Abstract:
Please substitute the following paragraph(s) for the abstract now appearing in the currently filed specification: A biopsy needle for removal of tissue from a patient includes an outer tube having a distal end that has an inner diameter (IDtip) and an inner tube within said outer tube and having an inner diameter (IDsc), defined at the distalmost section of the inner tube. The needle also includes a snare having a first end connected to the inner tube and a second end coupled to the outer tube. The snare has a variable diameter that is controlled by rotation of the inner tube with respect to the outer tube in a prescribed direction resulting in the opening and closing, respectively, of the snare, A ratio (R) defined as (IDsc)/(IDtip) is greater than 1.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to a surgical instrument, known variously as a biopsy needle or cannula that is used to gather tissue, such as bone marrow, from living persons or animals for pathological study. More specifically, the invention relates to a biopsy needle having an improved structure for severing a tissue sample and/or retaining the tissue sample within the needle.  
       BACKGROUND  
       [0002]     For various medical reasons, such as evaluating the histology and/or pathology of a tissue, it is often necessary for a physician to obtain a sample of a patient&#39;s body tissue. In particular, bone marrow is frequently retrieved to study its cellularity and potential infiltration with abnormal cells. The currently available procedures and instruments used for obtaining bone marrow biopsy samples, while not overly complex, almost universally result in excessive patient discomfort and often recover inadequate quantities of biopsy material which sometimes is distorted and/or difficult to interpret. In the standard bone marrow procurement protocol, using currently available instruments, (such as those disclosed in U.S. Pat. No. 4,262,676 to Khosrow Jamshidi), the patient is prepared with a suitable local anesthetic at the posterior superior iliac crest/spine. Then, a relatively narrow needle is inserted to obtain an aspirate of liquid bone marrow material to make slides for examination of cellular morphology and to evaluate the surface immunophenotype of the bone marrow cells with flowcytometry. This portion of the procedure, referred to as the bone marrow aspiration, is generally relatively less painful than the bone marrow biopsy procedure using a conventional biopsy needle. Using newer bone marrow biopsy needles which actively capture specimens, and minimize manipulation of the needle after insertion, the aspirate procedure appears to be more painful than the biopsy procedure.  
         [0003]     After the aspirate is obtained, if necessary, a biopsy of the bone marrow is taken. A significantly wider bore needle having an inner diameter that will accommodate a suitable marrow sample is prepared with an inner stylet that extends beyond the distal end of the outer needle. The stylet&#39;s distal end may be cut at an angle, with the leading edge sufficiently sharp to pierce tissue and bone. With the stylet in place within the outer needle, the needle is pushed through the outer layers of skin and subcutaneous tissue until the needle tip reaches the surface of the cortical bone. The needle and stylet are then pushed into and through the cortical layer until the tip has penetrated into the bone marrow space.  
         [0004]     The stylet is then removed from the proximal end of the needle, which opens up the core of the needle to accommodate entry of bone marrow material for collection and retrieval. The needle is then usually advanced another 1 to 2 centimeters at minimum with a slight twisting motion. Often, the distal end of the needle will also be provided with an angled cut and sharpened leading edge to facilitate cutting and coring the tissue. By providing a slight twisting motion as the needle is advanced, usually with no more than quarter or half turns, an appropriate sample is cored from the marrow tissue and enters the inner passage of the marrow needle.  
         [0005]     At this point, the marrow biopsy sample is ready to be removed from the patient, although it is important that the biopsy remain within the needle as the needle is withdrawn to ensure recovery of the specimen. If the biopsy becomes dislodged and falls through the distal end of the biopsy needle, the specimen is irretrievably lost. The procedure is then unsuccessful and must be repeated from the beginning.  
         [0006]     Various methods have been utilized by physicians to try to prevent the biopsy specimen from dislodging from the needle. For example, after the needle has entered the bone and fully cored a sample from the marrow, some physicians, will pull the biopsy needle back a few millimeters and then advance it a few millimeters at a different angle than the first insertion. This theoretically will “cut” the biopsy piece at the tip of the needle. Other physicians attempt to dislodge or disrupt the connection between the specimen and the bone by making multiple complete clockwise and counterclockwise rotations of the biopsy needle while within the bone. Some physicians even hit the proximal end of the biopsy needle at its handle in an attempt to mechanically disrupt the connection between the specimen and the additional bone.  
         [0007]     As can be plainly realized, these manipulations at the end of the procedure, attempts at ensuring that the specimen remains within the needle, can often produce substantial discomfort and anxiety to the patient. Sometimes when the bone marrow is very soft, as in patients with osteoporosis, almost all of these attempts are futile because the bone structure is so fragile. Conversely, sometimes when the bone marrow is very fibrotic, which occurs in patients with myelofibrotic diseases or in AIDS patients, it is difficult to dislodge the core biopsy, since the bone marrow itself is reinforced by the surrounding tissue. In those cases, the cored biopsy often remains attached to the bone and is not successfully recovered.  
         [0008]     Other attempts at designing a more efficient and successful biopsy needle have met with little or no success, for various reasons, including the complexity of the devices. For example, U.S. Pat. No. 3,605,721 to Hallac, discloses a biopsy needle in which an inner tube has a weakened portion represented by strips extending between distal and proximal portions of the inner tube. The distal portion of the inner tube is adhered to an outer tube and will not rotate. Once a biopsy has entered the needle, the proximal portion of the inner tube is rotated, causing the strips to twist together and eventually break off. This twisting motion tends to twist the strips to the tube&#39;s center, thus hopefully keeping the biopsy piece proximal of the twisted and broken strips for later removal. This particular biopsy needle is only a disposable device, since the strips are broken or irreversibly warped by deformation during the twisting process. Another disadvantage is the lack of control over the twisting motions or the breakage of the strips. Essentially, the operator is left to twist the inner tube until resistance to that twisting is lost, indicating that the strips have severed. There is also no way of releasing the device&#39;s grip on tissue during the procedure, should any problems arise.  
         [0009]     U.S. Pat. No. 5,074,311 to Hasson discloses a biopsy device that includes a pair of inner jaws that can be actuated within the outer needle to “bite off” any biopsy piece that has entered the needle. The disadvantages of this device include multiple small mechanical linkages and parts including pivot pins, which are extremely difficult and expensive to assemble and maintain, in addition to the greatly increased chance of mechanical failure resulting in failure to retrieve an adequate specimen.  
         [0010]     U.S. Pat. No. 5,522,398, to Goldenberg et al., discloses a bone marrow biopsy needle; however, the patent teaches that an inner diameter B at the distal tip of the needle (as shown in  FIG. 4  thereof) is substantially equal to an inner diameter C of the inner tube (as shown in  FIG. 3C ) so that there will be no ridge or lip within the instrument to impede tissue entering the inner lumen of the needle. However, observations over time of the performance of needles constructed in this manner indicates that such a relationship may impede specimen transit into and through the needle, and that a virtual obstruction phenomena may develop as a result of the above relationship between the two inner diameters. Compromise of specimen transit into the needle results in an inability of the specimen to move forward into the lumen of the needle. In addition, as the needle penetrates tissue, external pressures, especially those produced by dense bone, could deform or change the diameter at the needle tip (inner diameter B) or might transmit a force through the wall of the needle, marginally decreasing the diameter of the inner tube or snare (inner diameter C). These changes could dynamically alter the relationship between the inner diameters and cause a virtual obstruction, impeding specimen transit and making it difficult for the specimen to move forward into the needle.  
       SUMMARY  
       [0011]     In view of the deficiencies noted in the prior references and the current protocols, it is an object of the present invention to provide an improved biopsy needle that will sever a tissue sample from surrounding tissue or hold it with sufficient force such that the action of removing the needle detaches the piece from the surrounding tissue.  
         [0012]     It is another object of the invention to provide a biopsy needle that requires minimal manipulation of the needle at the end of the procedure, thus decreasing patient pain and anxiety.  
         [0013]     It is a further object of the invention to ensure obtaining a biopsy sample with each attempt, thus decreasing the number of necessary biopsy attempts, and the time, effort and money expended on the overall procedure.  
         [0014]     It is yet another object of the invention to provide a biopsy needle that is simple and inexpensive to manufacture, may be reusable, and is simple to operate.  
         [0015]     According to the objects of the invention, an improved biopsy needle has an outer cannula, an inner tube and a stylet. The distal end of the inner tube is provided with a snare in the form of a coil extending from the inner tube. The free end of the coil is adhered to the outer cannula. Upon rotation of the inner tube with respect to the outer cannula, the coil will decrease in diameter to either sever or hold the biopsy piece within the outer needle. After removal of the needle from the patient, rotating the inner tube in the opposite direction will cause the coil to expand to its original diameter and allow the biopsy piece to be removed from the needle.  
         [0016]     In yet another aspect, a biopsy needle for removal of tissue from a patient, according to one embodiment, includes an outer tube having a distal end, contributing to a needle tip, that has an inner diameter (ID tip ) and an inner tube within said outer tube. The needle also includes a snare having a first proximal end connected to the inner tube and having an inner distal diameter (ID sc ) and a second distal end coupled to the outer tube. The snare has a variable diameter that is controlled by rotation of the inner tube with respect to the outer tube in a prescribed direction resulting in the opening and closing, respectively, of the snare, wherein a ratio (R)=(ID sc )/(ID tip ) is greater than 1. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     Other objects, advantages and embodiments than those described above will become apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments in conjunction with a review of the appended drawings, in which:  
         [0018]      FIG. 1  is a perspective view of a biopsy needle in accordance with the present invention;  
         [0019]      FIG. 2  is an exploded view of the biopsy needle according to the present invention;  
         [0020]      FIGS. 3   a - 3   e  are detail perspective views of the distal ends of various components during operation of the biopsy needle;  
         [0021]      FIG. 4  is a cross-section of the distal end of the outer cannula;  
         [0022]      FIG. 5  is a perspective view of the biopsy needle showing operation by a physician;  
         [0023]      FIG. 6A  is a detail side view of the inner tube of the present invention according to one embodiment;  
         [0024]      FIG. 6B  is a detail side view of the inner tube of the present invention according to another embodiment; and  
         [0025]      FIG. 7  is a cross-section view through the handle piece of the biopsy needle. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]     Referring now to  FIGS. 1 and 2 , a biopsy needle  10  has an outer cannula  12 , an inner tube  14  with a snare  16  at its distal end  18 , a stylet  20 , and a handle assembly  22 . In  FIG. 2 , the assembly of the present biopsy needle  10  is shown in an exploded view.  
         [0027]     As part of the handle assembly  22 , a lever  24  fits into a corresponding groove  26  within a handle piece  28 . The lever  24  actuates the snare  16  within the outer cannula  12  without any movement of the outer cannula  12  relative to the patient (not shown). The functioning of this lever  24  is described more fully below. The inner tube  14  has a snare  16  at its distal end  18  and a gear or lever connector  30  mounted on its proximal end  32 . The inner tube  14  is inserted into the proximal end  34  of the outer cannula  12  with the gear or lever connector  30  extending out of the proximal end  34 , which facilitates connection of the lever to the inner tube and uniform conversion of lever rotation to inner tube rotation. As can be seen in  FIG. 4 , the interior of the outer cannula  12  has a constant inner diameter A along a majority of its length, and a portion  38  having a smaller inner diameter B at its distal tip  40  allowing the inner tube to fit within the outer tube while keeping the inner diameter of the inner tube C nearly equivalent to the inner diameter of the distal tip B.  
         [0028]     In contrast to the teachings of the present inventor&#39;s prior ‘398 patent, the present applicant has discovered that the narrow inner diameter B at the distal tip  40  should not be substantially equal to the inner diameter C of the inner tube  14  in order to optimize the ability of the specimen to move forward into the needle. The ability of the specimen to move forward into the needle  10  can be described by the following equation: ID sc (d)/ID tip (d)=R, where d is the needle penetration distance, ID sc (d) is the internal diameter of the most distal aspect of the snare (as indicated by the legend C in  FIG. 3   c ) as a variable dependent on the penetration of the needle  10  into a tissue and ID tip (d) is the internal diameter of the tip  40  which also may be dependent on forces that develop relative to the penetration of the needle a certain distance (d) into a tissue. In accordance with the present invention, the present applicant has discovered that R should be greater than or equal to one since as R increased, the potential interaction between the core specimen and the internal diameter (C) of the snare  16 /inner tube  14  decreases. The internal diameters are described as variables dependent on the needle penetration distance (d), since it is possible, depending upon the structural integrity of the wall components, that external forces applied as the needle penetrates tissue could influence the specified internal diameters.  
         [0029]     In accordance with the present invention, there is a direct correlation between needle performance and the R averages and the ratio R provides a valid descriptor of intraluminal specimen transit and needle performance. According to a first embodiment R≧1.00; according to a second embodiment, R≧.15; according to a third embodiment, R≧1.20; according to a fourth embodiment, R≧1.25; according to a fifth embodiment, R≧1.30; and according to a sixth embodiment, R≧1.35. It will be appreciated that the above values are merely exemplary in nature and that other values are equally suitable so long as the ratio R eliminates the occurrence of the obstruction phenomena that makes it difficult for the specimen to move forward into the needle  10  or compromises specimen recovery at the conclusion of the procedure.  
         [0030]     It will also be appreciated that since R represents a ratio, small differences in the values of the numerator and denominator can result in substantial practical and physical implications influencing specimen transit and needle performance. The applicant has therefore discovered that an R average value of about 1.0 or less will produce a virtual obstruction, which is not desirable during the specimen capture and withdrawal procedure. This is in direct contrast to Applicant&#39;s previous patent where diameter equivalence between the distal tip  40  and the inner tube  14  was suggested and still consistent with the concept of avoiding a ridge or lip between the distal tip  40  and the inner tube  14  which could impede tissue entering the instrument.  
         [0031]     The inner tube  14  is inserted until the snare  16  reaches the shoulder  42  provided on the interior of the outer cannula  12  at the position where the diameter changes. However, other embodiments not requiring a shoulder are possible in which the outer surface of the inner tube is opposed to the inner surface of the outer tube, the two surfaces are bonded and the distal portion of the inner and outer tube are formed into a distal cutting tip.  
         [0032]     With the gear or connector  30  extending proximal of the outer cannula&#39;s anchor  44 , the cannula and snare assembly are attached to the handle piece  28  at the distal facing side  52  of the handle  22 . The gear  30  of the inner tube  14  is inserted into a complementary hole  48  in the lever while the anchor  44  of the outer cannula  12  mates with a complementary hole  49  in the handle piece  28 . Thus, when the lever  24  is rotated within its groove  26  with respect to the handle piece  28 , the inner tube  14  will rotate with respect to the outer cannula  12 . A cannula cap  50  is assembled onto the distal tip  40  of the cannula and threadedly engaged to the forward facing end  52  of the handle piece  28 . In other embodiments, a non-threaded cannula cap or similar retaining member can be bonded to the forward facing end  52  of the handle piece  28  to ensure that the outer cannula  12  does not rotate or move longitudinally relative to the handle  28 . The stylet  20  is inserted into the proximal end  32  of the inner tube until a distal tip portion  54  of the stylet extends beyond the distal tip  40  of the cannula. A stylet cap  56  can then be threadedly engaged to the proximal facing side  46  of the handle piece, covering the proximal end  58  of the stylet to prevent it from moving proximally within the inner tube  14 . Other embodiments not requiring a stylet cap in which the proximal end of the stylet reversibly connects to the handle to prevent it from moving proximally are possible.  
         [0033]     As can be seen in  FIGS. 3   a  and  4 , both the distal ends  40 ,  54  of the stylet and the outer cannula preferably have sloped end faces  60 ,  62  although it is not necessary. This improves the cutting actions of the both the stylet and the outer cannula by providing sharp leading edges  64 . In this position, the stop  66  at the proximal end  58  of the stylet preferably mates with a complementary indent  68  ( FIG. 7 ) in the handle piece  28  to maintain the rotational orientation of the stylet  20  with respect to the outer cannula  12  such that the slopes of the two distal ends  40 ,  54  are approximately parallel, or aligned optimally to result in an efficient piercing and cutting action and the stylet does not rotate relative to the outer cannula during the initial bone penetration. This is the configuration that would be used for initiating insertion of the biopsy needle  10  into the bony cortex.  
         [0034]     As can be seen in  FIG. 3   b , which is a partial cutaway view, the free end  70  of the coil snare  16  includes a tab  72  that engages or is attached to a hole  74  ( FIG. 4 ) on the interior surface of the outer cannula  12 . This hole  74  preferably extends through the entire wall of the outer cannula. If desired, the tab  72  can be adhered to the hole  74  in the outer cannula through the use of adhesives, welding, or any known attachment process. However, it will be appreciated that the tab  72  and hole  74  can be eliminated and the outer surface of the inner tube can be bonded to the inner surface of the outer tube by welding or some other type of attachment method. It will therefore be appreciated that so long as the two structures are attached to one another, any number of different techniques can be used to accomplish such a coupling action, including the illustrated manner or using a direct bond between two surfaces, etc.  
         [0035]     After the needle  10  is inserted into the marrow, the stylet  20  is removed proximally without any movement of the outer cannula  12  with respect to the patient, minimizing discomfort. As can be seen in  FIG. 3   c , marrow tissue may now enter the passageway within the outer cannula  12  through the distal end  40  of the outer cannula as the needle is advanced further and can enter the inner passageway of the inner tube  14 , preferably to a position proximal of the snare  16 .  
         [0036]     Specimen transit refers to the process of specimen movement from the distal tip of the needle into the snare and inner tube lumen. The efficacy of specimen transit is modulated by the configuration of the tip and the relationship of (ID sc ) to (ID tip ). The advantages of snare capturing mechanisms are realized only by ensuring that specimen transit is maximized, according to the R value relationship.  
         [0037]     To operate the snare  16 , i.e. to cause cutting and/or holding of the biopsy piece  76  within the inner tube  14 , the lever  24  attached to the proximal end  32  of the inner tube is rotated in the direction of arrow D as seen in  FIGS. 3   d - 3   e  and  5 . Of course, the snare  16  can be designed such that rotation in the opposite direction causes the same effect. With full rotation (180 degrees) of the lever  24 , the inner tube  14  and snare  16  achieve a position similar to that shown in  FIG. 3   e , in which the inner tube  14  has been rotated approximately 180 degrees. Since the free end  70  of the snare is fixed to the outer cannula  12 , the result of the rotation is that the coil of the snare  16  will tighten so that the cross-sectional area through the snare  16  is approximately less than a third of the area when in the open configuration. It is also contemplated that any decrease, even a slight decrease, in the cross-sectional area of the snare will cause pressure on the biopsy piece  76 . Therefore, while the current amount of rotation is preferred, it is not necessary for the proper functioning of the present invention.  
         [0038]     As seen in  FIG. 5 , movement of the lever  24  can be independent of any movement of the handle piece  28  or the outer cannula  12 . Therefore, the outer cannula  12 , which is in direct contact with the patient while the sample is taken, can remain substantially stationary. As motion of the outer cannula  12  relative to the patient, a painful maneuver, is not required to sever and capture the specimen, incorporation of the snare mechanism limits painful needle manipulations.  
         [0039]     With the tightening of the snare  16 , there is a high probability that the biopsy piece  76  will remain in the needle  10  and will be recovered as the needle is removed so long as efficient specimen transit has facilitated the passage of the specimen into the lumen of the snare and the inner tube. If the tightening of the snare  16  does not immediately cause the biopsy piece  76  to be cut, it will be significantly squeezed and/or notched, such that rearward motion of the needle  10 , which causes rearward pressure on any biopsy piece  76  proximal of the snare  16 , will cause material proximal of the snare  16  to detach from material that is distal of the snare.  
         [0040]     As can be seen in  FIG. 7 , the handle  22  includes several features designed for ease of use of the physician and ease of manufacture and construction. The handle piece  28  includes a groove  26  that holds the lever  24 . The groove  26  has two notches  78  that generally protect the lever  24  from any accidental contact with the physician when in either the full-open or full-closed positions, but allow access to the lever. Further, the holes in the handle piece  28  that receive the anchor  44  of the outer cannula and the stop  66  of the stylet have complementary shapes in order to prevent rotation of those two components with respect to the handle, as previously discussed. The proximal and distal facing sides  46 ,  52  of the handle piece are also provided with threaded regions for receiving the cannula and stylet caps  50 ,  56 .  
         [0041]     Once the biopsy needle  10  has captured a cored specimen, it must be recovered for pathologic interpretation. The lever is rotated opposite to the direction D, thereby opening up the coil to its original diameter. A obturator is placed through the tip of the needle and the specimen is pushed through the inner tube and through the handle for collection. As initial efficient specimen transit into the inner tube influences transit of the specimen through the remainder of the inner cannula during the specimen recovery phase of the procedure, maximizing the R value also positively influences specimen recovery. Once the specimen has been ejected and recovered, the biopsy needle  10  is then ready to be sterilized for its next use. If necessary, the entire biopsy needle can be disassembled, although the tab  72  at the free end of the snare must be disengaged from the hole  74  in the outer cannula. This can be accomplished with any small tool pushed through hole  74 . If the free end  70  of the snare is permanently adhered to the outer cannula  12 , it then may be necessary to sterilize the outer cannula and inner tube as a single unit. However, due to the few number of parts and relative ease and low cost of construction of the present needle, it is also contemplated that such a device is easily disposable.  
         [0042]      FIG. 6   b  shows another embodiment where the snare  16  is not located at the distalmost section of the inner tube  14  but instead is spaced slightly inward from the distal end. A distal end section  91  is provided and in this embodiment (as mentioned above), the inner tube  14  is not attached to the outer tube via a tab and opening but instead, the inner tube  14  can be attached by means of the distal end section  91 . It will be appreciated that the most distal inner diameter of the inner tube  14  at the most distal aspect of section  91 , designated as Id int , defines the ratio R=(!ID int )/(ID tip ) When the most distal portion of the inner tube  14  is the most distal portion of the snare  16 , the ratio is defined as (ID sc )/(ID tip ) since ID sc =ID int ; however, when a small portion (section  91 ) of the inner tube  14  is distally located relative to the snare  16 , the ratio R is =(ID int )/(ID tip ), where (ID int ) is the inner diameter of the most distal portion of the inner tube  14 . It will be appreciated that the distal end section  91  can have a diameter that is different than the diameter of the adjacent snare  16 .  
         [0043]     Thus, it can be seen that a low cost, simply-manufactured biopsy needle will attain improved results over known devices, not only in the success rate of the marrow extraction procedures, but also a marked increase in patient comfort throughout the procedure. High performance needles require not only efficient specimen capture but efficient specimen transit through the needle. One desirable side benefit of this increased comfort might be increased participation in bone marrow donor programs for transplant candidates.  
         [0044]     While the embodiments shown and described above are fully capable of achieving the objects and advantages of the present invention, it is to be understood that these embodiments are shown and described solely for the purposes of illustration and not for limitation.