FR2871362A1 - PIN FOR ATTACHING A SUPPORT ON A BONE - Google Patents

Abstract

Pin for fixing a support on a bone, in particular intended for fixing a support for an infrared reflector of a computer assistance system for bone and joint surgery or other techniques, the pin (10) comprising a support part (20) intended to receive the support and an anchoring part (22) intended to be introduced, through an insertion end (18), into the bone. According to the invention, the anchoring part (22) is shaped to prevent any rotation of the pin (10) about its axis after the anchoring portion (22) is forcibly introduced into an upper cortex of the bone.

Description

The invention relates to a pin for fixing a support on a bone,

  particularly intended for fixing a support of an infrared reflector of a computer assistance system to osteo-articular surgery. The invention also relates to a support device comprising such a pin.

  In the case of surgery on a knee, for example, a computer assistance system can be implemented to allow the surgeon to visualize, in real time, on a computer screen, three-dimensional images of the knee on which he is preparing to intervene. This system also allows him to navigate between different locations of the knee, that is to say, to visualize, in the form of a continuous film, a virtual displacement between these places.

  Conventionally, in a first step, landmarks are fixed on the knee and a multitude of knee points are spotted in space relative to these landmarks. The assistance system then determines in real time the relative position of these marks relative to each other.

  In case of displacement of a marker relative to another following a movement of the knee, the computer is able, from the sole knowledge of the new relative positions of the marks, to calculate the new positions of said knee points relative to to landmarks. The new positions of said knee points are therefore calculated without the need to make new measurements of their positions. The system allows real-time navigation, regardless of knee configuration.

  If a marker moves relative to the knee, the calculated positions of the knee points no longer correspond to their actual positions. The consequences can be dramatic, especially if navigation is used to drive a surgical instrument. The quality of the fixation of the marks is therefore paramount, a displacement greater than 0.1 mm being considered as unacceptable.

  The markers may be infrared reflectors carried by supports, in English rigid body, themselves fixed on pins screwed into a knee bone.

  Depending on the type of three-dimensional tracking system used in computer-assisted surgery systems, infrared reflectors may be combinations of disks, spheres or bands, but they may also be replaced by infrared emitters or by transmitters or transmitters. ultrasonic receivers, or magnetic transmitters or receivers, or inertial sensors.

  Conventionally, a pin, or nail, has the general shape of a rigid rod. There is a support portion for receiving the support and an anchoring portion for attachment to the bone. The anchoring portion is provided with a thread.

  A bone comprises a rigid envelope: cortical bone called cortical and a spongy central part: spongy bone or bone marrow, contained in the cortex. To ensure a satisfactory immobilization of the spindle, the surgeon must pierce the bone from one side to the other, that is to say successively a first part of the cortical, called the superior cortical, the marrow, and a second part of the cortex. , called lower cortical, then screw the anchor portion of the spindle in the bores thus formed. To limit the possibilities of rotation of the spindle about its axis, it then comes to tighten a nut against the superior cortex.

  Fixing the spindle by thread is a long operation. It does not guarantee a perfect locking in rotation and, because of drilling through the bone, leads to the weakening of the bone. The pins are also expensive to manufacture.

  To limit the possibilities of rotation of the reflector support, it is also known to fix the reflector support to the bone by means of several threaded pins secured to each other by means of a stirrup. The operation is however long to implement and also leads to the weakening of the bone. In addition, the multiplication of the pins leads to a multiplication of percutaneous incisions or to their enlargement. The implantation area must also be extended. In some procedures, such as for the reconstruction of the anterior cruciate ligament, multiple pins can not be positioned optimally.

  There is therefore a need for means for fixing a support on a bone which are quick to implement, inexpensive to manufacture, less invasive than the pins according to the prior art and able to avoid any rotation of the support.

  The object of the present invention is to meet this need.

  According to the invention, this object is achieved by means of a pin for fixing a support on a bone, in particular a pin for fixing a support for an infrared reflector of an assistance system. computer to osteoarticular surgery, said pin comprising a support portion for receiving said support and an anchoring portion to be introduced, by an insertion end, into said bone. According to the invention, said anchoring portion is shaped to prevent any rotation of said pin about its axis after force introduction of said anchoring portion into said bone.

  The anchoring portion thus defined can therefore take a wide variety of shapes, excluding the forms of revolution around the axis of the spindle, possibly provided with a thread as in the prior art.

  As will be seen in more detail in the following description, the introduction of the pin into the bone in force can be performed by percussion by means of a mass and is therefore particularly fast.

  The rotational locking results from the conformation of the anchoring portion which, when it is forced into the bone, engages the bone, in particular with the upper cortex. Because of the effectiveness of this blocking, it is not essential that the pin according to the invention passes through the lower cortical. Advantageously, the weakening of the bone resulting from the establishment of the spindle is thus limited.

  The rotational locking does not require any particular operation or additional member such as a nut. It is so fast and efficient.

  The spindle according to the invention still has the following preferred features.

  Said anchoring portion has at least one longitudinal edge. Advantageously, this edge facilitates the introduction of the spindle force.

  Said anchoring portion has a triangular cross section, regardless of the cross sectional plane considered. Advantageously, a triangular section is particularly adapted to prevent rotation of the spindle about its axis.

  The introduction end has the shape of a tip. Advantageously, the tip facilitates the introduction of the pin into force and / or a depression of the insertion end in the lower cortical bone.

  Said anchoring portion is arranged such that, in a service position in which said anchoring portion is immobilized in rotation by the upper cortex of said bone, said insertion end is driven into the lower cortex of said bone. This depression of the insertion end limits the bending of the pin around its points of contact with the upper cortex. Advantageously, the immobilization of the support relative to the bone is improved. Said insertion end is shaped to pierce a hole in said bone by rotation of said pin about its axis, the diameter of said hole being determined to prevent introduction of said anchoring portion without passing force.

  The invention also relates to a support device, in particular for an infrared reflector of a computer assistance system for osteoarticular surgery, which is remarkable in that it comprises a pin according to the invention.

  Preferably, the support device according to the invention comprises a slider slidably mounted on said support portion and locked in rotation around said support portion in complementary form with said support portion.

  More preferably, it comprises a plate mounted to rotate in an axis substantially perpendicular to the axis of said support portion and locking means in position of said plate on said slide.

  The invention finally relates to a method for fixing a support on a bone, in particular a support for an infrared reflector of a computer assistance system for osteo-articular surgery, which is remarkable in that it comprises a step of driving force into said bone, a fixing pin according to the invention.

  The method according to the invention also has the following preferred characteristics: Prior to said depression, a hole is drilled in the upper cortex of said bone at the location where said depression is to be made, the diameter of said hole being determined to prevent an introduction. said anchoring portion without passing force. Advantageously, the risk of rupture of the bone during the driving force is decreased.

  In one variant of the invention, said hole is pierced by means of said spindle, said spindle is held in said hole after piercing said hole, and said anchoring portion is then forced into said upper cortex. Advantageously, no specific tools are therefore necessary. Advantageously, the surgeon does not need to find the hole to introduce the pin.

  Forcing said pin into said upper cortex until penetration of said insertion end into the lower cortex of said bone. Advantageously, the holding in position of the spindle is improved. Preferably, said penetration is limited so that said pin does not pass through the lower cortical bone. The weakening of the bone is advantageously reduced.

  Other features and advantages of the present invention will appear on reading the following description and on examining the appended drawing in which FIGS. 1A and 1B show in perspective and in cross-section along the sectional plane AA shown in FIG. Figure 1A, respectively, a first embodiment of a pin according to the invention; FIGS. 2A, 2B and 2C show in perspective and in cross-section along the sectional planes A'A 'and B'B' shown in FIG. 2A, respectively, a second embodiment of a spindle according to the invention; Figure 3 shows a pin according to the first embodiment in a service position; FIG. 4 represents a detailed view of a support device according to the invention.

  In the various figures, identical references are used to designate identical or similar members. A prime sign has however been added to the references of the second embodiment.

  Reference is now made to Figures 1A-1B. Figure 1A shows a pin 10 of axis D, made of a rigid material compatible with penetration into the human body, for example aluminum, titanium or stainless steel. Pin 10 could also be made, in whole or in part, of a rigid plastic material, possibly armed at its center with a metal core. The pin 10 has a body 14, and at the ends of the body 14, a substantially cylindrical head 16 and a tapered insertion end, or tip 18.

  The body 14 is in the form of a straight rod with three substantially plane lateral faces 14a, 14b and 14c delimited by longitudinal edges 19a, 19b and 19c.

  By longitudinal edge is meant an edge extending in a plane containing the axis D of the spindle.

  The section of the body 14 is triangular isosceles (see Figure 1B) and substantially constant over the entire length L of the body 14.

  Preferably, the length of the body 14 L is about 90 mm. The length of the tip 18 is about 20 mm.

  Preferably, the width I of a face 14a-c is less than 10 mm, preferably less than 7 mm, more preferably about 5 to 6 mm.

  From the functional point of view, there is a support portion 20 and an anchoring portion 22.

  The support portion 20 is constituted by an upper portion of the body 14. It is intended to serve as sliding rail to a slide 24 (see FIG. 4) and to allow it to be immobilized on the spindle 10.

  As shown in FIG. 4, the support portion 20 and the slider 24 are shaped to prevent any rotation of the slider 24 around the support portion 20, preferably by complementarity of the light shapes of the slider 24 and the portion of the slider 24. support 20.

  The immobilization of the slider 24 is ensured by the support, on the face 14a of the body 14, of the tip of a screw 26 screwed into a threaded bore passing through a wall 28 of the slider 24. A plate 30 is provided to fix a reflector reinforcement 32 on the slide 24. The angular position of the plate 30 about an axis F substantially perpendicular to the axis D of the pin 10 can be modified by sliding, in two buttonholes 40 and 42 formed in the plate 30 and extending along the same circle, two screws 36 and 38 screwed into the slider 24. The screws 36 and 38 thus selectively allow the plate 30 to be released or immobilized on the slider 24.

  Preferably, the plate 30 is further shaped so that, by tightening the screws 36 and 38, the plate 30 presses the reflector armature 32 against the slide 24 and immobilizes it. The position of the reflector armature 32 with respect to the plate 30 and the slide 24 can thus advantageously be modified at will, by simply loosening the screws 36 and 38, changing the position of the armature of the reflector 32 and tightening the screws 36 and 38.

  The anchoring portion 22 comprises a lower portion 40 of the body 14, of triangular section, intended to come into contact with the upper cortex S of the bone, and the tip 18, intended to be driven into the lower cortical 1 of the bone, preferably without passing through it, as shown in FIG. 3. The anchoring portion 22 makes it possible to secure the pin 10 on the bone in a service position, as represented in FIG. 3, in which the pin 10 is perfectly immobilized relative to the bone.

  According to the invention, the anchoring portion 22 is shaped to prevent any rotation of the pin 10 about its axis D after the anchoring portion 22 has been forced into the upper cortical bone S (see Figure 3).

  To set up the pin 10, the surgeon first pierces a hole T in the upper cortex S where he plans to fix the pin 10, for example by means of a drill with a suitable forest. The diameter d of the hole, preferably about 3.5 mm, is determined not to allow the free passage of the anchor portion 22, that is to say that the depression of the anchoring portion 22 in this hole implies a passage in force.

  It then forces the pin 10 into the hole T, for example by striking the head 16 by means of a mass, until the tip 18 comes into contact with the lower cortex S of the bone. It then slightly strikes the pin 10 so as to make the tip 18 penetrate the lower cortical S, preferably avoiding that the tip 18 passes through the lower cortical S. The embrittlement of the bone is thus advantageously limited.

  In this position, called the operating position, the pin 10 is perfectly immobilized in rotation about the axis D by the close contact of the faces 14a-c of the anchoring portion 22 on the upper cortex S. The pin 10 is in further perfectly immobilized in translation along the axis D by the close contact of the faces 14a-c of the anchoring portion 22 on the upper cortical S and, towards the lower cortical I, by the abutment of the tip 18 on the cortex lower I. The thickness E of the area of contact with the upper cortex S and the depression of the tip 18 in the lower cortical 1 finally prevent any radial pivoting of the pin 10.

  Figures 2A-C show the preferred embodiment of the invention.

  The tip 18 ', preferably of a length of about 8 mm, is shaped to allow the hole T to be pierced. The tip 18' joins a cylindrical portion 42 with a diameter d of approximately 3.5 mm and a length of about 12 mm. A transition portion 44 provides a progressive widening of the outer surface of the pin 10 between the cylindrical portion 42 and the body 14 '.

  Preferably, the pin 10 'is not terminated by a cylindrical head and its end 16' opposite the tip 18 'is shaped to be fixed on the mandrel of a drill.

  To set up the spindle 10 ', the surgeon first fixes the end 16' of the spindle 10 'on a drill, then, by means of the spike 18', pierces a hole T in the upper cortical S to the spine. where he plans to fix pin 10 '. Advantageously, no specific drill is necessary. Once the upper cortical S breakthrough, the surgeon does not extract the 10 'pin from the T hole, but the drill's disassembly. The cylindrical portion 42 or the transition portion 44 is then in contact with the edge of the hole T and the pin 10 'could be extracted without difficulty. Advantageously, the pin 10 'is already in position to be fixed on the bone. The surgeon does not have to look for the hole he has just pierced to insert the pin 10 'and can immediately force the pin.

  The surgeon then proceeds as with the pin 10. He pushes the pin 10 'into the hole T of the upper cortical S until the tip 18' is inserted into the lower cortex. In less than a quarter of an hour, the pin 10 'can be put in place.

  As is clear now, the invention provides a means of fixing a support on a bone which is both quick to implement, inexpensive to manufacture, requiring only the drilling of a hole through a hole. only cortical. The presence of the longitudinal edges 19a, 19b and 19c makes it possible to effectively prevent any rotation of the spindle about its axis. Advantageously, a single pin makes it possible to immobilize the support with great rigidity relative to the bone. An incision of 2 to 3 mm is advantageously sufficient for the establishment of the spindle according to the invention.

  The present invention is however not limited to the embodiments described and shown, provided by way of illustrative and non-limiting examples.

  The anchoring portion is not necessarily of constant cross section. In particular, the anchoring part may flare towards the spindle head, which, for the same diameter of the hole T, advantageously allows a more or less rigid attachment according to the greater or smaller depression of the spindle in the spindle. 'bone.

  The cross section of the anchoring portion is not necessarily triangular, although this embodiment is preferred because it provides a very good rotational locking while preventing the anchor portion from overflowing the hole cylindrical T made to avoid weakening the bone.

  Preferably, the anchoring portion has a plurality of flat faces, interconnected by longitudinal edges. Depending on the types of bone, and to further reduce the risk of weakening of the bone, the section of the anchoring portion may thus have a shape closer to the circle, for example square, pentagonal, hexagonal, pentagonal, or more generally any polygonal shape, regular or not. The section of the anchoring portion can still have a star shape with any number of branches.

  The flatness of the faces is not limiting, even if flat faces are preferred. The faces could thus have asperities or, preferably, longitudinal grooves.

  The longitudinal edges are preferably sharp so as to facilitate forcing into the cortex.

  The presence of longitudinal edges improves the locking in rotation, but is not limiting. Any form of the anchoring portion allowing a force sink into the upper cortex, then, as a result, a locking of the rotation of the spindle about its axis, is possible. The anchoring portion could thus have, for example, an elliptical section which, although less effective than a triangular section, is within the scope of the present invention.

  The sections of the support and anchoring portions have the particular function of preventing rotation of the slider relative to the spindle and the spindle relative to the bone, respectively. The sections of the support and anchoring portions could be different from each other.

  Preferably, however, the support and anchoring portions are aligned axially and angularly around the axis D. Preferably, as for the pins 10 and 10 ', there is no discontinuity or slope failure between the support and anchoring portions, these body-forming portions having no physical limit to distinguish the support and anchoring portions. Thus, the pins can advantageously be attached to bones of various diameters.

  To reduce manufacturing costs, it is advantageous for the support and anchoring portions to have identical and constant sections along the entire length of the spindle body.

  The depression of the tip of the pin in the lower cortex is not essential to the implementation of the invention, a force sink through the single upper cortex already allowing a very satisfactory immobilization of the pin on the bone.

  Finally, the invention applies to any system in which it is necessary to locate the movement of a bone with great precision, that is to say not only to the osteo-articular surgery, but also to surgery maxillofacial, neurosurgery (fixation of the skull), ENT, spine surgery, or rheumatology. With the aid of equivalent systems, but of small dimensions, the invention can also be applied to very light procedures making it possible to carry out a diagnosis such as measuring the relative movements of the bones of a joint or to make a percutaneous gesture or minimally invasive.

Claims (9)

  1. Pin for fixing a support on a bone, in particular for attaching a support of an infrared reflector of a computer assistance system to osteo-articular surgery and other fixation techniques, said pin ( 10, 10 ') having a support portion (20) for receiving said support and an anchoring portion (22) to be introduced through an insertion end (18, 18') into said bone, characterized in that said anchoring portion (22) is shaped to prevent any rotation of said pin (10, 10 ') about its axis after force introduction of said anchoring portion (22) into said bone.   2. Fixing pin according to claim 1, characterized in that said anchoring portion (22) comprises at least one longitudinal edge (19a, 19b, 19c).   3. Fixing pin according to any one of claims 1 and 2, characterized in that said anchoring portion (22) has a triangular cross section, regardless of the cross sectional plane considered.   4. Fixing pin according to any one of the preceding claims, characterized in that said insertion end (18, 18 ') has the shape of a tip.   Fastening pin according to one of the preceding claims, characterized in that said anchoring part (22) is arranged in such a way that in a service position in which said anchoring part (22) is immobilized in rotation by the upper cortical (S) of said bone, said insertion end (18, 18 ') is pressed into the lower cortical (I) of said bone.   6. Fixing pin according to any one of the preceding claims, characterized in that said insertion end (18, 18 ') is shaped to pierce a hole (T) in said bone (S) by rotation of said pin ( 10, 10 ') about its axis (D), the diameter (d) of said hole (T) being determined to prevent introduction of said anchoring portion (22) without forcing.   7. Support device, in particular for an infrared reflector of a computer assistance system for osteoarticular surgery, characterized in that it comprises a pin (10, 10 ') according to any one of the preceding claims. .   8. Support device according to claim 7, characterized in that it comprises a slide (24) slidably mounted on said support portion (20) and locked in rotation around said support portion (20) by complementarity of form with said support portion (20).   9. Support device according to claim 8, characterized in that it comprises a plate (30) mounted to rotate about an axis (F) substantially perpendicular to the axis (D) of said support portion (20), and locking means in position of said plate (30) on said slide (24).