable through a hole or slot in the said one end of the body, the post, the body and the nut having complementary part-spherical surfaces which cooperate in the manner of a ball joint so that the post and the nut can be moved angularly relative to the body into a selected orientation, the nut then being tightened on the post to clamp the latter relative to the body in the selected orientation for the prosthesis.

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9. An implant according to Claim 8, in which the body is dome-shaped, with the hole or slot at its apex, and has a part-spherical concavity which opens towards the said other end and in which the nut is captive.

10. An implant according to Claim 8 or Claim 9, int which the nut is of a shape such that it positively engages the surface of the cavity of the body to prevent it from moving relative to the body when it is tightened in the selected orientation.

11. An implant according to any one of the preceding claims, in which the fingers project radially from the body and are substantially flat with holes through which bone can grow to ensure a firm anchorage as a result of osteo-integration.

12. An implant according to any one of the preceding claims, in which the fingers have strengthening ribs along their opposite edges and/or along their median lines.

13. An implant according to Claim 12, in which the holes in the fingers are in rows on each side of the median ribs.

14. An implant according to Claim 12 or Claim 13, in which the strengthening ribs are upstanding from those surfaces of the fingers which face in the direction of the said one end of the body.

15. An implant according to Claim 12, Claim 13 or Claim 14, in which the strengthening ribs are interrupted or of reduced height in transverse zones where the fingers join the body and at intervals along the length of the fingers, to facilitate bending and/or trimming of the fingers.

16. An implant according to any one of the preceding claims, in which there is a barb on each finger.

17. An implant according to any one of the preceding claims in which the barbs comprise prongs which project from the free ends of those surfaces of the fingers which are in contact with the bone upon initial fitting of the implant.

18. An implant according to any one of Claims 1 to 16, in which the barbs normally lie in or parallel to the planes of the respective fingers and are bendable out of those planes for engagement with the bone upon fitting of the implant.

19. An implant according to Claim 18, in which the bendable barbs comprise pre-cut or pre-stamped portions of the fingers and are attached thereto by integral hinges or zones of flexure.

20. A bone implant, particularly but not exclusively for dental use, substantially as herein described with reference to, and as shown in, the accompanying drawings.