Title of Invention

"A DEVICE FOR FRACTURE TREAMENT ON BONES AND/OR FOR FIXING SURGICAL IMPLANTS"

Abstract

The device according to the invention is used for fracture treatment on bone and/or for fixing surgical implants, surgical threads or tissues in or on bone and essentially comprises a closing element (1) and a rivet (2) which comprises, extending coaxially to a central axis (6), a rivet shank (3), a rear end portion (18) which intersects said central axis (6), a shank front end portion (7) which is axially opposed to said rear end portion (18) , and a through hole (5) which coaxially penetrates the rivet (2), so that the shank (10) of the closing element (1) is coaxially displaceable within the through hole (5) and the head (11) may be axially brought to rest on the shank front end portion (7) . The rivet shank (3) also comprises at least two grooves (9) arranged on the outside surface thereof and extending parallel to the central axis (6) from the shank front end portion (7) in the direction of the rear end portion (18).

Full Text

The present invention relates to a device for fracture treatment on bones and/or for fixing surgical implants. Device for fixing surgical implants The invention relates to a device for fracture treatment on bone and/or for fixing surgical implants, surgical sutures or tissues in or on bone as claimed in the precharacterising part of claim 1. For surgical fracture treatment on bone or for fixing surgical implants, sutures or tissues in or on bone, it is - also possible to use rivets, in particular blind rivets. Rivets having closing heads formed by separate and comparatively widely spreadable legs are particularly adequate in this respect. Blind rivets of this type for non-medical applications are known for example from GB 2 054 082 TUCKER FASTENERS. The anchoring legs are formed by axially severing the wall of the rivet shank on the front end portion of the blind rivet by means of a pyramidally shaped, sharp-edged closing head which is inserted into the hollow cylindrical rivet shank from the front end thereof. These known blind rivets suffer from the disadvantage of being limited to utilisation in soft materials and of necessitating strong closing forces for the closing head to be formed in the blind rivet. The invention is intended to provide a remedy for this. It is accordingly an object of the invention to provide a fixation means suitable for medical purposes, in particular a blind rivet apt to be utilised in surgery, which allows the use of materials of higher density, such as titanium, and which may be fixed in place by using closing forces that are acceptable in surgery. According to the invention, this object is achieved by means of a device for fracture treatment and/or for fixing surgical implants, surgical sutures or tissues in or on bone, which show the features of claim 1. The inventive device comprises essentially A) a closing element having a shank and, formed in the end portion thereof, a head rigidly joined to the shank or attachable to the shank by means of a screwed joint; and B) a rivet which comprises a rivet shank extending coaxially to a central axis and a through hole passing coaxially through the rivet. The shank of the closing element is coaxially displaceable within the through hole so that the head may be brought to rest against the front end portion of the shank. The head and the shank of the closing element may be realised either in two parts or in one part. The rivet shank further comprises at least two grooves formed in the outside portion thereof which run from the shank front end portion towards the rear end of the rivet, extending parallel to the central axis over a length L. The grooves mark design rupture sites, ensuring that the rivet shank on part of its total length is severed into a number of anchoring legs by the head of the closing element, as the closing element is further displaced in the direction of the rivet head. The ratio between the length L and the total length of the rivet shank is comprised between 20 and 90 percent, so that the anchoring legs are allowed to radially spread over a surface F which may be from three times to twenty times the cross-sectional area of the rivet shank. In the preferred embodiment of the device according to the invention, the rivet shank comprises slits extending parallel to the central axis and leading, on the one hand, to the opening of the through hole on the shank front end portion and, on the other hand, to said grooves. These slits facilitate the severing of the rivet shank. In another embodiment of the device according to the invention, the rivet comprises a rivet head formed in the rear end portion thereof which may be rigidly joined to the rivet or may, for example, be attachable to the shank by means of a threaded joint. In another embodiment of the device according to the invention, the materials characteristics of the rivet material lie within benchmark figures for tensile strength (Rm in N/mm2) related to elongation at break (A5 in %) that are in a range of between 10 ; 1 and 50 : 1, preferably between 10 : 1 and 30 : 1. In yet another embodiment of the device according to the invention, the geometric dimensions of the rivet are chosen in such a way that the ratio between the outside diameter da of the rivet shank and the diameter d of the through hole is in a range of between 1.1 : 1 and 2.5 : 1, preferably between 1.5 : 1 and 2:1. The ratio between the radial depth t of the grooves and the wall thickness of the rivet shank is suitably in a range of between 1 : 1.2 and 1 : 2.5, preferably between 1 : 1.7 and 1 : 2.3. The wall thickness may be determined from the difference between the outside diameter da and the diameter d. Rivets provided with these geometrical proportions will have geometrical dimensions that are comprised between the following benchmark figures: outside diameter da of the rivet shank: 2 to 12 mm, preferably 3 to 8 mm; diameter d of the through hole: 1 to 8 mm, preferably 1.5 to 5 mm; wall thickness of the rivet shank: 0.2 to 4 mm, preferably 0.5 to 2 mm; and radial depth t of the grooves: 0.1 to 3 mm, preferably 0.2 to 1 mm. In a further embodiment of the device according to the invention, the grooves, considered perpendicularly to the central axis, have a triangular cross-section, the triangle's angle of point formed in the bottom of the groove being in a range of between 30 and 80 degrees, preferably between 40 and 7 0 degrees. The number of grooves distributed in a uniform manner about the circumference of the rivet shank is suitably between 3 and 8, preferably between 3 and 5. The number of grooves will also determine the number of anchoring legs of the device, once the rivet is in a fixed position. Preferably, the rivet is made of a metallic material and comprises the following materials or alloys, respectively: a) materials based on iron, preferably steel; b) materials based on titanium, preferably Ti c.p. and titanium alloys; c) materials based on cobalt, preferably cobalt alloys; d) materials based on tantalum, preferably tantalum alloys; and e) materials based on zircon, preferably zircon alloys. Further advantageous embodiments of the invention will be characterised in the dependent claims. The advantages achieved by the present invention consist essentially in the fact that due to the device according to the invention: - it is possible to achieve a more homogeneous transmission of force into the bone; and - it is possible to obtain a better anchorage than with bone screws, even in cases of poor bone quality. In the following, the invention and improvements of the invention will be illustrated in greater detail with reference to the partially diagrammatic representations of several embodiments. In the drawings: Fig. 1 shows a view of the device according to the invention; Fig. 2 is a longitudinal section of the embodiment of the inventive device shown in Fig. 1; Fig. 3 shows a sectional view according to line 1-1 of the embodiment of the inventive device shown in Figs. 1 and 2; Fig. 4 shows a perspective view of the embodiment of the inventive device shown in Figs. 1 to 3; and Fig. 5 is a longitudinal section of another embodiment of the device according to the invention. Fig. 1 shows a rivet 2 and a closing element 1 according to one embodiment of the inventive device. The rivet 2 has a central axis 6 and consists of a cylindrical rivet shank 3 which needs not necessarily be circular cylindrical and which runs parallel to the central axis 6, a rivet head 4 rigidly joined to the rivet shank 3, and a cylindrical through hole 5 penetrating the rivet 2 coaxially along the central axis 6. The rivet shank 3 has an outside diameter da and comprises grooves 9 extending parallel to the central axis 6, running from the shank front end portion 7 over a length L and having a depth t measured from the outer lateral surface 14. The depth t is such that the wall thickness, as defined by the diameters da and d, and by the depth t, allows the rivet 2 to be severed, along the anchoring portion, into separate anchoring legs 13 (Fig. 4), as the rivet 2 is closed by means of the closing element 1, the number of anchoring legs 13 corresponding to the number of grooves 9 arranged on the outer lateral surface 14 of the rivet 2. In the embodiment of the rivet 2 shown here, the wall thickness of the rivet shank 3 corresponds to 14 percent of the outside diameter da. From the fr.ont end face 15 of the rivet shank 3, slits 12 running parallel to the central axis 6 penetrate the rivet shank 3, and on the side of the shank front end portion 7 lead to the through hole 5, whereas on the opposite side, running parallel to the central axis 6, they lead to the grooves 9. The closing element 1 comprises a shank 10 extending parallel to the central axis 6 and a head 11, located on the end portion thereof, which has a frusto-conical form and leads to the shank 10. The closing of the rivet 2 is realised by means of the closing element 1 after the rivet 2 has been inserted, for example, into a bone plate and a bone (not shown) . The head 11 of the closing element 1 has a diameter D which is superior to the diameter d of the through hole 5, so that the head 11 of the closing element 1, by means of a tensile force exerted on the shank 10, is pressed into the inner cone 8 (Fig. 2) of the through hole 5. As the widening, frusto-conical head 11 of the closing element 1 is pressed into the inner cone 8 (Fig.2) formed in the through hole 5, the wall 20 (Fig.2) of the rivet shank 3 is widened and, as the head 11 of the closing element 1 further advances, is severed into the anchoring legs 13 (Fig. 4) at the design rupture sites formed by the grooves 9. Fig. 2 shows the rivet 2 belonging to the embodiment of the inventive device described above. The rivet 2 comprises a central axis 6, a circular cylindrical rivet shank 3 including a shank front end portion 7 intersecting the central axis 6, and an equally circular cylindrical rivet head 4 arranged on the rear end portion 18 intersecting the central axis 6. The shank front end portion 7 is provided with an end face 15 extending perpendicularly to the central axis 6. The rivet head 4 has a convex or frusto- conical portion tapering towards the shank front end 7, which leads to the rivet shank 3, and an equally convex or frusto-conical portion tapering towards the rear end face 19 arranged on the rear end portion 18 of the rivet 2. A through hole 5 is arranged coaxially to the central axis 6 and penetrates the rivet 2 from the shank front end portion 7 to the rear end portion 18. On the shank front end portion 7, the through hole 5 is enlarged by the inner cone 8 and leads to the front end face 15. Grooves 9 are arranged parallel to the central axis 6 which penetrate the rivet shank 3 from the shank front end portion 7 to a length L (Fig. 1) and which have a V-shaped cross-section (Fig. 3) when considered perpendicularly to the central axis 6. In addition, slits 12 extending equally parallel to the central axis 6 penetrate the rivet shank 3 from the front end face 15. Considered perpendicularly to the central axis 6, these slits 12 have a rectangular cross-section (Fig. 1), whereas they are shaped in the form of a segment of a circle when considered parallel to the central axis 6. The slits 12 extend parallel to the central axis 6 and lead to the front end face 15, to the outer lateral surface 14,' and to the grooves 9. Fig. 4 shows the rivet 2 including the central axis 6, the rivet head 4, the enlarged rivet shank 3 and the closing element 1 in a closed condition of the rivet 2. The rivet shank 3 is spread apart over a length L (Fig. 1) and comprises three anchoring legs 13. Fig. 5 shows an embodiment of the rivet 2 which differs from the embodiments shown in Figs. 1 and 2 only in so far as the rivet 2 comprises no rivet head 4 (Fig. 1 and 2) formed in its rear end portion 18. Furthermore, the closing element 1 penetrates the rivet 2 only or. part of its total length and has a bore 21 penetrating the closing element 1 coaxially, said bore 21 being provided with a coaxial, internal screw thread 23 formed in the end portion 22 axially opposite to the head 11. A Kirschner wire 24 is threadably insertable into this internal screw thread and rnay be removed again from the internal screw thread 2 3 after the closing of the rivet 2. We claim: 1. A device for fracture treatment on bones and/or for fixing surgical implants, surgical sutures or tissues in or on the bone including a rivet [2] which comprises, extending coaxially to a central axis [6], a rivet shank [3] having an outer lateral surface [14], a rear end portion [18] intersecting the central axis [6], a shank front end portion [7] axially opposite to the rear end portion [18], and a through hole [5] coaxially penetrating the rivet [2], wherein the rivet shank [3] comprises at least two grooves [9] running parallel to the central axis [6] which extend from the shank front end portion [7] over a length L in the direction of the rear end portion [18] and which have a radial depth t, measured from the outer lateral surface [14], characterized in that the materials characteristics of the material of the rivet [2] lie within benchmark figures for tensile strength [Rm in N/mm2] as related to elongation at break [A5 in %] of between 10:1 and 50:1. 2. A device as claimed in claim 1 wherein the ratio between the length L and the total length of the rivet shank is comprised between 20 and 90 percent. 3. A device as claimed in claim 1 or 2 wherein the rivet shank [3] comprises slits [12] which on the shaft front end portion [7] lead to the through hole [5], whereas on the other hand they extend parallel to the central axis [6] and lead to the grooves [9]. 4. A device as claimed in any of the claims 1 to 3, wherein the range of the ratio of tensile strength [Rm in N/mm2] as related to elongation at break [A5 in %] is comprised between 10:1 and 30:1. 5. A device as claimed in any of the claims 1 to 4, wherein the ratio between the outside diameter da of the rivet shank [3] and the diameter d of the through hole [5] is in a range of between 1.1:1 and 2.5 :1. 6. A device as claimed in claim 5, wherein the ratio between the outside diameter da of the rivet shank [3] and the diameter d of the through hole [5] is in a range of between 1.5:1 and 2:1. 7. A device as claimed in any of the claims 1 to 6 wherein the ratio between the radial depth t of the grooves [9] and the wall thickness of the rivet shank [3] is in a range of between 1: 1.2 and 1 : 2.5. 8. A device as claimed in claim 7, wherein the ratio between the radial depth t of the grooves [9] and the wall thickness of the rivet shank [3] is in a range of between 1 : 1.7 and 1 : 2.3. 9. A device as claimed in .-any of the claims 1 to 8, wherein it comprises a closing element [1] having a shank [10] and a head [11] formed in the end portion thereof, so that the shank [10] of the closing element [1] is coaxially displaceable within the through hole [5] and that the head [11] may be axially brought to rest on the shaft front end portion [7]. 10. A device as claimed in any of the claims 1 to 9 wherein the rivet [2] comprises a rivet head [4] formed on the rear end portion [18] thereof.

Documents:

293-delnp-2003-abstract.pdf

293-delnp-2003-assignment.pdf

293-delnp-2003-claims.pdf

293-delnp-2003-complete specification (as filed).pdf

293-delnp-2003-complete specification (granted).pdf

293-DELNP-2003-Correspondence Others-(23-09-2011).pdf

293-DELNP-2003-Correspondence-Others (09-11-2009).pdf

293-delnp-2003-Correspondence-Others-(07-04-2011).pdf

293-DELNP-2003-Correspondence-Others-(23-03-2010).pdf

293-DELNP-2003-Correspondence-Others-(30-03-2010).pdf

293-delnp-2003-correspondnece-others.pdf

293-delnp-2003-correspondnece-po.pdf

293-delnp-2003-description (complete).pdf

293-delnp-2003-drawings.pdf

293-DELNP-2003-Form-1-(23-09-2011).pdf

293-DELNP-2003-Form-1.pdf

293-delnp-2003-form-13.pdf

293-delnp-2003-form-19.pdf

293-delnp-2003-form-2.pdf

293-delnp-2003-form-3.pdf

293-delnp-2003-form-6.pdf

293-DELNP-2003-GPA-(23-03-2010).pdf

293-DELNP-2003-GPA-(30-03-2010).pdf

293-delnp-2003-gpa.pdf

293-delnp-2003-petition-137.pdf