Implantable system with elastic components

Abstract

A system (100) for a controlled stressing of a reconstructed or re-natured ligament of a human or animal body comprises an anchoring element (10) for implantation in a first bone (50), at least one connecting element (120) and a holding element (30), which fixes the at least one connecting element (20) in a second bone. According to the invention, an elastomer element (125) is arranged in the anchoring element and/or in the connecting element (120) and provides a defined elastic action through the cooperation of elastomer element (125) with the connecting element (120).

Claims

1. A system for controlled stressing of a reconstructed or re-natured ligament of a human or animal body, comprising: an anchoring element configured to be implanted in a first bone; a connecting element; a holding element configured to hold the connecting element in a second bone; and an elastomer element configured to fit in an interior of an outer element of the anchoring element between a contact surface on a base of the outer element and a sleeve to which the connecting element is fixed, and wherein the elastomer element cooperates with the anchoring element to lead to a defined elasticity of the system similar to an elastic curve of a natural ligament with a first region in which a course of a strain characteristic is flat and a second region in which the course of the strain characteristic is progressive, wherein at a start of a tensile stress, the elastomer element continuously fills free volume in the interior reflecting the flat course of the strain characteristic, and wherein as soon as the elastomer element almost fills the entire volume of the interior, the progressive course of the strain characteristic of the system starts due to non-compressibility of the elastomer element.

2. The system of claim 1, wherein a second elastomer element is configured to fit in the connecting element so that the second elastomer element is connected to the anchoring element or the holding element by means of the connecting element.

3. The system of claim 2, wherein the second elastomer element provides a smaller elastic modulus than the connecting element.

4. The system of claim 2, wherein the connecting element comprises a tubular shape and the second elastomer element is configured to fit in a portion of an axial cavity of the connecting element.

5. The system of claim 1, wherein the connecting element is plaited, twisted, knitted, or woven from a plurality of first individual fibers and a part of the first individual fibers enclose an angle ranging between 5° and 85° relative to a longitudinal axis of the connecting element.

6. The system of claim 5, further comprising a second elastomer element comprising a plurality of second individual fibers plaited, knitted, woven twisted, or spun with the first individual fibers to form the connecting element.

7. The system of claim 1, wherein the connecting element is configured to fit in an axial recess of the elastomer element.

8. An anchoring device for an implantable system, comprising: an anchoring element configured to be implanted in a first bone; and a connecting element configured to pass through a first bone tunnel and connect with the anchoring element, the connecting element also configured to pass through a second bone tunnel and connect with a holding element; and an elastomer element configured to fit in an interior of an outer element of the anchoring element between a contact surface on a base of the outer element and a sleeve to which the connecting element is fixed, and wherein the elastomer element cooperates with the anchoring element to lead to a defined elasticity of the system similar to an elastic curve of a natural ligament with a first region in which a course of a strain characteristic is flat and a second region in which the course of the strain characteristic is progressive, wherein at a start of a tensile stress, the elastomer element continuously fills free volume in the interior reflecting the flat course of the strain characteristic, and wherein as soon as the elastomer element almost fills the entire volume of the interior, the progressive course of the strain characteristic of the system starts due to non-compressibility of the elastomer element.

9. The device of claim 8, wherein a second elastomer element is configured to fit in the connecting element so that the second elastomer element is connected to the anchoring element or the holding element by means of the connecting element.

10. The device of claim 9, wherein the second elastomer element provides a smaller elastic modulus than the connecting element.

11. The device of claim 9, wherein the connecting element comprises a tubular shape and the second elastomer element is configured to fit in a portion of an axial cavity of the connecting element.

12. The device of claim 8, wherein the connecting element is plaited, twisted, knitted, or woven from a plurality of first individual fibers and a part of the first individual fibers enclose an angle ranging between 5° and 85° relative to a longitudinal axis of the connecting element.

13. The device of claim 12, further comprising a second elastomer element comprising a plurality of second individual fibers plaited, knitted, woven twisted, or spun with the first individual fibers to form the connecting element.

14. The device of claim 8, wherein the connecting element is configured to fit in an axial recess of the elastomer element.

Description

(1) The invention is described in the following with reference to exemplary embodiments and explained in greater detail on the basis of the drawings. The drawings show:

(2) FIG. 1 a system according to the invention implanted in a knee joint in a schematic view;

(3) FIG. 2 a schematic view of a strain characteristic of a soft, biological tissue by comparison with other materials;

(4) FIG. 3A a first exemplary embodiment according to the invention of a connecting element with elastomer element in a schematic view;

(5) FIG. 3B a second exemplary embodiment according to the invention of a connecting element with elastomer element in a schematic view;

(6) FIG. 4 a sectional view through a first exemplary embodiment of an anchoring element according to the invention with an elastomer element;

(7) FIG. 5 a section through a second exemplary embodiment of an anchoring element according to the invention with elastomer element; and

(8) FIG. 6 a section through a third exemplary embodiment of an anchoring element according to the invention with tongue-shaped elastomer element.

(9) FIG. 7. depicts other embodiments of an implantable system implanted in a knee joint in a schematic view.

(10) Similar parts are marked with the same reference signs in all Figures.

(11) FIG. 1 shows the system 100 according to the invention inserted into a flexed human knee joint. The anchoring element 10 in the exemplary embodiment is screwed ventrally into the proximal region of the tibia bone 50, which is joined by a first bone tunnel 51 which leads to the interior 60 of the joint. A narrow second bone tunnel 41 is drilled through the adjacent distal end of the femur bone 40. The connecting element 20 is fixed there to a holding element 30. In this context, the holding element is supported on the outer surface of the femur bone 40. The connecting element leads through the second bone tunnel 41 via the interior 60 of the joint and the first bone tunnel 51 to the connecting element and is fixed by the latter. In a similar system shown in the embodiments of FIG. 7, a connecting element 120 is attached to the holding element 30 and the anchoring element 10 through the first bone tunnel 51 and second bone tunnel 41.

(12) FIG. 2 shows a diagram with strain characteristics of different materials in which the stress present is plotted against a given strain. Characteristic 71 represents the typical strain characteristic of soft biological tissue, such as a human ligament. The spring characteristic 72 was recorded in a rubber-elastic polymer, the line 73 in tempering steel. As shown in the diagram, elastomers provide a progressive strain characteristic similar to that of soft biological tissue. The elastic modulus respectively the cushioning constant, which are specified by the gradient of the curve, provides a similar, relatively flatter course with a slight strain. However, the progression begins only with a relatively greater strain and with reduced thickness. By contrast, metallic elements, such as tempering steel, provide an elastic modulus which approaches the spring characteristic in the rear progressive range.

(13) It was surprisingly shown that the elastic modulus of an elastomer element which is integrated in a tubular connecting element or otherwise cooperates with the connecting element can be approximated to the strain characteristic of a natural ligament.

(14) FIG. 3A represents a tubular connecting element 120 in the axial hollow cavity 122 of which an elastomer element 125 is arranged, which is shown once again separately above the connecting element by way of explanation. A cylindrical elastomer element 125 with a length l of preferably 20 mm-100 mm, for example, 60 mm, and with a diameter of preferably 0.5 mm to 10 mm, for example, 2 mm is integrated in an exemplary 120 mm long tubular connecting element 120. The connecting element 120 comprises a plurality of first individual fibres 121, which are knitted, plaited, woven, twisted, and/or turned to form a tubular connecting element 120.

(15) In this context, the first individual fibres 121 preferably comprise polyethylene and/or polyester. The connecting element 120 can be manufactured from first individual fibres 121 of a single material, but also from first individual fibres 121 of different materials. In this context, these individual fibres 121 are orientated at an angle τ 123 relative to the longitudinal axis 124 of the connecting element 120. Through the cooperation of the elastomer element 125 with the tubular connecting element 120, the connecting element 120 shows a large extension with a small tensile force, that is, a low elastic modulus, which increases strongly as soon as the angle τ 123 between the individual fibres 121 and the longitudinal axis 124 is reduced respectively tends towards zero. The angle τ is preferably disposed between 5° and 85°, by particular preference between 35° and 55°.

(16) FIG. 3B shows a connecting element 120′ in which the elastomer element is embodied from a plurality of second individual fibres 126. These are spun together with the first individual fibres 121 to form a connecting element 121′, preferably without axial cavity. However, the connecting element 121′ can also be plaited, knitted, twisted, spun and/or woven and can provide an axial cavity.

(17) FIGS. 4-6 each show an anchoring element 110, 110′, 110″ in which an elastomer element 115, 117, 119 acts as a cushioning element. An anchoring element 110, 110′, 110″ provides, for example, a cylindrical outer element 103, which is embodied in a pot shape and in the base 105 of which an opening 112 is introduced. The cylindrical outer element 103 comprises, for example, an outer thread with which the anchoring element is screwed into the first bone 50, see FIG. 1. At the open end-face 104 of the outer element 103, a sleeve 114 is introduced, which is mounted in a displaceable manner in the interior of the outer element. The sleeve 114 provides a fastening element 111, which comprises, for example, two conical segments. Between the inner surfaces 118 of the fastening element 111, the connecting element 20 is fixed in a non-slip manner. In the event of a tensile stress, the fastening element 111 itself is pressed against the diametrically opposed contact surfaces 113 of the sleeve 114 and is accordingly rigidly fixed in the sleeve 114.

(18) In FIG. 4, an elastomer element 115 is disposed between the contact surface 101 of the outer element 103 and a parallel contact surface of the sleeve 114 disposed opposite. The elastomer element 115 does not fill the interior 102 completely, especially in the radial direction. The elastomer element 115 provides a coaxial recess 116, through which the connecting element 20 is guided and leaves through the opening 112 of the anchoring element in the direction towards the bone tunnel 51.

(19) At the start of a tensile stress, the elastomer element 115 continuously fills the free volume in the interior 102, which is reflected in a flat course of the strain characteristic shown by curve 72 in FIG. 2. As soon as the elastomer element 115 almost fills the entire volume, though, an exponential rise occurs in the curve because of the non-compressibility of the elastomer, allowing the desired progressivity corresponding to the curve 71 in FIG. 2 to be obtained.

(20) FIG. 5 shows an anchoring element 110′ which is constructed with regard to the outer element 103 and sleeve 114 corresponding to the anchoring element 110. Once again, an elastomer element 119 is introduced into the interior 102 of the outer element 103. The elastomer element 119 provides a cylindrical shape. The base surface of the elastomer element is preferably round, but can also be embodied to be oval or angular. The connecting element 20 is now guided in a screw shape respectively spiral shape around the periphery of the elastomer element 119 and leaves the anchoring element 110′ via the opening 112 in the base 105 of the outer element 103.

(21) If a tensile stress now acts on the connecting element 20, this tensile force is transmitted through the connecting element in the radial direction to the elastomer element 119. At the start of the tensile stress, the elastomer element 119 can be compressed and, in the case of a continuing tensile stress, reaches its minimal volume and is then incompressible. A compression of the elastomer element 119 in the axial direction takes place only to a small extent because the majority of the tensile force is used for the compression of the elastomer element 119 in the radial direction.

(22) To eliminate the additional axial compression through the sleeve 114, the sleeve 114 can be fixed immovably in the outer element, as .B. shown in FIG. 6. This leads to a less steep rise of the spring characteristic.

(23) To prevent a slipping of the connecting element 20 on the periphery of the elastomer element 119, grooves, which are not illustrated, can be introduced peripherally into the elastomer element in which the connecting element 20 is placed and guided.

(24) FIG. 6 shows a further exemplary embodiment of the cushioning device through an elastomer element 117 which is formed by a plurality of tongue-shaped protrusions 117a, 117b. These protrusions 117a, 117b are arranged offset in the axial direction in the interior 106 of the outer element 103 and formed radially inwards. They extend radially beyond the axis of the anchoring element 110′ and are distanced from one another in the axial direction. The connecting element 20 is held by the fastening element 118 and further guided around the tongue-shaped protrusions 117a, 117b to the opening 112.

(25) At the start of a tensile stress, the protrusions 117a, 117b are deformed in the axial direction towards the base 105 of the outer element 103. Once again, this corresponds to the flat region of the strain characteristic of curve 72 in FIG. 2. With increasing tensile stress, the connecting element 20 is clamped between the protrusions 117a, 117b now arranged in contact with one another. If the protrusions 117a, 117b have been deformed maximally until contact on the base 105 of the outer element 103, no further compression is possible. This corresponds to the progressive course of the strain characteristic 71 in FIG. 2.

(26) The rise and the commencement of the progressive region of the strain characteristic can be varied through the selection of the material for the elastomer element 115, 117, 119. Suitable materials for the elastomer element 115, 117, 119 are polyethylene, polyester, polyurethane or silicon or a mixture of the named materials. Furthermore, the strain characteristic is determined by the free volume in the interior 102 of the outer element 103 and the shape, the diameter and the length of the elastomer element 115, 117, 118.

(27) All of the features described and/or designated can be advantageously combined with one another within the scope of the invention. The invention is not restricted to the exemplary embodiments described.