INSTRUMENTS FOR SPINAL CORD, PARTICULAR PORTE RODS
DESCRIPTIVE ORIA
The present invention relates to spinal elements, especially for essentially smooth connecting rods comprising a bone anchoring member having a separate anchoring part of a threaded screw protruding head, associated with a nut, by a body intermediate polygonal section, allowing the tightening on the cover, where the anchoring part is a screw, and forming a support on its upper part, and a receiver and tuning assembly adapted to receive said rod comprising a member forming a clamp that has two branches joined by a connection area, the branches being provided with aligned holes through which the head of the threaded screw can pass to the support and clamp delimiting a passage between the branches. It also refers to a receiver and tuning assembly adapted in particular to connect a rod to an anchoring member. Patent FR-2 657 775 discloses pair-of-spine instruments of the rod type adapted to reduce and contain the spine, comprising a set screw with a cylindrical threaded screw head which receives a portion engaged on a threaded screw head allowing to lock a connecting rod between a supporting portion of said part and the conical portion of a threaded engagement on the head of the threaded screw. This system locks the rod with respect to the screws, but the orientation of the rod with respect to the screw, which is orthogonal to the screw, is the same for all the screws and can not be modified. French patent 2 693 365 discloses rod-type spine instruments that allow a certain degree of adjustment of the angle between the respective axes of the rod and the screw in a particular plane (ie, without this plane being able to pivot about of the shaft of the rod), and locking the rod to the screw in this position. This device comprises a captive screw with a threaded screw head having an intermediate body, a receiver and tang assembly engaged in said threaded screw head by means of an oblong hole and provided with a housing for receiving the rod laterally from the screw and resting on the upper surface of the spherical shape of the intermediate body. The frustoconical lower face of the nut screwed into the head of the threaded screw comes into contact, in an area opposite the area of contact with the rod, with a corresponding frustoconical surface in said receiver and locking assembly. However, it is convenient to have a receiver and locking assembly that allows the angle of the rod with respect to the screw to be increased and thus reduce even more the curvature of the rods and consequently the tension in the arrangement that joins the different primary screws. , while significantly improving the binding and therefore the rigidity of the assembly. US 5 222 954 discloses backbone instruments for connecting rods having a separate anchoring part of a protruding threaded screw head, associated with a nut, by means of an intermediate body of polygonal section forming a support on its upper part and a receiving and a sanding part 26 in the form of a hole 28 that permits engagement of a protruding threaded screw head 16 and a passage 34, the axis of which is perpendicular to the axis of the hole 28 adapted to receive the connecting rod 40. Note that this device does not allow the connecting rod to be oriented in all directions, which is possible with the device of the present invention. Likewise, EP-A-585 518 and US 5 352 226 do not allow the connecting rod to be oriented in all directions. US 4 771 767 requires the use of a threaded screw rod, which has the disadvantage that it can not be modified to adapt it to the deformation or anatomy of the spine. The object of the present invention is, therefore, to propose spinal instruments by emphasizing the improved locking of the connecting rod, while allowing the rod to be oriented in all directions within a certain angle with respect to the neutral axis. The invention is characterized in that said passage defines a cavity, and in which a compressible ring housed in the cavity is provided and having a central passage for receiving the connecting rod, the cavi-ring assembly forming a ball joint, so that the fixing of the branches by means of the nut engaged on the head of the threaded screw locks the ring and the connecting rod in the angular-required position. The spinal instruments are made of a biocompatible material for surgical implantation, such as stainless steel or a titanium-based alloy. In a manner that is known per se, the bone anchoring members may be captive screws or hooks. Other anchoring means may be used in the context of the present invention. The "threaded screw rod" is an essentially smooth member, that is, it can freely slide through the ring before it is clamped. The rod can be a smooth connecting member of sufficient diameter to resist the stresses and loads of the spine, the smooth surface having the advantage that it can be modified to reach a certain degree of curvature adapting to the deformation or anatomy of the spine . The rod can also comprise flexible braided cylindrical wires. To facilitate the work of the surgeon, it is advantageous to limit the angle of the axis of the ring with respect to the axis of the cavity at rest. This facilitates the insertion of the rod because the passage is always accessible. An advantageous solution is to provide the ring with one or more supports limiting its rotation. In order to improve the bending of the ring, it is advantageous to provide suitable additional means for accentuating the pressure applied at certain points on the ring by the cavity. Therefore, the cavity is preferably provided with at least one sharp edge adapted to load the ring. This can be a slot in the cavity by supplying two other sharp edges that rest on the ring in the locked position. The clamping feature can also be improved by creasing the surface of the cavity and the surface of the ring at least partially by sandblasting or machining. To further improve the locking, the nut has a convex spherical lower face that fits a spherical concave area around the hole on the corresponding branch. The ring is advantageously annular, preferably spherical, and has a convex outer face the diameter of which is between that of a depressed central portion and that of the lateral portions of the cavity. The compression capacity of the ring is preferentially secured by a through notch. Flexibility can be further improved by a groove symmetrically opposite the notch. Other features and advantages will arise from the following description of a modality of the device of the invention given by way of example and with reference to the accompanying drawings, in which: Figure 1 is a schematic perspective view of a device of the invention; invention; Figure 2 is a perspective view of an assembled device of the invention; Figure 3 is a top view of a portion of the device at rest; Figure 4 is a sectional view taken along the line ITT-TTT of the portion shown in Figure 3; Figure 5 is a sectional view taken along line 00 of the portion shown in Figures 3 and 4; Figure 6 is a terminal view of another portion of the device; Figure 7 is a middle sectional view of the portion of Figure 6 taken along the line CC; Figure 8 is a partial sectional view of the implant when assembled and locked; Figure 9 is a top view of a variant of the portion of Figures 3 to 5; and Figure 10 is a partial sectional view of the portion of Figure 9. Referring to Figure 1, a captive screw 1 has a lower portion or threaded screw point 2 adapted to penetrate a vertebral body, and an upper portion or screw head 3, in which a nut 5 can be screwed. The point 2 and the head 3 are separated by an intermediate body 4, of hexagonal section in the mode shown, allowing the point 2 to be screwed using a wrench nuts The head of the threaded screw 3 is separated from the body
4 by a smooth portion 6, the diameter of which corresponds to the bottom diameter of the threaded screw of the head 3, for example. The hexagonal body 4 has a flat upper surface 7 forming a support. Figures 3, 4 and 5 show a part 9 forming a clamp which is a portion of a receiver and lock-8 assembly of the device. Clamp 9 has lower and upper branches 10 and 11 and a connecting area 12 joining these branches. The outer face of the lower branch 10 has a straight passage 13 delimiting a depressed lower external area 15. The outer face of the upper branch 11 has a curved edge 14 delimiting a depressed concave spherical area 16 centered in the hole 18. L branches 10 and 11 have coaxial holes 17 and 18 of appropriate diameter aligned to allow insertion of the head of the threaded screw 3 to the support 7, a vertical face 19 of the intermediate body 4 then resting on the lower passage 13 to prevent any relative rotation of the grub screw 1 and clamp 9. The nut 5 has a convex spherical bottom face 31 which conforms to the convex area 16. The clamp delimits an interior cavity-20 open on both sides of the clamp. Said cavity has a cylindrical central portion 21 flanked on each side by two cylindrical lateral portions 22 with a smaller radius, the three portions being coaxial. The steps due to the greater radius of the central portion provide two circular sharp edges 23. The outer edge of each cylindrical lateral portion 23 preferably has a small slot 33 to facilitate the insertion of the rod and not prevent its freedom of angular movement. In relation to figures 6 to 8, the cavity receives a ring 24, the length of which is preferably smaller than that of the cavity and which is provided with a straight through notch 25. The ring 24 receives in its interior passage 26 a cylindrical connecting rod 27. The outer face of the ring has a central spherical widening 28, the upper part of which is inserted in the loose position of the clamp in the cavity delimited by the central portion 21, said widening being extended on each side by two externally cylindrical portions 29 forming annular supports so that, in the unlocked position, the angle of the ring axis is limited by the annular supports resting on the cylindrical walls 22 of the cavity. A groove 30 in the symmetrical widening to the groove 24 improves the flexibility of the ring. Note here that the diameter of the spherical widening 28 of the ring is chosen to be greater than the diameter of the portions 2? of the cavity, but smaller than the diameter of the central portion 21. In this way, at rest, the ring is caught with play in the cavity. Note also that the limitation of the angular movement of the ring by the supports 29 ensures that the passage 26 in the ring is correctly aligned with the entrance of the cavity 20 of the clamp. The possible rotation angle of the rod around the axis of the cylindrical cavity defined in this way is preferably around 15 °. The screwing of the nut 5 on the head of the threaded screw holds the branches 10, 11 of the armrest that compresses the ring 24. Due to the flexibility of the ring, imparted by the notch 25 and the slot 30, the ring in turn attaches to the connecting rod, which is firmly locked in the position chosen by the physician. Note here that the fact that the clamp 9 rests on the ring 24 along two sharp edges 23, ensures a lock of excellent quality. The quality of the bending can be further improved by at least partially creasing the surface of the ring and the passage through it, as well as the connecting rod if ip
it is appropriate, for example, by blowing it out with sand or sand. In a variant of the part of figures 3 to 5 shown in figures 9 and 10, the holes 1 7, 18 of the branches 10, 11 are "oblong" in the longitudinal direction of the branches of the device, fidems, the external face of the upper branch-11 has a straight passage 14 'delimiting a depressed area 32 A flat nut (not shown) is partially housed in the depressed area. The passage 14 'is a sufficient distance from the nut to allow it to be turned with a wrench. This variant allows the distance between the axis of the connecting rod and that of the head of the threaded screw to be varied, allowing adaptation to the different morphotypes found and, in conjunction with the orientation possibilities, the limitation of the degree of curvature of the rods. In another variant, not shown, the clamp 9 is provided during part of its extension, with notched half 1, lower and upper to improve its deformability the aesthetic. Finally, the invention is not limited to the modalities described above but, on the contrary, covers all variants thereof. In particular, these spinal instruments can be associated with plate type instruments, as described in patent FR-B-2 657 775.