US20060276747A1 - Needle assembly with removable depth stop - Google Patents

Abstract

A needle assembly (10) includes a needle (14) attached to mounting structure (12), and is used to insert the needle into the body of a patient. A depth stop unit (50) of the needle assembly provides a stop surface (58) to limit the distance the needle can be inserted into the body. The depth stop unit may include a depth stop (52) that is adjustable to selectively change the depth to which the needle can be inserted. The entire depth stop unit can be removed from the needle assembly to permit the full length of the needle to penetrate into the body.

Description

CROSS REFERENCE TO RELATED APPLICATION
• This application includes subject matter in common with co-assigned U.S. patent application Ser. No. ______, entitled Bayonet Release of Safety Shield for Needle Tip, filed simultaneously herewith. The subject matter of this application is incorporated herein in its entirety by reference.
BACKGROUND OF THE INVENTION
• This invention relates generally to needles used in medicine and more particularly to a needle assembly having a depth stop to limit penetration of the needle into the subject, which depth stop can be selectively removed from the needle.
• In some medical applications needles are used to make relatively deep penetrations into the body in order to perform their tasks. For instance where it is necessary to obtain a biopsy sample, the needle may have to penetrate deep inside tissue to the location from which the sample is to be taken. However, there are also situations where the needle has to penetrate a substantial distance through tissue in order to inject a drug or withdraw fluid. One specific example is that of accessing the intramedullary canal of bone. This may be done to collect a specimen of bone marrow or fluid from the intramedullary canal. It is also possible that a drug or other fluid may be infused into the canal through the needle.
• To penetrate the hard cortical bone surrounding the intramedullary canal, the needle must be hard and strong, and substantial force has to be applied to the needle. The needle is typically mounted on a handle that can be grasped by a medical technician to supply the necessary force to penetrate the cortical bone to reach the intramedullary canal. It is important that the medical technician exercise care so that the needle is not driven elsewhere in the body other than the target bone. Depending upon the location of the bone selected for penetration, the bone may be near to organs or blood vessels that could be damaged by a misdirected needle. For example, if the needle penetrates too deeply, it could damage an untargeted area of the body. Thus, the use of a bone needle assembly of this type requires the simultaneous exercise of substantial force and precision.
• One way to reduce the chance that the needle will damage the body is to provide a depth stop that limits the depth of penetration of the needle into the body. Typically the depth stop is disposed around the needle below the handle and can engage the exterior of the body to stop the inward thrust of the needle. The depth stop reduces the length of the needle that is available for penetrating into the body. The appropriate depth of penetration can vary widely from one patient to the next. For example, an obese patient may require penetration of several inches of skin and soft tissue to reach the bone, while a thin patient requires very little penetration to reach the bone. Moreover, the location of the target bone may call for a different depth of penetration. To meet this need, depth stop units have been provided that permit the depth stop to be adjusted to expose a greater or lesser length of the needle for penetration into the body. While these adjustable depth stop units provide greater flexibility they do not fully meet the need for variability in needle length. Moreover, some procedures have less reason to use the depth stop than others. Medical technicians differ on their preference for use of needle assemblies incorporating depth stops.
• In instances where a depth stop is present in the needle assembly, a substantial length of the needle will never be available for use to penetrate into the body because it will remain covered by the depth stop. This is true even if the depth stop is adjusted to expose the maximum possible length of the needle for penetration. Accordingly, it is necessary to keep on hand multiple needle assemblies having different lengths and/or needle assemblies that do not have depth stops.
SUMMARY OF THE INVENTION
• In one aspect of the present invention, a convertible needle assembly generally comprises a mounting structure and a needle having a longitudinal axis and a sharp end, the needle being mounted on the mounting structure and projecting outwardly from the mounting structure so that the sharp end is generally remote from the mounting structure. A depth stop adapted to limit the depth of penetration of the needle is releasably connected by a rotary connector to the needle assembly. The released depth stop is removable from the needle for increasing the possible depth of penetration of the needle.
• In another aspect of the present invention, a bone needle assembly generally comprises a handle and a needle having a longitudinal axis and a sharp end. The needle is mounted on the handle at a location away from the sharp end of the needle and projects outwardly from the handle. A depth stop unit comprises a positioning stem and a depth stop mounted on the position stem and movable along a length of the stem to different selected positions along the stem and along the longitudinal axis of the needle. The depth stop has a stop surface adapted to limit the depth of penetration of the needle. A rotary connector of the depth stop unit is adapted to releasably connect the stem to the needle assembly. The rotary connector is capable of releasing connection of the stem so that the stem and depth stop may be removed from the needle for increasing the possible depth of penetration of the needle.
• In still another aspect of the present invention, a method of adjusting a permissible depth of penetration of a needle of a needle assembly generally comprises releasing a rotary connection of a depth stop unit to the needle assembly. The depth stop unit includes a depth stop positioned along a longitudinal axis of the needle and limiting the depth of penetration of the needle to a first depth. The depth stop unit is slid off of the needle to expose an additional length of the needle for penetration of the needle to a second depth greater than the first depth.
• Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a perspective of a bone needle assembly;
• FIG. 2 is the perspective ofFIG. 1 with a depth stop unit released from connection to the assembly;
• FIG. 3 is the perspective ofFIG. 2 with a depth stop unit moved off the needed assembly and exploded;
• FIG. 4 is a longitudinal section of the depth stop unit;
• FIG. 5 is an elevation of a threaded member of the depth stop unit;
• FIG. 6 is a front elevation of a distal handle member of the needle assembly;
• FIG. 7 is a left side elevation of the distal handle member with a portion of the distal handle member broken away and a cannula of the needle assembly removed;
• FIG. 8 is a front elevation of the distal handle member with the threaded member connected thereto; and
• FIG. 9 is a right side elevation of the distal handle member ofFIG. 8 with a portion of the handle member broken away and the cannula removed.
• Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.
DETAILED DESCRIPTION
• Referring now to the drawings and in particular toFIGS. 1-3, a bone needle assembly constructed according to the principles of the present invention is indicated generally at10. The bone needle assembly includes a handle12 (broadly, “mounting structure”), and aneedle14, all reference numbers indicating their subjects generally. Theneedle14 includes astylet18 and acannula20 that can receive the stylet. Thehandle12 includes a first or proximal handle member (indicated generally at22) mounting thestylet18, and a second or distal handle member (indicated generally at24) mounting thecannula20. “Proximal” and “distal” refer to the relative location of the handle members to a medical technician when the needle assembly is in use. Theproximal handle member22 is in contact with the palm of the technician's hand in use, and thedistal handle member24 is on the opposite side of the proximal handle member from the palm. 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. Moreover, the present invention has application to needle assemblies other than bone needle assemblies, and other than to needle assemblies having a depth stop. It is envisioned that the present invention also has use outside the field of needles.
• Thecannula20 has an axial passage extending the length of the cannula and opening at both ends of the cannula. Adistal tip28 of thecannula20 is beveled and sharpened. A proximal end portion of thecannula20 is received in thedistal handle member24. Thestylet18 is solid and includes a sharp distal tip32, and a proximal end portion received in theproximal handle member22. Thestylet18 can be inserted through the axial passage opening in the proximal end portion of thecannula20 and received entirely through the axial passage of the cannula so that its sharp distal tip32 projects axially outward from thedistal tip28 of the cannula. Thestylet18 provides the tool for penetrating the cortical bone, and can be removed from thecannula20 once the intramedullary canal is accessed by theneedle14.
• Thehandle12 formed by the proximal anddistal handle members22,24 has an ergonomic shape that can be comfortably received in a medical technician's hand, and allows the technician to easily control theneedle assembly10 as he or she applies the substantial forces needed to penetrate the bone. More specifically, the top orproximal surface38 of theproximal handle member22 is rounded in conformance with the shape of the palm of the hand. The bottom ordistal surface40 of thedistal handle member24 is also rounded but is undulating in shape thereby formingfinger wells40A for receiving the technician's fingers. The proximal anddistal handle members22,24 can be securely connected together when thestylet18 is received in thecannula20, so that thehandle12 acts essentially as a single piece when used to drive theneedle14 through a patient's skin and into the bone. The proximal anddistal handle members22,24 can be disconnected and moved apart for removing thestylet18 from thecannula20.
• To assemble theproximal handle member22 andstylet18 with thedistal handle member24 andcannula20, the sharp distal tip32 of the stylet is inserted into the central open portion of the distal handle member so that it enters the axial passage of the cannula. The proximal and distal handle members are turned from their aligned position to a position in which theproximal handle member22 is perpendicular to the distal handle member24 (not shown). When thehandle members22,24 are fully brought together, they are turned toward alignment with each other. This results in thehandle members22,24 being interconnected in the position illustrated inFIGS. 1 and 2. Thereafter, it will require nearly a 90 degree turn of theproximal handle member22 relative to thedistal handle member24 to disconnect these components. Accordingly, accidental separation of thehandle members22,24 in use is resisted.Wavy ribs46 on thedistal handle member24 are provided for gripping the distal handle member to disconnect and separate the distal handle member from theproximal handle member22. The wave shape of theribs46 suggests to the medical technician (because the ribs extend both around a longitudinal axis LA of the needle and along the needle axis) that first twisting and then axial movement is needed to achieve separation of theproximal handle member22 andstylet18 from thedistal handle member24 andcannula20.
• The proximal end portion of thestylet18 extends into the open center of theproximal handle member22, and is secured is a suitable manner to the proximal handle member. For instance, thehandle member22 may be molded around thestylet18 or the stylet may be attached to the proximal handle member by an adhesive. Theproximal handle member22 can be formed of polymeric or other material. Although shown as opaque in the drawings, thehandle member22 could be partially or totally transparent. A proximal end portion of thecannula20 extends into a tubular, projectingportion66 of thedistal handle member24 located at its center. Thecannula20 is mounted on thedistal handle member24 in a suitable manner. For instance, thedistal handle member24 may be molded around thecannula20 or the cannula may be adhered to the distal handle member. Thedistal handle member24 can be formed of polymeric or other suitable material. Although shown as opaque, thehandle member24 could be partially or totally transparent.
• Theneedle assembly10 further comprises a depth stop unit (broadly, “an operative member), generally indicated at50. The depth stop unit includes adepth stop52 that has a generallyconical portion54 with acylindrical nose56 projecting therefrom, calling to mind roughly the shape of a space capsule. Theconical portion54 has an annularbottom stop surface58 that is engageable with the body of the patient to limit the penetration depth of theneedle14 into the body. Ahub59 generally in the center of the bottom of thedepth stop52 is sized and shaped to receive and hold a tube (not shown) by a releasable interference fit. The tube covers the sharp ends28,32 of thecannula20 and stylet32, and is removed by pulling off of thehub59 prior to usage of theneedle assembly10.
• Thedepth stop unit50 further includes an elongate, tubular threaded member, indicated generally at60, on which thedepth stop52 is threadably mounted. The threadedmember60 has an axially extending passage61 (FIG. 3) that extends completely through the length of the threaded member. Thepassage61 receives theneedle14 through the threadedmember60. Referring toFIG. 5, the threadedmember60 includes apositioning stem62 havingthreads64. A connector (indicated generally at66) of the threadedmember60 comprises twoarms68 projecting upward from the positioning stem and having radially inwardly projectingfingers70 at their free ends. Thearms68 are located on diametrically opposite sides of the threadedmember60. Theconnector66 can releasably attach the threadedmember60 and depth stop52 to thedistal handle member24, as will be described more fully hereinafter. Although thepositioning stem62 andconnector66 are shown as one piece, a connector could be formed separate from the positioning stem. Moreover, thepositioning stem62 could be eliminated and theconnector66 could directly attach thedepth stop52 to thedistal handle member24 without departing from the scope of the present invention.
• As shown inFIG. 4, thedepth stop52 has anaxially extending passage74 extending through the entire length of the depth stop and including alarger diameter portion74A and asmaller diameter portion74B at its bottom end (as oriented inFIG. 4). Thelarger diameter portion74A receives the positioning stem62 of the threadedmember60 into the depth stop. Thesmaller diameter portion74B allows theneedle14 to pass out of thedepth stop52. Thelarger diameter portion74A hasthreads76 that mate with thethreads64 of thepositioning stem62. Rotation of thedepth stop52 about a longitudinal axis of the threaded member60 (which generally coincides with the longitudinal axis LA of the needle14) in the direction indicated by arrow Al inFIG. 1 causes the depth stop to move relative to thepositioning stem62 toward a distal end of the threaded member. Rotation of thedepth stop52 on thepositioning stem62 in the opposite direction indicated by arrow A3 inFIG. 1 causes the depth stop to move toward the proximal end of the threadedmember60. Movement toward the distal end of the threadedmember60 has the effect of shortening the length of theneedle14 located between sharpeneddistal tips28,32 of thecannula20 andstylet18 and thestop surface58 of thedepth stop52. The possible depth of penetration of theneedle14 into the body is therefore reduced. Moving thedepth stop52 toward the proximal end of the threadedmember60 increases the length of theneedle14 located between the sharpenedtips28,32 and thestop surface58 of thedepth stop52. The possible depth of penetration of theneedle14 into the body is therefore increased. Thus by rotating thedepth stop52 on thepositioning stem62, a particular limited depth of penetration of theneedle14 into the body of the patient can be selected. Among other things, this can prevent theneedle14 overshooting its target bone and inadvertently damaging another area inside the body.
• The adjustment of thedepth stop52 along the length of the threadedmember60 allows considerable variance in the effective length of theneedle14 and selected depth of penetration. However, in some instances it will be necessary or desirable to employ substantially the full length of theneedle14 projecting outward from thetubular portion66 of thedistal handle member24 to reach the target bone. Thedepth stop unit50 can be removed from theneedle assembly10 by disconnecting the threadedmember60 from thedistal handle member24.
• The threadedmember60 is attached to thedistal handle member24 by thefingers70 of thearms68 being received in circumferentially extendingslots80 formed in a projecting tubular portion (generally indicated at82) of the distal handle member (see,FIGS. 7 and 9). Thetubular portion82 includes ahole83 that receives the cannula20 (removed inFIGS. 7 and 9) and allows for passage of thestylet18 into the cannula. A threaded member or depth stop could be attached at other locations on a needle assembly without departing from the scope of the present invention. Theslots80 each are open on one circumferential end of the slot and include anend wall84 on the other end of the slot. Theend wall84 locates thefingers70 and positions the threadedmember60 relative to thehandle12. Thefingers70 andslots80 are shaped for retaining the fingers in the slots thereby to prevent inadvertent disconnection of the threaded member from thedistal handle member24. More specifically, each of thefingers70 has atriangular recess70A located generally in the center of the finger. Eachslot80 has a correspondingtriangular projection80A in the center of the slot.
• When thetriangular projections70A are received in thetriangular recesses80A, the threadedmember60 is held against rotation relative to thetubular portion82 of the distal handle member24 (FIGS. 1 and 9). Thus, the threadedmember60 is prevented from inadvertent disconnection from thedistal handle member24. By applying sufficient force, the interlocked connection of thetriangular recesses70A andtriangular projections80A can be overcome to release the threadedmember60 from thedistal handle member24. To connect the threadedmember60 to thedistal handle member24, the threaded member is rotated in a direction opposite arrow A3 from itsFIG. 2 position back to itsFIG. 1 position. A tapered leadingedge portion70B of eachfinger70 first enters itsrespective slot80 and eventually engages thetriangular projection80A. The tapered shape of theleading edge portion70B allows eacharm68 to be resiliently deflected by a small amount in a radially outward direction with respect to the longitudinal axis LA of theneedle14. As the threadedmember60 continues to be rotated, eachtriangular recess70A is eventually brought into registration with the correspondingtriangular projection80A. The resilience of the material of thearms74 forces therecesses70A down onto thetriangular projections80A so that the projections are partially received in the recesses to retain the connection. The technician will experience a tactile or audible snap as a result of this registering event that confirms the threadedmember60 is secured in place. By applying sufficient torque in the direction of arrow A3, thefingers76 can rotate to move thetriangular recesses70A off of thetriangular projections80A through deflection of the arms78. It will be understood that the shape of a projection and recess may be other than triangular. Moreover, the projection could be on a finger and a recess could be in a slot of a handle. Still further, the retention feature could be omitted within the scope of the invention.
• To release the threadedmember60, and hence thedepth stop unit50 from connection with thedistal handle member24, the connector66 (and hence the entire threaded member60) is rotated about 90 degrees in the direction indicated by arrow A3 from its connected position shown inFIG. 1 to a release position shown inFIG. 2. Rotation of theconnector66 moves thefingers70 out of theslots80 so that thedepth stop unit50 is no longer connected to thedistal handle member24. The connection may be described as “bayonet”. However, it will be understood that other types of connections, including non-rotary connections may be used within the scope of the present invention. Generally speaking, a quick release connection is desirable (but not mandatory in the present invention). For rotary connections, it is desirable to release connection with less than a 360 degree turn of the connector and more desirable to require a turn of less than 180 degrees to release connection. The bayonet connection illustrated in the drawings requires only about a 90 degree turn to achieve both connection and disconnection. Connection can be made by turning theconnector66 of the threadedmember60 from the position inFIG. 2 back to the position ofFIG. 1.
• Once the threadedmember60 is disconnected from thedistal handle member24 by this motion, thedepth stop unit50 can freely slide down theneedle14 and off of its distal end so that the depth stop unit is entirely removed from theneedle assembly10, as is illustrated inFIG. 3. The entire length of theneedle14 projecting outwardly from thetubular portion82 is now available for penetrating into the body of the patient to the target bone. If desired, thedepth stop unit50 can be reattached to theneedle14 because the disconnection is non-destructive.
• Generally circumferentially extendingribs88 are located on thedepth stop52 at the intersection of theconical portion54 and thecylindrical portion56. It will be understood that ribs (not shown) could be placed at other locations, such as on thearms68 of the threadedmember60. Theribs88 are spaced apart axially of each other along the longitudinal axis of the threadedmember60. The wave shape of theribs88 suggests by its circumferential extent that removal of thedepth stop unit50 requires rotary motion about the axis of the threadedmember60 andneedle14. The axial extent of theribs88 suggests a second movement along the axis is needed. These provide indications to the medical technician of how to release thedepth stop unit50 and then slide it off of the needle assembly.
• When introducing elements of the present invention or the preferred embodiment(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. Moreover, the use of “up”, “down”, “top” and “bottom” and variations of these terms is made for convenience, but does not require any particular orientation of the components.
• As various changes could be made in the above 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.

Claims (20)

1. A convertible needle assembly (10) comprising:

a mounting structure (12);

a needle (14) having a longitudinal axis and a sharp end (28,32), the needle being mounted on the mounting structure and projecting outwardly from the mounting structure so that the sharp end is generally remote from the mounting structure;

a depth stop (52) adapted to limit the depth of penetration of the needle;

a rotary connector (66) adapted to releasably connect the depth stop to the needle assembly, the released depth stop being removable from the needle for increasing the possible depth of penetration of the needle.

2. A convertible needle assembly as set forth inclaim 1 wherein the rotary connector (66) is constructed to connect to the mounting structure (12) by making a turn in a first direction about an axis that is less than 360 degrees, and to release from the mounting structure by making a turn in a second direction opposite the first direction about the axis that is less than 360 degrees.

3. A convertible needle assembly as set forth inclaim 2 wherein the rotary connector (66) is constructed to connect to the mounting structure (12) and release from the mounting structure by making turns in the first and second directions, respectively, that are less than 180 degrees.

4. A convertible needle assembly as set forth inclaim 2 wherein the rotary connector (66) is constructed to connect to the mounting structure (12) and release from the mounting structure by making turns in the first and second directions, respectively, that are about 90 degrees

5. A convertible needle assembly as set forth inclaim 4 wherein the rotary connector (66) and mounting structure (12) are constructed for bayonet connection of the rotary connector to the mounting structure.

6. A convertible needle assembly as set forth inclaim 5 wherein the mounting structure (12) comprises a pair of slots (80) and the rotary connector includes a pair of fingers (70) adapted to be received in the slots.

7. A convertible needle assembly as set forth inclaim 6 wherein at least one of the slots (80) and the fingers (70) includes retention structure (70A,80A) to resist relative rotation between the rotary connector (66) and the handle (12).

8. A convertible needle assembly as set forth inclaim 7 wherein the retention structure comprises a projection (80A) located in the slot (80) and a recess (70A) located on the finger (70), the projection being adapted to snap into the recess to provide a tactile confirmation of engagement.

9. A convertible needle assembly as set forth inclaim 1 wherein the rotary connector (66) mounts the depth stop (52) for selective positioning along the length of the needle (14) to change the depth limit of penetration.

10. A convertible needle assembly as set forth inclaim 9 wherein the rotary connector (66) is elongate and has threads (64) along its length, the depth stop (52) having threads (76) mated with the threads of the rotary connector and being rotatable on the rotary connector for selective positioning along the length of the needle (14).

11. A convertible needle assembly as set forth inclaim 10 wherein the rotary connector (66) and depth stop (52) are conjointly removable from the needle (14).

12. A bone needle assembly (10) comprising:

a handle (12);

a needle (14) having a longitudinal axis and a sharp end (28,32), the needle being mounted on the handle at a location away from the sharp end of the needle and projecting outwardly from the handle;

a depth stop unit (50) comprising a positioning stem (62), a depth stop (52) mounted on the position stem and movable along a length of the stem to different selected positions along the stem and along the longitudinal axis of the needle, the depth stop having a stop surface (58) adapted to limit the depth of penetration of the needle, and a rotary connector (66) adapted to releasably connect the stem to the needle assembly, the rotary connector being capable of releasing connection of the stem so that the stem and depth stop may be removed from the needle for increasing the possible depth of penetration of the needle.

13. A bone needle assembly as set forth inclaim 12 wherein the rotary connector (66) is constructed to connect to the handle (12) by making a turn in a first direction about an axis that is less than 360 degrees, and to release from the handle by making a turn in a second direction opposite the first direction about the axis that is less than 360 degrees.

14. A bone needle assembly as set forth inclaim 13 wherein the rotary connector (66) is constructed to connect to the handle (12) and release from the handle by making turns in the first and second directions, respectively, that are about 90 degrees.

15. A bone needle assembly as set forth inclaim 14 wherein the handle (12) includes a pair of slots (80) and the rotary connector (66) includes a pair of fingers (70) adapted to be received in the slots.

16. A bone needle assembly as set forth inclaim 12 wherein the rotary connector (66) and positioning stem (62) are formed as one piece (60).

17. A bone needle assembly as set forth inclaim 16 wherein the positioning stem (62) is elongate and has threads (64) along its length, the depth stop (52) having threads (76) mated with the threads of the positioning stem and being rotatable on the positioning stem for selective positioning along the length of the needle (14).

18. A method of adjusting a permissible depth of penetration of a needle (14) of a needle assembly (10) comprising:

releasing a rotary connection of a depth stop unit (50) to the needle assembly, the depth stop unit including a depth stop (52) positioned along a longitudinal axis of the needle and limiting the depth of penetration of the needle to a first depth;

sliding the depth stop unit off of the needle to expose an additional length of the needle for penetration of the needle to a second depth greater than the first depth.

19. A method as set forth inclaim 18 wherein the step of releasing connection of the depth stop unit (50) comprises rotating a rotary connector (66) attaching the depth stop unit to the needle assembly (10) less than 360 degrees relative to the needle assembly.

20. A method as set forth inclaim 19 wherein the step of releasing the connection of the depth stop unit (50) comprises rotating the rotary connector (66) about 90 degrees relative to the needle assembly (10).

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