DE10164328A1 - Shoulder joint prosthesis comprises a support element arranged on the acromium in the subacromial space and having a bearing surface above the head of the humerus to support the head of the humerus - Google Patents

Abstract

Shoulder joint prosthesis comprises a support element (21) arranged on the acromium (7) in the subacromial space (1) and having a bearing surface (23) above the head (3) of the humerus to support the head of the humerus. An Independent claim is also included for an alternative shoulder joint prosthesis. Preferred Features: The support element has devices (25) for fixing on the acromium, especially at least one anchoring element protruding toward the acromium for fixing in the acromium. The prosthesis also has a glenoid cavity element (19) for the head of the humerus on the shoulder blade side.

Description

The invention relates to a shoulder joint prosthesis.

The rotator cuff of the shoulder joint ensures that it is intact adequate rotation fixation of the humeral head in the socket on Neck of the shoulder blade (scapula). The shoulder blade overlaps with a in turn articulated to the clavicle Extension (acromion) the humeral head dorsally from above. On the acromion primarily used for the lateral lifting movement of the humerus responsible deltoid muscle that extends to the socket (glenoid) extends away along the upper arm. The subacromial space between the acromion and the humeral head is through with the shoulder joint intact the tendon of the supraspinatus muscle and a bursa (bursa subdeltoidea). Because of its location away from the socket The deltoid muscle exerts pivoting forces on the humeral head during contraction who try to tilt it eccentrically against the socket and pull him against the acromion. There are also strong ventrally and dorsally Muscles that also have a decentralizing effect on the Exercise humeral head. If the rotator cuff is intact, this acts Lever movements counter by turning the humeral head in a fixation point pulls in the socket. When implanting a The supraspinatus tendon falls over the humeral head prosthesis and, if applicable, an acetabular prosthesis and, if necessary, the bursa above it as a fulcrum Element of the shoulder joint often gone with the consequence of Subacrominial pinching and pain phenomena when lifting the arm.

In a first aspect, it is an object of the invention, the Specify shoulder joint prosthesis that improves pivot fixation.

Characteristic of a shoulder joint prosthesis according to the invention, the fulfilling this task is one in subacromial space Support to be arranged on the Acromion support element with a Support surface located essentially above the humeral head of the humeral head. The support element (subacromial prosthesis) takes over defective or missing supraspinatus tendon the initial Fixation of the humeral head relative to the socket and prevents the deltoid muscle the humeral head at the onset of contraction pulls undesirably far to the Acromion and areas of the Rotator cuff can be pinched. The support element can be dimensioned in this way be that its contact surface also in the resting position of the hanging Arms against the humeral head. In principle, however, it is sufficient if the Small contact surface in the hanging rest position of the arm Distance, for example one or more millimeters, from Humeral head runs away and only when the contraction begins Deltoid muscle on the humeral head comes to fix the pivot point.

The support element according to the invention is advantageously in Situations used in which the humeral head and possibly also the Socket is replaced by a prosthesis. The implantation of the However, the support element according to the invention can also be used without prosthetics of the actual one Shoulder joint are used because the beginning deformation of the Articular surfaces of the humeral head and the socket are often already early damage to the supraspinatus tendon and beyond lead lying bursa. In both cases, the support element improves Fixation of the pivot point of the humeral head. If the contact surface of the Support element formed as a sliding surface for the humeral head, so the available articulation surfaces to stabilize, and the primary joint stability is increased accordingly. This applies in particular to concave support surface of the support element.

The support element expediently comprises means for attachment to the Acromion, in particular at least one protruding toward Acromion Anchoring element, e.g. B. in the form of one or more webs or Cones that can be implanted in the acromion bone. Under one However, implantation should also be anchored here and below by cementing, gluing, using clips or the like can be understood.

The fixation of the socket element (glenoid prosthesis) Shoulder joint prosthesis on the neck of the shoulder blade is due to the low for the Attachment of available bone stick difficult and often not sufficiently stable. The stability of the fixation of the Joint socket element of a shoulder joint prosthesis can be considerable be improved if the support element and the socket element too connected to a unit or in the course of implantation and independently are connectable from the bone stock to such a structural unit. For example, a metal or / and plastic material Link the support element and the socket element preferably connect rigidly to each other. The one supported on the Acromion Support element contributes to the better fixation of the socket element on Shoulder blade neck and prevents tipping that leads to loosening of the socket element.

The improved fixation of the socket element in the shoulder blade-side bone stock allows the one assigned to the humeral head Sliding surface of the socket element compared to conventional To enlarge glenoid prostheses to an extent that the Circumference limitation of the sliding surface at least in regions over the shoulder blade side, for supporting the socket element protrudes laterally from certain bones. Especially in the area of Link can in this way increase the sliding surface considerably become.

The support element and the socket element can be made integrally consist of uniform material. It is expedient however, a unit in composite construction, in which the Connecting element from a rejection-free reaction in the bone stock implantable material, e.g. B. Titanium or the like. Is produced while the areas of the humeral head for support Support element or the socket element made of suitable sliding pairings such as B. metal-metal, ceramic-ceramic, metal-ceramic, polyethylene Ceramics, polyethylene metal or similar exist.

The connecting element is preferably designed such that it is in the course of Implantation can be adjusted. The adjustment can be made via adjustable Joining element, couplings or the like. But it can also be provided that the connecting element for implant adaptation purposes z. B. is permanently deformable by bending. So z. B. that Connecting element made of thermoplastic material, which for Adaptation is warmed to its softening temperature.

This was preceded by the subacromial support and Fixation of the socket element resulting advantages of improved fixation of the socket element in the bone and the Possibility to increase the articular surface to increase primary joint stability enlarge, under the first aspect of the invention in connection with a supporting element assigned to the humeral head is explained. The ones out the improved fixation of the socket element (glenoid prosthesis) resulting advantages can be seen in a second aspect of the invention, which has inventive meaning independent of the first aspect, too if the shoulder joint prosthesis has no support element, however, the socket element extends into the acromial space has reaching extension that can be supported on the acromium. The process corresponds in structure and mode of operation to the above explained connecting element and is in turn fixed to the acromium, as explained above for the support element. In particular, the extension can comprise means for attachment to the acromium, for example at least one protruding from the acromium, in this attachable anchoring element, for example in the form of a Screw, a clamp or a clamping part similar to a "press-fit"). It is understood that the extension may also be similar to the support element can be cemented or glued. The previous ones for that Configurations explained embodiments can also in the Insert the extension.

Exemplary embodiments of the invention are described below with the aid of a Drawing explained in more detail. Here shows

Fig. 1 is a schematic sectional view of a shoulder joint prosthesis according to a first aspect of the invention in the implanted state and

Fig. 2 is a schematic sectional view of a shoulder joint prosthesis according to a second aspect of the invention, also in the implanted state.

Fig. 1 schematically shows the shoulder blade 1 (scapula), which ended in the humeral head 3 upper arm 5, the light emanating from the shoulder blade 1 and the humeral head 3 dorsal and from above cross-spaced acromion 7 and articulated to the acromion 7 clavicle 9 ( clavicle). The deltoid muscle attached to the acromion 7 and lifting the upper arm leg 5 is indicated at 11 .

When the shoulder joint is intact, the humeral head 3 slides with a spherical joint surface in the concave joint surface of a joint socket formed on a neck 13 of the shoulder blade 1 . In addition to other ligaments of the rotator cuff, the supraspinatus muscle, whose tendon on the humerus head side extends from the side of the shoulder blade 1 through the subacromial space 15 formed between the acromion 7 and the humeral head 3 and extends opposite the joint socket, ensures that the humeral head 3 is fixed in this joint socket attacks the outside of the humeral head 3 . A bursa (subdeltoid bursa) covers the tendon of the subraspinatus muscle towards the acromion 7 and the delta muscle 11 .

When a shoulder prosthesis is implanted, in which one or both joint parts are replaced, the supraspinatus tendon or other parts of the rotator cuff are usually no longer present. As shown schematically in Fig. 1 as an example, the articular surface of the humeral head 3 can be z. B. designed as a spherical cap head prosthesis 17 , and instead of the glenoid joint surface of the shoulder blade 1 , a hollow spherical socket element 19 (glenoid prosthesis) can be implanted in the neck 13 of the shoulder blade 1 . When the deltoid muscle 11 begins to contract, the holding forces of the remaining rotator cuff are often not sufficient to hold the humeral head 3 in the socket element 19 . The humeral head 3 thus deviates upwards towards the Acromion 7 , which can lead to painful pinching effects and eccentric pressure on the implanted glenoid prosthesis to loosen it.

Defects of the type described above are avoided if, according to the invention, a support element 21 is implanted in the subacromial space 15 , which is supported on the one hand on the acromion 7 and on the other hand the humeral head 3 , in particular the articular surface of his prosthetic prosthesis 17 with a support surface 23 at a short distance from one or a few millimeters opposite or constantly abuts the prosthetic head 17 . When the deltoid muscle 11 begins to contract, the support element 21 holds the humeral head 3 in place essentially fixed in terms of the pivot point. Pinching effects of the type mentioned above or tilting deformations on the socket element 19 are avoided in this way.

The support element 21 thus improves the fixing of the pivot point of the humeral head 3 . Its support surface 23 is expediently curved concavely and forms an additional articular surface which slidably supports the humeral head 3 .

Similar to socket elements of conventional shoulder endoprostheses, as described for example in DE 39 17 285 A1 or EP 0 328 854 A1, the support element 21 can be made in one piece or as a composite element, e.g. B. which consists of an anchoring base part 27 and a support part 23 forming support part 29 may be formed. It is by a suitable attachment such. B. anchoring projections 25 or screws, brackets or by cementing or gluing but also clamping in the sense of a press fit or similar attached to the bottom of the acromion and forms a suitable articular surface to the humeral head or its endoprosthetic replacement. The articular surface can be part of a z. B. of metal-metal, ceramic-ceramic, metal-ceramic, polyethylene-ceramic, polyethylene-metal sliding pairs. In the exemplary embodiment in FIG. 1, the concave articular surface is formed by a support 35 made of the material of the sliding pairing component.

The support element 21 was previously explained in connection with a shoulder endoprosthesis. If only the supraspinatus tendon or the rotator cuff is damaged, the support element 21 can also be implanted if the shoulder joint is otherwise sufficiently intact.

In the example shown in Fig. 1 embodiment, the joint socket element 19 is formed as a separate component from the support member 21 and is also fixed separately from the support member 21 on the neck 13 of the scapula 1. Similar to the support element 21, the joint socket element 19 comprises a base part 31 , which is provided with anchoring extensions 33 , for example in the form of pins or ribs or the like, in the bone stock of the shoulder blade neck 13 or by means of screws, clamps or cementing, gluing but also clamping in the sense of a Fits or the like is anchored.

The bone stock available for anchoring the socket element 19 is comparatively small. In the event of deviations from the pivot point, the humeral head 3 exerts tilting forces on the socket element 19 , which can lead to a loosening of the socket attachment after a comparatively short time. The anchoring of the socket element 19 can be significantly improved if it is connected to the support element 21 to form a self-supporting unit. For this purpose, the base element 31 to be anchored in the bone stock of the shoulder blade neck 13 can be provided with an extension which extends into the subacromial space 15 and forms the support element 21 there, as is indicated by a dashed line in FIG. 1 at 37. The extension 37 can merge integrally into the base part 27 of the support element. In order to facilitate the implantation of the structural unit, the connection in the region of the support element 21 and / or the joint socket element 19 , possibly also in between, can be releasable, so that the elements are only connected to a fixed structural unit in the course of the implantation. The extension 37 connects the support element 21 and the socket element 19 to one another in a sufficiently rigid manner, so that the anchoring projections 25 of the support element 21 increase the load capacity of the socket element 19 . In addition, the extension 37 can be designed such that it is permanently deformable in the course of the implantation of the shoulder prosthesis to adapt to the shape of the bone structure. The extension 37 can consist of metal, for example titanium, or contain metal in a composite with other materials and can be bent to adapt to the bone structure. The extension 37 can also consist of a thermoplastic material that can be softened during the implantation for adaptation or else a plastic material that can be hardened after the adaptation.

The extension 37 fixed to the Acromion 7 considerably improves the fixation of the socket element 19 in the bone stock. Compared to conventional glenoid prostheses, the articular surface available to support the humeral head 3 can be considerably increased in this way, which increases the primary joint stability of the shoulder joint prosthesis.

The improved bone fixation of a glenoid prosthesis by additional fixation on the acromion can also be achieved independently of the advantages that can be achieved by means of a subacromial prosthesis, ie the support element. Fig. 2 shows a shoulder joint prosthesis according to a second aspect of the invention, in which only a glenoid prosthesis and possibly a head of the humeral head prosthesis is provided, but no Subacromialprothese within the meaning of the support member described above. Components with the same function shown in the figures are identified by the same reference numerals, but in FIG. 2 are provided with the letter a to distinguish them. To explain the structure and the mode of operation, reference is made to the description of components 1-19 , 25 and 31-37 of FIG. 1. Components 21 , 23 , 27 and 29 are missing.

Fig. 2 shows a shoulder joint prosthesis with a socket element 19 a (glenoid prosthesis), which in turn is fixed to the neck 13 a of the shoulder blade 1 a in the manner explained above. The socket element 19 has an extension 37 a which extends into the subacromonial space 15 a and is in turn fixed there on the acromion 7 a. In the area of the socket element 19 a, extensions 33 a are provided for fixing, while the extension 37 a is provided with anchoring projections 25 a. The variants of anchoring or fixing explained in connection with FIG. 1 can also be used in the variant of FIG. 2.

The additional fixation of the socket element 19 a by means of the extension 37 a on the acromion 7 a makes it possible to enlarge the articular surface 41 of the socket element 19 a that supports the humeral head 3 a compared to conventional glenoid prostheses. In particular, the articular surface 41 can now also protrude beyond the circumferential edge of the bone stock carrying the acetabular element 19 a, here the shoulder blade neck 13 a, without fear that articulated forces pry the acetabular element 19 a out of its anchoring. As shown in FIG. 2, the socket element 19 a can extend, in particular along the extension 37 a, far beyond the neck 13 a and reach close to the subacromial space 15 a. The enlargement of the concave joint surface 41 increases the primary joint stability of the shoulder joint.

The joint socket element 19 a shown in FIG. 2 is in turn designed as a composite element, a support part 35 a determining the pair of sliding surfaces of the joint surface 41 being arranged on the extension 37 a serving as the base part. It goes without saying that the components 35 a and 37 a can also consist integrally of uniform material.

In order to be able to adapt the extension 37 a to the spatial conditions of the skeleton, it can be designed to be adjustable in several parts. The extension 37 a can also be designed so that it is permanently deformable. In the case of extensions based on metal, these can be designed in such a way that they can be permanently bent for adaptation purposes. Extensions made of thermoplastic material can be permanently deformed by heating to the softening temperature. Preformed but deformable extensions made of a material that can be hardened subsequently, for example by UV radiation or heat or electron radiation, are also suitable.

Claims (16)

1. Shoulder joint prosthesis, characterized by a support element ( 21 ) to be arranged in the subacromial space ( 1 ) with support on the acromion ( 7 ), with a support surface ( 23 ) substantially above the humeral head ( 3 ) for supporting the humeral head ( 3 ). 2. Shoulder joint prosthesis according to claim 1, characterized in that the support element ( 21 ) comprises means ( 25 ) for fastening to the acromion ( 7 ), in particular has at least one anchoring element which projects from the acromion ( 3 ) and can be fastened therein. 3. Shoulder joint prosthesis according to claim 1 or 2, characterized in that it additionally comprises an articular socket element ( 19 ) assigned to the humeral head ( 3 ) on the shoulder blade side to be arranged. 4. Shoulder joint prosthesis according to claim 3, characterized in that the support element ( 21 ) and the socket element ( 19 ) are connected or connectable to form a structural unit. 5. shoulder joint prosthesis according to claim 4, characterized in that the support element ( 21 ) and the socket element ( 19 ) via a connecting member ( 37 ) are connected or connectable and the socket element ( 19 ) from the support element ( 21 ) separate means ( 33 ) to the shoulder blade side Has attachment. 6. shoulder joint prosthesis according to claim 5, characterized in that the connecting member ( 37 ) consists of metal and / or plastic. 7. shoulder joint prosthesis according to claim 5 or 6, characterized in that the connecting member ( 37 ) for implant adaptation purposes is permanently deformable. 8. Shoulder joint prosthesis according to one of claims 4 to 7, characterized in that the support element ( 21 ) and the socket element ( 19 ) are connected to one another in a substantially rigid manner. 9. shoulder joint prosthesis according to any one of claims 1 to 8, characterized in that the bearing surface ( 23 ) of the support element ( 21 ) is designed as a sliding surface for the humeral head ( 3 ). 10. Shoulder joint prosthesis according to one of claims 1 to 9, characterized in that the bearing surface ( 23 ) of the support element ( 21 ) is concave. 11. shoulder joint prosthesis with a joint surface element ( 19 a) defining a joint surface ( 41 ) for supporting the humeral head ( 3 a), to be fixed on the shoulder blade side, characterized in that the joint socket element ( 19 a) extends into the acromial space ( 15 a) , on the acromion ( 7 a) supportable extension ( 37 a). 12. Shoulder joint prosthesis according to claim 11, characterized in that the extension ( 37 a) comprises means ( 25 a) for attachment to the acromion ( 7 a), in particular has at least one anchoring element projecting from the acromion ( 7 a) and attachable thereon. 13. Shoulder joint prosthesis according to claim 11 or 12, characterized in that the extension ( 37 a) consists of metal and / or plastic. 14. Shoulder joint prosthesis according to one of claims 11 to 13, characterized in that the extension ( 37 a) is permanently deformable for implant adaptation purposes. 15. Shoulder joint prosthesis according to one of claims 3 to 14, characterized in that the joint socket element ( 19 ; 19 a) has a sliding surface ( 41 ) assigned to the humeral head (3; 3a), the circumference of which is at least partially over the shoulder blade side to support the joint socket element ( 19 ; 19 a) protrudes certain bone stock ( 13 ; 13 a). 16. Shoulder joint prosthesis according to claim 15, characterized in that the sliding surface ( 41 ) protrudes beyond the bone stock ( 13 ; 13 a) at least in the region of the connecting member ( 37 ) or the extension ( 37 a).