WRIST ENDOPROSTHESIS

Abstract

A wrist endoprosthesis (2) for functional replacement of the human wrist, containing a radius component (4) that has a shaft (10) for anchoring in the radius, a head (12), and a first joint surface (16), which is implemented on a distal head face (14), and a carpal component (6) that has a proximal carpal face (22), a distal carpal face (20) and a second joint surface (24) which is formed on the proximal carpal face (22) and interacts with the first joint surface (169) of the radius component (4), characterized in that the carpal component (6) is substantially trough-shaped, in order to at least partially surround the carpal bones. Also, a wrist endoprosthesis (2) that has anti-luxation protection (8), a method for producing wrist endoprostheses (2) and a computer program product.

Claims

1. A wrist endoprosthesis (2) for functional replacement of the human wrist, comprising: a radius component (4) that has a shaft (10) for anchoring in the radius, a head (12), and a first joint surface (16), which is formed on a distal head face (14), and a carpal component (6) that has a proximal carpal face (22), a distal carpal face (20) and a second joint surface (24), which is formed on the proximal carpal face (22) and interacts with the first joint surface (16) of the radius component (4), wherein the carpal component (6) is substantially trough-shaped in order to at least partially surround the carpal bones.

2. The wrist endoprosthesis (2) according to claim 1, wherein the carpal component (6) comprises a carpal cavity (18) which is open to the distal carpal face (20).

3. The wrist endoprosthesis (2) according to claim 2, wherein the carpal cavity (18) has a maximum clear width (W2) measured in the sagittal plane (E2), wherein a corresponding clear width (W1) of the carpal cavity (18) at a distal end (106) the carpal component (6) is less than the maximum clear width (W2).

4. The wrist endoprosthesis (2) according to claim 1, wherein the carpal component (6) comprises one or two lateral openings (28, 32) which are formed in a face (26, 30) parallel to the sagittal plane (E2).

5. The wrist endoprosthesis according to claim 1, wherein the carpal component (6) tapers parallel to a frontal plane (E1) in the direction of the distal carpal face (20).

6. The wrist endoprosthesis (2) according to claim 1, wherein a proximal end (108) of the carpal component (6) is implemented as a thickening (110).

7. The wrist endoprosthesis (2) according to claim 1, wherein the wrist endoprosthesis (2) comprises luxation protection (8).

8. The wrist endoprosthesis (2) according to claim 7, wherein the luxation protection (8) comprises a band (34) which connects the carpal component (6) and the radius component (4).

9. The wrist endoprosthesis (2) according to claim 8, wherein the radius component (4) comprises a tunnel (36) extending from a dorsal face (64) of the radius component (4) to a palmar face (66) of the radius component (4), wherein the band (34) runs through the tunnel (36).

10. The wrist endoprosthesis (2) according to claim 1, wherein a first material forming the wrist endoprosthesis (2) is an isoelastic material, preferably a thermoplastic material, particularly preferably PEEK.

11. A wrist endoprosthesis (2) for partial functional replacement of the human wrist, comprising: a carpal component (6) that has a proximal carpal face (22), a distal carpal face (20) and a second joint surface (24), which is disposed on the proximal carpal face (22) and formed to interact with a distal joint surface of a human radius, wherein the carpal component (6) is substantially trough-shaped in order to at least partially surround the carpal bones.

12. The wrist endoprosthesis (2) according to claim 11, wherein the proximal carpal face comprises a thickening (110) which is implemented as a convex elevation.

13. A method for producing a wrist endoprosthesis (2), particularly a wrist prosthesis (2) according to claim 1, the method comprising the steps: a) providing or producing a non-individualized 3D model of a wrist endoprosthesis; b) acquiring data material, particularly x-ray images, magnetic resonance tomography data, ultrasound images and/or computed tomography data, of a wrist of a patient to be treated; c) determining one or more parameters from the data material for approximating an approximated joint structure of the patient from the data material; d) individualizing the non-individualized 3D model based on the derived parameters for obtaining an individualized 3D model; and e) producing the wrist endoprosthesis (2) by means of an additive manufacturing process based on the individualized 3D model.

14. The method according to claim 13, wherein the parameter represents at least one geometric shape of a recess of a ligamentous connection between adjacent carpal bones of the proximal carpal row of the wrist to be treated, and wherein the individualized 3-D model (174) comprises an elevation (178a, 178b, 178c) corresponding to the recess of the ligamentous connection on a face (176) facing the anatomy.

15. The method according to claim 14, further comprising: providing a surface structuring on at least one surface segment of the anatomy-facing face (176) of the individualized 3D model (174), wherein the production of the wrist endoprosthesis (2) takes place based on the individualized 3D model with surface structuring.

16. The method according to claim 15, wherein a second parameter represents a shape and position of a cartilage-covered joint surface of the wrist to be treated, a third parameter represents a shape and position of a cartilage-free surface of the wrist to be treated, and wherein the individualized 3D model (174) on the anatomy-facing face (176) comprises a first connecting surface corresponding to the cartilage-covered joint surface and a second connecting surface corresponding to the cartilage-free surface.

17. The method according to claim 16, wherein the surface structuring comprises first structural elements on the first connecting surface at least in segments and second structural elements on the second connecting surface at least in segments, which second structural elements are different from the first structural elements.

18. The method according to claim 17, wherein the first structural elements are structural elements protruding from the first connecting surface.

19. The method according to claim 18, wherein the first structural elements are rhombuses, rectangles, triangles, circular structures, ellipses, polygons and/or ribs.

20. The method according to claim 17, wherein the second structural elements are pores in the second connecting surface.

21. The method according to claim 13, wherein the wrist endoprosthesis (2) allows an independent and/or externally controlled unfolding.

22. The method according to claim 13, wherein in the event that step b) is not possible, at least one of the following steps is carried out: acquiring data material, particularly x-ray images, magnetic resonance tomography data, ultrasound images and/or computed tomography data, of the second wrist of a patient; and/or providing data from a statistical comparison group.

23. The method according to claim 13, comprising: providing or creating a 3D instrument model of one or more surgical instruments based on the individualized 3D model of the wrist endoprosthesis and/or the data material; and producing the surgical instrument based on the 3D instrument model.

24. The method according to claim 13, wherein a first material used for producing the wrist endoprosthesis (2) is an isoelastic material, preferably a plastic, particularly preferably PEEK.

25. A method for producing a wrist endoprosthesis (2), particularly a wrist prosthesis (2) according to claim 1, wherein the method comprises the steps: a) providing or producing a non-individualized 3D model of a wrist endoprosthesis; b) acquiring data material, particularly x-ray images, magnetic resonance tomography data, ultrasound images and/or computed tomography data, of a wrist of a patient to be treated; c) creating a patient-specific 3D model of at least one anatomy segment of the wrist to be treated using the data material; d) deriving a negative shape (182) of the anatomy segment of the wrist to be treated; e) adapting an anatomy-facing face of the non-individualized 3D model to the derived negative shape (182) of the anatomy segment of the wrist to be treated for obtaining an individualized 3D model; and f) producing the wrist endoprosthesis (2) by means of an additive manufacturing process based on the individualized 3D model.

26. A computer program product comprising code means which, when executed on a computer, are implemented to execute at least one of the steps of the method defined in claim 13.

Description

[0045] Further advantages, features and details of the invention emerge from the following description of the preferred embodiment and with reference to the drawings; these show:

[0046] FIG. 1 an isometric view of the wrist endoprosthesis that has the luxation protection attached;

[0047] FIG. 2 an isometric view of the radius component;

[0048] FIG. 3 a section of the radius component along the frontal plane;

[0049] FIG. 4 a section of the radius component along the sagittal plane;

[0050] FIG. 5 an isometric view of the carpal component;

[0051] FIG. 6 a section of the carpal component in the sagittal plane;

[0052] FIG. 7 a section of the wrist endoprosthesis along the sagittal plane;

[0053] FIG. 8 a flow diagram illustrating the method for producing a wrist endoprosthesis;

[0054] FIG. 9 a dorsal view of the human bones of the right forearm;

[0055] FIG. 10 a view of the human radial bone in the sagittal plane;

[0056] FIG. 11 an anterior-posterior view of the bone structure of a human wrist;

[0057] FIG. 12 a view of the bone structure of a human wrist in a sagittal plane; and

[0058] FIG. 13a-13c schematic views illustrating an individualized 3D model of a wrist endoprosthesis.

[0059] According to the present embodiment example (FIG. 1), a wrist endoprosthesis 2 comprises a radius component 4, a carpal component 6 and luxation protection 8 as main elements. The radius component 4 is formed here by a shaft 10 and a head 12. A first joint surface 16 is disposed on a distal head face 14. The carpal component 6 is formed trough-shaped and preferably comprises a carpal cavity 18. In the present embodiment, the trough shape of the carpal component 6 is formed by the carpal cavity 18. The carpal cavity 18 is open to a distal carpal face 20. A second joint surface 24 is disposed on a proximal carpal face 22 which is opposite the distal carpal face 20. In the present embodiment example, there is contact between the first joint surface 16 and the second joint surface 24. It should be understood that wrist endoprostheses 2 that have a distance between the first joint surface 16 and the second joint surface 24 are also preferred. The carpal component 6 has a first lateral opening 28 on a radius face 26. The carpal component 6 comprises a second lateral opening 32 on an ulnar face 30 opposite the radius face 26.

[0060] According to the present embodiment example, the wrist endoprosthesis 2 comprises luxation protection 8 which is formed by a band 34 which connects the radius component 4 and the carpal component 6. The band 34 runs through a tunnel 36 formed in the radius component. The carpal component 6 is preferably disposed in the direction of the central axis ZA on the distal head face 14. In the embodiment described, the central axis ZA runs from a proximal shaft end 38 to the distal head face 14. A second central axis ZA2 of the carpal component 6 is congruent to the central axis ZA in the present embodiment example. It should be understood that the central axis ZA and the second central axis ZA2 are at a distance and/or can include an angle with one another. A first maximum width B1 of the radius component, measured parallel to the frontal plane E1, is preferably greater than or equal to a corresponding second maximum width B2 of the carpal component 6. The second maximum width B2 preferably has a range from 70% to 100%, preferably 85% to 100%, particularly preferably 90% to 95% of the first maximum width B1. In the exemplary embodiment shown, the luxation protection 8 applies a restoring force F, which causes contact between the first joint surface 16 and the second joint surface 24. However, it should be understood that luxation protection 8 is also preferred which does not apply any restoring force in a rest position. For example, the band 34 of the luxation protection 8 could be implemented as a rigid band that counteracts longitudinal expansion.

[0061] Referring now to FIG. 2, the radius component 4 of the present embodiment will be explained. The shaft 10 of the radius component 4 is implemented to be implanted in a radius of a patient. The head 12 protrudes from a distal end of the radius. In the preferred embodiment, the head 12 extends in the direction of the central axis ZA from the shaft 10 to the first joint surface 16. The head 12 is connected to the shaft 10 at a connecting segment 40. The connecting segment 40 is preferably implemented as an edge 42. It should be understood that rounded and/or continuous connecting segments 40 are also preferred. In the embodiment shown, the connecting segment 40 is substantially circular in a plane perpendicular to the central axis ZA. Substantially oval or egg-shaped connecting segments 40 are also preferred.

[0062] A thickness D1 on a radius face 44 of the radius component 4, measured in the direction of the central axis, is greater than a thickness D2 on an ulnar face 46. In the embodiment shown, the first joint surface 16 merges directly into the shaft 10 on the ulnar face 46 and the thickness D2 disappears. However, thicknesses D2 of the head 12 in the region of the ulnar face 46 which are greater than zero are also preferred. In the frontal plane E1 (see FIG. 1), a tangent TG1 to the first joint surface 16 includes an angle α with a plane perpendicular to the central axis ZA. The angle α has a range from 0° to 60°, preferably 0° to 45°, particularly preferably 15° to 20°. Negative angles α are also preferred, so that the thickness D2 is greater than the thickness D1. The first joint surface 16 can preferably also comprise planar segments. In the embodiment shown, the first joint surface 16 is implemented substantially oval, so that the width B1 is greater than a third width B3 of the joint surface 16 that is perpendicular to the first width B1.

[0063] The tunnel 36 comprises a first access 50 at the head 12 of the radius component 4. According to the present embodiment example, the first access 50 is disposed on the dorsal face 64 of the radius component 4. A second access 51 is preferably disposed on the palmar face 66 of the radius component 4. The second access 51 is preferably mirrors symmetrical to the first access 50 in the frontal plane. In the embodiment shown, the first access 50 has a cross section in the form of an elongated hole. The narrow faces 52, 54 of the first access 50 are closed by semicircles 56, 58. The long faces 60, 62 of the first access 50 are parallel and larger than the narrow faces 52, 54. Here, a width B4 of the band 34 is less than a length of the long faces 60, 62 and/or a thickness D3, measured perpendicular to the width B4, of the band 34 is less than a length of the narrow faces 52, 54. Round, oval and/or rectangular cross sections of the first access 50 and/or second access 51 are also preferred. The accesses 50, 51 can be rounded in order to minimize the loads on the band 34. The first access 50 and the second access 51 are preferably disposed completely on the head 12 of the radius component 4. In the embodiment shown, the first access 50 directly adjoins the connecting segment 40 in the direction of the distal head face 14. It should be understood that embodiments are also preferred in which the first access 50 is implemented at a distance from the connecting segment 40 in the direction of the central axis ZA. The first access 50 particularly preferably has a smaller distance from the connecting segment 40 in the direction of the central axis ZA than from the first joint surface 16.

[0064] According to the present embodiment example, the shaft 10 tapers continuously in the direction of the central axis ZA towards the proximal shaft end 38. Embodiments that have a shaft 10 alternately tapering and widening in the direction of the proximal shaft end are also preferred. In the embodiment shown, the proximal shaft end 38 is shown flattened. Pointed and/or rounded proximal shaft ends 38 are also preferred. According to the present embodiment example, a lateral surface 70 of the shaft 10 is implemented continuously. The shaft 10 can preferably be implemented to be rotationally symmetrical to the central axis ZA. The shaft 10 preferably has a length L1, measured along the central axis ZA between the connecting segment 40 and the proximal shaft end 38, in a range from 10 mm to 150 mm, particularly preferably 50 mm to 100 mm. A thickness D4 of the head 12 adjoining the length L1 along the central axis ZA has a range from 0 mm to 100 mm, preferably 10 mm to 40 mm, particularly preferably 20 mm to 30 mm.

[0065] FIG. 3 shows a section through the radius component 4 along the frontal plane E1. In the embodiment described, the first joint surface 16 is implemented alternately concave and convex in the frontal plane E1. Purely concave or purely convex courses of the first joint surface 16 are also preferred. The tunnel 36 preferably has a constant cross section 72 which corresponds to the cross section of the first access 50. The cross section 72 is preferably implemented mirror-symmetrically to the central axis ZA. The maximum width B1, measured perpendicular to the central axis ZA, is disposed in the transition region 40 in the embodiment example. It should be understood that embodiments that have maximum widths B1 along the central axis ZA in the direction of the first joint surface 16 from the transition region 40 are also preferred.

[0066] FIG. 4 shows a section through the radius component 4 along a sagittal plane E2. In the embodiment shown, an upper transition region 74 between the first joint surface 16 and a face surface 76 of the head 12 is implemented as an edge. Furthermore, completely or partially rounded transition regions 74 are also preferred. According to the present embodiment example, the first joint surface 16 is implemented in the sagittal plane E2 as a concave recess 78 which runs along the central axis ZA in the direction of the proximal shaft end 38. Likewise, first joint surfaces 16 which are implemented as convex elevations are also preferred.

[0067] In the embodiment described, the tunnel 36 runs in the region of the head 12 from the dorsal face 64 of the radius component 4 to the palmar face 66 and is curved in the direction of the proximal shaft end 38. A proximal point 84 of the tunnel 36, measured in the direction of the central axis ZA, is preferably disposed on the central axis ZA. The proximal point 84 is that point of the tunnel 36 which, measured in the direction of the central axis ZA, has the smallest distance from the proximal shaft end 38. Distal transition regions 86, 88 of the tunnel 36 to the dorsal face 64 and palmar face 66 are preferably rounded. Fully rounded first and second accesses 50, 51 are also preferred. The material of the head 12 between the joint surface 16 and the tunnel 36 has a minimum thickness D5 in a range of 20% to 200%, preferably 30% to 150%, particularly preferably 40% to 110%, of the length of the narrow face 52,54 of the tunnel 8. Furthermore, the minimum thickness D5 preferably has a range from 10% to 60%, preferably 50% to 60% of the thickness D4. Furthermore, the thickness D5 is preferably greater near the transition regions 86, 88 than in the region of the central axis ZA.

[0068] In the embodiment described, the radius component 4 is implemented mirror-symmetrically to the frontal plane E1. It should be understood that non-symmetrical or component-wise symmetrical embodiments of the radius component 4 are also preferred. For example, only the tunnel 36 and/or the transition region 40 could be implemented symmetrically to the frontal plane E1. A tangent TG2 is implemented tangentially to delimitation points 80, 82 of the first joint surface 16 in the sagittal plane E2. According to the present embodiment example, an angle δ between the tangent TG2 and a plane perpendicular to the central axis ZA is 90°. It should be understood that angles δ are preferred which have a range from 30° to 150°, particularly preferably 80° to 120°.

[0069] According to the present embodiment example, the first joint surface 16 is implemented concave in the sagittal plane E2. Concave first joint surfaces 16 in the frontal plane E1 are also preferred. The face surface 76 of the head 12 is formed on the dorsal face 64 of the radius component 4 and the palmar face 66 substantially parallel to the central axis ZA, so that the width of the head 12 in the sagittal plane E2 is constant and corresponds to the width B3 of the first joint surface 16. Embodiments are also preferred in which the head 12 widens and/or tapers in the direction of the first joint surface 16 so that a maximum width B5 differs from the width of the joint surface B3. The width B3 has a range from 10% to 150%, preferably 50% to 100%, particularly preferably 70% to 90%, of the width B1 in the frontal plane E1. In the embodiment shown, an angle δ, measured between the central axis ZA and a tangent TG1 at a first end point 81 on the dorsal face 64 and a second end point 83 on the palmar face 66, is 90°; other angles in a range of 0° to 180° are also preferred.

[0070] Referring now to FIGS. 5 and 6, the carpal component 6 will be described in more detail. FIG. 6 shows a section through the carpal component 6 in the sagittal plane E2. The carpal component 6 comprises a distal segment 90 and a proximal segment 92. The carpal cavity 18 is open to a distal carpal face 20. A second joint surface 24 is implemented on a proximal carpal face 22 opposite the distal carpal face 20. According to the present embodiment example, a maximum width B2 of the carpal component 6 parallel to the frontal plane E1 is greater than a maximum width B6 of the carpal component 6 perpendicular thereto in the sagittal plane E2 (see FIG. 6). The carpal component 6 is implemented elongated parallel to the frontal plane E1. In the embodiment shown, the first lateral opening 28 disposed on the radius face 26 is implemented as a first slot 94. In an analogous manner, the second lateral opening 32 disposed on the ulnar face 30 is implemented as a second slot 96. The slots 94, 96 are open in the direction of the distal carpal face 20.

[0071] In the embodiment shown, the first slot 94 and the second slot 96 are implemented mirror-symmetrically to the sagittal plane E2. A depth T1 of the slots 94, 96, measured starting from the distal carpal face 20 in the direction of the proximal carpal face 22, extends into the proximal segment 92. Likewise, the slots 94, 96 can only be disposed in the distal segment 90 of the carpal component 6. The depth T1, measured between the distal carpal face 20 and the proximal carpal face 22, has a range from 20% to 80%, preferably 30% to 70%, particularly preferably 40% to 60%, of the length L2 of the carpal component 6. It should be understood that asymmetrically implemented slots 94,96 are also preferred. The first slot 94 can preferably have a third depth T3, which is different from the depth T1. It is further preferred that the carpal cavity 18 comprises a bulge 112 in the direction of the proximal carpal face 22. A depth T2 of the bulge, measured from the distal carpal face 20 in the direction of the proximal carpal face 22, is preferably greater than the depth T1 and/or the depth T3. In the embodiment shown, the transition regions 102 between an inner surface 98 of the carpal cavity and an outer surface 100 of the carpal component 6 are implemented with edges 103. Rounded transition regions 102 are also preferred.

[0072] In the embodiment shown, the transition 104 between the distal segment 90 and the proximal segment 92 is implemented as a shoulder 105. The distal segment 90 of the carpal component 6 is parallel to the frontal plane E1, tapering in the direction of the distal carpal face 20, so that said distal segment has a trapezoidal shape in the present embodiment example. Outer corners 113,114,116,118 are implemented pointed here. Rounded corners 113,114,116,118 are also preferred. A width B7 parallel to the frontal plane at the distal end 106 of the carpal component 6 is less than a maximum width B2. The proximal end 108 of the carpal component 6 is disposed on the proximal face 22. The proximal end 108 is preferably implemented as a thickening 110. The second joint surface 24 is disposed on the thickening 110. The thickening 110 is implemented here as a convex elevation. The thickening can also be implemented as a concave recess, so that the second joint surface 24 is also concave in the frontal plane E1. According to the present embodiment example, the thickening 110 extends over the entire proximal segment 92 of the carpal component 6. In addition, embodiments that have a thickening 110 that extends only partially over the proximal segment 92 are also preferred. A thickness D7 of the carpal component 6, measured between the inner surface 98 and the outer surface 100 in the region of the distal end 106, is here less than a corresponding thickness D8 in the region of the proximal end 108. A ratio of the wall thicknesses D8:D7 preferably has a range from 8:1 to 1:1, more preferably 6:1 to 1:1, particularly preferably 6:1 to 3:1.

[0073] The carpal cavity 18 has a substantially U-shaped cross section. According to the present embodiment example, a clear width W1 of the carpal cavity 18 at the distal end 106 is smaller than a maximum clear width W2 in the interior of the carpal cavity 18. The carpal cavity 18 preferably tapers in the direction of the distal carpal face 20. Carpal cavities 18 which widen in the direction of the distal carpal face 20 are also preferred. In the embodiment described, the transition regions 102 at the distal end of the carpal component 6 are implemented as planar surfaces 117, 119. A rounded transition between inner surface 98 and outer surface 100 is also preferred.

[0074] In the exemplary embodiment, the second joint surface 24 is convex in the sagittal plane E2. However, concave or concave-convex second joint surfaces are also preferred. Here, a first transition 120 between shoulder 105 and the proximal segment 92 is rounded, while a second transition 122 between the shoulder 105 and the distal segment 90 is angled, particularly right-angled. Two rounded or angular transitions 120, 122 and a continuous transition without a shoulder 105 between the distal segment 90 and the proximal segment 92 are also preferred. If the first transition 120 and/or the second transition 122 are rounded, impairment of the surrounding soft tissue of a patient can be reduced or avoided after the implantation. The proximal end 108 of the carpal component 6 preferably comprises a continuous and/or rounded outer surface for this purpose.

[0075] Referring now to FIG. 7, the luxation protection 8 will be further described. The band 34 of the luxation protection 8 comprises a first end 124 which is attached to the dorsal carpal face 126. Furthermore, a second end 128 of the band 34 is attached to a palmar carpal face 130. The dorsal carpal face 126 is preferably substantially perpendicular to the distal carpal face 20 and to the radius face 26. In the present embodiment example, the first end 124 and the second end 128 are attached to the shoulder 105. It is also preferred that the first end 124 and/or the second end 128 are attached to the distal end 106 of the carpal part 6, to the distal segment 90, to the proximal segment 92, to the proximal end 108 and/or to the inner surface 98 of the carpal cavity 18. The attaching can preferably take place in a positive, frictional and/or material manner. The band 34 extends through the tunnel 36 between the first end 124 and the second end 128. The carpal component 6 and the radius component 4 of the wrist endoprosthesis 2 are thereby connected. The band 34 is only connected to the radius component 4 in a positive manner here by a loop formed between the first end 124 and the second end 128. The band 34 can thereby preferably slide relative to the tunnel 36. Rotational and tilting movements of the carpal component 6 relative to the radius component 4 are possible. The frictional forces between band 34 and tunnel 36 and between the first joint surface 16 and the second joint surface 24 must be overcome for this purpose. Synovial fluid can act as a lubricant. Furthermore, embodiments that have a fixed connection of the band 34 to the radius component 4 are preferred.

[0076] The band is preferably formed from a fibre material and/or a plastic. The band 34 is preferably pretensioned such that said band applies a pretensioning force F which brings about a contact between the first joint surface 16 and the second joint surface 24. A lifting of the carpal component 6 from the radius component 4 can be avoided by the pretensioning force. The pretensioning force has a range from 0 N to 1000 N, preferably 5 N to 200 N, particularly preferably 100 N to 150 N.

[0077] Embodiments that comprise a rigid band 34 are also preferred. A rigid band 34 has a high resistance to longitudinal expansion and thus counteracts the longitudinal expansion thereof. The pretensioning force can be reduced or omitted, as a result of which frictional forces occurring between the first joint surface 16 and the second joint surface 24 are reduced. A slight gap between the first joint surface 16 and the second joint surface 24 is possible.

[0078] Furthermore, embodiments of the invention that have a second band running through a second tunnel are preferred (not shown). The second tunnel preferably runs perpendicular to the first tunnel 36, wherein a first end of the second band is attached to a radius face 26 of the carpal component 6 and a second end of the second band is attached to an ulnar face 28 of the carpal component 6. The carpal component 6 can be prevented from slipping off the first joint surface 16 by designing the luxation protection 8 that has two bands. Furthermore, embodiments are preferred in which the head 12 does not comprise a tunnel (not shown). In such embodiments, a first end 124 of the band 34 can be connected to the carpal part 6 and a second end 128 of the band 34 can be connected to the radius part 36.

[0079] The further embodiments can have the same or similar features as the embodiment according to the example described, which is why reference is made in full to the above description.

[0080] The flow chart shown in FIG. 8 illustrates a method for producing a wrist endoprosthesis 2. In a first step S1, a non-individualized 3D model of a wrist endoprosthesis 2 is provided or produced. The non-individualized 3D model is preferably produced using computer-aided image processing programs and/or 3D CAD programs. Providing the non-individualized 3-D model can preferably have the following steps: selecting a suitable non-individualized 3D model from a database and loading the selected non-individualized 3D model into an image processing program and/or 3D CAD program.

[0081] In a second step S2, data material, particularly x-ray images, ultrasound images, magnetic resonance tomography data, and/or computed tomography data, of a wrist of a patient to be treated is acquired. The data material is preferably acquired at least in a first view parallel to the frontal plane E1 and in a second view parallel to the sagittal plane E2. Further views at an angle to the first and second views are preferably acquired. Furthermore, a 3D model of the wrist to be treated is preferably created from the magnetic resonance tomography data and/or computed tomography data. If information on the wrist to be treated is no longer available due to injuries or previous illnesses, step S2a is preferably carried out: acquiring data material, particularly x-ray images, ultrasound images, magnetic resonance tomography data and/or computer tomography data, of the second wrist of a patient. Data material which corresponds to the data material from step S2 is preferably acquired, which is why reference is made in full to the above description. If information from both wrists of the treating patient is no longer available, step S2b is preferably carried out: providing data from a statistical comparison group. The data material of the statistical comparison group can contain information equivalent to that of the data material acquired in steps S2 or S2a.

[0082] The comparison group can have people of the same sex, same age, same body size, same arm length, same hand size and/or the same anthropometric data. It should be understood that steps S2, S2a and S2b can also be executed in combination. For example, a first joint surface of the radius can be determined from x-ray images of the wrist to be treated and an angle of a second joint surface can be determined from data material from a statistical comparison group. Alternative or supplementary data material can preferably be provided which is based on individual empirical values, simulation data, literature data, statistical models, anthropometric comparison data, anthropometric ratio calculations, geometric ratios, previous examinations of the patient and/or mathematically determined optima.

[0083] Following steps S2, S2a and/or S2b, step S3 is carried out in the method: determining one or more parameters from the data material for approximating an approximated joint structure of the patient from the data material. The parameters can be determined from the data material manually, partially or fully automatically, preferably based on image material or 3D models. The parameter determined from the data material can be at least one of the parameters from the following group of parameters: ulnar variance UV, thickness of the cortex, plane shape of the inner cavity of the radius, radius of the proximal carpal row in a sagittal plane and/or frontal plane, joint surface angle in a sagittal plane and/or frontal plane, course of the mechanical forearm axis, curve course of the proximal and/or distal carpal row in a sagittal plane and/or frontal plane. The ulnar variance UV describes a length difference between the segment of the distal end 136 of the radius 134 pointing towards the ulna 132 and the segment of the distal end 138 of the ulna 132 of the arm to be treated pointing towards the radius 134. It is also possible to derive the course of the proximal and/or distal carpal row as an exact curve or to approximate said curve course as a radius or a curve course composed of a plurality of radii. The plane shape of the joint surfaces of the radial bone 134, the ulna 132 and/or the proximal carpal row can be derived exactly or approximately from the data material. The exact plane shape is preferably approximated by circular and/or elliptical fittings. Furthermore, the joint surfaces can be approximated by multi-axis convex, multi-axis concave or multi-axis convex-concave planes. Furthermore, an angle δ is preferably determined between a straight-line tangent to the distal end of the radius in the frontal plane and a straight line of the radius that is perpendicular to the longitudinal axis and lies in the frontal plane. In an analogous manner, an angle c is preferably also determined between a straight-line tangent to the distal end of the radius in the sagittal plane and a straight line that is perpendicular to the longitudinal axis of the radius and lies in the sagittal plane. The parameters of the data material such as plane shapes and surface shapes are preferably approximated. The approximation preferably includes at least the step: rounding the determined sizes to sizes that can be processed in the method. It is also preferred to execute step S1 following one of steps S2, S2a, S2b or S3.

[0084] In a fourth step S4, the non-individualized 3D model is individualized based on the derived parameters for obtaining an individualized 3D model.

[0085] Geometric properties of the non-individualized 3D model are preferably adapted to the approximated parameters. The angle α of the first joint surface is preferably adjusted or approximated to the determined or approximated angle R. Furthermore, the angle δ is preferably adjusted or approximated to the determined or approximated angle c. Furthermore, the length L1 and the tapering of the shaft 10 are preferably adapted taking into account at least one of the determined or approximated sizes, thickness of the cortex, diameter of the radius of a patient, diameter ratio of the radius. Furthermore, the first joint surface is preferably individualized such that said joint surface corresponds to the exact or approximated distal surface of the radius of the patient to be treated. In a further preferred embodiment of the method, the second joint surface is individualized such that said joint surface corresponds to the approximated and/or exact curve shape of the proximal carpal row of the patient in the sagittal plane and/or frontal plane.

[0086] Subsequent to step S4, step S5 is executed: producing the wrist endoprosthesis 2 by means of an additive manufacturing process based on the individualized 3D model. The additive manufacturing process is preferably one of the following processes: fused deposition modelling, selective laser sintering, selective laser melting, electron beam melting, laser deposition welding, multi-jet modelling, stereolithography, laminated object modelling. Step S5 preferably comprises at least one of the steps: loading the individualized 3D model, generating the layer information of the individual layers based on the individualized 3D model, generating the layer information of the individual layers to be manufactured taking into account support structures, preparing the manufacturing machine and/or the material, constructing the wrist endoprosthesis 2 layer-by-layer, removing the support structures, reworking the upper and/or active surfaces, checking for damage and/or compliance with the individualized 3D model, completely or partially coating the wrist endoprosthesis with a coating material, preferably titanium. A part of the shaft 10 which is disposed in the epiphysis 142 and/or the metaphysis 144 of the radius 134 as part of the implantation of the wrist endoprosthesis 2 is particularly preferably coated. The wrist endoprosthesis 2 is preferably made from a metal, fibre composite material and/or plastic, particularly preferably polyetheretherketone, cobalt-chromium alloys and/or titanium.

[0087] Referring now to FIG. 11 and FIG. 12, steps S3 and S4 of a preferred refinement of the method for producing a wrist endoprosthesis 2 are described. The anterior-posterior view of the bone structure of a human wrist shown in FIG. 11 and the view of the bone structure of a human wrist shown in FIG. 12 in a sagittal plane were previously acquired in step S2.

[0088] First, parameters P1 to P16 are determined, which parameters preferably form a basis for an individualization of the shaft 10 of the radius component 4 carried out in step S4. The parameters P1 to P4 represent frontal radius diameters of the radius 134, which are parallel to one another and are determined perpendicular to a central axis of the radius 134 in the frontal plane E1. The frontal radius diameter P1 is preferably determined at the height of the distal end 138 of the ulna 132. A second frontal radius diameter P2 is preferably determined at a first transition 140 between an epiphysis 142 and a metaphysis 144 of the radius 134 and/or a third frontal radius diameter P3 is determined at a second transition 146 between the metaphysis 144 and a diaphysis 148 of the radius 134. A position of the fourth frontal radius diameter P4 is determined individually for each patient, based on the bone structure of the patient. Further frontal radius diameters can preferably also be determined from the data material. Preferably, the thickness of the cortex of the radius 134, measured in the frontal plane E1, is determined as parameters P5 to P8 at the height of the distal end 138 of the ulna 132, at the first transition 140, at the second transition 146 and/or at the height of the fourth frontal radius diameter P4.

[0089] Sagittal radius diameters P9 to P12 of radius 134 and sagittal thicknesses of cortex P13 to P16 are preferably determined in an analogous manner from the bone structure in the sagittal plane (FIG. 12). The sagittal radius diameters P9 to P12 are preferably determined perpendicular to the frontal radius diameters P1 to P4. It is also preferred that the sagittal thicknesses of the cortex P13 to P16 are determined perpendicular to the frontal thicknesses of the cortex P5 to P8. In addition, the ulnar variance UV is determined as parameter P17 (not shown in FIG. 11).

[0090] A width P18 of the proximal carpal row 150 in the frontal plane E1 and/or a width P19 of the proximal carpal row 150 in the sagittal plane E2 are preferably determined as parameters. The width P18 is preferably measured in a lateral-medial direction R1 from a most lateral end 152 of the proximal carpal row 150 to a most medial end 154 of the proximal carpal row 150. The width P19 is preferably measured in an anterior-posterior direction R2 from a most anterior end 156 of the proximal carpal row 150 to a most posterior end 158 of the proximal carpal row 150. A height P20 of the proximal carpal row, measured between a most distal end 160 of the proximal carpal row and a most proximal end 162 of the proximal carpal row, is preferably a further parameter. A height of the carpal P21 is preferably determined between the most proximal end 162 and a most distal end 164 of a distal carpal row 166.

[0091] The angles β and ε are preferably determined and, in the present embodiment example, referred to as parameters P22 and parameters P23.

[0092] A frontal joint line P24 preferably bisects a distance between the proximal carpal row 150 and the joint surfaces 168, 170 of the radius 134 and the ulna 132. A sagittal joint line P25 preferably bisects a distance between the proximal carpal row 150 and the joint surface 168 of the radius 134. The frontal joint line P24 and/or the sagittal joint line P25 is preferably processed by an elliptical fitting and/or a circular fitting. A real course of the joint line is approximated by one or more circles and/or one or more ellipses.

[0093] In the present embodiment example, the position of a longitudinal axis of the radius 134 in extension through a third metacarpal bone 172 is determined as the final parameter P26.

[0094] The non-individualized 3D model of a wrist endoprosthesis 2 provided in step S1 is then individualized in step S4 based on the parameters P1 to P24. A diameter of the shaft 10 of the radius component 4 in the region of the connecting segment 40 is individualized here based on the parameters P1, P5, P9 and P12. A diameter of the shaft 10 at the connecting segment 40 in the frontal plane is preferably individualized such that said diameter corresponds to the difference between the frontal radius diameter P1 and the thickness of the cortex P5. In order to ensure that the shaft 10 is securely jammed in the radius 134, a jamming allowance, which is determined individually for each patient, is preferably added.

[0095] The jamming allowance preferably has a range from 0% to 25%, particularly preferably 5% to 10%, of the frontal radius diameter P1. The jamming allowance is calculated based on the cavity. In the case of a single radius, an increase in the radius, in the case of an elliptical shape, correspondingly along the axes of the ellipse.

[0096] P13 is subtracted from P9 and a jamming allowance is added in an analogous way. The allowance factor is preferably added symmetrically. Here, a cross section of the shaft 10 in the region of the connecting segment 40 is circular if a difference between P1 and P5 and P13 and P9 coincide, and elliptical if the differences between P1 and P5 and P13 and P9 differ. A diameter of the shaft 10 of the radius component 4 at the first transition 140, at the second transition 146 and in the region of the proximal shaft end 38 are preferably determined analogously from the parameters P2 to P4, P6 to P8, P10 to P12 and P14 to P16. The lateral surface 70 of the shaft 10 between the connecting segment 40 and the first transition 140 to the metaphysis 144 preferably comprises a porous surface structure. Growing in of the shaft 10 into the radius 134 can be improved by a porous surface structure. The lateral surface 70 of the shaft 10 is preferably smooth and/or polished between the first transition 140 and the proximal shaft end 38. The insertion of the shaft 10 into the radius 134 can thereby be facilitated in the course of treating a patient. The first joint surface 16 of the shaft 10 of the wrist endoprosthesis 2 is preferably aligned based on the parameters P22 and P23. The thickness D1 of the head 12 on the radius face 44 and the thickness D2 of the head 12 on the ulnar face 46 are particularly preferably adapted such that an ulnar variance UV disappears after an implantation of the radius component 4. It is also preferred that the ulnar variance UV of a natural wrist and the ulnar variance UV of a wrist fitted with a wrist endoprosthesis coincide. Furthermore, a shape of the first joint surface 16 is preferably adapted based on the frontal joint line P24 and/or sagittal joint line P25.

[0097] According to the present embodiment example, the second maximum width B2 of the carpal component 6 is individualized based on the width P18 of the proximal carpal row 150. The clear width W1 at the distal end 106 of the carpal cavity 18 and the maximum clear width W2 are individualized based on the width P19 of the proximal carpal row 150 in the sagittal plane E2.

[0098] The length L2 of the carpal component 6 is preferably individualized in step S4 based on the height of the wrist P21. A height P20 of the proximal carpal row 150 can also serve as a supplementary and/or stand-alone basis for the individualization of the length L2. Furthermore, the height P20 of the proximal carpal row 150 can preferably be used as a basis for individualizing the depth T1 of the carpal component 6, the depth T2 of the bulge 112 and/or the thickness D8 at the proximal end 108 of the carpal component 6. An allowance for individual adaptation in a range of 0% to 25%, particularly preferably 5% to 10%, of the height P20 and/or the height of the carpal P21 (carpal height) is preferably added.

[0099] In the present embodiment example, the second joint surface 24 is adapted based on the frontal joint line P24 and the sagittal joint line P25. The radius component 4 and the carpal component 6 are then aligned with one another, wherein the radius component 4 and/or the carpal component 6 are preferably disposed perpendicular to the determined position P26 of the longitudinal axis through the radius 134 and the third metacarpal bone 172.

[0100] The wrist endoprosthesis 2 is then produced in the fifth step S5.

[0101] FIGS. 13 a to c illustrate an individualized 3D model 174 of a carpal component 6 or an adapted anatomy-facing face 176 of the individualized 3D model 174 of a carpal component 6 of a wrist endoprosthesis 2. An outer face 178 of the 3D model 174 is implemented oval in a view from distal to proximal (FIG. 13a). Irritation of the tissue surrounding the later wrist endoprosthesis 2 can be prevented in this way. The anatomy-facing face 176 of the individualized 3D model 174, which here is the inner surface 98 of the carpal component 6, has been adapted to the patient-specific anatomy. The anatomy-facing face 176 comprises a plurality of elevations 178a, 178b, 178c which correspond to recesses of ligamentous connections of the wrist to be treated (not shown). A first elevation 178a corresponds here with a ligamentous connection between the triangular bone and the lunar bone. A second elevation 178b corresponds to a ligamentous connection between the lunar bone and the navicular bone. A third elevation corresponds to a ligamentous connection between the navicular bone and the small polygonal bone. FIG. 13b illustrates a view of the individualized 3D model 174 in the radial-ulnar direction. The outer face 178 is substantially U-shaped in the present view. Section lines of the anatomy-facing face 176, also illustrated by lines 180a, 180b, are substantially U-shaped. A height of the elevation 178a is greater than a height of the elevation 178b, so that a depth of the U-shape formed by line 180a is less than a depth of the U-shape formed by line 180b. It should be understood that preferably the entire anatomy-facing face 174 represents a negative shape 182 of the anatomy, particularly of the bony structure, of the wrist to be treated. In addition to elevations 178a, 178b, 178c, the remaining inner surface 98 is also adapted to the anatomy of the wrist to be treated (see FIGS. 13a, 13b). The elevations 178a, 178b, 178c can engage in corresponding recesses between the carpal bones and prevent the implanted wrist endoprosthesis 2 from slipping.