WO2004030581A2

WO2004030581A2 - Endoprosthesis for a shoulder joint

Info

Publication number: WO2004030581A2
Application number: PCT/CH2003/000658
Authority: WO
Inventors: Martin Bernhard Walder
Original assignee: Martin Bernhard Walder
Priority date: 2002-10-06
Filing date: 2003-10-03
Publication date: 2004-04-15
Also published as: WO2004030581A3

Abstract

Disclosed is an annular adjusting template (55), by means of which a first eccentric element (27) of a shoulder joint prosthesis comprising a double eccentric element can be adjusted such that a head of a bone (39) that is provided with the second eccentric element can be placed upon the first eccentric element (27) in such a way that the axis (43) of said head of the bone intersects the center of the circular cross section (11) of the bone. In order to do so, the circular ring of the adjusting template (55) has to have merely the width A1 which corresponds to the shortest distance between the opposite eccentric form (47) in the head of the bone (39) and the edge (53) of the base of the head of the bone (39).

Description

Endoprosthesis for a shoulder joint

The invention relates to an endoprosthesis for a shoulder joint according to the preamble of claim 1, an adjusting tool for such an endoprosthesis, and a method for adjusting the position of a head axis of a joint head of an endoprosthesis for the replacement of a shoulder joint with respect to a bone cut surface on the humerus.

Various proposals have been made for shoulder prostheses to bring the dome into line with the cut surface on the humeral head using a double eccentric. The humeral head can be adjusted using two eccentrics, the eccentricities of which can be added vectorially, for a wide variety of endoprostheses.

An example of an endoprosthesis with two eccentrics interacting in this way is the endoprosthesis shown in US Pat. No. 6,228,120, which claims the priority of FR 98 00146. US-A-6,228,120 discloses surgical equipment for the implantation of a total shoulder prosthesis and a total shoulder prosthesis. The shoulder prosthesis comprises a shaft part with a humeral shaft and a metaphyseal section. This section is at an angle to the shaft and has an upper front that is inclined relative to the shaft. This metaphyseal section has a hemispherical depression around a central axis. Centered with this axis is a threaded hole in the bottom of the hemispherical recess. A humeral plate has a hollow hemisphere with an axis of rotation. The outer surface of the hollow hemisphere fits into the hemispherical recess. The inner surface of the hollow hemisphere is also hemispherical and has an axial, conical bore. A cone is also formed on the humeral plate and has a rotation axis which is arranged at a distance d with respect to the rotation axis of the ball joint. Centric with the axis of rotation of the

Ball joint has a hole in the cone, which is in the hollow cavity Hemisphere flows out. A mounting screw has a screw shaft with a lower, threaded portion. This screw shaft fits into the threaded hole in the base of the hemispherical recess. The screw shaft has a diameter that is smaller than the conical hole in the hollow hemisphere of the humeral plate. The mounting screw also has a head with a hemispherical pressing surface that fits into the inner surface of the hollow hemisphere. The hemispherical depression in the metaphyseal section of the shaft part, the outer surface and the inner surface of the hollow hemisphere and the hemispherical pressing surface of the fastening screw have a common center point O when the fastening screw is tightened. The prosthesis also includes a head with an upper articulation surface for interaction with a glenoid and a lower surface with a conical recess that fits onto the cone of the humeral plate. In an advantageous embodiment, the head has an axis of rotation which is eccentric with respect to the axis of rotation of the cone or the cone recess by the amount d ¹ .

A first eccentric is thus formed by the cone, which is rotatable about the axis of rotation of the hemispherical depression. A second eccentric is formed by the head, which can be rotated about the cone axis.

Such a double eccentric permits adjustment of a deviation of a spherical cap axis from a neck axis predetermined on the shaft part. This difference varies from patient to patient. The deviation depends on a position of the shaft part in the humerus bone and an individual design of the humeral head. By turning the two eccentrics against each other, it is possible to adjust the eccentricity of the head with respect to the axis of rotation of the hemispherical depression in the metaphyseal section of the shaft part. In the present prosthesis, this eccentricity can be set between d minus d 'and d plus d'. This adjustability of the head cap is desirable, but it cannot be used in practice. In order for the second eccentric to be set correctly, the first eccentric must already be set correctly. In practice, however, it is impossible for the surgeon to determine during an operation how to adjust the inner eccentric so that the outer eccentric can be adjusted correctly. However, it is also impossible to clarify how the eccentrics must be in relation to each other before the operation, because this depends on the exact placement of the shaft part in the humerus.

For implanting the shaft part and aligning the axis of the hemispherical recess approximately perpendicular to the cut surface on the humeral head, the above-mentioned document suggests a complicated implantation instrument. This ensures that the shaft part is offset with maximum deviations from the ideal position with respect to the direction of the axis of the hemispherical recess, which maximum deviation lies within a tolerance range within which the deviations can be compensated for with the humeral plate. The humeral plate is placed on the implanted shaft part.

A test head is provided for setting the two eccentrics. The

Test head, which has an outer edge and an eccentric conical bore with respect to this, can be placed on the eccentric cone of the humeral plate. The conical bore is continuous, so that the humeral plate is accessible through the conical bore and can therefore be rotated with respect to both the shaft part and the test head. The ideal position of the humeral plate and the head can be approximated by trial and error by twisting the humeral plate and trial head against each other and in relation to the shaft part.

It is an object of the invention to provide the surgeon with an endoprosthesis and aids that are matched to the endoprosthesis allow for an endoprosthesis for the replacement of a shoulder joint with a double eccentric to immediately and precisely determine the optimal position of the eccentric to be set first with respect to the shaft part.

According to the invention, this object is achieved in an endoprosthesis mentioned at the outset by the characterizing features of claim 1. This solution is independent of the design of the endoprosthesis with regard to the adjustability of the direction of the neck axis or the head axis.

The invention is based on the knowledge that the first eccentric in an optimal position should have a minimum distance from the circle defined by the bone cutting edge, which corresponds to the smallest distance between the eccentric in the joint head of the prosthesis and the edge of its base. Since the radius of the base is matched to the radius of the circle defined by the bone cutting edge, the smallest distance between the first eccentric and this circle and the smallest distance between the second eccentric and the edge of the base of the joint head must correspond. When the first eccentric is in a position in which this distance is maintained, the joint head can be pivoted about the eccentric axis into the optimal rotational position.

To put it simply, the base of the joint head has the same radius as the bone edge of the bone interface, which radius is referred to as R2. A rotationally symmetrical shape on a neck part of an endoprosthesis forms a first eccentric that fits into a counter shape on the joint head. The counter-shape and the shape have the same radius, although it is advantageous to have a conical shape. This radius is referred to as R1. The eccentricity of the center of the radius Rl to the center of the radius R2 is denoted by Dl. The smallest distance mentioned between the counterform and the edge of the base is referred to below as AI. An annular adjustment template for adjusting a first eccentric has an annular width AI and advantageously an outer radius R2. The ring width corresponds to the difference between the radius (Dl + Rl) of an envelope curve of a second eccentric to be set later around the eccentric axis of rotation of this second eccentric and the radius R2 of the base of the

Condyle. With the help of this setting template, the circumferential circle of the first eccentric can be brought into a minimal distance from the edge of the bone cut surface, which corresponds to this distance AI. If this first eccentric is aligned in this way, the second eccentric can be placed on the first eccentric in such a way that the head axis of the joint head, which can be defined by the second eccentric, is concentric with the bone cutting surface.

In order to set the first eccentric, this setting template with the ring width AI and the radius R2 of the circumference can be placed around the first eccentric. It is brought into line with the bone cutting line or in a desired position with respect to the bone cutting line. Now the eccentric must be rotated about its eccentric axis of rotation until its circumference touches the setting template on its inner opening edge. The setting template now affects the circumference of the eccentric at one point, which is at a point on the same radius but on the outer side of the ring

Adjustment template on the edge of the bone cutting surface. Regardless of the shape and position of the bone cutting edge, the outer circumference of the setting template can lie in a desired position with respect to the bone cutting edge, so it should ideally be arranged in a covering manner.

There are two optimal positions of the first eccentric. One is achieved by turning the eccentric clockwise, the other by turning the eccentric counterclockwise. In both positions, the edge of the eccentric is at a minimum distance AI from the (idealized) edge of the bone interface. This distance AI corresponds to the distance of the The circumference of the second eccentric in the base of the condyle from the edge of the base of the condyle.

The setting template can also be smaller or larger than the idealized circle of the bone cut surface. Then the outer circumference must touch the edge of the bone cut surfaces at the point with the smallest distance AI. However, the outer peripheral edge of the setting template advantageously has the same radius as the base of the joint head. Then the outer circumference of the setting template must be aligned with the ideal circular line of the edge of the bone cutting surface. It is therefore possible for the operator to hold the setting template in an optimal position with two fingers even with an irregular edge of the bone cut surface. This position should also correspond to the optimal position of the joint head. This allows the best position of the first eccentric to be aligned with the optimal position of the joint head to be achieved.

In principle, however, it is also possible to choose the inner opening radius of the setting template in accordance with the radius of the circumferential circle of the first eccentric. Such an adjustment template can also be formed in one piece with the first eccentric. Its outer peripheral edge only needs to be positioned tangentially at one point. Then the first eccentric is already in one of the two optimal positions.

To set the first eccentric, an annular setting template is accordingly placed on the bone cut surface and the neck part is rotated about the neck axis relative to the implanted shaft part until the neck part is at a position closest to the bone cutting edge at a distance defined by the setting template. Then the position of the neck part can be fixed and the joint head can be put on. By turning the joint head around the neck part, its optimal position can be found immediately become. In this position, the edge of the base is parallel to a circle defined by the edge of the bone cut.

The setting template is advantageously a part that is separate from the endoprosthesis that replaces the joint and is therefore reusable. It is therefore only placed on the bone cutting surface for setting the first eccentric and held in a position to be achieved for the base of the joint head. This can be done with two fingers that grip both the edge of the bone and the setting template. The position can be felt by simultaneously touching the bone and the adjustment template. It can also be determined immediately whether the base size matches the cut surface size and, if necessary, a different joint head set is selected.

In this case, each joint head set with a uniform base radius necessarily has an adjustment template with the same radius. For all rod ends of a set, the smallest distance between the shape for receiving the neck part and the edge of the base is expediently identical.

The setting template is expediently rotationally symmetrical. It advantageously has a uniform thickness in the direction of its axis of symmetry, which corresponds to at least a maximum permissible distance of a cranial surface of the neck part from a plane of the bone section. This makes it possible to determine immediately if the neck part protrudes too far beyond the bone cutting surface. With an adjusting key, the neck part can now be brought into a position touching the inner opening edge surface of the setting template. If the adjustment key rests on the adjustment template, the adjustment key can also be used to align the neck axis normally to the bone cutting surface or to the desired position of the base of the joint head. For this purpose, contact surfaces are formed on the neck part for interaction with an adjusting key. The adjustment key in turn is designed with a shape corresponding to the contact surfaces. Formation and contact surfaces interact when the first eccentric is rotated around the neck axis. In addition, the adjustment key advantageously has a support surface for resting on the setting template. This contact surface is in a position of the adjustment key, in which the engagement surfaces and the formations on the adjustment key interact, perpendicular to the neck axis of the neck part.

In order to replace a

An adjustment tool is required to adjust the shape of the shoulder joint optimally (this is the first eccentric). According to the invention, this adjustment tool has an annular adjustment template which has an outer edge with a radius R4 and an inner edge which is concentric with the outer edge and has a radius R3, the following equation being valid: R4 - R3 = R2 - (Dl + Rl). In this equation, R 2 stands for the radius of the bone cutting surface, Rl for the radius of the second eccentric and Dl for the distance of the eccentric axis of the second eccentric from the head axis of the joint head. In a preferred embodiment, R4 is R2.

The setting template is expediently rotationally symmetrical. It advantageously has a constant thickness in the direction of its axis of symmetry, which preferably has at least a maximum permissible distance of a cranial surface of the neck part from a plane of the bone section. However, it can also be made thinner.

An adjustment key for turning the neck part around the neck axis is advantageously available. The adjustment key advantageously has a bearing surface for resting on the setting template. If the setting template is thicker than the maximum permissible distance between the cranial surface of the formation on the neck part and the bone cut surface, the contact surface can be adjusted using the Place the formation on the setting template. However, if the distance between the surface lying on the bone cut surface and the cranial surface opposite it is smaller than the distance between the cranial surface of the formation on the neck part and the bone cut surface in the setting template, then there must be a recess in the support surface of the adjustment key into which the shape may protrude from the neck part.

A measuring device is advantageously formed on the adjustment key. With the measuring device, the distance of the cranial surface of the

Adjustment template to the cranial surface of the neck part to be adjusted can be measured. Due to this distance and the thickness of the setting template, the joint head to be selected can be concluded from a set of joint heads. This measured distance can therefore be assigned directly to a specific joint head thanks to the thickness of the setting template belonging to a set of joint heads.

In the case of a tool set matched to a rod end set, there are therefore several setting templates, each with a radius matched to the respective outer radius of the base of the rod ends. The thickness of this

Setting templates are advantageously always the same, so that the adjustment key can be the same for all rod ends of the set. The adjustment key has a measuring device from which the joint head height to be selected can be read directly.

The invention is explained in more detail below on the basis of schematic sketches. It shows:

1 shows a humeral head without the removed natural joint head, the shaft part, neck part inserted into the humerus, an eccentric ring and an artificial joint head, Figure 2 shows a joint head in which a recess for receiving the

3 is a schematic drawing of the geometry of an adjustment template,

Figure 4 is a schematic drawing to illustrate the geometry and the setting of the first eccentric by means of an inventive

Adjustment template, Figure 5 is a schematic drawing to illustrate the setting of the eccentric with an adjustment template with an outer radius which is smaller than the radius of the bone cutting surface, Figure 6 a humeral head as in Figure 1, but with the

Bone cut surface placed on the template, Figure 7 an adjustment key to interact with a first

Eccentric according to FIG. 6, FIG. 8 shows a schematic section through the humeral head with the adjustment template placed on the bone cut surface, with the first

Eccentric interacting adjustment key and the

9, the same section as in FIG. 8, but with an adjustment template shaped according to a head cap.

In the humeral head shown in Figure 1, the natural articular surface is separated and not shown. The bone cut surface 11 is visible. Material was removed from the bone 13 and a shaft part 15 with bone cement 17 was inserted into the humerus bone 13. When the shaft part is implanted, the head 19 of the shaft part 15 comes more or less centrally into the approximately circular bone cutting surface 11. In the head 19 there is a recess 21 in which a neck part 23 can be articulated. The neck part 23 is shown detached from the sheep part 15. The neck part 23 has a convex spherical surface 25 for articulation in the pit 21. The neck part 23 also has a surface to be arranged above the bone cut surface 11 Cone 27 on. The axis of rotation of the cone 27 is called the eccentric axis 29 and is parallel to a neck axis 31 through the center of the spherical surface 25. A fastening screw 33 is arranged approximately on the neck axis, with which the neck part 23 can be fixed in the pit 21. The neck axis 23 can be directed thanks to the ball joint between the shaft part 15 and the neck part 23, while the direction of the fastening screw 33 is determined by the shaft part 15 and the threaded hole 35 worked out therein, into which threaded hole 35 the fastening screw 33 is screwed.

The cone 27 can therefore be rotated eccentrically about the neck axis 31 and can be pivoted about the center of the sphere surface 25. Thus, its cranial surface 37 can be directed parallel to the bone cutting surface 11 and its rotational position can be selected such that it is possible to place the joint head 39 centrally on the bone cutting surface 11. 1 shows a second eccentric 41 which mediates between a spherical cap 40 and the neck part 23. The receiving recess 45 in the spherical cap 40 is therefore designed to be rotationally symmetrical about the head axis 43. In FIG. 2, on the other hand, the joint head 39 is provided with an eccentric counter-shape 47 for cooperation with the cone 27 on the neck part 23. The second eccentric 41 is integrated in the joint head 39 in FIG. In Figure 1, the counter shape 47 is formed in the second eccentric 41. The second eccentric 41 and the spherical cap 40 therefore together form a joint head 39 with an eccentric counter-shape 47 to the cone 27.

In the base of the receiving recess 45 in the spherical cap 40, this has a radius R5 which is of course smaller than the radius R2 of the base 49 of the spherical cap 40 or the joint head 39. The radius R5 corresponds to the outer radius of the second eccentric, which is therefore also with R5 is denoted, it being neglected that the radii must not correspond exactly to one another so that clamping can be achieved between the second eccentric and the spherical cap 40. This radius R2 at the base 49 of the joint head 39 corresponds to the radius R2 of the

Bone cutting surface 11. These two identically designated radii should ideally match. Of course, the bone cutting surface 11 is not exactly circular. However, the head axis 43 of an ideally placed joint head 39 intersects the circular center 40 of the bone cutting surface 11 or the bone cutting edge 51.

Corresponding radii R1 are present on the counterform 47 and on the cone 27. Rl denotes the largest radius of the two conical shapes. This is also a simplification, since the largest radii of the two conical forms of rotation do not necessarily have to be identical. However, there must be corresponding radii on both interacting surfaces.

In fact, the joint head can now be optimally centered whenever a circumferential circle with the radius Rl of the cone 27 has a smallest distance AI from the bone cutting edge 51, which is the smallest distance AI of the circle with a radius Rl of the counterform 47 in the joint head 39 from the edge 53 of the base 49 has. This smallest distance AI can be read directly from FIG. 2. In FIG. 1, however, it is composed of the thickness of the thinnest cross section of the second eccentric 41 and the width of the annular base surface at its narrowest point.

In FIG. 2, the envelope curve 50 of the circle of the counterform 47 with the radius R 1 is also shown with a broken line when this circle rotates around the head axis 43. This envelope curve 50 has a distance AI to the edge 53 of the base 49 everywhere.

The distance between the circle with the radius Rl of the cone and the bone cutting edge 51 with the radius R2 can be set according to the distance AI. FIG. 3 shows an illustration for explaining this connection briefly mentioned above. The cone 27 must fit into the counterform 47 provided for this purpose in the joint head 39. The counter shape 47 or the cone 27 is represented by a circular area. Both are rotatable about the neck axis 31. The head axis 43 is arranged parallel to the eccentric axis 29, namely at a distance Dl. This distance is given by the counter-shape 47 in the joint head. The head axis 43 must cut the bone cutting surface 11 centrally with the optimal position of the joint head 39. The bone cutting edge 51 is therefore at a distance R2 from the head axis.

If the counterform 47 is rotated around the head axis 43, it describes a circular envelope curve 50 with the radius R6. This envelope curve 50 and the bone cutting edge 51 must be concentric, since the head axis 43 must be centered on the bone cutting surface edge 51. The distance between the envelope 50 with the radius R6 and the bone cutting edge 51 or

Base edge 53 with the radius R2 corresponds to the smallest distance AI between the counterform 47 and the base edge 53. Therefore AI = R2 - R6 applies. But AI = R2 - (Rl + Dl) also applies, since Dl + Rl = R6. In order to align the base edge 53 with the bone cutting edge 51, it is necessary for the cone 27 to be in a position in which its smallest distance from the bone cutting edge 51 is AI. With an adjustment template 55 with a ring width of AI, this distance can be specified and the cone can be brought into a position in which the adjustment template 55 touches the cone 27 with an inner radius R3 and the bone cutting edge 51 with an outer radius R4.

If an adjustment template 55 is now used, the outer radius of which is denoted by R4 and the inner radius of which is denoted by R3, the difference R4-R3 must also result in AI so that the smallest distance AI of the cone 27 to the bone cutting edge 51 can be adjusted using this template. The following generally applies: R4 - R3 = AI = R2 - (Rl + Dl). In Figures 3 and 4, R2 = R4 and R6 = R3. If this is the most sensible version, it does not necessarily have to be that way. A smaller radius can also be selected for R4. It is essential that the ring width is AI.

FIG. 4 shows a schematic plan view of a humerus head with a separated spherical cap and a bone cut edge 51 with a radius R2. The outer circumferential circle 74 of an annular adjustment template 55 is arranged to cover the bone cutting edge 51. The setting template 55 has a ring width of AI, an outer circle radius R4 of length R2, an inner circle radius R3 of length R6. The radius of the cone Rl. In addition, the distance D2 of the eccentric axis 29 from the neck axis 31 is ideally equal to R3 minus Rl. This means that ideally Dl is equal to D2. This allows the neck axis 31 to be placed exactly in the center of the circular line of the bone cutting edge 51. In this case, the cone 27 can be rotated about the neck axis 31, the smallest distance between the bone cutting edge 51 and the cone 27 corresponding to the distance AI in each position. Therefore, the joint head 39 can be placed in any position of the cone and the base edge 53 can be brought into register with the bone cutting edge 51. If, however, as shown in FIG. 4, the neck axis 31 is not arranged centrally, the cone 27 can be rotated about the neck axis 31 and has the desired distance AI from the bone cutting edge 51 in exactly two positions. These positions are shown with broken lines and with the numbers 57 and 59.

As already mentioned, this setting template with the radius R4 = R2 is merely a preferred embodiment of the setting template 55. In FIG. 5, therefore, an adjusting template 55 is shown with an inner edge 73 on a radius R3 which corresponds to the radius R1 of the cone 27. This setting template 55 can be part of the cone 27 and remain on the cone, or can only be attached to the cone for setting the cone 27. The cone is rotated with the adjustment template 55 around it around the neck axis 31 until the outer edge 74 of the setting template 55 touches the bone cutting edge 51. This is again the case in exactly two positions, namely in positions 57 and 59.

FIG. 6 shows a perspective view of a humeral head with an adjustment template 55 and a cone 27. The shaft part 15 is implanted in the humerus bone 13. The neck part 23 is inserted into the pit 21 and provisionally fixed with the screw 33. The setting template 55 was then placed on the bone cutting surface 11. Now the cone surface 37 can be directed parallel to the cranial, flat and annular surface of the setting template 55. The eccentric axis 29 is thus directed parallel to the optimal head axis 43. In order to obtain the optimal distance between the axis of rotation of the setting template 55 and the eccentric axis 29, the cone 27 is rotated about the neck axis 31 until the cone surface of the cone 27 is in contact with the inside of the setting template 55. There are two directions of rotation (compare the double arrows shown in FIGS. 4 and 5). Each direction of rotation leads to one of the two positions 57 and 59 of the cone 27, in which the smallest distance between the cone and the bone cutting edge 51 corresponds to AI. In this position, the neck part 23 is now fixed in the shaft part 15, and then the adjustment template 55 can be removed. In these positions 57 and 59, the joint head 39 can be placed on the cone 27 and rotated on the cone 27 about the eccentric axis 29 until the head axis 43 intersects the circular center 40 of the bone cutting edge 51 and the base edge 53 runs parallel to the bone cutting edge 51.

Two bores 61 are provided in the cone 27, in which an instrument for rotating and straightening the cone 27 can engage. Such an instrument is shown in FIG. This adjustment key 63 has a flat contact surface 65 on its underside. With the mounting surface 65, the adjustment key can be placed on the surface of the setting template 55. Under the

The contact surface 65 projects downwards from two bolts 67 which engage the bores 61 are matched in the cone. Distance markings 68 are attached to the bolts 67, at which the distance of the cranial surface 37 of the cone 27 from the cranial surface of the setting template 55 can be read. A rotary handle 69 is formed on the top of the adjustment key 63. An opening 71 is formed in the contact surface 65. The opening 71 allows the

Access to the fastening screw 33, the head of which is in the neck part 23. The position of the cone 27 can be set very easily with the adjustment key 63 and the setting template 55.

To explain the use of the adjustment key is a in Figure 8

Sectional drawing through the humerus head with attached setting template 55 and cone 27 to be straightened with the adjusting key 63. The setting template 55 is placed on the bone interface 11. With thumb 83 and index finger 85 and / or middle finger, the setting template 55 is held centrally on the bone interface 11, the correct position with the

Touched fingertips and can therefore be checked continuously. The bolts 67 are inserted into the bores 61. The contact surface 65 lies flat on the setting template 55. Since the surface of the setting template 55 is directed parallel to the bone cutting surface 11, the cone 27 or the eccentric axis 29 is directed perpendicular to the bone cutting surface 11. By turning the adjustment key 63, the cone 27 can be brought into a position touching the setting template 55. Since the cone 27 has a conical circumferential wall, but the inside 73 of the setting template 55 is directed perpendicular to the bone interface 11, the cone touches this inside 73 only at one point on a circle with the largest radius R1 of the cone.

The distance between the surface of the cone and the surface of the template can be used to determine which joint head fits best on the cone 27. If necessary, this distance can also be set. Markings 68 are provided on the bolts 67 for simple measurement of this distance. In FIG. 7, the markings on the two bolts 67 are each offset by half a marking distance, so that the labeling and reading of the markings are easier. In the example shown in FIG. 8, the setting template 55 is higher than the cone. A suitable design of the adjustment key 63 can, however, deviate from this and the adjustment template 55 can be designed with a lower height.

FIG. 9 shows an advantageous embodiment of the setting template 55. The setting template 55 has a spherical surface and an outer circumference 74, which has a rounded edge corresponding to a calotte. The rounded edge creates a smooth transition between a base surface and the spherical surface. As a result of this design, the surgeon can already use the setting template 55 to precisely determine how the calotte placed on the eccentric will later be arranged to the bone edge 51.

Furthermore, on this advantageous setting template 55, the inner surface 73, which is to be brought into contact with the conical shape of the first eccentric 27, has its cone angle correspondingly conical. This allows a linear contact between the first eccentric 27 and the adjustment template 55. These two features can be implemented independently of one another on an adjustment template 55.

Accordingly, the cone 27 of a shoulder joint prosthesis, which is designed as a first eccentric, can be adjusted with an annular adjustment template 55 in such a way that a joint head 39, designed as a second eccentric, can be placed on the first eccentric 27 such that the head axis 43 is the center of the. circular bone cutting surface 11 cuts. For this purpose, the circular ring of the setting template 55 only has to have the width AI which corresponds to the smallest distance of the eccentric counterform 47 in the joint head 39 from the base edge 53 of the joint head 39.

Claims

claims:

Endoprosthesis for the replacement of a shoulder joint, with

- a shaft part (15) for fastening in an upper arm bone (13),

- a neck part (23) which is rotatable about a neck axis (31) on the shaft part (15) and which neck part (23) has a shape (27) which is rotationally symmetrical with respect to an eccentric sleeve (29) spaced apart from the neck axis (31),

- an articulated head (39), which articulated head (39) has a circular base (49), a counter-shape (47) rotationally symmetrical about the eccentric axis (29) for interacting with the shape (27) on the neck part (23) and opposite the base (49 ) has a practically rotationally symmetrical articulation surface with respect to a head axis (43) spaced apart from the eccentric axis (29) for interaction with the articulation surface of a natural or artificial glenoid,

- and if necessary an artificial glenoid,

- In which endoprosthesis the eccentric axis (29) has a distance Dl from the head axis, the shape (27) on the neck part (23) or the counterform (47) on the joint head (39) has a radius R1 and the base (49) of the joint head (39) has a radius R2 corresponding to a bone cut surface (11), characterized by an annular adjustment template (55), which adjustment template (55) has an outer edge (74) with a radius R4 and an inner edge (74) concentric with the outer edge has a radius R3, where the following equation applies:

- R4 - R3 = R2 - (Dl + Rl)

Endoprosthesis according to claim 1, characterized in that R4 = R2 or R3 = Dl + Rl applies.

3. Endoprosthesis according to claim 1, characterized in that R3 = Rl or R4 = R2 - Dl applies.

4. Endoprosthesis according to claim 3, characterized in that the adjustment template (55) is formed on the neck part (23).

5. Endoprosthesis according to one of claims 1 to 3, characterized in that the setting template (55) is a separate part from the joint replacing endoprosthesis and is therefore reusable.

6. Endoprosthesis according to claim 5, characterized in that the setting template (55) is rotationally symmetrical and has a thickness in the direction of its axis of symmetry which is at least a maximum permissible distance of a cranial surface (37) of the neck part (23) from a bone cutting plane (11) having.

7. Endoprosthesis according to claim 5 or 6, characterized by engagement surfaces (61) on the neck part (23) for interacting with an adjustment key (63) and an adjustment key (63) with a shape (67) corresponding to the engagement surfaces (67) for interacting with the contact surfaces (61), turning the first eccentric (27) around the neck axis (31).

8. Endoprosthesis according to claim 7 and 6, characterized in that the adjustment key (63) has a support surface (65) for resting on the setting template (55), which support surface (65) in a position of the adjustment key (63) in which the Interacting surfaces (61) and the formations (67) on the adjustment key (63) interact perpendicular to the neck axis (31) of the neck part (23).

9. Adjustment tool for an endoprosthesis according to one of the preceding claims, characterized by an annular adjustment template (55), which adjustment template (55) has an outer edge (74) with a radius R4 and an inner edge (73) concentric with the outer edge (74). with a radius R3, where the following equation applies:

R4 - R3 = R2 - (Dl + Rl) and

R2 is the radius of a base of a joint head of an endoprosthesis and D1 is the distance between an eccentric axis of rotation of a first eccentric and the axis of rotation of a second eccentric of an endoprosthesis which can be rotated about the first eccentric.

10. Adjusting tool according to claim 9, characterized in that the adjusting template (55) is rotationally symmetrical and has a thickness in the direction of its axis of symmetry which is at least a maximum permissible distance of a cranial surface (37) of a neck part (23) of an endoprosthesis from a bone cutting plane ( 11).

11. Adjusting tool according to one of claims 9 or 10, characterized in that an adjusting key (63) for rotating the neck part (23) around the neck axis (31) is present, which adjusting key (63) has a bearing surface (65) for resting on the adjusting template (55).

12. Adjusting tool according to claim 11, characterized in that a measuring device (67) is formed on the adjusting key (63) for measuring the distance from the cranial surface of the adjusting template (55) to a cranial surface (37) of a neck part (23) to be adjusted endoprosthesis.

13. A method for adjusting the position of a head axis (43) with respect to a bone cut surface (11) in an endoprosthesis for the replacement of a shoulder joint - a sheep part (15) for fastening in an upper arm bone (13),

a neck part (23) which can be rotated about a neck axis (31) on the shaft part (15) and which neck part (23) has a shape (27) which is rotationally symmetrical with respect to an eccentric axis (29) spaced from the neck axis,

- an articulated head (39), which articulated head (39) has a circular base (49) with a symmetrical counter-shape (47) about the eccentric axis (29) for interacting with the shape (27) on the neck part (23) and opposite the base (49 ) has a practically rotationally symmetrical articulation surface with respect to a head axis (43) spaced apart from the eccentric axis (29) for interaction with the articulation surface of a natural or artificial glenoid,

- In which endoprosthesis the eccentric axis (29) has a distance Dl from the head axis (43), the shape (27) on the neck part (23) or the counterform (47) on the joint head (39) has a radius R1 and the base (49 ) of the joint head (39) has a radius R2 corresponding to a bone cut edge (51), characterized in that an annular adjustment template (55) is placed on the bone cut surface (11) and the neck part (23) with respect to the implanted shaft part (15) Neck axis (31) is rotated until the neck part (23) is at a position AI closest to the edge of the bone cut surface (51) at a distance defined by the setting template (55).