Abstract
A biopsy trocar (1) is provided for performing bone marrow biopsies. The trocar comprises a biopsy needle (2) having a cannula (4), and a mandrel (3) having a shaft (6), the shaft (6) being suitable for sliding in the biopsy needle (2). The cannula (4) has, at its distal end, at least one internal rib (12, 21) forming a helix portion on the internal wall of the cannula (4), and the shaft (6) has a helical groove (16, 26) that is able to cooperate with the internal rib (12, 21), the internal rib (12, 21) being suitable for retaining a sample of marrow in the needle (2).
Claims
1. Biopsy trocar for performing bone marrow biopsies, comprising: a biopsy needle having a cannula; and a mandrel having a shaft, the shaft being suitable for sliding in the biopsy needle, wherein: the cannula has, at its distal end, at least one internal rib forming a helix portion on the internal wall of the cannula, the axis of the helix portion of at least a part of the apex of the internal rib is off-centred with respect to the axis of the cannula, the diameter of the apex of the helix of the internal rib is greater than the internal diameter of the cannula, the shaft has at least one helical groove cooperating with the internal rib, the internal rib being suitable for retaining a sample of marrow in the needle.
2. Trocar according to claim 1, in which the width of the internal rib varies from 0 at its ends to several tenths of the value of the internal diameter of the cannula at the centre.
3. Trocar according to claim 1, in which the inclination of the internal rib with respect to the axis of the cannula and the inclination of the helical groove are identical.
4. Trocar according to claim 1, in which the inclination of the internal rib with respect to the axis of the cannula has a value of between 65 and 80.
5. Trocar according to claim 1, in which the inclination of the internal rib with respect to the axis of the cannula is 75.
6. Trocar according to claim 1, in which the internal rib extends on the internal wall of the cannula at an angle of between 30 and 180.
7. Trocar according to claim 1, in which the internal rib has a cross section of angular shape with an angle of between 10 and 120.
8. Trocar according to claim 7, in which the angle of the cross section is 60.
9. Trocar according to claim 1, in which the internal rib is a helix portion whose pitch is to the right, and the helical groove has a right-hand pitch.
10. Trocar according to claim 1, in which the mandrel screws into the needle.
11. Trocar according to claim 1, in which combined elements of said assembly, including said needle and said mandrel, are mounted in an automatic rotational drive means.
12. Biopsy device for performing bone marrow biopsies, comprising: a trocar according to claim 1; and an automatic rotational drive means, to which the trocar is rigidly connected.
13. Trocar according to claim 1, wherein the internal rib is formed by stamping the external wall of the cannula.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Other features and advantages of the present invention will become clear from the following description of preferred embodiments of the invention and by reference to the attached drawings, in which:
(2) FIG. 1 shows a perspective view of a trocar according to the invention;
(3) FIG. 2 shows a perspective view of the distal end of the trocar according to the invention;
(4) FIG. 3 shows a view of a biopsy needle of the trocar according to the invention;
(5) FIGS. 4 to 6 show views illustrating the distal end of a cannula of the trocar according to the invention;
(6) FIG. 7 shows a view of a mandrel of the trocar according to the invention;
(7) FIG. 8 shows a view of the end of a shaft of the trocar according to the invention;
(8) FIG. 9 shows a sectional view of the distal end of the trocar according to the invention;
(9) FIG. 10 shows a sectional view of the distal end of a variant of the trocar according to the invention;
(10) FIGS. 11 and 12 show views of the distal end of a variant of the cannula according to the invention; and
(11) FIG. 13 shows a view of the distal end of a variant of the shaft according to the invention.
DETAILED DESCRIPTION
(12) The trocar 1 according to the present invention, shown in FIG. 1, is composed of a biopsy needle 2 and of a mandrel 3. The biopsy needle 2 is formed by a cannula 4 lodged in a body 5. The mandrel 3 is formed by a shaft 6 lodged in a stopper 7. FIG. 2 shows the distal end of the trocar 1 in more detail.
(13) FIG. 3 shows the biopsy needle 2, of which the body 5 is composed of a Luer connector 8 and a snap-fit system 9. The shape 10 of the body 5 is hexagonal and cooperates, for example, with a hexagonal cavity of an endpiece of a drill. The snap-fit system 9 has two flexible parts that snap into recesses in the endpiece of the drill machine, allowing the trocar 1 to be supported and driven in rotation. The Luer connector 8 makes it possible, for example, to connect a syringe to the biopsy needle 2 in order to aspirate marrow, if this is necessary during a surgical procedure.
(14) FIGS. 4 to 6 show the distal part of the cannula 4. FIGS. 5 and 6 show sections along the lines indicated in FIG. 4. A bevelled grinding 11 formed at the distal end of the cannula 4 is traditionally used for bone marrow biopsy. The cannula 4 additionally has an internal rib 12. The internal rib 12 is oriented in such a way as to form a helix portion on the internal wall of the cannula 4. The pitch of the helix is a right-hand pitch, since the direction of manual or automatic rotation of the trocar during its operation is to the right. The helix portion is inclined at an angle A with respect to the axis of the cannula 4. According to the embodiments, the value of the angle A is between 65 and 80 and is preferably 75. The internal rib 12 is formed, for example, approximately 2 mm from the distal end of the cannula 4. As is illustrated in FIG. 6, the internal rib 12 forms an arc of a circle 13 having an angle B of between 30 and 180. Preferably, the angle B of the arc of a circle 13 is approximately 120.
(15) Preferably, the internal rib 12 has a cross section of angular shape, as is shown for example in FIG. 5. The angle C has a value of between 10 and 120. Preferably, the value of the angle C is 60.
(16) The internal rib 12 is preferably formed by stamping the external wall of the cannula 4, as is illustrated in FIGS. 4 and 5. This stamping is carried out by means of a cylindrical die with at least one helical groove corresponding to the shape to be obtained, which is lodged in the cannula 4, and at least one punch, whose distal end corresponds to the shape to be obtained, passing through a metal block in which the cannula 4 is lodged with the die in a bore whose diameter is slightly greater than the external diameter of the cannula 4, thus making it possible to obtain the one or more ribs without deformation and perforation of the external diameter of the cannula 4. This permits quick and simple production of the internal rib 12 by avoiding welding work in the cannula 4, the latter having an internal diameter of only a few mm. In addition, the stamping can be carried out on all types of existing trocars, thereby making them more effective.
(17) Referring to FIG. 6, the value of the diameter of the apex 14 of the helix of the internal rib 12 is greater than the value of the internal diameter of the cannula 4. The axis of the helix portion of the apex 14 of the internal rib 12 is off-centred with respect to the axis of the cannula. Thus, the width or the thickness of the internal rib 12, in the plane of the cross section of the cannula 4, varies from 0 mm at its ends to several tenths with respect to the internal diameter of the cannula 4 at the centre of the internal rib 12. For example, the maximum width of the internal rib 12 at the centre can be between 0.1 mm and 0.5 mm for an internal diameter of the cannula 4 of 2.5 mm, which corresponds to a maximum width of approximately 20% of the value of the internal diameter of the cannula 4.
(18) Of course, the representation of the shape of the apex 14 of the rib 12 is not limited to just a cylindrical shape, and instead it can be of a plane shape or a combination of plane shapes and/or a combination of plane and cylindrical shapes. In all cases, the parts forming the apex 14 of the rib 12 can be regarded as helix portions of variable diameter. The axis of at least one of the parts of the apex 14 is thus off-centred with respect to the axis of the cannula 4.
(19) FIG. 7 shows the mandrel 3, of which the stopper 7 has a hexagonal shape 15 cooperating with the cavity of hexagonal shape of the endpiece of a drill, making it possible to maintain the mandrel 3 in position with respect to the biopsy needle 2 during the rotation of the drill.
(20) FIG. 8 shows the distal part of the shaft 6 comprising a helical groove 16, of which the angulation cooperates with the angle A of the internal rib 12 of the cannula 4. The cross section of the helical groove 16 has an angular shape. The distal end of the shaft 6 has a traditionally ground cutting part 17 that permits drilling of the iliac cortical bone.
(21) FIG. 9 shows a longitudinal sectional view of the distal end of the trocar 1 comprising the cannula 4 and the shaft 6. The play existing between the internal rib 12 and the helical groove 16 can be seen. The angle D of the helical groove 16 is greater than or equal to the angle C of the internal rib 12 (see FIG. 5), and the depth of the helical groove 16 is greater than the width or the maximum thickness of the internal rib 12.
(22) FIG. 10 shows a sectional view of the distal end of the trocar 1 according to a variant. The trocar 1 comprises a biopsy needle 2, of which the cannula 4 has two diametrically opposite internal ribs 21, and a mandrel 3, of which the shaft 6 has two helical grooves 26 cooperating with the internal ribs 21 of the cannula 4.
(23) FIGS. 11 and 12 show views of the distal part of the cannula 4 having, at its distal end, two diametrically opposite internal ribs 21. The internal ribs 21 can be formed approximately 2 mm from the distal end of the cannula 4. They are oriented in such a way as to form two helix portions, which have a right-hand pitch and are inclined with respect to the axis of the cannula 4 by the same angle A.
(24) FIG. 13 shows the distal part of the shaft 6 comprising two helical grooves 26, of which the angulations cooperate with the angle A of the internal ribs 21.
(25) The biopsy device according to the present invention, intended for performing bone marrow biopsies, comprises a trocar 1 according to one of the above-described embodiments and a drill (not shown) on which the trocar 1 is mounted. In one example, with the drill having a speed of rotation of 6 revolutions per second, for a bone marrow depth to be penetrated of 30 mm, and with the average sampling time being 4 seconds, the average speed of penetration of the cannula is 7.5 mm/sec. With the theoretical pitch of the helix of the internal rib 12 being 1.39 mm, the theoretical speed of penetration of the cannula 4 is 1.39 mm6 revolutions/sec=8.34 mm/sec. The difference between the average speed of penetration and the theoretical speed of penetration of the cannula 4 thus generates the effect of an endless screw, by means of which the bone marrow is driven into the cannula 4.
