This application is the US-national stage of PCT application PCT/FR2010/000094 filed 9 Feb. 2010, published 12 Aug. 2010 as WO2010/089481, and claiming the priority of French patent application 0900557 itself filed 9 Feb. 2009, whose entire disclosures are herewith incorporated by reference.
The invention relates to a screw for osteosynthesis and arthrodesis for orthopedic surgery.
It finds a particularly important, although not exclusive, application in the field of anchors for orthopedic surgery of the hand and of the foot, more particularly at the phalanxes of the fingers and of the toes, but also of the metacarpals and metatarsals and notably for corrective surgery for the hand and for the foot.
Note than an osteosynthesis anchor must be used to keep in place two (or more) portions of one and the same bone fractured or cut by a surgical operation (osteotomy) for the time necessary for this bone to consolidate (typically three months).
An arthrodesis for its part is the immobilization of an articulation by surgical means in order to weld two bones into a single bone, by means of an osteosynthesis device.
In general the object of any osteosynthesis, and particularly in the case of an arthrodesis, is to seek a very good stability of the anchor in order to obtain the consolidation in the best conditions, that is to say in the position chosen by the surgeon, while minimizing the problems of postoperative pain and edemas, and while shortening the consolidation time as much as possible.
In order to obtain this result, the shape of the anchor is critical.
Another object sought is to provide and maintain a slight compression between the portions of bone to be fused, which makes the consolidation easier. Here again the shape of the anchor is important.
Various technical solutions have already been proposed for achieving such an osteosynthesis, notably at the extremities (foot, hand, wrist, ankle, etc.).
In addition to the conventional or shape-memory staples, it is for example routine to use screws, notably double-pitch screws allowing the placing in compression. In these screws, the pitch of each end is different (distal pitch and proximal or head pitch), for example 0.25 mm per rotation, which makes it possible to obtain a compression of 1 mm in 4 rotations. These known screws may be tubular (mounting on a pin) or not. They are usually self-tapping, that is to say that they do not usually require drilling.
Document FR 2 840 799 describes a self-tapping screw in the distal portion, for which it is nevertheless often necessary to carry out a real pre-drilling notably in the proximal portion which takes away the value of the self-drilling. Moreover, the cutting ridges of the threads are defined at the bore, which weakens the screw, that is to say that in practice the teeth thus defined break very easily.
A second frequent problem with these screws is that their length must be perfectly suited to the bony site so as not to create discomfort, and therefore that they must be screwed immediately in contact with the bone without pushing the latter away at the distal end, while ensuring a good anchorage of the end, which means a cylindrical end making good penetration impossible.
Therefore a screw is known (U.S. Pat. No. 6,306,140) comprising three portions, namely a cylindrical tapped distal portion, a smooth central portion and a self-tapping tapped proximal or head portion of larger diameter.
Such a screw has a particular angular condition only at the head, the distal portion therefore being conventional for its part, that is to say with the ridges of the screwthread being inscribed in a cylinder.
Document EP 0 856 293 A1 describes for its part a screw which on this occasion is self-tapping and self-drilling but which, in order to do this, has bevels at the ends which on the other hand detracts from the grip of the screw or makes it necessary to sink it more deeply in order that the bone is at the level at which the screw is totally cylindrical. Moreover, the proposed cutting ridges are too deep, fragile and therefore breakable at the barrel.
The invention provides a remedy for all these drawbacks in a simple, reliable, effective and rational manner.
To do this, the object of the present invention is to propose a screw that satisfies better than those formerly known the requirements of the practice notably in that it proposes a self-drilling and self-tapping, compressive screw allowing a good penetration and simultaneously ensuring a very good bone anchoring and does so without passing through the bone.
Such a screw is specially adapted to the surgical techniques that bear on the two sides of a fairly thin cortical bone as in the case of a metatarsal osteotomy of the “scarf” type.
In the rest of the text, reference will be made to the following definitions:
For this purpose, the invention therefore notably proposes an osteosynthesis and arthrodesis screw for orthopedic surgery notably of the hand and of the foot, the screw being tubular or not, having along its main axis (AP) three successive portions, namely a distal portion comprising threads (A1), a smooth central portion or central barrel (f) and a proximal portion or head comprising threads (A2), the distal portion having an external diameter that is slightly smaller than that of the proximal portion and having a screw pitch that is slightly greater than that of the proximal portion, making it possible to place in compression the two bony portions to be fused together, the bone-attack zone in the proximal portion (A2a) being conical self-tapping, characterized in that the end of the distal portion is conical,
“Diameter slightly less than” means a difference of between one fifth and one twentieth of the diameter of the proximal portion and advantageously and for example a diameter of the distal portion equal to the order of nine tenths of the diameter of the proximal portion.
“Screw pitch slightly greater than” means a screw pitch of the distal portion greater than a value of between 5% and 20%, and advantageously of the order of 10%, of the screw pitch of the proximal portion.
The two threaded zones, whether they be distal or proximal, for their part make it possible to achieve the bony anchorage, each of the two threads being self-drilling and self-tapping.
The invention is based on the idea of achieving in combination two anchoring zones biting into the bone when screwed in, one for the proximal portion and the other for the distal portion, with particular external profiles, namely slightly conical (thinner on the distal side) out of which the also conical threads are cut, both of them, at the distal end and at the proximal end, comprising several cutting ridges each made by a longitudinal cut in the screwthread.
More precisely, in the embodiment that is more particularly described here, the distal portion, the body of which is of slight conicity (the angle a1 for example being between 4 and 15°), is furnished with a thread of great conicity (the angle b1 for example being between 50 and 80° so that the profile of the crest of the threads of the end of the distal portion becomes cylindrical after the first or the second thread (see
Such an arrangement combined with ridges that are particularly cutting by reason of their formation by removal of material, allows the end to play a role of a punch which immediately catches hold and which makes it possible to place the screw without pre-drilling in a soft bone or with a slight punching in the bone in a harder bone, while having the same anchoring capacity as a screw with a purely cylindrical crest profile.
It is evident moreover that the fact that the ridges are obtained by removal of material and the fact that the profiles are specific and as described hereinabove surprisingly allow not only a good immediate penetration in the two portions of the bone, but also a good compression of the two portions of bone against one another and finally a good hold in the bone itself, and this is despite the conicity of the distal portion of the screw, and without passing through the bone.
The assembly can be anchored via the conventional manner of screws, after stabilization of the osteotomy by any appropriate instrument (tongs or forceps) and with the aid of an appropriate screwdriver, mounted on a pin (tubular screw) or not (solid), or a screw fitting making it possible to be connected to a motor.
Moreover, to take account of the anatomical characteristics, the anchoring zones are advantageously connected to the middle zone that is used for strength (notably shear strength) at the osteosynthesis focal point by more or less long connection zones.
Finally, the material constituting the anchor that is the subject of the invention allows drilling in the bone and therefore has the necessary hardness. Any anchorable material that is sufficiently hard such as stainless steel, titanium, a CrCo (chrome-cobalt) alloy, etc. is advantageously chosen in this instance.
In a particular embodiment of the invention, the anchor is therefore notably made of a titanium alloy such as the alloy known as TA6V (titanium, aluminum, vanadium alloy).
In advantageous embodiments, use is also made of one and/or the other of the following arrangements:
The invention will be better understood on reading the following description of an embodiment given as a nonlimiting example.
The description refers to the attached drawings in which:
a and 2b are views in longitudinal section along the main axis of the screw, respectively of the distal portion and of the proximal portion;
a and 3b are cross sections at the cutting ridges in a reference position (
The distal and proximal attack zones A1a and A2a each comprise several teeth D, for example three teeth each defining a cutting ridge AR. These teeth D are formed by a notch or cut parallel to a main axis AP of the screw in order to create a cutting ridge AR at the intersection of this milling with the outer edge of the thread of the screw P.
a shows more precisely a longitudinal section of the screw in the distal portion.
In this section, a1 is defined as the angle between the main axis AP and a straight line D1 connecting the roots of the threads P, or corresponding to the external surface of the barrel f1 excluding the threads. The angle b1 is also defined as the angle between the main axis AP and the straight line E1 connecting the crests of the threads P.
In the same manner,
Also the angle b2 is defined as the angle between the main axis AP and the straight line E2 connecting the crests of the threads P.
a for its part shows a cross section of the screw in the zone A1a, that is to say at the teeth D. The section is identical in the zone A2a and is therefore not shown. The cross-hatched zone f corresponds to the tubular barrel of the screw. The teeth D are shown to be three in number, and produced by removal of material corresponding to a ½ rectangle (L1-L2). The cutting ridges AR correspond to the intersection of the side L2 with the outside of the thread P. AxR is a radial axis of the screw.
b shows the same section after a slight rotation through an angle C. This angle C corresponds to the angle between the radial axis AxR passing through the cutting ridge AR and the side L2.
In order to obtain proper penetration, the distal end of the barrel, namely f1 at the distal end and f2 at the proximal end (corresponding to the thread bottoms), is slightly conical, both at the distal end A1a and at the proximal end A2a, with an angle a1 at the distal end and a2 at the proximal end.
This conicity of the barrel f is associated with a conicity of the crest of the thread angle b1 at the distal end and b2 at the proximal end that are large enough to allow an immediate engagement of the screw as soon as perforation begins.
Specifically the thread of the screw is cut at the very bottom of the end A1a at the distal end A2a at the proximal end, respectively on this conical trajectory, that is to say that the thread depth increases very rapidly which makes it possible to have a significant thread height as close as possible to the end.
According to the embodiment of the invention that is more particularly described here, on the one hand the sum of the angles a1+b1 at the distal end, a2+b2 at the proximal end, defined between on the one hand the main axis of the screw AP and the external conicity of the barrel f1 at the distal end and f2 at the proximal end, a1 at the distal end, a2 at the proximal end, and, on the other hand, between the main axis of the screw AP and the crest line of the threads P of the screwthread, namely b1 at the distal end, b2 at the proximal end, is greater than 45° and on the other hand the attack portion (the most distal portion) of each thread has a plurality of cutting ridges AR obtained by removal of material.
Moreover, and as has been seen, in advantageous embodiments, the cutting ridges AR are three in number, the sum of the angles (a1+b1 at the distal end and a2+b2 at the proximal end, respectively) is between 50° and 70°, and/or the angle a1 at the distal end is between 4° and 10° and the angle a2 at the proximal end is between 10° and 20°.
In practice, and as a nonlimiting example, for a screw of 2 mm in diameter, the distal diameter of the distal end is 1.8 mm to allow good penetration. The angle a1 is 6°, the angle a2 is 15°, while b1 is fixed at 50° and b2 at 40° to allow immediate anchoring. That is to say a1+b1=56° and a2+b2=55°.
In cross section, the cutting ridges are obtained by the machining of a closed L by the external diameter of the thread P of the screw.
This L is formed by a long side L1 and a short side L2 (
Finally, so as not to weaken the screw, the position of the point of intersection of the straight-line sides L1 and L2 (point L), that is to say the depth of the cut, in no circumstances bites into the main barrel.
In the advantageous embodiment more particularly described, the depth of the cutting ridges AR is less than or equal to the depth of the screwthread.
Finally, in
It will be similarly noted with reference to
In practice, as an example for a screw with a nominal diameter of 2.5 mm, a slight offset of 0.15 mm makes it possible to obtain an angle C of 7°.
In order to improve the clearance of bone chips, a relief of 10° rearward in the direction of screwing in can be made on each tooth D.
Also the external end of the head may be completely conical, for penetrating into the bone, or have a flat head in order to press on the external surface of the bone.
Now, with reference to
The surgeon will first of all bring together the two pieces of bone placing them next to one another in their fusion position.
Then, without initial preparation or pre-tapping, he will screw the screw through the bone portion known as the upper bone portion.
Since the distal portion is conical, penetration takes place until the proximal portion remains in contact with the bone.
The different pitches of the screws then have an effect of bringing together and of compressing the bone portions, which effect is increased at the end of screwing in by the conical aspect of the ends of the two distal and proximal portions in an increased manner.
Astonishingly, the combination of the two conical-effect screw formations, as described above, increases the stability of the assembly and allows an exceptional consolidation.
It goes without saying and it results from the foregoing that the present invention is not limited to the embodiments more particularly described. On the contrary, it covers all the variants thereof.
Number | Date | Country | Kind |
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09 00557 | Feb 2009 | FR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/FR2010/000094 | 2/9/2010 | WO | 00 | 9/6/2011 |
Publishing Document | Publishing Date | Country | Kind |
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WO2010/089481 | 8/12/2010 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
1677269 | Burghart | Jul 1928 | A |
2174578 | Graham | Oct 1939 | A |
2242003 | Lorenzo | May 1941 | A |
2247499 | Hutchison | Jul 1941 | A |
3512447 | Vaughn | May 1970 | A |
3537288 | Ansingh | Nov 1970 | A |
RE28111 | Laverty | Aug 1974 | E |
3929054 | Gutshall | Dec 1975 | A |
4175555 | Herbert | Nov 1979 | A |
4463753 | Gustilo | Aug 1984 | A |
4537185 | Stednitz | Aug 1985 | A |
4621963 | Reinwall | Nov 1986 | A |
4640271 | Lower | Feb 1987 | A |
4653244 | Farrell | Mar 1987 | A |
4778319 | Schule | Oct 1988 | A |
4940467 | Tronzo | Jul 1990 | A |
4950270 | Bowman et al. | Aug 1990 | A |
RE33348 | Lower | Sep 1990 | E |
5019079 | Ross | May 1991 | A |
5052719 | Boehm | Oct 1991 | A |
5415507 | Janusz et al. | May 1995 | A |
5456685 | Huebner | Oct 1995 | A |
5474408 | Dinitz et al. | Dec 1995 | A |
5643269 | Harle | Jul 1997 | A |
5653710 | Harle | Aug 1997 | A |
5746039 | Nystrom | May 1998 | A |
5816012 | Willis | Oct 1998 | A |
5827031 | Swallow | Oct 1998 | A |
5857816 | Assmundson | Jan 1999 | A |
5863167 | Kaneko | Jan 1999 | A |
5868749 | Reed | Feb 1999 | A |
5871486 | Huebner et al. | Feb 1999 | A |
5899906 | Schenk | May 1999 | A |
5968047 | Reed | Oct 1999 | A |
5997541 | Schenk | Dec 1999 | A |
6004321 | Graser | Dec 1999 | A |
6022177 | Hofer | Feb 2000 | A |
6030162 | Huebner | Feb 2000 | A |
6039738 | Sanders et al. | Mar 2000 | A |
6048344 | Schenk | Apr 2000 | A |
6053653 | Tanaka et al. | Apr 2000 | A |
6074149 | Habermehl et al. | Jun 2000 | A |
6264677 | Simon et al. | Jul 2001 | B1 |
6283973 | Hubbard et al. | Sep 2001 | B1 |
6306140 | Siddiqui | Oct 2001 | B1 |
6319254 | Giet et al. | Nov 2001 | B1 |
6341917 | Schubring et al. | Jan 2002 | B1 |
6402757 | Moore, III et al. | Jun 2002 | B1 |
6436100 | Berger | Aug 2002 | B1 |
6440136 | Gambale et al. | Aug 2002 | B1 |
6635059 | Randall et al. | Oct 2003 | B2 |
6672791 | Schubring et al. | Jan 2004 | B2 |
6736819 | Tipirneni | May 2004 | B2 |
6739815 | Takasaki | May 2004 | B2 |
6918727 | Huang | Jul 2005 | B2 |
6955677 | Dahners | Oct 2005 | B2 |
6981974 | Berger | Jan 2006 | B2 |
7037309 | Weil et al. | May 2006 | B2 |
7044953 | Capanni | May 2006 | B2 |
7207994 | Vlahos et al. | Apr 2007 | B2 |
7213999 | Haas | May 2007 | B2 |
7316532 | Matthys-Mark | Jan 2008 | B2 |
7367768 | McGovern et al. | May 2008 | B2 |
7582107 | Trail et al. | Sep 2009 | B2 |
7591823 | Tipirneni | Sep 2009 | B2 |
7708738 | Fourcault | May 2010 | B2 |
7722654 | Taylor et al. | May 2010 | B2 |
7731738 | Jackson et al. | Jun 2010 | B2 |
7794483 | Capanni | Sep 2010 | B2 |
7905909 | Orbay et al. | Mar 2011 | B2 |
8070786 | Huebner et al. | Dec 2011 | B2 |
8157803 | Zirkle, Jr. et al. | Apr 2012 | B1 |
8668725 | Smisson, III et al. | Mar 2014 | B2 |
20020087161 | Randall et al. | Jul 2002 | A1 |
20020169453 | Berger | Nov 2002 | A1 |
20020198527 | Muckter | Dec 2002 | A1 |
20030059270 | O'Berry | Mar 2003 | A1 |
20030078584 | Tipirneni | Apr 2003 | A1 |
20030120277 | Berger | Jun 2003 | A1 |
20040006345 | Vlahos et al. | Jan 2004 | A1 |
20040172030 | Tipirrneni | Sep 2004 | A1 |
20040172031 | Rubecamp et al. | Sep 2004 | A1 |
20040225292 | Sasso et al. | Nov 2004 | A1 |
20050101961 | Huebner et al. | May 2005 | A1 |
20060015105 | Warren et al. | Jan 2006 | A1 |
20060074419 | Taylor et al. | Apr 2006 | A1 |
20060142770 | Capanni | Jun 2006 | A1 |
20060173461 | Kay et al. | Aug 2006 | A1 |
20060217727 | Munro et al. | Sep 2006 | A1 |
20080119855 | Hoegerle et al. | May 2008 | A1 |
20080147128 | Fritzinger | Jun 2008 | A1 |
20080188899 | Bottlang et al. | Aug 2008 | A1 |
20080234752 | Dahners | Sep 2008 | A1 |
20080234763 | Patterson et al. | Sep 2008 | A1 |
20080306555 | Patterson et al. | Dec 2008 | A1 |
20090105768 | Cragg et al. | Apr 2009 | A1 |
20090131990 | Tipirneni et al. | May 2009 | A1 |
20090198289 | Manderson | Aug 2009 | A1 |
20090254129 | Tipirneni et al. | Oct 2009 | A1 |
20100069970 | Lewis et al. | Mar 2010 | A1 |
20100114315 | Manderson | May 2010 | A1 |
20100268285 | Tipirneni et al. | Oct 2010 | A1 |
Number | Date | Country |
---|---|---|
0856293 | May 2003 | EP |
1378205 | Jan 2004 | EP |
2840799 | Dec 2003 | FR |
02056778 | Jul 2002 | WO |
2004069031 | Aug 2004 | WO |
Number | Date | Country | |
---|---|---|---|
20110313473 A1 | Dec 2011 | US |