DE3343863C2 - Joint endoprosthesis - Google Patents

Abstract

A joint endoprosthesis, in particular a hip joint endoprosthesis, is described in which the areas lying outside the bone in the implantation position are surrounded by a tube-like part. The tube-like part, made of liquid-impermeable, body tissue-compatible, flexible material, prevents body fluids from entering the prosthesis material. Skirts of the tube-like part can be pulled over the cement joints and attached to the adjacent bone or periosteum and sealed against it. Within the tube-like part there is a protected space containing the joint gap, which can be filled with a lubricant and in which a shock absorber can be accommodated by forming a multi-part prosthesis part. The shock absorber can simultaneously exert a pumping effect so that the lubricant in the joint gap is continuously renewed (Figure 1).

Description

The invention relates to a joint endoprosthesis according to the preamble of the main claim.

Such a joint endoprosthesis is known from DE-OS 21 39 878. In this case, the joint, shaft, head and socket are surrounded by an artificial, flexible capsule that contains a fluid that is not the body's own, preferably physiological saline solution. The purpose of the measure is to prevent the prosthesis from becoming loose due to mechanical impact and friction by injecting a lubricant pump into the joint space that also acts as a shock absorber. The cement joints are exposed in the known joint endoprosthesis.

US Patent 38 64 758 describes a joint endoprosthesis in which the joint space is kept free of the body's own fluid in order to avoid hardening and the resulting mechanical stiffness. In this case, the entire prosthesis is not even covered. The cement joint is completely unprotected and exposed to the corrosive effects of the body's own fluids.

The object of the present invention is to design a joint endoprosthesis of the type specified in the preamble of the main claim in such a way that loosening, wear and corrosion phenomena can be avoided or kept to a minimum over a long period of time.

This object is achieved by the invention described in the characterising part of the main claim; an advantageous further development is specified in claim 2.

According to the invention, protection is provided at a point where the effects of body fluids are particularly dangerous, namely at the cement joints, which were exposed in known endoprostheses. The present invention is the first to recognize the danger to the cement joints from the body's own fluids and proposes protection against this by means of special aprons that are connected to the tube-like part surrounding the actual prosthesis, placed over the cement joints and attached to the bone or periosteum "beyond" the cement joint and sealed against it.

An embodiment of the invention is explained in more detail below with reference to the drawing; the only figure shows a schematic partial section through an inserted hip joint endoprosthesis (endoprosthesis itself not cut).

The drawing shows a schematic representation of a hip joint endoprosthesis in an inserted state. A first prosthesis part 1 comprises a shaft 2 which is cemented into the femur 3 in a known manner. A support collar 4a is formed on the bottom of a prosthesis neck 4 and a ball head 5 (in one or two pieces) is provided on the top. The ball head 5 sits in a second prosthesis part, the socket 6 , which is anchored in the pelvic bone 7 , forming a joint gap 9 ( exaggerated in the drawing).

A hose-like part 8 is attached tightly (eg glued, vulcanized, etc.) to the outer face of the socket 6 on the one hand and to the area of the collar 2 on the other. It consists of a flexible, impermeable and body tissue-compatible natural or plastic material, preferably polyester fabric. The hose-like part 8 encloses a space 10 containing the joint gap 9 , which is filled with a lubricant, e.g. oil.

At both ends, the tubular part 8 runs into protruding aprons 11 , 12. The apron 11 adjacent to the socket 6 is brought into contact with the pelvic bone 7 during the operation, fastened to it (or the periosteum) and sealed against it with a known, permanently plastic sealing agent. In a similar way, the apron 12 adjacent to the collar 4a is placed on the femur 3 during the operation, fastened to it (or the periosteum) and sealed.

The hose-like part 8 fulfils a dual function:

On the one hand, it prevents direct contact between the prosthetic material (metal or plastic) and the surrounding muscle tissue or body fluids, especially at the cement joints between the prosthetic parts and the bone. This not only prevents chemical reactions between the aggressive body fluids and the prosthetic material, but also prevents the prosthesis from becoming loose due to the effect of the body fluids on the cement joint.

On the other hand, the hose-like part 8 forms a reservoir for a lubricant, with which a permanent lubrication of the joint gap 9 is possible.

Claims (2)

1. Joint endoprosthesis, in particular hip joint endoprosthesis, with a first prosthesis part comprising a shaft, a neck and a ball head and a second prosthesis part comprising a socket which receives the ball head and forms a joint gap, both prosthesis parts being surrounded at least in the area exposed in the implantation position by a tube-like part made of flexible, body tissue-compatible, liquid-impermeable material, characterized in that the tube-like part ( 8 ) has aprons ( 11 , 12 ) at both ends which can be fastened to the surrounding bone or periosteum in the implantation position by bridging the cement joint and can be sealed against it. 2. Joint endoprosthesis according to claim 1, characterized in that the tubular part ( 8 ) is attached at its ends in a sealed manner to a prosthesis part ( 1 , 6 ).