DE4339895C1 - System for designing a knee-joint endoprosthesis - Google Patents

Abstract

System for designing a knee-joint endoprosthesis with articulation elements (11, 12) which can be secured at the lower end of the femur and which have a convexly curved articular bearing surface, with bearing elements (14, 15; 34) which can be secured at the upper end of the tibia 13 and which have a plane or optionally concave bearing surface (16, 17), and with a meniscus (18, 19) arranged movably between each of the femoral articulation elements (11, 12) and the tibial bearing elements (14, 15; 34), said menisci having slide surfaces (20, 21 and 22, 23) which are formed respectively on the upper side and the lower side and which are designed with a curvature complementing the associated articular bearing surface of the femoral articulation element (11 and 12) and the associated bearing surface of the tibial bearing element (14 or 15 or 34). The system includes tibial test bearing elements (29) with test meniscus (30), at least one bone-anchoring spike (31) being provided on the underside of the test bearing element (29). <IMAGE>

Description

The invention relates to a system for training a Knee joint endoprosthesis with

• - Can be attached to the lower end of the thigh (femur) Joint elements with convexly curved joint bearing surface,
• - Attachable bearing at the upper end of the tibia (tibia) elements with flat or concave storage area, and with
• - one each between the femoral and the tibial Bearing elements movably arranged on the meniscus Top and bottom trained sliding surfaces, wel che curvature complementary to the associated joint position gerfläche of the femoral joint element or the associated Storage area of the tibial bearing element are designed.

A knee joint endoprosthesis with the aforementioned features is known from DE 25 50 704 C2. The proposed knee Joint endoprosthesis is constructed so that it has the geometry of the "natural" knee joint and its bearing surfaces  imitated walking. Between the joint and the bearing element a movable meniscus element is provided, the on arranged on the top and bottom sliding surfaces complementary design on the one hand to the spherical bearing surface of the joint element and on the other hand to the bearing surface of the Have bearing element. With such a structure the natural play of the muscles and ligaments is relatively little disturbed and at the same time a relatively good distribution of the Load ensured. The joint and meniscus element on the one hand and the meniscus and the bearing element on the other on the other hand, can be relatively independent of each other move because the two are mechanically in a row switched partial joints each designed complementary Have storage space. In particular, the joint and the meniscal element relative to each other by three orthogo nale axes, and the meniscus element and the Lagerele ment can be relative to each other in two of these directions slide and rotate towards each other around the third of these axes. The resulting mobility between the Joint and the bearing element therefore includes both a rolling, a sliding and twisting and those combinations of these types of movements found in the natural knee. The essentially convex and relatively flat designs of the two storage areas can be so close to the surface events of the natural joint parts of the assigned Individual elements of the knee are adjusted that that too Interaction with the muscles and surrounding the joint Ligaments as in the natural knee. It is also advantageous the split version of both the femoral joint elements as well as the tibial bearing elements, so that the manufacture of semi-prostheses is possible. In this respect it differs the knee joint endoprosthesis according to DE 25 50 704 C2 also advantageous from the knee joint endoprosthesis according to the EP 0 519 873 A2 or EP 0 519 872 A1.

A disadvantage of the known systems is that the implant tion of the tibial bearing elements a particularly high level of skill required because before the tibial La  ger elements whose spatial position must be exactly predetermined. Very however, a correction is often necessary, which then is either omitted or only after another major one Intervention in the knee joint is possible. Most of all, must the bearing elements including the bone anchoring body are removed again with the result that the bone is considerably below it suffers. It should be borne in mind that the stability of Bones of older people is no longer too big. A man break out and reinsert the implanted Lagerele mente has significantly weakened the already attacked Resulting in bone.

The present invention is based on the object System for the formation of a knee joint endoprosthesis too create, with no major impact on the bones Corrections regarding the position of the ti to be implanted bial bearing elements and the menisci used are possible, taking the above-mentioned advantages of the knee joint endoprosthesis according to DE 25 50 704 C2 are to be maintained.

This object is achieved by the characterizing Features of claim 1 solved. Accordingly, inventions are made in accordance with tibial sample bearing elements and sample menisci worked, being on the bottom of the sample bearing elements at least one, preferably two small bones anchoring mandrel (s) is or are provided. That bone the corresponding sample bearing element should be anchoring mandrel just hold in place until the final one Location of the sample bearing element and thus the corresponding one final bearing element is fixed. Using a target device an attempt is made to test the sample bearing element with regard to its Optimally adjust the longitudinal and lateral inclination as well as the height, the sample bearing element may be used for this purpose must be removed several times to the bearing surface on Bone using a saw or similar tool to be able to work until the right location for that Sample bearing element is found, in which it during the full course of flexion and extension unchanged  lies on. The final implant element to be implanted speaks exactly the dimensions of the sample camp element. Accordingly, for the sample bearing element correct position in relation to the assigned femoral Hinge element has been found needs the trial camp element only through the final implant Bearing element to be replaced. The final implant Rende bearing element points much deeper in the bones penetrating anchoring means. However, this is not further harmful since the bearing to be finally implanted element only once in the previously using the appropriate Implanted sample bearing element found optimal position becomes. The arranged at the bottom of the sample bearing element The bone anchoring pins do not penetrate very deeply into the Bones one. The impact on is accordingly low the bone so that a repeated removal and renewed Inserting a sample bearing element has no negative effects have kungen on the bones.

Because the tibial bearing of the menisci is divided in two the corresponding storage areas can be independent of be adjusted to each other. This applies to both their longitudinal and lateral inclination as well as their Distance from the left and right femoral joint where with these two joint elements also into a single femur sled can be summarized. Because of the missing rigid connection between the two tibial implants also does not occur the undesirable "rocking" of the tibial Storage on how this is very common in one-piece execution fig is the case. This "rocking" also leads to one Loosening of the tibial implant with the result that this must be replaced after a relatively short time. It it is evident that the corresponding influence on the Tibia not very beneficial to patient well-being is.

The system according to the invention is also characterized through intercompatibility between femoral joint elements,  tibial bearing elements and the menisci from preferably Po polyethylene or the like material. The system described is suitable for all levels of care, d. H. for a so-called called half prosthesis, full prosthesis and also so-called Revisi prosthesis.

Preferred structural details of the Sy according to the invention stems, especially the sample bearing element, are in the Un Described claims. Is of particular importance but the formation of a groove-like sliding guide for the Trial and final menisci on the top the sample bearing elements as well as at the top of the end valid implanted tibial bearing elements. Preferably the groove-like sliding guide around the shin axis or Knee transverse axis bent around. This "tub-like" picture and sliding guidance for the Menisci has the consequence that the Menisci can be built relatively high across the entire width can. Accordingly, there is quite a lot of polyethylene Material for supporting the femoral joint elements for Available.

According to claim 5 is at least one of the two longitudinal side walls of the groove-like sliding guide in the direction from above inclined downwards outwards, the assigned Long side wall of the trial menisci or finally implanted ten Menisci has a complementary inclination. Through this The Menisci will safely measure in the sliding of the each associated bearing element held without weakening of the meniscus material. Both long sides are preferably walls of the groove-like sliding guide in the manner described inclined outwards for an even better hold of the To ensure Menisci in this sliding guide.

The sample menisci just like the final implant menisci at different heights. Accordingly different distances depending on the degree of wear the tibial bearing elements and the associated femoral Joint elements are balanced.  

The final plan corresponding to the sample bearing elements Tiert bearing elements each have min at least a peg-shaped or tab-shaped, preferably sleeve Sen-shaped anchoring element with at least one, esp special two superimposed cross holes. The aforementioned anchoring element extends for the purpose of better anchoring of the bearing element advantageously obliquely to the flat bottom of the same, the angle between the surface normal and the longitudinal axis of the anchor approximately 5 to 20 °. When training two Anchoring elements at the bottom of the final implan Tiert bearing element can ge differently inclined towards the flat underside of the bearing element his.

As can be seen from the above, this is system according to the invention immanent that the mentioned trial Menisci and sample bearing elements corresponding to Menisci and Bearing elements available for final implantation represents are.

The sample bearing elements show in the area of their meniscus Slide surface each have a hole to guide a kno Chen machining tool, in particular a hollow cylinder chisel on. Through this hole, the corresponding can Location hole for that at the bottom of the finally in planted bearing element arranged anchoring element be formed. The trial camp is also in this regard element particularly advantageous for the surgeon. The featured named guide hole preferably extends in one Inclination that corresponds to the inclination of the anchoring element on the Ent bottom side of the finally implanted bearing element speaks.

Last but not least, the trough-shaped design of the Lagerele ment the advantage that this not only with its lower part te, but also with its inside on the corresponding bear  processed bone. The position of the tibial implan In this way, tats are permanently protected against rotation chert. Since the "rocking" mentioned at the beginning does not take place a tensile load on the interface by lifting the tibial Bearing element avoided. Thus, a clear curl tendency of the tibial bearing elements even after prolonged use Use and heavy loads are expected.

An embodiment of the invention essen system explained in more detail with reference to the accompanying drawing.

Show it:

Fig. 1 a tibial trial bearing element in plan view;

FIG. 2 shows the sample bearing element according to FIG. 1 with the sample meniscus in a side view according to arrow II in FIG. 1;

Fig. 3, the trial bearing element according to FIG 1 with trial meniscal in side view according to arrow III in Fig. 1.

Fig. 4 is the trial bearing element according to FIG 1 with different height trial menisci in end view.

Figure 5 is a final implantable tibial Lagerele element in plan view.

. Fig. 6 shows the bearing element according to FIG 5 with the meniscus in Be tenansicht according to arrow VI in FIG. 5;

Fig. 7, the bearing element according to FIG 5 in side view according to arrow VII in Fig. 5.

Fig. 8, the tibial bearing element according to FIG 5 with differently under high menisci in end view.

Fig. 9 is a femoral slide in front view

Fig. 10 shows a knee joint endoprosthesis with a femoral slide and two independently placed tibial implants in front view and extended position.

The essential parts of a knee joint endoprosthesis will be explained with reference to FIG. 10. Accordingly, at the lower end of a thigh or femur 10, two joint elements 11 , 12 , each with a convexly curved articulated bearing surface, are arranged, while at the upper end of the shin or tibia 13 bearing elements 14 , 15 are fixed or anchored with a flat bearing surface 16 , 17 . Between the femoral joint elements 11 , 12 and the tibial bearing elements 14 , 15 , a meniscus 18 , 19 is arranged movably. Each Me niskus is provided on its top and bottom with sliding surfaces 20 , 21 and 22 , 23 , respectively, which are complementary to the curvature of the associated joint bearing surface of the femoral joint elements 11 and 12 and the associated bearing surface of the tibial bearing element 14 and 15, respectively are designed. The Menisci 18 , 19 each consist of polyethylene. The tibial bearing elements 14 , 15 are anchored to the bone by sleeve-shaped anchoring elements 24 , 25 with one or two transverse bores 26 , the anchoring sleeves 24 , 25 each being inclined to the longitudinal axis of the shin 13 . The cruciate ligaments are marked with the reference number 27 in FIG. 10. Incidentally, the tibial implants of interest here and the associated system for positioning them are explained in more detail with reference to FIGS . 1 to 8. To Fig. 9, it should be noted that this is a so-called A femoral component in front view and in the extended position, wherein the inner and outer joint member of the miteinan integrally connected. However, separate training is just as well conceivable, especially if a semi-prosthesis is implanted first and then a full prosthesis or revision prosthesis is subsequently implanted by means of a later operation. The femoral slide is identified by the reference number 28 in FIG. 9.

In FIGS. 1-4, a tibial trial bearing element 29 is shown with sample meniscus 30, wherein, a plurality of bone anchoring pins 31 are provided on the underside of the trial bearing element 29 which is formed generally flat. The bone anchoring mandrels 31 are net according to FIG. 4 along the two longitudinal edges of the sample bearing element. With the help of these thorns 31 not penetrating very deep into the bone, the sample bearing element can be anchored to the bone without damaging the bone until the correct position of the bearing element and associated meniscus relative to the associated femoral joint element is found. For this purpose, it may be necessary to remove the sample bearing element 29 several times in order to rework the bone support surface and to insert the sample bearing element again until the correct longitudinal and transverse inclination of the bearing element and the correct height of the meniscus has been found. Then a tibial receiving bore is formed through a bore 32 formed in the meniscus sliding surface 33 , preferably by means of a cylindrical hollow chisel. This tibial bore is used to receive an arranged on the underside of the finally implanted Lagerele element pin, tab or sleeve-shaped Ver anchoring element 24 , which is shown in FIGS . 6, 7, 8 and 10. In FIGS. 5-8 is shown by the reference numeral 34 finally to be implanted bearing element including meniscus 35, which corresponds in size and shape to the trial bearing element together with the sample meniscus shown in FIGS. 1-4. Accordingly, both the sample bearing elements 29 and the finally implanted tibial bearing elements 34 each have a groove-like sliding guide 35 on their upper side for the sample and finally implanted menisci 30 and 36, respectively. The groove-like slide guide 35 is curved according to FIGS. 1 and 5 in plan view, namely around the shin leg longitudinal axis or transverse knee axis. This allows a relative rotation of the knee joint in accordance with the possibility of natural rotation.

According to FIGS. 4 and 8 is at least one of the two longitudinal side walls 37 and 38 of the groove-like sliding guide 35 in the direction from top to bottom obliquely inclined outward, with the associated long side wall of the trial menisci 30 and the finally implanted menisci 36 a complementary Inclination. As a result, the Menisci are secured against unwanted lifting off the bearing element.

According to FIGS. 4 and 8, the trial menisci as well as the 30 have finally implanted menisci 36 under schiedliche heights. These are indicated in FIGS. 4 and 8 with the sliding bearing surfaces 20 of different heights.

As already stated above, the the sample-Lagerele elements 29 corresponding final implanted Lagerele elements 34 on their underside in each case at least one tenon, laschen- or sleeve-like anchoring element 24 (in Fig. 10 and 25) with at least one transverse bore 26. A sleeve-like anchoring element with transverse bore 26 has the advantage that it grows optimally in the bone. In addition, only a minimal bone substance has to be removed during the implantation, namely by means of the already mentioned cylindrical hollow chisel or milling cutter. According to FIGS. 6 to 8 and 10, the anchoring elements 24 and 25 extend obliquely relative to the flat lower surface of the bearing member 34, wherein the angle between the surface normal and the longitudinal axis of the anchoring element 24 or 25 is about 5 to 20 °. In the implanted state, the anchoring elements are preferably inclined towards the longitudinal axis of the tibia, as is shown schematically in FIG. 10.

Menisci corresponding to the sample menisci 30 are of course made available for the final implantation, as can be seen from a comparison of FIG. 4 with FIG. 8. Incidentally, Fig blank. 4 and 8 further appreciate that the bearing elements 29 and 34 are each formed wan nenförmig in cross section. This allows the height of the Me nisci to be maximized over the entire width of the same.

In practice, it makes sense to have three different ones Sizes for both the sample bearing elements and the end valid implanted bearing elements including Menisci To make available. The sliding surfaces of the bearing elements are preferably smooth polished.

Moreover, the trough-shaped cross section of the bearing elements makes it possible to anchor them so tibially that they rest against the bone both with their underside and with their inside. This ensures a permanent hold of the bearing elements in the bone: in case of doubt, only the meniscus must be replaced, the height of the new meniscus having to be adapted to the conditions which have meanwhile changed due to wear and tear on the knee and / or the other meniscus. The new meniscus should again guarantee the original lateral stability and correct overall knee axis. In FIGS. 1 and 5, the sliding movement of the meniscus is in each case within the groove-like slide guide 35 with the double arrow 39.

Claims (13)

1. System for the formation of a knee joint endoprosthesis with

• - At the lower end of the thigh (femur) ( 10 ) fastenable joint elements ( 11 , 12 ) with a convexly curved joint bearing surface,
• - At the upper end of the tibia (tibia) ( 13 ) attachable bearing elements ( 14 , 15 ; 34 ) with a flat or concave bearing surface ( 16 , 17 ) and with
• - Each between the femoral joint ( 11 , 12 ) and the tibial bearing elements ( 14 , 15 ; 34 ) movably arranged meniscus ( 18 , 19 ; 36 ) with sliding surfaces ( 20 , 21 or 22 , 23 ) which, in terms of curvature, are designed to be complementary to the associated joint bearing surface of the femoral joint element ( 11 or 12 ) or the associated bearing surface of the tibial bearing element ( 14 or 15 or 34 ),

characterized by tibial trial bearing elements ( 29 ) with trial menisci ( 30 ), at least one small bone anchoring mandrel ( 31 ) being provided on the underside of the trial bearing element ( 29 ). 2. System according to claim 1, characterized in that on the underside of the sample bearing element ( 29 ) are each arranged near the two longitudinal edges of the same bone anchoring mandrels ( 31 ). 3. System according to claim 1 or 2, characterized in that the sample bearing elements ( 29 ) as well as the finally implanted tibial bearing elements ( 14 , 15 ; 34 ) on their top each with egg ner groove-like slide guide ( 35 ) for the sample - ( 30 ) and finally implanted Menisci ( 18 , 19 ; 36 ). 4. System according to claim 3, characterized in that the groove-like slide guide ( 35 ) is bent in plan view around the longitudinal axis of the shin or around the transverse axis of the knee. 5. System according to claim 3 or 4, characterized in that at least one of the two longitudinal side walls ( 37 or 38 ) of the groove-like slide guide ( 35 ) is inclined obliquely outwards in the direction from top to bottom, the associated longitudinal side wall of the sample menisci ( 30 ) or the finally implanted Menisci ( 18 , 19 ; 36 ) has a complementary inclination. 6. System according to one of claims 1 to 5, characterized in that the sample ( 30 ) as well as the finally implanted Menisci ( 18 , 19 ; 36 ) have different heights ( Fig. 4 and Fig. 8). 7. System according to any one of claims 1 to 6, characterized in that the sample bearing elements ( 29 ) corresponding finally implanted Lagerele elements ( 14 , 15 ; 34 ) on their underside at least one pin or tab-shaped anchoring element ( 24 , 25 ) with at least one transverse bore ( 26 ). 8. System according to claim 7, characterized in that the anchoring element ( 24 , 25 ) extends obliquely to the flat underside of the bearing element ( 14 , 15 ; 34 ), the angle between the surface normal and the longitudinal axis of the anchoring element ( 24 , 25th ) is about 5 to 20 °. 9. System according to claim 8, characterized in that with two or more anchoring elements ( 24 , 25 ), these are inclined to different degrees relative to the flat underside of the bearing element ( 14 , 15 ; 34 ). 10. System according to claim 7, characterized in that the anchoring element ( 24 , 25 ) is an anchoring sleeve. 11. System according to any one of claims 1 to 10, characterized in that the sample menisci ( 30 ) corresponding menisci ( 14 , 15 ; 34 ) are provided for the final implantation. 12. System according to any one of claims 1 to 11, characterized in that the sample bearing elements ( 29 ) in the region of their meniscus sliding surface ( 33 ) each have a bore ( 32 ) for guiding a bone processing tool, in particular a cylindrical hollow chisel, aufwei sen.