POLYMER FOR JOINT SPACERS, IMPLANTS AND / OR AS A TENDON OR LIGAMENT REPLACEMENT

Description

[0001] The present invention relates to a biocompatible polymer for joint spacers, in particular a knee spacer and a hip spacer, implants and / or as tendon or ligament replacement consisting of a cross-linked polyurethane, wherein the polyurethane is polyurethaneurea or polyurea.

[0002] Osteoarthritis, the premature wear of cartilaginous joint surfaces, affects millions of people worldwide, primarily in the knees and hips. As an alternative to conventional artificial joints (endoprostheses), which are associated with numerous disadvantages, elastic, disc-shaped spacers, so-called "knee spacers," are available for the knee. These can be inserted into the knee cavity through a small skin incision after removal of the (residual) meniscus, smoothing of the joint surfaces, and careful size selection. They replace the worn-down cartilage and damaged meniscus in the joint. The knee spacers restore the natural joint space and can thus also correct angulations, such as X- or O-shaped deformities (valgus, varus) of the leg.

[0003] The natural medial (inner) and lateral (outer) menisci are crescent-shaped fibrocartilage tissues that are wedge-shaped in cross-section and anchored to the tibial plateau via the anterior and posterior horns. They increase the contact area between the tibial plateau and the condyles of the femur (thigh bone).

[0004] Joint spacers generally refer to spacers that can also be used in other joints, such as the hip, shoulder, foot, hand, or vertebrae of the human body. Joint spacers also include so-called "plugs" or flat plugs, which can replace only a small portion of the cartilage surface of a joint. Spacers can also be used as gliding and damping elements for endoprostheses. Knee spacers are distinguished between different designs. The meniscus spacer replaces the meniscus and worn-down cartilage of the joint surfaces, while the meniscus implant replaces only the meniscus. Joint surface replacement or joint surface spacer compensates for partially worn-down cartilage or the beginning of wear of the cartilage of the joint surfaces without replacing the meniscus.

[0005] Knee spacers are known to be made of various materials and polymers. Polyurethanes are particularly well-suited due to their high mechanical strength and high abrasion resistance. Polyurethanes can generally be divided into aromatic and aliphatic polyurethanes. Aromatic polyurethanes typically possess greater mechanical strength and therefore appear better suited to the high loads that occur in a knee spacer during flexion and extension. However, aromatic polyurethanes have the disadvantage compared to aliphatic polyurethanes in that they can "yellow," i.e., exhibit a certain aging effect. Furthermore, aromatic polyurethanes are under discussion because their potential degradation products may pose a carcinogenic risk.

[0006] Knee spacers have not yet become widely accepted because the implants frequently break, slip out of the knee joint space, or cause restricted movement. In particular, no knee spacers with physiological cushioning combined with sufficient mechanical strength and fatigue strength are currently known. However, physiological cushioning is particularly desirable, as it leads to pain relief for the patient.

[0007] From US 6 140 452 A, US 2013 / 218275 A1, US 2007 / 027285 A1, E. Müller: "Rubber-elastic substances" (In: Herrlinger et al.: "Houben-Weyl, Methods of Organic Chemistry", January 7, 1963 (1963-01-07), Georg Thieme Verlag, Stuttgart, XP055481377, Vol. 24 / 2, pages 79-81), Ellegast, Konrad: "Water-crosslinked products" (In: Vieweg et al.: "Plastics Handbook", 1966, Carl Hanser Verlag, Munich, XP055481374, Vol. VII, pages 270-273), ONG ET AL: "New Biomaterials for Orthopedic implants" ("ORTHOPEDIC RESEARCH AND REVIEWS, Vol. 2015-7, September 8, 2015 (2015-09-08), pages 107-130; XP055481290; DOI: https. / / doi.org / 10.2147 / ORR.S63437), JONES E ET AL: "Compliant-layer tibial bearing inserts: Friction testing of different materials and designs for a new generation of prostheses that mimic the natural joint", (PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS.JOURNAL OF ENGINEERING IN MEDICINE. PART H, MECHANICAL ENGINEERING PUBLICATIONS LTD, LONDON, UK, Vol. 222, No.8, January 2008 (2008-01), pages 1197-1208, XP009505574, ISSN: 09954-4119; DOI: 10.1243 / 09544119JEIM442), "PUR Elastomers", XP055481270, Found on the Internet: . URL:http: / / www.mattec.atZPolyurethaninfo.htm, DE 102 43 966 A1 and WO 98 / 20939 A2 disclose further materials that are used in particular for joint spacers.

[0008] The object of the present invention is to create a polymer for a durable, sufficiently dampened, and abrasion-resistant joint spacer that can absorb even very high localized loads. Joint spacers made from the polymer should also achieve the highest possible congruence between the articulating joint surfaces and be unable to slip out of the joint space. The polymer should also be suitable for implants and / or as a tendon or ligament replacement.

[0009] This object is achieved by the biocompatible polymer according to claim 1. According to the invention, a crosslinking reagent which contains at least a portion of water is used to crosslink the polyurethane.

[0010] Such a polymer, especially for a joint spacer, advantageously exhibits a pronounced progressive compression-compression behavior. With increasing compression, elasticity decreases disproportionately, and the polymer thus becomes harder. In other words, the material is relatively soft in terms of its Shore hardness and simultaneously possesses a relatively high modulus of elasticity perpendicular to the compression.

[0011] The polymers described are also suitable for other implants in the human body, such as vessels, heart valves, and other valves in the human body, as well as pump membranes and chambers in artificial hearts and cardiac assist systems. They are also suitable for ophthalmic implants such as intraocular lenses or artificial corneas.

[0012] Preferred embodiments of the invention are described in the subclaims and below.

[0013] According to a first advantageous embodiment, the crosslinking reagent comprises one or more chain extenders. Furthermore, the crosslinking reagent preferably comprises one or more crosslinking reagents.

[0014] Shore hardness is often used in connection with the selection of suitable materials or polymers for joint spacers. The very high loads that occur in joints, especially in the knee and hip, can only be absorbed by materials with Shore A hardnesses above 85, among the known materials suitable for medical technology. However, to ensure high congruity and cushioning, and ultimately pain relief for the patient, joint spacers made of such materials would be too hard in the knee and therefore less suitable. The softer the joint spacer, the larger the contact area between the joint spacer and the joint surface, and the lower the tension and thus the wear in the joint spacer. Ideally, the joint spacer should approximate the compliance of natural articular cartilage. This includes the weakened arthritic articular cartilage, so that it cannot be further damaged by the implant, if possible.The desired Shore A hardness of the material is between 20 and 77, preferably between 45 and 72. For very heavy people, depending on the size of the tibial surface or the joint spacer from approximately 100-120 kg, the Shore A hardness of the material can be up to 85. The materials primarily considered for this purpose are elastomers or thermoplastic elastomers. The known flexible polymers and other materials in this hardness range cannot build up sufficient tension under higher deformations to withstand the forces occurring in the joints, i.e. the load-bearing capacity of the bearing material is insufficient. However, series of tests have shown that materials that exhibit a pronounced progressive compression-compression behavior are suitable for joint spacers.Materials of the same Shore A hardness can have very different elastic moduli, and in particular, they can develop different levels of stress under a given strain or compression. In other words, the material will compress more or less under a given load, regardless of the same Shore A hardness.

[0015] Materials, particularly elastomers and thermoplastic elastomers, can soften when exposed to elevated temperatures, after absorption of water and prolonged storage in water for several months, or after repeated loading (load-induced softening or so-called Mullins effect) (Geary C et al. Characterisation of Bionate polycarbonate polyurethanes for orthopaedic applications. J Mater Sci: Mater Med 19 (2008) 3355-3363). In addition, sterilization can change the mechanical properties. Furthermore, materials can harden at very high test speeds. The parameters specified in this invention therefore refer to test conditions of the samples in a conditioned state at 37°C, after absorption of water or synovial fluid and at the usual test speeds of the relevant standards and in a sterilized state. The stress values ​​are preferably determined after the 5thCycle values ​​are determined to compensate for the Mullins effect, as the magnitude of the hysteresis can change significantly, especially during the first few cycles. Furthermore, the previously specified values ​​should be reached or exceeded even after at least 5 months of storage in water. The materials should therefore be as hydrolytically stable as possible. More generally, the materials used should retain their parameters even after prolonged implantation in the body.

[0016] The polymer therefore preferably consists at least partially of a material, in particular an elastomer or thermoplastic elastomer with a Shore A hardness between 20 and 77 and tensile stress values ​​at elongation between 20% and 60%, preferably at 50% (hereinafter also referred to as 50% tensile stress), greater than 3.8 N / mm 2< , preferably greater than 4.6 N / mm 2< and particularly preferably greater than 6 N / mm 2< , and / or a Shore A hardness up to 85 and tensile stress values ​​at elongations between 20% and 60%, preferably at 50%, greater than 6 N / mm 2< , preferably greater than 7 N / mm 2< and particularly preferably greater than 8 N / mm 2< . It should be noted here that the stress value at a certain elongation does not mean the tangent or secant modulus. The material should also preferably not have any flow behavior up to 50% elongation, preferably up to 70% elongation.

[0017] Preferably, the material has a Shore A hardness between 20 and 77 tensile stress values ​​at 100% elongation (100% tensile stress) of at least 5 N / mm 2< , preferably at least 6 N / mm 2< and particularly preferably at least 7.5 N / mm 2< , or with a Shore A hardness up to 85 tensile stress values ​​at 100% elongation of at least 7.5 N / mm 2< , preferably at least 8.5 N / mm 2< and particularly preferably at least 10.5 N / mm 2<.

[0018] A further characteristic for suitable materials is the compressive stress, even if the damage to the material is caused significantly more by the tensile stresses that occur. The polymer therefore preferably also consists at least partially of a material with a Shore A hardness between 20 and 77 and compressive stress values ​​at compression between 20% and 60%, preferably at 50% (hereinafter also referred to as 50% compressive stress), greater than 7.8 N / mm 2< , preferably greater than 9 N / mm 2< and particularly preferably greater than 10.5 N / mm 2< , and / or a Shore A hardness up to 85 and compressive stress values ​​at compression between 20% and 60%, preferably at 50%, greater than 10.5 N / mm 2< , preferably greater than 12 N / mm 2< and particularly preferably greater than 14 N / mm 2<.

[0019] The stress values ​​mentioned above can also be achieved at lower strain or compression values ​​than those mentioned, even if the polymer or the joint spacer is then not compressed as much under the same loads.

[0020] As previously indicated, softer materials are generally unable to withstand the stresses encountered in joints. In addition to the tensile stress values ​​at 50% or 100% elongation and the 50% compressive stresses described above, tear strength is another important material parameter. The softer the material, the higher the tear strength should ideally be; in other words, it should be inversely proportional to the Shore A hardness. Reference values ​​for this relationship are: for a Shore A hardness of 55, the tear strength should be greater than 60 N / mm (preferably greater than 70 N / mm), and for a Shore A hardness of 75, the tear strength should be greater than 35 N / mm (preferably greater than 40 N / mm). These reference values ​​should provide a linear progression across the Shore A hardness ranges. The tear strength values ​​refer to specimen shapes according to the "Trouser Tear Test."

[0021] Biocompatible, elastic, and durable polymers are suitable materials for the joint spacers, and as already mentioned, polyurethanes are particularly suitable. Furthermore, the polymers should be as free as possible from low-molecular-weight components, which increases the desired 50% stress values ​​and thus leads to the preferred properties.

[0022] Polyurethanes are characterized by the interplay of hard segments (formed from an isocyanate with low-molecular-weight chain extenders) and soft segments (of higher molecular weight). Depending on their composition, polyurethanes exhibit very different material behavior, particularly in their stress / strain curves.

[0023] Isocyanates are widely described in the literature and, in principle, can all be used. However, compact, slightly branched, and high-melting isocyanates such as cyclohexane diisocyanate (CHDI), naphthalene-1,5-diisocyanate (NDI), or paraphenylene diisocyanate (PPDI) are preferred. Linear, symmetrical isocyanates such as hexamethylene diisocyanate (HDI) are also suitable. Such starting components further promote progressive compression behavior, which results in the aforementioned advantages. Furthermore, these isocyanates are particularly well-suited for dynamic applications. The weight fractions of these isocyanates are up to 50%, preferably 3%-30%, of the polymers. These preferred isocyanates can also be mixed with other aromatic or aliphatic isocyanates. Polyisocyanates can also be added to the aforementioned diisocyanates or diisocyanate mixtures.

[0024] According to a preferred embodiment of the present invention, the polyurethane mixture comprises at least partially trans-1,4-cyclohexane diisocyanate (CHDI), cis-CHDI, or mixtures thereof. Trans-CHDI is particularly preferred because it gives the polymer particularly high crystallinity and thus the preferred properties. CHDI also leads to the favored aliphatic polyurethanes. Furthermore, the polyurethane mixture consists at least partially of other aliphatic isocyanates, in particular dicyclohexylmethane diisocyanate (H12MDI) or an isomer mixture thereof, or even a mixture of CHDI and H12MDI.

[0025] Below, a number of formulations or components are given, each of which advantageously leads to the preferred properties.

[0026] To achieve the desired progressive compression-compression behavior of polyurethanes with high stress values ​​at 50% elongation or compression and low Shore A hardness, the soft segments are crucial. Hydrolysis-resistant and biostable soft segments based on polyolefins, such as polyisobutylene (PIB) or polybutadiene (PB), are preferred for the polymer. Furthermore, soft segments based on polycarbonate (PC) and polydimethylsiloxane (PDMS) are also considered relatively hydrolysis-resistant. Typical polyester or polyether urethanes known from the literature or commercially, including medical grade ones, are not sufficiently biostable for long-term implants and are therefore less suitable or not preferred for the polymer, even if they can be added in relatively small amounts. Silicone-ether-polyurethane copolymers also appear to have insufficient biostability.

[0027] According to a preferred embodiment of the present invention, the soft segment of the polymer is a polyisobutylene (PIB) or a bifunctional polyisobutylene, preferably a hydroxyl-terminated (HO-PIB-OH) or an amine-terminated (H 2 N-PIB-NH 2 ) polyisobutylene.

[0028] In another preferred embodiment, the soft segment is polybutadiene (PB), preferably OH-terminated and particularly preferably OH-terminated hydrogenated polybutadiene. However, amine-terminated polybutadienes can also be used.

[0029] The advantageous properties of the polymer are particularly high when the soft segment consists exclusively of a PIB or PB or even of a mixture of these two soft segments.

[0030] The polyurethane types of the biocompatible polymer are cross-linked. Water is the preferred cross-linking agent for achieving the desired properties. However, other cross-linking agents, such as trivalent glycol or other polyvalent cross-linking agents known from polyurethane chemistry, can be used.

[0031] Preferred isocyanates for water-based crosslinking are HDI, NDI, PPDI, or CHDI. Preferred soft segments, in addition to the previously mentioned preferred soft segments PIB and PB, are also polycarbonatediol (PCD) and, optionally, butanediol (BD) or one or more other chain extenders as a chain extender. However, it is preferable to omit an additional chain extender, using only water for crosslinking.

[0032] For polyurethanes based on polycarbonatediols, polyhexamethylene carbonatediol (C6-PCD) is commonly used in medical technology. These are composed exclusively of six methylene groups (CH2). However, in order to achieve softer polyurethanes while at the same time achieving the advantageous material properties that are particularly well suited to the polymer, polycarbonatediol copolymer types (polyalkylene carbonatediols) are used instead of a homogeneous C6-PCD, which are composed of the units hexane (C6), pentane (Cs), butane (C4) or propane (Cs). The copolymer types preferably consist of combinations with C6 / C5 or C6 / C4 or C4 / C3 units, expressed in the chemical formula with i.e., with n=6 or 5; or n=6 or 4; or n=4 or 3. Furthermore, the copolymer types with a decreasing number of methylene groups exhibit significantly better abrasion behavior.

[0033] A preferred formulation therefore provides that the polymer of the joint spacer contains at least partially polycarbonate diol copolymers.

[0034] Particularly preferred components of the polyurethane system are, as already stated, the isocyanates HDI, CHDI, PPDI, or NDI, and polyolefins, preferably PIB or PB and PCD, as soft segments. For PCD, the aforementioned polycarbonatediol copolymer types are preferably used. In this case, the polyolefin types PIB or PB can be mixed or, in particular, mixed with the PCD to achieve particularly abrasion-resistant polyurethane types. The proportion of PCD in the total soft segment content is up to 80%, preferably 5 to 40%. The soft segments can also be mixed with other known soft segments, such as, in particular, polydimethylsiloxane (PDMS) or polytetramethylene oxide (PTMO). The addition of polydimethylsiloxane-polycaprolactone block copolymers is also suitable for achieving the advantageous properties. The proportions of these soft segments in the total soft segment content are up to 50%, preferably 3 to 35%.

[0035] A further advantageous formulation provides that the polymer of the joint spacer contains as soft segments exclusively hydroxyl- and / or amine-terminated polyisobutylene, and / or hydroxyl- and / or amine-terminated and preferably hydroxyl-terminated hydrogenated polybutadiene, and / or polycarbonatediol.

[0036] The aforementioned amine- or hydroxyl-terminated PIBs can also be linear or branched PIBs. Copolymers such as acrylonitrile-butadiene-styrene can also be used for polybutadienes.

[0037] Furthermore, the above-mentioned isocyanates can also be mixed with other aromatic or aliphatic or cycloaliphatic isocyanates, such as 3,3'-dimethyl-4,4'-biphenylene diisocyanate (TODI).

[0038] In addition, in the formulations shown above, the chain extenders mentioned can also be introduced into the polymer synthesis in combination with two or more chain extenders and / or crosslinking reagents (e.g. glycol).

[0039] With the previously described material configurations, i.e. depending on the exact composition of the individual components, 50% tensile stresses of up to 20 N / mm 2 can be achieved in the Shore A hardness ranges mentioned.

[0040] To improve sliding properties or reduce the coefficient of friction, the polyurethane mixture may also contain polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), or other hydrophilic polymers or suitable substances. The proportion of these substances is less than 10%, preferably less than 3%.

[0041] Particularly in the case of knee spacers, the central region of the joint spacer is subjected to considerable stress due to the convexity of the femoral condyles. However, literature and patents describe knee spacers with a softer central region and a harder edge region. However, plastics tend to creep, causing the central region of the joint spacer to "iron out" under continuous load, i.e., become wavy in the center or develop wrinkles, which can lead to distortion and dislocation of the joint spacer. Furthermore, the edge regions can absorb less and less load over time. To obtain a joint spacer with the preferred damping properties (compliance), in another embodiment, a harder material is preferably arranged in the center and softer material in the edge regions of the joint spacer.A meniscus spacer is designed so that the softer peripheral areas are loaded first by the femur, followed by the harder central area, thus achieving progressive compression and compression behavior. The femoral side of the meniscus spacer is more concave than the convexity of the femur, meaning that upon contact, the peripheral areas of the meniscus spacer are first contacted by the femur.

[0042] Preferably, the previously outlined harder or softer materials with the corresponding 50% tensile or compressive stress values ​​are used. However, this design can also be constructed from known polyurethanes. For example, a material with the lower 50% tensile or compressive stress values ​​of the Shore A hardness range up to 77 can be used as a hard material, preferably with a Shore A hardness range between 78 and 85. Furthermore, a material with lower 50% tensile or compressive stress values ​​than those specified in the Shore A hardness range of 20-77 can be used as a soft material for the edge area. The soft areas preferably extend in a wedge shape from the edge of the meniscus spacer to the center and are embedded on both sides by the hard material, with only the hard material present in the center.The deformation of the soft edge areas and thus the preservation of the recovery of these areas are limited by the central hard area, which absorbs the full load.

[0043] Furthermore, the joint spacer can have a layered structure with at least three layers, namely two cover layers and a core layer arranged between them. The core layers and the cover layer are made of materials of different hardness, with the core layer preferably consisting of a comparatively harder layer and the cover layers of a comparatively softer layer. The relatively soft edge regions are preferably dimensioned in such a way that these areas are initially loaded by a condyle, whereby the joint spacer initially exhibits exceptionally high compliance. With increasing compression of the flexible edge regions, the joint spacer behaves more rigidly due to the comparatively harder core layer (progressive compression-compression behavior).

[0044] Preferably, the difference in Shore hardness between the cover and core layers is greater than 5 and preferably between 10 and 25. The harder core layer preferably consists of a polymer with a Shore A hardness of 78 to 90, preferably 80 to 84. In contrast, the cover layers have a Shore A hardness between 20 and 77 and preferably between 40 and 70. The hard and soft layers, respectively, have 50% tensile or compressive stress values ​​as in the embodiment previously described with a soft edge.

[0045] One of the two soft cover layers, especially the distal one, which in the case of a knee spacer faces the tibia (shinbone), can be omitted, preferably if the knee spacer is fixed to the tibia. The advantage of the additional soft layer, however, is that it can better adapt to the patient's individual joint topography. It should also be noted that the progressive compression / compression behavior can generally also be achieved if the core layer is soft and the cover layers are hard.

[0046] Furthermore, the material designs and sandwich structures embodied in this invention can also be used for other joint spacers, which can be used in other joints internally (intervertebral discs, shoulder, foot, and hand) or externally as orthoses of the human body. They can also be used for joints in animals, such as horses. In harder versions, the materials are also suitable as tendon or ligament replacements, such as cruciate ligaments in the knee joint.

[0047] Specific configurations and further preferred embodiments of the present invention are explained below with reference to the diagram and the figure. They show: Diagram: Stress-strain curves, Fig. 1a: Tibia and femur of a left knee with medial (left) and lateral (right) meniscus spacer and Fig. 1b, c: a lateral view of a slightly flexed knee from lateral (b) and in frontal view (c),

[0048] The abbreviations used below mean the following: anterior pposterior Inner side of a knee spacer, close to the center of the knee Outer side of a knee spacer

[0049] Diagram 1 shows the characteristic range of the tensile stress / strain curves for the preferred materials. It specifically shows the 50% tensile stress values ​​for materials in the Shore A hardness range of 20-77, which should be greater than 3.8 N / mm², preferably greater than 4.6 N / mm², and most preferably greater than 6 N / mm². The diagram also illustrates a stress curve with yield behavior that should be avoided unless the yield point would reach very high values ​​greater than 10 N / mm². The S-curve ("S-curve") illustrates that a suitable material with sufficient 50% tensile stress can exhibit much lower elastic moduli and tensile stress values ​​at strains below 50% than in the other curves shown.

[0050] The Fig. 1a-c show different perspective views of a (left) knee joint 10 as well as parts of a thigh 12 (femur) and a lower leg 13 (tibia). Meniscus spacers 15, 15' are arranged between the joint surfaces 14, 14', replacing the worn and damaged (natural) meniscus. To protect the material of the meniscus spacer 15, 15', the forces to be transmitted must be distributed over the largest possible load-bearing surface. The shape, in particular the edge contour of a knee spacer 15, 15' projected onto the tibial plateau 14, therefore plays a central role. The highest loads occur when the leg is almost fully extended, as in Fig. 1bis indicated. In this slightly flexed position, the stress in the anterior half of a knee spacer 15, 15' is highest due to the femoral condyle rising posteriorly relative to the tibial plateau 14 and the resulting widening gap 16. Furthermore, the contact surface of the tibial plateau 14 narrows from anterior to posterior due to a depression (the area intercondylaris posterior). The posterior half of the contact surface serves primarily to roll the condyles 17, 17' in more flexed positions, where lower loads occur.

Claims

1. Biocompatible polymer for joint spacers, implants and / or as a tendon or ligament replacement, consisting of a crosslinked polyurethane, the polyurethane being polyurethaneurea or polyurea, characterized in that a crosslinking reagent is used to crosslink the polyurethane, which contains at least a proportion of water.

2. Biocompatible polymer according to claim 1, characterized in that the crosslinking reagent comprises one or more chain extenders.

3. Biocompatible polymer according to one of claims 1 or 2, characterized in that the crosslinking reagent comprises one or more crosslinking reagents.

4. Biocompatible polymer according to one of claims 1 to 3, characterized in that the polymer consists at least partly of a material with tensile stress values at elongations between 20% and 60%, preferably at 50%, greater than 3.8 N / mm2, preferably greater than 4.6 N / mm2 and particularly preferably greater than 6 N / mm2, and / or compressive stress values at compressions between 20% and 60%, preferably at 50%, greater than 7.8 N / mm2, preferably greater than 9 N / mm2 and particularly preferably greater than 10.5 N / mm2.

5. Biocompatible polymer according to one of claims 1 to 4, characterized in that the polymer exclusively contains hydroxyl- and / or amine-terminated polyisobutylene and / or hydroxyl- and / or amine-terminated and preferably hydroxyl-terminated hydrogenated polybutadiene as soft segments.

6. Biocompatible polymer according to one of claims 1 to 5, characterized in that a) that the polymer contains as soft segments polyisobutylene and / or polybutadiene and a polycarbonate diol and preferably a polycarbonate diol copolymer type with a proportion of the polycarbonate diol in the total soft segment proportion of up to 80%, preferably 5 to 40%, and / or b) that the soft segment or mixture of soft segments of the polymer contains the soft segments polydimethylsiloxane or polytetramethylene oxide or polydimethylsiloxane-polycaprolactone block copolymers or a mixture of one or more of these soft segments, with a proportion of one or more of these soft segments in the total soft segment proportion of up to 50%, preferably from 3 to 35%.

7. Biocompatible polymer according to one of claims 1 to 6, characterized in that the polyurethane consists at least partly of naphthalene-1,5-diisocyanate and / or para-phenylene diisocyanate and / or trans-1,4-cyclohexane diisocyanate and / or hexamethylene diisocyanate.

8. Biocompatible polymer according to one of claims 1 to 7, characterized in that the polymer is formed as a joint spacer, wherein a) the edge zone of the joint spacer consists at least partly of a material with a Shore A hardness between 20 and 77 and the material of the central (harder) region has a Shore A hardness greater than 77 with tensile stress values at elongations between 20% and 60%, preferably at 50%, greater than 3.8 N / mm2, preferably greater than 4.6 N / mm2 and particularly preferably greater than 6 N / mm2, and / or compressive stress values at compression between 20% and 60%, preferably at 50%, greater than 7.8 N / mm2, preferably greater than 9 N / mm2 and particularly preferably greater than 10.5 N / mm2, or b) the joint spacer has an at least partially layered structure with at least three layers, namely at least two cover layers and a core layer arranged between them, which consist of materials of different hardnesses, the difference in Shore A hardnesses between the cover and core layers being greater than 5 and preferably between 10 and 20 and at least one of the layers consisting of a material with tensile stress values at elongations of between 20% and 60%, preferably at 50%, greater than 3.8 N / mm2, preferably at 50%, preferably at 3.8 N / mm2 and particularly preferably greater than 10.5 N / mm2, or preferably at 50%, greater than 3.8 N / mm2, preferably greater than 4.6 N / mm2 and particularly preferably greater than 6 N / mm2 and / or compressive stress values at compression between 20% and 60%, preferably at 50%, greater than 7.8 N / mm2, preferably greater than 9 N / mm2 and particularly preferably greater than 10.5 N / mm2.