DE19820748A1 - Joint surface replacement for fingers or toes - Google Patents

Abstract

A joint surface replacement for finger and toe joints, which is anchored in the adjacent bones, comprises a spherical shell member made of a bio-ceramic, with a penetrating bore for self tapping screws. The main shell member (4) consists of a 180 degree section and the hollow section fits precisely on the bone. The smaller section (5) extends over 60-90 degrees and has a curved section which fits precisely over the bone.

Description

The invention relates to a non-guided bioceramic endoprosthesis for basic joints the toes and fingers.

Endoprosthesis for the small joints have been known for years. In EP-A1-0 455 929 proposes a joint prosthesis that a bearing body in the form of a includes thin-walled shell element made of high-strength metallic materials. At the A shaft is formed on the back of the shell element and is anchored in the bone. This shaft is necessary because the metallic material does not have a permanent connection the bone.

According to EP-A1-0 396 519, an endoprosthesis with a special Anchoring element for holding a joint part and an artificial joint described, wherein the anchoring element as firmly and deeply in the adjacent Bone ends is inserted. A guide bush ensures sufficient Centering. The anchoring element is preferably made of titanium or is made of titanium coated. In addition, the surface of the anchoring element can be scored or Recesses can be designed to facilitate attachment in the bone and to hold improve. Both in this endoprosthesis and in the one mentioned above Scripture described endoprosthesis, the bone must be of sufficient mass and Have firmness 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 has also a molded shaft that has sufficient bone mass for one Attachment requires.

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, with the endoprosthesis parts 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 only meet all requirements in exceptional cases a replacement of the basic joints of the toes and fingers can be made.

Joint replacement parts with an attachment by a shaft that goes into the medullary canal Metacarpal / metatarsal or phalanx / big toe phalanges is loosened too often because of the leverage that occurs and because of the sparse blood vessel supply to the shaft and the medullary canal, compared with the Trabecular bone structure of the bony joint body. They also affect Material properties of the replacement articular surfaces and the reaction of the body to the Abrasion significantly affects the utility value of prostheses.

It is the object of the present invention, a non-guided endoprosthesis for small To produce joints that cover the articular surface of a joint body that has not yet been destroyed to replace. The side ligaments that connect the joint-forming bones are supposed to be there be preserved.

Another task is the occurrence of leverage as between a shaft of a joint replacement part and the surrounding medullary can occur and therefore particularly easily lead to loosening, to avoid.

The above-mentioned tasks are achieved by replacing the articular surface on basic joints of fingers and toes, consisting of a body distant and a body near Joint part, which are anchored in the adjacent bones, solved in that the Joint parts made of spherical shell bodies made of a bio-ceramic, the one Have through hole and with self-tapping screws in the cancellous Joint bodies are anchored, the body-near shell body about 180 ° Represents spherical cap, is bulged to the joint gap and with the hollow-arched side a perfect fit on the loaded part of the articular surface of the metacarpal head or Metatarsal head is pressed, the distal shell body about 60 ° to 90 ° one  Spherical cap represents one of the natural articular surface of the basic limb base has simulated hollow curvature and with the bulging side fits snugly into the Basic limb-joint surface is indented, and the bulges of the joint-side Surfaces have approximately the same radii. The area of the body-hugging As a result, the shell body is always larger than that of the shell body remote from the body, as a result the natural function of the joint can be simulated.

The shell body can also be made of another biologically compatible material exist that is available for the production of endoprostheses, the then Bone-side surfaces with a coating made of a bio-ceramic become.

The screws that are provided for fastening the shell bodies are around self-tapping titanium screws. But it is also possible to remove these screws another biologically compatible plastic or a biologically compatible To manufacture ceramics.

In a special embodiment, the joint surface replacement is distinguished Basic joints of the toes in that the body-near shell body up to about 25 ° the back of the foot is pressed onto the metatarsal head to create the natural To restore joint mobility. The titanium screw is in one Angle introduced obliquely to the longitudinal axis of the bone.

In a special embodiment of the joint surface replacement on the basic joints of the fingers the body-near shell body is displaced 30 ° towards the palm of your hand on the head of the Metacarpal presses on to restore the natural movement rash to manufacture. The titanium screw is also at an angle to Longitudinal axis of the bone introduced.

The pressure forces are transmitted perpendicular to the loaded part of the Joint replacement. Shear and tensile forces are generated by the screws neutralized.  

The bone deposits are each prepared with profile files so that the Endoprosthesis parts can be placed on them with a precise fit. This formation of the Bone bed largely standardizes the process of implantation and creates greatest possible contact areas between the bio-ceramic shell bodies, for Example made of zirconium oxide, or the bio-ceramic coatings on the bone side another material is applied, and the bone. It will only be destroyed and strained joint surface parts removed and replaced. The guidance of the joints through the Sidebands are retained. In addition, bioceramics probably create because of their physical properties a permanent bond with the bone.

Within a few weeks, new bone formation starts, based on the biological highly active spongiosa of the natural joint body for a permanent connection of the Bone beams with the flat shell body made of a bioceramic, such as Zircon ceramic, or another biocompatible bioceramic coated Materials. It is the manufacture of the precisely fitting, motion-proof connection of Joint replacement and cancellous bone of the bony joint body with their high Cell density is the prerequisite for the fastest possible healing, d. H. a permanent one load-resistant connection due to the adhesion of the joint surface replacement parts newly formed bones. For example, if a shaft is used for attachment, loosening could easily occur due to leverage, since the medullary canal in Compared to cancellous bone contains only a few active mesenchymal cells. By the Use of self-tapping screws, especially made of titanium, and through that precise fitting insertion of the cylindrical shell body will the occurrence of Leverage forces that could lead to this loosening are largely avoided.

Added to this is the comparatively low injury and the low loss of tissue through the procedure, compared to known endoprostheses. The fastenings of the Tapes are protected and preserved.

For planting, the finger / toe base joint is opened on the stretch side, the Articulated body with rotating profile files over leading drilling wires with a precise fit  Use of shaped files and the endoprosthesis shells after removing the Drilling wires with self-tapping screws, which are made of titanium, for example, attached.

Access to the big toe joints is through a dorso-lateral skin incision from the base of the base of the toe over the base joint to the head of the first Metatarsal bone. The extensor hood and the joint capsule are on the side the middle rein of the extensor tendon opened. The endoprosthesis is then implanted as already described, by fitting the bone bearing with a profile file is molded and then the joint prosthesis is pressed on and with a self-tapping Screw is attached.

If the result of the joint surface replacement according to the present invention Alternative techniques of joint replacement are not yet leading to the expected success possible. This possibility is not the case with conventionally known joint prostheses present, since mostly larger parts of the joint body have to be removed. The Situation after the failure of the implantation of the new joint surface replacement therefore much cheaper than with the implantation of conventional joint prostheses.

This type of joint replacement can also be transferred to the shoulder joint at the predominantly endoprostheses with molded shaft are used. The This could reduce surgical trauma.

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

The invention will be explained below using a few exemplary embodiments. In the Drawings denote the same reference numerals, the same or comparable parts.

Fig. 1 shows a distal shell body according to the invention;

Fig. 2 shows a body-like shell body according to the invention;

Fig. 3 shows an endoprosthesis of the finger base joint, in which the body-near shell body is offset 30 ° to the palm;

Fig. 4 shows a just inserted endoprosthesis of the basic toe joint according to the invention;

Fig. 5 shows a 25 ° backward inserted body-near shell body of an endoprosthesis of the basic toe joint.

In Figs. 1 and 2, the two joint parts of the endoprosthesis are shown according to the present invention. The joint parts consist of shell bodies made of bioceramics or of a biocompatible material which is provided with a coating of bioceramics on the surface on the bone side. The body-near shell body consists of a half-shell, the distal joint part of a shell body, which represents about 60 ° of a spherical cap. The shell bodies have through holes through which a self-tapping screw is inserted into the cancellous joint body during implantation. The shell body remote from the body in FIG. 1 has a hollow curvature towards the joint gap and is fastened in the base of the basic limb bone with the pre-arched surface during implantation.

Fig. 2 shows the body-close shell body. The close-fitting shell body 4 has a protrusion that mimics the natural articular surface of the base limb base toward the joint gap and is securely attached to the head of the metacarpal / metatarsal bone with the hollow-arched side. The curvatures of the joint-side surfaces of the two shell bodies have approximately the same radii and the shell body close to the body has a larger articular surface than the shell body remote from the body, since it represents a larger section of a spherical cap.

Fig. 3 shows a basic joint which is formed between the metacarpal bone 2 and a phalange 3 . The metacarpal bone 2 is provided with a bulging shell body 4 which is offset by 30 ° towards the palm of the hand in order to simulate the mobility of the replacement joint and that of the natural joint. The self-tapping screws 6 are also shown in this illustration. It can be seen that the body-near screw 6 is inserted at an angle obliquely to the longitudinal axis of the bone in the head of the middle hand bone 2 , so that a displacement of the shell body 4 close to the palm is achieved.

A human toe 1 is shown in FIG . On the metatarsal bone 2 of the basic joint there is a pre-arched shell body 4 as a joint replacement close to the body and at the base of the base of the toe joint 3 there is a hollow arched shell body 5 as a part of the joint replacement remote from the body. In this exemplary embodiment, the replacement joint is used in a straight line. The screws 6 , with which the two shell bodies 4 , 5 are attached to the bone, have not been shown. The articulated surface of the bulging shell body 4 close to the body is larger than that of the bulging shell body 5 remote from the body, as has already been explained with reference to FIG. 3.

Fig. 5 also shows a human toe 1 , in which the basic joint is replaced by an endoprosthesis. In contrast to FIG. 4, the close-fitting shell body 4, however, is placed on the metatarsal bone, shifted backward by about 25 °. The self-tapping screws are indicated schematically in this illustration. With this design, a joint replacement is created, the movement of which is similar to that of the natural joint.

The shaping of the bone bed with profile files standardizes the process of Implantation as far as possible and creates the largest possible contact area of Bioceramics and bones. Only destroyed and loaded parts of the articular surface are removed and replaced. The guidance of the joints through the side straps is retained. Furthermore bioceramics probably creates one due to its physical properties permanent connection to the bone. This creates a joint replacement that the Requirements for the restoration of a destroyed joint largely met. A particularly good healing success can be expected if only the articular surfaces are still the joint bodies are not destroyed. The precisely fitting insertion of the shell body and the good connection between bone and bio-ceramic body or more bio-ceramic Coating offers lasting healing success. It will be a gentle on the tissue Solution offered in which neither cement nor filler materials are required.

Claims (5)

1. Replacement of the articular surface on basic joints of fingers and toes, consisting of a distal and a near-body joint part, which are anchored in the adjacent bones, characterized in that the joint parts consist of spherical shell bodies made of bioceramics, which have a through hole and which have self-tapping screws are anchored in the cancellous joint bodies, whereby the body-near shell body represents 180 ° of a spherical cap, is bulged towards the joint gap and is pressed with the hollow-arched side precisely onto the loaded part of the joint surface of the metacarpal head or metatarsal head, the body-distant shell body is about 60 ° to 90 ° represents a spherical cap, has a hollow bulge modeled on the natural articular surface of the base limb base and is pressed with the bulging side into the base limb articular surface with a precise fit, and the bulges of the surface on the joint side chen have approximately the same radii. 2. replacement of the articular surface on basic joints of fingers and toes according to claim 1, characterized in that the spherical shell body from a biological  compatible material, the bone side has a bio-ceramic coating owns. 3. replacement of the articular surface on basic joints of fingers and toes according to claim 1, characterized in that the self-tapping screws from a biocompatible material such as titanium or bioceramics. 4. joint surface replacement on basic joints of fingers and toes according to claim 1 to 3, characterized in that the close-fitting shell body for toes up to about 25 ° is pressed backwards on the metatarsal head, the self-tapping screw is inserted obliquely to the longitudinal axis of the bone. 5. replacement of the articular surface on basic joints of fingers and toes according to claims 1 to 3, characterized in that the body-near shell body for fingers 30 ° is pressed on the head of the metacarpal, offset the self-tapping screw at an angle to the longitudinal axis of the bone is introduced.