Drilling device for forming a curved osseous channel within the body of a vertebra
The drilling device for forming an osseous channel ( 2 ) with a curved profile ( 2 b ) via a straight cannula ( 6 ) previously fixed in the body of a vertebra ( 3 ) with a cortical plateau ( 4 ) of a spinal segment (Sr) of a vertebral column (Cv) includes a guide pin ( 8 ) which is provided from a guide pin kit and has at one of its ends a curved profile ( 8 a ) of which the radius of curvature R is less than 20 millimeters, and a sharpened tip ( 8 b ) arranged in a direction defined by an angle Y which is less than 90 degrees to the longitudinal axis of said pin, the profile of said guide pin ( 8 ) making it possible to define, after insertion thereof into the body of the vertebra ( 3 ), two contact points a and b ensuring the guidance of the free end of an articulated drill bit ( 10 ) so as to position said free end in a direction substantially perpendicular to that of the cortical plateau ( 4 ) of the vertebra ( 3 ) to be drilled.
1. A drilling system for forming an osseous channel with a curved profile via a straight cannula previously fixed in a body of a vertebra with a cortical plateau of a spinal segment of a vertebral column, the drilling system comprising:
an articulated drill bit; and
a guide pin which is provided from a guide pin kit and has at one end i) a curved profile of which a radius of curvature is less than 20 millimeters, and ii) a sharpened tip arranged in a direction defined by an angle which is less than 90 degrees to a longitudinal axis of the pin, the profile of the guide pin defining, after insertion thereof into the body of the vertebra, first and second contact points ensuring guidance of a free end of the articulated drill bit, the guide pin being configured to receive the articulated drill bit over an outer surface of the guide pin, and to guide the articulated drill bit and cause the articulated drill bit to deform,
wherein the articulated drill bit is configured to deform at the free end thereof in accordance with the radius of curvature of the guide pin as the articulated drill bit is guided along the guide pin,
the guide pin is configured to position the free end of the articulated drill bit in a direction substantially perpendicular to that of the cortical plateau of the vertebra to be drilled,
the articulated drill bit is formed of a metal cylindrical tube comprising
a grasping grip at one end thereof, and
a profile at the other end thereof, the other end being cropped, the profile ensuring deformation and articulation of the other end in a curved shape, so as to define a cutting end comprising
a first set of teeth arranged over a periphery of the tube, and
a second set of teeth arranged at the other end of the metal tube and a protective sheath arranged in an inner portion of the metal tube, the protective sheath being made of a resilient material to internally smooth irregularities and gaps in the free end arising from the profile.
2. The drilling system according to claim 1 , wherein the first contact point is defined by a tangent to the outer profile of the radius of curvature of the guide pin which is perpendicular to the cortical plateau of the vertebra, and the second contact point is defined by the free end of the articulated drill bit which rests against an inner profile of the sharpened tip of the guide pin arranged within a depth of the cortical plate of the vertebra.
3. The drilling system according to claim 1 , wherein the guide pin is made of a material which is both hard-wearing and flexible.
4. The drilling system according to claim 1 , wherein the guide pin has an outer diameter which is less than 3 millimeters.
5. The drilling system according to claim 4 , wherein the guide pin has an outer diameter which is between 1.4 millimeters and 2 millimeters.
6. The drilling system according to claim 1 , wherein the curved profile has a radius of curvature which is between 10 millimeters and 20 millimeters.
7. The drilling system according to claim 1 , wherein the angle of the sharpened tip is between 70 and 85 degrees with respect to the longitudinal axis of the guide pin.
8. The drilling system according to claim 1 , wherein the guide pin comprises a straight longitudinal portion having a flattened part which cooperates with a complementary profile formed in a pin holder, ensuring i) that the guide pin is blocked against rotation inside the pin holder, and ii) that the guide pin is rigidified over the straight longitudinal portion during insertion of the guide pin and of the pin holder through the straight cannula previously fixed in the body of the vertebra.
9. The drilling system according to claim 8 , wherein the guide pin comprises a notch formed in the straight longitudinal portion beside the flattened part at the end opposite the end with the curved profile of the guide pin, the notch cooperating with a tensioning screw which is guided in a grasping grip of the pin holder to block movement in translation of the guide pin in the pin holder.
10. The drilling system according to claim 8 , wherein the pin holder is formed of a metal cylindrical tube formed in one piece at one end thereof with a grasping grip equipped with a tensioning screw and a hollow cylindrical sleeve having, over an outer profile thereof, a fast thread adapted to screw in a plug to block the movement in translation of the guide pin relative to the pin holder.
11. The drilling system according to claim 1 , wherein the grasping grip comprises a hollow cylindrical sleeve in an extension of the metal tube, the sleeve having, over an outer profile thereof, a fast thread to insert and fix a centering sheath inside the metal tube.
12. The drilling system according to claim 11 , wherein the centering sheath is formed of a cylindrical tube made of a resilient material and formed in one piece at one end thereof with a grasping head comprising
an inner threaded bore for cooperation with the sleeve of the grip of the articulated drill bit for immobilization of the sleeve on the articulated drill bit, and
a blocking device opposite the inner threaded bore blocking movement in translation of the cylindrical tube inside grasping head of the centering sheath.
13. The drilling system according to claim 11 , wherein the articulated drill bit comprises a locking device arranged on the metal tube and beneath the grasping grip so as to immobilize the drill by a retaining element and a fixing nut on the straight cannula previously fixed in the body of the vertebra.
14. The drilling system according to claim 13 , wherein the locking device is formed of a retaining element comprising a cylindrical head formed in one piece with a sleeve having a cylindrical outer profile equipped with a thread extending via a split, conical outer profile.
15. The drilling system according to claim 14 , wherein the retaining element is perforated through a middle thereof by a through-bore comprising an inner thread at the cylindrical head cooperating with a threaded profile of the straight cannula in order to immobilize the retaining element over the cannula.
16. The drilling system according to claim 14 , wherein the locking device is formed of a fixing nut comprising
a first threaded bore in an inner portion of the fixing nut, the first threaded bore cooperating with the thread formed in the cylindrical portion of the sleeve of the retaining element, and
a second inner bore which is coaxial with the first inner bore and has a conical inclination profile complementary to the conical outer profile of the sleeve.
17. The drilling system according to claim 1 , wherein the protective sheath ensures a significant coefficient of slip for sliding of the guide pin and/or of a centering sheath during drilling of the osseous channel with the curved profile.
18. The drilling system according to claim 1 , wherein the profile of the metal cylindrical tube is formed of a sequence of alternately concave and convex loops ensuring deformation and articulation of the end of the articulated drill bit in a curved shape.
19. The drilling system according to claim 1 , wherein a cutting edge of each tooth of the first set of teeth is slightly inclined relative to the longitudinal axis of the articulated drill bit.
20. The drilling system according to claim 1 , wherein a cutting edge of each tooth of the second set of teeth is sharply inclined so as to intersect the longitudinal axis of the articulated drill bit.
21. The drilling system according to claim 1 , wherein the articulated drill bit comprises safety means ensuring recovery of the cutting end when the articulated drill bit breaks.
22. The drilling system according to claim 21 , wherein the safety means are formed by a resilient thread or wire arranged inside the metal tube and between an inner face of the tube and the protective sheath in such a way that each end of said resilient thread cooperates with a grasping head of the centering sheath.
23. The drilling system according to claim 21 , wherein the safety means are formed by a resilient thread or wire arranged inside the metal tube and between the protective sheath, which is formed in one piece with an inner face of the tube, and an outer face of a centering sheath in such a way that each end of the resilient thread cooperates with a grasping head of the centering sheath.
24. The drilling system according to claim 23 , wherein the ends of the resilient safety thread respectively comprise a stop arranged in a seat of similar profile formed in the grasping head of the centering sheath.