FR2831419A1 - Spinal support fixator anchor screw has bone screw with locking nut for ball joint connection to fixing rod - Google Patents

Abstract

The spinal support anchor screw has a bone screw (1) with a threaded cylindrical section (5) and a stop collar (7). A locking nut (8) is threaded onto the threaded shank to fix a slide (4) on a fixing rod (3). A ball joint is provided to allow adjustment of the connecting slide and the fixing rod. The ball joint is held by the locking nut.

Description

<Desc / Clms Page number 1>

APPARATUS FOR MAINTAINING RACHIS
A BALL JOINT ASSEMBLY
The present invention relates to an apparatus for ensuring the maintenance of the vertebrae in a desired position. Such an apparatus is used for the treatment of a spine presenting an abnormal deviation, of degenerative or traumatic origin.

 For example, osteoarthritis or vertebral fractures can be treated to correct spinal deviations such as scoliosis, lordosis and kyphosis.

 US Pat. No. 4,648,388 discloses an apparatus for treating the spine comprising anchoring elements in the vertebrae, a securing rod with a circular section and a smooth outer surface, and connecting slides for connecting elements. anchoring to the securing rod. The anchoring elements are screws having three main parts, a first helical threaded end portion adapted for penetration and holding in the bone, a smooth cylindrical intermediate portion of reduced diameter, and a second end portion. with helical thread suitable for tightening a tightening nut. The connecting sliders comprise a clamping portion shaped to surround a section of the securing rod, and a connecting portion protruding laterally and pierced with two corresponding holes to be traversed by the anchoring screw with little play. The anchoring screw is first screwed into the bone, the connecting slide connected to the securing rod is then fitted onto the intermediate cylindrical portion of the anchoring screw, and the tightening nut is finally screwed on. on the second threaded portion of the clamping screw for pressing the connecting slide against a vertebra and for simultaneously tightening the connecting slide around the securing rod.

 Such an apparatus is intended to ensure the maintenance of the spine according to an appropriate curvature. It turns out that the installation of this device is not very easy. In particular, it is often difficult to adapt the connecting slide on the cylindrical intermediate portion of the anchoring screw when the latter has a

<Desc / Clms Page number 2>

 oblique orientation to follow the abnormal orientation of the vertebra before treatment.

 EP-A-0 408 489 discloses an apparatus for connecting two vertebrae, by means of two double threaded pedicle screws and two slides connected by a threaded rod to adjust the spacing. The screw comprises an intermediate stop plate with a spherical male bearing allowing inclination adjustment in all directions with respect to the slide by partially engaging in a cylindrical hole of the slide whose internal diameter is much greater than that of the screw. . The tightening of a tightening nut on the threaded portion of the screw ensures a locking in rotation, the nut bearing on a washer interposed against the slide. This device, which seems suitable for the spacing adjustment of two successive vertebrae, is totally unsuitable for holding more than two vertebrae. It also requires the addition of washers, which complicates the implementation, increases the risk of loss of parts and increases the cost of production.

 WO-A-91 11967 discloses a spine treatment apparatus comprising double-threaded pedicle screws and intermediate stop plate, on which is reported a slider shaped to receive and retain a securing rod. The slide has a lower groove in which the stop plate engages to prevent its rotation relative to the screw, and has an upper groove in which the securing rod engages. The threaded portion of the screw traverses the slider with little clearance, and a frustoconical lower bearing locking nut is screwed onto the threaded portion and laterally forces the securing rod in the upper groove of the slider for locking. The installation of this device is not very easy, for the same reasons as those mentioned in relation to US-A-4,648,388.

 The problem proposed by the present invention is to design a new structure of spine treatment device with connecting rod and connecting slides for anchoring elements, which ensures both an effective attachment of the vertebrae and a greater ease of operation. laying and setting of

<Desc / Clms Page number 3>

 position of the elements relative to each other in three-dimensional. In particular, it is sought to allow the tilt adjustment of the slider in position on a screw or other anchoring element, under conditions favoring the installation of the apparatus and nevertheless ensuring an effective mechanical strength.

 For this, the spine treatment apparatus according to the present invention comprises: - anchoring elements in the vertebrae, each having a threaded cylindrical portion on which a tightening nut is screwed, and having an anchoring portion connected to the cylindrical portion threaded by an intermediate stop flange, - at least one securing rod, - connecting sliders for connecting anchoring elements to the securing rod, the connecting sliders having a first passage shaped to be traversed by the threaded cylindrical portion of anchoring element to ensure their attachment to an anchoring element, the connecting slides having clamping means for selectively tightening or loosening the fastening rod in the connecting slide, - the collar of stop comprising a male spherical bearing surface engaging a corresponding lower female spherical surface a around the lower entrance of the first passage of the connecting slide, the first passage of the connecting slide having a diameter greater than the diameter of the threaded cylindrical portion of the anchoring element to allow angular oscillation of the connecting slide to the distance from the axis on the anchoring element before tightening the clamping nut; according to the invention the connecting slider comprises a convex upper spherical surface around the upper inlet of the first passage of the connecting slider, and the clamping nut has a corresponding concave lower spherical surface which directly receives said convex upper spherical surface of link slide.

 Such a structure with several spherical contact surfaces constitutes a ball joint which allows, before tightening the nut, an angular oscillation of the connecting slide in a

<Desc / Clms Page number 4>

 plane parallel to the securing rod and the threaded cylindrical portion of the anchoring element.

 Preferably, the four spherical surfaces are substantially concentric. This promotes a good mechanical rigidity of the assembled device and in place.

 Also preferably, the cross section of the first passage is oblong and elongate in the transverse direction parallel to the securing rod, and its elongation increases progressively from an intermediate transverse zone when approaching the lower entrance or entry upper, so that the connecting slider can oscillate around the anchoring element in a plane parallel to the fastening rod. Angular adjustments and oscillations are thus favored in the direction parallel to the securing rod, to facilitate installation, and these angular oscillations are limited in the transverse direction to ensure better rigidity.

 According to a first embodiment, the clamping means comprise: - a tightening screw, comprising a threaded rod and a head, - a clamping hole distinct from the first passage, provided in the bottom of the transverse groove of the slide and offset laterally relative to the first passage, - a cylindrical surface constituting a first edge of the transverse groove and shaped to receive the securing rod section, - an oblique bearing constituting an opposite edge of the transverse groove and inclined with respect to the axis of the clamping hole, - a jumper wedged in the transverse groove between the oblique seat and the securing rod and pushed towards the bottom of the transverse groove by the clamping screw.

 In a practical embodiment, the rider is pierced with a hole through which the clamping screw passes, so that the head of the clamping screw rests on the external face of the rider to push it towards the bottom of the transverse groove.

 According to a second embodiment, the connecting slider comprises a clamping part which surrounds a section of the

<Desc / Clms Page number 5>

 securing rod, and comprises a connecting part with two parallel branches which develop laterally from the two lips of a slot of the clamping part, the parallel branches each having a hole, the two holes forming the first passage and being traversed by the threaded cylindrical portion for clamping the parallel branches against each other during tightening of the clamping nut and to thereby tighten the securing rod.

 The apparatus may comprise, as anchoring element, one or more double threaded bone screws on either side of an intermediate stop collar, one or more hooks whose rear wall perpendicular to the axis of the threaded portion serves as a stop collar, and possibly shaped support plates to adapt to the particular morphology of certain areas of the spine.

 Other objects, features and advantages of the present invention will emerge from the following description of particular embodiments, with reference to the accompanying figures, in which: FIG. 1 is a perspective view of a bone screw that can be used anchoring element according to the invention, assembled to a slider and a securing rod according to a first embodiment; - Figure 2 is a cross-sectional view on a larger scale of the assembly of Figure 1; FIG. 3 is a perspective view of a laminar hook that can serve as an anchoring element according to the invention, assembled to a slider and to a securing rod according to the first embodiment; - Figure 4 is a sectional view in a plane parallel to the securing rod, showing the shape of the first slide passage, and illustrating the possibility of angular oscillation of the connecting slide on an anchor screw; - Figure 5 is a sectional view in a transverse plane perpendicular to the fastening rod, illustrating the angular retention of the connecting slider on an anchor screw; and

<Desc / Clms Page number 6>

 - Figure 6 illustrates a second embodiment of connecting slider, acting by pinching.

 The apparatus shown in the figures comprises anchoring elements such as bone screws 1 (FIGS. 1 and 2) or hooks 2 (FIG. 3), at least one securing rod 3, and connecting slides 4 between each anchoring element and the fastening rod 3.

 The fastening rods 3 of the apparatus according to the invention are, for example, smooth rods of circular section. The material and the section are chosen so as to obtain an optimum elasticity, adapted to the forces to be withstood during use, and so that the rod can be curved according to the desired shape for the part of the spine to be treated.

 Each anchoring element, bone screw 1, hook 2 or support plate, is in one piece with a threaded cylindrical portion 5 provided with an external thread 6, and comprises a stop collar 7 limiting the clamping a clamping nut 8 on this external thread 6.

 In the embodiment of FIGS. 1 and 2, the anchoring element is a double-threaded bone screw 1, the threaded cylindrical portion 5 with external threading 6 constituting the first threading, a second threaded coaxial portion 9, with the aid of FIG. opposite of the stop flange 7, constituting a second thread adapted to be screwed into the bone. The stop flange 7 constitutes an intermediate part of larger section separating the two threaded portions 5 and 9. The stop collar 7 advantageously comprises a peripheral surface 10 with six-sided facets, an abutment surface 11 connecting to the second threaded coaxial portion 9 and intended to bear against the vertebra bone, and an opposite bearing surface 12 connecting to the threaded cylindrical portion 5 and developing from its base 5a.

 The bearing surface 12 of the stop flange 7 is a convex spherical surface whose convexity is turned towards the threaded cylindrical portion 5, and which constitutes a male spherical bearing surface capable of engaging in a surface

<Desc / Clms Page number 7>

 corresponding lower spherical 13 of the connecting slide 4.

 In a known manner, the threaded cylindrical portion 5 can be extended by an excess coaxial threaded portion 5c, shown in FIGS. 3 to 5, and to which it is connected by an intermediate annular groove 5b constituting a rupture primer to facilitate cutting of the section. excessively after screwing a tightening nut 8 onto the threaded cylindrical portion 5. The annular groove 5b advantageously has a sawtooth section, the groove bottom being adjacent to the end of the threaded cylindrical portion 5.

 In the embodiment of FIG. 3, the anchoring element is a pedicular hook 2 intended to hook the pedicle of a vertebra. The hook 2 comprises a hook body 15, bent as shown in the figure, and a bearing surface 12 on which is connected the threaded cylindrical portion 5. As in the case of the pedicle screw of FIG. 12 is a male spherical surface.

 The connecting slider 4 comprises a first passage 16 shaped to be traversed by the threaded cylindrical portion 5 of an anchoring element 1 or 2, and has an upper transverse groove 17 shaped to receive a section of the fastening rod 3. Clamping means for selectively clamping or loosening the securing rod 3 in the transverse groove 17.

 The transverse groove 17 comprises a cylindrical bearing surface 18 which constitutes one of its edges and which is shaped to receive the securing rod section 3, for example by wrapping it around 120 as illustrated in FIGS. 2 and 4. Preferably, the cylindrical surface 18 comprises anti-slip reliefs 18a which effectively oppose any displacement of the securing rod 3 in the connecting slide 4 in translation as well as in rotation.

 The opposite edge of the transverse groove 17 is constituted by an oblique bearing surface 19 inclined so that the transverse groove 17 is flared upwards.

<Desc / Clms Page number 8>

 The connecting slide 4 comprises a tapped hole 20, distinct from the first passage 16, oriented along an axis II inclined with respect to the axis I of the first passage 16, and provided in the bottom of the transverse groove 17 of the slide. link 4.

 As illustrated in FIG. 2, a clamping screw 21 comprising a threaded rod 21a and a head 21b is screwed into the clamping hole 20.

 A rider 22 is wedged in the transverse groove 17 between the oblique seat 19 and the securing rod 3. The rider 22 is pushed towards the bottom of the transverse groove 17 by the clamping screw 21. For this, the rider 22 is pierced with a hole traversed by the clamping screw 21, so that the head 21b of the clamping screw 21 is supported on the outer face of the rider 22 to push it towards the bottom of the transverse groove 17. The rider 22 comprises a bearing face 22b which is slidingly bearing on the oblique bearing surface 19 of the connecting slide 4, and has an opposite thrust face 22c bearing on the securing rod 3 to ensure its locking in the transverse groove 17. The jumper 22 is retained on the clamping screw 21 by the engagement of a flange 21c in an annular groove 22a.

 The lower end of the first passage 16 is flared to form the lower spherical female surface 13 into which the male spherical bearing surface 12 of the stop flange 7 engages. The first passage 16 of the connecting slide 4 a in addition, a cross-section of appropriate shape so as to allow angular oscillation of the connecting slide 4 away from the axis I on the anchoring element 1 or 2 before clamping the clamping nut 8.

The oscillation is schematically illustrated by the double arrow 23 in FIG.

 An advantageous form of the first passage 16 of the connecting slide 4 is shown in FIGS. 4 and 5.

 FIG. 4 represents a partial section of a bone screw 1, with its threaded cylindrical portion 5, the stop flange 7 and its spherical bearing surface 12. The connecting slide 4 is engaged on the threaded cylindrical portion 5. The cut

<Desc / Clms Page number 9>

 is made in a plane parallel to the connecting rod, that is to say a plane perpendicular to the elongation of the connecting slide 4.

 FIG. 4 shows that, in this plane, the first passage 16 comprises a first lower inlet 16a flared to form the lower spherical surface 13 in which the support surface 12 of the stop collar 7 engages. The connecting slide 4 further comprises, around the upper entrance 16b of the first passage 16, an upper convex spherical surface 24. The clamping nut 8 has a concave lower spherical surface 8a, with the same curvature as the convex upper spherical surface 24, and adapted to directly receive said convex upper spherical surface 24 when tightening the clamping nut 8.

 Preferably, in the assembled position when the tightening nut 8 is tightened, the four successive spherical surfaces 12, 13, 24 and 8a are substantially concentric.

 The cross section of the first passage 16 is oblong and elongate in the direction parallel to the connecting rod, or direction of the plane of Figure 4. As seen in the figure, the elongation of the cross section, such as for example the distance d from the intermediate transverse zone 25 increases progressively from said intermediate transverse zone 25 when approaching the lower inlet 16a or the upper inlet 16b of the first passage 16. In the illustrated embodiment, in the vicinity of the upper inlet 16b, the elongation is little less than the external diameter of the connecting slide 4.

And the elongation becomes equal to the outer diameter of the connecting slide 4 in an entire area near the lower entrance 16a.

As a result, the connecting slide 4 can oscillate around the anchoring element 1 in the plane parallel to the securing rod, as can be seen in FIG. 4.

 On the other hand, in the perpendicular plane, as illustrated in FIG. 5, the internal diameter of the first passage 16 is only slightly greater than the external diameter of the threaded cylindrical portion 5 of the anchoring element 1, leaving only one

<Desc / Clms Page number 10>

 low deflection possible angular oscillation of the connecting slide 4 on the anchoring element 1 in this plane.

 In the second embodiment illustrated in FIG. 6, the connecting slide 4 comprises a clamping part 26 which surrounds a section of the securing rod, and comprises a connecting part 27 with two parallel branches 27a and 27b which develop laterally from the two lips of a slot 26a of the clamping portion 26. The parallel branches 27a and 27b each have a respective hole 27c and 27d. The two holes 27c and 27d form the first passage 16 and are traversed by the threaded cylindrical portion of the anchoring element to clamp against one another the parallel branches 27a and 27b during tightening of the clamping nut. , and to thereby tighten the securing rod engaged in the transverse hole 26b of the clamping portion 26.

 The apparatus of the invention allows the use of a rod or several rod elements, curvature appropriate to the vertebral region to be treated.

 The positioning of the connecting slides 4 on the connecting rod 3 is easy, since they can be threaded by each of the ends thereof, or adapted by lateral engagement, and they slide freely on the connecting rod 3 whatever its curvature, while being able to be inclined on the corresponding anchoring element 1 or 2.

 The principle of reduction of the deformed spine is three-dimensional. It is necessary to transform a scoliotic curve oriented in a plane close to the frontal plane into a curve of physiological pace located in the sagittal plane and presenting a kyphotic curvature, thoracic and lumbar lordotic normal.

 Firstly, the securing rod is given a shape close to the normal physiological curvature, and positioned in the sagittal plane of the patient, fixing its two ends by anchoring elements and slides properly tightened. The non-slip reliefs of the slides thus make it possible to block the rod very effectively, both in translation and especially in rotation. Anchors are positioned in or on the other intermediate vertebrae. The

<Desc / Clms Page number 11>

 anchors closest to the rod are engaged in the sliders and locked by also locking the rod in the sagittal plane and in rotation by tightening the clamping screw. The engagement of the furthest anchors located in the concavity of the curve is permitted by the length of the threaded cylindrical portion 5 of the anchoring elements. Once the end of the threaded cylindrical portion introduced into the passage of the connecting slide 4 itself fixed on the rod, the progressive tightening of the tightening nut 8 brings the anchor point closer to the fastening rod, realizing progressive reduction of vertebral curvature. If the elasticity of the spine is exhausted, the securing rod 3 is deformed, and provides a correction in an intermediate position of maximum reduction.

 The apparatus according to the invention thus makes it possible to search on the spot for each intermediate anchoring element, to introduce its threaded cylindrical part into the bore of a slider, and to fix it rigidly on the rod, in alignment with the upper and lower anchoring elements, to obtain the desired straightening of the vertebrae thus fitted.

 The placement of the apparatus forming the subject of the invention on the patient's spine can be performed both in the anterior position and in the posterior position, with respect to the spine.

 The establishment of the apparatus according to the invention can be carried out in a much shorter operating time than with the previously known devices, given the increased facility with which the surgeon can present and assemble the elements of the apparatus. to each other and to the spine.

 It will be understood that an apparatus according to the invention may comprise, depending on the spine treatment to be performed, screw anchors, or hook anchors, or plate anchors, or a combination of two or three of these types of anchors. anchoring which are thus independent of each other.

 The present invention is not limited to the embodiments which have been explicitly described, but it includes the various variants and generalizations thereof within the scope of the claims below.

Claims (8)

1-apparatus for treating the spine, comprising: - anchoring elements (1,2) in the vertebrae, each having a threaded cylindrical portion (5) on which a tightening nut (8) is screwed, and comprising a part anchoring device connected to the threaded cylindrical portion (5) by an intermediate stop collar (7), - at least one securing rod (3), - connection slides (4) for connecting anchoring elements ( 1.2) to the securing rod (3), the connecting slides (4) having a first passage (16) shaped to be traversed by the threaded cylindrical portion (5) of anchoring element to ensure their attachment to an anchoring element, the connecting slides comprising clamping means for selectively tightening or loosening the fastening rod (3) in the connecting slide (4), - the locking flange (7) having a surface of male spherical support (12) engaging in an inferior spherical surface corresponding female (13) around the lower inlet of the first passage (16) of the connecting slide (4), the first passage (16) of the connecting slide (4) having a diameter greater than the diameter of the cylindrical portion threaded anchoring element (5) to allow angular oscillation of the connecting slide (4) away from the axis (I) on the anchoring element before tightening the tightening nut (8). ), characterized in that the connecting slide comprises an upper spherical surface (24) convex around the upper entrance (16b) of the first passage (16) of the connecting slide (4), and in that the nut of clamping (8) has a corresponding concave lower spherical surface (8a) which directly receives said convex upper convex spherical surface (24).  2-spine treatment apparatus according to claim 1, characterized in that the four spherical surfaces (12,13, 24,8a) are substantially concentric.  3-spine treatment apparatus according to one of claims 1 or 2, characterized in that the section <Desc / Clms Page number 13>  cross section of the first passage (16) is oblong and elongated in the transverse direction parallel to the securing rod, and its elongation (d) increases progressively from an intermediate transverse zone (25) when approaching the lower entrance (16a ) or the upper inlet (16b), so that the connecting slider (4) can oscillate around the anchoring element (1) in a plane parallel to the securing rod.  4-apparatus for treating the spine according to any one of claims 1 to 3, characterized in that the clamping means comprise: - a clamping screw (21), comprising a threaded rod (21a) and a head (21b) - a clamping hole (20) distinct from the first passage (16), provided in the transverse groove bottom of the slide and offset laterally with respect to the first passage (16), - a cylindrical seat (18) constituting a first edge of the transverse groove (17) and shaped to receive the securing rod section (3), - an oblique bearing (19) forming an opposite edge of the transverse groove (17) and inclined with respect to the axis (II) of the clamping hole (20), - a rider (22) wedged in the transverse groove (17) between the oblique bearing (19) and the securing rod (3) and pushed towards the bottom of the transverse groove (17) by the clamping screw (21).  5-apparatus for treating the spine according to claim 4, characterized in that the jumper (22) is pierced with a hole through which the clamping screw (21) passes, so that the head (21b) of the clamping screw (21) is supported on the outer face of the rider (22) to push it towards the bottom of the transverse groove (17).  6-apparatus for treatment of the spine according to any one of claims 1 to 3, characterized in that the connecting slide (4) comprises a clamping portion (26) which surrounds a section of the connecting rod (3), and comprises a connecting portion (27) with two parallel branches (27a, 27b) which develop laterally from the two lips of a slot <Desc / Clms Page number 14>  (26a) of the clamping portion (26), the parallel legs (27a, 27b) each having a hole, the two holes (27c, 27d) forming the first passage (16) and being traversed by the threaded cylindrical portion (5). ) to clamp the parallel branches (27a, 27b) against each other when tightening the clamping nut (8) and thereby tighten the securing rod (3).  7-Apparatus according to any one of claims 1 to 6, characterized in that it comprises, as anchoring element, one or more bone screws (1) with double thread, the threaded cylindrical portion (5) of element anchoring device constituting the first thread, a second threaded coaxial portion (9), opposite the stop flange (7), constituting a second thread adapted to screw into the bone.  8-Apparatus according to any one of claims 1 to 7, characterized in that it comprises, as anchoring element, one or more hooks (2) in which the rear wall of the hooks, perpendicular to the axis of the threaded cylindrical part (5), serves as a stop flange.