DE19632266A1 - Artificial joint for bones - contains calcium phosphate cpd. shaft section fixed into shaft body and lying exposed on the surface of this body - Google Patents

Abstract

Shaft for an artificial joint for bones, comprising shaftbody with a ball secured to it at one end and also contg. a hole for receiving at least one shaft section, contains at least one hardened shaft section comprising a calcium phosphate cpd., fixed into the hole in the shaft body and at least part of this section is exposed on a surface of this body.

Description

The invention relates to operations in which artificial Ge steering, especially a shaft, more precisely said a composite shaft that is used to hold a spherical body, which serves as an artificial joint, in egg a bone is embedded.

Generally, joints, such as hip joints, have Shoulder joints or the like, a similar structure. On For example, the hip joint consists of a caput femoral (Headboard) and a fossa acetabuli. The Caput Femoral has essentially the shape of a spherical body, and the Fossa acetabuli of a deep pan. About two thirds of the caput femoral sit in the acetabular fossa. Similar to be is a shoulder joint from a caput humeri (head part) in Form of an essentially spherical body and one Fossa acetabuli in the form of a deep pan.

So far, operations have been in the field of orthopedics  using artificial joints or joints Biomaterial or the like for reconstruction function capable or damaged joints.

Artificial joints used in joint replacement surgery generally consist of a spherical body ceramic as a replacement for the head part of a joint, such as for example a Caput Femoral or a Caput Humeri. Of the spherical ceramic body is on one end of a shaft orderly. The shaft is generally made of metal. The other The end of the shaft is inserted into human bones and attached to it, such as on a femur (for hip replacement) or a humerus (for shoulder gels replacement). To complete the pan-shaped fossa Acetabuli becomes a hemispherical pan made of metal or Composition made of metal and synthetic resin. The hemispherical pan is inserted into the human bone bed and attached to it, such as on one Hip bones, d. H. the hipbone (for hip replacement) or a shoulder blade (for shoulder joint replacement). Thus receives the main structure of the artificial joint.

With conventional artificial joints, the shaft is attached two joining procedures on a human bone Stigt, with a method that uses cement and a process without cement.

In the cement process, a receiving hole is first made a predetermined location in human bones drills. Then much of the stem of the artificial Joint inserted into the drilled receiving hole. Finally becomes a cementing material such as an adhesive in the gap between an inner wall of the receiving hole and inserted the shaft. When the cement material cured tet, the artificial joint is solid with the human Bones connected. Although this connection initially holds up well, it worsens over time. This allows the  Move the shaft in the bone drilled. Is this Cement material also a polymer such as Po lymethyl methacrylate (PMMA), the monomeric components of the polymer causing problems that lead to infection could lead.

In the process without cement are on the surface of the Metal shaft of the artificial joint with a surface treatment such as titanium spraying or the like topographical features such as small protrusions and dents manufactured. Then a large part of the shaft is used the machined surface in the previously drilled receptacle hole inserted. The bone then grows to the processed one Shaft surface. The gap between the inner wall of the up hole and the shaft will gradually grow through the filled in the bone. However, since this procedure is described in An initial stage after joint replacement not satisfactory Guaranteed hold, the patient must long after the op ration lie to an insufficient connection of the bone to prevent with the shaft. As an alternative, widespread spreads a biocompatible material such as B. Apatite for Ver improvement of the binding of the shaft surface with the growing Bones sprayed onto the surface of the shaft. With this The process keeps the connection compared to the previous one described procedures without cement better in the beginning. That on sprayed apatite, however, disappears over time as we is crystalline and very soluble. With this procedure cannot ensure a permanent and good hold who the.

An object of the invention is to address the inadequate The artificial joint shaft is held in the human knot to improve and for a long time without ver maintain deterioration.  

The invention solves this problem by the features of Pa Tent claims 1. Advantageous further training is the subject of subclaims.

The invention is based on the finding that a calcium Phosphate compound due to its high chemical stability and low solubility improves grip when so in the shaft of the artificial joint is inserted that at least at least a part of it is free on a surface of the shaft lies.

Because in the shaft arrangement of the invention the shaft body is too additionally a hardened part such as a Gesin teres part or from a calcium phosphate compound contains molded part, the calcium phosphate compound has chemical stability and low solubility, that Shaft part is firmly connected to the shaft body and mind least in part of it on a surface of the shaft body exposed, you get an excellent grip of the shaft partly and thus the shaft body in the human bone such as the femur or scapula, and the degree of Liability, d. H. the hold can be maintained over a long period of time the.

The invention will now be described with reference to the drawings explained, with similar parts with matching reference characters are designated. In it show:

Fig. 1 is a front view of a shaft assembly for artificial union joints according to a first embodiment of the invention;

FIG. 2 shows the top view of the shaft arrangement shown in FIG. 1;

Fig. 3 is a perspective view of a plate-shaped shank portion of a calcium phosphate compound that is used in the embodiment shown in Figures 1 and 2 shaft assembly.

Figure 4 is a front view of a shaft assembly for artificial union joints according to a second embodiment of the invention.

Fig. 5 shows the cross section of the Schaftan arrangement shown in Figure 4 along the line VV.

Fig. 6 is the front view of a shaft assembly for artificially Liche joints according to a third Ausführungsbei game of the invention;

Fig. 7 is a top view of the arrangement shown in Fig. 6;

FIG. 8 is a perspective view of the block-shaped shaft part made of a calcium phosphate compound, which is used in the shaft arrangement shown in FIGS . 6 and 7; and

Fig. 9 is a perspective view of an artificial hip joint, which is attached to a femur during a hip replacement operation.

The shaft arrangement according to the invention has a shaft body and at least one separate shaft part. An end area of the Shank body holds a spherical body of an artificial one Joint. Much of the shaft body is in the human Chen bones embedded. The shaft body can be from any lovely material, such as metal, ceramic, one Alloy or other materials that are conventional for the Manufacture of artificial joints used best hen.  

The shaft part preferably consists of a hardened part from a calcium phosphate compound. It gets in an up Participation part such as a hole, a passage hole, a depression, a cut surface or the same recorded and fixed in such a way that at least one Area of the shaft part on a surface of the shaft body pers exposed. The shaft part is with any fastening agents such as cement material, adhesive, Pins, screws or the like in the receiving part of the Shaft body attached. The fasteners can be used for used alone or in combination.

Depending on various factors such as that desired result of the type of joint to be replaced etc. the shape of the shaft part can be very different. So the shaft part can have the shape of a plate, a block, of a cylinder or the like. Furthermore, the different shaft parts for themselves or in combination ver be applied.

In one embodiment of the invention, the shaft part a plate body that in a previously formed recess inserted and attached. The depression serves as an opening receiving part for the shaft body and preferably has one Plate body corresponding shape. In this example it is Plate body preferably with adhesive on the shaft body attached.

In a further embodiment of the invention that is Shaft part a block, which in a previously formed through is inserted into the passageway and fastened in it. The through Gang hole serves as a receiving part for the shaft body and has preferably a shape corresponding to the block. With this Embodiment is preferably the block in the through shaft of the shaft body with fasteners as for for example glue, pins, screws and preferably with a combination of adhesive (for fixing in the  Through hole) and pins (for attachment to the shaft body) attached.

In a further embodiment of the invention that is Shaft part a cylindrical body, which at one end section of the shaft body is attached. The end section serves as a receiving part for the shaft body and is with ge suitable fasteners such as a pen head attached to it.

In these and other shaft designs of the invention ha ben the shaft body and the shaft part as a whole preferred have a smooth surface so that the shaft is light and correctly inserted into the hole drilled in the bone can.

The calcium phosphate compound that is used for the hardened Shaft part of the shaft assembly used has a good one Biocompatibility and preferably a molar ratio of Calcium to phosphorus (Ca / P ratio) from 1.5 to 2.0. Appropriate Nete calcium phosphate compounds contain, for example a variety of apatites such as hydroxyapatite, fluoroapatite and the like, primary calcium phosphate, dibasic cal calcium phosphate, three-base calcium phosphate, four-base Calcium phosphate and other calcium phosphates. The above mentioned Calcium phosphate compounds can be used alone or in com combination can be used.

In practice, the calcium phosphate compound is hardened so that you get a hardened part with the shape and size speaking the desired shaft part. The calciumphos phat connection can be achieved using any conventional method be tert. Thus, after the powdery Kal is formed Ziumphosphat connection to a powder pressed part a sintered tes part with the desired shape and size with a relati ven density from 30 to 100%, preferably 40 to 80%. The right The relative density of the sintered product should not be less  amount to 30%, otherwise the mechanical strength will not is guaranteed. Generally has a porous sintered body an excellent effect due to its relatively low density the growth and migration of the bone in the sintered body. In the invention, however, a sintered one Use bodies with a relative density of 100% without any problems be det.

Alternatively, the calcium phosphate compounds can be used after each any conventional method can be shaped so that one receives a molding, the size and shape of the desired corresponds to th shaft part. For example, a hydraulic calcium phosphate as a starting material ver be applied. After forming, the hydraulic Kalzi umphosphate hardened with water, creating the desired shape and size is achieved.

The stem used in the stem assembly of the invention Part can be made by any conventional method be put. For example, hydroxyapatite is considered to be out used material, so the sintered shaft part are made as follows. From phosphate and calcium Salt components (starting materials) are produced in one conventional wet process produced an emulsion, which then is dried in a rotating drum dryer. Here hydroxyapatite powder is obtained. The powder is then in egg ner conventional form such as a hydrostati shaped dry press. So you get a product Hydroxyapatite with a shape that matches the desired shaft part corresponds. After shaping, the product is at a tem temperature of about 1000 to 1200 ° C annealed, for example. Like this with you get the shaft part of the invention.

In the aforementioned method of manufacturing a shaft sometimes a hydrostatic drying press is used as a mold used. However, in practice any other device can or another method can be used. Suitable For  mungsverfahren are, for example, molding, injection molding, turning the molded powder or the like.

Furthermore, the shaft part of the invention can be made using Tricalzium-α-phosphate as a starting material the. The tricalcium α-phosphate is mixed with water and kneaded, which, if desirable, for manufacture of a hardened part can contain an acid as hardener. This produces a hardened part, which is then ver will work that you ent the desired shaft part speaking form. Alternatively, the hardened product also in a suitable form by kneading the mixture Tricalcium α-phosphate made with water in the mold be, whereby you can avoid the manufacturing process.

The invention will now be described with reference to various Embodiments of a shaft assembly described. The However, the invention is not based on the following embodiments games limited.

Fig. 9 shows a perspective view of an artificial hip joint with a shaft assembly of the invention on a femur.

A hemispherical cup 12 is attached to and inserted into a hip bone 11 at a predetermined location. The pan 12 can be made of a metallic material or a composite material of metal and synthetic resin. A stem assembly 20 is inserted and secured in a hole 14 previously drilled in the femur 13 .

The shaft arrangement 20 has a spherical body 21 which is fastened to the upper end region and is preferably made of ceramic. The body 21 is rotatably seated in a concave ven hemispherical surface 12 a of the pan 12 .

Figs. 1 and 3 show a shaft arrangement for künstli che joints according to a first embodiment of the dung OF INVENTION.

The shaft assembly 20 consists of two separate parts, namely a shaft body 22 made of metallic material, such as titanium, and plate-shaped shaft parts (plate) 23 made of a sintered or molded body made of the aforementioned calcium phosphate compound. Each of the shaft parts 23 is firmly embedded in the shaft body 22 at predetermined locations.

As shown in FIG. 1, the shaft body 22 has a spherical body holding portion 22 b and an insert member 22 a. The spherical body holding portion 22 b extends laterally from a lower end portion of the insert 22 a of the shaft body 22 . The insert part 22 a is embedded in a femur 13 (see FIG. 9). Both side surfaces of the insert part 22 a have a recess 24 for receiving and fastening the corresponding shaft part 23 . The plate-shaped shaft part 23 and the recess 24 have corresponding shapes, ie they have essentially the same shape and thickness (shaft part 23 ) or depth (recess 24 ) in plan view. Since each shaft part 23 sits completely in the respective recess 24 of the shaft body 22 , the surface of the shaft arrangement 20 thus obtained is smooth over its entire length. In the illustrated embodiment, an adhesive is used for connecting the shaft part 23 to the recess 24 .

FIGS. 4 and 5 show a shaft arrangement for künstli che joints in a second embodiment of the dung OF INVENTION.

As FIG. 4 shows, there is a shaft assembly 20 in addition to the shaft portions 23 be with reference to FIGS. 1 to 3 were enrolled, from a shank portion 25 which is a of the shaft body 22 fixed to the tip of the insert 22.

Similar to the shaft parts 23 of the first embodiment, the shaft part 25 consists of a sintered or molded body made of the calcium phosphate compound. The shaft part 25 consists of a cylindrical body which is fixed with a pin 26 with head firmly to a tip of the insert part 22 a. The pin 26 with head consists of a shaft 26 a, a screw 26 b and a head 26 c. The shaft 26 a is inserted and positioned in a hollow region of the shaft part 25 . The head 26 c has a larger outer diameter than the shaft 26 a. The screw 26 b and the head 26 c are integrally formed at the two ends of the shaft 26 a.

When screwing the screw 26 b into the insert part 22 a of the shaft body 22 , the shaft part 25 can be firmly attached to the end region of the shaft body 22 and thus forms the shaft arrangement 20 . The screw 26 b can, if desired, also be replaced by a shaft without thread (not shown), which is then attached to the shaft body 22 with adhesive. The shaft assembly 20 obtained with the shaft body 22 and the shaft part 25 attached thereto thus has a smooth surface.

FIGS. 6 to 8 show a shaft arrangement for künstli che joints in a third embodiment of the dung OF INVENTION.

In the third embodiment, a through hole similar opening 27 is formed at a predetermined position in the insert 22 a, which has approximately the shape of a trapezoid. A shaft part (block) 28 separate from the shaft body consists of a sintered or molded body made of the calcium phosphate compound. The shaft part 28 is inserted and fastened in the opening 27 . It can also, as shown in Fig. 6, fixed with pins 30 who the. Since the insert part 22 a and the shaft part 28 have holes 29 and 28 a corresponding to one another, the pins 30 can be inserted into the holes 28 a and 29 and thus the shaft part 28 can be fixed to the shaft body 22 . If a stronger hold is also desired, additional glue to the pins 30 can be introduced into the gap between the wall of the opening 27 and the surface of the shaft part 28 . The he holding shaft assembly 20 with the shaft body 22 and the attached shaft part 25 thus has a smooth upper surface.

Each shaft assembly 20 with the shaft parts 23 described above; 25 or 28 is inserted into the hole that was previously drilled in the femur 13 (see FIG. 9) and fi xed therein. The attachment can be done with conventional fasteners such as glue, mechanical fastening tools or parts or with simple fits. After the end of the joint replacement operation, the bone of the femur 13 can grow gradually and, over time, migrate into the fine pores of the shaft part 23 , 25 or 28 from the calcium phosphate compound. Due to the excellent biocompatibility of the calcium phosphate connection, the shaft part 23 , 25 or 28 can be firmly connected to the femur 13 . Since the calcium phosphate compound is essentially chemically stable, has a low solubility and the shaft part formed from it is formed separately from the shaft body, no erosion (dissolution) of the shaft part takes place after insertion of the shaft arrangement in the bones.

In practice, the manufacture of the shaft parts 23 , 25 and 28 is not restricted. To further understand the invention, the following discussion refers to examples that describe the manufacture of a shaft part as a sintered body and as a shaped body, using hydroxyapatite as the starting material.

example 1

In a conventional wet process, an emulsion of hydroxyapatite is made which is dried in a spray dryer. This gives a hydroxyapatite powder. The powder is pressed in a mold. A pressed sintered body with a length of 45 mm and a diameter of 35 mm is obtained. The pressed sintered body is processed on an NC lathe in order to obtain the desired size and shape corresponding to the shaft part. The product is worked so that its size and shape is slightly larger than that of the shaft part, since the pressed sintered body, ie the processed product, can shrink slightly by calcining. The processed product is then annealed at 1100 ° C for two hours in an electric furnace. This gives the sintered body which is formed into the shaft parts 23 , 25 and 28 of FIGS. 1, 4 and 6.

Example 2

A water solution of phosphoric acid and a suspension of calcium hydroxide react and are dried according to a conventional method. This produces hydroxyapatite with a CA / P ratio of 1.67. The hydroxyapatite obtained is then annealed at a temperature of 1200 ° C and a pressure of 1.3 × 10 ^-4 Pa for one hour. The hydroxyapatite decomposes pyrolytically, and a mixture of tricalcium-α-phosphate and tetrakalzium-α-phosphate is obtained. After pulverization, the powder mixture of tricalcium-α-phosphate and tetrakalzium-α-phosphate is mixed and kneaded with a water solution containing 45% citric acid, 15% glucose and 1% chitosan, the powder / solution ratio being 2 to 1. The kneaded product is poured into two-part polyacetal molds with a drilled cavity corresponding to the shape of the desired shaft part, and hardened therein for about 10 minutes. After curing, the product is removed from the molds. The hardened product has exactly the shape of the shaft part 23 , 25 or 28 .

As can be seen from this discussion, the Shaft assembly of the invention has many advantages. When inserting of an artificial joint, the shaft arrangement can be adjusted with we significantly improved adhesion to the human bone be consolidated because the shaft part is separate, not from the the same material as the shaft body and a gesin terter or molded body from a calcium phosphate Ver is a bond that is chemically stable and has little solubility. Au In addition, the shaft arrangement is inserted into the bone in such a way that at least part of the shaft part on the surface of the Shaft body is exposed and comes into contact with the bone. The excellent hold of the shaft arrangement can be done without Ver deterioration is maintained over a long period of time.

Claims (11)

1. shaft assembly for an artificial joint to be inserted into a bone with a shaft body and a spherical body which is fastened to an end region of the shaft body, and with a receiving part provided in the shaft body for receiving at least one shaft part to be connected to the shaft body, thereby characterized in that at least one shaft part consists of a hardened part made of a calcium phosphate compound, that this at least one shaft part is received and fixed in the receiving part of the shaft body in such a way, and that at least part of the shaft part is exposed on a surface of the shaft body. 2. shaft arrangement according to claim 1, characterized in that that the shaft part is a plate body and the previously trained recess contains the receiving part, wherein the plate body in the previously formed recess of the shaft body is received and fixed. 3. shaft arrangement according to claim 1, characterized in that that the shaft part is a block body and one previously formed through hole is the receiving part, the Block body in the previously formed through hole of the Shaft body is recorded and fixed in it. 4. shaft assembly according to claim 3, characterized in that the block body in the through hole of the shaft body pers with fasteners such as glue, pens or Screws is attached. 5. shaft arrangement according to claim 1, characterized in that the shaft part is a cylindrical body, one end part of the shaft body with a pin with head the up  is receiving part and the cylindrical body at the end part the shaft body is attached. 6. shaft arrangement according to one of the preceding claims, characterized in that it is a smooth overall Has surface. 7. shaft arrangement according to one of the preceding claims, characterized in that the calcium phosphate compound a molar ratio of calcium to phosphorus (Ca / P ratio) of 1.5 to 2.0. 8. shaft arrangement according to one of the preceding claims, characterized in that the calcium phosphate compound at least one element from the group hydroxylapa tit, fluorapatite, primary calcium phosphate, dibasic Calcium phosphate, triphase calcium phosphate and four is basic calcium phosphate. 9. shaft arrangement according to one of the preceding claims, characterized in that the hardened part is sintered is. 10. shaft arrangement according to claim 9, characterized in that the sintered part has a specific gravity of 30 to Has 100%. 11. Shank arrangement according to one of claims 1 to 8, characterized characterized in that the hardened part is a molded part is.