Trial prosthesis, impactor and system for positioning and implanting a prosthesis

Abstract

The invention relates to a trial prosthesis (8) for positioning and implanting a prosthesis (40), comprising: a first opening (first trial prosthesis opening) (10) extending through the trial prosthesis (8), and a second opening (second trial prosthesis opening) (12) extending through the trial prosthesis (8), wherein: the first trial prosthesis opening (10) and the second trial prosthesis opening (12) run substantially parallel to each other; the trial prosthesis (8) is designed as a trial socket and has a trial prosthesis head (14); the first trial prosthesis opening (10) runs substantially centrally through the trial prosthesis head (14), and the second trial prosthesis opening (12) runs eccentrically with respect to the trial prosthesis head (14). The invention also relates to an impactor (16) for positioning and implanting a prosthesis (40), comprising a first opening (first impactor opening) (18) extending through the impactor (16), wherein: the impactor (16) is designed as a socket impactor and has an impactor head (24) which is designed in such a way that a prosthesis socket (42) can be plugged onto the impactor head (24); and the first impactor opening (18) runs eccentrically with respect to the impactor head (24). The invention further relates to a system (2) comprising such a trial prosthesis (8) and an impactor (16).

Description

[0001] PROSTHESIS, IMPACTOR AND SYSTEM FOR POSITIONING AND IMPLANTATION OF A PROSTHESIS

[0002] Technical field

[0003] The invention relates to a trial prosthesis and an impactor, each for positioning and implanting a prosthesis. Furthermore, the invention relates to a system for positioning and implanting a prosthesis comprising such a trial prosthesis and such an impactor, as well as the use of such a system for positioning and implanting a prosthesis, in particular a thumb saddle joint prosthesis.

[0004] background

[0005] Osteoarthritis is a degenerative joint disease in which the shock-absorbing cartilage layer between the joint surfaces gradually deteriorates. In advanced stages of this disease, there is a risk of joint stiffness. In Germany, more than five million people suffer from osteoarthritis, making it the most common joint disease.

[0006] A common form of osteoarthritis is osteoarthritis of the thumb's carpometacarpal joint, the joint between the trapezium bone and the first metacarpal bone in the hand. This form of osteoarthritis leads to significant health limitations for those affected, as the thumb plays a crucial role in hand function.

[0007] In cases of osteoarthritis of the thumb's carpometacarpal joint, surgery may become necessary after conservative treatment options, such as wearing an orthosis or undergoing physiotherapy, have been exhausted. In addition to removing the trapezium bone, an artificial joint replacement can restore thumb function and lead to significant pain relief. Besides osteoarthritis, an injury or other condition may also necessitate reconstruction of the thumb's carpometacarpal joint.

[0008] For the purpose of reconstructing the thumb's carpometacarpal joint, a so-called thumb carpometacarpal joint prosthesis can be implanted, whereby the worn joint between the trapezium and the first metacarpal bone is replaced by a mobile ball-and-socket joint. The ball-and-socket joint is intended to maintain or restore mobility in all directions as well as the original length of the thumb.

[0009] A thumb saddle joint prosthesis typically comprises a socket that is inserted into the trapezium bone. The prosthesis also usually features an insert attached to a neck, which is movably, and specifically rotationally, mounted within the socket. The neck extends into a shaft designed to reach into the first metacarpal bone of the thumb. Thus, the thumb saddle joint prosthesis restores a properly functioning connection between the thumb and the carpal bones.

[0010] The thumb saddle joint prosthesis is surgically implanted into the thumb saddle joint. The prosthesis replaces the worn joint surfaces of the first metacarpal bone and the trapezium, which are removed during the procedure. Before implanting the thumb saddle joint prosthesis, which remains in the patient's hand, the trapezium, into which the prosthesis will be inserted, is first prepared. For this purpose, a bone preparation instrument, such as a burr, is guided over a Kirschner wire, also called a K-wire, which serves as a reference or guide wire.

[0011] A Kirschner wire, or K-wire, is a medical instrument commonly used in orthopedics and traumatology. It is a type of wire made of stainless steel or titanium and typically has a smooth, cylindrical shape. Kirschner wires are used to fix or stabilize bone fragments, particularly during surgical procedures such as fracture repair or the correction of bone deformities, or as an aid during surgical interventions. The application of a Kirschner wire often involves piercing the bone or tissue to guide the wire through the tissue and hold the fragments in the desired position, or to anchor the wire in the bone or tissue and hold it in a specific position.

[0012] When using a K-wire as a guide or reference wire during bone preparation, the K-wire is typically inserted under radiological guidance to ensure ideal and central alignment of the acetabular cup. The K-wire is positioned as centrally as possible within the trapezium bone. This is verified radiologically during the procedure. A suitable burr is then inserted over this wire, and the acetabular socket is prepared. After preparation of the trapezium bone, the K-wire is removed, and a trial cup is inserted. The trial cup allows for verification of the alignment and desired insertion depth for the final implant (acetabular cup). The trial cup is then removed, and the acetabular cup is inserted. The acetabular cup is typically inserted using an impactor, specifically an acetabular cup impactor.

[0013] An impactor is a medical instrument regularly used in prosthetics to insert or adjust prosthetic components. Impactors in prosthetics can take various forms, depending on the type of prosthesis and the patient's specific needs. For example, an impactor can be used to securely implant and align a prosthetic component, such as a joint part, within the patient's body. Using an impactor ensures the prosthesis is firmly and securely positioned.Since, as a rule, during the implantation of a joint prosthesis, especially a thumb saddle joint prosthesis, the K-wire serving as a guide wire is removed after milling the socket and before inserting the trial implant, especially the trial socket, the trial socket and also the prosthetic socket are placed freehand and especially without a reference, which can easily lead to incorrect positioning or alignment of the prosthetic socket, especially in surgeons with little experience in the surgical technique (first users).

[0014] The present invention is therefore based on the objective of overcoming the disadvantages of the prior art. In particular, the invention is based on the objective of providing a trial prosthesis and an impactor, respectively, for positioning and implanting a prosthesis, especially a thumb saddle joint prosthesis, and a system comprising the trial prosthesis and impactor with which the positioning and / or alignment of the prosthesis, especially the thumb saddle joint prosthesis, can be made more error-free and reliable.

[0015] invention

[0016] According to a first teaching of the invention, the above-mentioned problem is solved by a trial prosthesis for positioning and implanting a prosthesis, comprising: a first opening extending through the trial prosthesis (first trial prosthesis opening), and a second opening extending through the trial prosthesis (second trial prosthesis opening), wherein the first trial prosthesis opening and the second trial prosthesis opening are substantially parallel to each other, wherein the trial prosthesis is designed as a trial cup and has a trial prosthesis head, wherein the first trial prosthesis opening extends substantially centrally through the trial prosthesis head, and wherein the second trial prosthesis opening extends eccentrically to the trial prosthesis head.In particular, the trial prosthesis and the first and second trial prosthesis openings are arranged and designed in such a way that the trial prosthesis can be guided along a guide wire, in particular one aligned in a straight line, by means of at least one of the openings extending through the trial prosthesis.

[0017] In the context of this application, an “essentially parallel alignment” or “essentially parallel course” is understood to mean an arrangement, alignment, or course in which the two essentially parallel objects, here the guide wires or the openings, are at least essentially parallel, in particular at an angle of 0° to each other, or at least close enough to this that they can be considered practically parallel. Thus, slight deviations from a perfectly parallel alignment may exist, but these are negligible for the purpose under consideration.

[0018] In addition to the trial prosthesis head, the trial prosthesis can have an elongated body extending from the trial prosthesis head. In particular, the trial prosthesis openings inside the body can run along its longitudinal direction.

[0019] Because the first trial prosthesis opening runs essentially centrally through the trial prosthesis head, the trial prosthesis, and in particular the trial acetabular cup, can be easily positioned centrally in the trapezium bone, especially using a guide wire. Because the second trial prosthesis opening runs eccentrically to the trial prosthesis head, a (further) guide wire can be easily positioned eccentrically to the trapezium bone, specifically outside the prepared acetabular base.

[0020] By providing a second trial prosthesis opening, positioned eccentrically to the trial prosthesis head, a second guide wire can be inserted as a reference. The trial prosthesis can thus serve as an instrument for placing this second (eccentric) guide wire in the trapezium bone. Specifically, the second trial prosthesis opening, and therefore the second guide wire, runs outside the acetabular base of the trapezium bone, into which the trial acetabular cup and later the final prosthetic cup are inserted. This ensures that a reference point for positioning the final prosthetic cup remains available, even after the removal of the first, centrally placed guide wire.

[0021] The trial prosthesis according to the invention thus prevents incorrect alignment of the prosthetic socket and makes the implantation technique safer for the surgeon, especially for a first-time user. Furthermore, potential revision surgeries that may be caused by incorrect alignment of the prosthetic socket can be avoided by using the trial prosthesis according to the invention.

[0022] The aforementioned problem is also solved according to a second teaching of the invention by an impactor for positioning and implanting a prosthesis, comprising a first opening extending through the impactor (first impactor opening), wherein the impactor is designed as a cup impactor and has an impactor head configured such that a prosthetic cup can be placed onto the impactor head, and wherein the first impactor opening extends eccentrically to the impactor head. In particular, the first impactor opening extends parallel to the longitudinal axis of the impactor body, which is preferably elongated.

[0023] In this way, the impactor according to the invention allows it to be guided over a guide wire that is positioned and runs through the eccentrically extending impactor opening and, in particular, outside the acetabular base of the trapezium bone, while simultaneously enabling work to be carried out in the center of the acetabular base using the impactor. In particular, with an existing reference point, a prosthetic acetabular cup, which can be attached to the impactor head, can be positioned centrally in the acetabular base using the eccentrically extending impactor opening. Furthermore, a prosthetic acetabular cup can be advantageously introduced and, in particular, implanted using the impactor head and with the aid of a reference point.

[0024] Consequently, the impactor according to the invention also offers the advantages already described for the trial prosthesis according to the invention, such that incorrect alignment of the prosthetic socket is prevented and the implantation technique can be made safer for the surgeon, especially for a first-time user. Furthermore, potential revision surgeries that may be caused by incorrect alignment of the prosthetic socket can be avoided by using the impactor according to the invention.

[0025] In particular, the impactor and the first impactor opening are arranged and designed such that the impactor can be guided along a guide wire by means of the opening extending through the impactor, preferably along a guide wire aligned in a straight line. Furthermore, the first impactor opening extends through the impactor body, which is also elongated, and in particular substantially parallel to its longitudinal axis.

[0026] According to a third teaching of the invention, the above-mentioned problem is also solved by a system for positioning and implanting a prosthesis, comprising: the described trial prosthesis or an embodiment thereof, and the described impactor or an embodiment thereof.

[0027] Furthermore, the above-mentioned problem is solved according to a fourth teaching of the invention by using the described system or an embodiment thereof for positioning and implanting a prosthesis, in particular a thumb saddle joint prosthesis.

[0028] The technical effects and advantages already described for the inventive trial prosthesis and impactor result accordingly for the system and its use according to the third and fourth teachings of the invention.

[0029] The trial prosthesis, the impactor, and the system preferably serve for the positioning and implantation of a prosthesis, whereby the positioning and implantation of at least a part of a prosthesis is understood to mean, for example, the socket of a prosthesis (prosthetic socket). The prosthesis is preferably a joint prosthesis, particularly preferably a thumb saddle joint prosthesis. The thumb saddle joint prosthesis particularly comprises a stem, a neck, and a socket, wherein the socket may have a conical or spherical shape. The neck may have an insert by means of which the neck and the shaft attached to it are movable, in particular rotatable, in the socket according to a ball-and-socket joint.

[0030] The trial prosthesis, the impactor, and the system, as well as their individual components, can have various sizes and shapes, depending in particular on the size and shape of the final prosthesis to be positioned and implanted. The individual components, especially the trial prosthesis and the impactor, are preferably made of materials commonly used for surgical instruments, such as stainless steel, titanium, cobalt-chromium alloys, plastics like (cross-linked) polyethylene (PE), composite materials, or ceramics.

[0031] To illustrate the technical effect of the teachings according to the invention and to describe possible embodiments of the trial prosthesis, the impactor, the system, and its use, the following section describes, step by step, an exemplary surgical procedure for using the trial prosthesis and the impactor or the system for positioning and implanting a thumb saddle joint prosthesis. At the same time, a comparison is made with a system known and previously used for positioning and implanting a thumb saddle joint prosthesis.First, in both a system for positioning and implanting a prosthesis, preferably a thumb saddle joint prosthesis, known according to the prior art, wherein only a guide wire is provided and neither the known trial prosthesis nor the known impactor has an opening, in particular neither the known trial prosthesis nor the known impactor has an eccentric opening, and according to the trial prosthesis, the impactor according to the invention and the system for positioning and implanting a prosthesis, preferably a thumb saddle joint prosthesis, or their respective use, the center of the trapezium bone (lat. os trapezium) is marked in a first step, in particular with the aid of the measuring gauge.

[0032] A gauge is a surgical instrument used to take precise measurements during surgical procedures. Gauges can take various forms, depending on the specific requirements of the procedure and the parameters to be measured; for example, they may include linear scales, protractors, drilling templates, or other measuring instruments. It is particularly important not to place the marking too far dorsally or radially off-center on the trapezium bone.

[0033] In a second step, both in a known system and in the system according to the invention or its components, a Kirschner wire or K-wire is placed in the marked center of the trapezium as the first guide wire. The position of the first guide wire is checked using intraoperative X-ray or fluoroscopy. Once the correct positioning of the first guide wire has been confirmed, it is drilled into the bone and thus anchored.

[0034] In a third step, both in a known system and in the system according to the invention or its components, a milling cutter is guided over the inserted and aligned first guide wire. The trapezium bone is milled using the milling cutter, in particular to prepare it for receiving the trial prosthesis, preferably a trial acetabular cup. This begins with milling using a starter cutter to open the sclerotic zone or the superficial bone, followed by milling with a spherical or conical cutter, depending on the design of the final prosthesis to be implanted later, especially the acetabular cup, which may, for example, have a spherical or a conical shape. At the end of this third step, the milling cutter should be as completely embedded in the bone as possible, and the base of the trapezium acetabular cup should be circumferentially surrounded by cortex, the outer layer of bone.

[0035] In a fourth step, according to the prior art, the first guide wire used to align the acetabular cup reaming is removed using the known system and components (trial prosthesis and impactor). Thus, when using the known system, there is no longer a reference point for the subsequent surgical procedure. Furthermore, in this fourth step, according to the prior art, the trial prosthesis, specifically the trial cup, is inserted to check the reaming and anchoring of the first guide wire after its removal. If faulty reaming and / or anchoring is detected in this step, the second and / or third steps described above may need to be repeated. This may involve repeating the fluoroscopy or taking X-rays and thus renewed radiation exposure.

[0036] In a fifth and final step, according to the prior art, the final prosthesis, in particular the acetabular cup, is positioned using a cup holder with the aid of a cup holder. However, due to the absence of a guide wire and the previously described lack of openings according to the invention, this positioning is not referenced. Since the surface of the trapezium bone is altered in inclination and shape, for example by osteoarthritis, this final step of cup positioning is generally difficult and prone to errors, especially for first-time users. In this final step of positioning and implantation, the final prosthesis, in particular the acetabular cup, is also progressively driven into place, preferably by means of an impactor, and thus definitively implanted.The impact occurs particularly in accordance with the hydroxyapatite (HAP) coated zone of the prosthesis, especially the prosthetic socket.

[0037] In contrast to the known fourth step described in the prior art, according to the inventive trial prosthesis, the inventive impactor, and the inventive system for positioning and implanting a prosthesis, preferably a thumb saddle joint prosthesis, or their respective use in a new fourth step, the first guide wire for aligning the acetabular cup milling cannot be removed. Instead, the trial prosthesis, in particular the trial cup, can be guided along the first guide wire via one of the trial prosthesis openings, especially the first trial prosthesis opening, and inserted over the first guide wire to check the milling and anchoring.

[0038] Subsequently, the second guide wire, preferably also a Kirschner wire or K-wire, can be inserted essentially parallel to the first guide wire over the trial prosthesis, particularly along the second trial prosthesis opening. The second guide wire is preferably also inserted in the trapezium bone, but outside the acetabular base. After placement of the second guide wire, the first guide wire and the trial prosthesis can be removed. Advantageously, the second guide wire can remain as a reference for positioning, particularly for the impactor, which for this purpose has a first impactor opening that runs eccentrically to the impactor head.Compared to the system known from the prior art in the described fourth step, thanks to the described embodiments of the trial prosthesis, the impactor, and the system for positioning and implanting a prosthesis, preferably a thumb saddle joint prosthesis, according to the invention, or their respective uses, the second step of the surgical procedure does not need to be repeated if an incorrect positioning of the trial prosthesis, in particular the trial socket, is detected, i.e., if it does not fit. Rather, it is only necessary, if applicable, to guide and position the milling cutter again over the first guide wire in accordance with the described third step in order to perform a new milling operation. This is because, through the system according to the invention, or rather,Its components or use, in contrast to the described use of the known system, allows the first guide wire to be removed before the insertion of the sample pan, so that it remains available as a reference in case of incorrect positioning of the sample pan.

[0039] In contrast to the known fifth step described in the prior art, according to the inventive trial prosthesis, the inventive impactor, and the inventive system for positioning and implanting a prosthesis, preferably a thumb saddle joint prosthesis, or their respective use in a new fifth step, the impactor can now be used to place the final prosthesis, in particular the prosthetic socket, while still maintaining the reference provided by the second guide wire. First, the prosthetic socket can be placed with the aid of the impactor. In particular, the impactor is guided along the second guide wire by means of the impactor opening. In this way, the impactor can be inserted via the second guide wire as a reference, and the prosthesis, in particular the prosthetic socket, can be centered within the milled cavity.

[0040] In this new final step of positioning and implantation, the final prosthesis, in particular the acetabular cup, can also be progressively driven into place, preferably using the impactor, and thus definitively implanted. The impaction is performed specifically against the hydroxyapatite (HAP)-coated zone of the prosthesis, especially the acetabular cup. Subsequently, the impactor and the second guide wire are preferably removed, and the implantation can be completed.

[0041] According to the described known or novel surgical procedure, in particular thanks to the trial prosthesis, the impactor, and the system for positioning and implanting a prosthesis, preferably a thumb saddle joint prosthesis, or their respective applications, after satisfactory alignment of the prosthetic socket has been established, a trial neck, straight or angled at approximately 15°, can be inserted as a further component of the trial prosthesis. After another X-ray check, the prosthetic neck and the prosthetic stem can then be inserted as further components of the final prosthesis. Furthermore, the surgical site can be thoroughly irrigated between each of the described steps and before inserting a new component.

[0042] In the following, further preferred embodiments of the trial prosthesis, the impactor and the system for positioning and implanting a prosthesis and the use of such a system or an embodiment thereof for positioning and implanting a prosthesis, in particular a thumb saddle joint prosthesis, are described, wherein the various embodiments can be combined with one another and apply in particular to the individual components trial prosthesis and impactor as well as to the system and its use.

[0043] According to another embodiment of the trial prosthesis, the trial prosthesis head is conical or spherical. Furthermore, the trial prosthesis head can have different sizes, particularly in both conical and spherical designs. For example, the trial prosthesis head can be sized to correspond to a final prosthesis cup diameter of 9 mm or 10 mm. In this way, the trial prosthesis, especially the prosthesis cup with the trial prosthesis head, can be advantageously and individually adapted to the specific needs of different patients. The milling cutter used to prepare the cupping area can also be conical or spherical and, in its diameter of, for example, 9 mm or 10 mm, correspond in particular to the final prosthesis cup.In particular, the diameter of the acetabular cup, the (outer) diameter of the trial prosthesis head and the (outer) diameter of the final prosthetic cup are essentially the same.

[0044] According to a further embodiment of the trial prosthesis, the trial prosthesis has at least one further opening extending through it (additional trial prosthesis opening). This additional trial prosthesis opening runs essentially parallel to the first and second trial prosthesis openings and eccentrically to the trial prosthesis head. This has the advantage that, depending on the size of the trapezium bone, either the second or the additional opening can be selected for positioning the second guide wire.

[0045] According to one embodiment of the trial prosthesis, the center point of the first trial prosthesis opening and the center point of the second trial prosthesis opening are offset by a parallel distance of at least 4 mm, preferably at least 5 mm, and particularly preferably at least 6 mm. In particular, the center point of the first trial prosthesis opening and the center point of the second trial prosthesis opening are separated by at least half the diameter, preferably half the diameter and an additional 0.5 mm, of the trial prosthesis head, especially the acetabular base. In this way, the first trial prosthesis opening can be positioned inside the acetabular base of the trapezium bone, particularly centrally within the acetabular base, whereas the second trial prosthesis opening is located eccentrically outside the acetabular base.For a trial prosthesis with a 9 mm diameter prosthesis head, for example, the center point of the second prosthesis opening is at least 4.5 mm, preferably at least 5 mm, for example 5.5 mm, away from the center point of the first prosthesis opening. A distance of at least 5 mm, for example 5.5 mm, ensures in particular that the second prosthesis opening lies outside the milled acetabular cavity. The distance between the outer circumference of the acetabular base and the outer circumference of the second prosthesis opening is, for example, 1.6 mm. The center point of a second prosthesis opening is, for example, 3 mm away from the center point of the second prosthesis opening. For a trial prosthesis with a 10 mm diameter prosthesis head, the distance between the outer circumference of the acetabular base and the second prosthesis opening changes.Here, the distance is, for example, 1.1 mm, while the other distances are the same. Preferably, in a trial prosthesis with a trial prosthesis head having a diameter of 10 mm, the center point of the second trial prosthesis opening is at least 5 mm, preferably at least 5.5 mm, for example 6 mm, away from the center point of the first trial prosthesis opening.

[0046] According to one embodiment of the impactor, the first impactor opening is located at a distance of at least 4 mm, preferably at least 5 mm, and particularly preferably at least 6 mm, from the center of the first impactor opening to the center of the impactor head. In particular, the center of the impactor head and the center of the first impactor opening are separated by at least half the diameter, preferably half the diameter and an additional 0.5 mm, of the prosthetic socket, especially the socket base. In this way, the design of the first impactor opening allows the impactor to be guided by means of the impactor opening over a reference, in particular a guide wire, which is located, in particular, outside the socket base of the trapezium bone.According to a further embodiment of the impactor, the impactor has at least one further opening extending through the impactor (further impactor opening), wherein the first impactor opening and the further impactor opening are essentially parallel to each other. This allows for greater flexibility in guiding the impactor along, for example, a guide wire. This is because different positions can be chosen for guiding the impactor along a guide wire. In particular, the impactor, especially a pan impactor, can also be guided along a guide wire by means of the further impactor opening.

[0047] Preferably, at least one further opening extending through the impactor (additional impactor opening) is eccentric to the impactor head. It is also possible to have several additional impactor openings that are eccentric to the impactor head. In addition to the first and the additional impactor opening, further impactor openings may be provided to further increase the flexibility of using the impactor, particularly with prostheses of different sizes. The impactor openings may be arranged parallel to each other, and their centers may be spaced between 1 mm and 5 mm, particularly between 2 mm and 4 mm, for example, 3 mm. In particular, the distance or parallel offset between the center of the additional impactor opening and the center of the first impactor opening may be between 1 mm and 10 mm, preferably between 6 mm and 8 mm.In particular, the dimensions correspond to those of the trial prosthesis used. However, since the inner diameter of prosthetic sockets generally does not differ even with different outer diameters, for example, 9 mm or 10 mm, the impactor can preferably be of a uniform size; in particular, an impactor of a uniform size can be used in both a system with a 9 mm trial prosthesis and a system with a 10 mm trial prosthesis. It is also conceivable that the at least one further opening extending through the impactor (additional impactor opening) runs essentially centrally through the impactor head.

[0048] According to one embodiment of the system, the system further comprises: a first guide wire, and a second guide wire, wherein the trial prosthesis and the impactor can each be guided along at least one of the guide wires by means of at least one of the openings extending through the trial prosthesis or the impactor.

[0049] The first guide wire can preferably be placed as a reference in the center of the trapezium, the center of the trapezium bone, and the system or trial prosthesis, as well as the first guide wire, are preferably configured accordingly. This can also be described as placement centrally in the acetabular base. The second guide wire can be inserted in the trapezium bone, like the first guide wire, and preferably substantially parallel to the first guide wire, but particularly outside the acetabular base, also called the acetabular bed or socket, and the system or impactor, as well as the second guide wire, are preferably configured accordingly.

[0050] The second guide wire, due to its advantageous placement outside the acetabular base, can remain in place as a reference for positioning and implanting the final prosthesis, particularly the final prosthetic acetabular cup, especially in contrast to the first guide wire, which is preferably removed after placement of the second guide wire when using the known system for positioning and implanting a prosthesis. Thus, error-prone freehand positioning and implantation of the final prosthesis is no longer necessary.

[0051] Furthermore, the impactor can preferably be inserted as an instrument for implantation via the second guide wire. Using the impactor, the prosthesis, in particular the acetabular cup, can then be implanted under guidance. Thus, thanks to the described embodiment of the system, the alignment originally referenced by the first guide wire is maintained during the implantation of the prosthesis, especially the acetabular cup. In particular, the originally referenced alignment can be a radiologically referenced alignment.

[0052] The guide wires can be made of materials such as stainless steel or titanium.

[0053] Description of the drawing

[0054] Exemplary embodiments and variants of the invention are explained in more detail below with reference to the drawings. The aspects of the disclosure can best be understood from the following detailed description in conjunction with the accompanying figures. The figures are schematic and simplified; they show only details to enhance understanding of the claims, while other details are omitted. The same reference numerals are used throughout for identical or corresponding parts. The individual features of each aspect can be combined with any or all features of the other aspects. These and other aspects, features, and / or technical effects are evident from and illustrated in the figures described below:

[0055] Figs. aa-b show schematic representations of embodiments of the system according to the invention or the trial prosthesis according to the invention and the impactor according to the invention for positioning and implanting a prosthesis, in particular a thumb saddle joint prosthesis;

[0056] Figs. 2a-f show schematic representations of steps one to five of an exemplary operative procedure when using a system known from the prior art for positioning and implanting a prosthesis;

[0057] Figs. 3a-b show schematic representations of steps four and five of an exemplary operative procedure when using an embodiment of the system according to the invention for positioning and implanting a prosthesis;

[0058] Fig. 4 shows a schematic representation of an embodiment of an impactor according to the invention for positioning and implanting a prosthesis, in particular a thumb saddle joint prosthesis; and

[0059] Fig. 5 shows a schematic exploded view of a prosthesis in the form of a thumb saddle joint prosthesis in different sizes.

[0060] Figures 1a and 1b show schematic representations of embodiments of the system 2 according to the invention, the trial prosthesis 8 according to the invention (Figure 1a), and the impactor 16 according to the invention (Figure 1b) for positioning and implanting a prosthesis 40, in particular a thumb saddle joint prosthesis. Such a prosthesis 40 designed as a thumb saddle joint prosthesis is shown by way of example in Figure 5.

[0061] In Fig. 1a, a first embodiment of the system 2 according to the invention is shown, in which the two guide wires 4, 6 and an embodiment of the trial prosthesis 8 according to the invention are shown.

[0062] System 2 according to Fig. 1a comprises a first guide wire 4 and a second guide wire 6, wherein the guide wires 4 and 6 run substantially parallel to each other. System 2 further comprises a trial prosthesis 8, which has a first trial prosthesis opening 10, a second trial prosthesis opening 12, and a further trial prosthesis opening 13, wherein the trial prosthesis openings 10, 12, and 13 run substantially parallel to each other and extend along the longitudinal axis of the elongated body of the trial prosthesis 8. The center point of the second trial prosthesis opening 12 and the center point of the further trial prosthesis opening 13 are each located more than half the diameter of the trial prosthesis head 14 from the center point of the first trial prosthesis opening 10, such that the second trial prosthesis opening 12 and the further trial prosthesis opening 13 are located eccentrically outside the acetabular base.The course of the trial prosthesis openings 10, 12, 13 within the body of the trial prosthesis 8 is shown schematically by means of dashed lines.

[0063] As shown, the trial prosthesis 8 can be guided along the guide wires 4, 6 by means of the first and second trial prosthesis openings 10, 12, and can therefore be moved along them. In particular, the trial prosthesis 8 is moved parallel to its longitudinal axis along the guide wires 4, 6 and the trial prosthesis openings 10, 12 are aligned accordingly.

[0064] The trial prosthesis 8 is designed as a trial socket and has a trial prosthesis head 14. The trial prosthesis head 14 is conical in shape. In contrast, the prosthesis 40 shown in Fig. 5, in the form of a thumb saddle joint prosthesis, has a spherical prosthesis socket 42, for which a correspondingly spherically shaped trial prosthesis head (not shown) can serve as an aid for positioning and implantation.

[0065] Furthermore, as shown in Fig. 1, the first trial prosthesis opening 10 is designed such that it runs essentially centrally through the trial prosthesis head 14. According to the illustration, the trial prosthesis 8 is guided along the first guide wire 4 via the first trial prosthesis opening 10. The second trial prosthesis opening 12 and the further trial prosthesis opening 13, on the other hand, run eccentrically to the trial prosthesis head 14. According to the illustration, the trial prosthesis 8 is guided along the second guide wire 6 via the second trial prosthesis opening 12, or the second trial prosthesis opening 12 can be used to insert the second guide wire 6 parallel to the first guide wire 4.

[0066] Fig. 1b shows an embodiment of system 2 or an embodiment of the impactor 16 according to the invention.

[0067] System 2 according to Fig. 1b thus also includes an impactor 16. The impactor 16 is shown in Fig. 1b in three different perspective views, i.e., from three different viewing directions (left, middle, and right view). The impactor 16 is designed as an acetabular impactor and has an impactor head 24, which is designed such that a prosthetic acetabular cup 42 can be attached to the impactor head 24.

[0068] The impactor 16 further comprises a first impactor opening 18, which is eccentric to the impactor head 24. The impactor also comprises a further impactor opening 20, which is eccentric to the impactor head 24 and parallel to the first impactor opening 18. It is also conceivable that a third impactor opening (not shown) runs essentially centrally through the impactor head 24 and parallel to the first impactor opening 18 and, optionally, to the further impactor opening 20.

[0069] The first impactor opening 18 and the second impactor opening 20 are essentially parallel to each other, as shown by the dashed lines representing the course of the impactor openings 18 and 20 inside the elongated impactor body. The impactor 16 can be guided along the guide wire 6 by means of the impactor opening 20, and can therefore be moved along it, in particular parallel to the longitudinal axis of the impactor body.

[0070] Figures 2a-f show schematic representations of steps one to five (first to fifth step) of an exemplary surgical procedure using a system known from the prior art for positioning and implanting a prosthesis 40, in particular according to the exemplary surgical procedure already described in the general description. In particular, such a system known from the prior art has only one guide wire, in particular for centric placement in the trapezium bone, and the known trial prosthesis or the known impactor are designed without openings, in particular without eccentric openings.

[0071] In step one (first step) according to Fig. 2a, the center 28 of the trapezium bone 26 is marked using the measuring gauge.

[0072] Subsequently, in step two (second step), shown in Fig. 2b, a Kirschner wire or K-wire is placed as a guide wire (first guide wire 4) in the marked center 28 of the trapezium bone 26. The position of the first guide wire 4 is checked by fluoroscopy or X-ray imaging, in particular its centric alignment in the trapezium bone 26.

[0073] In the third step (step three) shown in Fig. 2c, the trapezium bone 26 is milled out using a milling cutter 30, the milling cutter 30 being guided over the previously inserted and positioned guide wire 4.

[0074] In step four (fourth step) according to Fig. 2d, the guide wire 4, which previously served as a reference for the milling cutter 30, is removed, so that there is no longer a reference. Furthermore, as shown in Fig. 2d, the trial prosthesis 8, whereby the trial prosthesis 8 described in Fig. 1a can also be used, is inserted to check the milling and anchorage. If incorrect positioning is detected in step four, steps two and three must be repeated, so that a new fluoroscopy or the taking of further radiographs is necessary.

[0075] In the fifth and final step (step five), which is illustrated by Fig. 2e and 2f, the final prosthesis 40, here in the form of the prosthetic cup 42, is placed using a cup holder 32 and driven into place by means of an impactor, but without reference to the correct positioning.

[0076] Figures 3a-b show schematic representations of steps four and five of an exemplary surgical procedure when using an embodiment of the system 2 according to the invention for positioning and implanting a prosthesis 40, in particular corresponding to the surgical procedure already described in the general description. In the surgical procedure when using an embodiment of the system 2 according to the invention, steps one to three correspond to steps one to three of the exemplary surgical procedure shown in Figures 2a-c when using a system known from the prior art for positioning and implanting a prosthesis 40, wherein the trial prosthesis 8 according to Figure 1a is used as the trial prosthesis.

[0077] In step four according to Fig. 3a, it is shown that a first guide wire 4 is positioned centrally to the trapezium bone 26, in particular to the acetabular base (first image from the left in Fig. 3a). The trial prosthesis 8, here in the form of a trial acetabular cup, is guided along the first guide wire 4 via the first trial prosthesis opening 10 and inserted over it to check the milling and anchorage (second image from the left in Fig. 3a). Furthermore, the second guide wire 6 is inserted essentially parallel to the first guide wire 4 through the second trial prosthesis opening 12, also in the trapezium bone 26, but eccentrically to it and in particular outside the acetabular base (third image from the left in Fig. 3a). After insertion of the second guide wire 6, the trial prosthesis 8 and the first guide wire 4 can finally be removed (fourth image from the left in Fig. 3a), with the second guide wire 6 remaining in place as a reference.

[0078] Finally, in the concluding step five according to Fig. 3b, with the second guide wire 6 still serving as a reference, the final prosthesis 40, in particular the acetabular cup 42, is positioned using the impactor 16 (see the first image from the left in Fig. 3b). The impactor 16 is guided along the second guide wire 6 via the first impactor opening 18. After the progressive impaction of the acetabular cup 42 by means of the impactor 16, the impactor 16 is removed, and the acetabular cup 42 is definitively implanted (see the second image from the left in Fig. 3b). Now the second guide wire 6 can also be removed (see the third image from the left in Fig. 3b).

[0079] In further (not shown) steps, the other prosthetic components (see Fig. 5 and the corresponding figure description) can now be introduced and implanted.

[0080] Fig. 4 shows a schematic representation of an embodiment of an impactor 16 according to the invention for positioning and implanting a prosthesis 40, in particular a thumb saddle joint prosthesis, for example as a component of a system 2 when used in the surgical procedure according to Fig. 3a-b.

[0081] Figure 4 shows the impactor 16 in perspective view, which can be guided along the second guide wire 6 by means of the first impactor opening 18 or the further impactor opening 20 and on whose impactor head 24 a prosthetic cup 42 is placed for implantation.

[0082] Finally, Fig. 5 shows a schematic exploded view of a prosthesis 40 in the form of a thumb saddle joint prosthesis. The prosthesis 40 has a spherical prosthetic socket 42 (right in the illustration), a neck 44 with an insert 46 that can rotate within the prosthetic socket 42, corresponding to a ball and socket joint, and a stem 48. The neck 44 can, for example, be angled at a 15° angle or inserted straight into the insert 46. Alternatively, the prosthetic socket 42 can also be conical (not shown). In the assembled state of the prosthesis 40, the neck 44 engages with the stem 48. The stem 48 can be of different sizes, particularly with regard to length and / or diameter. By implanting such an artificial joint, the mobility of a wrist affected by thumb saddle joint osteoarthritis can be restored.By means of the system 2 according to the invention or its components trial prosthesis 8 and impactor 16, the positioning and implantation of the prosthesis 40 can be made more error-free and reliable, so that otherwise necessary revision operations can be avoided.

Claims

Patent claims 1. Trial prosthesis (8) for positioning and implanting a prosthesis (40), comprising: a first opening extending through the trial prosthesis (8) (first trial prosthesis opening) (10), and a second opening extending through the trial prosthesis (8) (second trial prosthesis opening) (12), wherein the first trial prosthesis opening (10) and the second trial prosthesis opening (12) are substantially parallel to each other, wherein the trial prosthesis (8) is designed as a trial cup and has a trial prosthesis head (14), wherein the first trial prosthesis opening (10) extends substantially centrally through the trial prosthesis head (14), and wherein the second trial prosthesis opening (12) extends eccentrically to the trial prosthesis head (14).

2. Trial prosthesis (8) according to claim 1, characterized in that the trial prosthesis head (14) is conical or spherical.

3. Trial prosthesis (8) according to claim 1 or 2, characterized in that the trial prosthesis (8) has at least one further opening (further trial prosthesis opening) (13) extending through the trial prosthesis (8), wherein the further trial prosthesis opening (13) runs substantially parallel to the first trial prosthesis opening (10) and to the second trial prosthesis opening (12) and eccentrically to the trial prosthesis head (14).

4. Trial prosthesis (8) according to one of claims 1 to 3, characterized in that the center point of the first trial prosthesis opening (10) and the center point of the second trial prosthesis opening (12) have a parallel offset of at least 4 mm, preferably at least 5 mm, particularly preferably at least 6 mm.

5. Impactor (16) for positioning and implanting a prosthesis (40), with a first opening (first impactor opening) (18) extending through the impactor (16), wherein the impactor (16) is designed as a cup impactor and has an impactor head (24) designed such that a prosthesis cup (42) can be placed on the impactor head (24), and wherein the first impactor opening (18) is eccentric to the impactor head (24).

6. Impactor (16) according to claim 5, characterized in that the center point of the first impactor opening (18) is located at a distance of at least 4 mm, preferably at least 5 mm, particularly preferably at least 6 mm, from the center of the impactor head (24).

7. Impactor (16) according to claim 5 or 6, characterized in that the impactor (16) has at least one further opening (further impactor opening) (20) extending through the impactor (16), wherein the first impactor opening (18) and the further impactor opening (20) are substantially parallel to each other.

8. Impactor (16) according to claim 7, characterized in that, that at least one further opening extending through the impactor (16) (further impactor opening) (20) is eccentric to the impactor head (24).

9. System (2) for positioning and implanting a prosthesis (40), comprising: a trial prosthesis (8) according to any one of claims 1 to 4, and an impactor (16) according to any one of claims 5 to 8.

10. System (2) according to claim 9, characterized in that the system further comprises: a first guide wire (4), and a second guide wire (6), wherein the trial prosthesis (8) can be guided along at least one of the guide wires (4, 6) by means of at least one of the openings (10, 12, 18, 20) extending through the trial prosthesis (8) and the impactor (16) by means of one of the openings (10, 12, 18, 20) extending through the impactor (16).

11. Use of a system (2) according to claim 9 or 10 for positioning and implanting a prosthesis (40), in particular a thumb saddle joint prosthesis.

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