Source: https://patents.google.com/patent/CA2571672C/en
Timestamp: 2019-05-20 21:08:49
Document Index: 435654130

Matched Legal Cases: ['art 3', 'art 3', 'art 2', 'art 2', 'art 2', 'art 3', 'art 3', 'art 3', 'art 2', 'art 2', 'art 3', 'art 3', 'art 2', 'art 2', 'art 5', 'art 2', 'art 3', 'art 3', 'art 3', 'art 3', 'art 3', 'art 2', 'art 2', 'art 3', 'art 2', 'art 3', 'art 2', 'art 2', 'art.\n2', 'art.\n3', 'art.\n9', 'art.\n10', 'art.\n11', 'art.\n12', 'art.\n13', 'art.\n16', 'art.\n17', 'art.\n20']

CA2571672C - Intramedullary nail - Google Patents
CA2571672C
CA2571672C CA 2571672 CA2571672A CA2571672C CA 2571672 C CA2571672 C CA 2571672C CA 2571672 CA2571672 CA 2571672 CA 2571672 A CA2571672 A CA 2571672A CA 2571672 C CA2571672 C CA 2571672C
CA 2571672
CA2571672A1 (en
2004-06-24 Application filed by Synthes USA LLC filed Critical Synthes USA LLC
2004-06-24 Priority to PCT/CH2004/000389 priority Critical patent/WO2006000109A1/en
2006-01-05 Publication of CA2571672A1 publication Critical patent/CA2571672A1/en
2012-08-28 Publication of CA2571672C publication Critical patent/CA2571672C/en
Disclosed is an intramedullary nail (1) that is made of a metal or a metal alloy and comprises a longitudinal axis (4), a connecting part (2) whose cross section has an orthogonal profile F in relation to the longitudinal axis (4), and a shaft part (3) which is to be inserted into the medulla and whose cross section has an orthogonal profile f < F in relation to the longitudinal axis. The metal or the metal alloy of the shaft part (3) is provided with greater mechanical stiffness than the metal or the metal alloy of the connecting part (2).
Intramedullary Nail The invention relates to an intramedullary nail according to the preamble of Patent Claim l.
US 4,875,474 A (BORDER) discloses an intramedullary nail whose central section has a lower wall thickness due to machining and therefore also has a lower strength, which is a disadvantage, in comparison with the proximal and distal end portions of the intramedullary nail.
US-B 16,261,290 (FRIEDL) discloses a hollow intramedullary nail whose distal shaft part has a smaller wall thibkness than the proximal connecting part. Therefore, the shaft part is more flexible than the connecting part, but here again there is the disadvantage of the lower strength of the shaft part. This is a disadvantage that is further potentiated by the various transverse bores in the shaft part.
The present invention seeks to remedy this situation. The object of the invention is to create an intramedullary nail shaft part is more flexible in comparison with the connecting part while nevertheless having the greatest possible strength.
The invention achieves this object with an intramedullary nail having the features of Claim 1.
Other advantageous embodiments of the invention are cliaracterized in the dependent clainis.
The advantages achieved through the invention may essentially be regarded as the fact that thanks to the inventive intramedullary nail, a high mechanical strength is achieved despite the flexibility imparted to the shaft part. Due to this flexibility, the introduction of the intramedullary nail into the intramedullary canal is facilitated and the greater strength ofthe material reduces the risk of nail breakage.
Another advantage is obtained due to the lower total weight of the nail due to the smaller wall thickness, approx. 30% lower weight versus a nail having a constant wall thickness. Finally, this also yields a more economical manufacturing process for the intramedullary nail because it can be manufactured more rapidly in comparison with the state of the art and no material is lost due to machining by cutting. This is achieved on the one hand due to the fact that it is possible to start with a prefabricated tube and its wall thickness may still be changed while on the other hand the method is faster on the whole than traditional teclmiques of metal working.
In another embodiment of the intramedullary nail, the tensile strength of the shaft part shows an increasing gradient in the radial diiection-from the longitudinal axis or from the wall of the existing cannulation to the surface of the shaft part. This yields the advantage that it is not necessary to insert a mandrel into the cannulation during the cold forming, thus permitting a simpler manufacturing process.
In yet another embodiment, the tensile strength of the shaft part at first shows a declining gradient and then again an increasing gradient in the radial direction-from the outer surface of the shaft to the longitudinal axis or to the wall of the cannulation. In comparison with a method without inserting a mandrel into the cannulation during cold forming, a greater strength of the material can be achieve here on the whole due to the increase in the tensile strength on the inside of the intramedullary nail.
Depending on the embodiment of the intramedullary nail:
- the axial length of the connecting part amounts to at most 30%, prefcrably at most 10% of the total length of the intramedullary nail;
- the surface of the shaft has a maximum rougllness Ro of 1.6 m, preferably max. 0.8 m;
- the metal or the metal alloy of the shaft part has at least a 5% higher meclianical strength than the metal or the metal alloy of the connecting part;
- the metal or metal alloy of the shaft part has a greater strength than the metal or metal alloy of the connecting part;
- the metal or metal alloy of the shaft part has a greater bending strength than the metal or metal alloy of the connecting part;
- the metal or metal alloy of the shaft part has a greater torsional strength than the metal or metal alloy of the connecting part;
- the metal or metal alloy of the shaft part has a greater fatigue strength than the inetal or metal alloy of the connecting part.
In another embodiment of the intramedullary nail, the connecting part and the shaft part had the same composition in terms of materials, so the intramedullary nail can be manufactured in one piece.
In yet another embodiment, the higher mechanical strength of the shaft part is created by cold forming of the mctal or metal alloy. The advantagc herc consists essentially of the simple way of manufacturing the intramedullary nail.
In another embodiment the outside diameter D,,,be, of the cormecting part is larger than the outside diameter Dsn,,n of the shaft part so that only the shaft part need be manufactured by cold forming.
In yet another embodiment the outside diameter D,,,b, of the connecting part is equal to the outside diameter Dsma of the shaft part. The advantage of this embodiment consists of the essentially constant mechanical strength of the intramedullary nail over the entire length.
In another embodiment, it comprises a cannulation that is concentric with the longitudinal axis, preferably in the form of a cylindrical cavity, whereby the wall thickness "W"
of the connecting part is preferably greater than the wall thickness "w" of the shaft part. The wall thickness w conforms to the condition 0.60W < w< 0.85W.
The invention and further embodiments of the invention are explained in greater detail below on the basis of the partially schematic diagrams of several exemplary embodiments.
Figure 1 shows a longitudinal section through an unmachined tube for a first manufacturing variant;
Figure 2 sliows a cross section along line lI-II in Figure 1 and Figure 3;
Figure 3 shows a longitudinal section through an inventive intramedullary nail having a tapering distal portion;
Figure 4 shows a cross section along line III-III in Figure 3;
Figure 5 shows a longitudinal section through an unmachined tube for a second manufacturing variant;
Figure 6 shows a longitudinal section through the partially machined tube according to Claim 5 having a tapered shaft part;
Figure 7 shows a longitudinal section through the completely machined tube according to Figure 6 with a constant outside diameter as the second variant of an inventive intramedullary nail;
Figure 8 shows a diagram of the mechanical strength of the shaft of an inventive intramedullary nail; and Figure 9 shows a diagram of the mechanical strength of the shaft for a variant of an inventive intramedullary nail.
In Figures 1 and 5, an unmachined hollow cylindrical or hollow prismatic tube 10 with an outside diameter D,,,b,: is shown, serving as the starting piece for the intramedullary nail 1. The tube 10 has a cannulation 5 that is coaxial with the longitudinal axis 4 and is surrounded by the tube wall 11. The cross-sectional area F of'the unmachined tube 10 orthogonal to the longitudinal axis 4 is shown in Figure 2.
Figure 3 shows the intramedullary nail 1 after cold fonning. After cold forming, the intramedullary nail I is constricted diametrically on the outside from its distal end 8 on a section A of its length forming the shaft part 3 in comparison with the tube 10 as a starting piece and optiunally, depeuding on the dianreter of the nrandrel inserted into the carurulation 5 during the shaping, its diameter on the inside is also reduced or unchanged. The surface 6 of the shaft part 3 opens with a conical transition into the surface 12 of the connecting part 2.
The cold formed section A of the intrarnedullary nail 1 has a cross-sectional area f orthogonal to the longitudinal axis 4 (Figure 4) which is smaller than the cross-sectional area F. Unformed section B of the intrameduilary nail I adjacent to the proximal end 9 of the intiamedullary nail 1 forms the corurecting part 2 of the intranicdullary nail 1 and has the outside diamcter Diõb~ of the unformed tube 10 (Figure 1). An inside thread 15 is cut into the cannulation 5 in the connecting part 2 from the proximal end. Furthermore, at least one trarrsverse bore 16 with a bore axis running across the longitudinal axis 4 is provided on the connecting part and on the shaft part 3, whereby the angle between the longitudinal axis 4 and the bore axes is typically between 30 and 90 .
Figure 6 shows a blank produced from the tube 10 (Figure 5) and having an outside diameter D,,,b, for another embodiment of the intramedullary nail I. Here again, the tube 10 (Figure 5) has been constricted only on the section A with a length of up to an outside diameter Dsi,ah < Du,bc, as measured from the distal end 8 of the intramedullary nail 1, forming the shaft part 3. The section B of the length of the intramedullary nail I as measured from the proximal end 9 is unformed and also has the outside diameter D,,,b,. The cannulation 5 of the blank is optionally either constricted or unchanged in section A, whereby the design of the cannulation 5 after cold fonning depends on the diameter of the mandrel inserted into the cannulation 5 during the cold forming process.
Figure 7 shows the blank depicted in Figure 6 after a second cold forming which is performed after the shaping of the shaft part 3, which is performed only on section B
that forms the connecting part 2. The connecting part 2 (section B) was compressed radially until its outside diameter corresponded to the outside diameter Dsi,;,n of the shaft part 3. The cannulation tapers in the transition from the shaft part 3 to the connecting part 2 and has a smaller= diameter here in the connecting part 2 than in the shaft part 5. Furthermore, an inside thread 15 is cut in the cannulation 5 in the connecting part 2 from the proximal end 9.
Figure 8 shows a plot of the tensile strength Rm in the tube wall t 1 of the cold-formed shaft part 3. The tensile strength Rm increases in this case in the radial direction from the wall 7 of the cannulation 5 to the surface 6 of the shaft part 3. Such a plot of the tensile strength Rm in the tube wall 11 after cold forming is characteristic of cold forming without the insertion of a mandrel into the cannulation 5.
Figure 9 shows another plot of the tensile strength Rm after the cold forming is concluded. The tensile strength R. in this case has a maximum at the wall 7 of the cannulation 5 and at the surface 6 of the shaft part 3 while a minimum tensile strength R. prevails at the center of the tube wall 11. This plot of the tensile strength R. in the tube wall 11 after cold forming is characteristic of cold forming with insertion of a mandrel into the cannulation 5.
Two different manufacturing methods for the inventive intramedullary nail are given below.
Example 1 The present example corresponds to Figures 1 through 4.
A hollow cylindrical or hollow prismatic tube 10 made of stainless steel with a length of typically 100 to 400 mm, an outside diameter of typically 10 to 14 mm and a wall thickness between 1.5 and 4.0 mm is machined over a section A of 70% to 90% of the tube length on the outside by cold forming, said section A corresponding approximately to the shaft part 3 of the intramedullary nail 1, so that its outside diameter is reduced to values between 8 and 12 mm and thus the tube 10 is lengthened by 20% to 40%, i.e., is brought to a final length of 120 to 500 mm..
By inserting a mandrel with an outside diameter of 5 mm to 10 mm into the cannulation 5 of the tube 10 during the cold forming, the wall thickness of the tube 10 is reduced to 1 to 3 mm.
In comparison with the strength values (R,,, between 500 and 800 MPa) of the unmactuned tube 10, the tube 10 machined according to this invention has 5% to 20% higlier strength values (Rm values between 600 and 1000 MPa). The blank obtained in this way is processed by applying transverse bores 16 in the shaft part 3 and in the unmachined remainder of the tube, i.e., in tlu connecting part 2 and a coaxial inside thread 15 in the cannulation 5 in the connecting part 2 to form an intramedullary nail 1.
Example 2 The present example corresponds to Figures 5 through 7.
A tube 10 made of stainless steel with a length of typically 100 to 400 mm, an outside diameter of typically 11 to 17 mm and a wall thickness between 1.5 and 4.0 mm is machined by cold forming over a section A of 70% to 90% of the tube length corresponding approximately to the shaft part 3 of the intramedullary nail 1, so that its outside diameter is reduced to values between 11 and 15 mm and thus the tube 10 is lengthened by 20% to 40%, i.e., brought to a final length of 120 to 500 mm.
By inserting a mandrel into the interior of the tube 10, its wall thickness is also reduced to values between I and 3 mm. In comparison with the strength values (Rm between 500 and 800 MPa) of the unmachined tube 10, the tube 10 machined according to the present invention has 5% to 20%
higher strength values (R. values between 600 and 1000 MPa).
In another method step, the mandrel in the interior of the tube 10 is removed and the previously unmachined connecting part 2 of the tube 10 is shaped so that the entire tube 10 has a constant outside diameter. A lower increase in strength occurs in this connecting part because the material can move freely on the inside of the tube. The blank obtained in this way is processed to yield an intramedullary nail I by creating transverse bores 16 in the shaft part 3 and the connecting part 2 as well as a coaxial inside thread 15 in the cannulation 5 of the connecting part 2.
1. Intramedullary nail made of a metal or metal alloy, comprising A) a longitudinal axis;
B) a connecting part having a cross-sectional profile F orthogonal to the longitudinal axis and C) a shaft part having a surface and intended for insertion into the intramedullary canal, having a cross-sectional profile f < F orthogonal to the longitudinal axis, characterized in that D) the metal or the metal alloy of the shaft part has a greater mechanical strength than the metal or the metal alloy of the connecting part.
2. Intramedullary nail according to Claim 1, characterized in that the tensile strength R m of the shaft part has an increasing gradient in the radial direction-from the longitudinal axis to the surface of the shaft part.
3. Intramedullary nail according to Claim 1, characterized in that the tensile strength R m.
of the shaft part has a gradient that first decreases and then increases again in the radial direction-from the surface of the shaft part toward the longitudinal axis.
4. Intramedullary nail according to any one of Claims 1 through 3, characterized in that the axial length of the connecting part is at most 30% of the total length of the intramedullary nail.
5. Intramedullary nail of claim 4, wherein the axial length is at most 10% of the total length of the intramedullary nail.
6. Intramedullary nail according to any one of Claims 1 through 5, characterized in that the surface of the shaft has a maximum roughness R a of 1.6 µm.
7. Intramedullary nail of claim 6, wherein the maximum roughness is 0.8 µm.
8. Intramedullary nail according to any one of Claims 1 through 7, characterized in that the metal or metal alloy of the shaft part has a mechanical strength at least 5% greater than that of the metal or metal alloy of the connecting part.
9. Intramedullary nail according to any one of Claims 1 through 8, characterized in that the metal or metal alloy of the shaft part has a higher tensile strength than the metal or metal alloy of the connecting part.
10. Intramedullary nail according to any one of Claims 1 through 9, characterized in that the metal or metal alloy of the shaft part has a higher bending strength than the metal or metal alloy of the connecting part.
11. Intramedullary nail according to any one of Claims 1 through 10, characterized in that the metal or metal alloy of the shaft part has a higher torsional strength than the metal or metal alloy of the connecting part.
12. Intramedullary nail according to any one of Claims 1 through 11, characterized in that the metal or metal alloy of the shaft part has a higher fatigue strength than the metal or metal alloy of the connecting part.
13. Intramedullary nail according to any one of Claims 1 through 12, characterized in that the connecting part and the shaft part each have the same composition in terms of the material.
14. Intramedullary nail according to any one of Claims 1 through 13, characterized in that the greater mechanical strength of the shaft part is achieved by cold forming of the metal or metal alloy.
15. Intramedullary nail according to any one of Claims 1 through 14, characterized in that the outside diameter D tube of the connecting part is greater than the outside diameter D shaft of the shaft part.
16. Intramedullary nail according to any one of Claims 1 through 14, characterized in that the outside diameter D tube of the connecting part the same as the outside diameter D shaft of the shaft part.
17. Intramedullary nail according to any one of Claims 1 through 16, characterized in that it has a cannulation concentric with the longitudinal axis.
18. Intramedullary nail according to claim 17, having the form of a cylindrical cavity.
19. Intramedullary nail according to Claim 17 or 18, characterized in that the wall thickness "W" of the connecting part is greater than the wall thickness "w" of the shaft part.
20. Intramedullary nail according to Claim 19, characterized in that the wall thickness w conforms to the condition 0.60W < w < 0.85W.
21. Method for manufacturing an intramedullary nail according to any one of Claims 1 through 20, characterized by cold forming of the shaft part of a rod or a tube having a constant cross-sectional area F intended for insertion into the intramedullary canal such that the cross-sectional area F of the shaft part is reduced to f < F.
22. Method according to Claim 21, characterized in that the outside diameter of the tube remains constant and a reduction in wall thickness of the shaft part is achieved by cold forming.
23. Method according to Claim 22, characterized in that the wall thickness of the shaft part is reduced by the cold forming and at the same time the shaft part is lengthened axially and its outside diameter is reduced.
CA 2571672 2004-06-24 2004-06-24 Intramedullary nail Expired - Fee Related CA2571672C (en)
PCT/CH2004/000389 WO2006000109A1 (en) 2004-06-24 2004-06-24 Intramedullary nail
CA2571672A1 CA2571672A1 (en) 2006-01-05
CA2571672C true CA2571672C (en) 2012-08-28
ID=34957775
CA 2571672 Expired - Fee Related CA2571672C (en) 2004-06-24 2004-06-24 Intramedullary nail
US (1) US20070156144A1 (en)
EP (1) EP1758514B1 (en)
AT (1) AT407635T (en)
CA (1) CA2571672C (en)
DE (1) DE502004008054D1 (en)
WO (1) WO2006000109A1 (en)
2004-06-24 CA CA 2571672 patent/CA2571672C/en not_active Expired - Fee Related
2004-06-24 EP EP20040738030 patent/EP1758514B1/en not_active Expired - Fee Related
2004-06-24 DE DE200450008054 patent/DE502004008054D1/en active Active
2004-06-24 WO PCT/CH2004/000389 patent/WO2006000109A1/en active IP Right Grant
2004-06-24 AT AT04738030T patent/AT407635T/en not_active IP Right Cessation
2006-12-21 US US11/645,322 patent/US20070156144A1/en not_active Abandoned
CA2571672A1 (en) 2006-01-05
EP1758514B1 (en) 2008-09-10
AT407635T (en) 2008-09-15
US20070156144A1 (en) 2007-07-05
EP1758514A1 (en) 2007-03-07
WO2006000109A1 (en) 2006-01-05
DE502004008054D1 (en) 2008-10-23
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