Patent Description:
Currently, the user must make a subjective assessment of when the needle is correctly placed. The user "feels" the needle advance past the relatively hard and compact, cortex layer of the bone and penetrates into the relatively soft, medullary cavity of the bone. However, the relative density of the bone cortex compared with the medullary cavity can vary depending on the bone, size of medullary space, and the patient. Accordingly, the clinician relies on a subjective assessment of a "lack of resistance" in order to determine if the medullary cavity has been successfully accessed. Further, the user relies on a subjective assessment to ensure that the needle does not advance through the medullary space and penetrate a far wall of the medullary cavity. Some devices include a stopping feature that contacts a skin surface. However, skin and subcutaneous tissue thickness can vary greatly between patients, leading to missed placements. <CIT> relates to an apparatus and method for accessing the bone marrow of a human's sternum.

The invention is defined by claim <NUM> and dependent claims disclose embodiments. No surgical methods are claimed. Briefly summarized, embodiments disclosed herein are directed to apparatus and methods for a stepped needle for an intraosseous device that uses the outer surface of the bone cortex as a reference point. Since the thickness of the bone cortex does not vary significantly between patients, the accuracy of needle placement can be improved. The device includes a needle with a stepped increase in outer diameter disposed along the needle shaft. The abrupt change in outer diameter is sufficient to provide a substantial increase in insertion force. In an embodiment, the stepped increase in outer diameter prevents the needle from being inserted any further into the bone cortex. The distance from the needle tip to the stepped increase in outer diameter is sufficient to ensure the needle tip enters the medullary cavity while preventing impingement on a far wall of the medullary cavity.

Disclosed herein is a needle assembly for an intraosseous access system including, a needle supported by a needle hub and extending to a distal tip, and a stepped increase in diameter disposed on an outer surface of the needle at a predetermined distance from the distal tip, the stepped increase in diameter configured to penetrate a skin surface and abut against a bone cortex.

In some embodiments, the predetermined distance is configured to allow the distal tip to extend through the bone cortex and into a medullary cavity of a bone. The stepped increase in diameter is formed integrally with the needle. A distal surface of the stepped increase in diameter extends perpendicular to a longitudinal axis of the needle. A distal surface of the stepped increase in diameter extends at an angle to a longitudinal axis of the needle to define a tapered shape. The needle defines a lumen having a first needle lumen diameter disposed distally of the stepped increase in diameter, and a second needle lumen diameter disposed proximally of the stepped increase in diameter, the second needle lumen diameter being larger than the first needle lumen diameter. In some embodiments, the needle assembly for an intraosseous access system further includes a third needle lumen diameter disposed proximally of the second needle lumen diameter, the third needle lumen diameter being less than the second needle lumen diameter to define a bulged portion in the needle.

In some embodiments, the needle assembly further includes an obturator disposed within the needle lumen, an outer diameter of the obturator being equal to, or less than, the first needle lumen diameter. In some embodiments, the needle assembly further includes an overtube engaged with an outer surface of the needle, a distal tip of the overtube defining a portion of the stepped increase in diameter. A longitudinal length of the overtube is less than a longitudinal length of a shaft of the needle, the overtube being adhered to the outer surface of the needle to form a collar. The overtube is slidably or rotatably engaged with the needle.

In an embodiment, the overtube includes a metal, alloy, plastic, polymer, composite, or carbon-based composite material. The overtube includes a first material, and a second material different from the first material. The first material is a relatively softer material and can elastically or plastically deform, the second material is a harder material and can be resistant to any elastic or plastic deformation. The overtube is formed of concentric tubes including a first tube formed of one of the first material or the second material and disposed adjacent the needle, and a second tube disposed on an outer surface of the first tube and formed of one of the first material or the second material. The overtube is formed of adjacent tubes including a first tube formed of the first material and disposed distally of a second tube formed of the second material. A first portion of the overtube is formed the first material and extends annularly about the needle between <NUM>° and <NUM>°, and a second portion of the overtube is formed of the second material and extends annularly about the needle between <NUM>° and <NUM>°. The distal tip of the overtube is configured to blunt and increase in diameter on contact with a surface of the bone cortex.

In some embodiments, a proximal end of the overtube abuts against the needle hub to prevent further longitudinal movement of the distal tip of the needle. A first diameter of the needle hub is between <NUM> and <NUM>. The needle hub includes a flared portion extending to a second diameter, the second diameter being greater than the first diameter. The needle hub includes a proximal housing slidably or rotatably engaged with a distal housing. In some embodiments, the needle hub includes a biasing member configured to bias the distal housing towards a proximal position relative to the proximal housing. The distal housing includes a distal face configured to engage a skin surface. The overtube is slidably engaged with the needle between a retracted position and an extended position. The distal tip of the overtube extends distally of the distal tip of the needle in the extended position. In some embodiments, the needle assembly further includes an overtube biasing member configured to bias the overtube towards the extended position. In some embodiments, the needle assembly further includes a locking mechanism configured to retain the overtube in the retracted position when in a locked configuration.

In some embodiments, the needle assembly further includes an actuator configured to transition the locking mechanism between the locked configuration and an unlocked configuration. The actuator includes rotating or sliding the proximal housing relative to the distal housing. The overtube biasing member is configured to prevent the overtube from transitioning from the extended position to the retracted position. In some embodiments, the needle assembly further includes an abutment configured to engage the overtube in the extended position and prevent the overtube transitioning from the extended position to the retracted position. In some embodiments, one of the needle or the overtube includes graduated markings.

Also disclosed is an exemplary method of accessing a medullary cavity including, penetrating a bone cortex with a distal tip of a needle, the needle including a stepped increase in outer diameter disposed at a predetermined distance from the distal tip, the predetermined distance being greater than a thickness of the bone cortex, abutting the stepped increase in outer diameter against a surface of the bone cortex to prevent further distal advancement of the distal tip, and accessing the medullary cavity.

In some embodiments, the method further includes withdrawing an obturator from a lumen of the needle until a distal tip of the obturator is proximal of a stepped increase in diameter of the lumen to allow a proximal blood flow to be observed and confirm medullary access. An overtube is slidably or rotatably engaged with the needle, a distal surface of the overtube defining a portion of the stepped increase in outer diameter. In some embodiments, the method further includes abutting a proximal end of the overtube against a needle hub to prevent further distal advancement of the distal tip of the needle. In some embodiments, the method further includes abutting a distal surface of a distal housing of a needle hub against a skin surface, the distal housing slidably or rotatably engaged with a proximal housing to allow the distal tip to continue to advance distally to access the medullary cavity. In some embodiments, the method further includes biasing the distal housing towards a distal position relative to the proximal housing.

In some embodiments, the method further includes transitioning the overtube between a retracted position, where a distal surface of the overtube is disposed at a predetermined distance from the distal tip of the needle, and an extended position where a distal surface of the overtube is disposed distally of the distal tip of the needle. In some embodiments, the method further includes biasing the overtube to the extended position. In some embodiments, the method further includes locking the overtube in the retracted position. In some embodiments, the method further includes sliding or rotating the proximal housing relative to the distal housing to unlock the overtube and transition the overtube from the retracted position to the extended position. In some embodiments, the method further includes engaging an abutment with a portion of the overtube to prevent the overtube transitioning from the extended position to the retracted position.

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.

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 needle intended 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.

As shown in <FIG>, and to assist in the description of embodiments described herein, a longitudinal axis extends substantially parallel to an axial length of a needle <NUM> extending from the driver <NUM>. A lateral axis extends normal to the longitudinal axis, and a transverse axis extends normal to both the longitudinal and lateral axes.

The present disclosure relates generally to intraosseous ("I. ") access devices, systems, and methods thereof. <FIG> shows an exploded view of an exemplary embodiment of an intraosseous access system <NUM>, with some components thereof shown in elevation and another shown in perspective. The intraosseous access system <NUM> 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.

In an embodiment, the system includes a driver <NUM> and an access assembly <NUM>. The driver <NUM> can be used to rotate the access assembly <NUM> into a bone of a patient. In embodiments, the driver <NUM> can be automated or manual. In an embodiment, the driver <NUM> is an automated driver <NUM>. For example, the automated driver <NUM> can be a drill that achieves high rotational speeds.

The intraosseous access system <NUM> can further include an obturator assembly <NUM>, a shield <NUM>, and a needle assembly <NUM>, which may be referred to, collectively, as the access assembly <NUM>. The access assembly <NUM> may also be referred to as an access system. The obturator assembly <NUM> is referred to as such herein for convenience. In an embodiment, the obturator assembly <NUM> includes an obturator <NUM>. However, in some embodiments, the obturator <NUM> may be replaced with a different elongated medical instrument. As used herein, the term "elongated medical instrument" is a broad term used in its ordinary sense that includes, for example, such devices as needles, cannulas, trocars, obturators, stylets, and the like. Accordingly, the obturator assembly <NUM> may be referred to more generally as an elongated medical instrument assembly. In like manner, the obturator <NUM> may be referred to more generally as an elongated medical instrument.

In an embodiment, the obturator assembly <NUM> includes a coupling hub <NUM> that is attached to the obturator <NUM> in any suitable manner (e.g., one or more adhesives or overmolding). The coupling hub <NUM> can be configured to interface with the driver <NUM>. The coupling hub <NUM> may alternatively be referred to as an obturator hub <NUM> or, more generally, as an elongated instrument hub <NUM>.

In an embodiment, the shield <NUM> is configured to couple with the obturator <NUM>. The coupling can permit relative longitudinal movement between the obturator <NUM> and the shield <NUM>, such as sliding, translating, or other movement along an axis of elongation (i.e., axial movement), when the shield <NUM> is in a first operational mode, and can prevent the same variety of movement when the shield <NUM> is transitioned to a second operational mode. For example, as further discussed below, the shield <NUM> may couple with the obturator <NUM> in a manner that permits longitudinal translation when the obturator <NUM> maintains the shield <NUM> in an unlocked state, and when the obturator <NUM> is moved to a position where it no longer maintains the shield in the unlocked state, the shield <NUM> may automatically transition to a locked state in which little or no translational movement is permitted between the shield <NUM> and the obturator <NUM>. Stated otherwise, the shield <NUM> may be longitudinally locked to a fixed or substantially fixed longitudinal orientation relative to the obturator <NUM> at which the shield <NUM> inhibits or prevents inadvertent contact with a distal tip of the obturator. In various embodiments, the shield <NUM> may be configured to rotate relative to the obturator <NUM> about a longitudinal axis of the obturator <NUM> in one or more of the unlocked or locked states.

With continued reference to <FIG>, the needle assembly <NUM> is referred to as such herein for convenience. In an embodiment, the needle assembly <NUM> includes a needle <NUM>. However, in various other embodiments, the needle <NUM> may be replaced with a different instrument, such as, for example, a cannula, a tube, or a sheath, and/or may be referred to by a different name, such as one or more of the foregoing examples. Accordingly, the needle assembly <NUM> may be referred to more generally as a cannula assembly or as a tube assembly. In like manner, the needle <NUM> may be referred to more generally as a cannula.

In an embodiment, the needle assembly <NUM> includes a needle hub <NUM> that is attached to the needle <NUM> in any suitable manner. The needle hub <NUM> can be configured to couple with the obturator hub <NUM> and may thereby be coupled with the driver <NUM>, as further discussed below. The needle hub <NUM> may alternatively be referred to as a cannula hub <NUM>.

In an embodiment, the shield <NUM> is configured to couple with the needle hub <NUM>. The coupling can prevent relative axial or longitudinal movement between the needle hub <NUM> and the shield <NUM>, such as sliding, translating, or the like, when the shield <NUM> is in the first operational mode, and can permit the shield <NUM> to decouple from the needle hub <NUM> when the shield <NUM> is transitioned to the second operational mode. For example, as further discussed below, the shield <NUM> may couple with the needle hub <NUM> so as to be maintained at a substantially fixed longitudinal position relative thereto when the obturator <NUM> maintains the shield <NUM> in the unlocked state, and when the obturator <NUM> is moved to a position where it no longer maintains the shield in the unlocked state, the shield <NUM> may automatically transition to a locked state relative to the obturator <NUM>, in which state the shield <NUM> also decouples from the needle hub <NUM>.

In an embodiment, the shield <NUM> can be coupled with the obturator <NUM>, the obturator <NUM> can be inserted into the needle <NUM>, and the obturator hub <NUM> can be coupled to the needle hub <NUM> to assemble the access assembly <NUM>. In an embodiment, a cap <NUM> may be provided to cover at least a distal portion of the needle <NUM> and the obturator <NUM> prior to use of the access assembly <NUM>. For example, in an embodiment, a proximal end of the cap <NUM> can be coupled to the obturator hub <NUM>.

With continued reference to <FIG>, the automated driver <NUM> may take any suitable form. The driver <NUM> may include a handle <NUM> that may be gripped by a single hand of a user. The driver <NUM> may further include an actuator <NUM> of any suitable variety via which a user may selectively actuate the driver <NUM> to effect rotation of a coupling interface <NUM>. For example, the actuator <NUM> may comprise a button, as shown, or a switch or other mechanical or electrical element for actuating the driver <NUM>. In an embodiment, the coupling interface <NUM> is formed as a socket <NUM> that defines a cavity <NUM>. The coupling interface <NUM> can be configured to couple with the obturator hub <NUM>. In an embodiment, the socket <NUM> includes sidewalls that substantially define a hexagonal cavity into which a hexagonal protrusion of the obturator hub <NUM> can be received. Other suitable connection interfaces are contemplated.

The automated driver <NUM> can include an energy source <NUM> of any suitable variety that is configured to energize the rotational movement of the coupling interface <NUM>. For example, in some embodiments, the energy source <NUM> may comprise one or more batteries that provide electrical power for the automated driver <NUM>. In other embodiments, the energy source <NUM> 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 <NUM>.

The energy source <NUM> may be coupled with the coupling interface <NUM> in any suitable manner. For example, in an embodiment, the automated driver <NUM> includes an electrical, mechanical, or electromechanical coupling <NUM> to a gear assembly <NUM>. In some embodiments, the coupling <NUM> may include an electrical motor that generates mechanical movement from electrical energy provided by an electrical energy source <NUM>. In other embodiments, the coupling <NUM> may include a mechanical linkage that mechanically transfers rotational energy from a mechanical (e.g., spring-based) energy source <NUM> to the gear assembly <NUM>. The automated driver <NUM> can include a mechanical coupling <NUM> of any suitable variety to couple the gear assembly <NUM> with the coupling interface <NUM>. In other embodiments, the gear assembly <NUM> may be omitted.

In embodiments, the automated driver <NUM> can rotate the coupling interface <NUM>, and thereby, can rotate the access assembly <NUM> at rotational speeds significantly greater than can be achieved by manual rotation of the access assembly <NUM>. For example, in various embodiments, the automated driver <NUM> can rotate the access assembly <NUM> at speeds of between <NUM> and <NUM>,<NUM> rotations per minute. However, greater or lesser rotations per minute are also contemplated.

Further details and embodiments of the intraosseous access system <NUM> can be found in patent application publications: <CIT>, <CIT>, <CIT>, and <CIT>.

<FIG> shows an exemplary access assembly <NUM>, which includes an obturator assembly <NUM> and a needle assembly <NUM>. The access assembly <NUM> is disposed within a patient with a tip <NUM> of the needle <NUM> extending through the skin surface <NUM>, subcutaneous tissues <NUM>, bone cortex <NUM>, and enters the medullary cavity <NUM>. The needle <NUM> further includes an obturator <NUM> disposed within a lumen thereof to prevent tissue, bone fragments and the like, entering and obstructing the needle lumen.

As shown in <FIG>, the needle <NUM> further includes a stepped portion ("step") <NUM> disposed annularly about an outer surface of the needle shaft <NUM> and defining an increase in outer diameter of the needle <NUM>. The stepped portion <NUM> is positioned at a predefined distance (x) from the needle tip <NUM>. The step <NUM> extends radially from the needle shaft <NUM> to provide an increase in outer diameter of the needle shaft <NUM>. The step <NUM> provides an increase in resistance as the needle <NUM> is driven into the bone cortex <NUM>. In an embodiment, the step <NUM> provides sufficient change in resistance to indicate to a user that the step <NUM> has contacted the outer surface of the bone cortex <NUM>, indicating that the needle bevel is within the medullary cavity <NUM>, as shown in <FIG>. In an embodiment, the step <NUM> prevents any further insertion of the needle <NUM> into the bone cortex <NUM>. In an embodiment, as shown in <FIG>, the needle <NUM> includes an overtube <NUM> that provides the step <NUM>, as will be described in more detail herein.

In an embodiment, the needle <NUM>, overtube <NUM>, or combinations thereof, include graduated markings <NUM> to indicate a depth of the needle tip <NUM> and guide the user as to when the needle tip <NUM> is correctly placed. In an embodiment, the overtube <NUM> can be formed of a metal, alloy, plastic, polymer, composite, carbon-based composite, combinations thereof, or the like. In an embodiment, a first portion of the overtube <NUM> can be formed of a first material, and a second portion of the overtube <NUM> can be formed of a second material different from the first material. In an embodiment the first material and the second material can display different mechanical properties. In an embodiment, the first material can be formed of a metal, alloy, or the like, and the second material can be formed of a plastic, polymer, or the like.

<FIG> show close up views of embodiments of the step <NUM>. It will be appreciated the features of these embodiments can be used in any combination without limitation and fall within the scope of the present invention. As shown in <FIG>, in an embodiment, the step <NUM> is formed integrally with the needle shaft <NUM>. As such, the needle <NUM> includes a distal portion <NUM> disposed distally of the step <NUM> and defines a first outer diameter, and a proximal portion <NUM> disposed proximally of the step <NUM> and defining a second outer diameter. The first outer diameter being less than the second outer diameter to define the step <NUM>. A first needle lumen diameter <NUM> defines a constant diameter both distally and proximally of the step <NUM>. Accordingly, a wall thickness of the proximal portion <NUM> of the needle <NUM> is greater than a wall thickness of the distal portion <NUM> of the needle <NUM>.

As shown in <FIG>, in an embodiment, the step <NUM> is formed integrally with the needle shaft <NUM>. As such, the needle <NUM> includes a distal portion <NUM> disposed distally of the step <NUM> and defines a first outer diameter, and a proximal portion <NUM> disposed proximally of the step <NUM> and defining a second outer diameter. The first outer diameter being less than the second outer diameter to define the step <NUM>. A needle lumen extending through the distal portion defines a first diameter <NUM>, and a needle lumen extending through the proximal portion defines a second diameter <NUM>, the second lumen diameter <NUM> being greater than the first lumen diameter <NUM>. Accordingly, a wall thickness of the needle <NUM> maintains a substantially constant thickness.

As shown in <FIG>, in an embodiment, the needle <NUM> defines a lumen including a first lumen diameter <NUM> and a second lumen diameter <NUM>, and a substantially constant wall thickness, as described herein in reference to <FIG>. The step <NUM> defines a tapered outer profile to provide an increase in outer diameter and to facilitate insertion of the needle through subcutaneous tissues <NUM>. The step <NUM> provides an increase in resistance when the step <NUM> contacts the bone cortex <NUM>. In an embodiment, a portion of the step <NUM> can be inserted within the bone cortex <NUM>. The needle lumen also includes a tapered transition portion <NUM>, adjacent the step <NUM> and disposed between the distal portion <NUM> of the needle <NUM>, which defines a first lumen diameter <NUM>, and the proximal portion <NUM> of the needle <NUM>, which defines a second lumen diameter <NUM>.

In an embodiment, the needle <NUM> can include a third portion (not shown) disposed proximally of the proximal portion <NUM> that defines a needle lumen having a first diameter <NUM>, i.e. a needle lumen that is less that the second lumen diameter <NUM>. As such the proximal portion <NUM> defines a "bulged" portion disposed at a predetermined distance (x) from the needle tip, as described herein. In an embodiment, the predetermined distance (x) can be between <NUM> and <NUM>, however other predetermined distances are also possible and within the scope of the invention. In an embodiment, the bulged proximal portion <NUM> can include a stepped, tapered, or rounded increase in diameter and decrease in diameter, back to the diameter of the distal portion <NUM>.

In the embodiments shown in <FIG>, the needle lumen facilitates medullary cavity access confirmation. In use, the needle <NUM> is inserted through the bone cortex <NUM> until the step <NUM> increases resistance. A user can then confirm the needle bevel is disposed within the medullary cavity by partially withdrawing the obturator <NUM> until a distal end thereof is proximal of the step <NUM>. As shown in <FIG>, blood can then flow proximally through the needle lumen, past the obturator <NUM>, to a needle hub where the blood flow can be observed to confirm medullary cavity access. If the needle tip <NUM> has not accessed the medullary cavity <NUM>, a reduced or absent blood flow will be observed. In which case the obturator <NUM> can be reinserted with minimal risk of contamination, and insertion of the access assembly <NUM> can continue through the bone cortex <NUM>. In an embodiment, the tapered transition portion <NUM> of the needle lumen can facilitate reinsertion of the obturator <NUM> within the distal portion of the needle lumen.

As shown in <FIG>, in an embodiment, the needle <NUM> defines a substantially constant outer diameter, a constant wall thickness, and a constant lumen diameter. The needle <NUM> further includes an overtube <NUM> disposed on an outer surface of the needle <NUM> and defines an overtube wall thickness that defines the step <NUM>. In an embodiment, a distal end of the overtube <NUM> extends to a point that is proximal of the needle tip <NUM>. In an embodiment, a distal end of the overtube <NUM> extends to a point that is a predetermined distance (x) from the needle tip <NUM>. As noted, the predetermined distance (x) can be between <NUM> and <NUM>, however other predetermined distances are also possible and within the scope of the invention, as described herein. As shown in <FIG>, the distal end of the overtube <NUM> can be tapered to facilitate insertion of the needle through tissues <NUM>, <NUM>.

In an embodiment, the overtube <NUM> is attached to the needle shaft by adhesive, welding, bonding, crimping or the like. Accordingly, the overtube <NUM> is fixed and unable to move relative to the needle <NUM>. In an embodiment, the overtube <NUM> can extend over a portion of the needle <NUM>. In an embodiment, a proximal end of the overtube <NUM> can extend to a point that is distal of the needle hub <NUM>. In an embodiment, the overtube <NUM> can define a collar that is attached to the needle shaft as described herein.

In an embodiment, the overtube <NUM> is slidably engaged with the needle <NUM> and can be selectively secured in place. The position of a distal end of the overtube <NUM> can be adjusted relative to the needle tip <NUM> to a preferred distance along the longitudinal axis. The user can select a predetermined distance (x) depending on the type of target bone, the procedure, or age or health of the patient, or the like. For example, a predetermined distance (x) of <NUM>-<NUM> would be preferable for smaller, pediatric patients, where a distance of <NUM>-<NUM> would be preferable for larger, adult patients.

In an embodiment, the overtube <NUM> is rotatably engaged with the needle <NUM> about the longitudinal axis. This allows the needle <NUM> to spin freely while the overtube <NUM> remains substantially stationary. In an embodiment, the needle <NUM> can be drilled through the bone cortex <NUM> and the overtube <NUM> protects the surrounding tissues <NUM>, <NUM> from twisting about the needle <NUM> as the needle spins. The overtube <NUM> therefore protects the tissues <NUM>, <NUM> from damage and irritation. In an embodiment, the overtube <NUM> can be both slidably and rotatably engaged with the needle <NUM>. Accordingly, the user can select a predetermined distance (x) between the distal end of the overtube <NUM> and the needle tip <NUM>. Further the overtube can protect any surrounding tissue <NUM>, <NUM> as the needle is drilled into the bone cortex <NUM>.

In an embodiment, as shown in <FIG>, the needle <NUM> includes both a stepped portion <NUM>, for example as described herein in reference to <FIG>, as well as an overtube <NUM>. The distal end of the overtube <NUM> can align with the stepped portion <NUM>. In an embodiment, the distal end of the overtube <NUM> can be positioned proximally of the stepped portion <NUM> to provide a second step (not shown). For example, the first step <NUM> can indicate that the user is approaching the predetermined depth. A user can then continue to insert the access assembly <NUM>, including the first step, through the bone cortex <NUM>, until a second step (not shown) contacts the bone cortex indicating that the desired depth is reached, or preventing any further insertion of the access assembly <NUM>.

As shown in <FIG>, the overtube <NUM> can include a first material <NUM> and a second material <NUM>. In an embodiment, the overtube <NUM> can be formed of one or more concentric tubes of one or more different materials, e.g. as shown in <FIG>. In an embodiment, the overtube <NUM> can be formed of one or more adjacent tubes of one or more different materials, disposed along the longitudinal axis, e.g. <FIG>. In an embodiment, the overtube <NUM> can include different adjacent portions formed of one or more materials.

As shown in <FIG>, in an embodiment, the first material is overmolded on to the second material <NUM>, which is disposed adjacent the needle shaft <NUM>, forming a tube thereabout. In an embodiment the first material <NUM> can be a plastic, polymer, or the like and the second material <NUM> can be a metal, alloy, or the like. In an embodiment, the first material <NUM> can display softer material properties or can elastically or plastically deform. In an embodiment, the second material <NUM> can display harder or resilient material properties and can be resistant to any elastic or plastic deformation. In an embodiment, as shown in <FIG>, the tube of a first material <NUM> can be disposed adjacent the needle shaft <NUM> and a tube of the second material <NUM> can be disposed thereover, substantially along an outer surface of the overtube <NUM>.

In an embodiment, the second material <NUM> can provide structural support to overtube while the first material <NUM> can deform to increase the outer diameter of the overtube as it is urged against the bone cortex <NUM>. To note the first material <NUM> can be sufficiently resilient to penetrate the skin surface tissues <NUM>, <NUM> without deforming but can deform slightly, when urged against the bone cortex <NUM>. Further, the relatively softer first material <NUM> can be configured to mitigate trauma to the bone cortex <NUM> as the needle <NUM> is rotated.

In an embodiment, a distal tip of the overtube <NUM>, forming the stepped increase in diameter <NUM> can be formed of the first, relatively softer material <NUM>. The tapered shape can facilitate penetrating the skin surface tissues <NUM>, <NUM>. Then, when the tapered stepped increase in diameter <NUM> contacts the relatively hard bone cortex <NUM>, the tapered shape can deform and "mushroom" out, to abut against the bone cortex and provide an increase in resistance to distal advancement, as described herein. In an embodiment, the distal tip can mushroom out to a diameter that is greater than the outer diameter of the overtube <NUM> to provide a greater resistance to further distal advancement.

In an embodiment, as shown in <FIG>, the overtube <NUM> can be formed of one or more adjacent tubes of one or more different materials, disposed along the longitudinal axis. For example, the overtube <NUM> can be formed of a second, relatively harder material <NUM> and include a first, relatively softer material <NUM> disposed at a distal tip and forming the stepped increase in diameter <NUM>. In an embodiment, the distal tip formed of the first material <NUM> can define a stepped increase in diameter <NUM> extending perpendicular to the longitudinal axis, or can define a tapered stepped increase in diameter <NUM>, as described herein. The distal tip formed of the first material <NUM> can mitigate trauma to the bone cortex <NUM> as the overtube <NUM> is urged distally. In an embodiment, the distal tip formed of the first material <NUM> can deform, blunt, or "mushroom," to provide an increase in outer diameter, an increase resistance to further distal advancement, cushion the impact of the overtube <NUM> against the bone cortex, or combinations thereof.

In an embodiment, as shown in <FIG>, a first side wall portion of the overtube <NUM> can be formed of a first material <NUM> and a second side wall portion of the overtube <NUM> can be formed of a second material <NUM>. In an embodiment, each of the first side wall portion or the second side wall portion can extend along a longitudinal length of the overtube <NUM> from a proximal end <NUM> to the distal end, adjacent the stepped increase in diameter <NUM>. In an embodiment, one of the first side wall portion or the second side wall portion can extend about the longitudinal axis between <NUM>° and <NUM>°. However, greater or lesser degrees are also contemplated. In an embodiment, the overtube <NUM> can be formed of a first half, extending about the longitudinal axis of the needle <NUM> by <NUM>° and formed of a first material <NUM>, a second half, extending about the longitudinal axis of the needle <NUM> by <NUM>° and formed of a second material <NUM>.

In an embodiment, the overtube <NUM> can be formed of a first quarter extending about the longitudinal axis of the needle <NUM> by <NUM>° and formed of a first material <NUM>, a second quarter disposed adjacent the first quarter, extending about the longitudinal axis of the needle <NUM> by <NUM>° and formed of a second material <NUM>, a third quarter disposed adjacent the second quarter, and extending about the longitudinal axis of the needle <NUM> by <NUM>° and formed of a first material <NUM>, and a fourth quarter disposed adjacent the third quarter, and extending about the longitudinal axis of the needle <NUM> by <NUM>° and formed of a first material <NUM>. It will be appreciated however, that other combinations of materials, and annular extensions, i.e. between <NUM>° and <NUM>°, of the different portions of the overtube <NUM> are also contemplated. In an embodiment, the overtube <NUM> can include a distal tip portion extending annularly about the needle <NUM> and formed of the first material <NUM>. The distal tip portion can be configured to deform when contacting the bone cortex, as described herein.

In an embodiment, as shown in <FIG>, the overtube <NUM> can be both slidably and rotatably engaged as described herein. The distal end of the overtube <NUM> can longitudinally align with one of the needle tip <NUM>, the needle bevel, or a proximal edge of the needle bevel. The overtube <NUM> and needle <NUM> can then be inserted through the skin <NUM> and subcutaneous tissues <NUM> until the distal end of the overtube <NUM> contacts a surface of the bone cortex <NUM>. The needle <NUM> can then be rotated and drilled into the bone cortex <NUM> while the overtube <NUM> can remain substantially stationary, and protects the surrounding tissues <NUM>, <NUM> from twisting about needle <NUM> as it spins. Advantageously, the overtube <NUM> being rotatably engaged with the needle <NUM> can allow the needle to rotate freely, while the overtube <NUM>, or more specifically, the stepped increase in diameter <NUM> remains substantially stationary against the surface of the bone cortex <NUM>. This can mitigate any friction or trauma of the bone cortex <NUM> by mitigating any movement of stepped increase in diameter <NUM> relative to the surface of the bone cortex <NUM>. The needle <NUM> then advances distally, through the over tube <NUM> and through the bone cortex <NUM>, until a proximal end <NUM> of the overtube <NUM> contacts a needle hub <NUM>, preventing any further advancement of the needle <NUM> relative to the overtube <NUM>. It will be appreciated that when the proximal end <NUM> of the overtube <NUM> contacts the needle hub <NUM>, the distal end of the overtube <NUM> will be at a predetermined distance (x) from the needle tip <NUM>. The predetermined distance (x) being sufficient to allow the needle bevel to enter the medullary cavity <NUM>, without the needle tip <NUM> contacting a far wall of the medullary cavity <NUM>.

With continuing reference to <FIG>, in an embodiment, when the needle is to be removed, the needle <NUM> can be retracted through the bone cortex <NUM> and into the overtube <NUM> such that a needle tip <NUM> is disposed within the lumen of the overtube <NUM>. Optionally, the needle <NUM> and overtube <NUM> can then be locked in place relative to each other when the needle tip <NUM> is disposed within the lumen of the overtube <NUM>. The needle <NUM> and overtube <NUM> can then be withdrawn from the tissues <NUM>, <NUM>. Accordingly, the overtube <NUM> provides a safety cover for the needle <NUM>, preventing accidental needle stick injuries once the needle is removed from the patient.

As shown in <FIG>, in an embodiment, an access assembly <NUM> can include a needle hub <NUM> that defines an increased diameter (d1), extending perpendicular to a longitudinal axis of the needle <NUM>. In an embodiment, a diameter (d1) of the needle hub <NUM> can be between <NUM> and <NUM> although greater or lesser diameters are also contemplated. Advantageously, the needle hub <NUM> with the increased diameter (d1) can provide increased leverage for a user to grasp the needle hub <NUM> and urge the needle <NUM> through the bone cortex <NUM> by hand, or remove the needle assembly <NUM> by hand after the procedure is complete. The increased hub diameter can be of importance if the driver <NUM> fails to operate, runs out of power, or if the user is able to determine access to medullary cavity <NUM> more accurately by urging the needle <NUM> by hand, through a remaining distance of bone cortex. For example, a user may use the driver <NUM> to drill the needle <NUM> through a majority of the bone cortex <NUM> and then detach the access assembly <NUM> and drive the needle <NUM> the remainder of the distance by hand in order to "feel" medullary cavity access more accurately. Further, the increased hub diameter can be important to allow a user to remove the needle <NUM> from the bone cortex <NUM> without having to attach a secondary device, e.g. syringe, hemostats, or the like, to the needle hub <NUM> to facilitate removal of the needle <NUM>.

In an embodiment, the needle hub <NUM> can include one or more flared portions <NUM>, for example a distal flared portion 303A and a proximal flared portion 303B. The flared portion <NUM> can extend annularly about the hub and provide an increased diameter (d2) relative to the diameter (d1) of the needle hub <NUM>. Advantageously, the flared portion <NUM> can provide support for a user when urging the needle hub <NUM> along the longitudinal axis in either of the proximal or distal directions. Further the flared portion <NUM> can guide a user's fingers towards a longitudinal midpoint of the needle hub <NUM> and provide a secure grasp of the needle hub <NUM>. This can be important in an emergency situations, where a user, who is often wearing gloves, would need to grasp the hub <NUM> rapidly and apply significant force to the needle hub <NUM>, while avoiding slipping.

In an embodiment, the needle hub <NUM> can include a distal housing 304A and a proximal housing 304B that are slidable engaged with each other, for example, in a telescoping manner. As shown in <FIG>, an outer diameter of the proximal housing 304A can be equal to an inner diameter of the proximal housing 304B to allow the distal housing 304A to slide into a cavity defined by the proximal housing 304B. It will be appreciated that other configurations of housings 304A, 304B are also contemplated, for example the proximal housing 304B being received within the distal housing 304A.

Advantageously, the proximal housing 304B can spin about the longitudinal axis independently of the distal housing 304A. As such, as the access assembly <NUM> advances into the patient, a distal face <NUM> of the distal housing 304A can contact a skin surface of the patient. The distal face <NUM> of the distal housing 304A can rest in a substantially stationary position against the skin surface, allowing the proximal housing 304B and/or needle <NUM> to rotate about the longitudinal axis until the medullary cavity is accessed. The distal housing 304A can mitigate friction between the access assembly <NUM> and the skin surface, preventing friction burns, or similar trauma.

In an embodiment, the distal housing 304A can slide independently of the proximal housing 304B and/or needle <NUM>, along the longitudinal axis. In an embodiment, the needle hub <NUM> can further include a biasing member, e.g. compression spring, or the like, configured to bias the distal housing 304A towards a longitudinally distal position. In an embodiment, when a distal face <NUM> of the distal housing 304A contacts a skin surface of the patient, the proximal housing 304B and/or the needle <NUM> can continue to advance distally, along the longitudinal axis until the medullary cavity <NUM> is accessed. The distal housing 304A can rest on a skin surface and remain substantially stationary preventing compression or trauma of the surface tissues <NUM>, <NUM> disposed between the distal face <NUM> and the bone cortex <NUM>. This can be important where a thickness of the surface tissues <NUM>, <NUM> can vary significantly between different patients.

Further, the distal face <NUM> can align with the skin surface <NUM> to stabilize the needle assembly <NUM> once the needle <NUM> has been placed correctly. In an embodiment, a stabilizing device can be attached to the needle hub <NUM> or distal housing 304A to further stabilize the needle assembly <NUM> relative to the skin surface <NUM>. The biasing member disposed within the needle hub can be configured to apply sufficient pressure to the distal housing 304A to urge the distal face <NUM> against the skin surface <NUM> and stabilize the needle hub <NUM>, without compressing the surface tissues <NUM>, <NUM> between the distal face <NUM> and the bone cortex <NUM>. In an embodiment, the distal face <NUM> can include an adhesive or the like to further stabilize the needle assembly <NUM> with the skin surface <NUM>.

As shown in <FIG>, in an embodiment, the access assembly <NUM> can include an overtube <NUM> slidably engaged with an outer surface of the needle <NUM> and defining a thickness to define a stepped portion <NUM> at a distal end thereof. To note, the overtube <NUM> can allow the needle <NUM> to rotate independently of the overtube <NUM>, as described herein. In an embodiment, the overtube <NUM> can be slidable along a longitudinal axis of the needle <NUM> between a retracted position (<FIG>) and an extended position (<FIG>).

In an embodiment, with the overtube <NUM> in the retracted position, a predetermined distance (x) between a distal tip of the overtube <NUM> that defines a stepped outer diameter <NUM> and a distal tip of the needle <NUM> can be sufficient to allow a bevel of the needle to access the medullary cavity <NUM>. In the extended position, a distal tip of the overtube <NUM> can extend distally of the distal tip <NUM> of the needle <NUM>. The needle hub <NUM> can include an overtube biasing member <NUM>, e.g. a compression spring or the like, configured to bias the overtube <NUM> towards an extended position.

The needle hub <NUM> can further include a locking mechanism <NUM> configured to selectively retain the overtube <NUM> in a retracted position. As shown, the locking mechanism is disposed at a mid-section of the overtube <NUM>, however, it will be appreciated that other configurations of locking mechanism <NUM> are also contemplated including disposing towards a proximal end. In the retracted position, the locking mechanism <NUM> can inhibit proximal movement of the overtube <NUM> relative to the needle <NUM> to maintain the predetermined distance (x) between the stepped portion <NUM> and the needle tip <NUM>. Further, the locking mechanism in the locked configuration, can retain the overtube <NUM> to prevent distal advancement of the overtube <NUM> relative to the needle <NUM>. In an embodiment, the locking mechanism <NUM> can be transitioned from the locked configuration to the unlocked configuration to allow the overtube biasing member <NUM> to urge the overtube <NUM> to the extended position. Advantageously, in the extended position, the overtube <NUM> can prevent accidental needle stick injuries when the needle <NUM> is withdrawn proximally from the patient.

In an embodiment, the locking mechanism <NUM> can be transitioned from the locked configuration to the unlocked configuration by rotating the proximal housing 304B relative to the distal housing 304A in one of a clockwise or anti-clockwise direction. Advantageously, the proximal housing 304B can include a gripping feature <NUM> configured to facilitate grasping the proximal housing 304B and rotating the proximal housing about the longitudinal axis. Exemplary gripping features <NUM> can include grooves, ridges, or similar structures, and/or can include different materials disposed on a surface of the proximal housing 304B that have an increased friction co-efficient, e.g. rubber, silicone, or the like, or combinations thereof. As shown, the gripping feature <NUM> is disposed on a flared portion 303B of the proximal housing 304B, however other configurations of gripping features are also contemplated. Often a user can be wearing gloves when manipulating the needle hub <NUM> and the increased diameter (d1) of the needle hub <NUM>, the flared portion(s) <NUM>, and/or gripping feature(s) <NUM> can facilitate manipulation of the needle hub <NUM> even with gloves on.

In an embodiment, the locking mechanism <NUM> can be transitioned from the locked configuration to the unlocked configuration by sliding the proximal housing 304B relative to the distal housing 304A, along a longitudinal axis. For example, a user can grasp the proximal housing 304B and slide proximally away from the distal housing along the longitudinal housing to activate one or more cantilever systems that can transition the locking mechanism from the locked configuration to the unlocked configuration. In the unlocked configuration the biasing member <NUM> can urge the overtube <NUM> distally to the extended position, as described herein. As will be appreciated, the distal flared portion 303A and the proximal flared portion 303B can facilitate grasping the respective distal housing 304A and proximal housing 304B and sliding longitudinally apart, as described herein.

As shown in <FIG>, in an embodiment, the biasing member <NUM> is configured to prevent proximal movement of the overtube <NUM> from the extended position to prevent retraction of the overtube <NUM> and prevent accidental needle stick injuries. In an embodiment, the needle hub <NUM> can include an abutment <NUM> configured to abut against the overtube <NUM>, or portion thereof, to prevent proximal movement of the overtube <NUM> from the extended position to prevent retraction of the overtube <NUM> and prevent accidental needle stick injuries.

In an exemplary method of use, as shown in <FIG>, an access assembly <NUM> can be provided, as described herein. The access assembly <NUM> can be coupled with an intraosseous access system <NUM>, configured to drive the needle <NUM> through a bone cortex <NUM> and access a medullary cavity <NUM>.

As shown in <FIG>, prior to insertion of the needle <NUM>, the access assembly <NUM> can include an overtube <NUM> disposed in the retracted position and retained in the retracted position by the locking mechanism <NUM>. As shown in <FIG>, the access assembly can be rotated by the driver <NUM> to drill the needle <NUM> through the skin <NUM> and surface tissues <NUM> to the bone cortex <NUM>. The driver <NUM> can continue to drill the needle <NUM> through the bone cortex <NUM> and a distal portion of the overtube <NUM> can be inserted through the skin <NUM> and surface tissues <NUM> until the stepped portion <NUM> abuts against a surface of the bone cortex <NUM>, preventing any further distal movement of the access assembly <NUM>.

In an embodiment, prior to insertion of the needle <NUM>, the overtube <NUM> can be biased towards the extended position. The needle <NUM> and overtube <NUM> can be advanced through the surface tissues <NUM>, <NUM> until a distal tip of the overtube <NUM> contacts the bone cortex <NUM>. The driver <NUM> can be activated to drill the needle <NUM> through the bone cortex <NUM>. As the needle <NUM> advances, the overtube <NUM> can transition towards the retracted position.

In an embodiment, the distal surface <NUM> of the needle hub <NUM> can abut against the skin surface. As noted, the distal housing 304A can be configured to contact the skin surface and remain substantially stationary while allowing the needle <NUM> and/or proximal housing 304B to continue to rotate. Advantageously, then distal housing 308A can prevent friction burns, or similar trauma between the needle hub <NUM> and the skin surface <NUM>.

In an embodiment, the distal surface <NUM> can contact the skin surface <NUM> prior to the stepped portion <NUM> contacting the bone cortex <NUM>, or prior to the overtube <NUM> fully transitioning to the retracted position. As noted, the distal housing 304A can be slidably engaged with the needle hub <NUM> and configured to allow the needle <NUM> to continue to advance distally while the distal housing 304A rests on a skin surface <NUM>. Advantageously, this can prevent the soft tissues <NUM>, <NUM> from being compressed between the distal face <NUM> and the bone cortex <NUM> and stabilizes the needle hub <NUM> with the skin surface <NUM>. In an embodiment, the distal housing 304A configured as such, can allow a stabilizing device to be attached to the needle hub <NUM> or the distal housing 304A to further stabilize the needle assembly <NUM> relative to the skin surface <NUM>. Optionally, when the overtube <NUM> has fully transitioned to the retracted configuration, the locking mechanism can be configured to automatically retain the overtube <NUM> in the retracted position.

As shown in <FIG>, once the medullary cavity <NUM> has been accessed and the procedure is complete, the needle assembly <NUM> can be withdrawn proximally. Prior to removal of the needle <NUM>, or after removal of the needle <NUM> from the insertion site, the needle hub <NUM> can be actuated to transition a locking mechanism <NUM> from the lock configuration to the unlocked configuration. In an embodiment, the proximal housing 304B can be rotated either clockwise or anticlockwise relative to the distal housing 304A to actuate the needle hub <NUM>. In an embodiment, the proximal housing 304B can be slid longitudinally either proximally or distally relative to the distal housing 304A to actuate the needle hub <NUM>. It will be appreciated that other configurations of actuating the needle hub <NUM> such as push buttons, levers, or the like are also contemplated.

With the locking mechanism <NUM> in the unlocked configuration, the overtube biasing member <NUM> can urge the overtube <NUM> distally and transition the overtube <NUM> from the retracted position to the extended position, either as the needle <NUM> is withdrawn from the insertion site, or optionally, after the needle is withdrawn from the insertion site. In an embodiment, the biasing member <NUM> can maintain the overtube <NUM> in the extended configuration to prevent accidental needle stick injuries. In an embodiment, the needle hub <NUM> can further include an abutment <NUM> configured to engage the overtube <NUM>, or portion thereof, and maintain the overtube <NUM> in the extended configuration to prevent accidental needle stick injuries.

Advantageously, embodiments disclosed herein provide a change in needle outer diameter that is abrupt enough to substantial increase resistance to insertion. This change in insertion resistance indicates the needle tip is correctly placed. In an embodiment, the change in resistance prevents the needle from being inserted past the outer diameter step. This removes any subjective assessment as to when to stop advancing the needle. Accordingly, embodiments can be deployed by users who don't have specialized training or regular practice at placing intraosseous devices. This is especially important since placing intraosseous devices often occur in emergency situations where users may not have specialized training or regular practice, yet need to quickly access a medullary cavity for vascular access.

Claim 1:
A needle assembly (<NUM>) for an intraosseous access system, comprising:
a needle (<NUM>) supported by a needle hub (<NUM>) and extending to a distal tip (<NUM>); and
a stepped increase in diameter disposed on an outer surface of the needle at a predetermined distance from the distal tip (<NUM>), the stepped increase in diameter configured to penetrate a skin surface (<NUM>) and abut against a bone cortex (<NUM>),
wherein the needle (<NUM>) defines a lumen having a first needle lumen diameter (<NUM>) disposed distally of the stepped increase in diameter, and a second needle lumen diameter (<NUM>) disposed proximally of the stepped increase in diameter, the second needle lumen diameter (<NUM>) being larger than the first needle lumen diameter (<NUM>).