WO2018210946A1 - Polyaxial bone screw for an osteosynthesis device, and osteosynthesis device comprising same - Google Patents

Polyaxial bone screw for an osteosynthesis device, and osteosynthesis device comprising same Download PDF

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Publication number
WO2018210946A1
WO2018210946A1 PCT/EP2018/062768 EP2018062768W WO2018210946A1 WO 2018210946 A1 WO2018210946 A1 WO 2018210946A1 EP 2018062768 W EP2018062768 W EP 2018062768W WO 2018210946 A1 WO2018210946 A1 WO 2018210946A1
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WO
WIPO (PCT)
Prior art keywords
screw
head
rod
tulip
space
Prior art date
Application number
PCT/EP2018/062768
Other languages
French (fr)
Inventor
Clément CHAROSKY
Christopher J. DEWALD
Poul Martin GEHRCHEN
Pierre Roussouly
Clément SILVESTRE
Philippe Vincent-Prestigiacomo
Original Assignee
Kisco International
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kisco International filed Critical Kisco International
Publication of WO2018210946A1 publication Critical patent/WO2018210946A1/en

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
    • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
    • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
    • A61B17/70—Spinal positioners or stabilisers ; Bone stabilisers comprising fluid filler in an implant
    • A61B17/7001—Screws or hooks combined with longitudinal elements which do not contact vertebrae
    • A61B17/7035—Screws or hooks, wherein a rod-clamping part and a bone-anchoring part can pivot relative to each other
    • A61B17/7037—Screws or hooks, wherein a rod-clamping part and a bone-anchoring part can pivot relative to each other wherein pivoting is blocked when the rod is clamped

Definitions

  • the present invention relates to orthopedic surgery, and more specifically the bone screws of osteosynthesis devices, in particular spinal devices, which are used to connect bones, such as vertebrae, or portions of bone, to a rod intended to correct and stabilize their relative positions.
  • the spinal osteosynthesis device screws intended to connect the vertebrae to be treated with a more or less locally curved longitudinal rod extending over a portion of the spine may, in known manner, be essentially of two types: monoaxial and polyaxial.
  • Monoaxial screws are, of construction, completely rigid. Their rectilinear lower part threaded externally, realizing the anchoring in the vertebra, forms a longitudinal axis for the screw. Their upper part, which extends the lower part, can consist of:
  • the polyaxial screws allow an adaptation of these relative orientations.
  • their upper part which receives the rod itself or, sometimes, a connector receiving the rod is not fixed rigidly to the threaded lower part but is hinged to it thanks, for example, to a substantially spherical configuration the upper end of the lower part of the screw which, for example, fits into a cavity also spherical formed in said upper part of the screw.
  • the orientations of the upper part of the screw in the sagittal and transverse planes are fixed and maintained, at the end of the assembly of the osteosynthesis device, by tightening the plugs or nuts.
  • Various designs of such polyaxial screws exist, in which configurations using a greater or smaller number of parts may be used to provide polyaxiality.
  • the existing polyaxial screws comprising a tulip for receiving the longitudinal rod do not however allow the surgeon to precisely adjust the orientation of the longitudinal axis of the screw relative to the longitudinal rod in the sagittal plane of the patient, during the setting. in place of the osteosynthesis device.
  • the precise relative positions of the vertebrae according to the local bending of the longitudinal rod are therefore not very easy to adjust during assembly of the device.
  • the object of the invention is to propose a new type of polyaxial screw comprising a tulip for receiving the longitudinal rod, with which it would be possible to easily fix the relative positioning of the bones (or portions of bone if the device is used, for example, during the reduction of long bone fractures) concerned, in particular vertebrae in the case of spinal surgery.
  • the subject of the invention is a polyaxial bone screw for an osteosynthesis device intended to connect a longitudinal rod and a bone of a patient, comprising a threaded rectilinear lower part intended to be anchored in the bone, a head having at least locally a spherical shape having a radius of curvature r and whose upper surface is intended to come into contact with said longitudinal rod, a tulip threaded internally in its upper part, having a space intended to serve as a receptacle for said rod longitudinal of the osteosynthesis device, and a threaded plug for closing said tulip after the insertion of the rod and pressing the rod against the head by clamping, the lower part of said tulip having an interior space whose wall has a surface allowing rotation of the head in said space, characterized in that said wall surface allowing rotation of the head stops before reaching the lower edge of the tulip, in that is formed permanently, in the lower part of the space, a space between said wall and at least a portion
  • the head of the screw may have a truncated upper surface perpendicular to the longitudinal axis of the straight lower threaded portion of the screw, said truncated upper surface being intended to come into contact with the longitudinal rod of the osteosynthesis device.
  • the external radius of curvature of the head of the screw may have, on a portion of the head, a value equal to r
  • the upper zone of the wall of the inner space of the tulip may comprise two diametrically opposite recesses, which have to function to guide the head of the screw when the cap is being clamped and press the rod against the head of the screw, the shape of these recesses being such that, in line with the space for the insertion of the rod , the inner wall of the tulip has a radius of curvature substantially equal to r.
  • the screw may be intended for a spinal osteosynthesis device.
  • the invention also relates to an osteosynthesis device comprising a longitudinal shaft and bone screws for connecting it to at least one bone of a patient, characterized in that at least one of said bone screws is of the above type.
  • the invention consists in designing a polyaxial screw comprising a tulip for receiving the longitudinal rod of the osteosynthesis device, which, when tightening the longitudinal rod in the tulip by means of the stopper, goes in the case of use in spinal surgery, impose an orientation of the longitudinal axis of the screw perpendicular to the stem in the sagittal plane of the patient, while in the transverse plane of the patient, the screw / rod angulation takes a free value and fixed by tightening.
  • the vertebrae are assuredly and automatically positioned optimally in the sagittal plane according to the local bending of the rod at their level.
  • the longitudinal axis of the screw is certainly perpendicular to the longitudinal axis of the rod, once it held in the tulip by tightening the cap. Seen in this sagittal plane, the screw seems to be of the monoaxial type. In contrast, in the transverse plane, the orientation of the screw relative to the rod remains free, as for a conventional polyaxial screw.
  • the upper end of the threaded lower part of the screw, on which the tulip articulates has a spherical general shape but, at least in certain variants of the invention, is truncated. so as to have an upper surface perpendicular to the longitudinal axis of the screw, and on which the rod will be pressed by tightening the plug.
  • the internal space of the tulip in which said upper end of the threaded lower portion of the screw is inserted has a shape which imposes, when tightening the cap, that the lower part screw thread takes an angulation perpendicular to the longitudinal axis of the rod in the area concerned.
  • FIG. 1 which shows, in longitudinal section in the sagittal plane, an example of a polyaxial screw of the prior art during the assembly of a spinal osteosynthesis device and the longitudinal rod of this device, before the tightening of the plug which press the rod against the upper end of the threaded portion of the screw;
  • FIG. 3 which shows schematically a very imperfect alignment of the vertebrae of the patient that may be obtained with the use of the screw of Figures 1 and 2 in combination with the longitudinal rod of the spinal osteosynthesis device;
  • FIGS. 1 and 2 show in longitudinal section in the sagittal plane of the patient an example of a polyaxial screw 1 according to the prior art and the longitudinal rod 2 that the screw 1 must rigidly connect to a vertebra 3 (in the preferred case which is the subject of the description, but it must be clear that the screws of the prior art and the screws according to the invention which will be described could be used to connect the rod 2 to any other type of bone - or of bone portion - on which the invention could be used).
  • the screw 1 has a lower portion 4 rectilinear externally threaded, defining the longitudinal axis of the screw, and intended to anchor in the vertebra 3.
  • Its upper end 5 (which will be called “head” in the continuation of text), which emerges from the vertebra 3, has a generally spherical shape and comprises, as is conventional, an imprint 6 of polygonal section (in the example shown), in which the surgeon can insert the end of a screwdriver to drive the screw 1 into the vertebra 3.
  • the screw 1 also comprises a "tulip" 7 serving as a receptacle for the longitudinal rod 2.
  • This tulip 7 comprises an upper part composed of two walls facing each other and defining a space 8 intended to be traversed by the rod 2. Only the a 9 of these walls is visible in the figures. These walls 9 carry on their surface facing the space 8 a threading 10 allowing the insertion and screwing of a cylindrical plug 1 1 whose outer wall has a thread 12 corresponding to that of the walls of the tulip 7 and which comprises a polygonal internal space 13 (in the example shown) for the insertion of a screwdriver which makes it possible to screw the plug 1 1 into the tulip 7.
  • the plug 1 1 makes it possible to close the tulip 7 after the insertion of the rod 2 and press the rod 2 against the head 5 at the end of the screwing.
  • the inner lower part of the tulip 7 also comprises a cavity 14 whose wall is of spherical shape to the lower edge 15 of the tulip 7, and in which is housed the head 5 of the lower part 4 of the screw 1.
  • the tulip 7 and the head 5 are hinged to one another in the manner of a ball joint.
  • Figure 1 shows the screw 1 and the rod 2 with the rod 2 and the cap 1 1 inserted in the tulip 7 but not yet blocked.
  • the cap 1 1 When the cap 1 1 is tightened by the surgeon, it presses the rod 2 against the head 5 and leads to the situation shown in Figure 2.
  • the vertical pressure exerted by the rod 2 permanently maintains the rectilinear part 4 and the tulip 7 of the screw 1 (and, consequently, the rod 2 which passes through the tulip 7 ) in relative orientations that can be any both in the sagittal plane and in the transverse plane, since the lower edge of the cavity 14 of the tulip 7, which opens itself to the lower edge 15 of the tulip 7, is in contact with the head 5.
  • the surgeon is not able to easily control these relative orientations. There is thus a strong risk of leading to an unsatisfactory situation such as that shown diagrammatically in FIG.
  • Figures 4 to 6 show a first example of implementation of the present invention, at three stages of its implementation.
  • the screw 1 with its threaded straight bottom part 4 and its head 5 which, in the example shown, is of hemispherical shape: the head 5 is, here, truncated substantially at its equator (in the example shown), and in any case in a plane perpendicular to the longitudinal axis of the screw 1, with its imprint 6, the tulip 7 (with, however, a significant difference in the configuration of the tulip 7 compared to that of Figures 1 and 2 which will be discussed later), the cap 1 1, and the longitudinal rod 2 of the device osteosynthesis.
  • the inner space 16 of the tulip 5 has its wall which has in its lower part, a surface 17 of spherical shape which, again, allows a rotation of the head 5 inside this space 16. But this spherical surface 17 stops before reaching the lower edge 15 of the tulip 7 so as, according to the invention, at all times, in the lowest part of the space 15, a space 18 between said wall and at least a part of the head 5 of the screw 1, regardless of the tightening state of the plug 1 1 and the angular position of the screw 1 relative to the rod 2.
  • FIG. 4 shows, in the sagittal plane, this example of a device according to the invention in a state comparable to that of the device according to the prior art in the state represented in FIG. 1, with the longitudinal rod 2 inserted into the tulip 7 and the cap 1 1 not yet tightened.
  • the tightening of the plug 5 has already begun, and the rod 2, at this moment, is in contact on the one hand with the lower surface of the plug 1 1, and on the other hand with a portion of the flat upper surface of the head 5.
  • Figure 5 shows the assembly at a later stage of the clamping of the cap 1 1. Due to the constant presence, according to the invention, of a space 18 between the wall of the internal space 16 of the tulip 7 and the head 5 of the screw 1, the pressure exerted by the rod 2 on the head 5 tends, without encountering resistance (contrary to what happens in the prior art of Figures 1 and 2), to reorient the threaded rod 4 of the screw 1 in the sagittal plane, to finally bring it after the complete tightening of the plug 1 1, in the state shown in Figure 6.
  • the rod 2 is then in contact with the head 5 along a line that runs through the entire upper surface of the head 5, so that there is automatically a perpendicularity between the longitudinal rod 2 and the longitudinal axis of the screw 1 in the sagittal plane.
  • the respective orientations of the rod 2 and the screw 1 remain free, so that in this transverse plane, the polyaxial nature of the screw 1 is retained.
  • FIGS. 8 to 13 show a variant of the invention in a configuration that achieves the final perpendicularity of the screw and the shaft in the sagittal plane of the patient and the polyaxiality in the transverse plane of the patient by means other than those of the previous variant.
  • the head 5 is, in the example shown, truncated perpendicularly to the axis of the screw 1 above its equator, and thus provides a contact surface with the rod 2 a little smaller than in the variant shown in FIGS. Figures 4 to 6, but which is still sufficient for the device can be oriented and properly blocked when tightening the cap 1 1.
  • a truncation of the head 5 perpendicular to the longitudinal axis of the screw 1 would not here, theoretically, not necessary, unlike the case of the previous variant.
  • the head 5 could here, in view of the principles on which the invention is based, be perfectly spherical in its upper part.
  • the interior space 16 of the tulip 7 has a greater height, because the head 5 is more voluminous and also that, as will be seen, the conformation of this space 16 is more complex than in the case of the figures 4 to 6.
  • Its spherical surface 17 continues with a frustoconical portion 19, dimensioned so as not to hinder the rotation of the head 5 during the clamping of the plug 1 1, and which therefore participates in the delimitation of the space 18 according to the invention.
  • the head 5 of the screw 1 has a shape that can, taken as a whole, not correspond to a sphere or a sphere portion.
  • the outer radius of curvature of the head 5 is thus, in the example shown, variable according to the height of the head 5.
  • the screw 1 Immediately under the head 5, the screw 1 has a portion 20 of narrowed diameter, which gives it the possibility to move undoubtedly in the lower part 18 of the interior space 16 of the tulip 5 without interfering with the wall of the space 16. The positioning of the screw 1 when tightening the cap 1 1 is not embarrassed.
  • FIGS 12 and 13 showing the tulip 7 of this second variant, together with Figure 1 1 representing the screw 1, to understand how the setting in position of the screw 1 during tightening.
  • the lower portion 18 of the inner space 16 of the tulip 7 is shaped in a manner comparable to that used in the first variant of the invention described above. In this way, in conjunction with the dimensioning of the screw 1 in the corresponding region, the polyaxiality of the screw 1 in the transverse plane is ensured.
  • the upper zone of the wall of the inner space 16 of the tulip 7 does not here have a uniformly spherical shape and corresponds substantially to the radius of curvature of the head 5 of the screw 1, as is the case in the variant of Figures 4 to 6.
  • this wall has two recesses 21, 22 diametrically opposed. These recesses 21, 22 serve to guide the head 5 of the screw 1 when the plug 1 1 is being clamped and presses the rod 2 against the head 5 of the screw 1.
  • these recesses 21, 22 is such that, in line with the space 8 for the insertion of the rod 2, which separates the two walls 9 of the tulip 5 internally threaded and which define this space 8, the inner wall of the tulip 5 has a radius of curvature substantially equal to the value "r" seen previously about the local radius of curvature of the head 5 of the screw 1.
  • the screw 1 and the tulip 5 can freely rotate relative to each other in the transverse plane of the patient, because of the permanent presence, in the lower part of the interior space 16 of the tulip 7, a space 18 between said wall and at least a portion of the head 5 of the screw 1, regardless of the clamping state of the cap 1 1 and the angular position of the screw 1 relative to on the other hand, when tightening the cap 1 1, the screw 1 guided by the recesses 21, 22 of the tulip 7, is naturally placed in the sagittal plane of the patient, perpendicular to the axis of the rod 2 at its connection to the tulip 5, as seen in Figures 8 to 10.
  • screws 1 according to the invention shown in the figures are not limiting, the essential being that the relative shapes of the head 5 of the screw 1 and the wall 17 defining the interior space 16 of the tulip 7 lead the screw 1 to be placed spontaneously in a position perpendicular to the rod 2 in the sagittal plane of the patient during the tightening of the cap 1 1, under the effect of the pressure exerted by the rod 2 on the head 5 of the screw 1, and that this position is maintained after tightening during use of the osteosynthesis device.

Abstract

Polyaxial bone screw (1) for an osteosynthesis device intended to connect a longitudinal rod (2) and a bone (3) of a patient, having a threaded rectilinear lower part (4), a head (5) having at least locally a spherical shape with a radius of curvature (r), and of which the upper surface is intended to come into contact with said longitudinal rod (2), a tulip (7) threaded internally in its upper part, having a space (8) intended to receive the rod (2), and a threaded plug (11) closing said tulip (7) after insertion of the rod (2) and clamping the rod (2) against the head (5), the lower part of said tulip (7) having an internal space (16) whose wall has a surface (17) permitting a rotation of the head (5) in said space (16). Osteosynthesis device having at least one such screw (1) and a rod (2).

Description

Vis osseuse polyaxiale pour dispositif d'ostéosynthèse, et dispositif  Polyaxial bone screw for osteosynthesis device, and device
d'ostéosynthèse la comprenant  of osteosynthesis including
La présente invention concerne la chirurgie orthopédique, et plus précisément les vis osseuses de dispositifs d'ostéosynthèse, notamment rachidienne, qui sont utilisées pour relier des os, tels que des vertèbres, ou des portions d'os, à une tige destinée à corriger et stabiliser leurs positions relatives. The present invention relates to orthopedic surgery, and more specifically the bone screws of osteosynthesis devices, in particular spinal devices, which are used to connect bones, such as vertebrae, or portions of bone, to a rod intended to correct and stabilize their relative positions.
Les vis de dispositifs d'ostéosynthèse rachidienne destinées à connecter aux vertèbres à traiter une tige longitudinale plus ou moins cintrée localement s'étendant sur une partie du rachis, peuvent, de façon connue, être essentiellement de deux types : monoaxial et polyaxial.  The spinal osteosynthesis device screws intended to connect the vertebrae to be treated with a more or less locally curved longitudinal rod extending over a portion of the spine may, in known manner, be essentially of two types: monoaxial and polyaxial.
Les vis monoaxiales sont, de construction, entièrement rigides. Leur partie inférieure rectiligne filetée extérieurement, réalisant l'ancrage dans la vertèbre, forme un axe longitudinal pour la vis. Leur partie supérieure, qui prolonge la partie inférieure, peut consister :  Monoaxial screws are, of construction, completely rigid. Their rectilinear lower part threaded externally, realizing the anchoring in the vertebra, forms a longitudinal axis for the screw. Their upper part, which extends the lower part, can consist of:
- soit en un réceptacle, souvent appelé « tulipe » et comportant deux parois opposées en arcs de cercle, filetées intérieurement, dans lequel on insère la tige longitudinale, en l'y bloquant à l'aide d'un bouchon dont la paroi externe comporte un filetage correspondant à celui des parois internes du réceptacle ; - soit en une tige filetée extérieurement, alignée sur l'axe longitudinal de la vis, et sur laquelle on insère, puis bloque à l'aide d'un écrou, un connecteur destiné lui-même à recevoir la tige longitudinale ; ce type de vis est utilisé lorsqu'on désire que l'axe longitudinal de la vis soit décalé latéralement par rapport à l'axe de la tige longitudinale.  - Or in a receptacle, often called "tulip" and having two opposite walls in arcs of circle, threaded internally, in which the longitudinal rod is inserted, by blocking it with a plug whose outer wall comprises a thread corresponding to that of the inner walls of the receptacle; - Or an externally threaded rod, aligned on the longitudinal axis of the screw, and on which is inserted, then locks with a nut, a connector for itself to receive the longitudinal rod; this type of screw is used when it is desired that the longitudinal axis of the screw is offset laterally with respect to the axis of the longitudinal rod.
Avec ces vis monoaxiales, il n'est pas possible de régler les orientations relatives de l'axe longitudinal de la vis et de la tige longitudinale dans le plan sagittal et dans le plan transversal du patient. Généralement, ces orientations sont perpendiculaires l'une à l'autre.  With these monoaxial screws, it is not possible to adjust the relative orientations of the longitudinal axis of the screw and the longitudinal rod in the sagittal plane and in the transverse plane of the patient. Generally, these orientations are perpendicular to each other.
Les vis polyaxiales permettent une adaptation de ces orientations relatives. A cet effet, leur partie supérieure qui reçoit la tige elle-même ou, parfois, un connecteur recevant la tige, n'est pas fixée rigidement à la partie inférieure filetée mais est articulée sur elle grâce, par exemple, à une configuration sensiblement sphérique de l'extrémité supérieure de la partie inférieure de la vis qui, par exemple, s'insère dans une cavité également sphérique ménagée dans ladite partie supérieure de la vis. Les orientations de la partie supérieure de la vis dans les plans sagittal et transversal sont fixées et maintenues, à la fin du montage du dispositif d'ostéosynthèse, par un serrage des bouchons ou écrous. Diverses conceptions de telles vis polyaxiales existent, dans lesquelles on peut utiliser des configurations faisant appel à un nombre plus ou moins grand de pièces pour assurer la polyaxialité. The polyaxial screws allow an adaptation of these relative orientations. For this purpose, their upper part which receives the rod itself or, sometimes, a connector receiving the rod, is not fixed rigidly to the threaded lower part but is hinged to it thanks, for example, to a substantially spherical configuration the upper end of the lower part of the screw which, for example, fits into a cavity also spherical formed in said upper part of the screw. The orientations of the upper part of the screw in the sagittal and transverse planes are fixed and maintained, at the end of the assembly of the osteosynthesis device, by tightening the plugs or nuts. Various designs of such polyaxial screws exist, in which configurations using a greater or smaller number of parts may be used to provide polyaxiality.
Les vis polyaxiales existantes comportant une tulipe pour la réception de la tige longitudinale ne permettent cependant pas au chirurgien de régler précisément l'orientation de l'axe longitudinal de la vis par rapport à la tige longitudinale dans le plan sagittal du patient, pendant la mise en place du dispositif d'ostéosynthèse. Les positions relatives précises des vertèbres en fonction du cintrage local de la tige longitudinale ne sont donc pas très faciles à régler lors du montage du dispositif.  The existing polyaxial screws comprising a tulip for receiving the longitudinal rod do not however allow the surgeon to precisely adjust the orientation of the longitudinal axis of the screw relative to the longitudinal rod in the sagittal plane of the patient, during the setting. in place of the osteosynthesis device. The precise relative positions of the vertebrae according to the local bending of the longitudinal rod are therefore not very easy to adjust during assembly of the device.
Le but de l'invention est de proposer un nouveau type de vis polyaxiale comportant une tulipe pour la réception de la tige longitudinale, avec lequel il deviendrait possible de fixer aisément les positionnements relatifs des os (ou des portions d'os si le dispositif est utilisé, par exemple, lors de la réduction de fractures d'os longs) concernés, en particulier de vertèbres dans le cas d'une chirurgie rachidienne.  The object of the invention is to propose a new type of polyaxial screw comprising a tulip for receiving the longitudinal rod, with which it would be possible to easily fix the relative positioning of the bones (or portions of bone if the device is used, for example, during the reduction of long bone fractures) concerned, in particular vertebrae in the case of spinal surgery.
A cet effet, l'invention a pour objet une vis osseuse polyaxiale pour dispositif d'ostéosynthèse destiné à relier une tige longitudinale et un os d'un patient, comportant une partie inférieure rectiligne filetée destinée à s'ancrer dans l'os, une tête présentant au moins localement une forme sphérique possédant un rayon de courbure r et dont la surface supérieure est destinée à venir au contact de ladite tige longitudinale, une tulipe filetée intérieurement dans sa partie supérieure, présentant un espace destiné à servir de réceptacle à ladite tige longitudinale du dispositif d'ostéosynthèse, et un bouchon fileté destiné à obturer ladite tulipe après l'insertion de la tige et à presser par serrage la tige contre la tête, la partie inférieure de ladite tulipe comportant un espace intérieur dont la paroi présente une surface autorisant une rotation de la tête dans ledit espace, caractérisée en ce que ladite surface de la paroi autorisant une rotation de la tête s'interrompt avant d'atteindre le bord inférieur de la tulipe, en ce qu'est ménagé en permanence, dans la partie la plus inférieure de l'espace, un espace entre ladite paroi et au moins une partie de la tête, quel que soit l'état de serrage du bouchon et la position angulaire de la vis par rapport à la tige, et en ce que les formes respectives de la tête de la vis et de la surface sont conçues pour que la pression exercée par la tige sur la tête lors du serrage du bouchon amène la vis dans une position perpendiculaire à la tige longitudinale dans le plan sagittal du patient, tout en conservant une polyaxialité de la vis dans le plan transversal du patient.  For this purpose, the subject of the invention is a polyaxial bone screw for an osteosynthesis device intended to connect a longitudinal rod and a bone of a patient, comprising a threaded rectilinear lower part intended to be anchored in the bone, a head having at least locally a spherical shape having a radius of curvature r and whose upper surface is intended to come into contact with said longitudinal rod, a tulip threaded internally in its upper part, having a space intended to serve as a receptacle for said rod longitudinal of the osteosynthesis device, and a threaded plug for closing said tulip after the insertion of the rod and pressing the rod against the head by clamping, the lower part of said tulip having an interior space whose wall has a surface allowing rotation of the head in said space, characterized in that said wall surface allowing rotation of the head stops before reaching the lower edge of the tulip, in that is formed permanently, in the lower part of the space, a space between said wall and at least a portion of the head , regardless of the clamping condition of the plug and the angular position of the screw relative to the rod, and in that the respective shapes of the screw head and the surface are designed so that the pressure exerted by the rod on the head when tightening the plug brings the screw in a position perpendicular to the longitudinal rod in the sagittal plane of the patient, while maintaining a polyaxiality of the screw in the transverse plane of the patient.
La tête de la vis peut présenter une surface supérieure tronquée perpendiculairement à l'axe longitudinal de la partie inférieure rectiligne filetée de la vis, ladite surface supérieure tronquée étant destinée à venir au contact de la tige longitudinale du dispositif d'ostéosynthèse. The head of the screw may have a truncated upper surface perpendicular to the longitudinal axis of the straight lower threaded portion of the screw, said truncated upper surface being intended to come into contact with the longitudinal rod of the osteosynthesis device.
Le rayon de courbure externe de la tête de la vis peut présenter, sur une portion de la tête, une valeur égale à r, la zone supérieure de la paroi de l'espace intérieur de la tulipe peut comporter deux évidements diamétralement opposés, qui ont pour fonction de guider la tête de la vis lorsque le bouchon est en cours de serrage et presse la tige contre la tête de la vis, la forme de ces évidements étant telle que, au droit de l'espace pour l'insertion de la tige, la paroi interne de la tulipe présente un rayon de courbure sensiblement égal à r.  The external radius of curvature of the head of the screw may have, on a portion of the head, a value equal to r, the upper zone of the wall of the inner space of the tulip may comprise two diametrically opposite recesses, which have to function to guide the head of the screw when the cap is being clamped and press the rod against the head of the screw, the shape of these recesses being such that, in line with the space for the insertion of the rod , the inner wall of the tulip has a radius of curvature substantially equal to r.
La vis peut être destinée à un dispositif d'ostéosynthèse rachidienne.  The screw may be intended for a spinal osteosynthesis device.
L'invention a également pour objet un dispositif d'ostéosynthèse comportant une tige longitudinale et des vis osseuses destinées à la relier à au moins un os d'un patient, caractérisé en ce qu'au moins une desdites vis osseuses est du type précédent.  The invention also relates to an osteosynthesis device comprising a longitudinal shaft and bone screws for connecting it to at least one bone of a patient, characterized in that at least one of said bone screws is of the above type.
Il peut s'agir d'un dispositif d'ostéosynthèse rachidienne.  It may be a spinal osteosynthesis device.
Comme on l'aura compris, l'invention consiste à concevoir une vis polyaxiale comportant une tulipe pour la réception de la tige longitudinale du dispositif d'ostéosynthèse, qui, lors du serrage de la tige longitudinale dans la tulipe au moyen du bouchon, va, dans le cas d'une utilisation en chirurgie rachidienne, imposer une orientation de l'axe longitudinal de la vis perpendiculaire à la tige dans le plan sagittal du patient, alors que dans le plan transversal du patient, l'angulation vis/tige prend une valeur libre et fixée par le serrage.  As will be understood, the invention consists in designing a polyaxial screw comprising a tulip for receiving the longitudinal rod of the osteosynthesis device, which, when tightening the longitudinal rod in the tulip by means of the stopper, goes in the case of use in spinal surgery, impose an orientation of the longitudinal axis of the screw perpendicular to the stem in the sagittal plane of the patient, while in the transverse plane of the patient, the screw / rod angulation takes a free value and fixed by tightening.
De cette façon, dans son ensemble la mise en place du dispositif d'ostéosynthèse est facilitée, et les vertèbres sont assurément et automatiquement positionnées optimalement dans le plan sagittal selon le cintrage local de la tige à leur niveau. L'axe longitudinal de la vis est assurément perpendiculaire à l'axe longitudinal de la tige, une fois celle-ci maintenue dans la tulipe par le serrage du bouchon. Vue dans ce plan sagittal, la vis semble donc être du type monoaxial. En revanche, dans le plan transversal, l'orientation de la vis par rapport à la tige reste libre, comme pour une vis polyaxiale classique.  In this way, as a whole the establishment of the osteosynthesis device is facilitated, and the vertebrae are assuredly and automatically positioned optimally in the sagittal plane according to the local bending of the rod at their level. The longitudinal axis of the screw is certainly perpendicular to the longitudinal axis of the rod, once it held in the tulip by tightening the cap. Seen in this sagittal plane, the screw seems to be of the monoaxial type. In contrast, in the transverse plane, the orientation of the screw relative to the rod remains free, as for a conventional polyaxial screw.
L'effet recherché est obtenu notamment parce ce que l'extrémité supérieure de la partie inférieure filetée de la vis, sur laquelle la tulipe s'articule, a une forme générale sphérique mais, au moins dans certaines variantes de l'invention, est tronquée de façon à présenter une surface supérieure perpendiculaire à l'axe longitudinal de la vis, et sur laquelle la tige va être pressée par le serrage du bouchon. Egalement, l'espace intérieur de la tulipe dans lequel ladite extrémité supérieure de la partie inférieure filetée de la vis est insérée a une forme qui impose, lors du serrage du bouchon, que la partie inférieure filetée de la vis prenne une angulation perpendiculaire à l'axe longitudinal de la tige dans la zone concernée. The desired effect is obtained in particular because the upper end of the threaded lower part of the screw, on which the tulip articulates, has a spherical general shape but, at least in certain variants of the invention, is truncated. so as to have an upper surface perpendicular to the longitudinal axis of the screw, and on which the rod will be pressed by tightening the plug. Also, the internal space of the tulip in which said upper end of the threaded lower portion of the screw is inserted has a shape which imposes, when tightening the cap, that the lower part screw thread takes an angulation perpendicular to the longitudinal axis of the rod in the area concerned.
L'invention sera mieux comprise à la lecture de la description qui suit, donnée en référence aux figures annexées suivantes :  The invention will be better understood on reading the description which follows, given with reference to the following appended figures:
- la figure 1 qui montre, en coupe longitudinale dans le plan sagittal, un exemple de vis polyaxiale de l'art antérieur lors du montage d'un dispositif d'ostéosynthèse rachidienne et la tige longitudinale de ce dispositif, avant le serrage du bouchon qui presse la tige contre l'extrémité supérieure de la partie filetée de la vis ;  FIG. 1 which shows, in longitudinal section in the sagittal plane, an example of a polyaxial screw of the prior art during the assembly of a spinal osteosynthesis device and the longitudinal rod of this device, before the tightening of the plug which press the rod against the upper end of the threaded portion of the screw;
- la figure 2 qui montre de la même façon cet exemple de vis de l'art antérieur après le serrage du bouchon ;  - Figure 2 which similarly shows this example of screw of the prior art after tightening the cap;
- la figure 3 qui représente schématiquement un alignement très imparfait des vertèbres du patient que l'on risque d'obtenir avec l'utilisation de la vis des figures 1 et 2 en combinaison avec la tige longitudinale du dispositif d'ostéosynthèse rachidienne ;  - Figure 3 which shows schematically a very imperfect alignment of the vertebrae of the patient that may be obtained with the use of the screw of Figures 1 and 2 in combination with the longitudinal rod of the spinal osteosynthesis device;
- les figures 4 à 6 qui montrent, en coupe longitudinale dans le plan sagittal, un exemple de vis polyaxiale selon l'invention lors du montage d'un dispositif d'ostéosynthèse rachidienne et la tige longitudinale de ce dispositif, à trois stades du serrage du bouchon qui presse la tige contre l'extrémité supérieure de la partie filetée de la vis ;  - Figures 4 to 6 which show, in longitudinal section in the sagittal plane, an example of a polyaxial screw according to the invention during the assembly of a spinal osteosynthesis device and the longitudinal rod of this device, at three stages of tightening plug which presses the rod against the upper end of the threaded portion of the screw;
- la figure 7 qui représente schématiquement l'alignement correct des vertèbres du patient que l'on obtient assurément avec l'utilisation de la vis des figures 4 à 6 en combinaison avec la tige longitudinale du dispositif d'ostéosynthèse rachidienne ;  - Figure 7 which shows schematically the correct alignment of the vertebrae of the patient that is certainly obtained with the use of the screw of Figures 4 to 6 in combination with the longitudinal rod of the spinal osteosynthesis device;
- les figures 8 à 10 qui représentent, de la même façon que sur les figures 4 à 6, un autre exemple de vis polyaxiale selon l'invention ;  - Figures 8 to 10 which show, in the same way as in Figures 4 to 6, another example of a polyaxial screw according to the invention;
- les figures 1 1 à 13 qui représentent plus en détail les composants de cet autre exemple : la vis en vue de face (figure 1 1 ), et la tulipe en perspective (figure 12) et en coupe selon A-A (figure 13)  - Figures 1 1 to 13 which represent more in detail the components of this other example: the screw in front view (Figure 1 1), and the tulip perspective (Figure 12) and in section along A-A (Figure 13)
Sur les figures 1 et 2 on a représenté en coupe longitudinale dans le plan sagittal du patient un exemple de vis polyaxiale 1 selon l'art antérieur et la tige longitudinale 2 que la vis 1 doit connecter rigidement à une vertèbre 3 (dans le cas privilégié qui fait l'objet de la description ; mais il doit être clair que les vis de l'art antérieur et les vis selon l'invention qui vont être décrites pourraient être utilisables pour connecter la tige 2 à tout autre type d'os - ou de portion d'os - sur lequel l'invention pourrait être utilisée). La vis 1 comporte une partie inférieure 4 rectiligne, filetée extérieurement, définissant l'axe longitudinal de la vis, et destinée à s'ancrer dans la vertèbre 3. Son extrémité supérieure 5 (que l'on appellera « tête » dans la suite du texte), qui émerge de la vertèbre 3, a une forme globalement sphérique et comporte, comme il est classique, une empreinte 6 de section polygonale (dans l'exemple représenté), dans laquelle le chirurgien peut insérer l'extrémité d'un tournevis afin d'enfoncer la vis 1 dans la vertèbre 3. FIGS. 1 and 2 show in longitudinal section in the sagittal plane of the patient an example of a polyaxial screw 1 according to the prior art and the longitudinal rod 2 that the screw 1 must rigidly connect to a vertebra 3 (in the preferred case which is the subject of the description, but it must be clear that the screws of the prior art and the screws according to the invention which will be described could be used to connect the rod 2 to any other type of bone - or of bone portion - on which the invention could be used). The screw 1 has a lower portion 4 rectilinear externally threaded, defining the longitudinal axis of the screw, and intended to anchor in the vertebra 3. Its upper end 5 (which will be called "head" in the continuation of text), which emerges from the vertebra 3, has a generally spherical shape and comprises, as is conventional, an imprint 6 of polygonal section (in the example shown), in which the surgeon can insert the end of a screwdriver to drive the screw 1 into the vertebra 3.
La vis 1 comporte également une « tulipe » 7 servant de réceptacle à la tige longitudinale 2. Cette tulipe 7 comporte une partie supérieure composée de deux parois se faisant face et définissant un espace 8 destiné à être traversé par la tige 2. Seule l'une 9 de ces parois est visible sur les figures. Ces parois 9 portent sur leur surface tournée vers l'espace 8 un filetage 10 permettant l'insertion et le vissage d'un bouchon cylindrique 1 1 dont la paroi externe comporte un filetage 12 correspondant à celui des parois de la tulipe 7 et qui comporte un espace interne 13 polygonal (dans l'exemple représenté) pour l'insertion d'un tournevis qui permet de réaliser le vissage du bouchon 1 1 dans la tulipe 7. Le bouchon 1 1 permet d'obturer la tulipe 7 après l'insertion de la tige 2 et de presser la tige 2 contre la tête 5 à l'issue du vissage.  The screw 1 also comprises a "tulip" 7 serving as a receptacle for the longitudinal rod 2. This tulip 7 comprises an upper part composed of two walls facing each other and defining a space 8 intended to be traversed by the rod 2. Only the a 9 of these walls is visible in the figures. These walls 9 carry on their surface facing the space 8 a threading 10 allowing the insertion and screwing of a cylindrical plug 1 1 whose outer wall has a thread 12 corresponding to that of the walls of the tulip 7 and which comprises a polygonal internal space 13 (in the example shown) for the insertion of a screwdriver which makes it possible to screw the plug 1 1 into the tulip 7. The plug 1 1 makes it possible to close the tulip 7 after the insertion of the rod 2 and press the rod 2 against the head 5 at the end of the screwing.
La partie inférieure interne de la tulipe 7 comporte également une cavité 14 dont la paroi est de forme sphérique jusqu'au bord inférieur 15 de la tulipe 7, et dans laquelle vient se loger la tête 5 de la partie inférieure 4 de la vis 1 . Ainsi, la tulipe 7 et la tête 5 sont articulées l'une sur l'autre à la manière d'une rotule.  The inner lower part of the tulip 7 also comprises a cavity 14 whose wall is of spherical shape to the lower edge 15 of the tulip 7, and in which is housed the head 5 of the lower part 4 of the screw 1. Thus, the tulip 7 and the head 5 are hinged to one another in the manner of a ball joint.
La figure 1 représente la vis 1 et la tige 2 avec la tige 2 et le bouchon 1 1 insérés dans la tulipe 7 mais non encore bloqués. Lorsque le bouchon 1 1 est serré par le chirurgien, il presse la tige 2 contre la tête 5 et on aboutit à la situation montrée sur la figure 2. Comme la cavité 14 est sphérique et que sa paroi est au contact de la tête 5 jusqu'au bord inférieur 15 de la tulipe 7, la pression verticale exercée par la tige 2 maintient de façon permanente la partie rectiligne 4 et la tulipe 7 de la vis 1 (et, par voie de conséquence, la tige 2 qui traverse la tulipe 7) dans des orientations relatives qu peuvent être quelconques à la fois dans le plan sagittal et dans le plan transversal, puisque le bord inférieur de la cavité 14 de la tulipe 7, qui débouche lui-même sur le bord inférieur 15 de la tulipe 7, est au contact de la tête 5. Le chirurgien n'a pas la possibilité de maîtriser aisément ces orientations relatives. On risque ainsi fortement d'aboutir à une situation insatisfaisante telle que celle représentée schématiquement sur la figure 3, et dans laquelle les vertèbres 3, vues dans le plan sagittal, ne suivent qu'imparfaitement le cintrage de la tige 2 qui est pourtant censé restituer au rachis une courbure correcte dans le plan sagittal de la région traitée. D'autre part, comme on le voit sur la figure 2, la surface de contact entre la tête 5 et la tige 2 est réduite, ce qui est défavorable à une très bonne stabilité dans le temps de leurs orientations relatives. Figure 1 shows the screw 1 and the rod 2 with the rod 2 and the cap 1 1 inserted in the tulip 7 but not yet blocked. When the cap 1 1 is tightened by the surgeon, it presses the rod 2 against the head 5 and leads to the situation shown in Figure 2. As the cavity 14 is spherical and its wall is in contact with the head 5 until at the lower edge 15 of the tulip 7, the vertical pressure exerted by the rod 2 permanently maintains the rectilinear part 4 and the tulip 7 of the screw 1 (and, consequently, the rod 2 which passes through the tulip 7 ) in relative orientations that can be any both in the sagittal plane and in the transverse plane, since the lower edge of the cavity 14 of the tulip 7, which opens itself to the lower edge 15 of the tulip 7, is in contact with the head 5. The surgeon is not able to easily control these relative orientations. There is thus a strong risk of leading to an unsatisfactory situation such as that shown diagrammatically in FIG. 3, and in which the vertebrae 3, seen in the sagittal plane, follow imperfectly the bending of the rod 2 which is nevertheless supposed to restore at the spine a correct curvature in the sagittal plane of the treated area. On the other hand, as seen in Figure 2, the contact surface between the head 5 and the rod 2 is reduced, which is disadvantageous to a very good stability over time of their relative orientations.
Les figures 4 à 6 montrent un premier exemple de mise en œuvre de la présente invention, à trois stades de sa mise en place. Par rapport à l'art antérieur des figures 1 et 2, on retrouve des éléments communs, de par leurs fonctions et leurs formes générales, à savoir la vis 1 avec sa partie inférieure 4 rectiligne filetée et sa tête 5 qui, dans l'exemple représenté, est de forme hémisphérique : la tête 5 est, ici, tronquée sensiblement au niveau de son équateur (dans l'exemple représenté), et en tout cas selon un plan perpendiculaire à l'axe longitudinal de la vis 1 , avec son empreinte 6, la tulipe 7 (avec, cependant, une différence importante de la configuration de la tulipe 7 par rapport à celle des figures 1 et 2 qui sera commentée plus loin), le bouchon 1 1 , et la tige longitudinale 2 du dispositif d'ostéosynthèse.  Figures 4 to 6 show a first example of implementation of the present invention, at three stages of its implementation. Compared to the prior art of FIGS. 1 and 2, there are common elements, by their functions and their general forms, namely the screw 1 with its threaded straight bottom part 4 and its head 5 which, in the example shown, is of hemispherical shape: the head 5 is, here, truncated substantially at its equator (in the example shown), and in any case in a plane perpendicular to the longitudinal axis of the screw 1, with its imprint 6, the tulip 7 (with, however, a significant difference in the configuration of the tulip 7 compared to that of Figures 1 and 2 which will be discussed later), the cap 1 1, and the longitudinal rod 2 of the device osteosynthesis.
Une différence essentielle entre l'invention et l'art antérieur des figures 1 et 2 est que, selon l'invention, l'espace intérieur 16 de la tulipe 5 a sa paroi qui comporte dans sa partie inférieure, une surface 17 de forme sphérique qui, là encore, autorise une rotation de la tête 5 à l'intérieur de cet espace 16. Mais cette surface sphérique 17 s'interrompt avant d'atteindre le bord inférieur 15 de la tulipe 7 de façon à, selon l'invention, ménager en permanence, dans la partie la plus inférieure de l'espace 15, un espace 18 entre ladite paroi et au moins une partie de la tête 5 de la vis 1 , quel que soit l'état de serrage du bouchon 1 1 et la position angulaire de la vis 1 par rapport à la tige 2.  An essential difference between the invention and the prior art of Figures 1 and 2 is that, according to the invention, the inner space 16 of the tulip 5 has its wall which has in its lower part, a surface 17 of spherical shape which, again, allows a rotation of the head 5 inside this space 16. But this spherical surface 17 stops before reaching the lower edge 15 of the tulip 7 so as, according to the invention, at all times, in the lowest part of the space 15, a space 18 between said wall and at least a part of the head 5 of the screw 1, regardless of the tightening state of the plug 1 1 and the angular position of the screw 1 relative to the rod 2.
La figure 4 montre, dans le plan sagittal, cet exemple de dispositif selon l'invention dans un état comparable à celui du dispositif selon l'art antérieur dans l'état représenté sur la figure 1 , avec la tige longitudinale 2 insérée dans la tulipe 7 et le bouchon 1 1 non encore serré. Le serrage du bouchon 5 a déjà débuté, et la tige 2, à cet instant, est en contact d'une part avec la surface inférieure du bouchon 1 1 , et d'autre part avec une portion de la surface supérieure plane de la tête 5.  FIG. 4 shows, in the sagittal plane, this example of a device according to the invention in a state comparable to that of the device according to the prior art in the state represented in FIG. 1, with the longitudinal rod 2 inserted into the tulip 7 and the cap 1 1 not yet tightened. The tightening of the plug 5 has already begun, and the rod 2, at this moment, is in contact on the one hand with the lower surface of the plug 1 1, and on the other hand with a portion of the flat upper surface of the head 5.
La figure 5 montre l'ensemble à un stade ultérieur du serrage du bouchon 1 1 . Du fait de la présence constante, selon l'invention, d'un espace 18 entre la paroi de l'espace intérieur 16 de la tulipe 7 et la tête 5 de la vis 1 , la pression exercée par la tige 2 sur la tête 5 tend, sans rencontrer de résistance (contrairement à ce qui se passe dans l'art antérieur des figures 1 et 2), à réorienter la tige filetée 4 de la vis 1 dans le plan sagittal, pour finalement l'amener, après le serrage complet du bouchon 1 1 , à l'état représenté sur la figure 6. La tige 2 est alors au contact de la tête 5 selon une ligne qui traverse toute la surface supérieure de la tête 5, de sorte qu'il y a automatiquement une perpendicularité entre la tige longitudinale 2 et l'axe longitudinal de la vis 1 dans le plan sagittal. En revanche, dans le plan transversal, les orientations respectives de la tige 2 et de la vis 1 demeurent libres, de sorte que, dans ce plan transversal, le caractère polyaxial de la vis 1 est conservé. Figure 5 shows the assembly at a later stage of the clamping of the cap 1 1. Due to the constant presence, according to the invention, of a space 18 between the wall of the internal space 16 of the tulip 7 and the head 5 of the screw 1, the pressure exerted by the rod 2 on the head 5 tends, without encountering resistance (contrary to what happens in the prior art of Figures 1 and 2), to reorient the threaded rod 4 of the screw 1 in the sagittal plane, to finally bring it after the complete tightening of the plug 1 1, in the state shown in Figure 6. The rod 2 is then in contact with the head 5 along a line that runs through the entire upper surface of the head 5, so that there is automatically a perpendicularity between the longitudinal rod 2 and the longitudinal axis of the screw 1 in the sagittal plane. In however, in the transverse plane, the respective orientations of the rod 2 and the screw 1 remain free, so that in this transverse plane, the polyaxial nature of the screw 1 is retained.
Il est particulièrement remarquable que cette perpendicularité dans le plan sagittal soit obtenue de façon automatique lors du serrage du bouchon 1 1 , sans que le chirurgien n'ait besoin de prendre des précautions particulières pour l'obtenir. Elle est obtenue au moyen d'une configuration simple des différentes pièces de la vis 1 , notamment de la tête sphérique 5 qui n'a besoin que d'être tronquée perpendiculairement à l'axe longitudinal de la vis 1 . En particulier, aucune pièce intermédiaire entre la tige 2 et la tête 5 n'est nécessaire pour assurer la bonne mise en place et le maintien en position de l'ensemble : la tige 2 peut exercer directement sa pression sur la tête 5.  It is particularly remarkable that this perpendicularity in the sagittal plane is obtained automatically when tightening the cap 1 1, without the surgeon needs to take special precautions to obtain it. It is obtained by means of a simple configuration of the various parts of the screw 1, in particular of the spherical head 5 which only needs to be truncated perpendicularly to the longitudinal axis of the screw 1. In particular, no intermediate piece between the rod 2 and the head 5 is necessary to ensure the proper positioning and maintenance in position of the assembly: the rod 2 can directly exert its pressure on the head 5.
On se retrouve ainsi dans la configuration schématisée sur la figure 7. Dans le plan sagittal, les axes longitudinaux de chaque vis sont chacun parfaitement perpendiculaires à la tige 2 au niveau de leur connexion à celle-ci par la tulipe 7. Les positionnements des vertèbres 3 suivent donc très bien le cintrage de la tige 2. La comparaison entre les figures 3 et 7 montre de façon claire que l'invention, contrairement à l'art antérieur, garantit un positionnement relatif des vertèbres 3 dans le plan sagittal conforme à ce qui est souhaité par le chirurgien et recherché par le cintrage précis de la tige 2.  We thus find ourselves in the configuration shown schematically in Figure 7. In the sagittal plane, the longitudinal axes of each screw are each perfectly perpendicular to the rod 2 at their connection to it by the tulip 7. The positioning of the vertebrae 3 thus follow very well the bending of the rod 2. The comparison between FIGS. 3 and 7 clearly shows that the invention, contrary to the prior art, guarantees a relative positioning of the vertebrae 3 in the sagittal plane conforming to this which is desired by the surgeon and sought by the precise bending of the stem 2.
Les figures 8 à 13 représentent une variante de l'invention dans une configuration qui réalise la perpendicularité finale de la vis et de la tige dans le plan sagittal du patient et la polyaxialité dans le plan transversal du patient par d'autres moyens que ceux de la variante précédente.  FIGS. 8 to 13 show a variant of the invention in a configuration that achieves the final perpendicularity of the screw and the shaft in the sagittal plane of the patient and the polyaxiality in the transverse plane of the patient by means other than those of the previous variant.
La tête 5 est, dans l'exemple représenté, tronquée perpendiculairement à l'axe de la vis 1 au-dessus de son équateur, et offre ainsi une surface de contact avec la tige 2 un peu plus réduite que dans la variante représentée sur les figures 4 à 6, mais qui reste néanmoins suffisante pour que le dispositif puisse être orienté puis bloqué correctement lors du serrage du bouchon 1 1 . Cependant, une troncature de la tête 5 perpendiculairement à l'axe longitudinal de la vis 1 ne serait ici, théoriquement, pas nécessaire, contrairement au cas de la précédente variante. La tête 5 pourrait, ici, au regard des principes sur lesquels repose l'invention, être parfaitement sphérique dans sa partie supérieure.  The head 5 is, in the example shown, truncated perpendicularly to the axis of the screw 1 above its equator, and thus provides a contact surface with the rod 2 a little smaller than in the variant shown in FIGS. Figures 4 to 6, but which is still sufficient for the device can be oriented and properly blocked when tightening the cap 1 1. However, a truncation of the head 5 perpendicular to the longitudinal axis of the screw 1 would not here, theoretically, not necessary, unlike the case of the previous variant. The head 5 could here, in view of the principles on which the invention is based, be perfectly spherical in its upper part.
Une telle troncature permet cependant d'offrir une plus grande surface de contact entre la tige 2 et la tête 5, et de fiabiliser ainsi la mise en place et le fonctionnement du dispositif. Mais surtout, la troncature résulte du ménagement de l'empreinte 6 sur la tête 5 pour l'insertion d'un tournevis. On pourra se limiter à une troncature de la tête 5 d'une hauteur qui serait juste nécessaire au ménagement de l'empreinte 6, sans devoir, comme dans la variante de l'invention précédemment décrite, offrir une surface de contact de grande ampleur à la tige longitudinale 2. Such truncation, however, provides a greater contact area between the rod 2 and the head 5, and thus make reliable the establishment and operation of the device. But above all, the truncation results from the relief of the impression 6 on the head 5 for the insertion of a screwdriver. We can limit ourselves to a truncation of the head 5 of a height that would be just necessary to the relief of the footprint 6, without having, as in the variant of the invention described above, provide a large contact surface to the longitudinal rod 2.
Egalement, l'espace intérieur 16 de la tulipe 7 présente une plus grande hauteur, du fait que la tête 5 est plus volumineuse et aussi que, comme on le verra, la conformation de cet espace 16 est plus complexe que dans le cas des figures 4 à 6. Sa surface sphérique 17 se poursuit par une portion tronconique 19, dimensionnée pour ne pas gêner la rotation de la tête 5 lors du serrage du bouchon 1 1 , et qui participe donc à la délimitation de l'espace 18 selon l'invention.  Also, the interior space 16 of the tulip 7 has a greater height, because the head 5 is more voluminous and also that, as will be seen, the conformation of this space 16 is more complex than in the case of the figures 4 to 6. Its spherical surface 17 continues with a frustoconical portion 19, dimensioned so as not to hinder the rotation of the head 5 during the clamping of the plug 1 1, and which therefore participates in the delimitation of the space 18 according to the invention.
Dans cet exemple, la tête 5 de la vis 1 présente une forme qui peut, prise dans son ensemble, ne pas correspondre à une sphère ou une portion de sphère. Le rayon de courbure externe de la tête 5 est ainsi, dans l'exemple représenté, variable selon la hauteur de la tête 5. Sur une portion de la tête 5, il présente une valeur « r » bien définie, dont il sera question plus loin à propos de la tulipe 7. Immédiatement sous la tête 5, la vis 1 présente une portion 20 de diamètre rétréci, qui lui donne la possibilité de se mouvoir assurément dans la partie la plus inférieure 18 de l'espace intérieur 16 de la tulipe 5 sans y interférer avec la paroi de l'espace 16. La mise en position de la vis 1 lors du serrage du bouchon 1 1 n'est donc pas gênée.  In this example, the head 5 of the screw 1 has a shape that can, taken as a whole, not correspond to a sphere or a sphere portion. The outer radius of curvature of the head 5 is thus, in the example shown, variable according to the height of the head 5. On a portion of the head 5, it has a well-defined value "r", which will be discussed more far away from the tulip 7. Immediately under the head 5, the screw 1 has a portion 20 of narrowed diameter, which gives it the possibility to move undoubtedly in the lower part 18 of the interior space 16 of the tulip 5 without interfering with the wall of the space 16. The positioning of the screw 1 when tightening the cap 1 1 is not embarrassed.
Les figures 12 et 13 représentant la tulipe 7 de cette deuxième variante, conjuguées à la figure 1 1 représentant la vis 1 , permettent de comprendre comment se réalise la mise en position de la vis 1 lors du serrage.  Figures 12 and 13 showing the tulip 7 of this second variant, together with Figure 1 1 representing the screw 1, to understand how the setting in position of the screw 1 during tightening.
La partie inférieure 18 de l'espace intérieur 16 de la tulipe 7 est conformée d'une façon comparable à celle que l'on utilise sur la première variante de l'invention précédemment décrite. De cette façon, en conjugaison avec le dimensionnement de la vis 1 dans la région correspondante, la polyaxialité de la vis 1 dans le plan transversal est assurée.  The lower portion 18 of the inner space 16 of the tulip 7 is shaped in a manner comparable to that used in the first variant of the invention described above. In this way, in conjunction with the dimensioning of the screw 1 in the corresponding region, the polyaxiality of the screw 1 in the transverse plane is ensured.
La zone supérieure de la paroi de l'espace intérieur 16 de la tulipe 7 n'a, ici, pas une forme uniformément sphérique et correspondant sensiblement au rayon de courbure de la tête 5 de la vis 1 , comme c'est le cas dans la variante des figures 4 à 6. Comme cela est visible sur la figure 13 plus particulièrement, cette paroi comporte deux évidements 21 , 22 diamétralement opposés. Ces évidements 21 , 22 ont pour fonction de guider la tête 5 de la vis 1 lorsque le bouchon 1 1 est en cours de serrage et presse la tige 2 contre la tête 5 de la vis 1 . La forme de ces évidements 21 , 22 est telle que, au droit de l'espace 8 pour l'insertion de la tige 2, qui sépare les deux parois 9 de la tulipe 5 filetées intérieurement et qui définissent cet espace 8, la paroi interne de la tulipe 5 présente un rayon de courbure sensiblement égal à la valeur « r » vue précédemment à propos du rayon de courbure local de la tête 5 de la vis 1 . De cette façon, la vis 1 et la tulipe 5 peuvent librement effectuer une rotation l'une par rapport à l'autre dans le plan transversal du patient, du fait de la présence permanente, dans la partie la plus inférieure de l'espace intérieur 16 de la tulipe 7, d'un espace 18 entre ladite paroi et au moins une partie de la tête 5 de la vis 1 , quel que soit l'état de serrage du bouchon 1 1 et la position angulaire de la vis 1 par rapport à la tige 2. En revanche, lors du serrage du bouchon 1 1 , la vis 1 guidée par les évidements 21 , 22 de la tulipe 7, vient naturellement se placer, dans le plan sagittal du patient, perpendiculairement à l'axe de la tige 2 au niveau de sa connexion à la tulipe 5, comme on le voit sur les figures 8 à 10. The upper zone of the wall of the inner space 16 of the tulip 7 does not here have a uniformly spherical shape and corresponds substantially to the radius of curvature of the head 5 of the screw 1, as is the case in the variant of Figures 4 to 6. As shown in Figure 13 more particularly, this wall has two recesses 21, 22 diametrically opposed. These recesses 21, 22 serve to guide the head 5 of the screw 1 when the plug 1 1 is being clamped and presses the rod 2 against the head 5 of the screw 1. The shape of these recesses 21, 22 is such that, in line with the space 8 for the insertion of the rod 2, which separates the two walls 9 of the tulip 5 internally threaded and which define this space 8, the inner wall of the tulip 5 has a radius of curvature substantially equal to the value "r" seen previously about the local radius of curvature of the head 5 of the screw 1. In this way, the screw 1 and the tulip 5 can freely rotate relative to each other in the transverse plane of the patient, because of the permanent presence, in the lower part of the interior space 16 of the tulip 7, a space 18 between said wall and at least a portion of the head 5 of the screw 1, regardless of the clamping state of the cap 1 1 and the angular position of the screw 1 relative to on the other hand, when tightening the cap 1 1, the screw 1 guided by the recesses 21, 22 of the tulip 7, is naturally placed in the sagittal plane of the patient, perpendicular to the axis of the rod 2 at its connection to the tulip 5, as seen in Figures 8 to 10.
Il va de soi que les exemples de vis 1 selon l'invention représentés sur les figures ne sont pas limitatifs, l'essentiel étant que les formes relatives de la tête 5 de la vis 1 et de la paroi 17 délimitant l'espace intérieur 16 de la tulipe 7 conduisent la vis 1 à se mettre de façon spontanée dans une position perpendiculaire à la tige 2 dans le plan sagittal du patient lors du serrage du bouchon 1 1 , sous l'effet de la pression exercée par la tige 2 sur la tête 5 de la vis 1 , et que cette position soit maintenue après le serrage lors de l'utilisation du dispositif d'ostéosynthèse.  It goes without saying that the examples of screws 1 according to the invention shown in the figures are not limiting, the essential being that the relative shapes of the head 5 of the screw 1 and the wall 17 defining the interior space 16 of the tulip 7 lead the screw 1 to be placed spontaneously in a position perpendicular to the rod 2 in the sagittal plane of the patient during the tightening of the cap 1 1, under the effect of the pressure exerted by the rod 2 on the head 5 of the screw 1, and that this position is maintained after tightening during use of the osteosynthesis device.

Claims

REVENDICATIONS
1 . - Vis osseuse polyaxiale (1 ) pour dispositif d'ostéosynthèse destiné à relier une tige longitudinale (2) et un os (3) d'un patient, comportant une partie inférieure (4) rectiligne filetée destinée à s'ancrer dans l'os (3), une tête (5) présentant au moins localement une forme sphérique possédant un rayon de courbure (r) et dont la surface supérieure est destinée à venir au contact de ladite tige longitudinale (2), une tulipe (7) filetée intérieurement dans sa partie supérieure, présentant un espace (8) destiné à servir de réceptacle à ladite tige (2) longitudinale du dispositif d'ostéosynthèse, et un bouchon (1 1 ) fileté destiné à obturer ladite tulipe (7) après l'insertion de la tige (2) et à presser par serrage la tige (2) contre la tête (5), la partie inférieure de ladite tulipe (7) comportant un espace intérieur (16) dont la paroi présente une surface (17) autorisant une rotation de la tête (5) dans ledit espace (16), caractérisée en ce que ladite surface (17) de la paroi autorisant une rotation de la tête (5) s'interrompt avant d'atteindre le bord inférieur (15) de la tulipe (7), en ce qu'est ménagé en permanence, dans la partie la plus inférieure de l'espace (16), un espace (18) entre ladite paroi et au moins une partie de la tête (5), quel que soit l'état de serrage du bouchon (1 1 ) et la position angulaire de la vis (1 ) par rapport à la tige (2), et en ce que les formes respectives de la tête (5) de la vis (1 ) et de la surface (17) sont conçues pour que la pression exercée par la tige (2) sur la tête (5) lors du serrage du bouchon (1 1 ) amène la vis (1 ) dans une position perpendiculaire à la tige longitudinale (2) dans le plan sagittal du patient, tout en conservant une polyaxialité de la vis (1 ) dans le plan transversal du patient. 1. - Polyaxial bone screw (1) for an osteosynthesis device for connecting a longitudinal rod (2) and a bone (3) of a patient, comprising a threaded rectilinear lower portion (4) intended to anchor in the bone (3), a head (5) having at least locally a spherical shape having a radius of curvature (r) and whose upper surface is intended to come into contact with said longitudinal rod (2), a tulip (7) threaded internally at its upper part, having a space (8) intended to serve as a receptacle for said longitudinal rod (2) of the osteosynthesis device, and a threaded plug (1 1) intended to close said tulip (7) after the insertion of the shank (2) and pressing clamping the shank (2) against the head (5), the lower part of said shank (7) having an interior space (16) whose wall has a surface (17) allowing a rotation of the head (5) in said space (16), characterized in that the said surface (17) of the wall allowing a rotation of the head (5) is interrupted before reaching the lower edge (15) of the tulip (7), that is formed permanently, in the part of the lower space (16), a space (18) between said wall and at least a portion of the head (5), regardless of the tightening state of the plug (1 1) and the angular position of the screw (1) with respect to the rod (2), and in that the respective shapes of the head (5) of the screw (1) and the surface (17) are designed so that the pressure exerted by the rod ( 2) on the head (5) during the tightening of the plug (1 1) brings the screw (1) in a position perpendicular to the longitudinal rod (2) in the sagittal plane of the patient, while maintaining a polyaxiality of the screw ( 1) in the transverse plane of the patient.
2. - Vis osseuse polyaxiale selon la revendication 1 , caractérisée en ce que la tête (5) de la vis (1 ) présente une surface supérieure tronquée perpendiculairement à l'axe longitudinal de la partie inférieure (4) rectiligne filetée de la vis (1 ), ladite surface supérieure tronquée étant destinée à venir au contact de la tige longitudinale (2) du dispositif d'ostéosynthèse.  2. - polyaxial bone screw according to claim 1, characterized in that the head (5) of the screw (1) has a truncated upper surface perpendicular to the longitudinal axis of the lower portion (4) threaded rectilinear screw ( 1), said truncated upper surface being intended to come into contact with the longitudinal rod (2) of the osteosynthesis device.
3. - Vis osseuse polyaxiale selon la revendication 1 , caractérisée en ce que le rayon de courbure externe de la tête (5) de la vis (1 ) présente, sur une portion de la tête (5), une valeur égale audit rayon de courbure (r), en ce que la zone supérieure de la paroi de l'espace intérieur (16) de la tulipe (7) comporte deux évidements (21 , 22) diamétralement opposés, qui ont pour fonction de guider la tête (5) de la vis (1 ) lorsque le bouchon (1 1 ) est en cours de serrage et presse la tige (2) contre la tête (5) de la vis (1 ), la forme de ces évidements (21 , 22) est telle que, au droit de l'espace (8) pour l'insertion de la tige (2), la paroi interne de la tulipe (7) présente un rayon de courbure sensiblement égal audit rayon de courbure (r) de la tête (5). 3. - polyaxial bone screw according to claim 1, characterized in that the outer radius of curvature of the head (5) of the screw (1) has, on a portion of the head (5), a value equal to said radius of curvature (r), in that the upper zone of the wall of the internal space (16) of the tulip (7) has two recesses (21, 22) diametrically opposed, whose function is to guide the head (5) of the screw (1) when the plug (1 1) is being clamped and presses the rod (2) against the head (5) of the screw (1), the shape of these recesses (21, 22) is such that, in line with the space (8) for the insertion of the rod (2), the inner wall of the tulip (7) has a radius of curvature substantially equal to the radius of curvature (r) of the head (5). ).
4. - Vis osseuse polyaxiale selon la revendication 1 , caractérisée en ce qu'elle est destinée à un dispositif d'ostéosynthèse rachidienne. 4. - Polyaxial bone screw according to claim 1, characterized in that it is intended for a spinal osteosynthesis device.
5. - Dispositif d'ostéosynthèse comportant une tige longitudinale (2) et des vis osseuses destinées à la relier à au moins un os d'un patient, caractérisé en ce que au moins une desdites vis osseuses (1 ) est du type selon l'une des revendications 1 à 3.  5. - Osteosynthesis device comprising a longitudinal rod (2) and bone screws intended to connect it to at least one bone of a patient, characterized in that at least one of said bone screws (1) is of the type according to one of claims 1 to 3.
6. - Dispositif selon la revendication 5, caractérisé en ce qu'il s'agit d'un dispositif d'ostéosynthèse rachidienne.  6. - Device according to claim 5, characterized in that it is a spinal osteosynthesis device.
PCT/EP2018/062768 2017-05-16 2018-05-16 Polyaxial bone screw for an osteosynthesis device, and osteosynthesis device comprising same WO2018210946A1 (en)

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FR1754287A FR3066380A1 (en) 2017-05-16 2017-05-16 POLYAXIAL BONE SCREW FOR OSTEOSYNTHESIS DEVICE, AND OSTEOSYNTHESIS DEVICE COMPRISING SAME.
FR1754287 2017-05-16

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IT201900002119A1 (en) 2019-02-13 2020-08-13 Vese Silvana Device for osteosynthesis

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US20030187439A1 (en) * 2002-03-27 2003-10-02 Biedermann Motech Gmbh Bone anchoring device for stabilizing bone segments and seat part of a bone anchoring device
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US20150196329A1 (en) * 2000-11-10 2015-07-16 Biedermann Technologies Gmbh & Co. Kg Bone screw
US20030187439A1 (en) * 2002-03-27 2003-10-02 Biedermann Motech Gmbh Bone anchoring device for stabilizing bone segments and seat part of a bone anchoring device
US20100160965A1 (en) * 2008-12-22 2010-06-24 Zimmer Spine, Inc. Bone Anchor Assembly and Methods of Use

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Publication number Priority date Publication date Assignee Title
IT201900002119A1 (en) 2019-02-13 2020-08-13 Vese Silvana Device for osteosynthesis

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