Surgical cutting apparatus

IS 2 255 648 T3

DESCRIPTION

Surgical cutting instrument.

Technical field

This application relates to a surgical cutting instrument, and more particularly to a surgical cutting instrument, and more particularly to a surgical cutting instrument having a chamber for storing the cut tissue portions. Background of Related Art

Surgical instruments for cutting body tissue are well known. One type of instrument has scissor-like jaws, in which either both jaws are moved or one jaw is moved relative to the other fixed jaw in a manner similar to scissors, that is, at an angle relative to the longitudinal axis of the instrument. An example of this scissor-type instrument is described in US Patent No. 4,994,024 to Falk. Another type of cutting instrument, especially useful in orthopedic procedures for cutting hard tissue or bone, has a cutting blade that is longitudinally slidable in the distal or proximal direction to cut the body portion. In US Patent No. 5,106,364 to Hayafuji et al., In US Patent No. 4,850,354 to McGurk-Burleson et al., In US Patent No. 5,226,910 to Kajiyama et al., And in US Patent No. 4,282,884 to Boebel, examples of this type of instrument are described.

It is also recognized that since these cutting instruments dissect body tissue, it is advantageous to remove the tissue portions as they are dissected or to keep the dissected tissue portions in the instrument. This is especially the case in endoscopic surgical procedures. Endoscopic (minimally invasive) surgical procedures are performed under visualization through small manholes or directly through small incisions in the body. Thus, if the dissected body tissue is not removed as it is dissected, the instrument needs to be removed from the surgical site each time a tissue portion is cut, the tissue portion needs to be manually removed from the instrument, and then the instrument needs to be reinserted. instrument at the surgical site. These steps have to be repeated until the entire tissue section is removed. This repeated reattachment of the instrument can be time consuming and therefore more expensive, especially in endoscopic procedures, because the surgery is performed at a remote surgical site. Repeated insertion can also cause complications in endoscopic procedures in cases where surgical site is difficult, such as in endoscopic discectomy.

As noted above, the advantages of removing or storing dissected portions of body tissue are well known. One way to continually remove the portion of tissue as it is dissected is through the use of aspiration. An example of the use of aspiration is described in US Patent No. 4,589,414 to Yoshida et al. According to the Yoshida document, a cutting member is longitudinally slid in a distal direction to cut body tissue located in the opening of the instrument and the cut tissue is withdrawn through an aspiration channel in the inner tube. US Patent No. 5,007,917 to Evans describes a rotary blade for cutting tissue and a suction tube for removing tissue. The above-mentioned patent to Falk describes a vacuum extraction channel for use with a scissor-type cutting instrument.

US Patent No. 4,282,884 to Boebel, identified above, has a storage chamber for cut fabrics. The trim assembly slides in a proximal direction, and the trimmed tissue portion is pushed into a tubular receiving member within which it is stored. At the end of the procedure, these tissue portions can be removed from the recipient limb.

Document WO 94/28803 A1 describes an endarterectomy catheter and a method for removing blockages from an artery that includes a housing of cylindrical, kidney oval or otherwise, the housing having an opening inside with a primary blade is movable . The primary blade is razor-sharp and cylindrical or otherwise with a smooth finish or serrated or threaded on the inside diameter and movable by means of a trigger wire connected by an adapter to a trigger mechanism, which displaces the primary blade back and forth within the housing to cut, encapsulate and store obstructions that protrude into the opening. The primary blade can also be moved by an electric wire and a solenoid, a hydraulic system, or other means. A guidewire positions the catheter in an artery, fallopian tube, or other cavity, and an inflatable saline anchor (s) stabilize the catheter against obstruction to make a precise cut.

DE 85 18 482 U describes a surgical instrument with an outer tube and an inner tube, which is axially movable within the outer tube. The outer tube and the inner tube comprise a device to detach pieces of tissue at a free end thereof, while the pieces of tissue are removable by aspiration through the inner tube. The outer tube has at its free end a spoon which acts as a jaw plate, which is formed at the end of the outer tube by a recess and the front face of the inner tube forms the jaw plate.

There is a need for an improved cutting instrument to store the dissected tissue portions for removal at the end of the procedure. Such an instrument would be advantageously configured to push the tissue sections into the storage chamber to avoid clogging and to allow maximum use of the space within the chamber. The instrument would also advantageously allow easy access and removal of tissue sections at the end of the procedure. Summary

A surgical apparatus is provided for cutting and storing sections of body tissue according to claim 1.

An end cap or plug assembly may be mounted at the proximal end of the cutting tube and can be removed therefrom after the cutting tube is removed from the outer tube to access the cut tissue sections.

The plug assembly preferably includes a plug and a retention member having a pair of ears that extend into a pair of notches in the shear tube such that pulling the plug when the

ES 2 255 648 T3 cutting tube is located inside the outer tube, the ears are raised further until they fit with the notches to prevent the plug from being removed.

The handle assembly preferably includes a trigger movable from a first position to a second position to advance the cutting tube and subsequently movable to a detachment position to allow detachment of the cutting tube. A release lever may be provided which is engageable with the trigger and movable from a first engaged position to a release position to allow the trigger to move to its release position to allow removal of the cutter tube from the outer tube.

In a preferred embodiment, a rotary knob rotates the elongated body portion, ie the outer tube and the cutting tube, about their longitudinal axis. A locking member can also be provided which is engageable with the rotary knob to prevent rotation of the knob.

Brief description of the drawings

Various embodiments are described herein with reference to the drawings, in which:

Fig. 1 is a perspective view showing the surgical cutting apparatus with the cutting tube in the retracted position;

Fig. 1A is an enlarged cross-sectional view taken along lines 1A-1A of Fig.

1, showing the engagement of the locking button with the rotation knob in order to prevent the rotation of the outer tube;

Fig. 2 is a perspective view of the apparatus of Fig. 1 showing the locking button in the detach position and the rotation of the outer tube;

Fig. 2A is an enlarged cross-sectional view taken along lines 2A-2A of Fig.

2, illustrating the locking button in the disengaged position of the rotation knob;

Fig. 3 is an exploded perspective view of the apparatus of Fig. 1;

Fig. 3A is an exploded perspective view of an alternative embodiment of the mechanism for locking the rotation knob;

Fig. 4 is a cross-sectional view taken along lines 4-4 of Fig. 1, showing the trigger in the initial position and the cutting tube in the retracted position;

Fig. 4A is a cross-sectional view taken along lines 4A-4A of Fig. 1 showing the cutter tube in the retracted position;

Fig. 4B is an enlarged perspective view of the distal end of the apparatus of Fig. 1 showing the cutting tube retracted within the outer tube;

Fig. 5 is an enlarged side view in partial cross-section of a portion of the cap assembly;

FIG. 5A is an enlarged, exploded perspective view of the cap assembly;

Fig. 6 is a cross-sectional view similar to Fig. 4, showing the trigger in the proximal position and the cutting tube in the advanced (distal) position for cutting body tissue;

Fig. 6A is a cross-sectional view similar to Fig. 4A, showing the cutting tube in the advanced position;

Fig. 6B is an enlarged perspective view of the distal end of the apparatus of Fig. 1 showing the cutting tube in the advanced position for cutting body tissue;

Fig. 7 is an enlarged cross-sectional view corresponding to the position of the trigger and cutting tube in Fig. 6;

Fig. 7A is an enlarged cross-sectional view corresponding to the position of the trigger and cutting tube when the trigger is moved to the release position;

Fig. 8 is a cross-sectional view similar to Fig. 4, showing the release lever in the release position, the trigger in the distal release position, and the cap assembly while being pulled back to remove the cutting tube;

Fig. 9 is a partial cross-sectional side view illustrating grasping the plug to remove the cutting tube and plug assembly from the outer tube;

FIG. 10 is a partial cross-sectional side view illustrating gripping the plug retainer to remove the plug assembly from the cutting tube;

Fig. 11 is a side view illustrating removal of the cap assembly from the cutting tube;

Fig. 12 is a side view showing the direction of insertion of the plunger into the cutting tube to remove the tissue sections contained therein; and Fig. 13 is a side view showing the plunger inserted into the cutting tube to push the tissue sections out of the distal end.

Detailed description of the preferred embodiments

Referring now to the drawings, and in particular to Figs. 1 and 1A, the surgical apparatus, generally designated by reference numeral 10, for cutting body tissue is illustrated. The apparatus has an elongated outer tube or endoscopic portion 14 extending from the sheath or handle assembly 12. The outer tube 14 is sized and configured for either insertion through a trocar cannula or through a small incision in body tissue. An elongated hollow inner cut tube 16 is slidably positioned within outer tube 14. Cut tube 16 is advanced distally by actuation of handle assembly 12 to cut body tissue positioned in window 61 of outer tube 14. An anvil 66, located at a distal end of outer tube 14, pushes the cut portion of body tissue back into cutting tube 16. In this manner, the apparatus can be inserted into the body and the cutting tube 16 can be repeatedly advanced to cut body tissue with the anvil 66 pushing proximally the cut tissue sections within the cutting tube to allow storage of a plurality of portions. of tissue. The cutting tube 16 can subsequently be detached from the apparatus with ease to access and remove the individual tissue sections stored therein. This is accomplished by removing the plug assembly, which includes a plug 92 and plug retainer 90, from the proximal end of cutting tube 16 in the manner described below.

A release lever 42 is mounted on handle assembly 12 and cooperates with trigger 40 to allow movement of trigger 40 to a release position so that cutting tube 16 can be removed from the apparatus. Fig. 1 shows

ES 2 255 648 T3 release lever 42 in the engaged (locking) position. Also shown in FIG. 1 is the rotation knob 20 for rotating the outer tube 14 (and inner cutting tube 16) about its longitudinal axis. A locking button 22 is engageable with the rotation knob 20 to lock the knob 20 and prevent rotation of the tubes 14, 16. The locking button 22 and the release lever 42 are described in detail below.

Turning now to the individual components of apparatus 10, and first to handle assembly 12 as illustrated in Figs. 1 and 3, the handle assembly 12 is comprised of two shell halves 12a, 12b welded together or joined by other known methods. Trigger 40 is pivotally mounted to shell halves 12a, 12b via mounting pin 41 extending through aperture 46. Trigger 40 is movable between three positions. In the first (initial) position shown in Fig. 4, the cutter tube 16 is in the retracted position. In the second position, as shown in Fig. 6, trigger 40 is moved toward stationary grip 48 to advance cutting tube 16 distally. In the third position, the trigger 40 is moved to a distal release position shown in FIG. 8, which allows the cutting tube 16 to be removed from the outer tube 14 in the manner described below.

In the initial position of the trigger 40, fingers 43 projecting apart from each other engage the rod portion 89 of the cap assembly, which is mounted to the cutting tube 16, such that proximal movement (in the direction of clockwise) of trigger 40 in the direction of the arrow in Fig. 6, slides cutting tube 16 distally to cut tissue located in window 61 (Fig. 6A).

Trigger 40 is normally biased to the third position by extension spring 50; however, it is prevented from moving to this position by lever mounting pin 56 when release lever 42 is in the locked position. Thus, when release lever 42 is in its normal locking position of Fig. 4, trigger 40 is essentially biased by extension spring 50 to the first position. When release lever 42 is pivoted to its release position of Fig. 8, trigger 40 is no longer locked and can spring forward to its third position. As shown in Fig. 4, one end of extension spring 50 is mounted at post 31 of stationary grip 48 and the other end extends through opening 38 in trigger 40. Stop 45 limits movement trigger pivot 40.

Release lever 42 blocks movement of trigger 40 due to mounting pin 56. Mounting pin 56 extends through opening 33 in handle shell half 12a. Torsion spring 59 biases lever 42 to the trigger lock position shown in Figs. 4 and 6. In this locked position, trigger 40 is prevented from moving to its distal position by mounting pin 56 because slot 52 in trigger 40 collides with curved surface 56b of pin 56. This prevents removal of cutting tube 16 from the outer tube 14, since projecting fingers 43 remain engaged in rod portion 89 of the cap assembly. When the release lever 42 is pivoted to its upward release position, as shown in Fig. 8, the trigger slot 52 can bypass the mounting pin 56 due to the alignment of the flat portion 56a of the mounting pin 56 with surface 52a of notch 52. Accordingly, the trigger 40 jumps forward to the release position such that the projecting fingers 43 are out of engagement with the plug assembly to allow removal of the cutting tube 16.

Turning now to outer tube 14, and referring to Figs. 1, 3, and 4, the outer tube 14 has an open distal end 60 for mounting the anvil (tissue engaging member) 66, a window 61 for receiving the body tissue to be cut, and a proximal end portion 62 positioned within the recess. 36 formed by the shell halves 12a, 12b. Lip 65 helps retain outer tube 14 in handle assembly 12. The central hole 64 of outer tube 16 is dimensioned to slidably receive cutter tube 16. A cylindrical seal 67 is positioned within outer tube 14 and surrounds cutter tube 16 to restrict gas leakage through of the gap between the outer tube 14 and the cutting tube 16 if the body cavity is insufflated during the procedure. Clearly, other types of seals are also contemplated to restrict gas flow.

The outer diameter of the outer tube 14 is preferably about 10mm and preferably has a taper as shown in portion 63 to an outer diameter of about 5mm, although other dimensions are clearly contemplated as well. Anvil 66 is mounted to distal end 60 of outer tube 14 via dovetail fitting 66a (Fig. 4B) and has an angled surface 68 that corresponds to angled distal tip 75 of outer tube 12 (see Figs. 4A and 4B). The angled distal tip 75 facilitates handling and use of the apparatus since it can be more easily hooked behind the target tissue. Angled surface 68 of anvil 66 also has a straight portion 68a that helps to push cut portions of tissue proximally into cutting tube 16 as cutting tube 16 is advanced. Angled surface 68 is preferably angled relative to the central longitudinal axis of outer tube 14 with a range from about 90 degrees to about 140 degrees, and preferably an angle R of 130 degrees. Alternatively, other angles can be used, such as a 90 degree angle.

An orientation plate 70 is positioned within the outer tube 12 and extends through the slots 72 to seat within the cavity 37 of the handle assembly 12. The central D-shaped opening 74 is dimensioned to receive the cutting tube. 16 through it.

The cutting tube 16, as shown in Figs. 3, 4, 4A and 4B, has an open proximal end 80 and an open distal end 82. The open distal end 82 is shown with a circumferential straight cutting edge, although a one-piece formed angled edge may alternatively be provided. with the cutting tube 16 or as a separate element attached thereto. A plurality of cutting teeth may also alternatively be provided. The cutting tube 16 has an axial hole 86 that extends the length of the same forming a chamber for guar4

ES 2 255 648 T3 give the individual portions of tissue as they are cut. Anvil 66 pushes cut tissue sections back into axial hole 86 to create space in cutting tube 16 to receive the next cut tissue section when cutting tube 16 is again advanced to cut tissue.

The cutter tube 16 has a flattened bottom surface 81 that sits on the flat bottom surface of the D-shaped opening 74 of the orientation plate 70. This prevents lateral movement and rotation of the cutter tube and also Aligns cutter tube 16 within outer tube 14.

Referring to Figures 3, 4, 5, and 5A, the plug assembly (end cap assembly) is mounted to the proximal end 80 of cutting tube 16 and includes a plug 92 and plug retainer 90 to prevent removal of plug 92. Plug retainer 90 is seated in the proximal portion of axial bore 86, is spring biased distally by compression spring 101 mounted in tubular portion 117 of plug 92, and has a pair of spaced apart ears 94 seated in a pair of notches 96 formed in shear tube 16. The ears 94 are supported by the pin 103 which has an outer diameter nearly the same as the cutter tube 16 to allow friction engagement of the pin 103 and the cutter tube 16 to stabilize the cutter tube 16. The end Proximal cut tube 16 collides with surface 107 of cylindrical portion 113 of plug retainer 90. Proximal extensions 116 are seated within recesses 118 formed in a head portion 112 of plug 92.

Plug 92 has a knurled gripping surface 98 at its proximal end and a cam nose 99 at its distal end. O-ring 97 is seated in a circumferential recess of cam nose 99 to provide a seal to prevent the escape of insufflation gas through cutting tube 16 if the apparatus is used in a procedure performed under insufflation. Other seals can also be used. In the initial position, notches 111 of ears 94 rest on cam surface 105 of cam nose 99 and ears 94 extend through notches 96 of cutter tube 16 to connect the plug assembly to the tube. cutter 16. This is best shown in Fig. 4. If the plug 92 is grasped by its knurled surface 98 and pulled proximally, the cam nose 99 will be pulled proximally between the ears 94 to allow the cam surface 105 to lift the ears 94 further out into the socket. interlocking with the notches 96 of the cutter tube 16, as shown in Fig. 8 and 9. This allows the cutter tube 16 to be removed. Note that this interlocking engagement prevents removal of plug 92 from cutter tube 16 if knurled surface 98 is pulled. In this way, the lugs also function to provide a locking device to prevent inadvertent disengagement of the tube assembly. cutting tube plug 16.

The cap assembly can be removed from the cutting tube 16 to access tissues stored therein only when the knurled gripping surface 91 of the cap retainer 90 can be grasped. This occurs only when the release lever 42 has been rotated to its release position to disengage the projecting fingers 43 of the trigger 40 from the rod portion 89, and the shear tube 16 is removed from the outer tube 14, as shown. in Fig. 10. Only when this occurs can knurled surface 91 be accessed. When plug retainer 90 is pulled proximally in the direction of the arrow, ears 94 can slide out of notches 96 as cam surfaces 96 are pushed inward. through wall 115 of cutter tube 16 adjacent notches 96 and plug retainer 90 (and plug 92 attached thereto) can be removed from outer tube 14 as shown in FIG. 11. T tissue sections can be removed and arranged for pathology.

As best shown in FIG. 7, recess 93 in the cap assembly is configured to receive stop ball 85 when trigger 40 is in the release position. Ball 85 is seated in recess 83 in shell half 12b and is biased by compression spring 87 so that it engages recess 93 in plug retainer 90 to prevent shear tube 16 slides out of outer tube 14 when trigger 40 is in the release position (see FIG. 7A). This engagement also provides a tactile feel to the user that the cutter tube 16 has been released for removal from the outer tube 14 as well as when the cutter tube 16 has been properly reinserted into the outer tube 14 of the apparatus.

Turning now to rotation knob 40 and referring to Figs. 1 and 3, as mentioned above, rotation knob 20 extends through cutout 34 in shell halves 12a, 12b and is mounted to outer tube 14 to rotate outer tube 14 about its longitudinal axis. The rotation of the outer tube 14 causes the rotation of the cutter tube 16 due to the orientation plate 70 rotating with the outer tube 14. The leg 22a of the rotary interlock button 22 is seated within the recess 23 of the mounting block 25, slidably mounted on the handle assembly 12, and spring biased to the interlocked position by the spring 30. The lock button interlock 22 is shown in Figs. 1 and 1A in the locked position. In this locking position, the pair of locking fingers 24 of the mounting block 25 engage with a pair of recesses 26 in the rotation knob 20 to thereby prevent rotation of the knob 20. When it is desired to rotate the outer tube 14 to change the orientation of the window 61, the locking button 22 is slid proximally in the direction of the arrows in Figs. 2 and 2A. This causes the mounting block 25 to slide proximally to disengage the locking fingers 24 from the recesses 26 and allow free rotation of the knob 20. When the locking button 22 is released by the user, it snaps back to the off position. interlocking under the biasing force of spring 30.

An alternative embodiment of a rotary knob locking mechanism is shown in Fig. 3A. The interlock button 122 has a mounting leg 123 seated within the recess 126 in the interlock plate 124. The interlock plate 124 has a single one-piece extension 125 that engages with a single recess on the rotary knob to prevent rotation.

In operation, initially referring to Figs. 4, 4A and 4B, the trigger 40 is initially separated from the stationary grip 48 with projecting fingers 43 that engage the rod portion 89 of the plug 92. As shown, the shear tube

ES 2 255 648 T3 is in the proximal (retracted) position and the release lever 42 is in the locking position parallel to the longitudinal axis of the tubes 14, 16.

The apparatus is inserted into the body, either through a cannula or directly through a small incision, and the outer tube 14 is positioned adjacent the surgical site such that the tissue to be cut sits within the window 61. If the user needs to reorient window 61, locking button 22 slides proximally to disengage locking fingers 24 from recesses 26 of rotation knob 20. The locking button 22 is held by the user in the proximal position and the rotation knob is turned to rotate the outer tube 14 (and window 61) to the desired position. Once the tissue has been properly seated, trigger 40 is actuated by pushing it toward stationary grip 48 to advance cutting tube 16 distally toward anvil 66, as shown in Figs. 6, 6A and 6B. The cutting edge of the cutting tube 16 passes through the window 61 to pierce and dissect the body tissue seated therein. As cutting tube 16 passes over anvil 66, angled surface 68 and straight surface 68a enter the hollow interior of cutting tube 16, and proximally push the dissected tissue into cutting tube 16. After dissection , trigger 40 is released, returning cutting tube 16 to the proximal position of FIG. 4A. Note that the plug 92 cannot be removed from the cutter tube 16 due to the engagement of the ears 94 with the notches 96 of the cutter tube 16.

The user can then once again squeeze trigger 40 to advance cutting tube 16 to dissect another portion of the body tissues positioned in window 61. As cutting tube 16 advances to its most distal position, the anvil 66 once again pushes the dissected tissue back (proximally) into cutting tube 16. Cutting tube 16 can be repeatedly advanced and retracted in this manner to dissect the entire desired portion of body tissue, with anvil 66 advantageously pushing the sections of body tissue proximally to provide space for the next portion of body tissue. FIG. 9 illustrates a plurality of body tissue sections T positioned within cutting tube 16.

Note that when trigger 40 and cutting tube 16 are in the position of Figs. 4 and 4A, the cutting tube 16 cannot be removed from the outer tube 14. If the user grasps the gripping surface 98 of the plug 92 in an attempt to remove the cutting tube 16, the projecting fingers 43 of the trigger 40 will block the removal of cutting tube 16. Also, plug 92 cannot be removed at the position of Figs. 4 and 4A, of the cutter tube 16 because the ears 94 engage in the notches 96 of the cutter tube 16 and if the user pulls on the grip surface 98, the cam nose 99 of the plug 92 will further lift the ears to their fits notches 96.

After use, to remove tissue from chamber 86 of cutter tube 16, release lever 42 is rotated counterclockwise to the position of Fig. 8 so that flat portion 56a of mounting pin 56 is aligned with surface 52a of trigger notch 52. Accordingly, notch 52 rides on mounting pin 56 to allow trigger 40 to spring forward to its distal release position under the extension force of spring 50. In this distal release position, projecting fingers 43 are disengaged from the notch 89 of the cap 92. Thus, when the user grasps the gripping surface 98 of the plug 92 and pulls it proximally, the entire cutting tube 16 is withdrawn from the outer tube 14 through the opening in the proximal end 62 as the ears 94 of the retainer. 90 of plug fits into notches 96 of shear tube 16.

After the cutting tube 16 has been removed as indicated in Fig. 9, to access the tissue portions, the gripping surface 91 of the plug retainer 90 is grasped and pulled proximally (Fig. 10 ). This removes plug 92 and plug retainer 90 from cutter tube 16, since lugs 94 are raised enclosed by notches 96 adjacent wall 115 so that they can slide out of notches 96. FIG. eleven illustrates the plug assembly separated from cut tube 16. Tissue sections can then be removed from cut tube 16 and arranged in a manner similar to their pre-dissection configuration to aid in tissue examination and testing. Figs. 12 and 13 illustrate a method of removing tissue sections T in which plunger 100 is inserted through open proximal end 80 of cutting tube 16 to push tissue sections out through open distal end 82.

For subsequent use of the instrument, the cutting tube 16 is inserted through the opening in the proximal end 62 of the outer tube 14 until the user notices the engagement of the stop ball 85 with the recesses 93 of Fig. 7A. . Trigger 40 is then depressed toward stationary grip 48, causing release lever 42 to rotate clockwise about center, under the force of torsion spring 59, to its original position of Fig. . 4, allowing the projecting fingers 43 to engage the rod portion 89 of the plug 92. The cutting tube 16 can then be actuated by squeezing the trigger 40 in the manner described below for reuse.

The apparatus can be entirely disposable, and can be disposed of after use. It can also be partially disposable, with some parts being removed, for example the cutting tube and cap assembly, while the remaining parts, for example the handle assembly, are reused. Alternatively, the apparatus may be composed of suitable materials to allow resterilization of the instrument parts for later reassembly and reuse. The apparatus 10 can be packaged in a kit with various cutting tubes (and plug assemblies).

Instrument 10 can be used to dissect tissue following a variety of surgical procedures. For example, in endoscopic discectomy procedures, the instrument can be inserted into the disc space to rapidly dissect portions of the disc. The cutting tube can then be removed in the manner described above and the tissue sections can be removed and analyzed. The instrument can also be used as a trephine to cut and store bone portions in other surgical procedures.

It should be understood that various modifications can be made to the embodiments described herein. For example, you can use a shear tube that po11

ES 2 255 648 T3 is either teeth or has other cutting configurations such as a beveled edge. The instrument can even be disposable or reusable. Therefore, the above described should not be considered as limiting, but merely as examples of preferred embodiments. Other embodiments may be contemplated within the scope of the appended claims.