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

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

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

It is also known that when, due to the pathologies as above, the spongy part of the bone is unable to support the prosthesis, it is necessary to create appropriate bone seatings for the implantation of a bone or metal filler that acts as a support for the prosthesis. This problem can become critical especially for knee prostheses and 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 in the case where it is necessary to recondition a previously implanted knee prosthesis, the creation of a bone seating, for the application of suitable support cones, first requires that a hole is made, with one or more boring devices of increasing diameter, and subsequently that the hole is shaped with a suitable milling device.

For this purpose, milling devices are known, which can be used during prosthetic surgery for the preparation of said seatings.

These milling devices typically comprise a handling body provided with a rotating rod 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 a connector to a drive member and a distal end connected to a milling tool, made to rotate by the drive member.

Given that both tibia and femur have an asymmetrical elongated conformation, one of the main problems encountered during the preparation of a bone seating is to avoid 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, and consequently with the longitudinal axis around which the rotating rod is driven, depending on the case, of the tibia or femur; such devices are therefore not able to follow the specific anatomy of the tibial and femoral bone.

To help the surgeon in the milling operation, the milling device often comprises, or is combined with, a guide rod which is previously inserted into the intra-medullary canal. The guide rod is slidably positioned inside the milling device along the longitudinal axis, and therefore is also coaxial to the milling axis. Although this solution allows the surgeon to follow a desired milling direction in a guided way, it does not allow to incline the milling axis with respect to the longitudinal axis and therefore to the axis of the intra-medullary canal, with the consequent risk of damaging, in particular perforating, the cortical zone. This risk occurs in particular when the milling diameter is increased to make the implant seating.

Sometimes, to avoid perforation of the cortical zone, the surgeon is therefore obliged to make bone seatings of a limited size which may, however, not be sufficient to guarantee adequate joint stability of the prosthesis, especially in the case where previous prostheses implants have damaged or otherwise rendered unusable an extended zone of the spongy part of the bone, or the removal of the previous implant has created significant bone loss or there is degeneration or lack of bone.

There is therefore a need to perfect a guided milling device for prosthetic surgery which 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 guided milling device for prosthetic surgery which is able to perform milling operations while avoiding damage to the cortical zone of the bone.

Another purpose of the present invention is to provide a guided milling device for prosthetic surgery which is able to obtain a stable milling with respect to a milling axis different from the axis of the intra-medullary canal or different from the axis of the guide rod that is inserted into it.

Another purpose of the present invention is to provide a guided 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 guided milling device for prosthetic surgery which is simple to assemble, in order to carry out the surgical operation, and to disassemble, in order to carry out cleaning and sterilization thereof.

The Applicant has studied, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

Document <CIT> discloses an exemplary guided milling device for prosthetic surgery.

In accordance with the above purposes, the guided milling device for prosthetic surgery comprises a milling tool rotating about a milling axis, and a handling body having a drive rotating rod which develops along a longitudinal axis of linear rotation. The rotating rod is connected to the milling tool in order to make the milling tool rotate about the milling axis.

The rotating rod is internally hollow and has a guide channel parallel to the longitudinal axis and in which a guide rod is positioned coaxially in a slidable manner, able to be positioned so as to extend beyond the milling tool along the longitudinal axis.

The milling axis is inclined with respect to the longitudinal axis, so that the milling tool is disposed inclined with respect to the rotating rod and also with respect to the guide rod.

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.

Embodiments described using the attached drawings concern a guided 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>, <FIG> concern a guided milling device <NUM> suitable for making seatings for bone fillers for the tibial bone, <FIG>, <FIG> concern a milling device <NUM> suitable for making seatings for bone fillers for the femoral bone and <FIG> concern a milling device <NUM> suitable for making seatings for a shoulder joint prosthesis, also called humeral prosthesis. <FIG> show embodiments of the milling device <NUM> respectively configured for the preparation of a seating in the tibial bone, in the femoral bone and in the shoulder joint, in which a guide rod <NUM> is slidingly associated. <FIG> concern another embodiment of the milling device <NUM> suitable for making seatings for a shoulder joint prosthesis, in particular for the glenoid, <FIG> and <FIG> concern the use for milling of the tibial and femoral bone respectively. Other embodiments shown in <FIG> concern a milling device <NUM> suitable for making seatings for the hip joint. In this case, the guide rod <NUM> which is coupled, during use, with the device <NUM> is the coupling cone of a hip prosthesis rod already previously implanted in the femoral canal.

The guided milling device for prosthetic surgery <NUM>, hereafter device <NUM>, comprises a milling tool <NUM>, rotating about a milling axis R, and a handling body <NUM> having a drive rotating rod <NUM> which develops along a longitudinal axis Z of linear rotation. The rotating rod <NUM> is connected to the milling tool <NUM> to make the milling tool <NUM> rotate about the milling axis R. This longitudinal axis Z is favorably a linear axis.

In accordance with some embodiments described here, the rotating rod <NUM> is cannulated, that is, it is internally hollow and has a guide channel <NUM> parallel to the longitudinal axis Z and suitable to house a guide or reference rod <NUM> necessary to axially position the device <NUM> in the desired milling position during the surgical operation.

The guide rod <NUM> is coaxially housed in the guide channel <NUM> and is slidably positioned therein to extend beyond the milling tool <NUM> along the longitudinal axis Z. The amount by which the guide rod <NUM> extends beyond the milling tool <NUM> is coordinated and aimed at the insertion of the guide rod <NUM> into the intra-medullary canal, in order to guide the milling operation (see for example <FIG>, <FIG>, <FIG>, <FIG>). As will be described in more detail below, the guide rod <NUM> can also be the coupling cone of a hip prosthesis rod previously implanted in the femoral canal (<FIG>).

In accordance with the present invention, the milling axis R is inclined with respect to the longitudinal axis Z, so that the milling tool <NUM> is disposed inclined with respect to the rotating rod <NUM> and also with respect to the guide rod <NUM>.

Consequently, according to the present invention, since the guide rod <NUM> is inserted into the guide channel <NUM> along the longitudinal axis Z, it follows that the milling axis R is actually also inclined with respect to such guide channel <NUM> and therefore to the guide rod <NUM>, when in use.

In accordance with some embodiments, the guide rod <NUM> has, at least in the proximal part, a transverse size, in particular a diameter, which is smaller than the transverse size of the guide channel <NUM>, so that it can be inserted in the latter, but with limited transverse play. In the distal part, on the other hand, the guide rod <NUM> can have a diameter which is also larger, which is a function of the anatomical canal.

The guide rod <NUM>, or at least a guide portion 50a thereof, can have a shorter length than the length of the guide channel <NUM> measured along the longitudinal axis Z.

The milling tool <NUM>, although it is guided along the guide rod <NUM> and therefore along the longitudinal axis Z, allows to define a bone seating having a development along an axis that is different to that of the guide rod <NUM>, that is, along the milling axis R inclined with respect to the longitudinal axis Z.

In accordance with possible embodiments, the guide rod <NUM> can be a reference pin, a more or less thin rigid shaft, a so-called Kirschner wire or "lead wire", for example in the case of a shoulder joint, or similar guide element. Depending on the applications, the guide rod <NUM> can have a shaped tip, with teeth, coils or other elements, to act as a reamer mean, for example in the event it is used for the tibial or femoral intra-medullary canal.

In particular, in accordance with some embodiments, shown in <FIG>, at least in the case of a milling device <NUM> for the femoral and/or tibial bone, the guide rod <NUM> can generally be a reaming device which, suitably driven by a motorized or manual drive mean, is used before the device <NUM> in order to create a first hole, or first holes of increasing diameters in the intra-medullary canal. Once the suitable diameter of the hole has been reached, the guide rod <NUM> is left in the intra-medullary canal where the hole was created and is released from the drive mean. After that, the device <NUM> is prepared so that the guide rod <NUM> is inserted into the guide channel <NUM> and acts as an axial guide during the milling operation. In the example described here, the guide rod <NUM> comprises a guide portion 50a able to cooperate with the guide channel <NUM>, and a reaming portion 50b which always remains outside the milling tool <NUM>.

According to the embodiment shown in <FIG>, the guide rod <NUM> is configured as a guide wire, also called Kirschner wire or k-wire, or it can also be a so-called "lead wire". In fact, in the case of the shoulder joint, the intra-medullary canal has a reduced cross-section compared to the tibial or femoral bone and it is not possible to use a reaming tool as in the applications to the femoral and tibial bones. As shown in <FIG>, the milling tool <NUM> is guided and advances along the wire, which in this case acts as a guide rod <NUM>, previously inserted and aligned along the final axis of the prosthetic implant. At the same time, the milling tool <NUM> is able to rotate and prepare a seating, for example of a spherical shape, oriented along an axis - the milling axis R - that is inclined with respect to that of the wire which acts as a guide rod <NUM> - coinciding with the longitudinal axis Z. In this specific case, the inclined axis along which the seating being prepared is oriented, defined by the milling axis R, is an axis essentially orthogonal to the eroded surface of the glenoid. In accordance with some embodiments, the handling body <NUM> comprises an angular positioning assembly <NUM> configured to define the inclined disposition of the milling tool <NUM> with respect to the guide rod <NUM> and to the rotating rod <NUM>, as described above.

The angular positioning assembly <NUM> comprises articulation means <NUM>, to connect the milling tool <NUM> to the rotating rod <NUM> in an articulated manner, and a positioning member <NUM>, disposed on a tubular handle <NUM> of the handling body <NUM>.

In accordance with some embodiments, the articulation means <NUM> can comprise an angular joint <NUM> (see for example <FIG>, <FIG> and <FIG>), disposed on one end of the rotating rod <NUM>, or, or in addition, a pair of articulated surfaces <NUM>, <NUM> (see for example <FIG>) respectively defined on the rotating rod <NUM> and on an internal part of the milling tool <NUM>, so as to configure a spherical joint. Favorably, the angular joint <NUM> lies on the longitudinal axis Z. In particular, the angular joint <NUM> essentially lies on the intersection of the longitudinal axis Z and the milling axis R.

For example, the angular joint <NUM> can be completely contained inside the milling tool <NUM>, see for example <FIG>, or be partly outside and partly inside the milling tool <NUM>, see for example <FIG> and <FIG>.

The articulation means <NUM> allow to selectively define a plurality of inclined positions of the milling tool <NUM> with respect to the longitudinal axis Z.

The positioning member <NUM> comprises a stabilizing body <NUM> disposed eccentric with respect to the longitudinal axis Z and configured to cooperate with the milling tool <NUM> so as to selectively define, from among the plurality of inclined positions as above, a single specific stable inclined position of the milling tool <NUM> with respect to the longitudinal axis Z.

On the basis of the conformation of the stabilizing body <NUM> and the reciprocal cooperation with the milling tool <NUM>, it is therefore possible to determine the desired angular position, which, once selected, is used to carry out the milling with the chosen angle of inclination of the milling axis R.

The specific stable inclined position allows the milling tool <NUM> to rotate with respect to the milling axis R.

The milling axis R is inclined with respect to the longitudinal axis Z of rotation of the rotating rod <NUM> by an angle of inclination α which varies according to the surgical application (application to the tibial bone, to the femoral bone or to the shoulder joint). Therefore it can be said that the milling tool <NUM> is inclined with respect to the rotating rod <NUM> and with respect to the guide rod <NUM>.

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

As shown schematically in <FIG>, with this configuration of the device <NUM> it is possible to create 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, this device <NUM> shapes the bone seating as above with respect to the angle of inclination α that corresponds to the specific stable inclined position. Optionally, the milling tool <NUM> can have the profile of a solid of revolution, obtained rotating a desired curve, which for example approximates the internal geometry of the tibia or femur. In particular, a known milling device is schematically shown in a dashed line, the device <NUM> in accordance with the embodiments described here is shown in a continuous line. Evidently, the known milling device comes much closer to the cortical zone <NUM>, with the risk of damaging it by perforating it.

In addition, this allows the user to create a deeper bone seating, being able to ensure, especially in the case of severe degeneration of the spongy part of the bone, a suitable joint stability of the prosthesis.

The milling tool <NUM> has a concave coupling seating <NUM> having a polar coupling aperture <NUM>, through which the guide rod <NUM> is made through. The guide rod <NUM>, therefore, has a smaller transverse size than the transverse size of the polar coupling aperture <NUM>. The rotating rod <NUM> is provided with a distal end <NUM> connected to the milling tool <NUM> inside the concave coupling seating <NUM> in correspondence with the polar coupling aperture <NUM>, and a proximal end <NUM> which has a tang <NUM> for attachment to a drive member to make the milling tool <NUM> rotate about the milling axis R. The distal end <NUM> is open to allow the guide rod <NUM> access to the guide channel <NUM>.

Here and hereafter, the relative terms "proximal" and "distal" when they describe the rotating rod <NUM> of the milling device <NUM> are defined with reference to the perspective of the milling device <NUM>. Thus, "proximal" refers to the direction of coupling with the attachment tang <NUM> and "distal" refers to the direction of coupling with the milling tool <NUM>. Consequently, the relative terms "proximal" and "distal" when applied to other components refer to the reference described above.

With particular reference to <FIG>, in the case of surgical application of the device <NUM> to the shoulder joint, the rotating rod <NUM> can be provided, in the head or distal position, with a front milling tip <NUM> which is outside the milling tool <NUM> and cooperating with the latter to create a seating for the prosthetic implant.

The front milling tip <NUM> can be made in a single piece with the rotating rod <NUM>, in correspondence with its distal end <NUM>, and is therefore integral in rotation with the rotating rod <NUM>. The front milling tip <NUM> has an axial aperture to allow the passage of the guide rod <NUM> in the guide channel <NUM>. When the milling tool <NUM> is driven in rotation and advances removing the bone, at the same time the front milling tip <NUM> also rotates, thus also making an axial hole in the bone (along the longitudinal axis Z) which houses the part of the rotating rod <NUM> axially protruding from the milling tool <NUM>. The front milling tip <NUM>, therefore, rotates about an axis coaxial to the longitudinal axis Z, and not about the milling axis R of the milling tool <NUM>. In particular, in this variant described with reference to <FIG>, the point of intersection of the milling axis R and the longitudinal axis Z falls outside the milling tool <NUM> (see in particular <FIG>).

The embodiment shown in <FIG> also shows a device <NUM> provided with a front milling head <NUM>. In this specific case, the device <NUM> is suitable for surgical applications of the hip joint.

The device <NUM> therefore comprises both lateral cutting edges - see the external surface of the milling tool <NUM> - and also front cutting edges - see the front part of the front milling head <NUM>.

The front milling head <NUM> is coupled with the milling tool <NUM> and disposed outside, beyond the polar coupling aperture <NUM>.

The front milling head <NUM> has a front aperture <NUM> substantially aligned with the polar aperture <NUM> of the milling tool <NUM> and through which the guide rod <NUM> is configured to pass.

In this solution, the guide channel <NUM> has a more limited extension/depth than the embodiments previously described. In fact, in this case the guide channel <NUM> has to contain a guide rod <NUM> which has a rather limited extension. The guide rod <NUM> in this case is the coupling cone of a hip prosthesis rod already previously implanted in the femoral canal.

The front milling head <NUM> also has, laterally, discharge apertures for the passage of the material removed and to facilitate the cleaning of the component.

The front milling head <NUM> has a curved lateral surface defining the angular joint <NUM>. The curved lateral surface, as a whole, defines a single convex curved portion <NUM>.

In particular, the coupling of the angular joint <NUM> and the polar aperture <NUM> of the milling tool <NUM> allows to position the latter according to any possible inclination whatsoever with respect to the longitudinal axis Z, while the final angle always remains determined by the positioning member <NUM>, see the enlarged detail in <FIG>.

In accordance with some embodiments, the angular joint <NUM> is positioned in correspondence with the distal end <NUM> of the rotating rod <NUM> or in the proximity thereof, and is rotatably coupled with the polar coupling aperture <NUM> with degrees of freedom able to allow the milling tool <NUM> to selectively assume a plurality of positions that are inclined with respect to the longitudinal axis Z.

In accordance with some embodiments, the handling body <NUM> comprises the tubular handle <NUM> which is coaxially coupled, in a removable manner, with the rotating rod <NUM> and is provided with the positioning member <NUM>.

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

The tubular handle <NUM> has a longitudinal channel <NUM> made through from the distal aperture <NUM> to the proximal aperture <NUM> for the rotational coupling with the rotating rod <NUM>. Advantageously, the longitudinal channel <NUM> has a size in a direction orthogonal to the longitudinal axis Z which is greater than that of the rotating rod <NUM>, thus allowing to prevent unwanted sliding.

In accordance with possible solutions, the tubular handle <NUM> can be made in a single piece or it can be made in two separate parts which can be selectively joined in order to form a shell to house the rotating rod <NUM>. Advantageously, the tubular handle <NUM> can be made of plastic material in order to reduce possible friction with the rotating rod <NUM> and with the milling tool <NUM> to a minimum.

In accordance with the embodiments described here, with particular reference to <FIG> and <FIG> and <FIG>, and which can be combined with all the other embodiments described, the size of the proximal aperture <NUM> is slightly smaller than the size of the longitudinal channel <NUM> in order to cooperate with a retaining edge, or tooth <NUM>, for example circumferential, of the rotating rod <NUM> and guarantee a desired positioning of the rotating rod <NUM> in the direction of the longitudinal axis Z. The retaining edge <NUM> allows the snap-in attachment of the tubular handle <NUM> onto the rotating rod <NUM>.

Advantageously, the tubular handle <NUM> can have, externally, an ergonomic and non-slip grip <NUM> so that it is easier for the user to grip and handle 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 camber in order to further improve the grip.

Advantageously, in some embodiments, see for example <FIG>, <FIG>, <FIG>, <FIG>, and which can be combined with all the embodiments described here, the tubular handle <NUM> can have, or be associated with, a safety clamping nut <NUM>. The safety clamping nut <NUM> secures the tubular handle <NUM> along the longitudinal axis Z in order to prevent the tubular handle <NUM> from being accidentally released, during the surgical act, due to pressure on it.

The positioning member <NUM> and in particular the stabilizing body <NUM> is configured to cooperate with the concave coupling seating <NUM>.

In accordance with some embodiments, the stabilizing 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 above described 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 positioning member <NUM> comprises the distal aperture <NUM> and a sliding coupling seating <NUM> configured to house a shaped portion <NUM> of the rotating rod <NUM> in order to guarantee a desired positioning of the rotating rod <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 exert an action of positioning the rotating rod <NUM> in cooperation with the positioning action exerted by the retaining edge <NUM>. In this way, once the rotating rod <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 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>, so as to allow the functional movement.

In accordance with some embodiments, for example shown in <FIG> and in <FIG>, the shaped portion <NUM> has a substantially cylindrical shape.

In some embodiments, see for example <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG> it can be provided that the stabilizing body <NUM> is coupled with the inside of the milling tool <NUM>, that is that the stabilizing body <NUM> acts as a male element for coupling with a respective female seating of the milling tool <NUM>. In other embodiments, as explained in detail below, a mechanical inversion can be provided in the coupling between the stabilizing body <NUM> and the milling tool <NUM> (for example <FIG>).

In some embodiments, see for example <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, the stabilizing body <NUM> has an external surface <NUM> coupled slidingly 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 that substantially defines the angle 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 having a diameter slightly larger than the diameter of the cylindrical portion that defines the external surface <NUM>, in order to guarantee the sliding coupling as above. This sliding coupling guarantees the single specific stable inclined position of the milling tool <NUM> with respect to the longitudinal axis Z.

The external surface <NUM> and the internal surface <NUM> are, for example, defined by two cylindrical and concentric portions, which can have an arc with an amplitude even smaller than <NUM>°.

The stabilizing 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 stabilizing 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 shown schematically in <FIG>, and also valid for the corresponding embodiments in which it is provided, the base surface <NUM> is altogether eccentric with respect to the longitudinal axis Z and is defined by a first portion 34a, delimited for illustrative purposes only with a dashed line, which is concentric with respect to the longitudinal axis Z, and by a second portion 34b which is eccentric with respect to the longitudinal axis Z, these portions 34a, 34b essentially being one a continuation of the other. The greater 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 as above.

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 knee joint prosthesis, the angle of inclination α is between about <NUM>° and <NUM>° (in this case, for example, in the operative variant with bilobed milling, see <FIG>) for the milling device <NUM> for the tibial bone, and is about <NUM>° for the milling device <NUM> for the femoral bone.

In accordance with some embodiments, shown in <FIG>, the shaped portion <NUM> can have a substantially conical shape.

Also, in some embodiments described using <FIG>, <FIG> and <FIG>, the milling tool <NUM> is provided with a central body <NUM> coupled slidingly with a seating <NUM> of the positioning member <NUM>. This seating <NUM> can for example be inclined 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 concave coupling seating <NUM> is defined inside the central body <NUM>. Both the seating <NUM>, and also the central body <NUM> are eccentric with respect to the longitudinal axis Z. This 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 shoulder joint prosthesis, in particular for the glenoid, the angle of inclination α can be selected, as needed, so that it is greater than <NUM>° and up to about <NUM>°.

In the embodiments described using <FIG>, <FIG> in which the seating <NUM> is provided, the latter has an internal surface <NUM> coupled slidingly with an external surface <NUM> of the central body <NUM> of the concave coupling seating <NUM> of the milling tool <NUM>. This internal 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 angle of the milling axis R with respect to the longitudinal axis Z. The external surface <NUM> of the central body <NUM> of the concave coupling seating <NUM> has a cylindrical profile having a diameter slightly smaller than the diameter of the cylindrical portion that defines the internal surface <NUM>. The internal surface <NUM> and the external surface <NUM> are, for example, defined by two cylindrical and concentric portions, which can have an arc with an amplitude even smaller than <NUM>°.

In accordance with some embodiments, described using <FIG>, the shaped portion <NUM> has a substantially cylindrical shape and has a convex upper articulation surface <NUM> which develops around the body of the rotating rod <NUM>. The central body <NUM> has a concave lower articulation surface <NUM> coupled slidingly, alternatively during the rotation, with the seating <NUM> and with the upper articulation surface <NUM>. The upper <NUM> and lower articulation surfaces <NUM> define the articulation means <NUM>. In the embodiments of <FIG>, this coupling therefore configures a ball joint having the function of a joint, which is disposed outside the milling tool <NUM>, differently for example from the variant of <FIG> in which the joint, see the convex portions <NUM> of the angular joint <NUM> described in detail below, is actually disposed inside the milling tool <NUM>. Advantageously, this joint, disposed outside the milling tool <NUM>, reduces the risk of wear and deterioration of the components during milling operations. In particular, the radii of curvature of the upper <NUM> and lower articulation surfaces <NUM> are the same. Furthermore, during use, the centers of these radii of curvature have to be coinciding with each other and coinciding with the center of rotation positioned on the longitudinal axis Z in a central position between anti-rotation constraint elements <NUM> that transmit the rotation. In this case, the center of rotation is outside the milling tool <NUM>. In particular, in this variant described with reference to <FIG>, the point of intersection of the milling axis R and the longitudinal axis Z falls outside the milling tool <NUM> (see in particular <FIG>).

In other embodiments, see for example <FIG>, it can be provided that the stabilizing body <NUM> is coupled with the outside of the milling tool <NUM>, that is, that the milling tool <NUM> acts as a male element for coupling with a respective female seating of the stabilizing body <NUM>.

In particular, this can be described with reference to the embodiments of <FIG>, in which the positioning member <NUM> has a seating <NUM> as described above, which, however, does not couple with a central body <NUM> inside the concave coupling seating <NUM> of the milling tool <NUM>, but rather couples outside the milling tool <NUM>.

In these embodiments, described by way of example with reference to the variant for interventions to the tibial bone, the stabilizing body <NUM> has an internal surface <NUM>, in particular with an annular conformation and delimiting the seating <NUM>, and in a mating manner the milling tool <NUM> has an external surface <NUM> able to produce a sliding coupling with the internal surface <NUM>.

The internal surface <NUM> is advantageously defined by a cylindrical portion and is inclined with respect to said longitudinal axis Z by an angle of inclination α which substantially defines the angle of the milling axis R with respect to the longitudinal axis Z.

The external surface <NUM> has a cylindrical profile having a slightly smaller diameter than the diameter of the cylindrical portion which defines the internal surface <NUM>.

The external surface <NUM> and the internal surface <NUM> are, for example, defined by two cylindrical and concentric portions, for example with an arc with an amplitude even smaller than <NUM>°.

In accordance with some embodiments, the anti-rotation constraint elements <NUM> are present on the distal end <NUM> of the rotating rod <NUM> and are operatively coupled with coupling seatings <NUM> provided in the concave seating <NUM> of the milling tool <NUM>. The anti-rotation constraint elements <NUM> are configured to angularly constrain the milling tool <NUM> with respect to the handling body <NUM> so that they are able to rotate integrally about the longitudinal axis Z. The anti-rotation constraint elements <NUM> are configured as means for transmitting torque, from the rotating rod <NUM> to the milling tool <NUM>.

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

The anti-rotation constraint elements <NUM> protrude radially from the profile of the rotating rod <NUM>, advantageously in a diametrically opposite position to each other if they are present in a number greater than one. Advantageously, in fact, the anti-rotation constraint elements <NUM> are two, in order to guarantee a better transmission of the rotation torque from the rotating rod <NUM> to the milling tool <NUM>. This diametrically opposite disposition of the two anti-rotation constraint elements <NUM> allows the milling tool <NUM> to oscillate or rotate on a plane orthogonal to the one passing through the anti-rotation constraint elements <NUM>, in such a way as to selectively assume a plurality of positions that are inclined with respect to the longitudinal axis Z, and in particular to assume a single specific stable inclined position defined by the same-shape coupling of the stabilizing body <NUM> with the concave coupling seating <NUM> of the milling tool <NUM>.

The anti-rotation constraint 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 for the transmission of the rotation torque from the rotating rod <NUM> to the milling tool <NUM>.

Advantageously, the coupling seatings <NUM> are in a number coherent with the number of anti-rotation constraint elements <NUM>. This guarantees a unique and determinate connection of the milling tool <NUM> onto the rotating rod <NUM>, preventing possible assembly errors.

In the embodiments described using <FIG>, in which the front milling tip <NUM> is provided and the point of intersection of the milling axis R and the longitudinal axis Z falls outside the milling tool <NUM>, the risk of wear and deterioration of the transmission tongues <NUM> is reduced, since the torque necessary for the milling and the torque necessary to create the seating of the spherical cap during the forward movement does not have to come exclusively from the transmission tongues <NUM>, but part of the milling action is performed by the cutting edges of the front milling tip <NUM> which is integral with, and made in a single piece on, the rotating rod <NUM> of the handling body <NUM> and, therefore, act independently of the milling tool <NUM>.

In accordance with some 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 each other with respect to the longitudinal axis Z.

In accordance with the embodiments described here, the anti-rotation constraint 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 rotating rod <NUM> in a diametrically opposite position with respect to that of the anti-rotation constraint elements <NUM> and are configured to couple with respective shaped concavities <NUM>, having a shape mating with that of the convex curved portions <NUM>.

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

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

In accordance with some embodiments, the angular joint <NUM> comprises elastic keying tongues <NUM> each provided with one of the convex curved portions <NUM>, for example conformed as a hemispherical portion (see for example <FIG>, <FIG>, <FIG>, <FIG>).

Each keying tongue <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 rotating rod <NUM>. Advantageously, only the base <NUM> is stably attached to the rotating rod <NUM> so that the keying tongue <NUM> can flex with respect to the base <NUM> when a pressure is exerted on the tip <NUM>.

The keying tongue <NUM> can flex in a direction orthogonal to the longitudinal axis Z. For this purpose, the angular joint <NUM> has a chamber <NUM>, <FIG> and <FIG>, made through orthogonally in the rotating rod <NUM> and configured to allow the inward flexion of the keying tongues <NUM>, at least during the coupling with the milling tool <NUM>.

In accordance with some embodiments, shown in <FIG>, a possible operating sequence of use of the milling tool <NUM> for surgical application to the tibial bone is shown. In the example described here, there is shown an operating sequence to obtain a "bilobed" type milling, useful in the event that the degeneration of the spongy part of the bone is rather extensive. In fact, in this case it is more appropriate to mill with a smaller milling tool <NUM>, performing a double milling as described below. However, the same procedure can be applied to produce a single milling, for example using a milling tool <NUM> of larger sizes.

After having performed the proximal resection of the tibial bone, perpendicular to the intra-medullary axis, a reaming tool is used that allows to define, possibly with several passes with increasing diameter, a lead-in channel <NUM> for the milling tool <NUM>, <FIG>. Advantageously, the part of the reaming tool that does not have the cutting edges remains protruding from the resection plane and acts as a guide rod <NUM> for the milling tool <NUM>.

Once the lead-in channel <NUM> has been made, the milling tool <NUM> is positioned vertically so that the longitudinal axis Z is aligned with the axis of development of the guide rod <NUM>, and moved closer to it so that the guide rod <NUM> couples slidingly in the guide channel <NUM> of the rotating rod <NUM>.

At this point, since the milling is asymmetrical, it is possible to define a right milling, in which the angle of inclination α with respect to the longitudinal axis Z has a positive value (<FIG>), and a left milling, in which the angle of inclination α with respect to the longitudinal axis Z has a negative value (<FIG>).

What is obtained is a seating that is substantially symmetrical with respect to a central (sagittal) plane transverse to the previously prepared lead-in channel <NUM>, and equidistant from the cortical zone <NUM> of the bone, <FIG>. This solution allows to simplify and speed up the milling operation for the preparation of such a seating <NUM> for a bone filler, and to avoid breaking the cortical zone of the bone in the event of extensive bone gaps following the failure of previous implants.

<FIG> are used to describe a possible operating sequence of use of a milling device <NUM> provided with a milling tool <NUM> for surgical application to the femoral bone. <FIG> shows the use of the reaming tool to create the guide channel <NUM> in the femoral bone. Also in this case, the guide rod <NUM> corresponding to the part of the reaming tool that remains protruding from the resection plane is indicated. After that, <FIG>, the milling tool <NUM> is coupled with the guide rod <NUM>. The latter, therefore, is aligned with the longitudinal axis Z, while the milling tool <NUM> is inclined along the respective milling axis R. <FIG> shows the milling operation, where it can be clearly seen that the milling has an angle of inclination α with respect to the longitudinal axis Z. <FIG> shows the seating <NUM> thus obtained, once the milling device <NUM> has been removed.

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

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 forms of guided milling device 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:
Guided milling device for prosthetic surgery, suitable for making seatings for the hip joint, said device comprising:
a milling tool (<NUM>) rotating about a milling axis (R);
a handling body (<NUM>) having a drive rotating rod (<NUM>) which develops along a longitudinal axis (Z) of linear rotation, connected to said milling tool (<NUM>) in order to make said milling tool (<NUM>) rotate about said milling axis (R);
wherein said rotating rod (<NUM>) is internally hollow and has a guide channel (<NUM>) parallel to the longitudinal axis (Z) in which a guide rod (<NUM>) is housed coaxially in a slidable manner, able to be positioned to extend beyond said milling tool (<NUM>) along said longitudinal axis (Z),
wherein said milling axis (R) is inclined with respect to said longitudinal axis (Z), so that said milling tool (<NUM>) is disposed inclined with respect to said rotating rod (<NUM>) and also to said guide rod (<NUM>),
characterised in that
said rotating rod (<NUM>) is provided, in the head or distal position, with a front milling head (<NUM>) which is outside the milling tool (<NUM>),
wherein the guide rod (<NUM>) which is coupled, during use, with the device (<NUM>) is a coupling cone of a hip prosthesis rod able to be previously implanted in a femoral canal.