Patent ID: 12208022

DETAILED DESCRIPTION

With reference to the attached figures, the reference number1indicates a positioning device of a surgical instrument for hip arthroplasty surgery200. In detail, this device is used for correctly positioning and orienting a surgical instrument for hip arthroplasty200, i.e. to correctly direct the different surgical instruments11needed during the hip joint replacement operation to the acetabular cup300.

This device comprises an arched structure2that has a first3and a second4end (visible inFIG.4).

In particular, the first end3can be positioned inside a patient500, while the second end4remains outside the patient500. In particular, the second end remains outside the patient, on the outer side of the leg, i.e. the side not facing the pelvic area.

Advantageously, this arched structure2is open and has, preferably, at least a first21, a second22, and a third23straight segment placed between them in sequence. Even more preferably, the first21and the second22straight segment are orthogonally connected in sequence with each other using a respective arched portion5, just as the second22and the third23straight segment are orthogonally connected in sequence with each other by means of a respective arched portion6.

The first section21preferably starts at the first end3, while the third section23ends with the second end4of the arched structure2.

In addition, the device1comprises a gripping element7, or handle, located at the second end4of the arched structure2, for which the surgeon can grasp and handle the device itself1.

At the first end3, the device1comprises a positioning and fixing head12; this head12has connection means13facing the gripping element7to couple with a temporary stem100that can be inserted inside a femoral canal600of a femur400of a patient500. The temporary stem100can be inserted into the femoral canal through the femoral neck that is cut, separating it from the rest of the femoral bone.

In other words, the positioning and fixing head12faces the opposite direction to the acetabular cup300.

Advantageously, these connection means13comprise a snap connection or snap fit, or a joint, interference, or push-button connection, or the like, to quickly join inside their respective seats made in the temporary stem100that can be inserted into the femoral canal600.

Once the first entry point P1has been identified for the first end3, this configuration, in particular the connection of the positioning and fixing head12to the temporary stem100, allows the second end to be correctly positioned above the outer portion of the patient's leg.

In other words, the arched structure2is shaped and sized in such a way that the second end4is positioned above the patient's femur, outside the leg, i.e. facing the opposite direction to the pelvic area.

An alternative configuration (not depicted) to the arched structure composed of three straight segments as described above, could involve a semi-circular structure, where the first3and the second4ends are arranged at the extreme points of the diameter of the semicircle.

As can be seen inFIGS.2-4and13-15, the positioning and fixing head12lies on a plane B that is tilted in relation to the first end3of the arched structure2, in particular in relation to a longitudinal axis3aof the first section21of the arched structure2, of an angle φ. This tilting angle φ of the positioning and fixing head12in relation to the first end3ranges between 5° and 85°, preferably 45°. In this way, the connection means13are oriented and facing towards the gripping element7.

The device1comprises, in addition, a surgical instrument8that can be coupled to the gripping element7at a seat9made in this gripping element7. The seat9may be at least partially open or, alternatively, closed and shaped like a slot, as shown in the attached figures, purely by way of example.

A surgical instrument8can be coupled to the gripping element7at this seat9.

In particular, the surgical instrument8comprises a stem10and a plurality of interchangeable tools or heads11that can be joined to the stem10.

The interchangeable heads or tools11can be, for example, scalpels for making the incision in a given position, rasps to smooth the inside of the acetabular cup, or abutment heads to insert the prosthesis into the acetabular cup.

The stem10is slidably movable inside the above-mentioned seat9of the gripping element7, so as to bring the joined tool closer or move it away from the acetabular cup300, as will be explained in detail below. The stem10can be thus be brought closer or moved away from the positioning and fixing head12.

Advantageously, the stem10is joined to the gripping element7so that it is basically oriented towards the positioning and fixing head12, defining an insertion angle α ranging between 30° and 60°, preferably 45°, in relation to a longitudinal symmetry axis7aof said gripping element7.

In other words, the stem enters the patient at an angle of about 45° in relation to the pelvic plane of a patient.

The stem10of the surgical instrument8has a longitudinal symmetry axis10a, transverse to the longitudinal symmetry axis7aof the gripping element7. The stem10is hinged to the gripping element7at the housing seat9and, therefore, has a degree of rotational freedom around an additional axis X that is orthogonal to both the axis10aof the stem10and the longitudinal symmetry axis7aof the gripping element7.

This degree of rotational freedom allows the stem10to travel around the axis X of an angle β (FIG.3) ranging between −15° and +105° in relation to the insertion angle α. In order to check the tilt of the stem10in relation to the gripping element7, a circular graduated scale15is provided on the gripping element7, indicating the rotational travel angles of the stem10. The zero of the circular graduated scale15(FIG.2) is placed at 45° to the insertion angle α, as shown inFIG.2. The angle α′ (FIG.3) on the graduated scale marks the angle of deviation of the stem10from the zero position of the stem10itself, which corresponds to an angle α=45° formed between the axis10aof the stem10itself and the axis7aof the gripping element7.

The angle formed by the axis10aof the stem10with the lying plane B of the positioning and fixing head12ranges between 30° and 150°, depending on the variable tilting of the stem10and on the angular position given to the positioning and fixing head12in relation to the end3of the arched structure2.

The gripping element7, positioned at the second end4of the arched structure2, has at least a first degree of translational freedom in relation to the arched structure2; in particular, it is slidably movable, at least partially, along the third straight segment23of the arched structure2, along a longitudinal axis7aof the gripping element itself coinciding with a longitudinal axis23aof the arched structure2. This freedom of translation is advantageously present to correctly align the stem10, and, therefore, its axis10a, with the acetabular cup300within which the tool that will be joined to the stem10must operate.

The need to adjust the distance of the gripping element7from the second straight segment22is basically due to the patient's size.

A fixing element14, such as a pin or a screw, fixes the position of the gripping element7along the arched structure2, in particular along the third straight segment23of this structure2.

The gripping element7has, in addition, at least a second degree of rotational freedom about a longitudinal symmetry axis thereof7a. This degree of rotational freedom enables the gripping element7to rotate about its longitudinal symmetry axis7aat an angle δ of + or −15° in relation to a zero position of normal use at which the stem10belongs to a plane A containing the arched structure2. In other words, the zero position of normal use of the gripping element7is configured when the stem is contained within the space of the arched structure2.

The rotational freedom of the gripping element7also causes the stem10to oscillate by the same angular width. This is useful when proceeding with the engagement of the surgical instrument joined to the stem with fixing screws that are offset in relation to the central axis of the acetabular cup. It is therefore necessary that it be possible for it to travel with the stem10, including to reach points not perfectly aligned with the central axis of the acetabular cup.

The positioning and fixing head12has a zero position in normal use (FIGS.1-5) in which it faces the gripping element7and the connection means13are axially and centrally cut by one plane A containing the arched structure2and that passes through the symmetry axis2aof the arched structure2.

The positioning and fixing head12has a degree of rotational freedom about the longitudinal symmetry axis2aof the arched structure2that allows it to travel according to an angle θ of about + or −20° in relation to the above-mentioned zero position (FIG.6). This makes it possible to rotate the whole arched structure2in relation to the positioning and fixing head12that remains fixed and integral with the temporary stem100inserted inside the patient's femoral canal.

Optionally, there may be a sort of protective sheath (not shown) around the stem10that prevents any friction between the lateral surface of the stem10during its movement and the patient's surrounding tissues.

In use, the patient is placed in a lateral position, turning the side to be operated on to the surgeon who locates the point to make a first incision P1, positioned above the acetabular cup.

The piriformis tendon of the joint tendon is then cut to expose the femur.

Then the surgeon proceeds with the upper cortical opening of the femur, the proximal reaming of the femur, and the proximal and distal broaching of the femur itself (FIG.8) for the insertion of a temporary stem100(FIG.9), which will be used during the surgical procedure and then removed for positioning the final stem.

The femoral neck is then cut off (FIG.10) and the head of the femur is removed from the acetabular cup (FIG.11). Before inserting the positioning device, which is the subject of this invention, the cut distal part of the femur is trimmed (FIG.12).

The temporary stem100is inserted into the femoral canal at the femur's femoral neck.

The surgeon inserts the first end3of the device and, in particular, the positioning and fixing head12, through the first incision P1(FIG.13) to fix the connection means13of the head12to the temporary stem100inserted into the femoral canal (FIG.14), at the femoral neck.

Once the positioning and fixing head12has been joined to the temporary femoral stem100, the arched structure2comes out of the patient's body and orients itself by positioning the second end4above the patient's leg at the level of the femur (FIG.14).

The arched structure is positioned on the outside of the leg, on the side opposite the pelvic area.

The position of the gripping element7along the third straight segment23of the arched structure2is adjusted so that the distance of the hinge point of the stem10, in other words of the seat9, from the arched portion6, placed between the second22and the third23straight segment, is basically equal to the length of the second straight segment22.

Once the gripping element7has been fixed, the stem10is tilted to 45° bringing the graduated scale to the zero position and the stem10is advanced, again at 45°, towards the patient's leg to make a second incision P2(FIG.14). In this way, the stem10is aligned with the femoral neck to reach the acetabular cup300.

Once the stem10is in position (FIG.15) it is possible to remove the arched structure and proceed by inserting, in succession, the various heads of the surgical tools that will be connected to the stem (FIGS.16and17).

Then the surgeon proceeds with the reaming of the acetabulum to then impact the new acetabular cup (FIG.18).

The arched structure2is advantageously repositioned for the insertion of the fixing screws of the new acetabular cup so that the screwdriver is more stable and more guidable in inserting the screws into the correct position.

Finally, the entire device and the temporary stem100, previously fixed in the femur, can be removed to replace it with the definitive stem700and, thus, to fix the final implant800(FIGS.19-21).

Compared to what is already known, the positioning device of a surgical instrument for hip arthroplasty surgery, which is the subject of this invention, means that the instrument is more stable and more guidable because the device is fixed directly to the femur.

With the use of this device, the field of vision of the surgical site is not obstructed, as, in contrast, is the case with devices of the prior art, allowing better vision. The direct connection to the femur, instead of to the acetabular cup, leaves the surgeon free to operate directly, and without obstacles, inside the acetabular cup to ream and insert the prosthesis.

The device that is the subject of this invention is easy for the surgeon to use and facilitates quick and safe operations for the patient. The tilting of the stem aligns the instrument with the surgical site and the possibility of moving the stem itself gives the surgeon greater freedom of action.

Finally, the device that is the subject of this invention is able to be configured as a correct and precise reference to the patient's anatomy during hip replacement operations.