DE10123517C1 - Shoulder endoprosthesis has a joint connection formed by a protrusion on a middle part clamped by a clamping element from the proximal end of the middle part in a recess in the proximal end of a shaft - Google Patents

Abstract

Shoulder endoprosthesis comprises a shaft, a middle part (20) fixed to the shaft by a joint connection having at least two degrees of rotational freedom, and a head cap (40) fixed to the middle part. The joint connection is formed by a protrusion (23) on the middle part clamped by a clamping element (30) from the proximal end of the middle part in a recess (14) in the proximal end of the shaft. The protrusion is pin-shaped. The recess has two angled clamping surfaces (16, 17) at the proximal end of the shaft between which the protrusion is spread by the clamping element. Preferred Features: The clamping surfaces are truncated conical surfaces.

Description

The invention relates to a shoulder endoprosthesis with a Shaft, with a middle part, which by means of an articulation binding that has at least two degrees of freedom the shaft is attachable, and with an articulated head on the middle part is attachable. The articulation will formed in that the middle part has a rotational sym has metric approach that in a recess on proximal end of the shaft is clamped. Tightening the middle part at the shaft end is done by screwing a threaded bolt from the proximal end of the middle part.

State of the art

The replacement of diseased or accidentally damaged joints has been part of everyday accident practice for many years surgery and orthopedics. In addition to artificial hip and knee For some years now, the replacement of injured people has been steering Shoulder joints applied with success.  

The requirements for artificial joints arise from their mechanical load that occurs as an alternating load and over must be endured for many years, as well as from the milieu flows, which the materials used permanently resist have to stand.

Special problems that apply to the entire joint endo prosthetics result, are the respective individual anatomi conditions to which the artificial joint is adapted must be to the biomechani present in the healthy joint and kinematic relationships in the artificial joint to restore at least approximately. At the shoulder joint the circumstances are particularly complicated since the shoulder joint has an extraordinarily large range of motion, which Articular socket (glenoid) however only a small part of the Joint head covered.

Depending on the individual conditions, ver different sizes and constructions of artificial joints manufactured to meet every possible application to be able to.

From EP-A-0 715 836 a shoulder prosthesis is known which using one attached to the proximal end of the humeral shaft ball and a spherical recess in the joint head a setting with three free rotations to hold the ball degrees. The axis of the condyle is offset from the center of the sphere by an additional one enable medial and dorsal offset of the humeral head. The joint head and ball are fixed from the lateral and distal to the resection plane, which is an extraoperative one Positioning and fixation using a trial implant and setting device direction required.

DE-A-195 09 037 describes a shoulder prosthesis in which the three-dimensional adjustability over two separate Joint mechanisms is realized. The setting of the Retrotorsion is attached to a central part  Ball and a seat in the shaft for jamming the ball realized. The inclination is over another joint adjusted by means of separate fixation. The double ezen trical adjustment of the medial and dorsal offset is possible. The separate setting of the parameters mentioned takes place by means of two fixing elements and a manipulation Middle part.

From WO 99/34756 is a shoulder prosthesis at the beginning known type, which is also a three-dimensional Attitude as well as having a double eccentricity. The Recess at the proximal end of the shaft and the approach on The middle section is hemispherical. The middle section has one axial recess starting from the proximal end with a hemispherical bottom and a conical hole in the bottom. The Recess at the end of the shaft has a central threaded hole and by means of one inserted into the recess in the middle part Ball stud is the middle part at the proximal end of the Shaft clamped. Due to the hemispherical shape of the outer and inside of the bottom of the middle part and the bottom the head of the spherical collar bolt, the middle part can be opposite be aligned with the shaft. The scope of the setting is due to the excess of the conical bore compared to the Stud diameter determined. The setting and fixation of proximally, intraoperative surgery and head revision is possible possible without simultaneous shaft revision.

Basic principle of the invention

The object of the invention is a shoulder endo prosthesis, in which the individual elements are reliable are connected so that there is no risk of loosening of connections or jiggles.

According to the invention, this goal is achieved in that the Approach of the middle part is cone-shaped and that the off opposite at the proximal end of the shaft  has inclined surfaces between which the cone-shaped Approach can be clamped by means of a clamping element.

Under "cone-shaped approach" an approach is ver stood, the diameter of which starts from the central part first enlarged and then reduced, the surface overall smooth and at least in the area of the largest through knife without edges. It is preferably cone-shaped Approach rotationally symmetrical. He can e.g. B. have spherical shape or be a constant.

"Oppositely inclined surfaces" means that the recess first widens and then narrows. The oppositely inclined surfaces touch the cone approach of the middle part to relatively far from each other distant points, which is a safe and wobble-free ver bond results. This design of the recess is one secure support and fixation of the cone-shaped attachment guaranteed at least three points.

The inclined surfaces can be opposite conical. she can also be flat and each have a multi-sided pyramid span. However, they are preferably frustoconical surfaces and the approach of the middle part is spherical, so that between the conical surfaces and the approach of the middle part lines touch exists. The surface pressure at the points of contact is reduced.

The approach is in a particularly preferred embodiment of the middle part is not spherical, but has an axial one cut the shape of a constant thick. The distance of the Kreisli no line contact between the neck and the double cones The surface of the recess becomes larger, so that the Bracing the middle part in the recess of the shaft can absorb high moments even with a small size. This can also be achieved by making the approach a double is torus and then in the axial section the shape of a rectangle with rounded corners.  

The middle part has a main section, a disc and the approach. The approach is generally about one short neck section with the main section and the flat one Disk connected. In the embodiment in which the approach has the shape of a constant thickness in axial section is preferred on the side of the approach of the Radius of curvature up to 50% larger than that of the main part cut away side. This creates an additional free Degree of optimization to optimize the cross-sections and cross-section transitions created according to the load profile.

The middle part and its attachment preferably have a continuous, central hole located at the distal end of the approach narrows or widens and is the approach by means of a clamping element, the tip of which is corresponding tapered or expanded, expandable and therefore in the Recess can be tightened at the proximal end of the shaft. The conical Tapering or widening at the distal end of the tensioning element tes can also be slightly spherical. For example can be the surface of a spherical segment act.

The clamping element is expediently a threaded bolt and has the continuous, central bore of the middle part and the Approach a threaded section so that the threaded bolt is in this hole can be screwed in. If the central Hole is narrowed towards the distal end of the attachment, so the threaded bolt from the proximal end of the middle section screwed. If the hole at the distal end of the Approach, on the other hand, is expanded, so the threaded bolt is from distal end of the middle part screwed in.

This structure allows the middle section to be adjusted at least two and usually around the shaft three axes of rotation. In addition, the middle part is opposite fix the stem proximally through the middle section bar. This gives the surgeon the option, even after the Insert the shaft, the middle part and the spherical cap  exchange without removing the shaft got to. Furthermore, the revision of the joint head is without the inevitable revision of the shaft possible.

The clamping force introduced by the threaded bolt is over reinforces the cone at the top of the threaded bolt so that not only the result of the tightening torque of the screw axial force causes the bracing. The recordable Moments are very big. For the safe and durable The design of the components does not require large volumes, which is anatomically advantageous. The flow of tension is independent of the flow of force transmission through the Implant. The movement of the shoulder joint Forces and torques that occur cannot loosening the tension of the middle part on the shaft to lead.

The threaded bolt of the tensioning element is preferably second egg lig formed by the conical tip opposite the Main part of the bolt is rotatable. This means that when Screwing in the threaded bolt only from the axial tightening moment resulting force are applied. The top will only pushed axially to spread the approach, needs but not to be turned. That for screwing in the thread Bolt required torque is essential less and the tension of the middle part in the recess the shaft can be reinforced.

Such a two-part design of the clamping element can, for. B. can be realized in that at the distal end of the Threaded bolt a rotatable sleeve is provided, the one has conical outer surface and by means of a locking ring on Threaded bolt is held. This configuration is ins especially useful if the central hole on the distal end of the approach expands and the threaded bolt consequently screwed in from the distal end.  

In the embodiment in which the central bore of the There is also a narrow middle section at the distal end of the approach the possibility of a from the proximal end of the hole Insert ball into the constriction within the neck and then advance this ball by means of the threaded bolt Approach to spread out and the middle part in the out Tension on the proximal end of the shaft. The Use a ball to spread the segments of the tenon shaped approach is advantageous because even with a relatively small Opening angle no self-locking clamping occurs, so that it is generally sufficient to unscrew the threaded bolt, to brace the middle part in the recess on to release the distal end of the shaft.

At the top of the middle part there can be a proximal Towards the tapered cone to accommodate the spherical cap be ordered. The axis of this cone can be compared to the Bore of the middle part must be offset. The axis can also opposite the cone formed in the joint head (calotte) the joint head axis be offset. This double eccentric Connection allows the setting of a medial and dorsal Offsets. The two dislocations are preferably the same. The The center of the calotte can then be at any point within a circular area whose radius is equal to that is double offset.

As already mentioned, the shoulder Endoprosthesis is a very compact design. This enables the distance between the calotte and the proximal end of the shaft is so small to keep using the center of the curvature of the calotte the center of the cone-shaped projection and the recess collapses at the proximal end of the shaft or only one very has a small distance from this center. As a result, the Calotte none or only when the shoulder joint moves very low tipping forces on the clamping connection with the shaft out. The forces exerted by the spherical cap are in primarily directed radially and go through the curvature  center of the spherical cap and therefore also through the Center of the approach or recess.

In the case of orthopedic use, only the spherical cap is used anatomical neck resected. With the implant according to the invention can all adjustment procedures after implantation of the Humeral shaft proximal to the resection level intraoperatively be performed. This protects the bone, shortening the operating time and simplifying the operating Technology achieved. Elaborate and faulty trial implant tate and adjustment devices are omitted and the instru mentarium can be reduced.

The middle part is only with after the shaft is hammered in this tense. The parameters that are particularly important for Orthopedic use are discontinued, are the inclina tion, retrotorsion and medial and dorsal offset of the humeral head. This is when the shaft is hammered in Middle part only inserted, but not yet braced. At the Drive the shaft into the prepared humerus the prosthesis with regard to inclination and retrotorsion automatically. By turning the middle section as well If necessary, the medial and the dorsal offset independently and steplessly turned on be put. By means of the instep inserted from proximal element, the middle part and the shaft can be temporary and be finally braced. The parts of the shoulder prosthesis can thus be connected by simple and secure elements and be replaced during the operation. Here are angular and positional relationships infinitely adjustable.

The shoulder endoprosthesis is preferably modular, d. H. the shafts have different diameters and However, lengths always have the same recesses and they have the same Middle parts each cone-shaped approaches of the same dimensions so that every shaft combines with every middle part can be. Due to the modular structure, shafts are in different lengths and diameters can be used are solid  and modular domes with different outer geometries can be used and can middle parts with different exterior geometries can be used.

Overall, the invention thus represents a shoulder endo prosthesis available from the stem, the middle part, the clamping element and the spherical cap. The connection of The shaft and middle section are infinitely variable in three dimensions Adjustment of inclination, retrotorsion as well as medial and dorsal offset adjustable. The connection between shaft and The middle section is able to absorb moments of rotation. The Adjustment of the implant in the dimensions mentioned takes place intraoperatively on the implanted stem.

The modular shoulder prosthesis is very great different anatomical conditions and different most indications.

When implanting it is advantageous that the endoprosthesis from a small number of parts of low complexity consists.

The shaft part, the middle part and the tensioning element can be made of Titanium or cobalt-chrome alloys and the rod end can made from a cobalt-chrome alloy or ceramic his.

The shaft part preferably has a proximal / lateral fin with holes for attaching tendons and possibly bone fragments.

An embodiment of the invention is described below the drawing explained. Show it:

Figure 1 shows the shoulder endoprosthesis in an exploded view from the side.

Figure 2 shows the spherical cap, the tensioning element, the middle part and the proximal end of the shaft of Figure 1 in an exploded, spatial presen- tation.

Fig. 3 shows the calotte bearing, the clamping element, the middle part and the proximal end of the shaft of Figure 1 in an exploded sectional view.

Fig. 4, the shoulder endoprosthesis of Figure 1 in the assembled state in section.

FIG. 5 shows a representation similar to that of FIG. 4, the calotte with the central part, however, being maximally tilted with respect to the shaft;

Fig. 6 shows the calotte bearing, the central part, the clamping element and the proximal end of the shaft in an exploded sectional view, wherein the clamping element is formed in two parts;

Fig. 7 shows the calotte bearing, the central part, the clamping element and the proximal end of the shaft of Figure 6 ung in an exploded spatial Visu.

Fig. 8 shows the endoprosthesis of Fig. 6 in the assembled state and

Fig. 9 shows the endoprosthesis of Fig. 6 in the assembled state with maximum tilt of the calotte towards the shaft.

The shoulder endoprosthesis shown in the drawing consists of a shaft 10 , a central part 20 , a tensioning element 30 and a calotte 40 .

The shaft 10 is composed of a straight shaft section 11 and a widening, proximal head section 12 , the head section 12 having a connecting surface 13 which extends at an angle of approximately 45 ° to the longitudinal axis of the shaft 10 and approximately corresponds to the resection plane. A recess 14 is provided in the connecting surface 13 , which has a circular opening edge 15 and two double-conical clamping surfaces 16 , 17 . From the opening edge 15 , the recess 14 widens in the first clamping surface 16 to its largest diameter and then narrows in the second clamping surface 17 again. A floor recess 18 is also connected to the second clamping surface 17 . The recess 14 has an overall rotationally symmetrical shape with an axis of rotation 19 .

The middle part 20 has a main section 21 , a flat disk 22 and a part-spherical projection 23 . The main section 21 of the middle part 20 lies on one side of the disk 22 and the shoulder 23 on the other side. Between the neck 23 and the disc 22 , a cut 42 is available. The central part 20 is overall rotationally symmetrical, the axis of the extension 23 being offset by an amount X of 2 to 10 mm with respect to the axis 29 of the main section 21 . The plane of the disk 22 is normal to both axes. A threaded bore 24 runs through the main section 21 in the center of the axis of the extension 23 , which continues into the extension 23 , but there has a smooth wall surface 25 that tapers at an angle of approximately 5 to 20 °. The extension 23 is segmented over its entire length by two intersecting slots 26 . Its distal tip is capped.

Proximally, ie from the side opposite the shoulder 23 , a clamping element 30 is used, which clamps the segments 27 of the shoulder 23 against the clamping surfaces 16 , 17 of the recess 14 at the proximal end of the shaft 10 ( FIG. 4). The clamping element 30 is a bolt, the front end 31 of which tapers in accordance with the wall surface 25 and the rear end 32 of which has a larger-diameter thread which engages in the threaded bore 24 . The threaded bolt 32 has an internal hexagon at its proximal end. The bolt is inserted with its front end 31 into the threaded bore 24 and can be pressed into the shoulder 23 by screwing in the thread, so that its segments 27 are spread apart and pressed against the clamping surfaces 16 , 17 .

The outside 28 of the main section 21 of the central part 20 tapers in the proximal direction at a cone angle of approximately 3 °. The dome 40 has a corresponding inner cone 41 , which can also be offset by approximately the amount X relative to the axis of rotation of the dome 40 . This offset cannot be seen in FIG. 3.

At the proximal end of the shaft 10 , a fin 44 with two bores 45 is provided on the side of the shaft 10 opposite the recess 14 . Tendons can be attached by means of these bores 45 . Likewise, the edge 22 of the middle part 20 can have bores 46 , to which tendons or bone parts can be attached.

Before the shoulder endoprosthesis is inserted, the middle part 20 is connected to the shaft 10 , the shoulder 23 being inserted into the recess 14 and being braced to such an extent that the middle part 20 cannot detach from the shaft 10 , but can still rotate with respect to the shaft 10 is adjustable. The tensioning element 30 is therefore not yet fully tightened. The shaft 10 is driven into the cavity of the humerus by means of a conventional shaft hammer until the disc 22 rests on the resection surface. Since the central part 20 has not yet been clamped, it can be aligned precisely with its disc 22 on the resection surface. Then when the final setting is found, the clamping element 30 is tightened and thereby the extension 23 spread, so that it is clamped in the recess 14 from. Between the segments 27 of the shoulder 23 and the clamping surfaces 16 and 17 of the recess 14 there is essentially line contact in the area of the largest diameter of the shoulder 23 , so that a secure and stable bracing is achieved. Any torques that may occur later when the shoulder joint moves between the calotte 40 , the central part 20 and the shaft 10 are not transmitted to the tensioning element 30 , so that there is no risk that the tension will loosen even under unfavorable conditions.

After tightening the clamping element 30 , the spherical cap 40 is placed on the middle part 20 . The assembled and fixed endoprosthesis is shown in FIG. 4, the axis of rotation 19 of the recess 14 coinciding with the axis 29 of the extension and the clamping element 30 . In Fig. 5, the assembled and fixed endoprosthesis with maximum tilt angle between the axis of rotation 19 of the recess 14 and the axis 29 of the projection 23 and the tensioning element 30 is shown.

In the embodiment of FIGS. 1 to 5, the clamping element 30 is inserted proximally into the central part 20 and screwed in, so that the front conical end 31 of the clamping element 30 is pressed into the extension 23 and expands it. FIGS. 6 to 9 show an embodiment in which the clamping element is distally inserted into the central member 20 and 30 screwed in. The clamping element 30 is designed as a threaded bolt with a threaded portion 33 in its middle, an external hexagon 34 at its proximal end and a smooth, cylindrical portion 35 at its distal end. A sleeve 36 with a conical outer side 37 is pushed onto the cylindrical section 35 and fixed by means of a locking ring 38 . The sleeve 36 can rotate on the cylindrical section 35 , but is secured against axial displacement by the locking ring 38 . The smooth wall surface 25 of the threaded bore 24 widens in the extension 23 towards the distal end and the conical outer side 37 of the sleeve 36 accordingly also widens towards the distal end. The threaded bore 24 in the central portion 20 opens at the proximal end in a school terbohrung 39 so that the external hex 34 is a Schrau can be placed benschlüssel without edge of the hexagon 34 protrude needs.

The clamping element 30 is inserted with the sleeve 36 attached to it from the distal end through the shoulder 23 into the middle part 20 and screwed into the threaded bore 24 with the threaded portion 33 . The sleeve 36 is drawn into the extension 23 and spreads it. In this embodiment, too, the tool (wrench) is attached to the proximal end of the clamping element in order to fix the alignment of the central part 20 . From the direction of the central part 20 and thus also the dome head 40 is thus possible when the shaft 10 is already inserted into the humerus. The finished, assembled endoprosthesis is shown in FIG. 8, with the cap 40 being in its central position, while in FIG. 9 it is tilted maximally with respect to the shaft 10 .

LIST OF REFERENCE NUMBERS

10

shaft

11

straight shaft section

12

header

13

interface

14

recess

15

opening edge

16

clamping surface

17

clamping surface

18

floor recess

19

axis of rotation

20

midsection

21

main section

22

disc

23

approach

24

threaded hole

25

wall surface

26

slots

27

segments

28

outside

29

Axis of approach

30

clamping element

31

front end

32

rear end

33

threaded portion

34

External hexagon

35

cylindrical section

36

shell

37

conical outside

38

circlip

39

counterbore

40

dome

41

inner cone

42

neck section

44

fin

45

drilling

46

drilling

Claims (4)

1. shoulder endoprosthesis with a shaft ( 10 ), with a central part ( 20 ) which can be fastened to the shaft ( 10 ) by means of an articulated connection which has at least two degrees of freedom of rotation, and with a spherical cap ( 40 ) which on the Middle part ( 20 ) can be fastened, the articulated connection being formed by an extension ( 23 ) of the middle part ( 20 ) and a recess ( 14 ) at the proximal end of the shaft ( 10 ), in which the extension ( 23 ) is formed by means of a tensioning element ( 30 ) can be tightened from the proximal end of the middle part ( 20 ), characterized in that
that the approach ( 23 ) of the central part ( 20 ) is cone-shaped and
that the recess ( 14 ) at the proximal end of the shaft ( 10 ) has two oppositely inclined surfaces ( 16 , 17 ), between which the peg-shaped extension ( 23 ) can be clamped by spreading it by means of the clamping element ( 30 ). 2. Endoprosthesis according to claim 1, wherein the clamping surfaces ( 16 , 17 ) are truncated cone surfaces. 3. Endoprosthesis according to claim 1 or 2, wherein the central part ( 20 ) and its extension ( 23 ) have a continuous, central bore ( 24 ) that narrows or widens at the distal end of the extension, and the clamping element ( 30 ) one has a correspondingly narrowing or expanding tip ( 31 ; 36 ) and can be screwed into the bore ( 24 ). 4. Endoprosthesis according to claim 1 or 2, wherein the central part ( 20 ) and its extension ( 23 ) have a continuous, central bore ( 24 ) which narrows or widens conically at the distal end of the extension, the tip ( 31 ) of the tensioning element ( 30 ) is designed as a surface of a spherical segment and the clamping element can be screwed into the bore ( 24 ).