CH715848A2 - Modular acetabular prosthesis. - Google Patents

Abstract

A modular acetabular cup prosthesis (1, 2, 3, 4, 5) comprises an acetabular cup (10, 20) and an augment (40, 50, 60, 70) that can be connected to the acetabular cup (10, 20). The acetabulum (10, 20) has a pole area (13a) and an opposite entrance area (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) have 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 (10 , 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 prosthesis having various modular attachment components for use in an orthopedic surgical procedure.

A natural hip joint can have congenital deformities or experience degenerative changes due to a variety of causes. If these congenital deformities or degenerative changes are advanced and irreversible, it may ultimately be 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 shaft of the hip joint prosthesis is inserted into the cavity in the femur, supported and, if necessary, fastened by cement or mechanical fasteners. Alternatively, the hip joint prosthesis can be hammered into the thigh bone so that it rests in an interference fit in the bone and is supported by the thigh bone. If the patient's acetabulum also needs to be repaired, all remnants of the articular cartilage are usually removed from the acetabulum and an acetabular prosthesis, which can accommodate the head of the hip joint prosthesis, is attached to the natural acetabulum. The acetabular cup is attached to the acetabulum with cement, screws, or other suitable fasteners. In recent years, so-called press-fit cups have become more and more popular, in which the holding effect of the acetabular cup prosthesis in the acetabular cup is based on a press fit between the outer surface of the acetabular cup prosthesis and the inner surface of the acetabular cup, with the frictional forces between the acetabular cup prosthesis and the acetabulum by means of a rough surface and / or the formation of teeth, projections and the like of the acetabular prosthesis are reinforced.

In a small part of the patients who undergo such orthopedic surgical interventions, a subsequent revision operation may be necessary for various reasons to replace the prosthesis with a new prosthesis, which is commonly referred to as "revision prosthesis". In this context, a revisable acetabular prosthesis usually includes additional attachment points, such as integrated flanges or hooks, which provide additional stability for the revisable acetabular prosthesis. These additional attachment points are usually due to progressive bone loss or defects in the acetabulum, e.g. Collar / rim defects or pelvic discontinuity defects.

Different types of revision prostheses are currently available and different surgeons prefer different types of revision prostheses. Some surgeons prefer a so-called ilium flange, which is formed integrally with the acetabular cup prosthesis and enables the acetabular cup prosthesis to be further secured in the ilium region of the pelvis. Other surgeons prefer what is known as the obturator hook, which is able to ensure a certain fixation of the acetabular cup by engaging the obturator foramen, which is a large opening next to the acetabulum. For this reason, a hospital must maintain a large inventory of different revision sockets to suit the preferences of different surgeons. In addition, the surgeon typically needs to have multiple revision sockets available during the operation to accommodate any type of disease that may appear or become apparent during the surgical procedure. This increased inventory of prosthetic equipment increases the overall hospital cost and inventory control. In addition, multiple prosthetic devices must be sterilized prior to surgery by requiring the acetabular cups to be available during surgery, which increases surgical time, costs, and complexity of the surgical processes.

[0005] US Pat. No. 6,416,553 B1 discloses a modular acetabular prosthesis which has additional modular fastening components for use in orthopedic surgical interventions. This acetabular prosthesis includes an acetabulum and a variety of modular fasteners. In a preferred embodiment, this acetabular prosthesis comprises an acetabulum, a fastening plate and a modular fastening element. The acetabular cup has an outer surface that can be received in the patient's osseous acetabulum and an inner surface which is configured to receive a bearing shell with an annular region extending between the outer and inner surfaces. The mounting plate extends from the ring area and defines an inner channel. The modular fastener has a fastener and an engaging element. The fastening member is slidably received and positionable within the channel of the fastening plate. The engagement element is configured to engage a region of the acetabulum so that, after the fastening member has been positioned in the channel, the modular fastening element is prevented from rotating with respect to the acetabulum.

From the document US 2018/0140427 a prosthesis hip socket with a tab augment is known, which is connected to the hip socket by means of a snap connection. The snap connection is provided along the circumference of the opening in the acetabulum, which is used to receive a joint head. This provides a universal acetabular cup prosthesis which can be provided with a strap augment, which can be adapted to the circumstances of a specific patient, for fastening the prosthetic acetabulum 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 fastening wings of different shapes and sizes 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, e.g. an acetabulum.

From the document US 2005/0288793 A1 an acetabular prosthesis arrangement is known which has an outer socket for fastening in the acetabulum of a patient. The outer cup has an inner surface that receives a bearing insert. Coupling features that are complementary to one another are formed on the inner surface of the outer socket and on the outer surface of the bearing insert in order to couple the bearing insert to the outer socket. 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 locations on the adapter. The inner surfaces of the adapter contain the same coupling features as the outer socket so that they can receive a bearing insert. To attach the adapter to the outer socket, a polar threaded hole is provided on the outer socket and a through hole on the pole of the bearing insert, whereby a screw is passed through the through hole of the bearing insert from the inside and screwed into the threaded hole of the outer socket. The coupling features preferably comprise complementary, conically tapering surfaces, so that a locking is produced. The aforementioned screw connection in the pole area can also serve to reinforce the locking, with the conical surfaces of the outer socket and the adapter being pressed against one another by tightening the screw, thus forcing a locking.

In summary, it can be stated that there are already a large number of different solutions to allow the surgeon to select the appropriate acetabular cups and modular fastening components depending on the needs of the patient and thus produce a versatile acetabular prosthesis.

However, the acetabular prostheses discussed still have a relatively large number of items, which requires an increased inventory of prosthetic devices in the operating room and thus increases the overall costs of the hospital and the inventory control, or are complicated to assemble during the operation, which The risk of incorrect operation and, in general, the operating time, costs and the complexity of the operating processes increase.

From the document DE 199 01 710 A1 an implantable prosthesis for acetabular replacement is known which comprises 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 an upright collar of the support ring by means of a thread. This solution is based on the knowledge that micro-movements between the socket shell and the support ring are disadvantageous because 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 construction 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 in relation to one another. Any relative movement between the augment and the acetabulum delays the growth of the acetabulum prosthesis into the surrounding pelvic bones and should therefore 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 applications which are anatomically conditioned or due to an asymmetrical design of the hip joint prosthesis, in which it would be desirable to fix the acetabulum and the augment in a position that is only partially screwed into one another.

There is therefore still a need for an improved acetabular prosthesis comprising an acetabulum and modular fasteners that requires a minimum of individual parts, in which the acetabulum and the modular fasteners are quick, easy and very reliable to assemble, and which in the assembled state has a high stability for installation in the acetabulum of a patient. Such an acetabular cup prosthesis should preferably also offer a connection between the acetabulum and the modular fastening elements that can be fixed in various positions.

[0014] This object is achieved by providing an acetabular prosthesis with the features of claim 1. Advantageous configurations of the invention emerge from the subclaims and the description.

In addition to solving the problem posed, the present invention brings more surgical flexibility in the implantation of the acetabular 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 operating time, costs and complexity.

The modular acetabular prosthesis according to the invention comprises an acetabulum and at least one augment that can be connected to the acetabulum. The acetabular cup has an outer surface that is configured to be received in the acetabulum of a patient and has an inner surface that is configured to receive a bearing insert. When installed, the bearing insert serves to accommodate a ball head of a hip joint prosthesis in plain bearings. The hip socket has a pole area and an entrance area opposite the pole area, which is delimited by a peripheral edge. The term “augment”, as used herein, denotes a fastening element which, when connected to the acetabulum, serves to stabilize and anchor the acetabulum through additional fastening points in the pelvic bone. The augment has an annular base from which at least one extension extends. According to the invention, the peripheral edge of the acetabulum and the annular base of the augment are provided with mutually complementary screw threads, wherein the mutually complementary screw threads of the acetabulum and the augment are equipped with an anti-twist device which, when the acetabulum and the augment are connected, a relative rotation of the acetabulum and the Prevents augments.

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

In the acetabular prosthesis according to the invention, it is desirable that the acetabulum and the augment not move in relation to one another in the connected state, since any movement delays the ingrowth of the acetabular prosthesis into the surrounding pelvic bones. To achieve this goal, the invention provides that the mutually complementary screw threads of the acetabulum and the augment are equipped with an anti-twist device which prevents relative rotation of the acetabulum and the augment when the acetabulum and the augment are connected.

A preferred anti-rotation device is realized according to the invention 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, the annular base of the augment and thereby the screw thread is opened with a tool, e.g. a vice or a mounting device with specifically designed clamping jaws, elastically preloaded from its non-circular shape into a circular shape and can be easily screwed to the screw thread of the acetabulum in this elastically preloaded state. After the acetabular cup and augment are screwed together, the tension applied by the tool to the annular base of the augment is released, whereby the annular base of the augment tends to return the screw thread to its original non-circular shape. However, this is not possible because the screw thread of the acetabulum counteracts such a tendency to move. As a consequence, the screw threads of the augment and the acetabulum press firmly against each other (possibly up to the point of plastic deformation) and prevent the acetabulum and augment from twisting against each other due to the frictional connection and possibly form-locking. In preferred embodiments of the invention, the non-circular cross section of the screw thread on the ring-shaped base of the augment is oval or at least partially polygonal.

In an alternative or supplementary embodiment of an anti-rotation device according to the invention, at least one of the two mutually complementary screw threads of the acetabulum 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 acetabulum 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-rotation device within the meaning of the invention when the screw threads are screwed to the end of the thread. 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 end angle play, a defined stop can be created by designing at least one of the two screw threads 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. Pins that can be used in a form-fitting and / or force-fitting manner at an interface between the acetabulum and the augment and prevent mutual rotation.

According to a further embodiment of the acetabular cup prosthesis according to the invention, an extension of the augment is designed to be deformable in order to engage the acetabulum in a non-positive and / or form-fitting manner in the deformed state. In this embodiment, the acetabulum and the augment are first screwed together and then an extension of the augment is deformed, e.g. bent so that it engages positively on the acetabulum or positively engages in a recess in the acetabulum.

In an embodiment that is preferred because of its universal implantability, the acetabulum is designed to be rotationally symmetrical with respect to an axis of rotation running through the pole of the acetabulum. Furthermore, because of the excellent anchoring that can be achieved in the acetabulum, it is preferred if the acetabular cup has a section containing the pole with an essentially dome-shaped or hemispherical contour. In this embodiment, one speaks of a “spherical” acetabulum, even if this acetabulum represents only a section of a sphere and the spherical shape is only approximated. For example, in the case of such a “spherical” acetabulum, 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 acetabular prosthesis, the invention also provides that a cylindrical portion of the acetabulum adjoins the portion of the acetabulum with a substantially dome-shaped or hemispherical contour, which includes the peripheral edge of the acetabulum. This cylindrical section is primarily used to support and hold the bearing insert even better in the acetabulum. It should be mentioned that although this cylindrical section forms the peripheral edge of the acetabulum, the screw thread does not have to be located directly on the open end region of the cylindrical section, but can be offset from it in the pole direction. In one embodiment of this acetabular cup that can be used for most hip joint deformities, the entrance area of the acetabulum defines an entrance plane which is at right angles to the axis of rotation of the acetabulum, i. an equatorial plane. In an alternative embodiment of the acetabulum, which is particularly suitable for displastic hips, the entrance area of the acetabulum defines an entrance 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 to be optimal. Compared to that embodiment in which the input plane forms an equatorial plane, in the latter embodiment the input plane of the acetabulum is tilted by 5 ° to 25 °, preferably by 10 ° to 18 °, with respect to an equatorial plane.

In one embodiment of the acetabular cup prosthesis according to the invention, the screw thread of the acetabulum is formed on the inner surface of the acetabulum and the screw thread of the augment is formed on an outer surface of the annular base. In an alternative embodiment, which enables simplified machining of the inner surface of the acetabulum, the screw thread of the acetabulum is formed on the outer surface of the acetabulum and the screw thread of the augment is formed on an inner surface of the annular base.

For additional anchoring of the acetabulum prosthesis in the case of a severely deformed pelvis or a bad, e.g. osteoporotic bone structure, according to the invention, the acetabulum can be provided with through openings, which optionally have screw threads. The through openings offer the possibility of additional primary fixation by screwing the acetabulum onto the iliac, ischium and / or pubic bone. The screw head can be designed as a round head or as a multidirectional angle-stable screw head.

For optimal primary anchoring of the acetabulum in the acetabulum and to promote the growth of the acetabulum in 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 acetabular cup prosthesis according to the invention has at least one additional augment in the form of a cranial augment, the additional augment being attachable to the acetabulum and / or to the augment with an annular base. This cranial augment is used to fill in cranial defects in the acetabulum in order to move the center of rotation of the hip joint back into its original position.

It is further preferred, in the acetabular prosthesis according to the invention, to configure the acetabulum and the at least one augment so that they can be connected and fixed in different positions, preferably in freely selectable positions. This fastening option in different or freely selectable positions allows the surgeon to optimally respond to the anatomy of the acetabulum and thus optimally adjust the holes in the acetabulum and the augment for screwing the acetabulum prosthesis into the acetabulum.

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

Reference is first made to FIGS. 1A, 1B, 1C and 1D, which show a first embodiment of an acetabular cup 10 of a modular acetabular cup prosthesis 1 according to the invention. The acetabulum 10 has an outer surface 11 which is designed to be received in the acetabulum of a patient. The acetabulum 10 consists of a metal, preferably titanium, and can be manufactured in one piece from a block by milling. For improved adhesion to the acetabulum, the outer surface 11 of the acetabulum 10 is equipped with a rough surface structure 11a and can optionally be additionally provided with a rough titanium plasma coating and / or with a bioactive surface coating. The acetabulum 10 also has an inner surface 12 which is designed to receive a bearing insert (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" socket type, i. it is designed to be rotationally symmetrical with respect to an axis of rotation 14 running through the pole 13 of the acetabulum 10 and has an essentially dome-shaped or hemispherical contour, optionally with a flattening of the pole area 13a and / or with an excess of the radius in the area of the equator. The acetabulum 10 has an input area 15 opposite the pole area 13a, which is delimited by a peripheral edge 16. The spherical section of the acetabulum 10 with an essentially dome-shaped or hemispherical contour is followed by a cylindrical section 17 of the acetabulum 10, which includes the peripheral edge 16. The input area 15 of the acetabulum 10 defines an input plane 15a which is at an angle α to the axis of rotation 14 of the acetabulum 10, which is a right angle. On the outer surface 11 of the acetabulum 10, more precisely on the circumferential edge 16, a circular screw thread 18 with a diameter a is formed. As an alternative to this, 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 outward, which are designed as tabs for screw connection with 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. If, in an alternative embodiment, the screw thread 18 of the acetabulum 10 is formed on the inner surface 12 of the acetabulum 10, the screw thread 43 of the augment 40 would be formed on an outer surface of the annular base 41.

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

Figures 4A, 4B, 4C and 4D show a second embodiment of a modular acetabular cup prosthesis 2 according to the invention, which differs from the first acetabular cup 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. From the annular base 51, three pairs of tab-shaped extensions 52 and an additional wide extension 54 for anchoring to the pelvic bone extend evenly around the circumference.

In FIGS. 5A, 5B, 5C and 5D, a second embodiment of an acetabular cup 20 of a modular acetabular cup prosthesis according to the invention is shown. Similar to the first embodiment of the acetabulum 10, the acetabulum 20 also has an outer surface 21 which is designed to be received in the acetabulum of a patient. The acetabulum 20 consists of a metal, preferably titanium, and can be manufactured in one piece from a block by milling. For improved adhesion to the acetabulum, the outer surface 21 of the acetabulum 20 is equipped with a rough surface structure 21a and can optionally also be provided with a rough titanium plasma coating and / or with a bioactive surface coating. The acetabulum 20 also has an inner surface 22 which is designed to receive a bearing insert (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. it has a section which is rotationally symmetrical in relation to an axis of rotation 24 running through the pole 23 of the acetabulum 20 and which has an essentially dome-shaped or hemispherical contour. The acetabulum 20 has an input region 25 which is opposite the pole 23 and which is delimited by a peripheral edge 26. The spherical section of the acetabulum 20 with an essentially dome-shaped or hemispherical contour is followed by an approximately cylindrical, slightly curved section 27 of the acetabulum 20 which surrounds the peripheral edge 26. The entrance area 25 of the acetabulum 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 acetabulum 10, in which the angle α is a right angle, in the second embodiment of the acetabulum 20 the input plane 25a is at an angle α of 95 ° to 115 °, preferably at an angle α of 100 ° to 118 °, inclined to the axis of rotation 24 of the acetabulum 20. 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 with a diameter a is formed.

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

In FIGS. 7A and 7B, a further embodiment of a modular acetabular prosthesis 4 according to the invention is shown, in which the augment 50 is screwed to the acetabulum 20.

It is desirable in the acetabular cup prosthesis 1, 2, 3, 4 according to the invention that the acetabular cup 10, 20 and the augment 40, 50 do not move in relation to one another in the connected state, since any movement causes the acetabular cup prosthesis 1, 2 to grow in , 3, 4 delayed in the surrounding pelvic bones. In order to achieve this goal, the invention provides, in embodiments of the acetabular cup 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 in that an augment 60 is provided, the screw thread 63 of which on the annular base 61 of the augment 60 has a non-circular cross-section, in this embodiment with an oval cross-section a major axis b and a minor axis c at right angles 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 non-prestressed state of rest, 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 acetabulum 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 acetabulum 10, 20 to the augment 60. These precautions consist in the ring-shaped base 61 of the augment 60 being clamped in a vice or a mounting device with specifically designed clamping jaws in such a way that the clamping jaws of the vise or the mounting device engage on the opposite sides of the main axis b on the ring-shaped base 61 and when contracting, exert forces F on the annular base 61 from the opposite sides, which elastically deform the annular base so that the main axis b is shortened to a length which corresponds to the diameter a of the circular screw thread 18, 28 of the acetabulum 10, 20. By compressing the annular base 61 at the main axis b, the minor axis c is simultaneously stretched 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 acetabulum 10, 20 can now easily be screwed into the screw thread 63 of the augment 60. After the acetabulum 10, 20 and the augment 60 are screwed together, the tension applied by the tool to the annular base 61 of the augment 60 is released, whereby the annular base 61 of the augment 60 tends to keep the screw thread 63 in its original state -Circular shape traced back. However, this is not possible, since the screw thread 18, 28 of the acetabulum 10, 20 counteracts this. As a consequence, the screw threads 63; 18, 28 of the augment 60 and the acetabulum 10, 20 firmly against one another and prevent the acetabulum 10, 20 and the augment 60 from rotating in relation to one another due to the force fit and possibly the form fit.

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

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

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

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 form-fitting and / or force-fitting manner on an interface between the acetabulum and the augment.

Finally, it is also provided that an anti-rotation device is implemented in that an extension of the augment 40, 50, 60, e.g. one of the extensions 42, 52, 54, 64 or an additional dedicated extension provided for attachment to a pelvic bone is designed to be deformable in order to intervene positively and / or positively in the acetabulum 10, 20 in the deformed state.

9A to 9D show an additional augment 80 in the form of a cranial augment that is used in an acetabular prosthesis according to the invention. The additional augment 80 has a body 81 which has the shape of a sector of a socket, or is generally bulbous or convex. The surface of the body 81 can be designed with teeth or roughened and optionally provided with a rough titanium plasma coating and / or with a bioactive surface coating. In the body 81, threaded holes 82 for screwing with another augment and threaded holes 83 for screwing with an acetabular cup are formed. The additional cranial augment 80 is used to fill in cranial defects in the acetabulum in order 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 acetabular cup 10 already described above and a strap augment 70 screwed to it, which corresponds in its function to the augments 40, 50 and possibly the augment 60 described above . A detailed description of the augment 70 can therefore be dispensed with; it should only be mentioned that the tab augment 70 also has an annular base 71 with a thread 73 and tab 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 additionally be fastened to the acetabulum through holes formed in the acetabulum 10 by means of a screw 91 which is inserted into the threaded hole 83 of the additional augment 80.

Claims (19)

1. A modular acetabular cup prosthesis (1, 2, 3, 4, 5), comprising an acetabulum (10, 20) and at least one augment (40, 50, 60, 70) connectable to the acetabulum (10, 20), wherein the acetabulum (10, 20) has an outer surface (11, 21) which is designed to be received in the acetabulum of a patient, and an inner surface (12, 22) which is designed to receive a bearing insert, wherein the acetabulum (10 , 20) has a pole area (13a) and an input area (15, 25) opposite the pole area (13a), which is delimited by a peripheral edge (16, 26), the augment (40, 50, 60, 70) being 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), characterized in that the 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 and the augment (60) consists of an elastically deformable material. 3. acetabulum 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. acetabular 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 acetabulum (10, 20) and 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 being screwed in with a defined minimum torque. 5. acetabular 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 acetabulum (10, 20) and the augment (40, 50, 60, 70) are designed as a fine thread, in particular with a pitch of 0.5 to 1.5 mm, preferably 0.75 mm. 6. 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 formed with a section of changed pitch or with at least one projection (32) protruding into the thread . 7. acetabular prosthesis according to any one of claims 1 to 6, characterized in that the anti-rotation device comprises mechanical locking means which form a positive and / or non-positive fit at an interface between the acetabulum (10, 20) and the augment (40, 50, 60, 70 ) can be used. 8. Acetabular 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 in order to be positively and non-positively into the acetabulum (10, 20) in the deformed state to intervene. 9. acetabulum prosthesis according to one of claims 1 to 8, characterized in that the acetabulum (10, 20) is designed to be rotationally symmetrical with respect to an axis of rotation (14, 24) extending through the pole (13, 23) of the acetabulum (10, 20) is. 10. acetabulum prosthesis according to claim 9, characterized in that the acetabulum (10, 20) has a section containing the pole (13, 23) with a substantially dome-shaped or hemispherical contour. 11. acetabular prosthesis according to claim 10, characterized in that a substantially cylindrical portion (17, 27) of the acetabulum (10, 20) adjoins the portion of the acetabulum (10, 20) with a substantially dome-shaped or hemispherical contour, which the The peripheral edge (16, 26) of the acetabulum (10, 20). 12. Acetabular prosthesis according to one of claims 9 to 11, characterized in that the input area (15) of the acetabulum (10) defines an input plane (15a) which is at a right angle (α) to the axis of rotation (14) of the acetabulum (10) stands. 13. acetabulum prosthesis according to one of claims 9 to 11, characterized in that the input area (25) of the acetabulum (20) defines an input 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. Acetabular prosthesis according to one of the preceding claims, characterized in that the screw thread (18, 28) of the acetabulum (10, 20) is formed on the inner surface (12, 22) of the acetabulum (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. Acetabular prosthesis according to one of claims 1 to 13, characterized in that the screw thread (18, 28) of the acetabulum (10, 20) is formed on the outer surface (11, 21) of the acetabulum (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. acetabulum prosthesis according to one of the preceding claims, characterized in that the acetabulum (10, 20) is provided with through openings (19, 29), which optionally have a screw thread. 17. acetabular prosthesis according to any one of the preceding claims, characterized in that the outer surface (11, 21) of the acetabulum (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. acetabular prosthesis according to one of the preceding claims, characterized in that the acetabular prosthesis (5) has at least one additional augment (80) in the form of a cranial augment, the additional augment (80) on the acetabulum (10, 20) and / or on the Augment (70) with an annular base (71) can be attached. 19. acetabulum prosthesis according to one of the preceding claims, characterized in that the acetabulum and the at least one augment are configured and adapted to one another so that they can be connected and fixed to one another in different positions, preferably in freely selectable positions