Patent Description:
In the knee joint, the posterior cruciate ligament (PCL) plays a very important biomechanical role, particularly in providing the necessary stability to the joint.

As a result of major traumas, the ligament may suffer different degrees of injury. If the injury is partial, it is usually sufficient to use conservative procedures and to wait for the ligament to heal on its own. But if the injury is total, a ligament reconstruction operation is necessary to restore the correct functioning of the knee joint.

In this type of operation, a hole must first be created in the condyle of the femur to act as a housing for a head of the ligament under reconstruction. The position and diameter of the hole must be determined in such a way as to approximate as precisely as possible the insertion of the natural ligament. In so doing, the reconstructed ligament does not alter the biomechanics of the joint and restores its original functioning.

More specifically, the diameter and position of the ideal hole for inserting the reconstructed ligament need to approximate as precisely as possible the curvature of the patient's condyle.

The document <CIT> describes a tool intended to help a surgeon choose the size and position of the hole. This tool comprises a cannulated shaft equipped with a pistol handle at the proximal end and an interchangeable shaped tip at the distal end. A portion of the perimeter of the shaped tip is defined by a circular arc centred on the axis of the cannulated shaft. In the kit provided with the tool, various shaped tips are available and in each shaped tip the portion of the circular arc has a different radius. The use of the tool requires gradually bringing various shaped tips near to the condyle so as to be able to visually compare their respective radii and, thus, to identify the shaped tip that best approximates the natural curvature of the condyle. Once the most suitable shaped tip has been identified, it provides the measurement of the radius of the reamer head that must then be used to open the hole.

In addition, again by means of a visual comparison, the most appropriate shaped tip can easily be arranged so that the respective circular arc portion follows the curvature of the condyle. Once the shaped tip's correct position has been found, two small anchor tips that extend distally allow the instrument to be held firmly in place while a guidewire (typically a Kirschner wire) is inserted along the cannulated shaft. Thanks to the geometry of the tool, the guidewire is positioned in the centre of the circular arc that best approximates the curvature of the condyle.

Once the guidewire has been inserted, the tool can be removed and the bone reamer with the most suitable reamer head, which had been identified previously, can be used to open the hole.

Document <CIT> discloses a device for a correctly targeted formation of a drill bore centrally in a femoral attachment site of a posterior cruciate ligament of a knee joint comprises a hollow shaft for guiding a drill wire therethrough and a sighting element arranged at a distal end of the hollow shaft. Said sighting element has an edge for placing said sighting element via said edge to an outer margin of a femoral attachment site of a posterior cruciate ligament.

The applicant believes that these known tools, although widely used and appreciated, are not without room for improvement.

First of all, the system based on interchangeable shaped tips, although effective, is quite laborious and requires many successive operations in which the shaped tips are replaced before identifying the correct one. The different replacement operations of the shaped tips that follow one another result in a rather long overall time for arriving at the insertion of the guidewire.

In addition, the two anchor tips necessarily determine incisions in the cartilage of the joint. In cases where the cartilage is already damaged by trauma, the two small incisions do not result in a significant worsening of the overall condition of the knee. However, there are cases in which the cartilage is healthy despite the ligament being damaged. In these cases, the small incisions create additional damage that is added to the other, worsening the overall condition of the knee. Such damage is completely undesirable.

The purpose of the present invention is, therefore, to overcome the drawbacks highlighted above in relation to the prior art.

In particular, one of the tasks of the present invention is to provide an auxiliary tool for knee surgery that allows a simple and rapid procedure for choosing the size and positioning of the bone hole.

Another task of the present invention is to provide an auxiliary tool for knee surgery that does not result in cartilage injury when choosing the size and placement of the bone hole.

This purpose and these tasks are achieved by means of a tool in accordance with claim <NUM> and by means of a kit in accordance with claim <NUM>. Additional advantages can be obtained by means of the optional technical features set out in the dependent claims.

In order to better understand the invention and to appreciate its advantages, some of its non-limiting embodiments are described below, referring to the attached drawings, wherein:.

The invention relates to a minimally invasive auxiliary tool for knee surgery that is identified, as a whole, by the number <NUM>. The tool <NUM> comprises a handle <NUM> in proximal position, a shaft <NUM> defining an axis X and a shaped tip <NUM> in a distal position, wherein.

In the tool <NUM> according to the invention, the channel <NUM> preferably has a substantially straight development. Although slightly curved developments of the channel <NUM> can still guarantee the functionality of the tool <NUM>, the straight development is what makes its use easier and more intuitive, and which limits its size as much as possible.

The handle <NUM> preferably develops mainly along the axis X, thus assuming the typical shape of the handle of the type used for screwdrivers (see <FIG>). Although other shapes can be used for the handle <NUM>, the shape shown in <FIG> is the one that limits the overall dimensions of the tool <NUM> in each use position. This feature will be further described below, with reference to the advantages that it implies in the use of the tool <NUM>.

Above and below, the reference number <NUM> identifies either a single, a priori unspecified sector or the plurality of sectors as a whole. The reference numbers <NUM><NUM>, <NUM><NUM>. <NUM>n indicate, instead, the individual sectors when it is necessary to distinguish them from each other. A similar use is made with the reference numbers relating to other components that are present in the tool <NUM> in a plurality of examples, such as, for example, the circular arcs <NUM> and their respective radii R.

As already mentioned, the channel <NUM> connects the proximal end P with the distal end D of the tool <NUM>. In other words, through the channel <NUM> it is possible to completely cross the tool <NUM> from side to side. For example, it is possible to insert a guidewire, typically a <NUM> diameter Kirschner wire, into the opening of the channel <NUM> at the proximal end P and push the guidewire along the channel <NUM> until it exits the opening at the distal end D.

In accordance with the embodiment represented in the attached figures, the shaped tip <NUM> comprises four sectors <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, and <NUM><NUM> that are defined, respectively, by the circular arcs <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, and <NUM><NUM> and that have, respectively, the radii R<NUM>, R<NUM>, R<NUM> and R<NUM>. The following relation applies to this embodiment: R<NUM> < R<NUM> < R<NUM> < R<NUM>.

In accordance with other embodiments (not shown) the shaped tip <NUM> can comprise a different number of sectors <NUM>.

The sectors <NUM> are preferably arranged in a progressive manner. In other words, it is preferable that, considering first the sector with the minimum radius:.

Therefore, with specific reference to the example in <FIG>, starting from the sector <NUM><NUM> with the minimum radius R<NUM>:.

The range of measurements within which the radii R are chosen can be defined on a statistical basis with reference to the condyle measurements in patients undergoing cruciate ligament reconstruction surgery. The radii R of the circular arcs <NUM> are, preferably, comprised between <NUM> and <NUM>, and, even more preferably, between <NUM> and <NUM>.

Similarly, the difference between two consecutive radii R can be defined on a statistical basis. The difference between two consecutive radii R is preferably between <NUM> and <NUM>, even more preferably between <NUM> and <NUM>.

Preferably, the shaped tip <NUM> further comprises a plurality of blunt studs <NUM> that extend in a distal direction along the axis X. The blunt studs <NUM> allow to obtain a firm support on the surface of the bone and of the cartilage for the tool <NUM>. In addition, the fact that the studs are blunt prevents unwanted damage to the patient's cartilage.

Preferably, the blunt studs <NUM> are four in number (see <FIG> and <FIG>), but in some embodiments they can be even fewer, for example three, or more.

Preferably, the tool <NUM> according to the invention is used in a kit that also comprises a bone reamer with a plurality of interchangeable reamer heads, wherein the various heads have different radii r from each other. Even more preferably, the radius r of each reamer head is equal to the radius R of a sector <NUM> of the shaped tip <NUM>.

The following is a brief description of a method for using the tool <NUM> according to the invention during a posterior cruciate ligament reconstruction procedure.

The method essentially comprises the following steps:.

Preferably, the method further comprises the following steps:.

As the skilled person may well understand in view of the method, the technical features described above in relation to the tool <NUM> result in some significant advantages.

For example, since the shaped tip <NUM> and the whole tool <NUM> are rotated around the axis X, the screwdriver shape shown in <FIG> for the handle <NUM> allows to maintain the minimum encumbrance in any angular position of the tool <NUM>. A pistol-shaped handle might be more ergonomic in a single angular position of the tool <NUM>, but rotating the tool around the axis X it will soon interfere with other encumbrances.

Furthermore, the progressive arrangement of the sectors <NUM> allows to minimise the movement of the shaped tip <NUM> and to make it extremely efficient in order to identify the optimal sector <NUM>. In fact, thanks to this arrangement, one of the possible ways to identify the optimal sector <NUM> is to place a sector <NUM> with a lower radius R near the condyle and then to rotate the shaped tip <NUM> on the spot in a single direction until the optimal sector <NUM> is found.

Moreover, in the case of momentary indecision between two sectors <NUM> with similar radii, the progressive arrangement of the sectors <NUM> allows an extremely simple and rapid comparison to be made between the two sectors, since it is sufficient to rotate the shaped tip <NUM> a little. This limits errors in the choice of the reamer radius.

On the contrary, a non-progressive arrangement of the sectors <NUM> would require many more rotations of the shaped tip <NUM> in both directions and a greater risk of error in the choice.

As the skilled person can well understand, the invention enables to overcome the drawbacks highlighted above with reference to the prior art. In particular, the present invention provides an auxiliary tool for knee surgery that allows a simple and rapid procedure for the choice of the size and of the positioning of the bone hole. In fact, the comparison of the condyle with different sectors can be done simply by rotating the shaped tip <NUM> around the axis X, without any need to extract the tool and replace the shaped tip as required by the prior art.

In addition, the present invention provides an auxiliary tool for knee surgery that does not result in cartilage injury when choosing the size and placement of the bone hole. In fact, the blunt studs <NUM> that define the support on the bone do not cause any damage to the tissues.

Claim 1:
A minimally invasive auxiliary tool (<NUM>) for knee surgery, comprising a handle (<NUM>) in proximal position, a shaft (<NUM>) defining an axis (X) and a shaped tip (<NUM>) in distal position, wherein
- the handle (<NUM>), the shaft (<NUM>) and the shaped tip (<NUM>) define a channel (<NUM>) which connects the proximal end (P) of the tool (<NUM>) with the distal end (D) of the tool (<NUM>),
characterized in that the perimeter of the shaped tip (<NUM>) comprises a plurality of sectors (<NUM>), wherein each sector (<NUM>) is defined by a respective circular arc (<NUM>) centred on the axis (X) and wherein the circular arcs (<NUM>) defining various sectors (<NUM>) have respective radii (R) which are different the one from the others, for visually comparing the curvature of a condyle of a knee with the curvature of one of the sectors (<NUM>) by rotating the tool (<NUM>) around the axis (X) until identifying the optimal sector (<NUM>).