SK279513B6 - Anchor element - Google Patents

Abstract

The anchor element (4), in the form of a cylindrical capsule, has an external thread to be screwed into a bone (2), for fixation of an articulated element (1) on the coupling end (13) thereof. The anchor element (4) is at least partially hollow and is provided with threads (8, 9) running from an inserted end (7) to the articulated element (1). The anchor element (4) has a surface that can at least partially knit together with the tissue (2) to obtain a permanent anchoring in the longitudinal axis of the bone. The anchor element (4) consists of a material that is compatible with the tissue of the bone. Thickness of the anchor element's (4) wall is gradually thinning towards the inserted end (7) and the wall is elastically deformable.

Description

Technical field

The invention relates to a fastening element for supporting the articulation mechanism of a toe or other reconstructed joint, to a method of positioning the fastening element in a bone and to a reconstructed joint.

A preferred embodiment of the invention will be described in detail in the following, according to the reconstruction of the toe joint. However, the invention is not limited thereto. The invention can be applied to other similar joints, such as toe joints, elbow joints, etc. The invention can also be used in reconstructions after amputation or other defect.

BACKGROUND OF THE INVENTION

The reconstruction of the finger joints by means of prostheses is primarily carried out on the joints on which rheumatic changes have occurred. Known prostheses for this purpose are Swanson's silastic toe joints. These joints consist of a silicone-like material, have an elongated shape and have ends with a substantially circular cross-section. The ends may be stowed and anchored or anchored in the shaft of each bone. The central part of the prosthesis is elastically deformable, thus forming a true joint mechanism.

For the reconstruction of the toe joints, a prosthesis is also known. George - cement prosthesis.

The problem associated with these conventional prostheses is that the fastening element supporting or supporting the prosthesis mechanism is released and / or damage to the prosthesis occurs in the load direction. Therefore, recent attempts have been made with titanium fasteners anchored in the bone marrow cavity for osseo-integration (ossification) as described in Hagert et. al. 'Metacarpophalangal Joint Replacement with Osseo. integrated Endoprostheses' in Scand. J. Plast. Reconstr. Surg. 20, p. 207 to 218.1986.

Oral or dental prostheses permanently anchored in bone tissue are already known. This method of dental integration by ossification (osseo-integration) has been developed in the last 25 years by Professor Branemark and his colleagues with excellent results using gum clamps to fasten teeth or bridges. However, the experiments done by Hagert using this method to reconstruct the joints of the fingers did not fully meet expectations. Obviously, unacceptable results have arisen because of the completely different conditions when using this “dental method” in prosthetic reconstruction of the finger joints.

By known methods, for example, the clamping element is anchored perpendicular to the longitudinal axis of the bone. In the toe joint, the clamping element is located in the bone axis. This, of course, causes completely different loads and pressures on the fastening elements.

At present, the main problem in orthopedic prosthetic surgery is the release of the bone attachment unit. However, with a success rate of more than 90% in dental implants over a period of 20 years, many other problems have arisen that need to be considered.

One of the main problems is increasing the wear on the joint mechanism. When osseo-integration is used, it is necessary to produce a prosthesis of a different type to that used hitherto. In order to allow replacement of the hinge mechanism without breaking the fixation in the bone, the prosthesis system must be divided into individual components where the hinge element can be separated from the actual fastening element.

Furthermore, when the two-step method is used, it must be possible to attach the joint mechanism in the second stage if the patient or at least the reconstructed joint is not to remain stationary. Two factors must therefore be taken into account: first, the joint mechanism is subject to wear and must therefore be replaceable. Secondly, in order to use the two-step method, the hinge mechanism must be replaceable.

It has now surprisingly been found that the problems and disadvantages of the described methods can be overcome by the fastening elements according to the invention.

The invention is based on extensive experimental biological analysis of the structure and function of joints in a disease or defective condition after wear or inflammatory distribution of bone tissue, and extensive studies of vascular delivery to the bone marrow. It has been found that destroyed articular cartilage and connective tissue, bone and marrow tissue must be considered as a structural and functional unit. It is absolutely necessary to count on the cooperation between bone and marrow tissue, especially for a long time when the hardened tissue is to function as a support element.

The invention is therefore based on the fact that when anchoring the prosthesis of the joint surface and the ligament of the carcass parts close to the joint is anchored, the interaction between bone and marrow tissue must be respected. This means that the attachment element in the long bone marrow cavity must be attached by a mechanical element which allows the connection between the bone marrow and bone tissue along, as far as technically possible, the entire length of the attachment element, paying particular attention to the boundary layer between the marrow and compact bone the wall of the medullary cavity.

SUMMARY OF THE INVENTION

These requirements are met by a cylindrical bushing fastening element having an external thread for screwing into the bone for fastening the hinge element at its connecting end, wherein the fastening element is at least partially hollow and is provided with slits extending from its open insertion end to the hinge element, and has a surface that can at least partially coalesce with bone tissue to effect permanent anchoring within the bone along the longitudinal axis, the fastening element being a bone-compatible material according to the invention, which is based on the wall thickness of the fastening element being gradually decreases to the insertion end and the wall is resiliently deformable, wherein the fastening element is adapted to the surrounding bone tissue, and wherein the notches have cutting edges.

According to a preferred embodiment, the fastening element according to the invention is formed by a guide sleeve surrounding the connecting end, which can be fixed in the guide sleeve secured against rotation.

According to a further preferred embodiment, the coupling end is adapted to engage the coupling parts of the hinge element by pressure.

According to a further preferred embodiment, a coupling is arranged between the hinge element and the guide bushing.

According to a further preferred embodiment, the fastening element consists of titanium.

The surface of the fastening element is preferably provided with a layer of titanium.

According to a further preferred embodiment, the surface of the fastening element is a radial outer surface and is provided at least partially with microcavities having a diameter of 10 to 300 nm.

The hinge element of the fastening element is preferably part of an artificial finger joint.

The present invention further provides a reconstructed joint.

Application of the attachment element to the bone comprises: cutting the bone at its joint to open the bone marrow cavity; adjusting the space in the medullary cavity at the joint; inserting a guide sleeve into the space; screwing the fastening element into the medullary cavity, the guide sleeve being used to center the fastening element.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will be explained in the description of an exemplary embodiment with reference to the accompanying drawings, in which:

Fig. 1 is a partial cross-sectional view of a reconstructed finger joint with an attachment element according to the invention; FIG. 2 shows a fully reconstructed toe joint, FIG. 3 shows how the fastening element is positioned in the long bone, FIG. 4 is a perspective view of a fastening element; FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 4, FIG. 6 is a partial cross-sectional view 6-6 of FIG. 4 shows a part of the articulated mechanism according to the invention, FIG. 7 shows the coupling of the hinge mechanism to the fastening elements according to the invention, and FIG. Figures 8 to 10 show some other embodiments, showing how a non-rotating wedging effect is achieved between the fastening element and the guide sleeve and / or its improvement.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 shows portions of the long bones 3 and 2 on each side of the toe joint mechanism 1.

The rotationally symmetrical fastening element 4 has the shape of a hollow, substantially sleeve-like body 5 with an external thread 6 and a decreasing wall thickness. The open insertion end 7 of the body 5 tapers conically and is provided with notches 8 and 9 starting at the open end 7.

The end 13 (FIG. 6) of the fastening element 4 at the hinge mechanism 1 is located in the guide sleeve 11. The guide sleeve 11 shown is substantially cylindrical and is provided with longitudinal undulations along its outer radial surface. These undulations may be identical to the axial portion of the threaded rotary symmetrical clamp used in dentistry.

The guide sleeve 11 surrounds the articulated end 13. The articulated end 13 of the body 5 is closed by a wedge-like action against the inner surface 14 of the guide sleeve 11 when the body 5 is additionally screwed into the bone tissue. The connecting parts 15 of the hinge mechanism 1 are detachably inserted into the hinged end 13. The connecting parts 15 can be made as centering pins (Fig. 7) protruding from the hinge mechanism 1. These pins fit into corresponding joints 16 in the fastening element 4 or in the connecting part ( (not shown) arranged between the guide sleeve 11a and the hinge mechanism 1.

One or more openings whose edges towards the surface are sharp may be directly connected to the outer radial surface of the fastening element 4. When the body 5 is screwed into the bone, the thread 2 cuts itself by this screwing. In this case, the removed bone tissue is pushed inwardly into the fastening element 4, as shown in FIG. 5th

As the wall thickness of the fastening element 4 gradually decreases towards the insertion end 7 and / or because the fastening element 4 has longitudinal slits 8 and 9, the requirements for proper deformation are met and the danger of stress concentration is largely reduced, which is mainly a cause of earlier problems. embodiments. The arrows B-B in FIG. 1 denote the elasticity of the open insertion end 7, i. j. ability to adapt the surrounding tissue. The same applies to the A-A arrows.

The notches 8 and 9 may be made with sharp edges α, since the cut bone tissue 17 passes into the cavity as shown in FIG. 5, the fastening element 4 is itself its own preparation tool. At the same time, optimum conditions for normal anatomical and physiological situations are ensured, so that disruption of the remaining biological tissue, i. j. marrow and bone tissue are minimized.

Fig. 2 shows the reconstruction of the joint already with the fastening element 4.

Fig. 3 shows how the fastening element 4 is located in the boundary zone between the pulp and bone tissue. The wall thickness of the sleeve body 5 decreases towards the incised insert 7 ending with a bevelled cutting edge 12. The edges of the longitudinal slits 8 may also be designed as cutting edges. The bone tissue cuttings 17 formed when the fastening element 4 is screwed into the medullary cavity are thus transferred to the cavity in the body 5, as shown in FIG. 5th

In the operation, a portion of the long bone 2 at the joint is cut to expose the marrow cavity. A probe (not shown) is then inserted into the medullary cavity to determine a suitable longitudinal axis for insertion of the fastening element 4. The probe is used as a direction finder to center the fastening element 4 as desired.

Then the hole for the guide sleeve 11 is carefully drilled into the exposed marrow cavity. After application of the guide sleeve 11, the sleeve body 5 is screwed down through this guide sleeve 11 into the pulp cavity.

Before that, however, the probe is taken out. The hinged end 13 of the fastening element 4 extends slightly outward and upward as indicated by the locations 18 and its diameter is slightly larger than the lower opening of the guide sleeve 11.

Finally, in this way, a wedge effect occurs between the articulated end 13 and the guide sleeve 11 (when the sleeve 11 moves to the position shown in FIG. 6 dotted) so that both the guide sleeve 11 and the sleeve body 5 are positioned as desired.

The fastening element 4 and the guide sleeve 11 consist of or are made of titanium or are provided with a titanium layer. The structure of the titanium surface is such that at least a portion of the respective surface is integration supported.

The surface may advantageously contain irregularities in the form of microscopic wells as described in Swedish patent 7902035-0, the wells having diameters between 10 and 1000 nm, preferably up to 10 to 300 nm. Alternatively, the chemical composition of the titanium coating may be due to certain positive tissue reactions, such as described in Swedish patent 8505158-9.

Fig. 8 shows how the upper end 19 of the sleeve 11 facing the flange 20 of the fastening element 4 is provided with a protruding edge 21 arranged to cooperate with the thread 22 on the flange 20. Element 4

Thus, the housing 11 and the housing 11 are non-rotatably secured when the body 5 is screwed sufficiently far into the bone tissue.

An alternative blocking effect between the housing 11a of the element 4 is achieved by the arrangement shown in FIG. 9, where axial undulations are provided on the element 4 to cooperate with the inner surface of the housing 11.

A further blocking effect can be achieved by the arrangement shown in FIG. 10 with special grooves 24 on the upper edge of the fastening element 4, which is screwed into the tissue.

While the invention has been described in accordance with a preferred embodiment, other variations and modifications are known to those skilled in the art. It is therefore advantageous that the invention is not limited either by these facts or by the subordinate points of the invention.

Claims (9)

PATENT CLAIMS A fastening element (4) in the form of a cylindrical sleeve having an external thread for screwing into a bone (2) for fastening the hinge element (1) at its connecting end (13), being at least partially hollow and having notches (8, 9) extending from its open insertion end (7) to the hinge element (1) and having a surface that can at least partially coalesce with bone tissue (2) to effect permanent anchoring in the interior of the bone along its longitudinal axis, being formed by material; which is compatible with bone tissue, characterized in that the wall thickness of the fastening element (4) gradually decreases to the inserted end (7) and the wall is resiliently deformable, the fastening element (4) being adapted to the surrounding bone tissue and the notches (8) 9) have cutting edges. A fastening element according to claim 1, characterized in that it is formed by a guide sleeve (11) surrounding the connecting end (13), which can be secured in the guide sleeve (11) against rotation. Fastening element according to claim 1 or 2, characterized in that the connecting end (13) is adapted to receive the connecting parts (14) of the hinge element (1) by pressure. The fastening element according to claim 3, characterized in that a coupling is arranged between the hinge element (1) and the guide sleeve (11). Fastening element according to one of Claims 1 to 4, characterized in that it consists of titanium. Fastening element according to one of Claims 1 to 4, characterized in that its surface is provided with a layer of titanium. Fastening element according to one of Claims 1 to 4, characterized in that its surface is a radial outer surface and is provided at least partially with micro-cavities with a diameter of 10 to 300 nm. Fastening element according to one of Claims 1 to 7, characterized in that the hinge element (1) is part of an artificial finger joint. An artificial joint having one or two fastening elements (4) is a part according to claims 1 to 8.