Patent Description:
The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

Osseointegration is a technique which provides amputee patients with a prosthetic implant which is integrated with the skeleton of a patient. That is, an implant where there is direct contact between living bone and the surface of a load bearing implant. Osseointegration dramatically enhances bone and joint replacement surgery by providing much stronger and longer lasting implants, which in turn provides greater quality of life for amputees.

In some currently utilised osseointegration implants, a skeletally integrated implant is connected through an opening in the stump of an amputee to an external prosthetic limb. This allows direct contact to the ground, which provides greater stability, more control and minimizes energy exerted.

As there is a direct connection between the implant and the external prosthetic limb, there is no need for a patient to use a so-called "suction" prosthesis. Patients that are unable to wear a suction prosthesis for long periods of time or those confined to a wheel chair may benefit from osseointegration implants. Indeed, bilateral amputees have been able to become mobile through osseointegration.

In some other currently utilised osseointegration implants, such as for example the implants of <CIT>, which discloses the technical features of the preamble of claim <NUM>, <CIT> and <CIT>, part of the implant forms an abutment against the cut bone with portions of the implant extending beyond outside the cut bone. In these circumstances an implant-abutment interface is formed by abutment against the cut bone. In such a high stress region, this implant-abutment inevitably creates small gaps between the implant and the bone. These small gaps present regions within which bacteria may colonise, potentially causing inflammation and infection.

In the other currently utilised osseointegration implants mentioned above with reference to <CIT>, <CIT> and <CIT> there is a region of the implant extending outwardly from the implant-abutment that interfaces with the patient's soft tissue causing friction between the soft tissue and implant.

It is against this background that the present invention and embodiments of the present invention have been developed.

The present invention provides an implant as set forth in the accompanying claims.

The at least one end including the enlarged portion may be arranged so that the end is flush with the end of the skeletal bone when implanted.

The width of the enlarged portion may be narrower than the width of the skeletal bone so that the enlarged portion sits entirely within the recess formed in an end of the skeletal bone.

The body may include a coating arranged to assist osseointegration of the implant into the skeletal bone. In one embodiment, the coating includes a porous structure arranged to assist osseointegration of the implant into the existing skeletal bone. The porous structure may be formed from titanium, which may in turn be formed by a plasma deposition process.

The implant may be sized to be integrated into a human femoral bone. The implant may also have a curved shape, arranged to mimic the curve of a human femoral bone.

The implant may be sized to be integrated into a portion of a human tibial bone. The implant may also have a curved shape, arranged to mimic the curve of a human tibial bone.

In one embodiment, the body of the implant further includes at least one projection which extends along a portion of the body, wherein the projection is arranged to, in use, prevent rotation of the implant relative to the skeletal bone. The projection may be at least one spline. The implant may include a plurality of splines which may extend longitudinally along the body of the implant.

The implant may have a second end, wherein the second end is tapered.

The physiologically inert substance may be niobium.

The body may include a screw hole proximal to the enlarged portion arranged to receive a fixing device arranged to fix the body to the skeletal bone.

The implant may further include a coupling portion at the at least one end of the implant. The coupling portion may include a threaded portion arranged to receive a corresponding coupling portion on a prosthetic device.

There is also disclosed a method of surgically implanting an implant into a skeletal bone of a patient. The method does not form part of the present invention. It comprises the steps of forming a longitudinal cavity in the bone of the patient, the cavity being arranged to, in use, receive the implant, wherein the cavity comprises at least one end wherein the at least one end of the cavity further comprises a stepped portion formed to substantially mimic the shape of the implant, and implanting the implant into the cavity.

There is further disclosed a method of surgically preparing a skeletal bone of a patient for receiving an implant. The method does not form part of the present invention. It comprises the step of forming a longitudinal cavity in the bone of the patient, the cavity comprising at least one end, the cavity arranged to, in use, receive the implant, wherein the at least one end of the cavity further comprises a stepped portion formed to substantially mimic the shape of the implant.

Further features of the present invention are more fully described in the following description of several non-limiting embodiments thereof. This description is included solely for the purposes of exemplifying the present invention. It should not be understood as a restriction on the broad summary, disclosure or description of the invention as set out above. Of the following embodiments, only embodiments three (<NUM>), five (<NUM>), seven (<NUM>) and eight (<NUM>) form part of the present invention since their respective enlarged portions are stepped outwardly from their respective bodies. The remaining embodiments do not form part of the present invention and serve illustrative purposes only. The description will be made with reference to the accompanying drawings in which:.

Broadly, embodiments of the present disclosure relate to an implant arranged for integration into an existing skeletal bone of a patient. Such implants are generally referred to as "osseointegrative" implants. The implants of the present disclosure are particularly suited for implantation into long bones such as the femur, tibia or humerus.

In the ensuing description, like reference numerals in consecutive Figures refer to like or functionally identical parts.

The embodiment described herein, with reference to <FIG>, an implant <NUM> which a body <NUM> having a distal end <NUM>. The implant <NUM> is well suited for integration into a femur. This does not suggest that the implant <NUM> is solely suitable for use with a femur.

In one arrangement the implant <NUM> is forged titanium chosen for its biocompatibility. The skilled addressee will recognize that alternative materials that are biocompatible can be used such as titanium alloys, composite materials or otherwise.

The body <NUM> is elongate as it is arranged to substantially mimic a portion of a skeletal bone. In the embodiment described herein, the implant <NUM> is designed to be implanted in the leg of a patient, as a partial replacement for the femur bone of a patient. The patient is an amputee who is seeking to use a prosthetic limb and requires the implant to serve as an "attachment" point for the prosthetic limb.

The distal end <NUM> which includes a flared portion <NUM>, that is enlarged with respect to the body <NUM>, arranged to, in use, prevent migration of the implant into the flesh of a patient. Osseointegrative implants suffer from the issue of the 'end' of the implant, which is necessarily open to the air and passes through the flesh and skin of a patient, being slowly 'pushed upwards' (i.e. upwardly migrating) when the patient wears a prosthetic limb which exerts upward pressure on the implant and therefore can cause the end of the implant to migrate into the flesh of the leg of the patient. The embodiment described herein, in contrast, utilizes a flared portion <NUM> to prevent such 'upward migration' of the implant into the leg of the patient.

The flared portion <NUM> is sized and shaped to sit within a recess <NUM> formed in the exposed end <NUM> of the bone <NUM> (shown in <FIG>). As a result of this the flared portion <NUM> has a perimeter that is smaller than that of the skeletal bone it is to be inserted into. The recess <NUM> is shaped so that the end of the flared portion <NUM> is flush with the end of the bone <NUM>.

As the flared portion <NUM> is flush with the end of the bone <NUM> after the implant is inserted, a surgeon can suture the skin to the outside of the bone surrounding the implant. As the flared portion <NUM> does not extend beyond the end of the bone <NUM> no site is presented for a bacteria colony to develop. This greatly reduces the risk of inflammation, infection and destruction of tissue around the implant site due to bacterial activity.

Also, as the flared portion <NUM> is flush with the end of the bone <NUM> after the implant is inserted, the soft tissue surrounding the bone <NUM> does not adhere to the implant. As a result forces transmitted through the implant <NUM>, such as through walking or otherwise, are directly transferred through the implant <NUM> and bone <NUM> and are not dissipated either through a socket or through soft tissue. This minimizes energy loss.

The end of the flared portion <NUM> is coated with nano particles or is highly polished to minimize the friction between the soft tissue surrounding the implant and resultant irritation felt by the patient.

As soft tissue dues not adhere to the implant <NUM>, muscles and soft tissue surrounding the implant <NUM> and bone is encouraged to adhere to the bone in a natural fashion. This minimizes or eliminates muscle wastage and allows the patient to feel the sensory interactions of walking or otherwise that would otherwise be lost.

The flared portion <NUM> is enlarged with respect to the body portion <NUM> so that the flared portion is wider than the body portion <NUM>. This results in the flared portion <NUM> having a larger cross sectional area that the body portion <NUM>.

At least part of the flared portion <NUM> is covered by a physiologically inert substance, to reduce the possibility of infection or an immune reaction at the site at which the implant <NUM> protrudes from the stump of a patient's leg. In the embodiment described herein, the physiologically inert substance is niobium, but it will be understood that other coatings may be used, such as gold, or any other coating known or discovered to be physiologically inert. Such variations are within the purview of a person skilled in the art.

The distal end <NUM> of the implant <NUM> further includes a coupling portion <NUM> which is arranged to receive a coupling part (which will be described in more detail later).

In addition to the flared portion <NUM> having a coating, at least a portion of the body <NUM> may also have a coating (generally denoted by <NUM>), which has the purpose of assisting the implant <NUM> to integrate into the existing skeletal bone (shown as <NUM> in <FIG>).

In one embodiment, the coating is a suitable porous structure which assists in encouraging bone growth into the porous structure, thereby assisting osseointegration of the implant into the existing skeletal bone. In one embodiment, the porous structure is formed from titanium which is deposited on the surface of the body <NUM> by using a plasma deposition process.

The implant has a curved shape which is generally visible at area <NUM>, which is arranged to mimic the curve of a human femoral bone. It will be understood that different types of implants may have different shapes and profiles, as may be required to meet certain physiological constraints. Such variations are within the purview of a person skilled in the art.

The body <NUM> of the implant <NUM> further includes at least one projection <NUM> which extends along a portion of the body <NUM>. The projection is arranged to, in use, prevent rotation of the implant relative to the skeletal bone, by providing 'grip' to prevent rotation of the implant <NUM> when it is located inside the skeletal bone. In the embodiment shown in the Figures, the projection <NUM> is at least one spline which extends longitudinally along the body of the implant. However, it will be understood that other variations which achieve the same functionality may include the provision of raised patterns (a 'zig-zag' pattern), circumferential ridges, or other simple or complex patterns.

The implant <NUM> also has a proximal end <NUM> which is tapered, to allow the patient to also receive an artificial hip implant (or other implant).

In one arrangement, the at least one projection <NUM> is located in the region adjacent the proximal end <NUM>. The porous portion <NUM> for bio adhesion is located adjacent the distal end <NUM>.

Referring now to <FIG> and <FIG> there is shown a first coupling part <NUM> which includes a threaded portion <NUM> arranged to receive a corresponding coupling piece <NUM> which connects to a prosthetic device (not shown).

In a second embodiment described herein, with reference to <FIG>, an implant <NUM> which comprises a body <NUM> having at least one end <NUM>. The body <NUM> is elongate as it is arranged to substantially mimic a portion of a skeletal bone and in the example embodiment described herein, the implant is arranged to mimic at least a portion of a tibia bone of a human patient. This does not suggest that the implant <NUM> is solely suitable for use with a tibia.

Implant <NUM> can be formed through 3D printing or by other means as understood by the skilled addressee and is made of a biocompatible material.

As the implant <NUM> is arranged to mimic a portion of a tibia bone it has a generally triangular cross sectional profile to suite the cross sectional profile of a tibia. The skilled addressee will recognize that variations.

The distal end <NUM> which includes a flared portion <NUM> arranged to, in use, prevent migration of the implant into the bone of a patient. Osseointegrative implants suffer from the issue of the 'end' of the implant, which is necessarily open to the air and passes through the flesh and skin of a patient, being slowly 'pushed upwards' (i.e. upwardly migrating) when the patient wears a prosthetic limb which exerts upward pressure on the implant and therefore can cause the end of the implant to migrate into the bone of the leg of the patient. The embodiment described herein, in contrast, utilises a flared portion <NUM> to spread the upward pressure on the bone and thereby prevent such 'upward migration' of the implant into the leg of the patient.

It will also be understood that the flared portion <NUM> of the implant has a substantially triangular cross-section (i.e. in the embodiment shown, three substantially straight walls, which are connected by rounded corners, as shown in <FIG>). However, it will be noted that the body <NUM> has a substantially round (circular) cross section. That is, the implant <NUM> converges from being substantially triangular at the distal end <NUM> to being substantially round at the body <NUM>.

At least part of the body <NUM> is covered with a rough coating <NUM> which assists in the osseointegration of the body <NUM> into the bone of a patient. In one embodiment, the coating is a suitable porous structure which assists in encouraging bone growth into the porous structure, thereby assisting osseointegration of the implant into the skeletal bone. In one embodiment, the porous structure is formed from titanium which is deposited on the surface of the body <NUM> by using a plasma deposition process.

The flared portion <NUM> is sized and shaped to sit within a recess formed in the exposed end of the bone. As a result of this the flared portion <NUM> has a perimeter that is smaller than that of the skeletal bone it is to be inserted into. The recess is shaped so that the end of the flared portion <NUM> is flush with the end of the bone.

As the flared portion <NUM> is flush with the end of the bone after the implant is inserted, a surgeon can suture the skin to the outside of the bone surrounding the implant. As the flared portion <NUM> does not extend beyond the end of the bone no site is presented for a bacteria colony to develop. This greatly reduces the risk of inflammation, infection and destruction of tissue around the implant site due to bacterial activity.

Also, as the flared portion <NUM> is flush with the end of the bone after the implant is inserted, the soft tissue surrounding the bone does not adhere to the implant. As a result forces transmitted through the implant <NUM>, such as through walking or otherwise, are directly transferred through the implant <NUM> and bone and are not dissipated either through a socket or through soft tissue. This minimizes energy loss.

The distal end <NUM> of the implant <NUM> further includes a coupling portion <NUM> which is arranged to receive a coupling part.

The body <NUM> of the implant <NUM> further includes at least one projection <NUM> adjacent the distal end <NUM> which extends along a portion of the body <NUM>. The projection is arranged to, in use, prevent rotation of the implant relative to the skeletal bone, by providing 'grip' to prevent rotation of the implant <NUM> when it is located inside the skeletal bone. In the embodiment shown in the Figures, the projection <NUM> is at least one spline which extends longitudinally along the body of the implant. However, it will be understood that other variations which achieve the same functionality may include the provision of raised patterns (a 'zig zag' pattern), circumferential ridges, or other simple or complex patterns.

The implant further includes at least one fixing point <NUM> which in the embodiment are described as 'screw holes', which are arranged to provide one or more fixing points to allow the implant to be fixed to a tibia bone through the use of appropriate screws or other fixing devices.

In one arrangement, the body <NUM> includes a central bore <NUM>. Screws can be placed in the fixing point <NUM> through the central bore and then screwed into the surrounding bone when the implant <NUM> is in place.

It will be understood that the fixing point <NUM> may be in the form of a threaded bushing. Where the fixing point <NUM> is a threaded bushing, screws can be partially inserted through the fixing point <NUM> before the implant <NUM> is inserted into the bone. When the implant <NUM> is inserted into the bone the partially inserted screws can be screwed through the central bore fully and engaged with the bone.

In an alternative arrangement, a jig can be placed over the outside of the bone to locate the fixing point <NUM> and screws can be inserted through the fixing point <NUM> from outside the bone.

The implant <NUM> also has a proximal end <NUM> which includes a second attachment point in the form of a second coupling portion <NUM>.

The implant of <FIG> may include one or more fixing points similar to those of fixing point <NUM>.

In a third embodiment described herein, with reference to <FIG>, an implant <NUM> which comprises a body <NUM> having at least one end <NUM>. The body <NUM> is elongate as it is arranged to substantially mimic a portion of a skeletal bone. In the embodiment described herein, the implant <NUM> is designed to be implanted in the leg of a patient, as a partial replacement for the femur bone of a patient. The patient is an amputee who is seeking to use a prosthetic limb and requires the implant to serve as an "attachment" point for the prosthetic limb.

The at least one end <NUM> which includes a stepped portion <NUM> arranged to, in use, prevent migration of the implant into the bone of a patient. Osseointegrative implants suffer from the issue of the 'end' of the implant, which is necessarily open to the air and passes through the flesh and skin of a patient, being slowly 'pushed upwards' (i.e. upwardly migrating) when the patient wears a prosthetic limb which exerts upward pressure on the implant and therefore can cause the end of the implant to migrate into the bone of the leg of the patient. The embodiment described herein, in contrast, utilizes a stepped portion <NUM> to prevent such 'upward migration' of the implant into the leg of the patient.

At least part of the stepped portion <NUM> is covered by a physiologically inert substance, to reduce the possibility of infection or an immune reaction at the site at which the implant <NUM> contacts the flesh of the patient's leg. In the embodiment described herein, the physiologically inert substance is niobium, but it will be understood that other coatings may be used, such as gold, or any other coating known or discovered to be physiologically inert. Such variations are within the purview of a person skilled in the art.

The at least one end <NUM> of the implant <NUM> further includes a coupling portion <NUM> which is arranged to receive a coupling part (which will be described in more detail later).

In addition to the stepped portion <NUM> having a coating, at least a portion of the body <NUM> may also have a coating (generally denoted by <NUM>), which has the purpose of assisting the implant <NUM> to integrate into the skeletal bone (shown as <NUM> in <FIG>).

In one embodiment, the coating is a suitable porous structure which assists in encouraging bone growth into the porous structure, thereby assisting osseointegration of the implant into the skeletal bone. In one embodiment, the porous structure is formed from titanium which is deposited on the surface of the body <NUM> by using a plasma deposition process.

The implant has a curved shape which is generally visible at area <NUM>, which is arranged to mimic the curve of a human femoral bone. It will be understood that different types of implants may have different shapes and profiles, as may be required to meet certain skeletal and anatomical constraints. Such variations are within the purview of a person skilled in the art.

The body <NUM> of the implant <NUM> further includes at least one projection (not shown) which extends along a portion of the body <NUM>. The projection is arranged to, in use, prevent rotation of the implant relative to the skeletal bone, by providing 'grip' to prevent rotation of the implant <NUM> when it is located inside the skeletal bone. In the embodiment shown in the Figures, the projection is at least one spline which extends longitudinally along the body of the implant. However, it will be understood that other variations which achieve the same functionality may include the provision of raised patterns (a 'zig-zag' pattern), circumferential ridges, or other simple or complex patterns.

The implant <NUM> also has a second end <NUM> which is tapered, to allow the patient to also receive an artificial hip implant (or other implant) which can be attached to the leg implant.

Referring now to <FIG> there is shown a coupling part <NUM> which is arranged to cooperate with the implant <NUM>. The coupling part <NUM> includes a locking slot <NUM> arranged to lockingly slot into the implant <NUM>. The coupling part also includes a connector engagement boss <NUM> arranged to connect, either directly or indirectly, with a prosthetic device (not shown), in cooperation with a locking pin channel <NUM>, which is arranged to receive a pin (not shown) to lock the prosthetic (not shown) to the coupling part <NUM>.

Referring now to <FIG>, <FIG> and <FIG> there is shown a fourth embodiment of the present disclosure where the osseointegrative implant <NUM> is attachable to a tibial base plate <NUM>. The tibial base plate <NUM> is used in a knee replacement. The proximal end <NUM> of the osseointegrative implant <NUM> is tapered and includes receiving recess <NUM> arranged to receive a protrusion <NUM> in the tibial base plate <NUM>. When the protrusion <NUM> is received in the receiving recess <NUM> the two can be fixed together at fixing points <NUM> and <NUM> through the use of screws, bolts or other fixing means as would be understood by the skilled addressee. <FIG> is an extension <NUM> to the osseointegrative implant <NUM>.

Although <FIG>, <FIG> and <FIG> have been described with reference to a knee replacement and tibial osseointergrative implant, the skilled addressee will recognize that this would apply to other joint replacements where a base plate is used.

Referring now to <FIG> there is shown a fifth embodiment of the present disclosure where a humeral osseointegrative implant (not shown) is attachable to humeral head replacement <NUM>. The humeral osseointegrative implant includes the features of the osseointegrative implant <NUM> discussed above. The humeral osseointegrative implant includes and extension <NUM> with the exception that the proximal end <NUM> includes a receiving recess <NUM>. The humeral head replacement <NUM> includes a protrusion <NUM> arranged to be inserted into the receiving recess <NUM> of the extension <NUM>. When the protrusion <NUM> is received in the receiving recess <NUM> the two can be fixed together at fixing points <NUM> and <NUM> through the use of screws, bolts or other fixing means as would be understood by the skilled addressee.

Referring now to <FIG> there is shown a sixth embodiment of the present disclosure where a hip replacement <NUM> is arranged to be attachable to the osseointegrative implant <NUM> when used in a femur. The hip replacement <NUM> includes a recess <NUM> arranged to receive the proximal end <NUM> of the osseointegrative implant <NUM>. When the proximal end <NUM> is received in the recess <NUM> the two can be fixed together through the use of screws, bolts or other fixing means as would be understood by the skilled addressee.

<FIG> shows an extension portion <NUM>. <FIG> shows an extension portion <NUM> that includes recess <NUM> to receive extension portion <NUM>.

<FIG> illustrates a seventh embodiment of the present disclosure with an osseointegrative implant <NUM> similar to that of osseointegrative implant <NUM> with fixing points <NUM>. Fixing points <NUM> operate in the same manner as fixing points <NUM>, but are located at the proximal rather than distal end.

<FIG> illustrates an eighth embodiment of the present disclosure with an osseointegrative implant <NUM> similar to that of osseointegrative implant <NUM> with fixing points <NUM>. Fixing points <NUM> operate in the same manner as fixing points <NUM>, but are located at the proximal rather than distal end and receiving portion <NUM> being a profiled recess.

Of course, it will be understood that the osseointegrative implant may be manufactured in different sizes, so that the correct size may be provided for different patients of different heights, weights and builds. This may include manufacturing implants of different lengths and/or implants which have different radial profiles. Such variations are encompassed by the broader inventive concept described and defined herein.

One of the advantages of the embodiments and broader invention described herein is that the invention flared distal end to stop upward migration of the implant into the flesh of the patient.

Moreover, the embodiment described herein provides longitudinal splines which prevent rotation of the implant.

The implant also preferably includes a porous coating, such as a plasma titanium spray, which acts to induce and assist osseointegration.

Lastly, the embodiment is tapered on the proximal end to allow for future hip/neck implants that may be required by the patient.

Throughout this specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", 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.

Those skilled in the art will appreciate that the disclosure described herein is susceptible to variations and modifications other than those specifically described.

Claim 1:
An implant (<NUM>) arranged for integration into a skeletal bone (<NUM>) of a patient, comprising:
a body (<NUM>) and at least one end (<NUM>), the body being arranged to sit within a passageway formed within the bone (<NUM>) and substantially mimic a portion of a skeletal bone;
wherein the at least one end (<NUM>) includes an enlarged portion (<NUM>) arranged to, in use, prevent migration of the implant into the skeletal bone of a patient; wherein the enlarged portion (<NUM>) is stepped outwardly from the body (<NUM>);
characterized in that the enlarged portion (<NUM>) is arranged to sit within a recess formed in an end of the skeletal bone (<NUM>) when implanted, wherein the recess is connected to the passageway and is of a larger diameter than the passageway; and
in that a portion of the at least one end (<NUM>) is coated with a physiologically inert substance.