DE19820749A1 - Joint surface replacement for small hinge joints - Google Patents

Abstract

A joint surface replacement for small hinge joints, comprises two sections which are anchored in the adjacent bones. The joint sections are cylindrical shells made of a bio-ceramic, with penetrating bores for self tapping screws. The section nearest the body has a 180-225 degree cylinder shell, and its outer round surface locates with the inner round surface of the section away from the body, which has a 60-90 degree shell.

Description

The invention relates to a two-part bioceramic joint surface replacement for small Hinge joints, the middle and end joints of the fingers, big toe joints and Toe joints can be used.

Endoprosthesis for the small joints have been known for years. In EP-A1-0 455 929 proposed a joint prosthesis that has a bearing body in the form of a thin-walled Shell element made of high-strength metallic materials. At the back of the A shaft is molded onto the shell element and is anchored in the bone. This shaft is required because the metallic material does not have a permanent connection to the bone comes in.

According to EP-A1-0 396 519, an endoprosthesis with a special Anchoring element for holding a joint part and an artificial joint described the anchoring element being as firm and deep as possible in the adjacent bone ends is let in. A guide bush ensures sufficient centering. The Anchoring element is preferably made of titanium or is coated with titanium. In addition, the surface of the anchoring element can have grooves or depressions be designed to facilitate fixation in the bone and improve support. Both with this endoprosthesis and with the one in the aforementioned document described endoprosthesis, the bone must have sufficient mass and strength have so that the shaft is securely picked up and held.

Another endoprosthesis for the metacarpus is proposed in US 5,413,609. This Endoprosthesis is made of a biologically compatible material, but also has one molded shaft, which requires the necessary bone mass for attachment.

In WO-A1-96 / 05784 an endoprosthesis for small joints is described, which by was developed by an applicant of this invention. The endoprosthesis described here is anchored in the bone with a centering pin, the endoprosthesis parts being level Have contact surfaces that are applied to the bones. The bone must be up to this contact area will be resected.  

These known endoprostheses do not always meet all the requirements for one Replacement of the middle and end joints of the fingers or the base joints of big toes or Toe joints are placed.

Joint replacement parts with an attachment by a shaft that goes into the medullary canal Metacarpus / metatarsal or phalanx / big toe phalanges often loosen up because of the leverage that arises and because of the scant Blood vessel supply to the shaft and the medullary canal, compared to the trabeculae bone structure of the bony joint body.

The object of the present invention is to replace a joint surface for small Manufacture hinge joints that maintain the replacement of the destroyed articular surfaces which allows the ligaments connecting the bones.

Another task is the occurrence of leverage as between one Shaft of a joint replacement part and the surrounding medullary can occur and therefore avoid loosening particularly easily. It's supposed to be an opportunity for one tissue-saving joint replacement can be found.

The aforementioned tasks are achieved by replacing the articular surface for small ones Hinge joints, consisting of a distal and a near-body joint part for Anchoring in the adjacent bones, solved by the fact that the joint parts are cylindrical Represent shell body with a through hole, which consist of a bio-ceramic and are anchored in the cancellous joint bodies with self-tapping screws, the body-near cylindrical shell body 180 ° to 225 ° of a cylindrical surface embodied, the bulging side of which represents the articular surface and the bulging side is pressed exactly on the body-near bone, and the distal cylindrical Shell body 60 ° to 90 ° embodies a cylindrical surface, the hollow side of which Represents the articular surface and its bulging side fits snugly on the distal bone is pressed, the articulated surfaces of the cylindrical shell body approximately the same Possess radii. The area of the close-fitting cylindrical shell body is therefore greater than that of the distal cylindrical shell body.  

The cylindrical shell body can be made of a biologically compatible material exist, which has a bio-ceramic coating on the bone side. The self-tapping Screws are preferably made of titanium, but they can also be made of another biologically compatible material.

In a further development of the invention is in the distal cylindrical Shell body next to the through hole, a guide groove is present, which after the precisely fitting insertion of the shell body in the distal bones parallel to Diffraction direction of the joint is aligned, and in the body-near cylindrical Shell body is the corresponding bulge, which after inserting the cylindrical shell body in the bone part close to the body sliding in this guide groove is arranged. This creates an "inner guide" in the joint replacement.

This measure leads to a higher stability of the joint, even at high Axial movement of the joint shells is largely excluded.

A further increase in lateral stability and rotational stability are achieved by two parallel guide grooves in the distal cylindrical shell body reached. By doing Cylindrical shell bodies away from the body of the joint surface replacement are then located in addition to the through hole, two parallel guide grooves, which after inserting the cylindrical shell body in the distal bones parallel to the direction of diffraction of the Joint lie, and are in the body-close cylindrical shell body corresponding protrusions exist after inserting the cylindrical Shell body in the body-close bones sliding in these guide grooves of the cylindrical shell body remote from the body are arranged. The guides are on the right and left of the through hole. A lateral displacement or rotation of the joint parts this also counteracts each other. These implants are special suitable if the lateral ligaments are already damaged or weakened and theirs Can no longer perform functions fully.

The close-fitting cylindrical shell body can be between 180 ° and 225 ° Include cylinder surface. The sliding surface of the shell body close to the body can be reduced  when they are shifted towards the palm of the hand and pressed precisely onto the bone is that a flexion angle of 90 ° is reached. The self-tapping screw must then be inserted at an angle to the longitudinal axis of the bone.

By solving the problems presented at the beginning in accordance with the present Invention is the occurrence of leverage, such as between a shaft of a Joint replacement and the surrounding medullary can occur avoided. This Leverage can particularly easily lead to loosening of the endoprosthesis because of the The medullary canal shows only a few active menschyme cells compared to cancellous bone can firmly install the implant. By using a bioceramic also a solid bond with the bone.

The novel endoprosthesis is characterized in that, depending on the natural strength of the sidebands thanks to guiding grooves of different strengths on the distal shell body and guide strips on the near-shell shell body an "inner guidance" is created which counteracts the laterally shifting forces.

The problem of fastening a shaft attachment of the Joint replacement in the medullary canal does not occur. The shear forces in the apex plane and the torsional forces are created by the precise fitting of the ceramic shells into the bony joint body and by fastening with the self-tapping screw neutralized. The low tensile forces initially hold the connection of the screw with the The trabecular skeleton and the increasing firm adhesion during the healing process formed bone stood on the bioceramic surface.

Lateral displacements become the shell body on smooth joint-side surfaces through the sidebands, which remain uninjured or after the implantation of the endoprosthesis be sewn, and counteracted by the scarring after the operation. In Depending on the tension of the sidebands, a lateral shift and / or Additional twisting due to the shape of the joint-side surface with the effect the "inner leadership" are difficult.  

The surgical technique of matching the formation of the bone bed with the help of diamond-coated profile files, if possible while maintaining the sideband approaches Tissue-preserving and tissue-saving and at the same time enables the most extensive Standardization of the intervention. Additional filling or connecting material to which the Body could possibly react is not needed.

The guide grooves can be formed in a third circle to a semicircle and the Protrusions are then designed in a correspondingly third-circle to semi-circular shape. However, it is also possible to use any other sliding form of the guide grooves, the good guide and Have sliding properties and do not slip out of the guide or in it can be tilted. After inserting the body-like shell body of the Endo prosthesis in the bone part close to the body, the protrusions lie in this guide groove. The Movement of the joint is restricted to one direction and through this "inner guidance" relieves the sidebands.

The shape of the two-part, cup-shaped endoprosthesis for small hinge joints enables economical removal of joint-forming bones. The manufacture of the Endoprosthesis made of zirconium oxide or the coating of the endoprosthesis on the bone side Bioceramic enables a good connection of the bone with the endoprosthesis parts and a long-lasting healing success.

Another advantage of the inventive endoprosthesis results from the simple Attachment and the ceramic material of the endoprosthesis parts with its high Abrasion resistance and an exceptional smoothness of the joint-side surface, if this is made of zirconium oxide.

The planting takes place through a stretch-side or side access, at which the The extensor tendon is removed from the body and a side ligament (on the fingers each on the elbow and the toes on the outside) are cut in steps and after Implantation can be sewn again.  

The joint bodies are fitted with a profile file to the rear surface of the bowl-shaped Ceramic implants shaped. The ceramic bowls are adapted to the bone surface pressed on and fastened with a self-tapping screw, preferably made of titanium.

If the result of the joint surface replacement according to the present invention is not alternative techniques of joint replacement are still possible to achieve the expected success. This possibility is not available in conventionally known joint prostheses because mostly larger parts of the joint body must be removed. The situation after one The failure of the implantation of the new joint surface replacement is therefore essential cheaper than with the implantation of conventional joint prostheses.

With the appropriate shape, this endoprosthesis can also be used for the unloaded Ball joints are used in veterinary medicine.

The invention is to be illustrated using an exemplary embodiment with reference to the Drawings are explained in more detail. In the drawings, the same reference numbers are used same parts. It shows:

Figure 1A-1C a distal cylindrical shell body according to the invention in three views.

Figures 2A-2C a proximal semi-cylindrical shell body according to the invention in three views.

3A-3C possible embodiments of the "inner lead" of the cylindrical shell body.

. Figure 4 shows a joint replacement in a finger member;

FIGS. 5A and 5B show a further exemplary embodiment of a joint replacement in an extended and bent form; and

Fig. 6 is a profile file for shaping the bone bed.

In Figs. 1A-1C, a cylindrical body further shell body is shown according to the present invention in three views. The hollow shell of the cylindrical shell body is pressed onto the distant bone with a precise fit after it has been shaped with the aid of the profile file according to FIG. 4. A self-tapping screw, preferably made of titanium, is inserted through the central hole 1 into the trellis framework of the joint body remote from the body. In the illustrations in Figs. 1A and 1B, the hinge-side slots 2 are visible, which in this embodiment at the distal shell body consists of two parallel grooves with a third circular cross-section.

In FIGS. 2A-2C, the proximal shell body is to that shown in Figs. 1A to 1C illustrated hinge part also in three views. The hollowed-out side of the semi-cylindrical shell body is pressed onto the bone after it has been shaped with the help of the profile file according to FIG. 4. Through the center hole 1 , a self-tapping screw is also screwed into the trellis structure of the body-near joint body. The domes 3 respectively form the counterpart to the grooves 2 in Figs. 1A to 1C and set in this embodiment, two-thirds of circular protrusions are sliding in the direction of movement of the joint in the guide grooves 2.

In FIGS. 3A-3C possible embodiments of the guides 2 are shown. Both the distance and the width and depth of the guide grooves 2 in the shell body remote from the body, or the protrusions 3 in the shell body close to the body can be varied. The shapes are determined by the required load capacity and the guiding and sliding properties.

In FIG. 4, a joint replacement is shown in a finger member. The semi-cylindrical shell body is pressed onto the bone close to the body so that the natural movement of the joint is simulated.

In Fig. 5A and 5B, another embodiment is shown of a joint replacement in a stretched and bent position. In this embodiment, only a part of the articular surface of the distal bone is replaced by a cylindrical shell body. The prerequisite for this is that the joint surface is only slightly destroyed. The sideband attachments can be retained with this implant. The joint shell on the body-near bone is also displaced towards the palm so that the replaced joint can be flexed in a natural way. The self-tapping screw is inserted at an angle to the longitudinal axis of the bone.

Fig. 6 shows a diamond-coated profile file for processing the body-near bone, with which it is shaped to fit the body-close cylindrical shell body. The economical removal of bone eliminates the need to remove larger parts of the bony joint body or to completely remove it, as in the previously known endoprostheses.

Claims (7)

1. replacement joint surface for small hinge joints, consisting of a distal and a near-body joint part for anchoring in the adjacent bones, characterized in that the joint parts represent cylindrical shell bodies with a through hole, which consist of a bio-ceramic and are anchored in the cancellous joint bodies with self-tapping screws , wherein the body-close cylindrical shell body embodies 180 ° to 225 ° of a cylindrical surface, the bulging side of which represents the articular surface and the hollow-arched side of which is pressed onto the bone close to the body, and the distal cylindrical shell body embodies 60 ° to 90 ° of a cylinder surface, the hollow-arched side of which Represents the articular surface and the protruding side of which is pressed onto the bone remote from the body with a precise fit, the articular surfaces of the cylindrical shell bodies having approximately the same radii. 2. joint surface replacement for small hinge joints according to claim 1, characterized characterized in that the cylindrical shell body from a biologically compatible Made of material that has a bio-ceramic coating on the bone side. 3. joint surface replacement for small hinge joints according to claim 1, characterized characterized in that the self-tapping screws from a biocompatible Material such as titanium or bioceramics exist. 4. joint surface replacement for small hinge joints according to claim 1, characterized characterized in that in the distal cylindrical shell body next to the Through hole a guide groove is present, which after inserting the Shell body in the distal bones parallel to the direction of flexion of the joint is aligned, and in the close-fitting cylindrical shell body the corresponding Counter curvature is present, which after inserting the shell body in the body-near bone is slidably disposed in this guide groove. 5. joint surface replacement for small hinge joints according to claim 1, characterized characterized in that in the distal cylindrical shell body next to the Through hole two parallel guide grooves are present after inserting of the shell body in the distal bones parallel to the direction of diffraction of the Joint lie, and in the body-like cylindrical shell body the corresponding Counter-arches are present, which after inserting the shell body in the Bones close to the body are slidably arranged in these guide grooves 6. joint surface replacement for small hinge joints according to claim 4 or 5, characterized characterized in that the guide grooves are formed in a third circle to semicircular are and the counter-arches corresponding third-circle to semicircular Represent bulges. 7. Joint surface replacement for small hinge joints according to one of the preceding Claims, characterized in that the body-like cylindrical shell body is offset on the palm of the hand and pressed precisely onto the bone so that a Diffraction angle of the link of 90 ° is executable, the self-tapping screw is inserted at an angle to the longitudinal axis of the bone.