DE2422745C3 - Prosthesis to replace a bone joint - Google Patents

Description

The invention relates to a prosthesis for replacing a bone joint, with a central area, from the ends of which at least one extension extends in the longitudinal direction, which with is connectable to a bone part.

The use of joint prostheses, and in particular internal prostheses for hinge joints, counts already to the state of the art (US-PS 35 06 982). A prosthesis specially designed for artificial use is also known New formation of the metacarpal and finger joints (US-PS 35 93 342).

However, the use of such prostheses is not possible in all cases and it remains with severe ones Diseases only the joint obliteration as an alternative.

By obliterating the joints, a good, painless function can normally be achieved with a generally good one Achieve finger function in wrist disorders. In rheumatic disease, the joints cause obliteration however, there are disadvantages due to the long convalescence period, high failure rates due to, for example, bad ones Bone quality and weak tissue as well as regrowth of the rheumatic synovial skin in the Desolation areas.

The state of the art also includes a bone prosthesis in the form of an artificial bone, which takes the place of missing bone material (US-PS 36 83 422). This is a reinforcement made of metal surrounded by a fabric which is forked at both ends and with these Forks a connection at a lower jaw bone creates these consisting of tissue Connections are then sutured to the remaining parts of the lower jaw.

It is also known in the field of mandibular surgery to use a metal cage which is connected on both sides with fork-shaped bearing elements. These fork-shaped bearing elements encompass the remaining mandibular bone areas and

ίο are connected to these with screws (US-PS 37 20 959). In both of the above cases, a stiffening of a bone joint is not intended. but a bridging of missing lower jaw areas.

The prior art also includes a transversely elastic inner splint with tubular bones (DE-PS 9 13 228). A hollow, channel-shaped part is used here, which fits into the bone and serves as a support for a bone fracture

In contrast, the object of the present invention is to create a simply designed, rigid prosthesis which is especially suitable for a joint that has not been used
This object is achieved according to the invention in that the central area and the extensions that can be inserted into the respective bone parts are formed in one piece and that after insertion the prosthesis consisting of a metal mesh is filled with hardening cement. This advantageously results in an improvement in the treatment of joints suffering from arthritis, especially in the wrist, shoulder and finger joints.

The entire prosthesis is initially flexible so that it can be in the appropriate position after insertion can be bent. After inserting and filling the various cavities of the prosthesis with hardening cement, for example, the wrist is then brought into its normal position. After this If the cement sets, a very rigid, disused wrist is achieved.

The extension can be at one end of the central area in two, each in the adjacent bone parts insertable hollow approaches be forked. This results in a very good attachment of the prosthesis within the joint.

Furthermore, the extension at the other end of the central area can consist of a pair of identical, overlapping fingers exist, which allows a precise fit to the wrist and the

single finger is possible. A corrugated reinforcement element can be arranged between the fingers be, whereby the prosthesis experiences a further strengthening. The cement can be made from methyl methacrylate exist. It is also possible to cover the entire surface of the central area of perforations push through. The metal mesh of the prosthesis can be malleable and prior to the hardening of the cement be designed to be bendable.

The invention is explained in more detail below with the aid of an exemplary embodiment shown in the drawing described. In the drawing shows

F i g. 1 is a perspective view of the prosthesis;
2 shows a side view of the prosthesis before its implantation;

2a shows a side view of the prosthesis according to FIG. 2 after it has been bent into the position to be assumed after implantation;
F i g. 3 shows a cross section according to 3-3 in FIG. 2;

4 shows a plan view of the metal blank to which the prosthesis is made;

F i g. 5 is a plan view of a human hand skeleton with an adapted prosthesis; and

F i g. 6 shows a cross section along line β-6 in FIG. 5.

The prosthesis 10 has a triangular cross-section (FIG. 3) over the entire length of its central region, which forms a bridge part, and is at its front end 11 bifurcated At its rear end it is provided with a drooping, conically tapering extension 12 provided with a surface 13 and a substantially flat lower surface 14. The prosthesis is one-story in the form of a solid, rigid Supporting structure. The triangular shape gives this supporting structure the necessary strength The vertex 15 here forms a kind of ridge (FIG. 3).

The prosthesis is formed from a film of a biologically non-reactive metal that is suitable for implantation in the human body. Corrosion-resistant steel, tantalum, titanium or a cobalt chrome alloy such as B. Vitallium, are over the last Years of successful use as materials for implants and are also suitable for these Prosthesis.

The use of titanium has proven to be very good for this particular use. The implant is designed so that in practice the titanium reinforcement has the highest internal pressure exposed area of the overall construction, because the modulus of elasticity of titanium is significantly higher than that of the methyl methacrylate to be used for the implant. The biggest part a load acting on the structure is absorbed by the titanium reinforcement. The prosthesis 10 is filled with a base material made of methyl methacrylate and embedded in this

The embodiment shown consists of a titanium foil approx. 0.8 mm thick, approx. 140 mm long and approx. 58 mm wide. The blank 20, which in FIG. 4 is formed with perforations P, preferably on center lines, aligned with a spacing of about 2.4 mm

These perforations allow the methyl methacrylate mass and filled into the prosthesis to be stored thus a firm locking effect of the hardened methyl methacrylate with the prosthesis, since this is through the perforations connects extruded methyl methacrylate with the surrounding matrix; thus forms the entire methyl methacrylate mass is a composite unit with the prosthesis.

As shown in FIG. 4, the blank 20 has two rearwardly extending fingers 21 and 22 and two forwardly extending fingers 23 and 24. The back fingers are rounded and the ends front fingers 23 and 24 formed with flat ends extending parallel to fingers 21 and 22 a stiffening extension 25. The free leg 26 of this extension 25 is initially wavy to give the prosthesis the necessary support and to prevent fingers 21 and 22 from bending To be able to prevent straight bending during the insertion of the prosthesis (Figs. 2 and 2a).

Then the free leg 26 of the extension 25 is in the kink line 27 upwards in a overlying the front portion of the extension 25

ίο bent position. The top of the blank is down along the kink line 28 under the middle area of the prosthesis that forms the bridge part bent over and the lower area is bent upwards along the crease line 29 under the bent upper one

Curved area.

By applying side pressure against the central area of the resulting structure, the First 15 is formed, which gives the finished prosthesis the final triangular cross-section other fingers 21 and 22 are then after bent at the bottom at an angle of approx. 60 ° to the horizontal (Fig. 2). By tack welding the overlapping fingers 22 attached to the upper part 25 as in FIG. 3 with 31 denotes the front ends of the front fingers 23 and 24 are rolled up so that relatively pointed hollow projections 35 and 36 are in shape a fork.

To adjust the prosthesis, the surgical team must remove the diseased remainder of the File long wrist holes in the medullary cavities of metacarpal bones 41 and 40 (Fig. 5) slightly wider hole in radius 42. Methyl methacrylate cement is then placed in the cavities of the prosthesis filled in, and the prosthesis is easily folded squeezes to let the cement pass through the perforations P. Additional cement can also be placed in the cavities of the metacarpal bones and the radius. The bones are then bent over to an angle of approx. 60 °, so that the Hollow attachments 35 and 36 into the hollowed metacarpal bones and the extension 12 into the larger one Opening in radius 43 can be used. Optionally, additional methyl methacrylate composition, as in 43 in FIG. 5 shown around the prosthesis be brought around. The wrist and prosthesis are then in a straight position or in a closed position elected position bent, the bending or the stretching in the straight shown in Fig. 2a End position before the cement mixture hardens must be done.

The methyl methacrylate mixture remains in a deformable state for several minutes. It is there Be careful to ensure that the prosthesis is properly fitted and the body of the prosthesis is in front as the base material begins to harden.

1 sheet of drawings

Claims (7)

Patent claims: 1. Prosthesis for the replacement of a bone joint, with a central area, .from the ends of which extend into In each case at least one extension extends in the longitudinal direction, which with a bone part is connectable, characterized in that the central area and in the respective Bone parts insertable extensions (11, 12) are integrally formed and that after Insert the prosthesis (10) consisting of a metal grid and filled with hardening cement 2. Prosthesis according to claim 1, characterized in that the extension (11) at one end of the middle area in two hollow attachments that can each be inserted into the adjacent bone parts (35,36) is forked 3. Prosthesis according to claim 1, characterized in that the extension (12) on the other End of the middle area made up of a pair of identical, superimposed fingers (21, 22) consists. 4. Prosthesis according to claim 3, characterized in that between the fingers (21, 22) a corrugated reinforcing element (26) is arranged. 5. Prosthesis according to claim 1, characterized in that the cement is made from methyl methacrylate consists. 6. Prosthesis according to claim 1, characterized in that the entire surface of the central region is interspersed with perforations ^. 7. Prosthesis according to claim I, characterized in that the metal grid of the prosthesis is malleable and bendable before the cement hardens.