Patent Description:
The invention is particularly useful in the surgical interventions of knee prosthesis implantation and the following description is made with reference to this specific field of application in order to simplify the exposition thereof.

In general, it is not excluded that the present invention could be applied in other types of surgical interventions of prosthesis implantation in bone extremities.

In the orthopaedic surgery for the implantation of a prosthesis, a bone seat is sometimes subjected to the application of an augment element, typically applied in a housing milled in the bone with a desired profile.

In the context of the present description, with the term "augment element" is meant a prosthesis element capable of filling or taking the place of a bone portion cut or degraded due to pre-existing pathologies or implantations and further capable of being connected to further prosthesis joint elements in order to provide a stable implantation.

The usage of an augment element is particularly common when a spongy part of the bone is not able to support by itself the prosthesis, especially in the case of knee or hip prosthesis.

Typically, an augment element is a substantially cone-shaped or truncated cone-shaped component made of metal.

For example, a knee prosthesis typically comprises a femoral component which is fixed to the distal extremity of a femur, and a tibial component which is fixed to the proximal extremity of a tibia. In that case, both an augment element for the extremity of the femur, and an augment element for the extremity of the tibia can be provided.

The document <CIT>) relates to a multilayered augment element for prosthesis, comprising a body of truncated conical shape with an axial through-cavity open at both ends and an annular section. The body comprises an outer portion of metal trabecular material.

The document <CIT>) relates to an augment element for prosthesis, comprising a hollow sleeve with an internal channel which crosses it. The hollow sleeve comprises one or more bending joints, configured for compressing the channel and reducing the circumference and width of the hollow sleeve. The body is of metal material, without trabecular portions.

The document <CIT>) relates to femoral augments for use with a knee joint prosthesis, including augment components monolithically formed from a single piece of porous metal material, which can be assembled into a large augment assembly. A diaphyseal augment has a generally truncated conical outer surface.

The document <CIT>) relates to anatomically shaped augments having a shape that is configured to generally conform to the shape of a metaphyseal-diaphyseal junction of an intramedullary canal of a bone. The augment includes reliefs configured to reduce a size of the augment and enhance the degree of freedom in the implant positioning and/or sizing of the augment.

A difficulty which emerges in the prior art is that the known augment elements are not able to precisely correspond with the bone anatomy, thus making the performances of the implanted prosthesis unsatisfactory.

In particular, since both tibia and femur have an asymmetric elongated configuration, known augment elements are not able to match the specific tibial or femoral bone anatomy of the patient.

Furthermore, in the prior art, there are problems regarding the insertion or removal of augment elements in the respective bone seat, which involve surgical complexity or difficulty.

A general object of the present invention is to provide to the surgeon an augment element which solves some drawbacks of the prior art.

A further object of the present invention is to allow an augment element to better adapt to the specific bone anatomy.

A further object of the present invention is to provide an augment element particularly suitable for a specific tibial or femoral bone anatomy of a patient.

A further object of the present invention is to give an augment element which is more efficient during insertion or removal in the respective bone seat.

The solution idea underlying the present invention is to provide an augment element for prosthesis configured to be inserted in a bone extremity, having a metal body of a substantially truncated shape with an axial cavity. The metal body has a plurality of annular sections defined along the axial cavity, which are eccentrically stacked so as to define a global inclination of the metal body. The configuration of the metal body allows to better adapt to the specific bone anatomy, in particular for femoral or tibial applications. Additionally, a metal trabecular surface, preferably obtained in one piece and seamlessly with the metal body, can be provided to further improve implantation and attachment on the bone seat.

Based on such solution idea, an augment element for knee prosthesis, is provided according to the features of claim <NUM>.

The augment element comprises a metal body of a substantially truncated conical shape and configured to be inserted in a bone extremity. The body has an outer surface preferably comprising a metal trabecular surface. The metal body is hollow with an axial through-cavity defining a plurality of substantially annular transversal sections. Furthermore, the metal body is inclined in a direction of inclination, so as to define at least one eccentricity between a first transversal section at a first end of the axial through-section and a second transversal section at a second end of the axial through-cavity.

Thereby, an augment element particularly suitable for a specific asymmetric bone anatomy is provided, with particular advantage in case of application of the augment element to a tibial or femoral bone extremity.

It is also provided that the augment element for prosthesis has a metal body of a substantially truncated conical shape, with an axial through-cavity and comprising a metal trabecular surface.

The augment element further comprises a plurality of through-slits, open from a first end of the metal body up to an intermediate portion; such slits are configured for a radial compression of the metal body, thus locally reducing a circumference of the substantially annular transversal section of the metal body.

Thereby, an augment element is advantageously provided which is more efficient during the insertion and implantation, allowing a radial compression of the metal body which increases the press-fit toward the bone; together with the increasing of the press-fit towards the bone, also the pressure of the trabecular surface against the bone increases, thus stimulating the bone growth in order to ensure a stable and long-term connection.

The augment element according to the present invention advantageously improves both the primary stability and the secondary stability of the implantation. The primary stability is the one which is immediately observable in the intervention, it is practically a mechanic wedging. The secondary stability is instead obtained due to the osseointegration, which is improved by the presence of primary stability, by the presence of a trabecular structure or with adequate porosity and by the presence of a compression force or press-fit which stimulates the bone growth.

Furthermore, specific features of the augment element are provided which make it particularly efficient in case of applications to tibial or femoral extremities, which will be illustrated in detail in the following.

Further features and advantages of the invention will become apparent from the detailed description which follows, provided for illustrative and non-limiting purposes, and from the claims which form an integral part of the present description.

In different figures, analogous elements will be indicated by analogous reference numbers.

The technical drawings presented in the figures are to be understood as purely illustrative, not necessarily made to scale or having the same scale among each other.

<FIG> shows a prospective view of a first embodiment of augment element <NUM> for prosthesis according to the present invention. The augment element <NUM> of this example is an element for femoral application, in combination with a knee prosthesis.

The augment element <NUM> comprises a metal body <NUM> of a substantially truncated conical shape, which is configured to be inserted in a femoral extremity. Preferably, the metal body <NUM> is made of titanium or alloys thereof, for biomedical applications.

In general, the metal body comprises walls, which will be further described, having a substantially constant thickness.

The metal body <NUM> has an outer surface comprising a metal trabecular surface <NUM>; preferably the metal trabecular surface <NUM> is obtained in one piece seamlessly with the metal body <NUM> by a co-manufacture procedure, for example by EBM (Electron Beam Machining) technologies. A co-manufacture procedure in fact allows to provide an interface-free metal trabecular surface, so as to avoid the risk of detachments of the trabecular part of the metal body.

The metal body <NUM> preferably comprises a smooth edge <NUM> on the outer surface surrounding the metal trabecular surface <NUM> on one or more sides, preferably on all sides.

The metal body <NUM> is hollow with an axial through-cavity <NUM> defining a plurality of substantially annular transversal sections, whose configuration will be further described.

<FIG> shows a frontal view of the augment element <NUM> for prosthesis, wherein the two symmetric lateral walls of the same are shown, having a same inclination.

<FIG> shows a lateral sectional view of the augment element <NUM> for prosthesis, with respect to section III-III of <FIG>.

The metal body <NUM> is inclined in a direction of inclination, in this case towards the right of the figure, so as to define an eccentricity between a first transversal section at a first end <NUM> of the axial through-cavity <NUM> and a second transversal section at a second end <NUM> of the axial through-cavity <NUM>.

In particular, the axial cavity <NUM> has a longitudinal axis <NUM> inclined in the direction of inclination with respect to the vertical axis of the metal body <NUM>. The vertical axis, not shown in the figure for the sake of simplicity, is perpendicular to one of the first or second transversal section, at the respective end <NUM> or <NUM>.

The metal body <NUM> comprises a frontal wall <NUM> extended towards the direction of inclination, and a rear wall <NUM> opposite the frontal wall <NUM> and extended away from the direction of inclination.

The frontal wall <NUM> has an inclination with respect to the vertical axis that is less than an inclination of the rear wall <NUM>.

In other words, the profile of the metal body <NUM> is tapered towards the first end <NUM>, with a frontal asymmetry visible in lateral section.

<FIG> shows a lateral view of the augment element <NUM> for prosthesis, wherein some features already discussed in relation to <FIG> are pointed out.

<FIG> shows a frontal sectional view of the augment element <NUM> for prosthesis, with respect to section V-V of <FIG>.

In this embodiment, it is appreciated how the longitudinal axis <NUM> of the cavity <NUM> is instead not inclined with respect to a vertical axis of the metal body <NUM>, considering the direction transversal to the direction of inclination shown in <FIG>.

The augment element <NUM> further comprises a plurality of through-slits <NUM> in the metal body <NUM>, which are open from the first end <NUM> up to an intermediate portion on the metal body <NUM>.

These slits <NUM> are configured for a radial compression of the metal body <NUM>, in particular facilitating the insertion in a femoral cavity, locally reducing a circumference of the substantially annular transversal sections which make up the metal body <NUM> during insertion of the augment element <NUM>, and increasing a press-fit towards a bone portion.

In particular, for femoral applications, the first transversal section at the end <NUM> is smaller in size with respect to the second transversal section at the end <NUM>, so as to facilitate an insertion of the metal body <NUM> into the femoral bone extremity.

Preferably, each of the slits <NUM> is open towards the first end <NUM> and ends in a respective enlarged circular hole <NUM> beside to the intermediate portion of the metal body <NUM>. Thereby, the enlarged circular hole <NUM> is configured to improve a localized mechanical resistance of the metal body.

<FIG> shows a bottom view of the augment element <NUM> for prosthesis. In this view it is possible to appreciate the eccentricity <NUM> resulting between the first transversal (in this case, circular) section at the first end <NUM>, and the second transversal (in this case, circular) section at the second end <NUM> of the axial through-cavity <NUM>.

<FIG> shows a frontal view of the augment element <NUM> for prosthesis with geometrical indications relating to the metal body <NUM>.

In particular, the conicity <NUM> of the symmetric lateral walls is overall comprised between <NUM>° and <NUM>°, more preferably equal to <NUM>°.

<FIG> shows a lateral view of the augment element <NUM> for prosthesis with geometrical indications relating to the metal body <NUM>.

In the example of the augment element <NUM>, the frontal wall <NUM> is vertical that is with inclination of <NUM>° with respect to the vertical. In general, an inclination of the frontal wall <NUM> with respect to the vertical axis can be comprised between <NUM>° and <NUM>°, more preferably comprised between <NUM>° and <NUM>°.

In the example of the augment element <NUM>, the rear wall <NUM> has an inclination <NUM> of <NUM>° with respect to the vertical. In general, an inclination of the rear wall <NUM> with respect to the vertical axis is comprised between <NUM>° and <NUM>°.

<FIG> shows a prospective view of a second embodiment of augment element <NUM> for prosthesis according to the present invention. The augment element <NUM> of this example is an element for femoral application, in combination with a knee prosthesis.

The augment element <NUM> comprises a metal body <NUM> of a substantially truncated conical form, which is configured to be inserted in a femoral extremity. Preferably, the metal body <NUM> is made of titanium or alloys thereof, for biomedical applications.

The metal body <NUM> has an outer surface comprising a metal trabecular surface <NUM>; preferably the metal trabecular surface <NUM> is directly applied to the metal body <NUM> by a co-manufacture procedure in one piece and seamlessly, for example by EBM (Electron Beam Machining) technologies.

<FIG> shows a frontal view of the augment element <NUM> for prosthesis, wherein it is evident a pair of bicondylar supports 220a and 220b, arranged sideways in the metal body <NUM>.

The bicondylar supports 220a and 220b protrude from a terminal transversal section of the body <NUM>, and each comprises a tapered body, which widens away from the metal body <NUM>.

Preferably, also the bicondylar supports 220a and 220b have an outer surface comprising a metal trabecular surface, made in one piece and seamlessly with the bicondylar supports 220a and 220b.

In the augment element <NUM>, the bicondylar supports 220a and 220b perform a support function also for the femoral condyles, in case that the bone defect will be extended also to the latter. The choice between the embodiment <NUM> without bicondylar supports or <NUM> comprising the bicondylar supports of the augment element, may depend for example on the location and extension of the bone defect. For example, in case of a removal of an implantation with stem, there is often the generation of a femoral bone defect along the channel, for which it would be preferred to use an augment element <NUM> according to the first embodiment; differently, in case of advanced bone degeneration, a situation may arise where the femoral condyle will not offer sufficient support for a prosthesis, and it would be preferred to use an augment element <NUM> according to the second embodiment, in order to obtain a greater reinforcement of the area.

Preferably, the metal body comprises a smooth edge <NUM> on the outer surface, which surrounds at least partially the metal trabecular surface <NUM> and preferably also the metal trabecular surface of the bicondylar supports 220a and 220b.

<FIG> shows a lateral sectional view of the augment element <NUM> for prosthesis, with respect to section XI-XI of <FIG>.

The metal body <NUM> is inclined in a direction of inclination, in this case towards the right of figure, so as to define an eccentricity between a first transversal section at a first end <NUM> of the axial through-cavity <NUM> and a second transversal section at a second end <NUM> of the axial through-cavity <NUM>.

In particular, the axial cavity <NUM> has a longitudinal axis <NUM> inclined in the direction of inclination with respect to a vertical axis of the metal body <NUM>. The vertical axis, not shown in the figure for sake of simplicity, is perpendicular to one of the first or second transversal section, at the respective end <NUM> or <NUM>.

In fact, an eccentricity between the first transversal section at the first end <NUM>, and the second transversal section at the second end <NUM> of the axial through-cavity <NUM> can be guessed.

<FIG> shows a frontal sectional view of the augment element <NUM> for prosthesis, with respect to section XIII-XIII of <FIG>.

Preferably, each of the slits <NUM> is open towards the first end <NUM> and ends in a respective enlarged circular hole <NUM> beside to the intermediate portion of the metal body <NUM>. Thereby, the enlarged circular body <NUM> is configured to improve a localized mechanical resistance of the metal body.

In the augment element <NUM> for femoral applications, the first transversal section at the end <NUM> is smaller in size with respect to the second transversal section at the end <NUM>, and the pair of bicondylar supports 220a e 220b arranged sideways protrude precisely from the second transversal section, thus being in distal position once the augment element is implanted in the respective femoral bone cavity.

In particular, the conicity <NUM> of the lateral walls is overall comprised between <NUM>° and <NUM>°, more preferably equal to <NUM>° as in the example of the augment element <NUM>.

As visible, the second transversal section at the end <NUM> is furthermore inclined in a second direction of inclination, in a plane transversal to the direction of inclination of the longitudinal axis <NUM>. In that sense, the metal body <NUM> has a plane of inclination of the end <NUM> which is different with respect to the plane of inclination of the end <NUM>, generating an overall asymmetry of the augment element <NUM>, not only in the already-considered direction of frontal inclination, but also in a direction of transversal inclination of the whole metal body <NUM>, visible in <FIG>.

Furthermore, the pair of bicondylar supports 220a and 220b extends from the second end <NUM> by a same height <NUM>, thus defining an asymmetric pair of bicondylar supports 220a and 220b.

In the light of the overall asymmetry of the augment element <NUM>, it is clear that different solutions for a left or right femur must be provided.

<FIG> shows a prospective view of a third example of augment element <NUM> for prosthesis according to the present invention. The augment element <NUM> of this example is an element for tibial application, in combination with a knee prosthesis.

The augment element <NUM> comprises a metal body <NUM> of a substantially truncated conical shape, which is configured to be inserted in a tibial extremity. Preferably, the metal body <NUM> is made of titanium or alloys thereof, for biomedical applications.

In a natural analogy, the metal body <NUM> is similar to a flower corolla shape from which two opposed petals were removed.

<FIG> shows a frontal view of the augment element <NUM> for prosthesis, wherein the two symmetric lateral walls of the same are shown, having a same inclination and configuration.

<FIG> shows a lateral sectional view of the augment element <NUM> for prosthesis, with respect to section XVIII-XVIII of <FIG>.

In particular, the axial cavity <NUM> has a longitudinal axis <NUM> inclined in the direction of inclination with respect to a vertical axis of the metal body <NUM>. The vertical axis, not shown in the figure for the sake of simplicity, is perpendicular to one of the first or second transversal section, at the respective end <NUM> or <NUM>.

In other words, the profile of the metal body <NUM> is tapered towards the second end <NUM>, with a frontal asymmetry visible in lateral section.

For tibial applications, it can be seen that the first transversal section at the end <NUM> is larger in size with respect to the second transversal section at the end <NUM>, so as to facilitate an insertion of said metal body into the tibial bone extremity.

The augment element <NUM> further comprises a pair of cut-outs <NUM> arranged sideways in the metal body <NUM>, and open from the first end <NUM> up to an intermediate portion on the metal body <NUM>.

<FIG> shows a frontal sectional view of the augment element <NUM> for prosthesis, with respect to section XX-XX of <FIG>.

Preferably, the metal body <NUM> comprises lateral walls <NUM> at the cut-outs <NUM>; such lateral walls <NUM> have respective curved and concave shapes with respect to the outside of the metal body <NUM>, to replicate a medial/side and rear bone anatomy.

In particular, an overall conicity <NUM> of the symmetric lateral walls <NUM>, measured with respect to imaginary straight lines passing through the two edges of the metal body <NUM>, respectively at the first end <NUM> and the second end <NUM>, is overall comprised between <NUM>° and <NUM>°, more preferably equal to <NUM>°.

In the example of the augment element <NUM>, the frontal wall <NUM> is near the vertical, with an inclination <NUM> equal to <NUM>° with respect to the vertical. In general, an inclination of the frontal wall <NUM> with respect to the vertical axis can be comprised between <NUM>° and <NUM>°, more preferably comprised between <NUM>° and <NUM>°.

In the example of the augment element <NUM>, the rear wall <NUM> has an inclination of <NUM>° with respect to the vertical. In general, an inclination of the rear wall <NUM> with respect to the vertical axis is comprised between <NUM>° and <NUM>°.

Preferably, the rear wall <NUM> further has a curved and concave shape with respect to the outside of the metal body <NUM>, to replicate a tibial bone rear anatomy.

<FIG> shows a top view of the augment element <NUM> for prosthesis.

In this view, it is possible to appreciate the eccentricity <NUM> resulting between the first transversal section (in this case, circular) at the first end <NUM> and the second transversal section (in this case, circular) at the second end <NUM> of the axial through-cavity <NUM>.

<FIG> shows a prospective view of a fourth embodiment of augment element <NUM> for prosthesis according to the present invention. The augment element <NUM> of this example is an element for tibial application, in combination with a knee prosthesis.

The metal body <NUM> has an outer surface comprising a metal trabecular surface <NUM>; preferably the metal trabecular surface <NUM> is directly applied to the metal body <NUM> by a co-manufacture procedure, made in one piece and seamlessly, for example by EBM (Electron Beam Machining) technologies.

<FIG> shows a frontal view of the augment element <NUM> for prosthesis, wherein the two symmetric lateral walls <NUM> of the same are shown, having a same inclination and configuration.

<FIG> shows a lateral sectional view of the augment element <NUM> for prosthesis, with respect to section XVI-XVI of <FIG>.

The metal body <NUM> is inclined in a direction of inclination, in this case towards the right of the figure, so as to define at least one eccentricity between a first transversal section at a first end <NUM> of the axial through-cavity <NUM> and a second transversal section at a second end <NUM> of the axial through-cavity <NUM>.

The metal body <NUM> comprises a frontal wall <NUM> extended towards the direction of inclination and a rear wall <NUM> opposite the frontal wall <NUM> and extended away from the direction of inclination.

<FIG> shows a frontal sectional view of the augment element <NUM> for prosthesis, with respect to section XXVIII-XXVIII of <FIG>.

<FIG> shows a top view of the augment element <NUM> for prosthesis, wherein it is appreciated that the first transversal section at the end <NUM> is bilobed annular, such that the outer surface of the metal body <NUM> is tapered between the first transversal section and the second transversal section, as better visible in <FIG>.

In this view, it is also possible to appreciate the double eccentricity <NUM> resulting between the first transversal section (in this case, bilobed therefore having two circumference centres which describe it) at the first end <NUM>, and the second transversal section (in this case, circular with only one circumference centre) at the second end <NUM> of the axial through-cavity <NUM>.

<FIG> shows a frontal view of the augment element <NUM> for prosthesis for prosthesis with geometrical indications relating to the metal body <NUM>.

In particular, an overall concavity <NUM> of the lateral symmetric walls <NUM> is overall comprised between <NUM>° and <NUM>°, more preferably equal to <NUM>°.

<FIG> show respective prospective views of a variation of the augment element <NUM>' for prosthesis.

In this variation, the augment element <NUM>' comprises a plurality of through-slits <NUM> in the metal body, open from the first end up to a intermediate portion on the metal body, which are configured for a radial compression of the metal body, locally reducing a circumference during insertion of the augment element <NUM>', and increasing a press-fit towards a bone portion. Preferably, each of the slits <NUM> ends in a respective enlarged circular hole <NUM>.

<FIG> shows an example of application of the augment element <NUM> for prosthesis to a femoral extremity.

<FIG> shows an example of application of the augment element <NUM> for prosthesis to a tibial extremity.

It is clear that further implementations and modifications of the present invention will be possible for the person skilled in the art, in order to meet contingent needs.

In particular, specific features described with reference to an embodiment could be also applied to other embodiments described herein in a variation thereof, if there is no technical prejudice in this regard.

Claim 1:
Augment element (<NUM>, <NUM>, <NUM>) for knee prosthesis, comprising a metal body (<NUM>, <NUM>, <NUM>) of a substantially truncated conical shape configured to be inserted into a bone extremity and having an outer surface comprising a metal trabecular surface (<NUM>, <NUM>, <NUM>),
said metal body (<NUM>, <NUM>, <NUM>) being hollow with an axial through-cavity (<NUM>, <NUM>, <NUM>) defining a plurality of substantially annular transversal sections,
wherein said metal body (<NUM>, <NUM>, <NUM>) is inclined in a direction of inclination, so as to define at least one eccentricity (<NUM>, <NUM>) between a first transversal section at a first end (<NUM>, <NUM>, <NUM>) of said axial through-cavity (<NUM>, <NUM>, <NUM>) and a second transversal section at a second end (<NUM>, <NUM>, <NUM>) of said axial through-cavity (<NUM>, <NUM>, <NUM>),
characterized by further comprising a plurality of through-slits (<NUM>, <NUM>, <NUM>) in said metal body (<NUM>, <NUM>, <NUM>), open from said first end (<NUM>, <NUM>, <NUM>) up to an intermediate portion on said metal body (<NUM>, <NUM>, <NUM>), wherein said plurality of through-slits (<NUM>, <NUM>, <NUM>) is configured for a radial compression of said metal body (<NUM>, <NUM>, <NUM>), locally reducing a circumference of said substantially annular transversal sections during insertion of said augment element (<NUM>, <NUM>, <NUM>), and increasing a press-fit towards a bone portion.