DE3343863A1 - Joint endoprosthesis - Google Patents

Abstract

The invention describes a joint endoprosthesis, especially a hip endoprosthesis, in which the regions lying outside the bone in the implanted position are surrounded by a hose-like part. The hose-like part made from a liquid-impermeable, flexible material compatible with the body tissues prevents access of body fluids to the prosthetic material, and aprons of the hose-like part can be drawn over the cement joints and fixed to the neighbouring bone or the periosteum and sealed relative to the latter. A protected space containing the joint cavity which can be filled with a lubricant and in which a shock absorber can be accommodated by a multi-part design of a prosthetic part is obtained inside the hose-like part. The shock absorber can simultaneously execute a pumping action, so that the lubricant present in the joint cavity is continuously replenished (Figure 1). <IMAGE>

Description

Joint endoprosthesis

Description The invention relates to a joint endoprosthesis, in particular Hip joint endoprosthesis, with a first, a shaft, a neck and a ball head comprehensive prosthesis part and a second, one the ball head to form a The prosthesis part encompassing the joint space accommodating the socket.

In known endoprostheses of this type, the prosthesis material lies (Metal or plastic), as long as it is not embedded in the bone, freely in the Body tissue and is the aggressive body fluids that fill the surgical cavities exposed. Despite careful selection of the prosthesis material, it is possible to do this Do not avoid signs of degeneration (wear, corrosion) in the long term. In addition, there is often a loosening of the endoprosthesis, that of the cement joints goes out.

The object of the present invention is to provide a joint endoprosthesis of the type mentioned in such a way that loosening, wear and tear Corrosion phenomena can be avoided or kept to a minimum for a long time.

This object is achieved according to the invention in that both prosthesis parts at least in the area exposed in the implantation position of a hose-like Part made of flexible, body-friendly, liquid-impermeable material surrounded is.

The invention is based on the knowledge that the aggressive, the Body fluids filling cavities attack the prosthesis material and to blame for certain loosening phenomena in the cement joints are. In the fluids that are typically around the well-known joint prostheses form, are the osteolytic Prostaglandin E2 and oxygen radicals.

Advantageously, not only is the prosthesis itself covered by a liquid-impermeable, surrounding tubular part; this rather comprises two associated with the prosthesis parts Aprons that are in the implantation position bridging the cement joint surrounding bone (or periosteum) can be fastened and sealed against it are. This particularly protects the cement joint.

The hose-like part expediently consists of a polyester fabric. This not only has the desired body tissue compatibility and impermeability to water; it also has the requirements for a very frequent alternating bending stress mechanical properties. In addition, its outside is covered with cells, so that there is no formation of cavities.

The hose-like part is advantageously in each case one area each attached to a prosthesis part sealed so that within the tubular Partly between these areas a sealed one containing the joint space Space is created, this space being filled with a lubricant.

In this way, a lubricant reservoir is created with de one Permanent lubrication of the joint space is possible.

The lubricant is expediently an oil.

One of the prosthesis parts in the one surrounded by the tube-like part Area can be designed in several parts as a shock absorber. The hose-like part in this case also protects the shock absorber parts that are movable relative to one another; the shock absorber in turn protects the endoprosthesis itself as well as the cement joints before peak loads.

It is useful if the shock absorber effect is at least partially is based on the fact that when the endoprosthesis is stressed by a lubricant or several narrow outlet channels is pressed, and that a spring element is provided, which when relieving the endoprosthesis for a reset of the relative to each other moving parts.

When the outlet channels open into the joint space, it is achieved that the shock absorber effect simultaneously with a pumping effect to renew the Lubricant is connected in the joint space.

The first part of the prosthesis can be used as a shock absorber and possibly as a pump be designed as follows: a) The ball head and neck can be moved axially to a limited extent with respect to one another separate parts; b) one area of the neck dips into a hole in the ball: head and there forms a displacement piston for the lubricant; c) the from acting as a displacement piston neck area beauf hit part of the bore of the ball head represents on the one hand with the outlet channel or channels and on the other hand via a non-return valve to the inside of the hose-like part, the space containing the lubricant in communication.

It is advantageous if several outlet channels leading radially to the joint gap are provided by a distribution space formed in the interior of the ball head go out. This ensures that the entire joint space is permanently lubricated evenly ensured.

It is geometrically particularly favorable if the one containing the check valve Connecting path between the richly acted upon part the bore of the ball head and the inside of the hose-like part, with lubricant-filled space a bore extending axially through the neck and at least one radial communicating with the latter via the non-return valve Includes intake duct.

Again for geometric reasons, it is advantageous if the bore is designed as a stepped bore in the ball head, which has a narrower area and has a further area connected to this via an annular shoulder and when the neck dipping into the ball head has a complementary narrower area and has a wider area connected to this via a ring shoulder, and when the spring element is arranged between the two ring shoulders.

The spring element can be a ring made of rubber-elastic material. The rigidity of this material, the alternating stresses in extraordinarily has grown in a good way, can largely be adapted to individual requirements will.

Alternatively, the spring element can also be a spiral spring.

Embodiments of the invention are described below with reference to the drawing explained in more detail; FIG. 1 shows a schematic partial section through an inserted one Hip joint endoprosthesis (endoprosthesis itself not cut); Figure 2: one Partial section through an endoprosthesis (without socket) with integrated shock absorber and Lubricant pump.

In Figure 1, a hip joint endoprosthesis is schematically inserted State shown. A first prosthesis part: includes a shaft 2, which is cemented into the femur 3 in a known manner. On a prosthetic neck 4 a support collar 4a is formed at the bottom and a ball head 5 (one or two pieces) at the top intended. The ball head 5 sits under the formation of a joint gap 9 (in the drawing exaggerated) in a second part of the prosthesis, the socket 6, which in the pelvis: bones 7 is anchored.

A hose-like part 8 is on the one hand on the outer end face the pan 6 and on the other hand in the area of the collar 2 attached tightly (e.g. glued, vulcanized, etc.). It is made of flexible, impermeable and natural or synthetic material compatible with body tissue, vo; preferably off Polyester fabric. From the hose-like part 8 is a joint space 9 containing Enclosed space 10, which is filled with a lubricant, such as oil is.

The hose-like part 8 runs into protruding aprons at both ends 11, 12 off. The skirt 11 adjacent to the pan 6 is in contact during the operation brought to the pelvic bone 7, attached to this (or to the periosteum) and sealed against this with a known, permanently plastic sealant. In the apron 12 adjacent to the collar 4a becomes correspondingly during the operation applied to the femur 3, attached to this (or the periosteum) and sealed.

The hose-like part 8 fulfills a double function: On the one hand it prevents direct contact between the prosthesis material (metal or plastic) and surrounding muscle tissue or body fluids, in particular also on the Cement joints between prosthesis parts and bones. This doesn't just become chemical Reactions between the aggressive Body fluids and that Prosthetic material avoided. It also prevents loosening of the prosthesis, which can be traced back to the action of the body fluids on the cement joint is.

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

In Figure 2 is a second embodiment of a hip joint endoprosthesis shown partially and in section. As far as parts correspond to those of Figure 1, they are marked with the same reference number plus 100.

The embodiment of Figure 2 differs from that according to Figure 1 mainly in that the ball head 105 and prosthesis neck 104 separate Parts are that under weight load (for example when walking) a certain axial relative perform movement and thereby act both as a shock absorber and as a pump for the lubricant works.

For this purpose, the ball head 105 is provided with a stepped bore 113, which opens into an inner distribution chamber 114.

The distribution space 114 stands over several, narrow, radial outlet channels 115 with the outer spherical surface of the spherical head 105 and thus with the joint gap in connection.

The end of the prosthesis neck 104 is in the stepped bore 11 ~ des Ball head 105 introduced and complementary to this double stepped: A first, Area 104b which is tapered in relation to main area 10 has an outer diameter which corresponds to the inner diameter of the further area 113b of the stepped bore 113. A second region 104c, which is further tapered in relation to region 104b, has a Outer diameter, which is the inner diameter of the narrower area 113c the stepped bore 113 corresponds. Areas 104b and 104c of neck 104 are connected to one another via an upwardly pointing annular shoulder 116. The areas 113b and 113c of the stepped bore 113 are over a downwardly pointing annular shoulder 117 connected to each other. A is located between the two ring shoulders 116, 117 elastic, annular spring element 118. In the drawing, this spring element is 118 shown as a solid ring made of rubber-elastic material. Possibly However, a spiral spring can also be used here.

In the jacket surface of the area 104c of the prosthesis neck 104 is incorporated a groove 119 in which an O-ring 120 is seated. This seals the Neck area 104c radially against bore area 113c.

The area 104b of the neck 104 is where it does not enter the stepped bore 113 immersed, provided with a plurality of radial suction channels 121, which in a Intake chamber 122 open.

The suction chamber 122 is a short axial bore 123 with a overlying valve chamber 124 in connection. This in turn communicates with an axial bore 125 which emerges in the end face of the neck region 104c.

In the valve chamber 124 is a designated as a whole with the reference symbol 12E Check valve built in. This includes a valve disk 127, which is of a Coil spring 128 is pressed against a valve seat 129 surrounding the bore 123 An axially extending groove 130 is machined into the jacket surface of the neck region 104b. A screw 132 is screwed into a radial threaded bore 131 of the ball head 105, which engages with its inner end in the axial groove 130 of the neck area 104b. The screw 132 limits in this way between the ball head 105 and the throat possible axial relative movement and prevents rotation between these parts.

The endoprosthesis shown in Figure 2 is just like that surrounded by Figure 1 by a hose-like part 8 (not shown in Figure 2), one lying between the tube-like part 8 and the endoprosthesis, the Joint space containing space is filled with lubricant. Open into this room the intake ducts 121 of FIG. 2.

They are, like the rooms 122, 124, the holes 123, 125, the Distribution chamber 114 and the outlet channels 115 are filled with lubricant.

If the endoprosthesis is stressed while walking, the neck areas look for each other Push 104b and 104c further into the ball head 10. Resists this movement not only the spring element 118. An additional resistance results from this, that the neck region 104c protruding like a piston into the bore region 113c is the In the distribution chamber 114 displace lubricant and through the narrow outlet channels 115 must squeeze into the joint space. A pressing out of the i manifold 114 is located Lubricant through the bore 125 is prevented by the check valve 126, the valve disk 127 of which is pressed onto the valve seat 129.

If the endoprosthesis is relieved again, the neck areas become 104b and 104c under the influence of the spring element 118 back again (in the drawing pushed down).

In this direction of movement, the valve disk 127 lifts from the valve seat 129 from. Via the intake channels 121, the intake chamber 122, the bore 129, the valve chamber 124 and the bore 125, new lubricant is sucked in from the space 10 (FIG. 1) and brought into the manifold 114.

With cyclical loading and unloading of the endoprosthesis, alSo under simultaneous shock absorber effect, the lubricant is continuously pumped in a circle, so that the lubricant in the joint gap is constantly renewed.

The following qualitative criteria obviously apply to the arrangement described Relationships: The maximum stroke (unless limited by screw 132 the greater the weight of the prosthesis wearer and the lower the rigidity of the spring element 118 is.

The shock absorber effect is the harder the stiffer the spring element 118, the larger the upper end face of the neck area 104c, the more viscous it Lubricant, the greater the length and the smaller the number and cross-section of the outlet channels 115 is.

The at. Finally, the amount of lubricant delivered in each cycle of movement is greater, the greater the stroke and the greater the upper face of the neck area 104c is.

There is thus a large number that can be selected largely independently of one another Parameters available so that the dynamic characteristics of the endoprosthesis can be individually tailored for each prosthesis wearer.

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Claims (14)

Claims 1. Joint endoprosthesis, in particular hip joint endoprosthesis, with a first prosthesis part comprising a shaft, a neck and a Kuael head and a second, one receiving the ball head with the formation of a joint gap The prosthesis part encompassing a pan, characterized in that both prosthesis parts (1, 6) at least in the area exposed in the implantation position of one hose-like part (8) made of flexible, body tissue-compatible, liquid-impermeable Material are surrounded. 2. joint endoprosthesis according to claim 1, characterized in that the hose-like part (8) has two aprons assigned to the two prosthesis parts (1, 6) (11, 12) has the in the implantation position bridging the cement joint can be attached to the surrounding bone (or periosteum) and sealed against it are. 3. joint endoprosthesis according to claim 1 or 2, characterized in that that the tubular part (8) consists of polyester fabric. 4. joint endoprosthesis according to one of claims 1 to 3, characterized in that that the hose-like part (8) in each case in one area on one prosthesis part (1, 6) is attached in a sealed manner, so that within the hose-like part (8) between these areas a sealed space containing the joint gap (9) (10) arises, and that this space (10) is filled with a lubricant. 5. joint endoprosthesis according to claim 4, characterized in that the Lubricant is an oil. 6. joint endoprosthesis according to any one of the preceding claims characterized in that at least one prosthesis part (101) in the hose-like Part (8) surrounding area is designed in several parts as a shock absorber. 7. Joint endoprosthesis according to claim 6 when referring back to claim 4 or 5, characterized in that the shock absorber effect is at least partially is based on the fact that when the endoprosthesis is stressed by a lubricant or a plurality of narrow outlet channels (115) is pressed, and that a spring element (118) is provided is, which when relieving the endoprosthesis for a reset of the relative to each other moving parts (104, 105) ensures. 8. joint endoprosthesis according to claim 7, characterized in that the outlet channels (115) open into the joint gap (9) in such a way that the shock absorber effect simultaneously with a pumping action to renew the lubricant in the joint space (9) is connected. 9. joint endoprosthesis according to one of claims 6 to 8, characterized in that that the first prosthesis part (101) is designed as a shock absorber and possibly as a pump as follows is: a) the ball head (106) and neck (104) can be moved axially to a limited extent with respect to one another, separate parts; b) the neck (104) dips into a region (104 b, 104 c) Bore (113) of the ball head (106) and forms a displacement piston there for the lubricant; c) the neck area acting as a displacement piston (104 c) acted upon part of the bore (113) of the ball head (106) stands on the one hand with the outlet channel or channels (115) and on the other hand via a Check valve (126) with the inside of the hose-like part (8), the lubricant-containing space (10) in connection. 10. joint endoprosthesis according to claim 9, characterized in that several outlet channels (115) leading radially to the joint gap (9) are provided, the distribution space (114) formed inside the ball head (106) go out. 11. Joint endoprosthesis according to claim 9 or 10, characterized in that that the connection path containing the check valve (126) between that of the neck region (104 c) acted upon part of the bore (113) of the ball head (106 and which the lubricant containing space (10) within the hose-like part (8) an axially through the neck (104) extending bore (125) and at least one with this over the Check valve (126) communicating radial suction channel (121) comprises. 12. Joint endoprosthesis according to one of claims 9 to 11, characterized characterized in that the bore (113) in the ball head (106) is designed as a stepped bore is, which has a narrower area (113 c) and one with this over a ring shoulder (117) connected further area (113 b), and that in the ball head (106) immersed neck (104) complementary to this a narrower area (104 and a wider area (104 b), and that between the two ring shoulders (116, 117) the spring element (11C is arranged. 13. Joint endoprosthesis according to claim 12, characterized gekennzeic; that the spring element (118) is a ring made of rubber-elastic material. 14. Joint endoprosthesis according to claim 12, characterized in that that the spring element (118) is a spiral spring.