Patent Description:
In particular, the milling device is particularly suitable to make seatings for bone void fillers for a knee prosthesis, or to prepare a bone seating for a shoulder joint prosthesis, also called a humeral prosthesis, or for a hip prosthesis.

It is known that in orthopedic surgery to implant a prosthesis, when the preparation of a seating for a bone void filler or the preparation of a housing seating for a prosthesis is required, it is necessary to make a hole in the bone and/or a milling in order to make the seating with the desired profile.

Often, in fact, congenital or traumatic degenerative pathologies, for example primary arthrosis, secondary arthrosis due to a trauma or caused by infections, rheumatoid arthritis, inflammatory arthritis, osteonecrosis, or bone tumors, or other similar problems, require the implantation of a prosthesis able to reproduce, overall, a movement that is analogous to that of the healthy joint.

It is also known that when, due to the pathologies as above, the cancellous bone cannot support the prosthesis, it is necessary to make suitable bone seatings for the implantation of a bone or metal void filler that acts as a support for the prosthesis. This problem can become critical especially for knee prostheses and for hip and shoulder prostheses.

The knee prosthesis typically comprises a femoral component, which is attached to the distal end of the femur, and a tibial component, which is attached to the proximal end of the tibia.

Especially if it is necessary to perform a revision of a previously implanted knee prosthesis, making a bone seating to apply suitable support cones first requires making a hole with one or more reamer devices with increasing diameter, and subsequently shaping it with a suitable milling device.

For this purpose, the milling devices which can be used during prosthetic surgery to prepare the seatings as above are known.

These milling devices typically comprise a handler body provided with a shaft which develops along a longitudinal axis, substantially coinciding with the axis of the intra medullary canal, depending on the case, of the tibia or femur, and provided with a proximal end which has an attachment to a drive member and a distal end connected to a milling tool, rotated by the drive member.

Since both tibia and femur have an asymmetrical elongated conformation, one of the main problems encountered during the preparation of a bone seating is avoiding perforation of the cortical zone of the tibial and femoral bone.

One of the disadvantages of known milling devices is that they are configured to shape the bone seating in the direction of a milling axis which substantially coincides with the axis of the intra medullary canal, depending on the case, of the tibia or femur, therefore being unable to follow the anatomy of the tibial and femoral bone.

Sometimes, in order to avoid perforation of the cortical zone, the surgeon is therefore forced to make bone seatings with a limited size which, however, may not be sufficient to guarantee an adequate joint stability of the prosthesis, especially in the event previous implants of prostheses have damaged, or in any case rendered unusable, an extended zone of the cancellous bone.

Surgical tools for drilling or milling are known, for example from documents <CIT>, <CIT>, <CIT> and <CIT>, in which, however, the longitudinal reference axis defined by the guide element, in the cases where it is provided, is coaxial to the milling axis, with the disadvantages mentioned above.

There is therefore the need to perfect a milling device for prosthetic surgery that can overcome at least one of the disadvantages of the state of the art.

In particular, one purpose of the present invention is to provide a milling device for prosthetic surgery that is able to perform a milling avoiding damage to the cortical zone of the bone.

Another purpose of the present invention is to provide a milling device for prosthetic surgery which is able to produce a stable milling with respect to a milling axis that is different from the axis of the intra medullary canal, that is, different from the axis of the guided shaft which is inserted inside it.

Another purpose of the present invention is to provide a milling device for prosthetic surgery which is simple to use, and which consists of a limited number of components.

Another purpose of the present invention is to provide a milling device for prosthetic surgery that is simple to assemble, to perform the surgical operation, and disassemble, to carry out its cleaning and sterilization.

In accordance with the above purposes, the milling device for prosthetic surgery comprises a milling tool and a handler body that has a rotating drive shaft which develops along a longitudinal axis. The rotating shaft is connected to the milling tool to rotate the milling tool around the longitudinal axis.

In accordance with one aspect of the present invention, the rotating shaft comprises an angular joint rotatably coupled with the milling tool to selectively define a plurality of inclined positions of the milling tool with respect to the longitudinal axis.

In accordance with another aspect of the present invention, the handler body comprises a guide member which comprises a stabilizer body disposed eccentric with respect to the longitudinal axis, configured to cooperate with the milling tool so as to selectively define, amongst the plurality of inclined positions as above, a single specific stable inclined position of the milling tool with respect to the longitudinal axis.

These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given as a non-limiting example with reference to the attached drawings wherein:.

We will now refer in detail to the various embodiments of the invention, of which one or more examples are shown in the attached drawings. Each example is supplied by way of illustration of the invention and shall not be understood as a limitation thereof. For example, the characteristics shown or described insomuch as they are part of one embodiment can be adopted on, or in association with, other embodiments to produce another embodiment. It is understood that the present invention shall include all such modifications and variants.

Before describing the embodiments, we must also clarify that the present description is not limited in its application to details of the construction and disposition of the components as described in the following description using the attached drawings.

Embodiments described using the attached drawings concern a milling device for prosthetic surgery, indicated as a whole with reference number <NUM> in the attached drawings.

With particular reference to the attached drawings, <FIG> concern a milling device <NUM> suitable to make seatings for bone void fillers for the tibial bone, <FIG> concern a milling device <NUM> suitable to make seatings for bone void fillers for the femoral bone, and <FIG> concern a milling device <NUM> suitable to making seatings for a shoulder joint prosthesis, also called a humeral prosthesis.

The milling device for prosthetic surgery <NUM>, hereafter device <NUM>, comprises a milling tool <NUM> and a handler body <NUM> with a rotating drive shaft <NUM> which develops along a longitudinal axis Z, connected to the milling tool <NUM> to rotate the milling tool <NUM> around the longitudinal axis Z.

In accordance with one aspect of the present invention, the rotating shaft <NUM> comprises an angular joint <NUM> rotatably coupled with the milling tool <NUM> to selectively define a plurality of inclined positions of the milling tool <NUM> with respect to the longitudinal axis Z.

In accordance with another aspect of the present invention, the handler body <NUM> comprises a guide member <NUM> which comprises a stabilizer body <NUM> disposed eccentric with respect to the longitudinal axis Z, configured to cooperate with the milling tool <NUM> so as to selectively define, amongst the plurality of inclined positions, a single specific stable inclined position of the milling tool <NUM> with respect to the longitudinal axis Z.

The specific stable inclined position allows the milling tool <NUM> to rotate with respect to a milling axis R inclined with respect to the longitudinal axis Z of rotation of the rotating shaft <NUM>, by an angle of inclination α variable according to the surgical application (application to the tibial bone, to the femoral bone or to the shoulder joint). So it can be said that the milling tool <NUM> is inclined with respect to the rotating shaft <NUM> and to the handler body <NUM>.

In particular, the guide member <NUM> defines the angle of inclination α so that when the shaft <NUM> rotates with respect to the longitudinal axis Z, the milling tool rotates with respect to the milling axis R.

As shown schematically in <FIG>, with this configuration of the device <NUM>, it is possible to make a bone seating without damaging the cortical zone <NUM> of the bone. In fact, while overall the device <NUM> is used so that the longitudinal axis Z is substantially orthogonal to the tibial resection, that is, substantially parallel to the intra medullary canal, the device <NUM> shapes the bone seating with respect to the angle of inclination α which corresponds to the specific stable inclined position. Possibly, the milling tool <NUM> can have the profile of a rotating body obtained by the rotation of a desired curve, for example one that approximates the internal geometry of the tibia or femur. In particular, a known milling device is shown schematically with a dashed line, the device <NUM> in accordance with embodiments described herein is shown with a continuous line. Evidently, the known milling device moves much closer to the cortical zone <NUM> with the risk of damaging it.

In addition, this allows the user to make a deeper bone seating, being able to guarantee, especially in case of serious degeneration of the cancellous bone, a suitable joint stability of the prosthesis.

The milling tool <NUM> has a concave coupling seating <NUM> with a coupling polar aperture <NUM>.

The shaft <NUM> is provided with a distal end <NUM> connected to the milling tool <NUM> inside the concave coupling seating <NUM>, and a proximal end <NUM> which has an attachment <NUM> to a drive member to rotate the milling tool <NUM> around the longitudinal axis Z.

Here and in the following description, the relative terms "proximal" and "distal", when describing the shaft <NUM> of the milling device <NUM>, are defined with reference to the perspective of the milling device <NUM>. Therefore "proximal" refers to the direction of coupling with the attachment <NUM> and "distal" refers to the direction of coupling with the milling tool <NUM>.

In particular, the angular joint <NUM> is positioned on the distal end <NUM> of the shaft <NUM>, and is rotatably coupled with the coupling polar aperture <NUM> with degrees of freedom able to allow the milling tool <NUM> to selectively adopt a plurality of inclined positions with respect to the longitudinal axis Z.

According to embodiments, the handler body <NUM> comprises a tubular handle <NUM> coaxially coupled in a removable manner with the shaft <NUM> and provided with the guide member <NUM>.

The tubular handle <NUM> is provided with a distal aperture <NUM> and a proximal aperture <NUM> respectively associated with the distal end <NUM> and the proximal end <NUM> of the shaft <NUM>.

The tubular handle <NUM> has a through longitudinal channel <NUM> from the distal aperture <NUM> to the proximal aperture <NUM> for the rotational coupling with the shaft <NUM>. Advantageously, the longitudinal channel <NUM> has a size in the direction orthogonal to the longitudinal axis Z greater than that of the shaft <NUM>, this allows to prevent unwanted sliding.

In accordance with possible solutions, the tubular handle <NUM> can be made in one piece or it can be made in two separate shell-like parts selectively combinable to accommodate the shaft <NUM>. Advantageously, the tubular handle <NUM> can be made of plastic material to reduce to a minimum the possible frictions with the shaft <NUM> and with the milling tool <NUM>.

In accordance with embodiments described herein, with particular reference to <FIG> and <FIG> and <FIG>, the size of the proximal aperture <NUM> is slightly smaller than the size of the longitudinal channel <NUM> to cooperate with a circumferential retaining edge <NUM> of the shaft <NUM>, and guarantee a desired positioning of the shaft <NUM> in the direction of the longitudinal axis Z.

Advantageously, the tubular handle <NUM> can have, externally, an ergonomic and non-slip grip <NUM> so that the user is aided in gripping and handling it. For this purpose, the tubular handle <NUM> has longitudinal grooves <NUM> which extend at least in a central zone thereof, possibly having knurled surfaces. In addition, the grip <NUM> can have a rounded shape in order to further improve its hold.

In accordance with embodiments described herein, the shaft <NUM> is cannulated, that is, it is internally hollow and has a guide channel <NUM> parallel to the longitudinal axis Z and suitable to accommodate a guide element necessary to axially position the device <NUM> in the desired milling position during surgery.

At least in the case of a milling device <NUM> for femoral and/or tibial bone, the guide element can generally be a reamer device which is used before the device <NUM> to create a first hole, or first holes of increasing diameters. Once the suitable diameter of the hole has been reached, the device <NUM> is prepared so that the guide element is inserted in the guide channel <NUM> and therefore acts as an axial guide for the milling operation.

The guide member <NUM>, and in particular the stabilizer body <NUM>, is configured to cooperate with the concave coupling seating <NUM>.

According to embodiments, the stabilizer body <NUM> is configured to make a same-shape coupling with the concave coupling seating <NUM> of the milling tool <NUM>, so as to define the specific stable inclined position of the milling tool <NUM> with respect to the longitudinal axis Z based on the eccentricity with respect to the longitudinal axis Z.

The guide member <NUM> comprises the distal aperture <NUM> and a sliding coupling seating <NUM> configured to accommodate a shaped portion <NUM> of the shaft <NUM>, to guarantee a desired positioning of the shaft <NUM> in the direction of the longitudinal axis Z. In particular, the seating <NUM> is concentric with respect to the longitudinal axis Z.

The seating <NUM> is configured to perform a positioning action of the shaft <NUM> in cooperation with the positioning action performed by the circumferential retaining edge <NUM>. In this way, once the shaft <NUM> is operatively inserted in the longitudinal channel <NUM>, its positioning in the direction of the longitudinal axis Z is substantially determined. In particular, the shaped portion <NUM> is in a rotational coupling with the seating <NUM>. This coupling presupposes that there is a minimum space between the surfaces of the seating <NUM> and the surfaces of the shaped portion <NUM> to allow a functional movement.

According to embodiments, for example shown in <FIG> and in <FIG>, the shaped portion <NUM> has a substantially cylindrical shape. The stabilizer body <NUM> has an external surface <NUM> in sliding coupling with an internal surface <NUM> of the concave coupling seating <NUM> of the milling tool <NUM>. The external surface <NUM> is defined by a cylindrical portion and is inclined with respect to the longitudinal axis Z by an angle of inclination α which substantially defines the angulation of the milling axis R with respect to the longitudinal axis Z. The internal surface <NUM> of the concave coupling seating <NUM> has an advantageously cylindrical profile with a diameter slightly larger than the diameter of the cylindrical portion that defines the external surface <NUM>, to ensure the sliding coupling as above. The sliding coupling guarantees the single specific stable inclined position of the milling tool <NUM> with respect to the longitudinal axis Z.

The stabilizer body <NUM> also has a base surface <NUM> provided with the distal aperture <NUM>, which allows access to the seating <NUM>. The surface of the seating <NUM> and the external surface <NUM> are connected to the base surface <NUM>, the first externally, the second internally with respect to the distal aperture <NUM>. In particular, since the stabilizer body is disposed eccentric with respect to the longitudinal axis Z, the distal aperture <NUM> is not centered with respect to the base surface <NUM>, but is concentric with the longitudinal axis Z.

As schematically shown in <FIG>, the base surface <NUM> is overall eccentric with respect to the longitudinal axis Z and is defined by a first concentric portion 34a, delimited solely for illustrative purposes with a dotted line, with respect to the longitudinal axis Z, and by a second portion 34b eccentric with respect to the longitudinal axis Z, the portions 34a, 34b being essentially one the continuation of the other. The larger the second portion 34b, and therefore the greater the eccentricity of the base surface <NUM>, the greater the angle of inclination of the milling tool <NUM> with respect to the longitudinal axis Z in the stable inclined position.

The base surface <NUM> is inclined with respect to the longitudinal axis Z by an angle of inclination α which corresponds to the angle of inclination α of the single specific stable inclined position of the milling tool <NUM> with respect to the longitudinal axis Z. In the case of a milling device <NUM> for the preparation of a bone seating for a prosthesis of the knee joint, the angle of inclination α is about <NUM>° for the milling device <NUM> for the tibial bone, and about <NUM>° for the milling device <NUM> for the femoral bone.

According to embodiments, shown in <FIG>, the shaped portion <NUM> has a substantially conical shape. Furthermore, the milling tool <NUM> is provided with a connection crown <NUM> in sliding coupling with an inclined seating <NUM> by an angle of inclination α which corresponds to the angle of inclination α of the single specific stable inclined position of the milling tool <NUM> with respect to the longitudinal axis Z. The sliding coupling guarantees the single specific stable inclined position of the milling tool <NUM> with respect to the longitudinal axis Z. In the case of a milling device <NUM> for the preparation of a bone seating for a prosthesis of a shoulder joint the angle of inclination α is approximately <NUM>°.

According to embodiments, anti-rotation constraining elements <NUM> are present on the distal end <NUM> of the shaft <NUM> and are operatively coupled with coupling seatings <NUM> provided in the concave coupling seating <NUM> of the milling tool <NUM>. The anti-rotation constraining elements <NUM> are configured to angularly constrain the milling tool <NUM> with respect to the handler body <NUM> so that they are able to rotate integrally around the longitudinal axis Z.

The anti-rotation constraining elements <NUM> comprise rigid transmission tabs <NUM> with a shape mating with corresponding coupling seatings <NUM> present on the milling tool <NUM>, to transmit the rotational motion to the milling tool <NUM>.

The anti-rotation constraining elements <NUM> protrude radially from the profile of the shaft <NUM>, advantageously in a diametrically opposite position with respect to each other if more than one is present. Advantageously, in fact, there are two anti-rotation constraining elements <NUM> to guarantee a better transmission of the rotation torque from the shaft <NUM> to the milling tool <NUM>. This diametrically opposite disposition of the two anti-rotation constraining elements <NUM> allows the milling tool to horizontally pivot on a plane orthogonal to the one passing through the anti-rotation constraining elements <NUM> so as to selectively adopt a plurality of positions inclined with respect to the longitudinal axis Z, and in particular to adopt a single specific stable inclined position defined by the same-shape coupling of the stabilizer body <NUM> with the concave coupling seating <NUM> of the milling tool.

The anti-rotation constraining elements <NUM> are removably keyed into the coupling seatings <NUM>, made in correspondence with the polar coupling aperture <NUM> of the milling tool <NUM>.

The coupling seatings <NUM> are substantially radial with respect to the longitudinal axis Z and are configured to guarantee the constraint necessary to transmit the rotation torque from the shaft <NUM> to the milling tool <NUM>.

Advantageously, the coupling seatings <NUM> are in a number coherent with the number of anti-rotation constraining elements <NUM>. This guarantees a univocal and determinate connection of the milling tool <NUM> on the shaft <NUM>, preventing possible assembly errors.

According to embodiments, the angular joint <NUM> has one or more convex curved portions <NUM> disposed around the longitudinal axis Z.

Advantageously, the angular joint <NUM> has at least two convex curved portions <NUM> disposed diametrically opposite with respect to the longitudinal axis Z.

In accordance with the embodiments described herein, the anti-rotation constraining elements <NUM> are disposed around the longitudinal axis Z alternating with the convex curved portions <NUM>.

The convex curved portions <NUM> protrude radially from the profile of the shaft <NUM> in a position diametrically opposite with respect to that of the anti-rotation constraining elements <NUM>, and are configured to couple with respective shaped concavities <NUM>, which have a shape mating with that of the convex curved portions <NUM>.

Advantageously, the shaped concavities <NUM> allow an elastic snap-in coupling which univocally determines the axial position of the milling tool <NUM>. In fact, when the milling tool <NUM> is coupled with the shaft <NUM>, the convex curved portions <NUM> are removably forced to be associated with the shaped concavities <NUM>.

Advantageously, the one or more convex curved portions <NUM> are sphere portions.

According to embodiments, the angular joint <NUM> comprises elastic keying tabs <NUM>, each provided with one of the convex curved portions <NUM>.

Each keying tab <NUM> has an extension in the direction of the longitudinal axis Z and has a tip <NUM> provided with the convex curved portion <NUM>, and a base <NUM>, opposite the tip <NUM>, stably attached to the shaft <NUM>. Advantageously, only the base <NUM> is stably attached to the shaft <NUM>, so that the keying tab <NUM> can flex with respect to the base <NUM> when pressure is exerted on the tip <NUM>.

The keying tab <NUM> can flex in an orthogonal direction to the longitudinal axis Z. For this purpose, the angular joint <NUM> has a chamber <NUM> orthogonally through in the shaft <NUM> and configured to allow the keying tabs <NUM> to flex at least during the coupling with the milling tool <NUM>.

It is clear that modifications and/or additions of parts may be made to the milling tool for prosthetic surgery as described heretofore, without departing from the field and scope of the present invention.

It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of milling tool for prosthetic surgery, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

Claim 1:
Milling device (<NUM>) for prosthetic surgery comprising:
a milling tool (<NUM>);
a handler body (<NUM>) with a rotating drive shaft (<NUM>) which develops along a longitudinal axis of rotation (Z), connected to said milling tool (<NUM>) to rotate said milling tool (<NUM>);
wherein said rotating shaft (<NUM>) is cannulated, being internally hollow and having a guide channel (<NUM>) parallel to said longitudinal axis (Z) and having an axis coaxial to said longitudinal axis (Z) and extending through an entire longitudinal dimension of said milling tool (<NUM>) and suitable to accommodate a guide element necessary to axially position the device (<NUM>) in the desired milling position during surgery,
wherein said rotating shaft (<NUM>) comprises an angular joint (<NUM>) rotatably coupled with said milling tool (<NUM>) to selectively define a plurality of inclined positions of said milling tool (<NUM>) with respect to said longitudinal axis (Z), and wherein said handler body (<NUM>) comprises a guide member (<NUM>) which comprises a stabilizer body (<NUM>) disposed eccentric with respect to said longitudinal axis (Z), configured to cooperate with said milling tool (<NUM>) so as to selectively define, amongst said plurality of inclined positions, a single specific stable inclined position of said milling tool (<NUM>), in which said milling tool (<NUM>) is able to rotate on itself around a specific milling axis (R) inclined with respect to said longitudinal axis (Z), thereby said milling axis (R) being inclined with respect to said axis of said guide channel (<NUM>).