ENDOPROSTHESIS

Abstract

Disclosed is an endoprosthesis for implantation in bone surgery, in particular hip surgery, without the use of surgical cement. The hip joint endoprosthesis for implantation in bone surgery of ball-and-socket joints, in particular hip joint, has a moving connection provided by the contact surface of two modules of the endoprosthesis femoral head and acetabulum, whereas their surfaces which are in contact with the bone next to the joint have a shape similar to a sphere, on which pins are placed, with an axis principally parallel to the lengthwise axis of the endoprosthesis, and at least two cutting blades with an arc-shaped cross-section outline, creating a groove for removal of the products of cutting.

Claims

1. A hip joint endoprosthesis for implantation in bone surgery of ball-and-socket joints, in particular hip joint, comprising a moving connection provided by a contact surface of two modules of the endoprosthesis femoral head and acetabulum, whereas their surfaces which are in contact with the bone next to the joint have a shape similar to a sphere, on which pins are placed, with an axis principally parallel to the lengthwise axis of the endoprosthesis, and at least two cutting blades with an arc-shaped cross-section outline, creating a groove for removal of the products of cutting.

2. An endoprosthesis in accordance with claim 1, wherein the sphere is a convex shell, on which pins are located, forming the endoprosthesis acetabulum.

3. An endoprosthesis in accordance with claim 1, wherein the sphere is a concave shell, on which pins are located, forming the endoprosthesis femoral head.

4. An endoprosthesis in accordance with claim 1, wherein it has on its external surface, in the zone of the lengthwise axis, advantageously rounded, porous supporting surface.

5. An endoprosthesis in accordance with claim 2, wherein the pins are placed in the area outside of the supporting surface, forming the a limiting surface.

6. An endoprosthesis in accordance with claim 3, wherein the pins are placed on a spherical surface forming a limiting surface.

7. An endoprosthesis in accordance with claim 1, wherein the cutting blades of the pins have an angle of application β within a range of 5-15°, advantageously 10°, an angle of attack a 35-45°, advantageously 40°, and the a wall thickness H of the pins cutting blade wall amounting to 0.25-1 mm, advantageously 0.5 mm, and the HI height of the cutting blade is 2-3 times higher than the H2 height of the opposite wall of the groove.

8. An endoprosthesis in accordance with claim 1, wherein the supporting surface has a D2 diameter with a value of ½-⅓ of the D1 diameter of the femoral head.

9. An endoprosthesis in accordance with claim 1, wherein the femoral head endoprosthesis has a cylindrical elongation with an 1 angle in relation to the centre point within a range of 30 to 50 degrees,

10. An endoprosthesis in accordance with claim 1, wherein the end of the grooves is situated in a zone of technological gripping devices.

11. An endoprosthesis in accordance with claim 1, wherein a distance z between the bases of adjacent pins is at least 100 micrometers.

12. An endoprosthesis in accordance with claim 1, wherein the pins have the shape of a cone.

13. An endoprosthesis in accordance with claim 1, wherein the pins have the shape of a rounded cone.

14. An endoprosthesis in accordance with claim 1, wherein the pins have the shape of a truncated cone.

15. An endoprosthesis in accordance with claim 1, wherein the pins 2 have the shape of a regular polyhedron.

16. An endoprosthesis in accordance with claim 1, wherein the pins have smooth side surfaces.

17. An endoprosthesis in accordance with claim 1, wherein the pins have shaped side surfaces.

18. An endoprosthesis in accordance with claim 2, wherein the height of the pins on the surface of the endoprosthesis acetabulum shell decreases from the edge to the supporting surface.

19. An endoprosthesis in accordance with claim 1, wherein the height of the pins on the surface of the convex endoprosthesis femoral head shell decreases from the central axis of the endoprosthesis to the external direction.

20. An endoprosthesis in accordance with claim 1, wherein the height of the highest pin is approximately twice the height of the lowest pin.

21. An endoprosthesis in accordance with claim 1, wherein the top points of the pins create a surface with an outline similar to the surface of the sphere on which they are placed.

22. An endoprosthesis in accordance with claim 1, wherein the pins are placed on the external surface of the acetabulum.

23. An endoprosthesis in accordance with claim 1, wherein the pins are placed on the internal surface of the femoral head.

24. An endoprosthesis in accordance with claim 1, wherein an insert is introduced or not on the internal spherical surface of the endoprosthesis acetabulum.

Description

[0034] The subject of the invention, in the example implementation was presented on drawings, where FIG. 1 presents a view of the acetabulum on the side of the supporting surface, FIG. 2 presents a detail of FIG. 1, FIG. 3 presents a cross-section of a cutting blade, and FIG. 4 a cross-section of the acetabulum, FIG. 5 demonstrates a view of the acetabulum, FIG. 6 presents a detail of the acetabulum from FIG. 5, FIG. 7 presents a view of the acetabulum on the side of the supporting surface, FIG. 8 demonstrates a detail of the acetabulum from FIG. 7, FIG. 9 presents a cross-section of the cutting blade, FIG. 10 presents a view of the acetabulum, FIG. 11 presents a detail of the acetabulum from FIG. 10, FIG. 12 presents a view of the femoral head, FIG. 13 presents a detail of the view from FIG. 12, FIG. 14 demonstrates a cross-section of the femoral head, FIG. 15 presents a view of the femoral head on the side of the limiting surface, FIG. 16 presents a detail of the view from FIG. 15, FIG. 17 presents a view of the femoral head, and FIG. 18 a detail of the view of the femoral head from FIG. 17, FIG. 19 presents a view of the femoral head on the side of the limiting surface, FIG. 20 a detail of the femoral head from FIG. 19, FIG. 21 presents a cross-section of the pins, and FIG. 22 demonstrates a fragment of the cross-section of the femoral head, FIG. 23 a cross-section of the pin, FIG. 23a presents a pin in the form of a cone, FIG. 23b a pin in the form of a rounded cone, FIG. 23c a pin in the form of a prism, FIG. 23d a pin in the form of a cuboid, FIG. 24 presents a fragment of the cross-section of the acetabulum, FIG. 25 presents an isometric view of the acetabulum on the side of contact of friction couple, FIG. 26 presents a cross-section of the endoprosthesis acetabulum and femoral head system embedded on bone surfaces, FIG. 27 presents a cross-section of the friction couple, and FIG. 28 presents a cross-section of the femoral head endoprosthesis with a demonstrated angle of elongation of the cylindrical surface.

[0035] Hip joint endoprosthesis for implantation in bone surgery of ball-and-socket joints, in particular hip joint, consists of a moving connection provided by the contact surface 10 of two modules of the endoprosthesis femoral head 9 and acetabulum 1. The surfaces of the endoprosthesis femoral head 9 and acetabulum 1 which are in contact with the bone next to the joint have a shape similar to a sphere, on which pins 2 are placed. The pins 2 have an axis in principle parallel to the longitudinal axis of the endoprosthesis and at least two cutting blades 3 with an arc-shaped cross-section outline are formed, creating a groove 5 for removal of the products of cutting. In the endoprosthesis the sphere is a convex shell, on which pins 2 are located, forming the endoprosthesis acetabulum 1. The sphere is a concave shell, on which pins 2 are located, forming the endoprosthesis femoral head 9. The endoprosthesis has on its external surface, in the zone of the lengthwise axis, advantageously rounded, porous supporting surface 6. The pins 2 are placed in the area outside of the supporting surface 6, forming the limiting surface 11 and are placed on a spherical surface forming the limiting surface 11. In the endoprosthesis the cutting blades 3 have an angle of application β within a range of 5-15°, advantageously 10°, angle of attack α 35-45°, advantageously 40°, and the wall thickness H of the cutting blade 3 wall amounting to 0.25-1 mm, advantageously 0.5 mm, and the H1 height of the cutting blade 3 is 2-3 times higher than the H2 height of the opposite wall 4 of the groove 5. The supporting surface 6 has a D2 diameter with a value of ½-⅓ of the D1 diameter of the femoral head 1. The femoral head endoprosthesis has a cylindrical elongation with an λ angle in relation to the centre point within a range of 30 to 50 degrees. In the endoprosthesis the end of the grooves 5 is situated in the zone of technological gripping devices 8. The distance between the bases of adjacent pins 2 is at least 100 micrometers. The pins 2 have a shape of a cone or a rounded cone or a truncated cone or a regular polyhedron. Moreover the pins 2 have smooth side surfaces or shaped side surfaces. The height of pins 2 decreases from the edge to the supporting surface and from the central axis of the endoprosthesis to the external direction. The height of the highest pin 2 is approximately twice the height of the lowest pin 2. The top points of the pins 2 create a surface with an outline similar to the surface of the sphere on which they are placed. The pins 2 are placed on the external surface of the acetabulum 1 and on the internal surface of femoral head 9. Additionally an insert 14 is introduced or not on the internal spherical surface of the endoprosthesis acetabulum 1.

[0036] The endoprosthesis consists of acetabulum 1 and femoral head 9, which on their limit surfaces in the form of spherical shells have polygonal needle protrusions in the form of pins 2 with parallel axes and varying length, the total area of which is a multiple of the joint area, whereas the minimum distance “z” between the bases of pins 2 is 100 micrometers, used in order to enable growth of trabeculae. The bases of pins 2 are not tangential. The axes of pins 2 are perpendicular to the plane of the supporting surface of the femoral head and of the supporting surface of the acetabulum 1, respectively. Additionally in order to reduce the abrasive wear of the friction couple of the acetabulum 1 and femoral head 9 of the hip joint endoprosthesis an insert 14 is introduced or not on the internal spherical surface of the endoprosthesis acetabulum 1 made of non-metallic material.

[0037] A precondition for the operation of the system is the fitting of the shape and size of the endoprosthesis femoral head 9 to the size and shape of the endoprosthesis acetabulum 1 in order to ensure the correct operation of the friction couple.

[0038] The endoprosthesis femoral head 9 is placed in the grips of an external device providing rotational movement, not shown on the drawing. This device moves the endoprosthesis around its angle of symmetry with a specific speed adapted to the machined material. The endoprosthesis, in the form of femoral head 9 is rotated, using the cutting blades 3 to remove bone tissue 7, which falls into the groove 5 between the wall of the cutting blade 3, and the wall 4 of the groove 5 or between the wall of the cutting blade 3 and the pins 2. The bone tissue 7 is moved by the pressure exerted by the newly cut bone tissue 7 between the wall of the cutting blade 3 and the wall 4 of the groove 5 or between the wall of the cutting blade 3 and the pins 2 out of the endoprosthesis, through the direct surface of the contact of the endoprosthesis with the bone tissue 7 surface. This process lasts until an optimum position of the endoprosthesis is obtained. The endoprosthesis causes a slight filling of the space between the pins 2 with small fragments of bone, which will feed the process of bone reconstruction and stabilisation of the endoprosthesis. After removing the diseased tissue of the joint connection and using the cutting blades 3 to obtain a shape similar to the outline created by the tips of the pins 2, the endoprosthesis is disconnected from the device providing rotational movement, not shown of the drawing, and then is placed on the previously prepared surface and gradually inserted into the spongy bone space, in parallel to the axis of symmetry of the femoral head 13 of the joint. The supporting surface 6 does not contact the periosteum, the cortical substance and the spongy substance, into which the pins 2 at a distance longer than the plane of the supporting surface 6 are simultaneously inserted. The pins do not penetrate the spongy bone fully, to enable releasing of excessive intraosseous fluid pressure. The space between the pins 2 which is not filled with bone tissue 7 in this process will be filled with osteoblasts in the process of tissue regeneration, which will grow during the convalescence period.

[0039] The implantation method for acetabulum endoprosthesis is similar to the implantation of the femoral head, whereas the acetabulum endoprosthesis is implanted in such a manner that the supporting surface 6 of the truncated limiting surface adheres to the bone in a plane perpendicular to the axis of the central acetabulum 1 of the bone and be placed in a manner symmetric to this axis, and polygonal pins 2 in the area of the spherical belt on the limiting surface 11 of the endoprosthesis acetabulum 1 are partially sunk into the spongy structure of the bone. The remaining space between the polygonal needle protrusions 2 not sunk into the spongy bone, up to the limiting surface 11 are filled with osteoblasts which grow during the convalescence period as a result of lack of movement between the endoprosthesis acetabulum and the bone 12. The supporting surface 6 with a slight rounding protects the implanting process against possible trauma to blood vessels present in the direct vicinity of the cut tissue.

[0040] Additionally in order to reduce the abrasive wear of the friction couple of the acetabulum 1 and femoral head 9 of the hip joint endoprosthesis an insert 14 is introduced or not on the internal spherical surface of the endoprosthesis acetabulum 1 made of non-metallic material.

[0041] A precondition for the operation of the system is the fitting of the shape and size of the endoprosthesis femoral head 9 to the size and shape of the endoprosthesis acetabulum 1 in order to ensure the correct operation of the friction couple.

[0042] The pins 2 are partially sunk in the bone tissue 7, advantageously to half their height, in order to allow osteoblasts to grow on the surface which is not sunk in the bone tissue 7.

DESIGNATION

[0043] 1—acetabulum [0044] 2—pin [0045] 3—cutting blade [0046] 4—wall [0047] 5—groove [0048] 6—supporting surface [0049] 7—bone tissue [0050] 8—technological gripping device [0051] 9—femoral head [0052] 10—friction couple contact surface [0053] 11—limiting surface [0054] 12—pelvic bone [0055] 13—femoral head [0056] 14—insert [0057] H—cutting edge 3 wall thickness [0058] H1—cutting edge 3 height [0059] H2—opposite wall 4 height [0060] α—angle of attack angle of application [0061] β—angle of application [0062] λ—angle of elongation of the femoral head 9 endoprosthesis body [0063] D1—diameter of the femoral head 1 [0064] D2—diameter of the supporting surface 6 [0065] z—distance between pins 2