Needle hub and related methods of use

Abstract

A needle hub for a pen needle is provided having an enlarged surface for contacting the skin of a patient. The enlarged surface is configured to have a size and shape such that a needle or cannula can penetrate the skin to a desired depth and allow substantially the entire exposed length of the needle or cannula to penetrate the skin to the desired depth. The surface of the needle hub can be formed by a central conical shaped member and an outer ring, the central shaped member forming a first contact surface having a surface area of about 1-5 mm 2 and the outer ring located at an outer peripheral edge and forming a second contact surface having a surface area of about 15 mm 2 to 50 mm 2 in combination. The present invention also relates to a method for injecting a medicament into a subject.

Description

[0001] This invention patent application is a divisional application of the invention patent application filed on February 22, 2018, with application number 201810154111.6 and invention title "Needle base and related usage method". Technical Field

[0002] This invention relates to a needle hub and a needle hub surface configured for controlling the insertion depth of a needle or cannula. The invention also relates to a pen needle having a needle hub with interfacial features to limit the penetration depth of the needle during initial insertion and during injection of material into a patient. The contact surface is configured to optimize the penetration or insertion depth, wherein substantially the entire length of the needle or cannula exposed from the needle hub can be inserted into the skin, thereby providing improved consistency in penetration depth. The needle hub has a seat surface with specific areas for concentrating surface pressure applied to the skin surface in said selected area to control the depth of penetration into the skin. Background Technology

[0003] Needle Insertion Medeling; Identifiability and Limitations, L. Barbe, Biomedical Signal Processing and Control 2(207)191-198 discloses that the insertion of a needle into a patient's skin is primarily determined by the characteristics of the needle rather than the characteristics or structure of the needle support. Needle insertion into a patient's skin is generally classified into three phases that affect the depth of injection. The first phase corresponds to the initial contact between the needle and the skin, where tissue deforms but the skin surface is not pierced. The second phase refers to the piercing of the skin and the relaxation of the skin when the insertion force of the needle ceases. The third phase is the withdrawal of the needle and the outward stretching or extension of the skin as the needle is withdrawn.

[0004] Various injection devices already manufactured do not have a support structure in contact with the skin during injection or needle withdrawal. Other devices have also been proposed, wherein the end faces of these other devices are positioned to contact the skin surface to limit the depth of penetration into the patient.

[0005] Pen-injector infusion devices have been developed to facilitate self-administration of intravenous medications. Pen needles are components of needle-based injection systems and include a double-ended cannula assembled into a plastic hub using an adhesive. The hub has internal threads so that it can be attached to a pen-injector device. The pen needle attachment allows the proximal end of the cannula to penetrate through a rubber septum of a medication reservoir to create a fluid flow path. For many diabetics, maintaining glycemic control is achieved by performing multiple injections of insulin into subcutaneous (SC) tissue daily, and the use of pen-injector infusion devices has evolved as a more convenient, discreet alternative to syringes and vials. A number of pen-injectors are available on the market in single-use or multi-use configurations, each providing various patient-centric features. The distal pen needle cannula interfaces with the infusion site to provide a conduit for infusion. The design of the pen needle is intended to achieve consistent infusion into the target tissue space, minimize leakage of the injection, and reduce pain / discomfort and side effects associated with injections such as bleeding and bruising. The success of the injection is determined by the primary design features, needle length / gauge and hub face geometry, and the mechanical structure of the infusion system and injection technique.

[0006] Injections can be performed in the intradermal region, subcutaneous region, intramuscular (IM) region of the skin. For many types of injectable medications, including insulin, the SC region is preferred for performing injections. See, e.g., Lo Presti et al., Skin and subcutaneous thickness at injecting sites in children with diabetes: ultrasound findings and recommendations for giving injection, Pediatric Diabetes (2012).

[0007] The length of the needle, such as a needle having a length of about 4 mm to 5 mm, is suitable for injecting medication to a specific target depth in the subcutaneous region. The present invention provides a structure so that the needle can be consistently inserted to the desired target depth. Existing pen needles have a cannula supported on an axial strut extending from the hub. The strut forms a narrow portion and a relatively wider base that does not contact the skin during injection. In other pen needles known in the art, the distal face of the hub that is placed against the injection site can be relatively large, and can be provided with a slight taper at the edges. When the cannula is inserted at an angle relative to the patient's skin, the edges of the hub can engage the skin.

[0008] Although the existing devices are generally suitable for the intended use, there is a continuing need for improved devices for controlling the penetration depth of a cannula for infusion of a medicament or drug to a selected target area. SUMMARY

[0009] The present invention relates to injection devices and, in particular, to needle hubs for use with injection devices such as pen injectors. The present invention further relates to injection devices for injecting a medicament, drug or other substance into a patient at a desired depth relative to the surface of the skin. The needle hub has a hub face forming a contact surface for contacting the skin and includes a predetermined shape, size and geometry for controlling and optimizing the penetration depth of a needle or cannula and preventing the needle or cannula from penetrating below the desired depth. The needle hub optimizes the insertion depth so that the entire length of the exposed cannula or needle is inserted into the tissue, thereby providing increased consistency of insertion depth. The needle hub has a skin contact face having a shape and configuration that provides consistency of cannula insertion depth when a user applies a range of insertion forces.

[0010] The hub face in one embodiment of the present invention has a skin contact surface having a surface geometry dictated by the shape and size that controls the penetration depth of the needle. The face of the needle hub provides a surface area that concentrates the pressure applied to the skin at the injection site to maximize the insertion depth while controlling the penetration depth. In one embodiment, the needle hub has a shape and size that complements the needle length to minimize muscle penetration of the needle or cannula. The hub face can have a size and configuration that distributes the force in a selected surface area of the skin to prevent penetration below a predetermined depth while allowing substantially the entire length of the needle or cannula to penetrate the skin or tissue to the desired depth.

[0011] In one embodiment of the present invention, an injection device is provided having a needle hub with a contact face having an area surrounding the base of the needle to concentrate the pressure or force against the skin and a peripheral feature to control the insertion depth by limiting the deformation of the skin during insertion. The profile of the contact face provides the maximum penetration depth of the needle for a given needle length. The periphery of the needle hub has a shape that distributes the pressure or force applied by the user to a predetermined surface area of the skin when the needle hub is fully engaged with the skin surface. The shape and size of the periphery of the needle hub controls the deflection and distortion of the skin at the injection site by distributing the insertion force over a surface area of the skin thereby limiting the penetration of the needle and the displacement of the skin.

[0012] Yet another feature of the present invention is to provide a needle hub having a contact surface with a predetermined profile to provide a desired pressure distribution that enhances the patient comfort perception. In the illustrated embodiment, the contact surface of the needle hub has a conical or convex shape.

[0013] In one embodiment of the present application, the hub has a contact surface that is shaped and sized to provide consistent infusion of a range of infusion volumes of a substance and to provide consistent and reproducible infusion results by the same operator and different operators.

[0014] The hub of the present application also provides a skin contact surface that minimizes injection side effects such as leakage, edema and redness at doses of 1-60U. The contact surface is shaped and sized to provide a low level of perceived pain and discomfort to the user. The hub of the present application also provides a lower / shorter perceived profile that reduces anxiety of use.

[0015] One embodiment of the present application provides a hub for use primarily with pen injector devices, wherein the skin contact surface of the hub is shaped and sized to reduce the effects of different injection techniques between different users and to provide consistent introduction for short pen needles used for subcutaneous infusion. The hub is configured to provide optimal penetration depth and infusion of the injected substance by controlling the deformation of the skin surface when the hub is pressed against the skin of a patient.

[0016] These and other objects of the present application are achieved by providing a hub for a pen needle, the hub having a skin contact surface shaped to form an initial contact surface area of about 1 mm 2 to 5 mm 2 . In yet another embodiment, the initial surface contact surface area can be about 1-10 mm 2 . The hub is shaped such that the contact surface (when it is in full contact with the skin) has a surface area of about 5-50 mm 2 . In one embodiment, the full contact surface area can be about 15 mm 2 to about 35 mm 2 .

[0017] The features of the present application are achieved substantially by providing a hub configured for coupling to a pen injector infusion device, wherein the hub includes a body having a proximal end and a distal end, wherein the proximal end is configured for coupling to a pen injector infusion device. A cannula is coupled to the body and extends from the distal end for insertion into a patient. The distal end of the hub abuts the skin surface of a patient when the cannula is inserted into the skin of the patient. A contact surface has a first portion that surrounds the base of the cannula and forms an annular first contact surface having a surface area of about 1-5 mm 2 . The contact surface has a second portion that surrounds the annular first contact surface and is spaced radially outwardly therefrom and forms an annular second contact surface, wherein the first and second contact surfaces have a surface area of about 15-50 mm 2mm2. In yet another embodiment, the annular first contact surface and the annular second contact surface can have a combined surface area of about 15 mm 2 to about 35 mm 2 In one embodiment, the conical shaped component on the inner side forms the first contact surface and extends axially about 0.5 mm distance relative to the outer ring which forms the second contact surface.

[0018] The present invention is further characterized by providing a method of injecting a medicament with a medicament pen, the injection being performed by providing a medicament pen having a hub with a body for coupling to a pen needle, a strut extending from a distal end of the body, and a cannula coupled to the strut. The strut has a contact surface for contacting the skin of a patient when the cannula is inserted into the skin. The contact surface has a first portion surrounding the cannula forming an annular first contact surface having a surface area of about 1-5 mm 2 and a second portion surrounding the first portion and spaced radially outwardly from the first portion, the second portion forming an annular second contact surface, wherein the first and second contact surfaces have a combined surface area of about 15-35 mm 2 .

[0019] One feature of the present invention is to provide a hub having a skin contact surface with a generally conical shape and forming a convex surface. In one embodiment, the conical shaped skin contact surface has a centrally located conical shaped annular portion that protrudes from a distal face of the hub and has an axial height of about 0.3 mm to 0.7 mm relative to the convex surface. A cannula extends from a central portion of the annular portion for penetrating the skin. In one embodiment of the present invention, the convex contact surface of the hub has an axial height of about 0.5 mm to 2.0 mm and a width of about 5.0 mm to 8.0 mm (and typically about 5.0 mm to 7.0 mm) to provide sufficient surface area and a suitable shape to contact the skin and provide a controlled depth of penetration by the cannula into the skin.

[0020] Yet another feature of the present invention is to provide an injection device having a cannula for penetrating the skin and wherein the injection device has a skin contact surface surrounding a base of the cannula, the skin contact surface having a generally convex surface with a width and a height to control the depth of penetration. The height and width of the convex surface are used to control the skin deformation during insertion of the cannula to prevent the cannula from penetrating the skin to the muscle layer.

[0021] The convex curved contact surface of the hub provides a surface area for contacting the injection site of the patient to provide greater patient comfort and stability. Insulin and other diabetes related medications are often infused into the subcutaneous region, so controlling the penetration depth of the needle is desirable.

[0022] It will be understood that each of the features of the preferred or optional features of the various embodiments can be combined with other features or with features described as being combined with one or more particular features, and also with one or more other features of other embodiments.

[0023] These and other features of the present application will become apparent from the following detailed description of the application taken in conjunction with the accompanying drawings. Figure One Various embodiments of the present application are disclosed. BRIEF DESCRIPTION OF DRAWINGS

[0024] The following is a brief description of the drawings, in which:

[0025] Figure 1 is a side view of the hub in one embodiment of the present application;

[0026] Figure 2 is a top perspective view of the hub of Figure 1

[0027] Figure 3 is a top view of the hub in the embodiment of Figure 1

[0028] Figure 4 is a bottom view of the hub of Figure 1

[0029] Figure 5 is a cross-sectional side view of the hub;

[0030] Figure 6 is a side view of the hub showing the initial insertion of the cannula into the skin and the initial penetration depth into the skin;

[0031] Figure 7 is a side view of the hub showing the cannula inserted into the skin and relaxed to conform to the end surface shape of the hub and showing the depth of penetration; and

[0032] Figure 8 is a graph showing the in-dwelling depth density profile of the needle. DETAILED DESCRIPTION

[0033] ​​​Pen needles of the present invention relate to needle hubs attached to pen injector devices for injecting drugs or other substances into a patient: The terms needle and cannula are used interchangeably herein to refer to a tubular member having a sharp end for insertion into an injection site on a subject. The distal direction is the direction toward the injection site, while the proximal direction is the opposite direction. The axial direction refers to the direction along or parallel to the longitudinal axis of the needle and needle hub, and the radial direction refers to the direction perpendicular to the axial direction. Pen injector devices can be standard devices as known in the art, where the needle hub can be attached to the end of the pen injector for infusion of a substance into a patient. After use, the needle hub is removed and discarded, and replaced with a new needle hub for a subsequent injection.

[0034] The intradermal layer of an adult human has a thickness of about 2 mm to 3 mm, so the depth of an intradermal injection is in the range of about 0 mm to 3 mm measured from the outer surface of the skin. The thickness of the subcutaneous layer varies depending on the age, sex, body mass index (BMI) of the patient, and the site of the body to which the injection is given. The subcutaneous region has an average thickness of about 7 mm to about 15 mm. Insulin is preferably infused into the subcutaneous region.

[0035] The present invention relates to injection devices and in particular to needle hubs having cannulas of predetermined length for penetrating the skin to a predetermined penetration depth. The needle or cannula can be, for example, 4-8 mm and can be 31-33 gauge. In other embodiments, the needle or cannula can be other gauges suitable for the intended purpose. The needle hub has a skin contact surface for contacting the skin and deforming the skin when the cannula penetrates the skin to provide a controlled penetration depth. The contact surface has a predetermined shape, width and height to control the deformation of the skin during insertion of the cannula to limit the depth of penetration into the skin by distributing the insertion force over an appropriate surface area of the skin. When the device has a small and narrow skin contact surface of about 3 mm 2 When a device having a small and narrow skin contact surface of about 3 mm or less is pressed against the skin during use, the applied force of the device can compress the skin around the cannula. The concentrated compression can cause the cannula to penetrate into the skin below the desired depth. The outer perimeter of the needle hub of the present invention distributes the pressure to limit the compression of the skin and the depth of penetration of the cannula. In one embodiment, the needle hub has a surface area that contacts the skin in a shape and configuration such that the entire length of the cannula is inserted into the tissue by normal or customary insertion forces applied by the user. The shape and configuration of the contact surface provides improved consistency of injection depth into the skin over a range of applied forces.

[0036] The skin contacting surface of the pen needle device that surrounds the cannula has a width and height configured to contact the skin to distribute contact pressure and limit or control the cannula penetration depth. In one embodiment of the present invention, the pen needle device is configured to achieve a cannula penetration of about 4 mm. The skin contacting surface is further configured to control the shape, width and depth of the skin surface deformation when the device is pressed against the skin during penetration of the cannula. The width corresponds to the surface area of the skin that is contacted during initial insertion of the cannula into the skin and during the typical force exerted by the user to inject or infuse a medicament. The height refers to the axial distance between the outer peripheral edge of the contacting surface and the base of the cannula that forms the proximal end of the contacting surface. The surface area and shape of the contacting surface can be configured such that the entire length or substantially the entire length of the needle or cannula penetrates the skin while controlling the penetration depth.

[0037] The hub in one embodiment has a first contact surface area for first contacting the skin about 1.0 mm 2 to about 5.0 mm 2 around the cannula. In other embodiments, the first contact surface has a surface area of about 1.0 mm 2 to 4.0 mm 2 . A second contact surface of annular shape surrounding the first contact surface area and spaced radially outwardly and axially from the first contact surface area has a surface area of about 10.0 mm 2 to 40 mm 2 . In various embodiments, the skin contacting surface of the hub has a surface area defined by the first and second contact surface areas of about 15.0 mm 2 to 50.0 mm 2 . In one embodiment, the combined surface area of the first and second contact surface areas can be about 15.0 mm 2 to 35.0 mm 2 . In yet another embodiment, the combined surface of the first and second contact surface areas can be about 15.0 to 20.0 mm 2 . In yet another embodiment, the first contact surface area can have a surface area of about 1 mm 2 to 5 mm 2 and the second contact surface area can have a surface area of about 10 mm 2 to 30 mm 2 for providing a combined surface area of about 15 mm 2 to about 35 mm 2 .

[0038] The skin contact surface of the hub can have a generally circular shape and a rounded or curved convex profile with the cannula positioned along a central axis of the circular skin contact surface. The curved or sloped surface of the contact surface converges to a central point at the base of the cannula extending from the hub to define an outer lateral end of the contact surface furthest from the base of the contact surface. The cannula in this embodiment has a length of about 4.0 mm to about 6.0 mm to penetrate the skin to a depth and layer of the skin to infuse the drug, and particularly insulin, to a target depth of the skin for a particular medication treatment. In yet another embodiment, the cannula has a length of about 3.5 mm to about 8.0 mm.

[0039] In the illustrated embodiment, the hub has a skin contact surface having a pronounced convex shape extending from an outer peripheral edge of the hub to a distal axial end of the hub contact surface at the base of the cannula such that the skin contact surface has a generally hemispherical or conical shape to contact the skin during initial penetration of the cannula and during full insertion for infusion of the medicament. The convex surface of the skin contact area of the hub can have a width or diameter of about 2.0 mm to 8.0 mm and an axial height of about 0.5 mm to about 1.0 mm measured from an outer peripheral edge of the contact surface formed by the outer ring to an outermost central conical portion of the contact surface surrounding the cannula and axially spaced from the outer peripheral edge. In one embodiment, the axial face forming the convex surface of the hub can have a diameter of about 5.0 mm to 9.0 mm providing a total surface area of about 20.00 mm 2 to about 70.0 mm 2 and typically about 25.0 mm 2 to 65.0 mm 2 . In yet another embodiment, the axial face has a diameter of about 5.0 mm to about 7.0 mm.

[0040] In one embodiment, the convex skin contact surface has a height of about 0.5 mm and a combined or total skin contact surface area formed by the first contact surface area and the second contact surface area of about 15 mm 2 to 20 mm 2 . The first contact surface area and the second contact surface area can be spaced apart by a distance of about 2 mm to 3 mm. The height is measured as an axial distance of the outer edge of the hub and the outer ring to the axial face of the central inner conical member of the hub. The total axial surface area of the hub is formed by the first contact surface, the second contact surface, and the area between the first contact surface and the second contact surface can be about 25.0 mm 2 to 65.0 mm 2 .

[0041] The relationship between the diameter, height, and total surface area of the contact surface area provides a controlled penetration depth of the cannula when the cannula is inserted into the skin and a range of applied force is typically applied to the hub. The hub as shown is primarily directed to use with a pen-injector infusion device. In other embodiments, the configuration of the contact surface is suitable for use with a reusable or disposable injection device, an auto-injector, a syringe, a patch pump, or other infusion device that requires contact with the skin.

[0042] In one embodiment of the application, the skin contact surface of the hub has a generally conical shape with an inner conical shape member at the center of the conical shape and an outer ring radially spaced outward from and surrounding the inner cone, forming an annular recess between the inner conical shape member and the outer ring. The outer ring in one embodiment forms the outer peripheral edge of the contact surface of the hub. The recess in one embodiment has a depth that enables the skin to contact the bottom of the recess when the device is pressed against the skin during insertion of the cannula into the skin. In other embodiments, the recess has a depth that does not enable the skin to contact the bottom of the recess. In one embodiment, the depth and radial width of the recess are configured to form a portion of the contact surface to control the deformation of the skin surface during penetration of the cannula to control the penetration depth. The recess can have a depth of about 0.4 mm to 2.0 mm. The recess can be defined by the outer ring at the outer peripheral edge of the hub and the inner conical ring member surrounding the cannula at the center of the contact surface. In other embodiments, the recess formed in the skin contact surface can have a volume of about 6 μl to 35.0 μl.

[0043] The inner conical shape member forms an inner annular ring having a diameter of about 2.0 mm to about 4.0 mm (typically about 2.0 mm to 3.0 mm) and an axial contact surface area in the range of about 1.0 mm to 5.0 mm. 2 to 5.0 mm 2 In one embodiment, the outer ring can have an axial surface area of about 10.0 mm 2 to 35.0 mm 2 When the cannula is first inserted into the skin, the inner conical shape member can form an initial contact surface. The inner cone can have an axial height of 0.3 mm - 0.7 mm relative to the axial face of the outer ring. The hub can have an initial contact surface area of 1 - 15 mm 2 and a fully seated surface area of 5 - 50 mm 2 In one embodiment, the initial contact surface area is formed by the axial face of the inner conical shape member.

[0044] The outer ring forming the second contact surface can have an axial surface area of about 10.0 - 30.0 mm 2The axial surface area is used to contact the patient's skin. The outer ring may have an axial height of approximately 0.4 mm to approximately 1.25 mm from the bottom of the recess. Twisting and deformation of the skin surface can occur during cannulation or needle insertion or removal from the patient's skin, which can affect the penetration depth of the cannula. (Reference) Figures 1 to 7 One embodiment of the invention is a needle hub 10 having a body 12 for connection to a pen needle and a support 14 for supporting a cannula 20 and forming a surface for contact with the patient's skin during insertion and injection. The body 12 has a generally cylindrical shape and has sidewalls 16 and a shoulder 18 extending inward toward the central axis of the body. In the illustrated embodiment, the shoulder 18 extends generally perpendicular to the longitudinal axis of the body.

[0045] The support 14 extends axially from the shoulder 18 and forms an axial surface 24 that supports the cannula and defines a skin contact surface. The support 14 has an axial height or length extending a distance from the body 12 such that only the surface features of the support contact the skin during use. The axial surface 24 of the support 14 forms the skin contact surface of the needle hub during use. A protruding central conical member 26 is formed on the axial surface 24, which protrudes axially from the support 14 to form a first portion of the contact surface and a first contact surface. An annular outer ring 28 formed at the outer periphery of the support forms a second contact surface area. An annular recess 30 is formed between the central conical member 26 and the outer ring 28. The axial surface 24 and the skin contact surface are defined by the outer peripheral edge of the outer ring 28 and the inner central conical member 26. In the illustrated embodiment, the annular recess 30 has a bottom surface 34 having a generally conical shape extending between the central conical member 26 and the outer ring 28, such that the bottom surface 34 extends outward from the inner central conical member 26 toward the outer ring 28 at a certain slope. In the illustrated embodiment, the annular recess 30 has a generally uniform depth relative to the inner central conical member 26 and the outer ring 28. The bottom surface 34 forms a continuous surface of generally uniform depth and has a conical curvature that complements the curvature formed by the axial surfaces of the inner central conical member 26 and the outer ring 28.

[0046] A central conical member 26 extends from the axial surface of the support 14 to define the axial height, relative to... Figure 1The axial height of the center conical shaped member 26 is greater than the axial height of the outer ring 28 in terms of the axial dimension of the hub. The height of the center conical shaped member 26, the height of the outer ring 28, and the difference between the two heights, enhance the distortion and deflection of the skin during initial insertion and after skin relaxation during use to control the penetration depth of the cannula. The axial spacing between the axial face of the center conical shaped member 26 and the axial face of the outer ring 28 enables the center conical shaped member 26 to initially contact the skin by the first contact surface to deform the skin and concentrate the pressure at the center member. The outer ring 28, which forms the second contact surface, subsequently contacts the skin to limit and control the penetration depth and deformation of the skin by distributing the pressure over the entire width of the axial face and by the height differential in the center conical shaped member 26.

[0047] The center conical shaped member 26 in the embodiment shown has a generally annular ring shape positioned in the axial center of the strut 14 and extends in the axial direction of the strut 14. The annular axial surface 38 of the center conical shaped member 26 faces outward in the axial direction to form an inner ring and define a first skin contact portion that forms an annular first contact surface of the skin contact surface of the hub 10. In the embodiment shown in Figures 1 to 3 and Figure 5 The center conical shaped member 26 in the embodiment shown has a generally annular ring shape positioned in the axial center of the strut 14 and extends in the axial direction of the strut 14. The annular axial surface 38 of the center conical shaped member 26 faces outward in the axial direction to form an inner ring and define a first skin contact portion that forms an annular first contact surface of the skin contact surface of the hub 10. In the embodiment shown in

[0048] As shown in Figures 1 to 3 and Figure 5 The center conical shaped member 26 has an annular outer surface 36 that forms a conical shape with the axial face 38. The outer annular surface 36 shown in the embodiment extends generally in the axial direction and forms a slightly outwardly tapering shape. In the embodiment shown, the axial face 38 has a surface that extends outwardly relative to the central longitudinal axis of the hub and the center conical shaped member 26. In the embodiment shown, the axial face 38 of the center conical shaped member 26 has a slight curvature that forms a conical shape that curves from the inner edge of the center conical shaped member 26 toward the outer peripheral edge of the center conical shaped member 26 at the inner side to form a first portion of the conical shaped skin contact surface. As discussed previously, the axial face 38 defines the first contact surface and generally has a surface area of about 1 mm 2 to about 5 mm 2 .

[0049] The outer ring 28 has an axially facing surface 40 that is slightly curved with a rounded inner edge and a rounded outer edge that converges with the outer annular surface of the post 14. The axially facing surface 38 of the inner, central conical shaped member 26 is slightly inclined outwardly toward the outer peripheral edge of the post 14 to form a generally conical shaped contact surface. The axially facing surface 38 forms a first portion of the contact surface of the post 14. The axially facing surface 40 of the outer ring 28 forms a second contact surface portion of the contact surface.

[0050] The axially facing surface 40 of the outer ring 28 and the axially facing surface 38 of the inner, central conical shaped member 26 in the embodiment shown are oriented to form a curvature having a radius of curvature of about 6 mm to about 9 mm. The axially facing surface 40 of the outer ring can form a second contact surface having a surface area of about 10.0 mm 2 to about 40.0 mm 2 . The outer ring 28 and the axially facing surface 40 can have a diameter of about 5.0 mm to 7.0 mm. In one embodiment, the axially facing surface 38 can have a generally flat surface that extends perpendicular to the longitudinal axis of the hub and perpendicular to the axis of the central conical shaped member.

[0051] In one embodiment, the hub has an axially facing surface of about 5.0 mm to about 7.0 mm diameter formed by the inner, central conical shaped member 26 having an annular axially facing surface 38 with a surface area of about 5.0 mm 2 to about 10 mm 2 , the annular outer ring 28 having an annular axially facing surface 40 with a surface area of about 25.0 mm 2 to 40 mm 2 , wherein the combined surface area of the first contact surface formed by the axially facing surface 38 of the central conical shaped member 26 and the second contact surface formed by the axially facing surface 40 of the outer ring 28 is about 30.0 mm 2 to about 50.0 mm 2 . In one embodiment where the outer dimensions of the outer ring and the contact surface are about 6-8 mm, the inner ring and the outer ring can be spaced apart a distance of about 2 mm to 3 mm. In yet another embodiment, the first contact surface can have a surface area of about 5-10 mm 2 and the second contact surface can have a surface area of about 10-25 mm 2 to provide a combined surface area of about 15-35 mm 2 .

[0052] The inner-side central conical shaped member and the outer-side ring can be axially spaced apart by a distance of about 0.3 mm to 1.0 mm. In another embodiment, the inner-side central conical shaped member and the outer-side ring are axially spaced apart by about 0.3 mm to 0.7 mm, or substantially 0.5 mm to 1.0 mm. In yet another embodiment, the inner-side central conical shaped member can have a radial width, measured from its inner edge to its outer edge, of about 0.8 mm to 1.2 mm, typically about 1.0 mm. In one embodiment, the inner-side central conical shaped member can have a surface area of about 3.0 mm 2 to 4.0 mm 2 , in another embodiment, the inner-side central conical shaped member can have a surface area of about 3.5 mm 2 to 3.7 mm 2 . The outer-side ring 28 can have a radial width, measured from its inner edge to its outer edge, of about 1.2 mm to 1.7 mm, typically about 1.5 mm. The outer-side ring can have a surface area of about 14.0 mm 2 to 16.0 mm 2 , in one embodiment, the outer-side ring can have a surface area of about 15.0 mm 2 to 15.5 mm 2 . The needle can be a 5-bevel needle or a cannula.

[0053] As shown in FIGS. Figure 6 and Figure 7 , the hub 10 contacts the patient's skin 42 during insertion of the cannula 20 to position the cannula at a desired depth in the skin. As shown in FIG. Figure 5 , the cannula 20 is inserted into the skin 42 with the axial contact surface of the inner-side central conical shaped member 26 making initial contact with the skin to depress the skin. Further insertion of the cannula 20 causes the axial contact surface of the outer-side ring 28 to contact the skin 42, limiting deformation of the skin and controlling the depth of penetration of the cannula 20 into the skin. Referring to FIG. Figure 6 , the inner-side central conical shaped member 26 of the strut 14 of the hub 10 initially contacts the skin 42 and creates a distortion of the skin by the downward insertion force. As shown in FIG. Figure 6 , the outer-side ring 28 contacts the skin to increase the surface contact with the skin and distribute the pressure to limit the depth of penetration. The shape and size of the hub, including the height of the inner-side central conical shaped member 26 relative to the outer-side ring 28 and the surface area of the combination of the inner-side central conical shaped member and the outer-side ring, affect the degree of compression and relaxation of the tissue under a given applied force. After insertion, as shown in FIG. Figure 7 , the skin 42 relaxes such that the cannula tip is at a desired depth for infusion of the injection substance. The depth of penetration can be expressed as follows.

[0054] f(Depth) = L + lo*σ / E + ψ

[0055] where

[0056] L = effective needle length

[0057] E = tissue modulus of elasticity

[0058] σ = F n / A compressive stress

[0059] ε = Δl / lo deformation due to applied stress

[0060] F n = normal force

[0061] A c = cross sectional surface area, = f(z)

[0062] lo = uncompressed length

[0063] Δl = change in length

[0064] ψ = bulge parameter correction - determined from empirical values

[0065] f(z) = initial surface area, cone height, cone height > z > 0 = increasing surface area, z > cone height

[0066] *Surface area (SA) depends on the unique surface geometry characteristics. A physical model can be used to determine the contact surface area with respect to the Z axis displacement of the needle, thus enabling the f(z) function to be generated.

[0067] A layer of tissue model is provided for illustrative purposes to explain the working principle of the present invention.

[0068] The needle penetration depth based on the shape and configuration of the skin contact surface is shown in Figure 8 . Figure 8 is a graph showing a density plot indicating the needle's placement into the tissue to a specific target depth. In the graph, device A corresponds to the device as shown in Figure 1 . The measurement is made from the skin surface to the top of the 2U reservoir and represents the depth of needle penetration into the tissue without the eddy current created by the non-uniform reservoir distribution that can accompany larger volume infusions. Devices B and C are prior art devices. The needle's placement depth means that the level of concentrated applied force is similar to historical data where the applied force was not measured.

[0069] The needle hub 10 is configured to be used with a pen-type injector. As Figure 4 and Figure 5The body 16 of the hub 10 shown in the middle has a wall with threads 44 for connection to a pen-type syringe in a typical manner. A cannula 20 extends downward into the center of the hub for piercing a septum of a cassette containing a substance to be infused. In this embodiment, an internal rib 46 extends the entire length of the top wall 48 from the strut 14 to provide additional strength and integrity to the hub 10. An internal strut 50 extends from the top wall 48 a length corresponding to the axial length of the strut 14 for supporting the cannula 20. The rib 46 extends between the inside surface of the strut 14 and the outside surface of the internal strut 50 for supporting the strut 50 and the cannula 20 against bending or deflection of the cannula 20 and strut 50 when connected to a pen-type syringe. In the embodiment shown, the rib 46 has an axial length to stabilize the strut 50.

[0070] The venous infusion system is characterized by the interface between the device and the infusion site, at which point the tissue biomechanics influence the function of the device. The construction and design of the device are adjusted to accommodate these factors. The complex relationship between the infusion mechanism, the biological interface, and the physical and chemical properties of the drug that determine infusion performance are not well understood. Existing devices typically focus on the characteristics of the needle or cannula, such as length, gauge, penetration, lubrication, and flow characteristics. For a particular application, pen needle design and hub face geometry favor consistent needle depth placement in the target tissue space. These features provide distinguishable construction to improve comfort during use, reduce the risk of intramuscular injection, and reduce the sensation of needle phobia. The face geometry of the hub, the needle length and gauge, and the structure of the infusion system and injection technique together determine the success of the device.

[0071] The contact surface of the hub has a width and height to control the deformation in the skin and thus the penetration depth of the cannula. The shape and size of the contact surface distribute the applied pressure when fully engaged with the skin surface. Such a profile and pressure distribution provides improved comfort for the patient. The height and surface area of the hub, as well as the peripheral surface area, affect the degree of compression and relaxation of the tissue for a given applied force.

[0072] In the described embodiment, the central conical shaped member 26 and the outer ring 28 have a generally cylindrical or annular shape and extend axially from the support 14, with the axial surfaces of both the central conical shaped member 26 and the outer ring 28 defining the skin contact surface of the hub 10. The outer ring 28 has a diameter that contacts the skin during use to control the deformation of the skin along with the size of the central conical shaped member 26 on the inside. In the illustrated embodiment, the central conical shaped member 26 on the inside has an axial height or length that is greater than the axial height of the outer ring 28 to provide initial contact with the skin. The contact is first made by the central conical shaped member 26 on the inside, then by the outer ring 28 as the cannula 20 is further inserted and the skin is relaxed. The size of the central conical shaped member on the inside and the outer ring is selected based on the desired penetration depth and cannula length. The embodiments described herein are exemplary in size, which can be modified as needed to provide the desired depth of cannula penetration during use.

[0073] The depth of the annular recess 30 can vary depending on the desired depth of penetration of the cannula 20. In the illustrated embodiment, the radial dimension of the annular recess 30 is greater than the combined radial dimension of the central conical shaped member on the inside and the outer ring. Generally, the greater the depth of the recess, the smaller the distal end face contact surface area and the greater the skin surface deformation enables the cannula to penetrate deeper. The angle of the axial surfaces of the central conical shaped member on the inside and the outer ring that form the contact surface can be selected based on the desired outcome. The annular recess 30 can have a depth relative to the axial face of the central conical shaped member 26 on the inside and the outer ring 28 such that the skin can contact the bottom surface of the annular recess 30 to control the skin deformation between the central conical shaped member 26 on the inside and the outer ring 28. In other embodiments, the depth of the annular recess 30 can be deep enough such that the skin does not contact the bottom of the annular recess 30 during use.

[0074] A hub device is suitable for use in a method for reducing shallow injections and for injecting a medicament into a patient. The method includes providing a pen body having a medicament compartment and a distal end configured to receive a pen needle. The pen needle includes a hub having a base with a recess on a proximal side for receiving and coupling to the pen body. A distal face and an opening of the pen needle extend between the proximal side and the distal face. The foregoing description of preferred embodiments should not be construed as limiting the invention defined by the appended claims. The present disclosure is intended to enable a person of ordinary skill in the art to practice a variant of the described invention without departing from the scope of the invention. Numerical limitations in the specification and claims herein are understood to be limited by the modifier "about" such that minor deviations resulting in equivalent results are within the scope of the invention. Features disclosed in association with one embodiment or dependent claim limitation can be incorporated into another embodiment or combined with a different independent claim without departing from the scope of the invention.

Claims

1. A hub configured to be coupled to a pen needle infusion device, the hub comprising, a body having a proximal end and a distal end, and a strut extending from the distal end of the body, the proximal end configured for coupling to the pen needle infusion device; and a cannula coupled to and extending from the post; The strut has an end wall whose outer surface forms a skin contact surface for contacting the skin surface of a patient when the cannula is inserted into the skin of the patient, the skin contact surface having an inner ring surrounding the cannula and forming an annular first contact surface having a surface area of 1 mm 2 to 5 mm 2 , and an outer ring surrounding the inner ring and spaced radially outwardly from the inner ring by a distance of 2 mm to 3 mm, thereby forming an annular second contact surface having a surface area of 10 mm 2 to 30 mm 2 , wherein the annular first contact surface and the annular second contact surface have a combined surface area of 15 mm 2 to 35 mm 2 and provide consistent infusion over a range of insertion forces. the end wall of the post has an inner surface having an inner post extending toward the proximal end to support the cannula, the inner surface having a plurality of radial ribs extending between the inner surface of the post and the inner post to stabilize the inner post.

2. The hub of claim 1, wherein, the skin contact surface has an annular recess between the annular first contact surface and the annular second contact surface, the annular recess having a depth of 0.4 mm to 2 mm.

3. The hub of claim 2, wherein, the annular first contact surface is positioned to contact the skin of a patient when insertion of the cannula deforms a skin surface, and the annular second contact surface contacts the skin when the skin contacted by the annular first contact surface is deflected.

4. The hub of claim 3, wherein, the skin contact surface of the hub has a substantially conical configuration having an axial height that satisfies the combined surface area to enable the cannula to penetrate the skin to a predetermined depth.

5. The needle hub of claim 4, wherein, the length and gauge of the cannula are adapted to the axial height of the combined surface area to enable the cannula to penetrate the skin to a predetermined depth.

6. The hub of claim 1, wherein, The annular second contact surface has a surface area of 15 mm 2 to 15.5 mm 2 and an outer diameter of 5 mm to 7 mm.

7. The hub of claim 1, wherein, the skin contact surface of the post has a substantially convex surface extending between the outer peripheral edge of the post and the cannula.

8. The hub of claim 1, wherein, the radius of curvature of the annular first contact surface surrounding the cannula is adapted to the radius of curvature of the annular second contact surface.

9. The hub of claim 1, wherein, the cannula has a length of 3.5 mm to 8.0 mm.

10. The hub of claim 1, wherein, The annular first contact surface and the annular second contact surface have a combined surface area of 15 mm 2 to 20 mm 2 of the first contact surface and the second contact surface.

11. The hub of claim 1, wherein, the skin contact surface has an annular recess between the annular first contact surface and the annular second contact surface, the annular recess having a depth of 0.4 mm to 1.0 mm.

12. The hub of claim 1, wherein, the inner ring is axially spaced from the outer ring by a distance of 0.3 mm to 1.0 mm.

13. The needle hub of claim 12, wherein, the inner ring is axially spaced from the outer ring by a distance of 0.3 mm to 0.7 mm.

14. The hub of claim 1, wherein, The annular first contact surface has a surface area of 1.0 mm 2 to 4.0 mm 2 .

15. The hub of claim 1, wherein, The annular first contact surface has a surface area of 3.0 mm 2 to 4.0 mm 2 .

16. The hub of claim 1, wherein, The annular first contact surface has a surface area of 3.5 mm 2 to 3.7 mm 2 .

17. The hub of claim 1, wherein, the annular first contact surface has a radial width of 0.8 mm to 1.2 mm, and the annular second contact surface has a radial width of 1.2 mm to 1.7 mm.

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