Patent Publication Number: US-8523809-B2

Title: Device for shielding a sharp tip of a cannula and method of using the same

Description:
RELATED APPLICATIONS 
     This application is a divisional application under 35 U.S.C. 121 and claims the benefit to pending U.S. application Ser. No. 11/179,143 filed Jul. 11, 2005, entitled DEVICE FOR SHIELDING A SHARP TIP OF A CANNULA AND METHOD OF USING THE SAME, which is incorporated by reference in its entirety for all purposes. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to a safety device, and more particularly to a device for shielding a sharp tip of a tubular needle. 
     Needle assemblies have particular, although not exclusive application in the field of medicine and have tubular needles with sharpened ends for use in piercing the skin to withdraw materials as needed. The needle is supported by some other structure that is used to manipulate the needle. The most common example is a syringe. However, some needle assemblies require the application of substantial force in use. One example of such a needle assembly is a bone marrow needle assembly that is used to penetrate cortical bone to reach the intramedullary canal for withdrawing liquid or a biopsy sample of bore marrow, or for infusing the canal with a selected material. Typically, the needle includes a cannula and a stylet that is received in the cannula and has a hard, sharp tip that can penetrate cortical bone. The tip projects out from the distal end of the cannula. The stylet can be withdrawn from the cannula after the needle penetrates the bone so that the hollow interior of the cannula can be used as a conduit for liquid or a receptacle to collect bone marrow. 
     In order to penetrate cortical bone, a substantial amount of force must be applied to the needle. For this reason, bone needle assemblies conventionally mount the needle in a handle that is sized and shaped so that the technician may comfortably grip the handle and apply the force necessary to penetrate the bone. The handle may comprise two handle members that can be selectively put together and separated for inserting the stylet into the cannula and removing the stylet from the cannula. A proximal handle member mounts the stylet and a distal handle member mounts the cannula. “Proximal” and “distal” refer to the relative location of the handle members to the technician when the needle assembly is in use. The proximal handle member is in contact with the palm of the technician&#39;s hand in use, and the distal handle member is on the opposite side of the proximal handle member from the palm. 
     Some needle assemblies, including bone needle assemblies, have associated safety mechanisms that shield the sharp tips of the needle components when they are not needed and after they have become contaminated with potentially hazardous biological material. The safety mechanism includes a shield and usually a mechanism for locking the shield in place over the sharpened tip. As a matter of convenience, and to enhance the probability that the safety feature will be used by a medical technician, the safety feature may be secured to the needle assembly. However, the safety feature must be retained out of the way when the needle assembly is being used, for example, to collect a liquid or solid sample from the intramedullary canal. The safety feature then must be released from its stowed position and moved to an operative position in which its shield covers the sharpened tip of the needle. While effective, this safety feature adds cost to the needle assembly and requires a conscious effort to use. 
     In cases where a sample (e.g., a bone marrow sample) is collected by the needle assembly, the sample has to be removed from the needle assembly. An obturator is a device including a long thin shaft that can fit inside the cannula for pushing the sample of bone marrow out of the cannula. This can be done with the safety shield in position covering the sharp end of the cannula to protect the technician. In some cases it will be determined that the sample is not satisfactory and it will be necessary to obtain a second sample. It is not necessary to use a new needle assembly, because the needle assembly would be reused on the same patient. However, the shield is held in place over the tip of the needle assembly making it unusable for a collecting a second sample. Accordingly, there is a need for a needle assembly that can be easily reset for second use, but which will not result in inadvertent release of the safety shield. 
     SUMMARY OF THE INVENTION 
     In general, the present invention relates to a safety device for shielding a sharp tip of a cannula having an interior passage including first and second opposite ends. The safety device includes a shaft sized and shaped for being received into the passage of the cannula through the first end of the passage and extending to the second end of the passage. A shield associated with the shaft is constructed for receiving and substantially shielding the sharp tip of the cannula upon reception of the shaft in the cannula passage. A catch associated with the shaft is adapted to prevent withdrawal of the shaft from the passage of the cannula when the shaft is received in the passage in a position where the shield receives the sharp tip of the cannula. 
     In another aspect, a needle assembly for use in collecting samples of tissues and/or bodily fluids generally includes a cannula at least partially defining an interior passage including first and second ends. The passage is adapted to receive the tissue and/or bodily fluid sample. A shaft is sized and shaped for being received into the passage of the cannula through the first end of the passage and extending to the second end of the passage for use in removing a sample collected in the cannula. A shield associated with the shaft is constructed for receiving and substantially shielding the sharp tip of the cannula upon reception of the shaft in the cannula passage. A catch associated with the shaft is adapted to engage the needle assembly to prevent withdrawal of the shaft from the passage of the cannula when the shaft is received in the passage in a position where the shield receives the sharp tip of the cannula. 
     In yet another aspect, a method of shielding a sharp tip of a cannula at least partially defining an interior passage including first and second opposite ends includes collecting a sample of tissue and/or bodily fluid from a patient in the passage of the cannula. A shaft is inserted into the passage through the first end thereof pushes the sample out of the second end of the passage to collect the sample. The step of inserting includes shielding the sharp tip of the cannula with a shield when the shaft is inserted a predetermined distance into the cannula. The shaft is retained relative to the cannula against movement out of the passage through the first end holds the shield over the sharp tip. 
     Other objects and features will be in part apparent and in part pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective of a bone marrow needle assembly including a needle and an obturator of new construction; 
         FIG. 2  is an enlarged fragmentary perspective of the obturator of  FIG. 1 ; 
         FIG. 3  is a further enlarged fragmentary side elevation of the obturator of  FIG. 1  with a longitudinal portion of the a shield of the obturator broken away to reveal the interior; 
         FIG. 4  is an enlarged fragmentary elevation of the obturator of  FIG. 1  illustrating a catch on a shaft of the obturator in an extended position protruding laterally outward from the shaft; 
         FIG. 5  is the enlarged fragmentary elevation of  FIG. 4  but illustrating the catch in a retracted position; 
         FIG. 6  is a perspective of the shaft of the obturator of  FIG. 1  axially aligned with a passage of the needle of  FIG. 1 ; 
         FIG. 7  is an enlarged fragmentary elevation of the needle and obturator of  FIG. 6 , but showing the shaft of the obturator received partially in the needle; 
         FIG. 8  is a side elevation of a distal handle member and cannula of the needle assembly with the obturator fully inserted into the needle and parts of the needle shield broken away to show internal components; 
         FIG. 9  is an enlarged fragmentary elevation of the needle and shaft of  FIG. 8  with parts of the needle broken away; 
         FIG. 10  is an enlarged detail of the distal handle member, cannula and obturator of the needle assembly with parts broken away to illustrate the catch; 
         FIG. 11  is a fragmentary elevation of another embodiment of the obturator constructed according to the principles of the present invention; and 
         FIG. 12  is a fragmentary longitudinal section of the obturator of  FIG. 11 . 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the drawings. 
     DETAILED DESCRIPTION 
     Referring now to the drawings and in particular to  FIG. 1 , a medical instrument constructed according to the principles of the present invention is shown in the form of a bone needle assembly, generally indicated at  10 . The bone needle assembly includes a handle  12  (broadly, “mounting structure”) and a needle  14 , all reference numbers indicating their subjects generally. The needle  14  includes a stylet  18  and a cannula  20  that can receive the stylet. The handle  12  includes a first or proximal handle member (indicated generally at  22 ) mounting the stylet  18 , and a second or distal handle member (indicated generally at  24 ) mounting the cannula  20 . It will be understood that a needle could include only a single component part, or more than two parts within the scope of the present invention. Similarly, a handle could be a single part or more than two parts. The mounting structure for the needle  14  can be other than a handle without departing from the present invention. The needle assembly  10  further includes a safety device in the form of a modified obturator, generally indicated at  26 , constructed according to the teachings of the present invention. The modified obturator  26  may be used to shield a sharp tip  28  of the cannula  20 , as described more fully below, and may be used to remove a sample captured in the cannula. 
     The cannula  20  has a central axial passage extending the length of the cannula and an opening at both ends of the cannula. The distal tip  28  of the cannula  20  is beveled and sharpened. A proximal end portion of the cannula  20  is received in the distal handle member  24 , and the opening of the end portion extends through the handle. The stylet  18  is solid and includes a sharp distal tip  30 , and a proximal end portion received in the proximal handle member  22 . The stylet  18  can be inserted through the axial passage opening in the proximal end portion of the cannula  20 . The stylet  18  can be received entirely through the axial passage of the cannula so that its sharp distal tip projects axially outward from the distal tip  28  of the cannula. The stylet  18  provides the tool for penetrating the cortical bone, and can be removed from the cannula  20  once the intramedullary canal is accessed by the needle  14 . The stylet  18  and cannula  20  are preferably constructed from strong, generally rigid metal, although they may be constructed from other materials. 
     The handle  12  formed by the proximal and distal handle members  22 ,  24  has an ergonomic shape that can be comfortably received in a medical technician&#39;s hand, and allows the technician to easily control the needle assembly  10  as he or she applies the substantial forces needed to penetrate the bone. More specifically, the top or proximal surface  38  of the proximal handle member  22  is rounded in conformance with the shape of the palm of the hand. The bottom or distal surface  40  of the distal handle member  24  is also rounded, but is undulating in shape thereby forming finger wells  40 A for receiving the technician&#39;s fingers. The form of the handle can be other than described herein without departing from the scope of the present invention. The proximal and distal handle members  22 ,  24  can be connected together in a suitable manner when the stylet  18  is received in the cannula  20  (as illustrated in  FIG. 1 ), so that the handle  12  acts essentially as a single piece when used to drive the needle  14  through a patient&#39;s skin and into the bone. The proximal and distal handle members  22 ,  24  can be disconnected and moved apart for removing the stylet  18  from the cannula  20 . The handle is preferably constructed of plastic material, although it may be constructed of other material. 
     The needle assembly  10  is driven into the bone by grasping the handle  12  and pushing the stylet  18  through the skin, underlying tissue and cortical bone. Once this penetration has been achieved, the stylet  18  is no longer required. The proximal handle member  22  is disconnected from the distal handle member  24  and moved axially away from the distal handle member so that the stylet  18  slides out of the central axial passage of the cannula  20  while the cannula remains in the bone. In order to collect a sample of bone marrow, the distal handle member is advanced further into the bone. The sharp tip  28  of the cannula  20  cuts into the bone marrow and a sample is received in the central axial passage of the cannula. The cannula  20  can then be withdrawn from the patient by pulling on the distal handle member  24 . The sample should remain lodged in the central axial passage of the cannula  20  near the sharp tip  28 . It will be understood that a needle assembly may be used to collect a sample other than of bone marrow within the scope of the present invention. 
     Referring to  FIGS. 2 and 3 , the obturator  26  can be used to remove a lodged sample of bone marrow that has been collected in the central axial passage of cannula  20 . The obturator  26  includes a grip  45  that is sized and shaped to be grasped by a user for manipulating the obturator  26 , as will be described. A generally tubular shield  48  extends from the grip  45  and has a closed end associated with the grip, an opposite open end and an annular chamber  51  located generally between the ends. The grip  45  and the shield  48  are preferably integrally formed and constructed of a plastic material, although it is contemplated that the grip and shield may be formed separately and/or constructed of other material. As shown best in  FIG. 8 , a long, thin shaft  55  that is sized to be received in the central axial passage of the cannula  20  in a generally close fitting relation therein extends from the closed end of the tubular body of the shield  48  through the open end of the tubular body and is generally coaxial with the cylindrical chamber  51 . The shaft  55  is preferably constructed of rigid metal material, although other types of material may be used. The chamber  51  is sized and shaped for snugly receiving at least the sharp tip  28  of the cannula  20  of the needle  14  when the shaft  55  is received in the axial passage of the cannula. In the illustrated embodiment, a hematic absorbent body  57  is disposed within the chamber  51 . The absorbent body  57  surrounds the shaft  55 . The body  57  can be penetrated for receiving at least the tip  28  of the cannula  20  and is absorbent for absorbing biological fluids. In one embodiment, the absorbent body  57  can be made of an anti-microbial material to inhibit the growth of bacteria. The absorbent body  57  retains biological fluid, such as blood and other fluids that may flow out of the tip  28  of the cannula  20  within the shield  48 . The body  57  may be constructed of a sponge material or plastic-type material or any other material that is generally known in the art for use in absorbing biological fluid, and in particular, such fluid flowing from a needle. The absorbent body  57  may be formed in other ways or omitted within the scope of the present invention. 
     Referring to FIGS.  2  and  4 - 5 , a catch generally indicated at  60  is disposed on the shaft  55  of the obturator  26  generally adjacent the free end of the shaft. The catch  60  of the illustrated embodiment comprises a flap  62  connected to the shaft  55  so that the flap can pivot about an axis transverse to the shaft. The shaft  55  has a recess  65  sized and shaped to conformally receive the flap  62 . The flap  62  and the associated recess  65  is formed by cutting out a longitudinal segment of the shaft  55  while leaving an end opposite the free end of the flap attached to the shaft to form a living hinge  67 . The flap  62  is pivotable about the hinge  67  between an extended position ( FIG. 4 ), in which the flap projects generally laterally outward from the shaft  55 , and a retracted position ( FIG. 5 ), in which the flap is substantially received in the recess  65 . The exterior surface of the flap  62  and the exterior surface of the shaft  55  are generally flush when the flap is in the retracted position ( FIG. 5 ). In the illustrated embodiment, only a small portion of the flap  62  remains attached to the shaft  55 , and the flap is biased in the extended position. For reasons which will become apparent, the flap  62  is formed so that it is biased to pivot toward the free end of the shaft  55 . Also, the hinge  67  should be strong enough to withstand at least some repetitious pivoting of the flap  62 . As explained below, the length of the flap  62  and the angle at which the flap is biased to extend from shaft  55  is not crucial as long as the radial distance D ( FIG. 4 ) between the free end of the flap and the central axis of the shaft is somewhat greater than the radius of the opening of the axial passage of the cannula  20  at the proximal end. 
     It is contemplated that the flap  62  may be formed separate from the shaft  55  and attached thereto in a suitable fashion (not illustrated). For example, a flap may be attached to a shaft  55  by welding or by other ways form the living hinge, or the flap may be attached using a hinge other than a living hinge. For example, a spring hinge can be used to bias the flap or a non-biasing hinge may be used along with other ways of properly biasing the flap, such as a spring associated with the free end portion of the flap. Also, it is contemplated that a shaft may not have a recess for receiving the flap. Instead, the flap can comprise a thin sheet, preferably of metal, having inner face for contacting the surface of the shaft and an outer face. Both faces have the same shape and generally the same radius of curvature as the surface of the shaft such that the flap lies generally flush against the surface of the shaft when it is in its retracted position. Other ways of forming and using a flap of the present invention are contemplated and within the scope of this invention. 
     Referring to  FIG. 6 , the initial position of the obturator  26  with the free end of the shaft  55  aligned with the central axial passage of the cannula  20  at the tip  28  is shown. As explained above, the flap  62  is initially in the extended position (i.e., extending generally transversely from the shaft  55 ). As shown by directional arrow A in  FIGS. 6 and 7 , the grip  45  is pushed to advance the shaft  55  into the central axial passage, and as the shaft advances, the flap  62  contacts the tip  28  at its end including the living hinge  67 , forcing the flap to pivot or fold down toward the recess  65 . Eventually during the advancement of the shaft  55  within the cannula passage, the flap  62  is pushed by engagement with the cannula  20  to its retracted position whereby it is substantially received in the recess  65  and its outer surface is substantially flush with the outer surface of the shaft  55  of the obturator  26  (see e.g.,  FIG. 5 ). The flap  62  remains generally in the retracted position while inside the passage because of the generally tight fit between shaft  55  and the passage. The shaft  55  of the obturator  26  can continue to advance within the passage without significant impedance from the flap  62 . As the shaft  55  advances, it pushes the sample toward the opening at proximal end of the central axial passage and out of the cannula where it can be collected in a Petri dish or other suitable container. 
     Referring to  FIGS. 8-10 , as the shaft  55  advances in the central axial passage, the tip  28  of the cannula  20  enters the chamber  51  of the shield  48 . The tip  28  of the cannula  20  advances in the chamber  51  toward the grip  45  and penetrates into the hematic absorbent body  57  ( FIG. 9 ). The technician continues to advance the shaft  55  until the free end of the flap  62  exits the opening associated with the proximal end of the central axial passage ( FIG. 10 ). As shown in  FIG. 8 , the free end of the flap  62  preferably does not exit the passage until at least the tip  28  of the cannula  20  is received in the chamber  51  of the shield  48 . Also, the flap  62  should exit the opening associated with the proximal end of the passage before the tip  28  of the cannula  29  contacts the closed end of the shield  48 . 
     As shown best in  FIG. 10 , when the free end of the flap  62  exits the axial passage, it pivots towards the free end of the shaft  55  and into its extended position. In the extended position, the laterally extending flap  62  prevents the shaft  55  from withdrawing from the passage of the cannula  20  because the radial distance D between the free end of the flap and the longitudinal axis of the shaft is greater than the radius of the opening associated with the proximal end of the central axial passage. The flap  62  catches on the edge of the cannula  20  adjacent the opening associated with the proximal end of the central axial passage and cannot move back into the opening. This essentially secures the obturator  26  to the cannula  20 . It is envisioned that the flap  62  may engage structure other than the cannula  20  to secure the obturator  26  in place shielding the cannula tip  28 . For example, the flap  62  could engage a portion (not shown) of the distal handle member  24 . 
     The flap  62  should be disposed at a location on the shaft  55  of the obturator  26  such that the flap prevents removal of at least the tip  28  of the cannula  20  from the chamber  51  of the shield  48 . Thus, the appropriate location of the flap  62  along the length of the shaft  55  depends on the length of the shaft, the length of the passage of the cannula  20  and the length of the chamber  51 . Retaining the tip  28  of the cannula  20  within the chamber  51  of the shield  48  prevents the technician and others from being stuck by the tip. There may, and most likely will be, some limited longitudinal movement of the shaft  55  within the central axial passage of the cannula  20 . Limited movement is satisfactory as long as at least the tip  28  of the cannula  20  remains within the chamber  51  of the shield  48  while the flap  62  is in the extended position. 
     In one version of the present invention, the distal handle member  24  and flap  62  are constructed and arranged so that the flap is essentially not accessible when engaged with the distal handle member or cannula  20  at the proximal end of the central axial passageway of the cannula. Therefore, once the flap  62  is engaged, the tip  28  is securely and substantially irreversibly held in the chamber  51  of the shield  48 . It is also envisioned that the obturator  26  could be constructed so that it could be removed from the central axial passageway of the cannula  20 . For example, if the sample collected in the cannula  20  is not satisfactory it will be necessary to obtain a second sample. This can be done using the same needle assembly  10 . To allow a second use, the flap  62  and distal handle member  24  can be configured to permit access to the flap after it is engaged at the proximal end of the central axial passageway of the cannula  20 . The technician configures the flap  62  into the retracted position and retains it in such position. For example, the technician may hold the flap  62  in the recess  65  by pressing it down with his or her fingers or any other means by which the flap can be depressed such as a pair of forceps or other suitable instrument. The technician maintains the flap  62  in the retracted position as he or she withdraws the shaft  55  from the cannula passage. Once the free end of the flap  62  enters the opening associated with the proximal end of the central axial passage, it is no longer necessary to hold the flap in the retracted position, and the entire shaft  55  of the obturator can readily be withdrawn from the passage. The assembly  10  is then ready for a second use. 
     Referring now to  FIGS. 11 and 12 , another embodiment a safety device of the present invention is in the form of an obturator and is generally indicated at  126 . This embodiment is similar to the previous embodiment of  FIGS. 1-10 , and as such, corresponding components of the safety device will be indicated by corresponding reference numbers plus “100” for convenience. The difference between this embodiment and the previous embodiment of  FIGS. 1-10  is that the catch  160  of the present embodiment comprises an engaging member  162  at least partially received in a cavity  165  formed in the shaft  155  of the obturator  126  ( FIG. 12 ). The engaging member  162  is movable between an extended position, in which a protruding portion of the member extends laterally outward from the cavity  165 , and a retracted position in the member is substantially entirely received within the cavity. An outer surface of the protruding portion may be generally flush with the exterior surface of the shaft  155  when the engaging member  162  is in the retracted position. A leaf spring  175  disposed within the cavity  165  biases the engagement member  162  in the extended position. Other types of springs, such as a coil spring, are contemplated. A stop  178  disposed on the engagement member  162  retains a non-protruding portion of the member within the cavity  165 . In the illustrated embodiment, the protruding portion of the engagement member  162  has a first face  180 A facing the free end of the shaft  155  and an opposite second face  180 B facing the grip  145 . For reasons discussed below, the first face  180 A tapers away from the shaft  155  and the second face  180 B extends generally perpendicular to the shaft. 
     The obturator  126  of the present embodiment is used in substantially the same way as the previous embodiment. In the initial position of the obturator  126 , the engagement member  162  is configured in its extended position with the protruding portion of the engagement member extending laterally outward from the cavity  165 . The shaft  155  of the obturator  126  is inserted into the passage of the cannula  20  at the tip  28 . As the shaft  155  advances in the passage, the first face  180 A of the protruding portion of the engagement member  162  contacts the tip  28  of the cannula  28 . Because of the tapered first face  180 A, the engagement member  162  is forced into the cavity  165 , thereby compressing the spring  175 . As the shaft  155  advances, the engagement member  162  is forced substantially completely into the cavity  165  (i.e., in the retracted position) and the engagement member enters the passage. The engagement member  162  remains substantially completely within the cavity  165  in the retracted position as the shaft  155  advances within the passage, although a portion of the upper surface of the member may contact the wall of the passage. As with the previous embodiment, the tip  28  of the cannula  20  enters the chamber  151  of the shield  148  and the engagement member  162  exits the passage at the opening associated with the proximal end of the central axial passage. When the engagement member  162  exits, the spring  175  expands forcing the member out of the cavity  165  into the extended position. If the shaft  155  is moved in a direction withdrawing it from the central axial passage, the second face  180 B of the engagement member  162  engages the edge of the opening associated with the proximal end of the central axial passage and prevents withdrawal of the obturator  126  from the passage. To disassemble the assembly if, for example a second sample is needed as explained above, the technician forces the engagement member  162  back into the cavity  165  by, for example, pressing the member down with his or her fingers to compress the spring  175 . The shaft  155  can then be withdrawn from the passage. 
     When introducing elements of the present invention or the preferred embodiments(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained. 
     As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.