|Publication number||USRE42626 E1|
|Application number||US 10/629,788|
|Publication date||Aug 16, 2011|
|Filing date||Jun 3, 1998|
|Priority date||Jun 3, 1997|
|Also published as||CA2292748A1, CA2292748C, DE69826999D1, DE69826999T2, DE69838626D1, DE69838626T2, DE69839406D1, DE69839406T2, EP0986339A1, EP0986339B1, EP1415602A2, EP1415602A3, EP1415602B1, EP1415603A2, EP1415603A3, EP1415603B1, US6267765, WO1998055038A1|
|Publication number||10629788, 629788, PCT/1998/1119, PCT/FR/1998/001119, PCT/FR/1998/01119, PCT/FR/98/001119, PCT/FR/98/01119, PCT/FR1998/001119, PCT/FR1998/01119, PCT/FR1998001119, PCT/FR199801119, PCT/FR98/001119, PCT/FR98/01119, PCT/FR98001119, PCT/FR9801119, US RE42626 E1, US RE42626E1, US-E1-RE42626, USRE42626 E1, USRE42626E1|
|Inventors||Jean Taylor, Bernard Villaret|
|Original Assignee||Medicrea Technologies|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (15), Referenced by (5), Classifications (20), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The subject of the present invention is a spinal, particularly dorso-lumbar, osteosynthesis device.
More specifically, the invention is aimed at a device of the type comprising at least two bone-anchoring elements for anchoring into bone structures of the spine, a member for longitudinally connecting the bone-anchoring elements, and shackles for connecting the bone-anchoring elements and the members for connecting the screws; each bone-anchoring element comprises an anchor for anchoring into the bone, a head for grasping by a screwing tool, a threaded shank extending the head for grasping and a tightening element which can be mounted on this shank to lock together the connector, the longitudinal connecting member and the corresponding bone-anchoring element.
Multivertebral, particularly dorso-lumbar, osteosynthesis combines the use of screws or hooks connected together by plates or rods.
The use of plates with appropriate recesses allows the screws a certain amount of travel and allows them to slide along an axis. This is useful when fitting screws which diverge in the sagittal plane.
The use of longitudinal connecting members such as rods for example also allows the bone-anchoring elements, for example screws, to slide along the principal axis of the longitudinal connecting member, and allows screws which diverge in the horizontal plane to be brought onto the same antero-posterior line, and this is by virtue of derotation effects imparted on the rods about an apicocaudal axis, that is to say in the horizontal plane.
However, the bending of the rod that this manoeuvring this must be performed between two vertebral segments which are a sufficient distance apart. Furthermore, one or more successive bending operations are performed only in the same frontal plane. This then results in a deformation transposed into another plane, orthogonal to the first.
The adjusting of the pedicle-screws/rod pair may lead to very high stresses in the system before it is definitely locked.
Special-purpose instruments have therefore been conceived.
Pedicle screws in which the threaded shank is extended rearwards have also been developed, so that the descent of the rod as far as the vertebral implantation base of the screw can be guided, segment by segment.
The other benefit of this type of extended pedicle implant is that it allows equal use either of a plate or of a rod.
There are deformations whose radius of curvature may be short, in one or two segments, but, nonetheless, combined in the three planes, sagittal, horizontal and frontal. Simply bending a rod in a single plane, bringing this rod gradually alongside or performing an overall derotation movement, is then no longer suitable.
This is because the reduction by rotation of the rod in the event of bending in two planes is prohibited by the laws of mechanics.
Reduction of a deformation with a large radius, under such conditions, is in three planes, but is not in any way sequential, and can even less be said to be selective.
These short deformations, which can be reduced partially, have to be considered segment by segment and especially plane by plane before any reduction manoeuvre, particularly partial, can be envisaged.
One vertebra which is off-set in isolation in the frontal sagittal and horizontal planes has to be brought into a condition such that it can undergo reduction in just one plane if necessary, or even with a view to be secured as it is to the adjacent segment under no stress other than the stress induced by neutralization.
To meet these requirements, pedicle screws equipped with a “ball joint” system have been designed and developed.
Thus, the head of a screw may be capped by a U-shaped element thus dubbed a “tulip” which acquires mobility about the principal axis of the screw.
The travel obtained makes it possible, within certain limits, to get around the consequences of an angular offset in the horizontal and/or frontal plane of the pedicle alignment.
This being the case, the bending of the rod is no longer a ruse for roughly aligning a poorly frontally aligned setup.
The surgeon is thus freed of this enormous burden and can implant the pedicle screws along the axis imposed by the topography of the pathological vertebra.
Regional sagittal vertebral statics are observed by virtue of a bending in one plane, aimed at restoring sagittal equilibrium.
Various mechanical solutions are proposed, particularly by successively fitting together elements which culminate in the securing of the screw/ball/rod triplet.
Geometrically complex recesses and the fitting-together of a series of elements allow the advantages of the above described screw/ball-jointed tulip element to be reproduced.
In spite of the considerable progress that this alternative represents, it is appropriate that a critical analysis be made of it, and this analysis can be summarized in three points:
Furthermore, reduction of an anterolisthesis requires the use of screws with a U, the arms of which are extended backwards, at the expense of requiring far more space. Finally, in order not to stress the tightening elements during traction manoeuvres, use of a special-purpose reduction instrument is recommended but entails stressing the pedicle in tension; all of which cause preliminary weakening.
The mechanically reliable nature of the immobilization assumes a perfect fit, although such fit is uncertain under operating conditions (firstly the constraints imposed by the process, the interposition of tissue, poor visual inspection, etc.) where the implant is embedded.
The absence of rotational locking between the anchoring part and the multi-axis ball also makes dismantling difficult and sometimes impossible.
According to the invention, the threaded shank has a ball end for articulation in a housing of a spherical cup of the head for grasping, allowing the shank to be orientated in many directions, and allowing the connecting shackle to be positioned to suit the configuration of the vertebral segment receiving the bone-anchoring elements, and the ball and the cup have respective centres of rotation which are separated by a distance, giving the device, when tightened using the tightening element, by bearing against the upper part of the head for grasping, a function of returning the bone-anchoring element by transverse force, the connector shackle for this purpose having a spherical bearing surface articulated to a portion of the spherical surface of the cup of the head of the bone-anchoring element.
Depending on the physical characteristics of the connecting shackle, either the surface contact immobilizes the bone-anchoring element and allows the orientation of the bone-anchoring element to be maintained, or the connecting shackle bears against the upper part of the head for grasping, giving the device, upon tightening of the element, a transverse return function.
Thus, among other advantages, the device according to the invention allows the implant to be orientated in many directions using a system which requires a very small amount of space, and allows the bone-anchoring elements to be used either with rods or with plates.
According to one feature of the invention, the threaded shank and the connecting shackle are equipped with means for immobilizing the shank and its ball in terms of rotation once the threaded shank has been introduced into the corresponding through-hole through the shackle.
According to another feature of the invention, the said means comprise at least one rotation-stopping geometry formed between the ball and the contiguous end of the threaded shank, and a second rotation-stopping geometry formed on the interior edge of the hole in the shackle, this second geometry being designed to press against the first geometry once the connecting shackle has been slid along the threaded shank.
According to another feature of the invention, the device also comprises at least one bone-anchoring element comprising an anchoring shape, a head with a transverse collar and a shape for grasping, for screwing and a threaded shank extending the head, the assembly being all of one piece.
Other particular features and advantages of the invention will emerge from the description which will follow, which is given with reference to the appended drawings which illustrate two embodiments thereof by way of non-limiting examples.
The spinal osteosynthesis device illustrated in
The head 5 for grasping has a shape which can cooperate with a screwing tool 6, for example a hexagonal outline as depicted, designed to cooperate with a female hexagonal cavity 9 of the tool 6.
The shank 7 has a ball end 11 for articulation in a hemispherical housing 12 of the head 5, in which housing this ball 11 can be held by various assembly techniques, particularly by crimping, welding, etc. The approximately hemispherical housing 12 allows the ball 11 to turn and be mobile in all planes, thus allowing the threaded shank 7 to be orientated in many directions.
The latter and the connecting shackle 3 are fitted with means for immobilizing the shank 7 and its ball 11 in terms of rotation while the nut 8 is being tightened or slackened once the shank 7 has been introduced into a corresponding through-hole 10 through the connecting shackle 3. In the embodiment depicted, these means comprise at least one male rotation-stopping geometry 13 formed on a collar 14 arranged between the ball 11 and the contiguous end of the shank 7, and at least one second, female, rotation-stopping geometry illustrated as a flat 15 formed on the interior edge of the hole 10 in the shackle 3. This second flat 15 is designed to press against the first flat 13 once the shackle 3 has been slid along the threaded shank 7.
As a preference, the collar 14 thus has two diametrically opposed rotation-stopping geometries 13, just one of these geometries 13 being visible in the drawings. The collar 14 thus equipped with the two geometries 13 can fit into the corresponding connecting shackle 3 if the fixture is being used with a vertebral rod 2 or into a plate 16 having similar rotation-stopping geometries (edges of the holes 38, 41, 43 in
Beyond the collar 14, the shank 7 has a first cylindrical threaded portion 17, a narrowed portion 18 constituting a break initiator, a second cylindrical threaded portion 19 extended by a plain end part 21 constituting a male shape with an appropriate profile, for example a half-moon profile with a rotation-stopping geometry, hereinafter known as the flat 22 (
The narrowed portion 18 preferably has a rotation-stopping geometry identical to the fiat 22. This arrangement allows the ball 11 to be immobilized in terms of rotation during an operation of withdrawing the implant, using the tool 6.
Fitting the male shape 21 with its rotation-stopping geometry which may be a flat 22, into the mating female shape 20 with the flats 22 and 23 pressing one against the other, allows the threaded shank 7 to be immobilized in terms of rotation while the nut 8 is being screwed onto the threaded portions 19 and 17 of the shank 7.
Furthermore, once fitting is complete it is at the narrowed portion 18 that the shank 7 is broken into two parts so that the threaded portion 19 can be removed. Thus, only the threaded portion 17 forms an integral part of the permanent fixture, the second portion 19 having the function only of guiding the descent of the nut 8 as far as the shackle 3 (
The connecting shackle 3 consists of two branches 26, 27 bent one over onto the other and separated by a longitudinal slit 28, the hole 10 for the passage of the shank 7 thus being formed in the branches 26, 27 one on each side of the slit 28. The two branches 26, 27 are connected by one or two rounded connecting pieces 29 which delimit one or two cylindrical housings 31 into which one or two cylindrical rods 2 can be introduced (
Specifically, they show that the sphere or ball 11 of the bone-anchoring element 1 and the spherical cup 57 have respective centres of rotation R1 and R2 which are distinct and separated by a distance S. The surface of the cup 57 of the head 5 is hemispherical and interrupted in its polar region to receive the ball 11, and the associated spherical surface 55 of the shackle 3, with the same radius of curvature as the surface of the hemispherical cup 57, completely covers the latter.
The pressing on the upper part of the head 5 for grasping gives the connecting shackle 3/bone-anchoring element 1 system a function of returning the latter to the axis XX of the tightening nut 8 and of the threaded shank 7 during the tightening manoeuvre using the element 8. Specifically, during this manoeuvre, the element 8 (nut for example), the skirt 8a of which rests against the conical wall 56 of the recess in the nut 8, produces a tensile force F (
In the embodiment illustrated in
This possibility of operating using different connectors capable of varying the realignment allows corrections to be planned without having to resort to additional tools.
The ability to orientate the bone-anchoring element 1 with respect to the axis XX, with return (
Once the threaded shank 4 has already been applied to the structure of a vertebra, for example a lumbar vertebra, the shank 7 is orientated towards the corresponding connector 3 already mounted on a vertebral rod 2. Once this has been performed, the tool 6 Allows the shank 7 to be immobilized in terms of rotation using the sleeve 24 while the outer socket 25 allows the tightening element 8 to be screwed as far as its position which immobilizes the assembly, the rotation stopping geometry or geometries 13 of the collar 14 pressing against the corresponding rotation-stopping geometry or geometries 15 of the shackle 3.
In the lombosacral set-up illustrated in
The bone-anchoring element 31 comprises a threaded anchoring rod 32, a head 33 which has no ball thus making the screw a one-piece screw. The head 33 consists of a transverse collar 34 and a shape 35 for grasping for screwing with an appropriate tool, for example a hexagonal shape. A threaded shank 7 similar to the one of the bone-anchoring element 1 extends the head 33, the assembly being of one piece. Facing the sacrum S the plate 16 has an end part with a circular hole for the passage of a single bone-anchoring element 31, and then, in the region of L5, has a second elongate portion 39 in which there is formed an oblong hole 41 which allows the position of a bone-anchoring element 31 to be adjusted correspondingly between two positions; finally, the plate 16 has a third part 42 of elongate shape in which there is made an oblong passage 43 delimiting three possible positions for the bone-anchoring element 1 depending on the adjustment needed, by virtue of three cut-outs formed on the edges of the passage 43.
The plate 16 which is intended for three spinal segments or stages, S, L5, L4, for example, may be replaced with a plate suited to a different number of stages. For example, in the three-stage set-up of
The multi-axis screw 1 is left free to move at the beginning of the fitting of the tightening element 8 along the threaded shank 7. Next, the sleeve 24 with its half-moon shape 23 immobilizes the ball 11. Using an appropriate movement, the bone-anchoring element 1 is thus positioned in one of the three orifices of the oblong hole 43. The prebending of the plate 16 allows the vertebra L4 to reposition itself in lordosis with respect to the underlying vertebra, without compromising the locking of the plate 16/bone-anchoring element 1 pair, because of the tolerance afforded by the ball 11.
It is possible to use a plate for just two boney structures of the lumbar spine. Prebending this plate allows the vertebra to be tilted in the posterior direction and therefore allows physiological discal asymmetry to be recreated, particularly in the case of the surgical treatment of the so-called “flat back” condition.
Aside from the technical advantages already mentioned, the spinal osteosynthesis device according to the invention exhibits the following advantages:
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US2190585 *||Aug 22, 1936||Feb 13, 1940||Armstrong Bros Tool Co||C clamp|
|US4946458 *||Feb 28, 1989||Aug 7, 1990||Harms Juergen||Pedicle screw|
|US5304179 *||Jun 17, 1993||Apr 19, 1994||Amei Technologies Inc.||System and method for installing a spinal fixation system at variable angles|
|US5591166 *||Mar 27, 1995||Jan 7, 1997||Smith & Nephew Richards, Inc.||Multi angle bone bolt|
|US5628740 *||Jun 30, 1995||May 13, 1997||Mullane; Thomas S.||Articulating toggle bolt bone screw|
|US5735851 *||Oct 9, 1996||Apr 7, 1998||Third Millennium Engineering, Llc||Modular polyaxial locking pedicle screw|
|US5800435 *||May 1, 1997||Sep 1, 1998||Techsys, Llc||Modular spinal plate for use with modular polyaxial locking pedicle screws|
|US5851082 *||May 31, 1996||Dec 22, 1998||Lemforder Metallwaren Ag||Axial ball-and-socket joint for linkages in motor vehicles|
|US5891145 *||Jul 14, 1997||Apr 6, 1999||Sdgi Holdings, Inc.||Multi-axial screw|
|US5938663 *||Mar 5, 1996||Aug 17, 1999||Stryker France, S.A.||Spinal instruments, particularly for a rod|
|US5984924 *||Oct 7, 1998||Nov 16, 1999||Isola Implants, Inc.||Bone alignment system having variable orientation bone anchors|
|US6022350 *||May 12, 1997||Feb 8, 2000||Stryker France S.A.||Bone fixing device, in particular for fixing to the sacrum during osteosynthesis of the backbone|
|US6123706 *||Dec 17, 1998||Sep 26, 2000||Lange; Robert||Apparatus for stabilizing certain vertebrae of the spine|
|US7163538 *||Feb 7, 2003||Jan 16, 2007||Cross Medical Products, Inc.||Posterior rod system|
|DE19512709A1 *||Apr 8, 1995||Oct 10, 1996||Rehder Guenther||Holding device for prosthesis|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US8444681||Apr 13, 2012||May 21, 2013||Roger P. Jackson||Polyaxial bone anchor with pop-on shank, friction fit retainer and winged insert|
|US8613760||Dec 14, 2011||Dec 24, 2013||Roger P. Jackson||Dynamic stabilization connecting member with slitted core and outer sleeve|
|US8911479||Jan 10, 2013||Dec 16, 2014||Roger P. Jackson||Multi-start closures for open implants|
|US8979904||Sep 7, 2012||Mar 17, 2015||Roger P Jackson||Connecting member with tensioned cord, low profile rigid sleeve and spacer with torsion control|
|US20120123478 *||May 17, 2012||Spartek Medical, Inc.||Low profile spinal prosthesis incorporating a bone anchor having a deflectable post and a compound spinal rod|
|International Classification||A61F5/00, A61B17/70, A61B17/80, A61B17/58|
|Cooperative Classification||A61B17/8061, A61B17/7052, A61B17/7037, A61B17/701, A61B17/7047, A61B17/7014, A61B17/7007, A61B17/7041|
|European Classification||A61B17/70B5B, A61B17/70B1C4, A61B17/70B6, A61B17/70D4, A61B17/70B1L, A61B17/70B1E, A61B17/70C|