CH715848B1 - Modular acetabular prosthesis. - Google Patents

Abstract

A modular acetabular prosthesis (1, 2, 3, 4, 5) comprises an acetabulum (10, 20) and an augment (40, 50, 60, 70) that can be connected to the acetabulum (10, 20). The acetabular cup (10, 20) has a pole portion (13a) and an opposite entry portion (15, 25) with a peripheral edge (16, 26). The augment (40, 50, 60, 70) has an annular base (41, 51, 61, 71) from which at least one extension (42, 52, 54, 62, 72) extends. The peripheral edge (16, 26) of the acetabulum (10, 20) and the annular base (41, 51, 61, 71) of the augment (40, 50, 60, 70) are provided with mutually complementary screw threads (18, 28; 43, 53, 63, 73). The mutually complementary screw threads (18, 28; 43, 53, 63, 73) of the acetabulum (10, 20) and the augment (40, 50, 60, 70) are equipped with an anti-twist device which, when the acetabulum (10th , 20) and the augment (40, 50, 60, 70) prevents relative rotation of the acetabulum (10, 20) and the augment (40, 50, 60, 70).

Description

The present invention relates generally to an apparatus for use in orthopedic surgery, and more particularly to a modular acetabular cup having various modular attachment components for use in an orthopedic surgical procedure.

[0002] A natural hip joint may have congenital deformities or undergo degenerative changes due to a variety of causes. When these congenital deformities or degenerative changes are advanced and irreversible, it may eventually become necessary to replace a natural hip joint with a hip joint prosthesis. If the implantation of such a hip joint prosthesis becomes necessary, the head of the natural femur is first resected and a cavity is created in the intramedullary canal of the patient's femur to accommodate a shaft of the hip joint prosthesis. The stem of the hip joint prosthesis is inserted into the cavity in the femur, braced and optionally secured by cement or mechanical fasteners. Alternatively, the hip replacement can be impacted into the femur so that it is an interference fit in the bone and supported by the femur. If the patient's hip socket (acetabulum) also needs repair, the usual procedure is to remove any remnant of articular cartilage from the socket and attach an acetabular cup that can accommodate the head of the hip replacement to the natural socket. The acetabular cup is attached to the acetabular cup with cement, screws, or other suitable fasteners. In recent years, more and more so-called press-fit sockets have become established, in which the holding effect of the acetabular prosthesis in the acetabulum is based on a press fit between the outer surface of the acetabular prosthesis and the inner surface of the acetabulum, with the frictional forces between the acetabular prosthesis and the acetabulum being reduced by a rough surface and / or the formation of teeth, projections and the like of the acetabular prosthesis are reinforced.

A small proportion of patients undergoing such orthopedic surgical procedures may, for various reasons, require subsequent revision surgery to replace the prosthesis with a new prosthesis, commonly referred to as a "revision prosthesis". In this regard, a revision acetabular cup typically includes additional attachment points, such as integral flanges or hooks, that provide additional stability to the revision acetabular cup. These additional attachment points are typically required due to progressive bone loss or defects in the acetabulum such as collar/rim defects or pelvic discontinuity defects.

Various types of revision prostheses are currently available and different surgeons prefer different types of revision prostheses. Some surgeons prefer a so-called iliac flange that is integral with the acetabular cup and allows for further securing of the acetabular cup in the iliac region of the pelvis. Other surgeons prefer what is known as the obturator hook, which is able to provide some fixation of the acetabular cup by engaging the obturator foramen, which is a large opening adjacent to the acetabular cup. For this reason, a hospital must maintain a large inventory of different revision cups to accommodate the preferences of different surgeons. In addition, the surgeon must usually have several revision cups available during surgery to account for any type of condition that may arise or become apparent during the surgical procedure. This increased inventory of prosthetic devices increases the hospital's overall costs and inventory control. In addition, several prosthetic devices must be sterilized prior to surgery, requiring that the acetabular cups be available during surgery, increasing surgical time, cost and complexity of the surgical processes.

[0005] US Pat. No. 6,416,553 B1 discloses a modular acetabulum prosthesis which has modular additional attachment components for use in orthopedic surgical interventions. This acetabular prosthesis includes an acetabular cup and a variety of modular fasteners. In a preferred embodiment, this acetabular prosthesis comprises an acetabular cup, a fixation plate and a modular fixation element. The acetabular cup has an outer surface receivable within the patient's bony acetabular cup and an inner surface configured to receive a bearing cup having an annular region extending between the outer and inner surfaces. The mounting plate extends from the ring area and defines an interior channel. The modular fastener includes a fastener member and an engagement member. The mounting member is slidably received and positionable within the channel of the mounting plate. The engagement element is configured to engage a portion of the acetabulum such that after the fastener has been positioned in the canal, the modular fastener is constrained from rotational movement relative to the acetabular cup.

[0006] Document US 2018/0140427 discloses a prosthetic hip socket with a tongue augment, which is connected to the hip socket by means of a snap connection. The snap connection is provided along the perimeter of the acetabulum receiving opening for a condyle. This provides a universal acetabulum prosthesis which can be provided with a tab augment adaptable to the circumstances of a specific patient for attachment of the prosthetic acetabular cup in the pelvic bone.

From document US 5,871,548 a modular acetabular reinforcement system is known that comprises a substantially cup-shaped reinforcement body with peripheral flanges. One or more attachment wings of different shape and size are selectively and separately attachable to the flange of the reinforcement body. This system is mountable in a patient's acetabulum to reinforce the acetabulum and serve as a platform for other prosthetic components, such as an acetabular cup.

From the document US 2005/0288793 A1 an acetabulum prosthesis arrangement is known which has an outer socket for attachment in the acetabulum of a patient. The outer cup has an inner surface that receives a bearing insert. Complementary coupling features are formed on the inner surface of the outer cup and on the outer surface of the bearing insert to couple the bearing insert to the outer cup. A plurality of adapters are provided having an outer surface for engaging the inner surface of the outer cup and an inner surface for receiving the bearing insert. Each adapter has at least one radially extending flange for attachment to a bone surrounding the acetabulum. The flanges can have different sizes and shapes and can be arranged at different points of the adapter. The inner surfaces of the adapter contain the same mating features as the outer cup to allow them to receive a bearing insert. To attach the adapter to the outer pan, a polar threaded hole is provided on the outer pan and a through hole at the pole of the bearing insert, a screw being passed through the through hole of the bearing insert and screwed tight in the threaded hole of the outer pan. The coupling features preferably include complementary conically tapered surfaces to provide an interlock. The above-mentioned screw connection in the pole area can also be used to strengthen the locking, with the conical surfaces of the outer socket and the adapter being pressed against one another by tightening the screw and thus locking being forced.

In summary, a variety of different solutions already exist to allow the surgeon to select the appropriate acetabular cup and modular fixation components based on the patient's needs, thereby creating a versatile acetabular cup.

However, the acetabular prostheses under discussion still have a relatively large number of individual parts, which requires an increased inventory of prosthetic devices in the operating room, thereby increasing the hospital's overall costs and inventory control, or are complicated to assemble during surgery, which The risk of incorrect operation and, in general, the operation time, the costs and the complexity of the operation processes increases.

From the document DE 199 01 710 A1 an implantable prosthesis for the acetabular replacement is known, which includes an augment in the form of a support ring, which is used for attachment to the bone, and a socket shell, which is used to accommodate and support the femoral head. The socket shell can be screwed onto a raised collar of the support ring by means of a thread. This solution is based on the finding that micro-movements between the socket shell and the support ring are disadvantageous, since they lead to an unstable system and, as a result, metal abrasion with possible destruction of the surrounding tissue. The proposed solution is considered to be so good that it results in a prosthesis which, with regard to the static load conditions, corresponds to a one-piece design of socket shell and support ring.

In practice, however, it has been shown that a mere screw connection between the augment and the acetabulum is not always sufficient to prevent the augment and the acetabulum from twisting against one another. However, any relative movement between the augment and the acetabulum will delay ingrowth of the acetabular cup into the surrounding pelvic bones and should be avoided at all costs. Furthermore, the solution proposed in DE 199 01 710 A1 assumes that the socket shell is screwed onto the raised collar of the support ring up to the end of the thread. However, there are anatomically conditioned or due to an asymmetrical design of the hip joint prosthesis applications in which it would be desirable to fix the acetabular cup and the augment in a position that is only partially screwed into one another.

Therefore, there remains a need for an improved acetabular prosthesis that includes an acetabular cup and modular fasteners that uses a minimum of separate parts, in which the acetabular cup and modular fasteners are quick, easy and highly reliable to assemble, and which when assembled has a high stability for installation in the acetabulum of a patient. Preferably, such an acetabular cup should also provide a connection between the acetabular cup and the modular fasteners that can be fixed in various positions.

[0014] This object is achieved by providing an acetabulum prosthesis having the features of claim 1. Advantageous configurations of the invention emerge from the dependent claims and the description.

The present invention, in addition to solving the problem at hand, brings more surgical flexibility in the implantation of the acetabulum prosthesis and offers the surgeon a variety of surgical options at the time of the surgical intervention. The proposed acetabular cup can be configured for use in many circumstances. It reduces the need for hospital inventory and reduces overall surgical time, cost and complexity.

The modular acetabulum prosthesis according to the invention comprises an acetabular cup and at least one augment that can be connected to the acetabular cup. The acetabulum has an outer surface configured to be received in a patient's acetabulum and an inner surface configured to receive a bearing liner. When installed, the bearing insert serves to accommodate a ball head of a hip joint prosthesis in a plain bearing. The acetabular cup has a pole region and an entrance region opposite the pole region and bounded by a peripheral edge. The term "augment" as used herein means a fastener that, when connected to the acetabular cup, serves to stabilize and anchor the acetabular cup through additional attachment points in the pelvic bone. The augment has an annular base from which extends at least one appendage. According to the invention, the peripheral edge of the hip socket and the annular base of the augment are provided with mutually complementary screw threads, the mutually complementary screw threads of the hip socket and the augment being equipped with an anti-twist device which, when the hip socket and the augment are in the connected state, prevent relative rotation of the hip socket and the Augments prevented.

The modular acetabulum prosthesis according to the invention enables a surgeon to select the most suitable augment for the respective clinical condition of the patient from a large number of different augments in the course of an operation and to connect the selected augment to the acetabulum simply, quickly and securely by screwing it without additional acetabular prosthesis components are required to make this connection. With the appropriately selected augment, e.g. a flap augment, the primary stability of the acetabulum can be further improved after implantation in the acetabulum. Primary stability is the anchoring of the acetabulum in the period between implantation in the acetabulum and ingrowth of the acetabular cup into the pelvic bone without the acetabulum moving in the acetabulum when external forces are applied.

It is desirable in the acetabular cup of the present invention that the acetabular cup and augment not move relative to each other when connected, since any movement will delay ingrowth of the acetabular cup into the surrounding pelvic bones. In order to achieve this goal, the invention provides that the mutually complementary screw threads of the hip socket and the augment are equipped with an anti-twist device which prevents relative rotation of the hip socket and the augment when the hip socket and the augment are in the connected state.

A preferred anti-rotation device is realized in that the screw thread on the annular base of the augment has a non-circular cross section and the augment consists of an elastically deformable material, in particular a metallic material such as titanium. Since a circular screw thread and a non-circular screw thread cannot in principle be screwed together, before the acetabular cup and augment are connected to one another, the ring-shaped base of the augment and thus the screw thread are removed with a tool, e.g. a vise or an assembly device with specially designed clamping jaws , is resiliently biased from its non-circular shape to a circular shape, and in this resiliently biased state is readily threadably engageable with the screw threads of the acetabular cup. After the acetabular cup and augment are screwed together, the tension exerted by the tool on the annular base of the augment is released, causing the annular base of the augment to tend to return the screw threads to their original non-circular shape. However, this is not possible, since the screw thread of the hip socket counteracts such a tendency to move. As a consequence, the screw threads of the augment and the acetabulum press firmly against each other (possibly to the point of plastic deformation) and prevent the acetabulum and augment from twisting against each other due to the force fit and possibly form fit. In preferred embodiments of the invention, the non-circular cross section of the screw thread on the annular base of the augment is oval or at least partially polygonal.

In an alternative or additional embodiment of an anti-twist device according to the invention, at least one of the two mutually complementary screw threads of the acetabular cup and the augment is equipped with a stop into which the other screw thread can engage by screwing in with a defined minimum torque.

If the two mutually complementary screw threads of the hip socket and the augment are designed as fine threads, in particular with a pitch (pitch) of 0.5 to 1.5 mm, preferably 0.75 mm, they form a self-locking thread, which also represents an anti-twist device within the meaning of the invention when the screw threads are screwed up to the end of the thread turn. In this case the end of the thread forms a stop. Due to manufacturing tolerances, flat threads tend to have a certain end angle play, which can be undesirable depending on the augment used. In order to eliminate this final angular play, a defined stop can be created in that at least one of the two screw threads is designed with a section of changed pitch or with at least one projection protruding into the thread.

For a particularly rigid connection of the acetabulum and the augment of the acetabulum prosthesis, in one embodiment of the invention, the anti-rotation device comprises mechanical locking means, e.g prevent twisting.

According to a further embodiment of the acetabulum prosthesis according to the invention, an extension of the augment is designed to be deformable in order to engage in the acetabulum in a non-positive and/or positive manner in the deformed state. In this embodiment, the hip socket and the augment are first screwed together and then an extension of the augment is deformed, e.g. bent, in such a way that it engages the hip socket in a force-fitting manner or engages in a depression in the hip socket in a form-fitting manner.

In an embodiment that is preferred because of its universal implantability, the acetabular cup is rotationally symmetrical with respect to an axis of rotation running through the pole of the acetabular cup. Furthermore, because of the excellent anchoring in the acetabulum that can be achieved in this way, it is preferred if the hip socket has a section containing the pole with an essentially dome-shaped or hemispherical contour. This embodiment is referred to as a "spherical" hip socket, even if this hip socket only represents a section of a sphere and the spherical shape is only approximated. For example, with such a “spherical” acetabular cup, the equatorial area can be a few percent larger than the radius of an ideal spherical shape and/or the pole area can be flattened.

In particular for use as a revision hip socket prosthesis, the invention also provides that the section of the hip socket with a substantially dome-shaped or hemispherical contour is followed by a cylindrical section of the hip socket, which encompasses the peripheral edge of the hip socket. This cylindrical section serves primarily to better support and hold the bearing insert in the hip socket. It should be noted that although this cylindrical section forms the peripheral edge of the acetabulum, the screw thread does not have to be located directly at the open end region of the cylindrical section, but can be offset therefrom in the polar direction. In an embodiment of this acetabulum usable for most acetabulum deformities, the entrance region of the acetabulum defines an entrance plane that is perpendicular to the axis of rotation of the acetabulum, i.e., an equatorial plane. In an alternative embodiment of the acetabular cup, which is particularly suitable for displastic hips, the entry area of the acetabular cup defines an entry plane which is at an angle α of 95° to 118°, preferably at an angle α of 100° to 118°, to the axis of rotation the acetabulum is inclined. An angle α of 114° is currently considered optimal. Compared to the embodiment in which the entrance plane forms an equatorial plane, in the latter embodiment the entrance plane of the acetabulum is thus tilted by 5° to 25°, preferably by 10° to 18°, relative to an equatorial plane.

In one embodiment of the acetabular cup of the present invention, the screw threads of the acetabular cup are formed on the inner surface of the acetabular cup and the screw threads of the augment are formed on an outer surface of the annular base. In an alternative embodiment that allows for simplified machining of the inner surface of the acetabular cup, the screw threads of the acetabular cup are formed on the outer surface of the acetabular cup and the screw threads of the augment are formed on an inner surface of the annular base.

For additional anchoring of the hip socket prosthesis in the case of a severely deformed pelvis or a poor, e.g. The through openings offer the possibility of an additional primary fixation by screwing the hip socket to the ilium, ischium and/or pubic bone. The screw head can be designed as a round head or as a multidirectional screw head with stable angles.

For an optimal primary anchoring of the acetabulum in the acetabulum and to promote the ingrowth of the acetabulum into the acetabulum, it is provided according to the invention that the outer surface of the acetabulum is provided with a rough surface structure and optionally with a bioactive surface coating.

According to a further embodiment, the acetabulum prosthesis according to the invention has at least one additional augment in the form of a cranial augment, wherein the additional augment can be fastened to the acetabulum and/or to the augment with an annular base. This cranial augment is used to fill cranial defects in the acetabulum in order to move the center of rotation of the hip joint back to its original position.

It is further preferred to configure the acetabular cup and the at least one augment and to adapt them to one another in the acetabulum prosthesis according to the invention in such a way that they can be connected and fixed to one another in different positions, preferably in freely selectable positions. With this attachment option in different or freely selectable positions, the surgeon can respond optimally to the anatomy of the acetabulum and thus optimally adjust the holes in the acetabulum as well as the augment for screwing the acetabulum prosthesis in the acetabulum.

The invention will now be explained in more detail using exemplary embodiments with reference to the drawings. 1A shows a side view of a first embodiment of an acetabulum of a modular acetabular prosthesis according to the invention. Figure 1B shows the acetabulum of Figure 1A in plan view. Fig. 1C shows the acetabular cup of Fig. 1A in perspective from the entrance opening side. Fig. 1D shows the acetabular cup of Fig. 1A in a sectional view taken along line A-A of Fig. 1B. Figure 2A shows an augment of the modular acetabular cup in plan view. FIG. 2B shows the augment of FIG. 2A in a perspective view. 3A shows an assembled first embodiment of a modular acetabular cup according to the invention in side view. Figure 3B shows the acetabular cup of Figure 3A in plan view. Figure 3C shows the acetabular cup of Figure 3A in perspective. Figure 3D shows the acetabular cup of Figure 3A in a sectional view taken along line B-B of Figure 3B. 4A shows an assembled second embodiment of a modular acetabular cup according to the invention in side view. Figure 4B shows the acetabular cup of Figure 4A in plan view. Figure 4C shows the acetabular cup of Figure 4A in perspective. Figure 4D shows the acetabular cup of Figure 4A in a sectional view taken along line C-C of Figure 4B. 5A shows a second embodiment of an acetabular cup of a modular acetabular cup prosthesis according to the invention in side view. Figure 5B shows the acetabulum of Figure 5A in plan view. Figure 5C shows the acetabular cup of Figure 5A in perspective from the entry port side. Figure 5D shows the acetabulum of Figure 5A in a sectional view taken along line D-D of Figure 5B. 6A shows an assembled third embodiment of a modular acetabular cup according to the invention in side view. Figure 6B shows the acetabular cup of Figure 6A in plan view. Figure 6C shows the acetabular cup of Figure 6A in perspective. Fig. 6D shows the acetabular cup of Fig. 6A in a sectional view along line E-E of Fig. 6B. 7A shows an assembled fourth embodiment of a modular acetabular cup according to the invention in a perspective view. Figure 7B shows the acetabular cup of Figure 7A in a sectional view through the pole of the acetabular cup. Figure 8 shows an augment of the modular acetabular cup in plan view. 9A shows a cranial add-on augment of the modular acetabular cup in side view. FIG. 9B shows the additional cranial augment of FIG. 9A in plan view. FIG. 9C shows the additional cranial augment of FIG. 9A in a perspective view. Figure 9D shows the add-on cranial augment of Figure 9A in a sectional view along line F-F of Figure 9B. 10A shows an assembled fifth embodiment of a modular acetabular cup according to the invention in side view. Figure 10B shows the acetabular cup of Figure 10A in plan view. Figure 10C shows the acetabular cup of Figure 10A in perspective. Fig. 10D shows the acetabular cup of Fig. 10A in a sectional view along line G-G of Fig. 10B.

Reference is first made to Figures 1A, 1B, 1C and 1D, which show a first embodiment of an acetabulum 10 of a modular acetabular prosthesis 1 according to the invention. The acetabulum 10 has an outer surface 11 adapted to be received in a patient's acetabulum. The acetabular cup 10 is made of a metal, preferably titanium, and can be machined in one piece from a block by milling. For improved adhesion to the acetabulum, the outer surface 11 of the hip socket 10 is equipped with a rough surface structure 11a and can optionally also be provided with a rough titanium plasma coating and/or with a bioactive surface coating. The acetabulum 10 further includes an inner surface 12 adapted to receive a bearing liner, not shown. For improved fixation of the acetabulum 10 by screwing it in the pelvic bone, in particular for revision surgery, the acetabulum 10 is provided with through openings 19, which optionally have screw threads.

The acetabulum 10 is of the "spherical" type, i.e. it is rotationally symmetrical with respect to an axis of rotation 14 running through the pole 13 of the acetabulum 10 and has a substantially dome-shaped or hemispherical contour, optionally with a flattening of the pole region 13a and/or with excess radius in the area of the equator. The acetabular cup 10 has an entrance area 15 opposite the pole area 13a and delimited by a peripheral edge 16 . A cylindrical section 17 of the acetabulum 10, which encompasses the peripheral edge 16, adjoins the spherical section of the acetabulum 10 with an essentially dome-shaped or hemispherical contour. The entrance region 15 of the acetabular cup 10 defines an entrance plane 15a which is at an angle α to the axis of rotation 14 of the acetabular cup 10, which is a right angle. On the outer surface 11 of the acetabulum 10, more precisely on the peripheral edge 16, a circular screw thread 18 with a diameter a is formed. Alternatively, the screw thread 18 could also be designed as an internal thread on the inner surface 12 of the acetabulum 10, in particular on the inner surface of the cylindrical section 17.

In the figures 2A and 2B an augment 40 of the modular acetabular prosthesis according to the invention is shown. The augment has an annular base 41 from which two extensions 42 extend outwards, which are designed as tabs for screw connection to the pelvic bones. On the inside of the annular base 41 of the augment 40 a screw thread 43 is formed which is complementary to the screw thread 18 of the acetabulum 10 . In an alternative embodiment, if the screw threads 18 of the acetabular cup 10 are formed on the inner surface 12 of the acetabular cup 10 , the screw threads 43 of the augment 40 would be formed on an outer surface of the annular base 41 .

The modular acetabular cup 1 of the present invention is assembled by threading the augment 40 onto the acetabular cup 10 . This assembled state of the acetabulum prosthesis 1 is shown in Figures 3A, 3B, 3C and 3D.

Figures 4A, 4B, 4C and 4D show a second embodiment of a modular acetabular prosthesis 2 according to the invention, which differs from the first acetabular prosthesis 1 only in that a different augment 50 is used. This augment 50 also has an annular base 51 with a screw thread 53 on its inside. Three pairs of tab-shaped extensions 52 and an additional wide extension 54 for anchoring to the pelvic bones extend from the annular base 51 evenly distributed around the circumference.

In the figures 5A, 5B, 5C and 5D a second embodiment of an acetabulum 20 of a modular acetabular prosthesis according to the invention is shown. Similar to the first embodiment of the acetabular cup 10, the acetabular cup 20 also has an outer surface 21 adapted to be received in a patient's acetabulum. The acetabular cup 20 is made of a metal, preferably titanium, and can be machined in one piece from a block by milling. For improved adhesion to the acetabulum, the outer surface 21 of the hip socket 20 is equipped with a rough surface structure 21a and can optionally additionally be provided with a rough titanium plasma coating and/or with a bioactive surface coating. The acetabular cup 20 further includes an inner surface 22 adapted to receive a bearing liner, not shown. For improved fixation of the acetabulum 20 in the pelvic bone, in particular for revision surgery, the acetabulum is provided with through-openings 29, which optionally have screw threads.

The acetabular cup 20 is generally of the "spherical" cup type, i.e. it has a rotationally symmetrical portion with respect to an axis of rotation 24 passing through the pole 23 of the acetabular cup 20, having a substantially dome-shaped or hemispherical contour. The acetabular cup 20 has an entrance region 25 opposite the pole 23 and bounded by a peripheral edge 26 . An approximately cylindrical, slightly curved section 27 of the acetabulum 20, which encompasses the peripheral edge 26, adjoins the spherical section of the acetabulum 20 with a substantially dome-shaped or hemispherical contour. The entrance area 25 of the acetabular cup 10 defines an entrance plane 25a which is at an angle α to the axis of rotation 24 of the acetabulum 20 . In contrast to the first embodiment of the acetabular cup 10, in which the angle α is a right angle, in the second embodiment of the acetabular cup 20 the entrance plane 25a is at an angle α of 95° to 115°, preferably at an angle α of 100° to 118 ° to the axis of rotation 24 of the hip socket 20 inclined. An angle α of 114° is currently preferred.

On the outer surface 21 of the acetabulum 20, more precisely on the peripheral edge 26, a circular screw thread 28 is formed with a diameter a.

Figures 6A, 6B, 6C and 6D show a modular hip socket prosthesis 3 according to the invention, in which the augment 40 is screwed to the hip socket 20.

In the figures 7A and 7B another embodiment of a modular hip socket prosthesis 4 according to the invention is shown, in which the augment 50 is screwed to the hip socket 20.

In the acetabular cup 1, 2, 3, 4 of the present invention, it is desirable that the acetabulum 10, 20 and the augment 40, 50 not move with respect to each other when connected, since any movement will prevent ingrowth of the acetabular cup 1, 2 , 3, 4 delayed into the surrounding pelvic bones. In order to achieve this goal, the invention provides in embodiments of the hip socket prosthesis 1, 2, 3, 4 that the mutually complementary screw threads 18, 28; 43, 53 of the acetabulum 10, 20 and the augment 40, 50 are equipped with an anti-twist device which prevents relative rotation of the acetabulum 10, 20 and the augment 40, 50 when the acetabulum 10, 20 and the augment 40, 50 are connected .

As shown in FIG. 8, a preferred anti-rotation device is realized by providing an augment 60 whose screw thread 63 on the annular base 61 of the augment 60 has a non-circular cross-section, in this embodiment an oval cross-section a major axis b and a minor axis c perpendicular thereto, the minor axis c being shorter than the major axis b. The augment 60 has tab-shaped extensions 62 and consists of an elastically deformable material, in particular a metallic material such as titanium. In the unbiased rest state, the annular base 61 assumes the shape in which the oval cross-section of the screw thread 63 is present. Since the circular screw thread 18, 28 of the hip socket 10, 20 cannot in principle be screwed to the non-circular screw thread 63 of the augment 60, special precautions must be taken for connecting the hip socket 10, 20 to the augment 60. These precautions consist in clamping the annular base 61 of the augment 60 in a vice or a mounting device with specially designed clamping jaws in such a way that the clamping jaws of the vice or the mounting device engage the annular base 61 on opposite sides of the main axis b and upon contraction exert forces F on the annular base 61 from the opposite sides, elastically deforming the annular base so that the major axis b is shortened to a length corresponding to the diameter a of the circular screw thread 18, 28 of the acetabulum 10, 20. By compressing the annular base 61 on the major axis b, the minor axis c is stretched at the same time, so that the screw thread 63 assumes a circular shape with a diameter a. In this pretensioned state of the screw thread 63, the screw thread 18, 28 of the hip socket 10, 20 can now easily be screwed into the screw thread 63 of the augment 60. After the acetabular cup 10, 20 and augment 60 have been screwed together, the tension exerted by the tool on the annular base 61 of the augment 60 is released, causing the annular base 61 of the augment 60 to tend to unscrew the screw thread 63 to its original position -circular shape attributed. However, this is not possible since the screw thread 18, 28 of the hip socket 10, 20 counteracts this. As a consequence, the screw threads 63; 18, 28 of the augment 60 and the acetabulum 10, 20 against each other and prevent the acetabulum 10, 20 and the acetabular cup 10, 20 and the acetabulum 60 from twisting against each other due to the force fit and, if necessary, the form fit.

In an alternative embodiment of an anti-twist device for the hip socket prosthesis, at least one of the two mutually complementary screw threads 18, 28; 43, 53 of the acetabular cup 10, 20 and the augment 40, 50 is provided with a stop (designated schematically by the reference numeral 31 in Figure 4D) into which the other screw thread 43, 53; 18, 28 can intervene by screwing in with a defined minimum torque.

A further embodiment of an anti-twist device is characterized in that the two mutually complementary screw threads 18, 28; 43, 53, 63 of the hip socket 10, 20 and the augment 40, 50, 60 are designed as flat threads.

In yet another embodiment of the anti-twist device, one of the two screw threads 18, 28; 43, 53, 63 with a section of modified pitch or with at least one projection projecting into the thread (schematically symbolized by the reference numeral 32 in FIG. 3D).

In a further embodiment of the anti-rotation device, the anti-rotation device comprises mechanical locking means (not shown in the drawings) which can be used in a positive and/or non-positive manner at an interface between the hip socket and the augment.

Finally, anti-twist protection is also provided in that an extension of the augment 40, 50, 60, e.g. one of the extensions 42, 52, 54, 64 provided for attachment to a pelvic bone, or an additional dedicated extension, is designed to be deformable , in order to engage in the deformed state in a non-positive and/or positive manner in the acetabulum 10, 20.

9A to 9D show an additional augment 80 in the form of a cranial augment that is used in an acetabulum prosthesis according to the invention. The additional augment 80 has a body 81 which has the shape of a sector of a pan or is generally bulbous or convex. The surface of the body 81 may be serrated or roughened and optionally provided with a rough titanium plasma coating and/or with a bioactive surface coating. Threaded holes 82 for screwing to another augment and threaded holes 83 for screwing to an acetabulum are formed in the body 81 . The cranial add-on augment 80 is used to fill cranial defects in the acetabulum to correct the position of the hip joint.

10A to 10D shows a further embodiment of a hip joint prosthesis 5 according to the invention, which has an acetabulum 10 already described above and a tab augment 70 screwed thereto, which corresponds in its function to the augments 40, 50 and optionally the augment 60 described above . A detailed description of the augment 70 can therefore be dispensed with; it should only be mentioned that the lug augment 70 also has an annular base 71 with a thread 73 and lug extensions 72 . In addition, the augment 70 has a through hole 74 through which a screw 90 can be passed in order to be screwed to the cranial additional augment 80 . The cranial augment 80 can be additionally secured to the acetabular cup through holes formed in the acetabular cup 10 by means of a screw 91 inserted into the threaded hole 83 of the additional augment 80 .

Claims (19)

A modular acetabular prosthesis (1, 2, 3, 4, 5) comprising an acetabular cup (10, 20) and at least one augment (40, 50, 60, 70) connectable to the acetabulum (10, 20), the acetabulum (10, 20) having an outer surface (11, 21) adapted to be received in a patient's acetabulum and an inner surface (12, 22) adapted to receive a bearing liner, the acetabulum (10 , 20) has a pole area (13a) and an input area (15, 25) opposite the pole area (13a) and delimited by a peripheral edge (16, 26), the augment (40, 50, 60, 70) having an annular base (41, 51, 61, 71) from which extends at least one appendage (42, 52, 54, 62, 72), the peripheral edge (16, 26) of the acetabulum (10, 20) and the annular base (41, 51, 61, 71) of the augment (40, 50, 60, 70) with mutually complementary screw threads (18, 28; 43, 53, 63, 73) are provided, characterized in that the mutually he complementary screw thread (18, 28; 43, 53, 63, 73) of the acetabulum (10, 20) and the augment (40, 50, 60, 70) are equipped with an anti-twist device which, when the acetabulum (10, 20) and the augment (40, 50, 60, 70) prevents relative rotation of the acetabulum (10, 20) and the augment (40, 50, 60, 70). 2. Acetabular prosthesis according to claim 1, characterized in that the screw thread (63) on the annular base (61) of the augment (60) has a non-circular cross-section to prevent rotation and the augment (60) consists of an elastically deformable material. 3. Hip socket prosthesis according to claim 2, characterized in that the non-circular cross-section of the screw thread (63) on the annular base (61) of the augment (60) is oval or at least partially polygonal. 4. Hip socket prosthesis according to one of Claims 1 to 3, characterized in that at least one of the two mutually complementary screw threads (18, 28; 43, 53, 63, 73) of the hip socket (10, 20) and of the augment (40, 50, 60, 70) is equipped with a stop (31) into which the other screw thread (43, 53, 63, 73; 18, 28) can engage by screwing it in with a defined minimum torque. 5. Hip socket prosthesis according to one of claims 1 to 4, characterized in that the two mutually complementary screw threads (18, 28; 43, 53, 63, 73) of the hip socket (10, 20) and the augment (40, 50, 60, 70) are designed as fine threads, in particular with a pitch of 0.5 to 1.5 mm, preferably 0.75 mm. 6. The acetabulum prosthesis according to claim 4 or 5, characterized in that at least one of the two screw threads (18, 28; 43, 53, 63, 73) is designed with a section of changed pitch or with at least one projection (32) protruding into the thread . 7. Hip socket prosthesis according to one of Claims 1 to 6, characterized in that the anti-rotation device comprises mechanical locking means which are positively and/or non-positively connected to an interface between the hip socket (10, 20) and the augment (40, 50, 60, 70 ) can be used. 8. Hip socket prosthesis according to one of Claims 1 to 7, characterized in that an extension of the augment (40, 50, 60, 70) is designed to be deformable as an anti-twist device, in order in the deformed state to be non-positively and/or positively fitted into the hip socket (10, 20) to intervene. 9. Hip socket prosthesis according to one of claims 1 to 8, characterized in that the hip socket (10, 20) is rotationally symmetrical in relation to a rotation axis (14, 24) running through the pole (13, 23) of the hip socket (10, 20). is. 10. Hip socket prosthesis according to claim 9, characterized in that the hip socket (10, 20) has a section containing the pole (13, 23) with a substantially dome-shaped or hemispherical contour. 11. Hip socket prosthesis according to claim 10, characterized in that the section of the hip socket (10, 20) with a substantially dome-shaped or hemispherical contour, a substantially cylindrical section (17, 27) of the hip socket (10, 20) adjoins the peripheral edge (16, 26) of the acetabulum (10, 20). 12. Hip socket prosthesis according to one of claims 9 to 11, characterized in that the entrance area (15) of the hip socket (10) defines an entrance plane (15a) which is at a right angle (α) to the axis of rotation (14) of the hip socket (10). stands. 13. Hip socket prosthesis according to one of claims 9 to 11, characterized in that the entrance region (25) of the hip socket (20) defines an entrance plane (25a) which is at an angle (α) of 95° to 118°, preferably at an angle (α) is inclined from 100° to 118° to the axis of rotation (24) of the acetabulum (10). 14. Hip socket prosthesis according to one of the preceding claims, characterized in that the screw thread (18, 28) of the hip socket (10, 20) is formed on the inner surface (12, 22) of the hip socket (10, 20) and the screw thread (43, 53, 63) of the augment (40, 50, 60, 70) is formed on an outer surface of the annular base (41, 51, 61, 71). 15. Hip socket prosthesis according to one of claims 1 to 13, characterized in that the screw thread (18, 28) of the hip socket (10, 20) is formed on the outer surface (11, 21) of the hip socket (10, 20) and the screw thread ( 43, 53, 63) of the augment (40, 50, 60, 70) is formed on an inner surface of the annular base (41, 51, 61, 71). 16. Hip socket prosthesis according to one of the preceding claims, characterized in that the hip socket (10, 20) is provided with through openings (19, 29) which optionally have a screw thread. 17. Hip socket prosthesis according to one of the preceding claims, characterized in that the outer surface (11, 21) of the hip socket (10, 20) is provided with a rough surface structure (11a, 21a) and optionally with a rough titanium plasma coating and/or with a bioactive surface coating is. 18. Hip socket prosthesis according to one of the preceding claims, characterized in that the hip socket prosthesis (5) has at least one additional augment (80) in the form of a cranial augment, the additional augment (80) being attached to the hip socket (10, 20) and/or to the Augment (70) can be fastened with an annular base (71). 19. Hip socket prosthesis according to one of the preceding claims, characterized in that the hip socket and the at least one augment are configured and adapted to one another in such a way that they can be connected and fixed to one another in different positions, preferably in freely selectable positions