Intraosseous stylet tip shield

Abstract

An access assembly for use with an intraosseous access device includes a safety mechanism to prevent needle stick injuries. In an example, the access assembly includes a needle supported by a needle hub, and a stylet supported by a stylet hub, wherein the stylet engages the needle lumen and includes a recess disposed a longitudinal length from a distal tip of the stylet. The access assembly further includes a plate shield comprising a housing slidably engaged with the needle hub, and a plate with an aperture and a plurality of fingers angled towards the distal end of the housing. The plate shield provides protection and stability during insertion and removal of the intraosseous access device, thereby ensuring safe and efficient access to the bone marrow without any needle stick injuries.

Description

INTRAOSSEOUS STYLET TIP SHIELDPRIORITY

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 540,863, filed September 27, 2023, which is incorporated by reference in its entirety into this application.BACKGROUND

[0002] Access assemblies for intraosseous (“I.O. ”) access devices provide a secure and efficient means of accessing the bone marrow for medical procedures and are often used in emergency situations where venous access is not viable. These access assemblies typically include an access needle defining a lumen, and a stylet or obturator disposed within the needle lumen to mitigate coring and occlusion of the needle lumen as the needle is drilled through tissues and bone. Once the access needle is placed, the stylet can be removed and discarded.

[0003] While stylets are not intentionally provided with a distal cutting edge, the tip of the stylet is ground flush with the bevel of the needle to prevent any pockets forming that might collect bone fragments and the like. This results in a sharpened tip that requires a tip safety mechanism to prevent accidental needle stick injuries once the stylet is removed from the needle. Problems can occur when certain needle safety mechanisms fail to deploy. Certain designs of safety mechanism fail to engage as the stylet is removed from the intraosseous needle, post placement. Further some designs of stylet safety mechanisms are complex to manufacture leading to increased costs.

[0004] What is needed therefore is a safety mechanism that addresses the foregoing.SUMMARY

[0005] In some aspects, the techniques described herein relate to an access assembly for use with an intraosseous access device including, a needle defining a lumen and supported by a needle hub, a stylet configured to slidably engage the needle lumen and supported by a stylet hub, the stylet including a recess extending annularly and disposed a longitudinal length (LI) from a distal tip of the stylet, the recess defining a diameter that is less than an outer diameter of the stylet, and a plate shield including, a housing defining a lumen and slidably engaged with a proximal end of the needle hub, the housing defining a distal opening and aproximal opening, and a plate engaged with the proximal opening and defining an aperture, the plate including a plurality of fingers extending radially inwards into the aperture, the plurality of fingers angled towards a distal end of the housing.

[0006] In some aspects, the techniques described herein relate to an access assembly, wherein each finger of the plurality of fingers extends radially inward to a tip of the finger, the tips of the plurality of fingers define a diameter (d4) that is equal to or less than an outer diameter of the stylet and equal to or greater than the diameter of the recess.

[0007] In some aspects, the techniques described herein relate to an access assembly, wherein a longitudinal distance between the plate and the distal opening is greater than the longitudinal length (Z7).

[0008] In some aspects, the techniques described herein relate to an access assembly, wherein the plurality of fingers elastically deform radially outwards to slidably engage a portion of the stylet therebetween.

[0009] In some aspects, the techniques described herein relate to an access assembly, wherein the plurality of fingers are configured to engage the recess and prevent movement of the housing relative to a distal tip of the stylet.

[0010] In some aspects, the techniques described herein relate to an access assembly, wherein a diameter of the distal opening is equal to or slightly larger than the outer diameter of the stylet such that the distal opening slidably engages the stylet.

[0011] In some aspects, the techniques described herein relate to an access assembly, wherein the housing includes a groove extending annularly about an inner surface of the housing adjacent the proximal opening, a diameter of the groove being greater than an inner diameter of the housing and equal to an outer diameter of the plate such that the plate engages the groove in a snap fit engagement.

[0012] In some aspects, the techniques described herein relate to an access assembly, wherein the housing engages the needle hub in an interference fit, press fit, or snap fit engagement.

[0013] In some aspects, the techniques described herein relate to a method of disengaging a stylet from an access needle including, sliding a stylet proximally from a lumenof the access needle, sliding the stylet through an aperture disposed in a plate, the plate including a plurality of fingers extending radially inwards into the aperture and angled distally, the plate engaged adjacent a proximal opening of a housing, slidably engaging a tip of a finger of the plurality of fingers with the stylet to engage a recess disposed on the stylet, and impinging the tip in the recess to prevent further longitudinal movement of the stylet relative to the housing, a distal tip of the stylet disposed within the housing.

[0014] In some aspects, the techniques described herein relate to a method, wherein the plurality of fingers extend radially inward to define a diameter (d4) that is equal to or less than an outer diameter of the stylet and equal to or greater than the diameter of the recess.

[0015] In some aspects, the techniques described herein relate to a method, wherein a longitudinal distance between the plate and a distal opening of the housing is greater than a longitudinal length (LI) between the recess and the distal tip of the stylet.

[0016] In some aspects, the techniques described herein relate to a method, wherein the plurality of fingers elastically deform radially outwards to slidably engage a portion of the stylet therebetween.

[0017] In some aspects, the techniques described herein relate to a method, wherein the plurality of fingers engage the recess and prevent movement of the housing relative to a distal tip of the stylet.

[0018] In some aspects, the techniques described herein relate to a method where a diameter of the distal opening is equal to or slightly larger than an outer diameter of the stylet such that the distal opening slidably engages the stylet.

[0019] In some aspects, the techniques described herein relate to a method, wherein the housing includes a groove extending annularly about an inner surface of the housing adjacent the proximal opening, a diameter of the groove being greater than an inner diameter of the housing and equal to an outer diameter of the plate such that the plate engages the groove in a snap fit engagement.

[0020] In some aspects, the techniques described herein relate to a method where the housing engages a needle hub of the access needle in an interference fit, press fit, or snap fit engagement.

[0021] In some aspects, the techniques described herein relate to an access assembly for use with an intraosseous access device including, a needle defining a lumen and supported by a needle hub, a stylet configured to slidably engage the needle lumen and supported by a stylet hub, the stylet including a recess extending annularly and disposed a longitudinal length (LI) from a distal tip of the stylet, the recess defining a diameter that is less than an outer diameter of the stylet, and a spring shield transitionable between a locked position and an unlocked position, the spring shield including, a top plate defining a top plate aperture and extending perpendicular to the stylet, a portion of the stylet extending through the top plate aperture, a first side arm extending from the top plate and including a first base plate defining a first base plate aperture, a second side arm extending from the top plate and including a second base plate defining a second base plate aperture, a first hook extending from a first side of the top plate aperture, and a second hook extending from a second side of the top plate aperture.

[0022] In some aspects, the techniques described herein relate to an access assembly, wherein in the unlocked position the top plate aperture, the first base plate aperture, and the second base plate aperture are aligned with a central longitudinal axis, and in the locked position the first base plate aperture and the second base plate aperture are misaligned with the central longitudinal axis.

[0023] In some aspects, the techniques described herein relate to an access assembly, wherein a first lateral distance between the first hook and the second hook is less than an outer diameter of the stylet and equal to or greater than a diameter of the recess.

[0024] In some aspects, the techniques described herein relate to an access assembly, wherein in the locked position, the first hook and the second hook move radially inward to a second lateral distance that is less than the first lateral distance, the second lateral distance being equal to or less than the diameter of the recess.

[0025] In some aspects, the techniques described herein relate to an access assembly, wherein the first hook and the second hook are configured to engage the recess and prevent further proximal movement between the stylet and the spring shield.

[0026] In some aspects, the techniques described herein relate to an access assembly, wherein the first hook and the second hook are disposed at a longitudinal distance from the first base plate and the second base plate that is greater than the longitudinal length (LI).

[0027] In some aspects, the techniques described herein relate to an access assembly, wherein the first side arm and the second side arm are biased to the locked position and elastically deformed to the unlocked position, a portion of the stylet disposed in the first base plate aperture and the second base plate aperture retaining the spring shield in the unlocked position.

[0028] In some aspects, the techniques described herein relate to an access assembly, wherein in the locked position a distal tip of the stylet impinges on one of the first base plate and the second base plate to prevent distal movement of the stylet relative to the spring shield.

[0029] In some aspects, the techniques described herein relate to an access assembly, wherein the spring shield engages the needle hub in an interference fit, press fit, or snap fit engagement.

[0030] In some aspects, the techniques described herein relate to a method of disengaging a stylet from an access needle supported by an access needle hub having a spring shield retained therein, the method including, sliding a stylet proximally from a lumen of the access needle, sliding the stylet through a top plate aperture, a first base plate aperture, and a second base plate aperture of the spring shield, engaging a recess disposed on the stylet with one of a first hook and a second hook of the spring shield to prevent further proximal movement of the stylet relative to the spring shield, urging the stylet proximally to disengage the spring shield from the access needle hub, and transitioning a first arm and a second arm from an unlocked position to a locked position, the first arm supporting a first base plate that defines the first base plate aperture, the second arm supporting a second base plate that defines the second base plate aperture.

[0031] In some aspects, the techniques described herein relate to a method, wherein transitioning the first arm and the second arm to the locked position misaligns the first base plate aperture and the second base plate aperture with a central longitudinal axis of the stylet, a distal tip of the stylet impinging on one or both of the first base plate and the second base plate to prevent distal movement of the stylet relative to the spring shield.

[0032] In some aspects, the techniques described herein relate to a method, wherein transitioning the first arm and the second arm to the locked position further includes transitioning the first hook and the second hook to a second lateral position, less than a first lateral position and equal to or less than an outer diameter of the recess.

[0033] In some aspects, the techniques described herein relate to a method, wherein in the unlocked position the top plate aperture, the first base plate aperture, and the second base plate aperture are aligned with a central longitudinal axis, and in the locked position the first base plate aperture and the second base plate aperture are misaligned with the central longitudinal axis.

[0034] In some aspects, the techniques described herein relate to a method, wherein a first lateral distance between the first hook and the second hook is less than an outer diameter of the stylet and equal to or greater than a diameter of the recess.

[0035] In some aspects, the techniques described herein relate to a method, wherein in the locked position, the first hook and the second hook move radially inward to a second lateral distance that is less than the first lateral distance, the second lateral distance being equal to or less than the diameter of the recess.

[0036] In some aspects, the techniques described herein relate to a method, wherein the first hook and the second hook engage the recess and prevent further proximal movement between the stylet and the spring shield.

[0037] In some aspects, the techniques described herein relate to a method, wherein first hook and the second hook are disposed at a longitudinal distance from the first base plate and the second base plate that is greater than a longitudinal length (LI) between the recess and a distal tip of the stylet.

[0038] In some aspects, the techniques described herein relate to a method, wherein the first arm and the second arm are biased to the locked position and elastically deformed to the unlocked position, a portion of the stylet disposed in the first base plate aperture and the second base plate aperture retaining the spring shield in the unlocked position.

[0039] In some aspects, the techniques described herein relate to a method, wherein in the locked position a distal tip of the stylet impinges on one of the first base plate and the second base plate to prevent distal movement of the stylet relative to the spring shield.

[0040] In some aspects, the techniques described herein relate to a method, wherein the spring shield engages the access needle hub in an interference fit, press fit, or snap fit engagement.

[0041] In some aspects, the techniques described herein relate to an access assembly for use with an intraosseous access device including, a needle defining a lumen and supported by a needle hub, a stylet configured to slidably engage the needle lumen and supported by a stylet hub, the stylet including a recess extending annularly and disposed a longitudinal length (LI) from a distal tip of the stylet, the recess defining a diameter that is less than an outer diameter of the stylet, and a cylinder shield transitionable between a locked position and an unlocked position, the cylinder shield including, a body defining a first edge, a second edge, a third edge and a fourth edge, the body defining a cylindrical shape where the first edge, disposed opposite the second edge, overlaps the second edge, and an end plate extending from the third edge perpendicular to the body and extending radially inward an inner edge of the end plate defining an aperture, the end plate aperture in the locked position defines a relatively smaller aperture than the end plate aperture in the unlocked position.

[0042] In some aspects, the techniques described herein relate to an access assembly, wherein the cylinder shield is biased towards the locked position and is retained in the unlocked position by a portion of the stylet disposed within the end plate aperture.

[0043] In some aspects, the techniques described herein relate to an access assembly, wherein the cylinder shield is biased towards the unlocked position and is retained in the locked position by a biasing member encircling an outer surface of the body.

[0044] In some aspects, the techniques described herein relate to an access assembly, wherein the biasing member is a rubber O-ring.

[0045] In some aspects, the techniques described herein relate to an access assembly, wherein the cylinder shield is configured to transition to the locked position when the end plate aperture is aligned with the recess.

[0046] In some aspects, the techniques described herein relate to an access assembly, wherein a longitudinal distance between the third edge and the fourth edge is greater than the longitudinal length (LI).

[0047] In some aspects, the techniques described herein relate to a method of disengaging a stylet from an access needle supported by an access needle hub having a cylinder shield retained therein, the method including, sliding a stylet proximally from a lumen of the access needle, sliding the stylet through an end plate aperture defined by an end plate extendingperpendicular to a body that defines a cylinder, the body having a first edge overlapping a second edge, transitioning the body to a locked position where the end plate aperture defines a relatively smaller diameter, engaging a recess disposed on the stylet with the end plate aperture to prevent further movement of the stylet relative to the cylinder shield, and urging the stylet proximally to disengage the cylinder shield from the access needle hub.

[0048] In some aspects, the techniques described herein relate to a method, wherein the body defining the first edge and the second edge, the first edge disposed opposite the second edge, further includes a third edge disposed opposite a fourth edge, the body defining a cylindrical shape where the first edge overlaps the second edge.

[0049] In some aspects, the techniques described herein relate to a method, wherein the end plate extends from the third edge and wherein a longitudinal length between the third edge and the fourth edge is greater than a longitudinal length (LI) extending between the recess and a distal tip of the stylet.

[0050] In some aspects, the techniques described herein relate to a method, wherein the cylinder shield is biased towards the locked position and is retained in an unlocked position by a portion of the stylet disposed within the end plate aperture.

[0051] In some aspects, the techniques described herein relate to a method, wherein the cylinder shield is biased towards an unlocked position and is retained in the locked position by a biasing member encircling an outer surface of the body.

[0052] In some aspects, the techniques described herein relate to a method, wherein the biasing member is a rubber O-ring.

[0053] In some aspects, the techniques described herein relate to a method, wherein the cylinder shield transitions to the locked position when the end plate aperture is aligned with the recess.

[0054] In some aspects, the techniques described herein relate to a method, wherein a longitudinal distance between a third edge and a fourth edge is greater than a longitudinal length (LI) between the recess and a distal tip of the stylet.BRIEF DESCRIPTION OF DRAWINGS

[0055] A more particular description will be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. Example embodiments of the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0056] FIG. 1 A shows an exploded view of an exemplary intraosseous access system, wherein an access assembly subset of the system is depicted slightly enlarged and in elevation, and a driver component is depicted in perspective, in accordance with embodiments disclosed herein.

[0057] FIGS. 1B-1C show an exemplary method of use for the intraosseous access system of FIG. 1 A, in accordance with embodiments disclosed herein.

[0058] FIGS. 2A-2C show various details of an embodiment of a shield for use with an access assembly, in accordance with embodiments disclosed herein.

[0059] FIGS. 2D-2E show an exemplary method of use for the shield of FIG. 2A, in accordance with embodiments disclosed herein.

[0060] FIGS. 3 A-3D show various details of an embodiment of a shield for use with an access assembly, in accordance with embodiments disclosed herein.

[0061] FIGS. 3E-3F show an exemplary method of use for the shield of FIG. 3A, in accordance with embodiments disclosed herein.

[0062] FIGS. 4A-4D show various details of an embodiment of a shield for use with an access assembly, in accordance with embodiments disclosed herein.

[0063] FIGS. 4E-4F show an exemplary method of use for the shield of FIG. 4A, in accordance with embodiments disclosed herein.DESCRIPTION

[0064] Before some particular embodiments are disclosed in greater detail, it should be understood that the particular embodiments disclosed herein do not limit the scope of theconcepts provided herein. It should also be understood that a particular embodiment disclosed herein can have features that can be readily separated from the particular embodiment and optionally combined with or substituted for features of any of a number of other embodiments disclosed herein.

[0065] Regarding terms used herein, it should also be understood the terms are for the purpose of describing some particular embodiments, and the terms do not limit the scope of the concepts provided herein. Ordinal numbers (e.g., first, second, third, etc.) are generally used to distinguish or identify different features or steps in a group of features or steps, and do not supply a serial or numerical limitation. For example, “first,” “second,” and “third” features or steps need not necessarily appear in that order, and the particular embodiments including such features or steps need not necessarily be limited to the three features or steps. Labels such as “left,” “right,” “top,” “bottom,” “front,” “back,” and the like are used for convenience and are not intended to imply, for example, any particular fixed location, orientation, or direction. Instead, such labels are used to reflect, for example, relative location, orientation, or directions. Singular forms of “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.

[0066] With respect to “proximal,” a “proximal portion” or a “proximal end portion” of, for example, a needle disclosed herein includes a portion of the needle intended to be near a clinician when the needle is used on a patient. Likewise, a “proximal length” of, for example, the needle includes a length of the needle intended to be near the clinician when the needle is used on the patient. A “proximal end” of, for example, the needle includes an end of the needle intended to be near the clinician when the needle is used on the patient. The proximal portion, the proximal end portion, or the proximal length of the needle can include the proximal end of the needle; however, the proximal portion, the proximal end portion, or the proximal length of the needle need not include the proximal end of the needle. That is, unless context suggests otherwise, the proximal portion, the proximal end portion, or the proximal length of the needle is not a terminal portion or terminal length of the needle.

[0067] With respect to “distal,” a “distal portion” or a “distal end portion” of, for example, a needle disclosed herein includes a portion of the needle intended to be near or in a patient when the needle is used on the patient. Likewise, a “distal length” of, for example, the needle includes a length of the needle intended to be near or in the patient when the needle is used on the patient. A “distal end” of, for example, the needle includes an end of the needleintended to be near or in the patient when the needle is used on the patient. The distal portion, the distal end portion, or the distal length of the needle can include the distal end of the needle; however, the distal portion, the distal end portion, or the distal length of the needle need not include the distal end of the needle. That is, unless context suggests otherwise, the distal portion, the distal end portion, or the distal length of the needle is not a terminal portion or terminal length of the needle.

[0068] As shown in FIG. 1 A, and to assist in the description of embodiments described herein, a longitudinal axis extends substantially parallel to an axial length of a needle extending from the driver. A lateral axis extends normal to the longitudinal axis, and a transverse axis extends normal to both the longitudinal and lateral axes. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art.

[0069] This disclosure generally relates to intraosseous (“I.O. ”) access devices, systems, and methods thereof. FIG. 1 A shows an exploded view of an exemplary intraosseous access system (“system”) 100, with some components thereof shown in elevation and other components shown in perspective. The intraosseous access system 100 can be used to penetrate skin and underlying hard bone for intraosseous access, such as, for example to access the marrow of the bone and / or a vasculature of the patient via a pathway through an interior of the bone.

[0070] In an embodiment, the system 100 includes a driver 101 and an access assembly 109. The driver 101 is used to rotate the access assembly 109 into a bone of a patient. In some embodiments, the driver 101 can be automated or manual. In an embodiment, the driver 101 is an automated driver 108. For example, the automated driver 108 can be a drill that achieves high rotational speeds. The intraosseous access system 100 can further include a stylet assembly 102, a shield 105, a needle assembly 202, and, optionally, a needle shield 107, which may be referred to, collectively, as the access assembly 109. In an embodiment, the stylet assembly 102 includes a stylet 104 and a stylet hub 103. In an embodiment, the stylet hub 103 is attached to the stylet 104 in any suitable manner (e.g., one or more adhesives or overmolding). The stylet hub 103 can be configured to interface with the driver 101.

[0071] In an embodiment, the shield 105 is configured to couple with the stylet 104. The coupling can allow longitudinal movement between the stylet 104 and the shield 105, whenthe shield 105 is in a first operational mode. In a second operational mode, the longitudinal movement between the stylet 104 and the shield 105 can be prevented, as described in more detail herein. For example, in the first operational mode, the stylet 104 maintains the shield 105 in an unlocked state. The stylet 104 can then be moved to a position where the shield 105 is no longer maintained in the unlocked state, and the shield 105 may automatically transition to the second operational mode, i.e., a locked state, in which little or no longitudinal movement is permitted between the shield 105 and the stylet 104. In the second operational mode, the shield 105 can inhibit inadvertent contact with a distal tip of the stylet 104 and prevent accidental needle stick injuries. In an embodiment, the shield 105 may be configured to rotate relative to the stylet 104, about a longitudinal axis, in one of the first operational mode or the second operational mode.

[0072] The automated driver 108 may take any suitable form. The driver 108 may include a handle 110 that may be gripped by a single hand of a user. The driver 108 may further include an actuator 111, e.g., trigger actuator, of any suitable variety via which a user may selectively actuate the driver 108 to effect rotation of a coupling interface 112. For example, the actuator 111 may comprise a button, as shown, or a switch or other mechanical or electrical element for actuating the driver 108. In an embodiment, the coupling interface 112 is formed as a socket 113 that defines a cavity 114. The coupling interface 112 can be configured to couple with the stylet hub 103. In an embodiment, the socket 113 includes sidewalls that substantially define a hexagonal cavity into which a hexagonal protrusion of the stylet hub 103 can be received. Other suitable connection interfaces are contemplated.

[0073] The automated driver 108 can include an energy source 115 of any suitable variety that is configured to energize the rotational movement of the coupling interface 112. For example, in some embodiments, the energy source 115 may comprise one or more batteries that provide electrical power for the automated driver 108. In other embodiments, the energy source 115 can comprise one or more springs (e.g., a coiled spring) or other biasing member that may store potential mechanical energy that may be released upon actuation of the actuator 111. The energy source 115 may be coupled with the coupling interface 112 in any suitable manner. For example, in an embodiment, the automated driver 108 includes an electrical, mechanical, or electromechanical coupling 116 to a gear assembly 117. In some embodiments, the coupling 116 may include an electrical motor that generates mechanical movement from electrical energy provided by an electrical energy source 115. In other embodiments, thecoupling 116 may include a mechanical linkage that mechanically transfers rotational energy from a mechanical (e.g., spring-based) energy source 115 to the gear assembly 117. The automated driver 108 can include a mechanical coupling 118 of any suitable variety to couple the gear assembly 117 with the coupling interface 112. In other embodiments, the gear assembly 117 may be omitted.

[0074] In some embodiments, the automated driver 108 can rotate the coupling interface 112, and thereby, can rotate the access assembly 109 at rotational speeds significantly greater than can be achieved by manual rotation of the access assembly 109. For example, in various embodiments, the automated driver 108 can rotate the access assembly 109 at speeds of between 200 and 3,000 rotations per minute (rpm). However, it will be appreciated that lesser or greater rotational speeds are also contemplated.

[0075] As shown in FIG. 1A, the needle assembly 202 includes a needle 204 and a needle hub 203 that is attached to the needle 204 in any suitable manner. The needle hub 203 can be configured to couple with the stylet hub 103 and may thereby be coupled with the driver 101. In an embodiment, the access assembly 109 in the assembled state includes the needle hub 203 retained by the stylet hub 103, the stylet 104 is disposed within a lumen of the needle and the shield 105 is in the unlocked position (first operational mode) within the access assembly 109.

[0076] FIGS. 1B-1C show an exemplary method of use for the I.O. access system 100. As shown in FIG. IB, with the access assembly 109 coupled with the driver 101 the driver 101 can rotate the access assembly 109 to penetrate the surface tissues and bone to access the medullary cavity. As shown in FIG. 1C, with the needle assembly 202 placed, the stylet assembly 102 can disengage the needle assembly 202 and be withdrawn proximally, withdrawing the stylet 104 from the lumen of the needle 204. The shield 105 is disposed within the needle hub 203 and the stylet 104 slides through the shield until a distal tip 146 of the stylet104 is located within the shield 105. At which point the shield 105 transitions from the first operational mode to the second operational mode and locks the shield 105 relative to the distal tip 146 of the stylet 104. The assembly of the driver 101, the stylet assembly 102, and the shield105 can then fully disengage the needle assembly 202.

[0077] In an embodiment, the stylet 104 is formed of a rigid material, e.g., stainless steel, to inhibit tissue and / or bone from entering a lumen of the needle 204 as the needle 204 isurged into the skin and bone tissues. Although not intentionally provided with a cutting distal edge, the rigid stylet 104 is ground flush with the beveled opening of the needle to provide a flush surface. Further the rigid material is sufficiently rigid and strong to inhibit tissue and / or bone from entering a lumen of the needle 204 during an access event. As such, the stylet tip 146 is sufficiently sharpened to provide a risk of needle stick injuries, and the shield 105 is provided to engage the stylet 104, and prevent accidental needle stick injuries.

[0078] I.O. access events are often performed in emergency situations and as the driver 101 and stylet assembly 102 are withdrawn rapidly from the needle assembly 202 the shield 105 may fail to fully engage the stylet tip 146. As such, the shield 105 may fail to transition to the second (locked) operational mode. Embodiments disclosed herein are to address the foregoing.

[0079] FIGS. 2A-2E show various details of an embodiment of a plate shield 205 generally including a housing 210 and a plate 220. The housing 210 and the plate 220 can be formed of a plastic, polymer, metal, alloy, composite, or similar suitable material. In an embodiment, the housing 210 and the plate 220 can be formed of the same material or from different materials. The housing 210 defines a substantially cylindrical shape where the walls extend substantially parallel, or can define a conical shape having a tapered profile where the walls extend at an angle relative to each other. The housing 210 defines a housing lumen 212 extending between a distal opening 214 disposed at a distal end, and a proximal opening 216 disposed at a proximal end. The housing lumen 212 is configured to receive a portion of the stylet 104 therethrough.

[0080] The diameter of the distal opening 214 defines a first diameter (t / 7) and the diameter of the proximal opening defines a second diameter (t / 2). In an embodiment, the second diameter (t / 2) is greater than the first diameter (t / 7). In an embodiment, the first diameter (t / 7) is equal to or slightly larger than an outer diameter of the stylet 104 and as such the stylet 104 slidably engages the distal opening 214 as the stylet 104 passes therethrough. In an embodiment, the housing 210 further includes a groove 218 extending annularly about an inner surface of the housing 210 and disposed adjacent the proximal opening 216. The diameter (< / 3) of the groove 218 is equal to the outer diameter (t / 3) of the plate 220 and greater than the diameter (t / 2) of the proximal opening 216. As such the plate 220 can engage the groove 218 in a snap-fit engagement to secure the plate 220 to the housing 210.

[0081] The plate 220 defines a central aperture 222 and further includes a plurality of fingers 224 extending radially inwards into the central aperture 222. In an embodiment, the plurality of fingers 224 also extend at a slight angle towards the distal end of the housing 210. The tips of the plurality of fingers 224 converge centrally to define a diameter (d4). The plurality of fingers 224 can elastically deflect along an axis extending parallel to a central longitudinal axis 70 of the plate shield 205.

[0082] As shown in FIG. 2A, the stylet includes a recess 150 disposed on the shaft of the stylet 104 at a predetermined length (LI) from the distal tip 146 of the stylet 104. The recess 150 extends annularly about the shaft of the stylet 104 to define a diameter that is less than the outer diameter of the stylet 104. In an embodiment, the diameter of the recess 150 can be substantially equal to the diameter (d4) defined by the tips of the plurality of fingers 224.

[0083] FIGS. 2D-2E show an exemplary method of use for the plate shield 205. FIG. 2D shows close up detail of the needle hub 203, shown in wire frame. The plate shield 205 is engaged with the needle hub 203 in an interference fit, press fit or snap fit engagement and a portion of the stylet 104 extends through the needle hub 203 and the plate shield 205. To note the needle 204 is not shown for ease of illustration.

[0084] As the stylet 104 is withdrawn proximally, the shaft of the stylet 104 slidably engages the distal opening 214 and the tips of the plurality of fingers 224. To note since the outer diameter of the stylet 104 is greater than the diameter (d4) defined by the tips of the plurality of fingers 224, the tips of the plurality of fingers 224 flex radially outwards and support the stylet 104 at a central axis 70 through the plate shield 205.

[0085] The stylet 104 is withdrawn proximally until the recess 150 aligns with the plate 220 and the tips of the plurality of fingers 224 are allowed to resume the undeflected position where the tips of the plurality of fingers 224 extend into the recess 150 and impinge thereon. The plurality of fingers 224 lock the plate shield 205 to the stylet 104. As such, urging the stylet 104 further proximally provides sufficient force to disengage the housing 210 from the needle hub 203. The distance between the plate 220 and the distal opening 214 is greater than the length (LI) between the recess 150 and the distal tip 146 of the stylet 104. As such the distal tip 146 of the stylet 104 is retained within lumen 212 of the housing 210. The plate shield 205 is locked to the stylet 104 mitigating accidental needle stick injuries. Advantageously, the plateshield 205 provides a reliable locking mechanism to mitigate shield failure, and provides a simplified construction which reduces manufacturing complexities and associated costs.

[0086] FIGS. 3 A-3F show an embodiment of a spring shield 305 for use with the access assembly 109. FIG. 3 A shows a cross-section view of the needle hub 203 with the spring shield 305 engaged therewith in a press-fit, interference fit, or snap-fit engagement. A portion of the stylet 104 extends through, and is slidably engaged with, both the spring shield 305 and the needle hub 203. To note the needle 204 is not shown for ease of illustration. FIG. 3B shows a perspective view of the spring shield 305. FIG. 3C shows a side view of the spring shield 305 in a first, or unlocked, operational mode. FIG. 3D shows a side view of the spring shield 305 in a second, or locked, operational mode.

[0087] The spring shield 305 generally includes a top plate 310 having a first arm 312A extending from a first side, perpendicular thereto, and a second arm 312B extending from a second side, opposite the first side and extending perpendicular to the top plate 310. The first arm 312A and the second arm 312B extending substantially parallel to each other when the spring shield 305 is in the unlocked position.

[0088] The first arm 312A includes a first base plate 314A extending perpendicular thereto and disposed at an opposite end of the first arm 312A from the top plate 310, the first base plate 314A includes a first base plate aperture 316A disposed therethrough. The second arm 312B includes a second base plate 314B extending perpendicular thereto and disposed at an opposite end of the second arm 312B from the top plate 310, the second base plate 314B includes a second base plate aperture 316B disposed therethrough. Each of the first base plate 314A and the second base plate 314B extends parallel with the top plate 310 when the spring shield 305 is in the unlocked position.

[0089] The top plate 310 further includes a top plate aperture 318 extending therethrough and aligned along a central longitudinal axis 70 of the spring shield 305. The top plate aperture 318 aligns with the both the first base plate aperture 316A and the second base plate aperture 316B when the spring shield 305 is in the unlocked position (FIG. 3B).

[0090] The spring shield 305 further includes a first hook 320A extending from a first edge of the top plate aperture 318 and extending towards the central longitudinal axis 70. The spring shield 305 also includes a second hook 320B extending from a second edge of the topplate aperture 318, opposite the first edge, and extending towards the central longitudinal axis 70.

[0091] The spring shield 305 is configured to transition between an unlocked position (FIGS. 3B-3C) and a locked position (FIG. 3D). In an embodiment, the spring shield 305 is biased towards the locked position. The spring shield 305 can be elastically deformed to the unlocked position and held in place by the shaft of the stylet 104 disposed through the first base plate aperture 316A and the second base plate aperture 316B and / or by the walls of the needle hub 203 when the spring shield 305 is engaged therewith (FIG. 3 A).

[0092] As shown in FIGS. 3B-3C, with the spring shield 305 in the unlocked position, the first base plate aperture 316A and the second base plate aperture 316B align and allow the shaft of the stylet 104 to slidably engage the spring shield 305 along the central longitudinal axis 70 through the first base plate aperture 316A, the second base plate aperture 316B and the top plate aperture 318.

[0093] As shown in FIG. 3D, in the locked position, the first arm 312A and the second arm 312B pivot radially outwards. As such, while the first base plate 314A and the second base plate 314B still overlap across the central longitudinal axis 70, the first base plate aperture 316A and the second base plate aperture 316B no longer align with the central longitudinal axis 70 thereby preventing distal movement of the stylet 104. In an embodiment, the first hook 320A and the second hook 320B engage the recess 150 of the stylet 104 in one or both of the locked position and the unlocked position to prevent further proximal movement of the stylet 104 relative to the spring shield 305. In an embodiment, in the locked position, the first hook 320A and the second hook 320B rotate inwards towards the central longitudinal axis 70 relative to the unlocked position.

[0094] FIGS. 3E-3F show an exemplary method of use for the spring shield 305. FIG. 3E shows the spring shield 305 in the unlocked position as described herein and engaged with the needle hub 203 in an interference fit, press-fit, or snap-fit engagement, or combinations thereof. The stylet 104 is withdrawn proximally through the needle hub 203, through the first base plate aperture 316A, the second base plate aperture 316B and the top plate aperture 318 until the first hook 320 A and the second hook 320B engages the recess 150.

[0095] In an embodiment, the first hook 320A and the second hook 320B slidably engage the stylet 104. In an embodiment, the lateral width between the first hook 320A and thesecond hook 320B is equal to or greater than the outer diameter of the stylet 104 so as to provide little or no friction as the stylet 104 slides through the spring shield 305. In an embodiment, the lateral width between the first hook 320A and the second hook 320B is equal to or less than the outer diameter of the stylet 104 so as to engage the stylet 104 as the stylet 104 slides longitudinally through the spring shield 305. In an embodiment, the outer diameter of the stylet 104 elastically deforms the first hook 320A and the second hook 320B radially outwards when the spring shield 305 is in the unlocked position.

[0096] In an embodiment, as the recess 150 aligns with the hooks 320A, 320B, the first hook 320A and the second hook 320B engage the recess 150 and, in an embodiment, resume the undeflected position. The first hook 320A and the second hook 320B impinge on the recess 150 and prevent any further proximal movement of the stylet 104 relative to the spring shield 305. As the stylet 104 is urged proximally, the force disengages the spring shield 305 from the needle hub 203 and allows the first arm 312A and the second arm 312B to pivot radially outwards to the locked position (FIG. 3F).

[0097] In an embodiment, a longitudinal length between the first and second hooks 320A, 320B and the first and second base plates 314A, 314B is greater than the length (LI) between the recess 150 and the distal tip 146 of the stylet 104. As such, when the recess 150 engages the hooks 320 A, 320B, the shaft of the stylet 104 disengages the first base plate aperture 316A and the second base plate aperture 316B allowing the first base plate 314A and the second base plate 314B to slide radially outwards (FIG. 3D).

[0098] In the locked position the first base plate 314A and the second base plate 314B prevent the stylet 104 from sliding distally relative to the spring shield 305 and the first hook 320A and the second hook 320B prevent the stylet 104 from sliding proximally relative to the spring shield 305. As such, the spring shield 305 is locked to the tip 146 of the stylet 104 mitigating accidental needle stick injuries. In an embodiment, as the spring shield 305 transitions to the locked position, the first hook 320A and the second hook 320B rotate radially inwards relative to the unlocked position, further impinging on the recess 150 and ensuring a secure engagement therewith. In an embodiment, the first hook 320A and the second hook 320B engage the recess 150 and elastically deform to ensure a tight fit with the recess 150 and mitigate accidental failure of the spring shield 305. Advantageously, the spring shield 305 provides a simplified construction which reduces manufacturing complexities and associated costs.

[0099] FIGS. 4A-4F show details of a cylinder shield 405 or use with an access assembly 109. The cylinder shield 405 includes a body 410 that defines substantially rectangular shape and includes a first edge 412 A, a second edge 412B, a third edge 412C, and a fourth edge 412D. The second edge 412B is disposed opposite the first edge 412A, and the third edge 412C is disposed opposite the fourth edge 412D. The body 410 is rolled up on itself such that the first edge 412A overlaps the second edge 412B and creates a cylinder. The body 410 further includes an end plate 414 extending from the third edge 412C at a proximal end of the cylindrical body 410, and extending perpendicular to the third edge 412C radially inwards. An inner edge of end plate 414 defines an aperture 416.

[0100] In an embodiment, the cylinder shield 405 is transitionable between an unlocked position and a locked position. In the unlocked position, the body 410 defines a diameter (dA) and in the locked position the body 410 defines a diameter (dB) where the diameter (dA) is greater than the diameter (dB). Further, in the locked position the first edge 412A and the second edge 412B provide a greater overlap relative to the unlocked position. In the unlocked position, the end plate aperture 416 defines a diameter (dC) and in the locked position the end plate aperture 416 defines a diameter (dD) where the diameter (dC) is greater than the diameter (dD).

[0101] In an embodiment, the body 410 is biased to the locked position and is elastically deformed to the unlocked position by the outer diameter of the shaft of the stylet 104 disposed through the end plate aperture 416. In an embodiment, the body 410 is biased to the unlocked position and is elastically deformed to the locked position by a biasing member, e.g., a rubber O-ring 420, or the like, extending about an outer surface of the body 410. In an embodiment, a length of the body 410 between the third edge 412C and the fourth edge 412D is greater than the length (LI), as such, as shown in FIG. 4A where the end plate aperture 416 engages the recess 150, the fourth edge 412D extends beyond the distal tip 146 of the stylet 104 mitigating accidental needle stick injuries.

[0102] FIGS. 4E-4F show an exemplary method of use for the cylinder shield 405. As shown in FIG. 4E, the cylinder shield 405 in an unlocked position is engaged with the needle hub 203 in a press-fit, interference fit, snap fit engagement or combinations thereof. The stylet 104 is withdrawn proximally through the needle hub 203 and end plate aperture 416 until the recess 150 aligns with the end plate aperture 416 and allows the cylinder shield 405 to transition to the locked position. In the locked position the end plate aperture 416 engages the recess 150and locks the cylinder shield 405 relative to the stylet 104. The stylet 104 can be urged proximally disengaging the cylinder shield 405 from the needle hub 203.

[0103] While some particular embodiments have been disclosed herein, and while the particular embodiments have been disclosed in some detail, it is not the intention for the particular embodiments to limit the scope of the concepts provided herein. Additional adaptations and / or modifications can appear to those of ordinary skill in the art, and, in broader aspects, these adaptations and / or modifications are encompassed as well. Accordingly, departures may be made from the particular embodiments disclosed herein without departing from the scope of the concepts provided herein.

Claims

CLAIMSWhat is claimed is:

1. An access assembly for use with an intraosseous access device, comprising: a needle defining a lumen and supported by a needle hub; a stylet configured to slidably engage the needle lumen and supported by a stylet hub, the stylet including a recess extending annularly and disposed a longitudinal length (LI) from a distal tip of the stylet, the recess defining a diameter that is less than an outer diameter of the stylet; and a plate shield comprising: a housing defining a lumen and slidably engaged with a proximal end of the needle hub, the housing defining a distal opening and a proximal opening; and a plate engaged with the proximal opening and defining an aperture, the plate including a plurality of fingers extending radially inwards into the aperture, the plurality of fingers angled towards a distal end of the housing.

2. The access assembly according to claim 1, wherein each finger of the plurality of fingers extends radially inward to a tip of the finger, the tips of the plurality of fingers define a diameter (d4) that is equal to or less than an outer diameter of the stylet and equal to or greater than the diameter of the recess.

3. The access assembly according to claim 1, wherein a longitudinal distance between the plate and the distal opening is greater than the longitudinal length (LI).

4. The access assembly according to claim 1, wherein the plurality of fingers elastically deform radially outwards to slidably engage a portion of the stylet therebetween.

5. The access assembly according to claim 1, wherein the plurality of fingers are configured to engage the recess and prevent movement of the housing relative to a distal tip of the stylet.

6. The access assembly according to claim 1, wherein a diameter of the distal opening is equal to or slightly larger than the outer diameter of the stylet such that the distal opening slidably engages the stylet.

7. The access assembly according to claim 1, wherein the housing includes a groove extending annularly about an inner surface of the housing adjacent the proximal opening, a diameter of the groove being greater than an inner diameter of the housing and equal to an outer diameter of the plate such that the plate engages the groove in a snap fit engagement.

8. The access assembly according to claim 1, wherein the housing engages the needle hub in an interference fit, press fit, or snap fit engagement.

9. A method of disengaging a stylet from an access needle, comprising: sliding a stylet proximally from a lumen of the access needle; sliding the stylet through an aperture disposed in a plate, the plate including a plurality of fingers extending radially inwards into the aperture and angled distally, the plate engaged adjacent a proximal opening of a housing; slidably engaging a tip of a finger of the plurality of fingers with the stylet to engage a recess disposed on the stylet; and impinging the tip in the recess to prevent further longitudinal movement of the stylet relative to the housing, a distal tip of the stylet disposed within the housing.

10. The method according to claim 9, wherein the plurality of fingers extend radially inward to define a diameter (d4) that is equal to or less than an outer diameter of the stylet and equal to or greater than the diameter of the recess.

11. The method according to claim 9, wherein a longitudinal distance between the plate and a distal opening of the housing is greater than a longitudinal length (LI) between the recess and the distal tip of the stylet.

12. The method according to claim 9, wherein the plurality of fingers elastically deform radially outwards to slidably engage a portion of the stylet therebetween.

13. The method according to claim 9, wherein the plurality of fingers engage the recess and prevent movement of the housing relative to a distal tip of the stylet.

14. The method according to claim 11, wherein a diameter of the distal opening is equal to or slightly larger than an outer diameter of the stylet such that the distal opening slidably engages the stylet.

15. The method according to claim 9, wherein the housing includes a groove extending annularly about an inner surface of the housing adjacent the proximal opening, a diameter of the groove being greater than an inner diameter of the housing and equal to an outer diameter of the plate such that the plate engages the groove in a snap fit engagement.

16. The method according to claim 9, wherein the housing engages a needle hub of the access needle in an interference fit, press fit, or snap fit engagement.

17. An access assembly for use with an intraosseous access device, comprising: a needle defining a lumen and supported by a needle hub; a stylet configured to slidably engage the needle lumen and supported by a stylet hub, the stylet including a recess extending annularly and disposed a longitudinal length (LI) from a distal tip of the stylet, the recess defining a diameter that is less than an outer diameter of the stylet; and a spring shield transitionable between a locked position and an unlocked position, the spring shield comprising: a top plate defining a top plate aperture and extending perpendicular to the stylet, a portion of the stylet extending through the top plate aperture; a first side arm extending from the top plate and including a first base plate defining a first base plate aperture; a second side arm extending from the top plate and including a second base plate defining a second base plate aperture; a first hook extending from a first side of the top plate aperture; and a second hook extending from a second side of the top plate aperture.

18. The access assembly according to claim 17, wherein in the unlocked position the top plate aperture, the first base plate aperture, and the second base plate aperture are aligned with a central longitudinal axis, and in the locked position the first base plate aperture and the second base plate aperture are misaligned with the central longitudinal axis.

19. The access assembly according to claim 17, wherein a first lateral distance between the first hook and the second hook is less than an outer diameter of the stylet and equal to or greater than a diameter of the recess.

20. The access assembly according to claim 19, wherein in the locked position, the first hook and the second hook move radially inward to a second lateral distance that is lessthan the first lateral distance, the second lateral distance being equal to or less than the diameter of the recess.

21. The access assembly according to claim 17, wherein the first hook and the second hook are configured to engage the recess and prevent further proximal movement between the stylet and the spring shield.

22. The access assembly according to claim 17, wherein the first hook and the second hook are disposed at a longitudinal distance from the first base plate and the second base plate that is greater than the longitudinal length (Z7).

23. The access assembly according to claim 17, wherein the first side arm and the second side arm are biased to the locked position and elastically deformed to the unlocked position, a portion of the stylet disposed in the first base plate aperture and the second base plate aperture retaining the spring shield in the unlocked position.

24. The access assembly according to claim 17, wherein in the locked position a distal tip of the stylet impinges on one of the first base plate and the second base plate to prevent distal movement of the stylet relative to the spring shield.

25. The access assembly according to claim 17, wherein the spring shield engages the needle hub in an interference fit, press fit, or snap fit engagement.

26. A method of disengaging a stylet from an access needle supported by an access needle hub having a spring shield retained therein, the method comprising: sliding a stylet proximally from a lumen of the access needle; sliding the stylet through a top plate aperture, a first base plate aperture, and a second base plate aperture of the spring shield; engaging a recess disposed on the stylet with one of a first hook and a second hook of the spring shield to prevent further proximal movement of the stylet relative to the spring shield; urging the stylet proximally to disengage the spring shield from the access needle hub; and transitioning a first arm and a second arm from an unlocked position to a locked position, the first arm supporting a first base plate that defines the first baseplate aperture, the second arm supporting a second base plate that defines the second base plate aperture.

27. The method according to claim 26, wherein transitioning the first arm and the second arm to the locked position misaligns the first base plate aperture and the second base plate aperture with a central longitudinal axis of the stylet, a distal tip of the stylet impinging on one or both of the first base plate and the second base plate to prevent distal movement of the stylet relative to the spring shield.

28. The method according to claim 26, wherein transitioning the first arm and the second arm to the locked position further includes transitioning the first hook and the second hook to a second lateral position, less than a first lateral position and equal to or less than an outer diameter of the recess.

29. The method according to claim 26, wherein in the unlocked position the top plate aperture, the first base plate aperture, and the second base plate aperture are aligned with a central longitudinal axis, and in the locked position the first base plate aperture and the second base plate aperture are misaligned with the central longitudinal axis.

30. The method according to claim 26, wherein a first lateral distance between the first hook and the second hook is less than an outer diameter of the stylet and equal to or greater than a diameter of the recess.

31. The method according to claim 30, wherein in the locked position, the first hook and the second hook move radially inward to a second lateral distance that is less than the first lateral distance, the second lateral distance being equal to or less than the diameter of the recess.

32. The method according to claim 26, wherein the first hook and the second hook engage the recess and prevent further proximal movement between the stylet and the spring shield.

33. The method according to claim 26, wherein first hook and the second hook are disposed at a longitudinal distance from the first base plate and the second base plate that is greater than a longitudinal length (LI) between the recess and a distal tip of the stylet.

34. The method according to claim 26, wherein the first arm and the second arm are biased to the locked position and elastically deformed to the unlocked position, a portion of thestylet disposed in the first base plate aperture and the second base plate aperture retaining the spring shield in the unlocked position.

35. The method according to claim 26, wherein in the locked position a distal tip of the stylet impinges on one of the first base plate and the second base plate to prevent distal movement of the stylet relative to the spring shield.

36. The method according to claim 26, wherein the spring shield engages the access needle hub in an interference fit, press fit, or snap fit engagement.

37. An access assembly for use with an intraosseous access device, comprising: a needle defining a lumen and supported by a needle hub; a stylet configured to slidably engage the needle lumen and supported by a stylet hub, the stylet including a recess extending annularly and disposed a longitudinal length (LI) from a distal tip of the stylet, the recess defining a diameter that is less than an outer diameter of the stylet; and a cylinder shield transitionable between a locked position and an unlocked position, the cylinder shield comprising: a body defining a first edge, a second edge, a third edge and a fourth edge, the body defining a cylindrical shape where the first edge, disposed opposite the second edge, overlaps the second edge; and an end plate extending from the third edge perpendicular to the body and extending radially inward an inner edge of the end plate defining an aperture, the end plate aperture in the locked position defines a relatively smaller aperture than the end plate aperture in the unlocked position.

38. The access assembly according to claim 37, wherein the cylinder shield is biased towards the locked position and is retained in the unlocked position by a portion of the stylet disposed within the end plate aperture.

39. The access assembly according to claim 37, wherein the cylinder shield is biased towards the unlocked position and is retained in the locked position by a biasing member encircling an outer surface of the body.

40. The access assembly according to claim 39, wherein the biasing member is a rubber O-ring.

41. The access assembly according to claim 37, wherein the cylinder shield is configured to transition to the locked position when the end plate aperture is aligned with the recess.

42. The access assembly according to claim 37, wherein a longitudinal distance between the third edge and the fourth edge is greater than the longitudinal length (Z7).

43. A method of disengaging a stylet from an access needle supported by an access needle hub having a cylinder shield retained therein, the method comprising: sliding a stylet proximally from a lumen of the access needle; sliding the stylet through an end plate aperture defined by an end plate extending perpendicular to a body that defines a cylinder, the body having a first edge overlapping a second edge; transitioning the body to a locked position where the end plate aperture defines a relatively smaller diameter; engaging a recess disposed on the stylet with the end plate aperture to prevent further movement of the stylet relative to the cylinder shield; and urging the stylet proximally to disengage the cylinder shield from the access needle hub.

44. The method according to claim 43, wherein the body defining the first edge and the second edge, the first edge disposed opposite the second edge, further includes a third edge disposed opposite a fourth edge, the body defining a cylindrical shape where the first edge overlaps the second edge.

45. The method according to claim 44, wherein the end plate extends from the third edge and wherein a longitudinal length between the third edge and the fourth edge is greater than a longitudinal length (LI) extending between the recess and a distal tip of the stylet.

46. The method according to claim 43, wherein the cylinder shield is biased towards the locked position and is retained in an unlocked position by a portion of the stylet disposed within the end plate aperture.

47. The method according to claim 43, wherein the cylinder shield is biased towards an unlocked position and is retained in the locked position by a biasing member encircling an outer surface of the body.

48. The method according to claim 47, wherein the biasing member is a rubber Oring.

49. The method according to claim 43, wherein the cylinder shield transitions to the locked position when the end plate aperture is aligned with the recess.

50. The method according to claim 43, wherein a longitudinal distance between a third edge and a fourth edge is greater than a longitudinal length (LI) between the recess and a distal tip of the stylet.

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