Patent Publication Number: US-2022211411-A1

Title: Needle assembly

Description:
TECHNICAL FIELD 
     The present disclosure relates to a needle assembly for ultrasound guided fenestration and/or transection of tissue and, more particularly, to a needle assembly in which a plunger-operated needle has a specific orientation with respect to an outer cannula. 
     BACKGROUND 
     Ultrasound guided musculoskeletal interventions are rapidly becoming more common and often offer an alternative to more costly and risky surgeries. Ultrasound guided fenestration of ligaments and tendons using a needle alone has been performed. Such needle fenestration, however, does not appear to offer a robust equivalent to endoscopic or open techniques because needling does not transect tissue in the manner a surgeon does with a scalpel. 
     SUMMARY 
     The present disclosure relates to a needle assembly for ultrasound guided fenestration and/or transection of tissue and, more particularly, to a needle assembly in which a plunger-operated needle has a specific orientation with respect to an outer cannula. 
     In certain aspects, a needle assembly is provided that includes an outer cannula having a longitudinally extending cannula wall with an inner surface and an outer surface. The inner surface of the cannula wall defines a cannula lumen extending longitudinally through the outer cannula. The cannula wall includes a distal end portion and a proximal end portion. The distal end portion of the cannula wall includes a sharpened tip. The needle assembly also comprises a plunger housing connected to the proximal end portion of the outer cannula and a plunger received in the plunger housing. The plunger has a longitudinally extending plunger wall with an inner surface and an outer surface. The inner surface of the plunger wall defines a plunger lumen extending longitudinally through the plunger. The plunger lumen is axially aligned with the cannula lumen. A proximal end portion of the plunger protrudes from the plunger housing. The inner surface of the plunger wall within the proximal end portion of the plunger has an orientation specific configuration. The needle assembly further comprises a spring received in the plunger housing and biasing the plunger in a proximal direction. A needle is receivable axially in the plunger lumen and in the cannula lumen. The needle has a longitudinally extending needle wall with an outer surface. A proximal end portion of the needle is receivable in the proximal end portion of the plunger. The outer surface of the needle wall in the proximal end portion of the needle has an orientation specific configuration that is complementary to and fits within the orientation specific configuration of the inner surface of the plunger wall. A cap is configured to cover the proximal end portion of the plunger and the proximal end portion of the needle when the needle is received in the plunger lumen and in the cannula lumen. 
     In certain aspects, a needle assembly is provided that comprises an outer cannula having a distal end including a sharpened tip, a proximal end, and an outer cannula lumen extending longitudinally therebetween. A plunger housing is connected to the proximal end of the outer cannula. A plunger is received in the plunger housing, the plunger having a distal portion, a proximal portion, and a plunger lumen extending longitudinally therebetween and being axially aligned with the cannula lumen. The proximal portion has a proximal face defining an orientation-specific opening. A spring is received in the plunger housing and biases the plunger in a proximal direction. A needle is receivable axially in the plunger lumen and in the cannula lumen. The needle has a distal portion, a proximal portion, and a needle lumen extending therebetween. The proximal portion has a proximal end key having an orientation-specific configuration complimentary to and releasably lockable into the orientation-specific opening in the proximal portion of the plunger. The needle assembly further includes an end cap configured to cover the proximal portion of the plunger and the proximal portion of the needle when the needle is received in the plunger lumen and in the cannula lumen. The needle assembly further comprises a handle extending laterally from the plunger housing and having a fixed orientation when the orientation-specific proximal end key of the needle locks into the complimentary orientation specific opening at the proximal portion of the plunger. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view, partly in section, of a needle assembly in accordance with an embodiment of the present disclosure; 
         FIG. 2  is a side view, partly in section, of the needle assembly of  FIG. 1  with certain components in different positions; 
         FIG. 3  is a perspective view, partly exploded, of certain components of the needle assembly of  FIG. 1 ; 
         FIG. 4  is another perspective view of certain components of the needle assembly of  FIG. 1 ; 
         FIG. 5  is still another perspective view of certain components of the needle assembly of  FIG. 1 ; 
         FIGS. 6A, 6B, and 6C  are schematic views of different cutting needle tips usable in the needle assembly of  FIG. 1 ; and 
         FIG. 7  is side view, partly in section, of a needle assembly in accordance with another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 through 5  illustrate a needle assembly  10  for ultrasound guided fenestration and/or transection of tissue, in accordance with an example of the present invention. The needle assembly  10  comprises an outer cannula  12 , a plunger housing  14 , a plunger  16 , a spring  18 , a cutting needle  20 , an end cap  22 , and a handle, which in the illustrated examples, is two finger grips  24 . 
     The outer cannula  12  includes a longitudinally extending cannula wall  30  that can be circular in cross-section. As best seen in  FIG. 5 , the cannula wall  30  has an inner surface  32  and an outer surface  34 . The inner surface  32  of the cannula wall  30  defines a cannula lumen  36  that extends longitudinally through the outer cannula  12 . The cannula wall  30 , as shown in  FIG. 1 , also includes a distal end portion  38  and a proximal end portion  40 . The distal end portion  38  of the cannula wall  30  is sharpened such that the cannula wall and the outer cannula  12  have a sharpened and pointed tip  42 . The proximal end portion  40  of the cannula wall  30  is fixed, secured, or permanently attached to the plunger housing  14 . 
     As best seen in  FIG. 3 , the plunger housing  14  can have a rectangular outer shape. The plunger housing  14  may be formed in two halves, as shown, to facilitate assembly of the plunger housing with the outer cannula  12  and the plunger  16 . The plunger housing  14  has a distal end portion  44  and a proximal end portion  46 . The plunger housing  14  also can have a cylindrical inner surface  48  that extends throughout the length of the plunger housing and that defines a housing bore  50 . The housing bore  50  extends through the entire length of the plunger housing  14  but can have different diameters along its length. In the distal end portion  44  of the plunger housing  14 , the housing bore  50  has a diameter that is the same as or slightly larger than the outer diameter of the cannula wall  30  of the outer cannula  12 . The proximal end portion  40  of the outer cannula  12  may thus be received in the housing bore  50  with a friction fit against the inner surface  48  of the plunger housing  14  so as to be fixed, secured, or permanently attached to the plunger housing. In addition or alternatively, the proximal end portion  40  of the outer cannula  12  may be fixed, secured, or permanently attached to the plunger housing  14  with adhesive or welding or any other suitable attachment technique. To help ensure that the proximal end portion  40  of the outer cannula  12  is properly positioned relative to the plunger housing  14 , the housing bore  50  in the distal end portion  44  of the plunger housing may have a second, smaller diameter to provide an abutment or wall  52  against which the proximal end of the outer cannula may abut. 
     Proximal of the wall  52 , the housing bore  50  increases in diameter to receive the plunger  16 . The plunger  16  includes a distal end portion  54 , an intermediate portion  56 , and a proximal end portion  58 . The distal end portion  54  and the intermediate portion  56  both can have cylindrical outer surfaces. The outer diameter of the distal end portion  54  is greater than the outer diameter of the intermediate portion  56  so that the distal end portion effectively provides a retaining flange. The retaining flange defined by the distal end portion  54  of the plunger  16  engages and retains one end of the spring  18 , which is shown schematically in  FIGS. 1 and 2 . The spring  18  is received in the housing bore  50  and may, for example, be a coil spring with an inner cylindrical space such that the spring may encircle the cutting needle  20 . The opposite end of the spring  18  is engaged by and retained by the wall  52 . The spring  18  thus tends to push or bias the distal end portion  54  of the plunger  16  away from the wall  52  or in a proximal direction. 
     To accommodate or allow a range of travel for the plunger  16 , the housing bore  50 , for a majority of its length, can have a diameter that is the same as or slightly larger than the diameter of the distal end portion  54  of the plunger. In the proximal end portion  46  of the plunger housing  14 , particularly at the proximal end of the plunger housing, the housing bore  50  can have a diameter that is the same as or slightly larger than the diameter of the intermediate portion  56  of the plunger  16 . The proximal end portion  46  of the plunger housing  14  thus effectively provides a retaining wall  60  to engage the distal end portion  54  of the plunger  16  and thereby limit travel of the plunger  16  in a proximal direction and help retain the plunger in the plunger housing. 
     The proximal end portion  58  of the plunger  16  can be located and always remain outside of the plunger housing  14 . The proximal end portion  58  also can have an outer periphery that is larger than the outer periphery of the intermediate portion  56  of the plunger  16 . The proximal end portion  58  of the plunger  16  thus limits the throw of the plunger  16  or, stated differently, the distance through which the plunger can travel in a proximal direction relative to the plunger housing  14  and the outer cannula  12 . In addition to the throw limitation provided by the proximal end portion  58  of the plunger  16 , further limits on the throw of the plunger may be provided by an optional adjustable washer (not shown) disposed around the outer surface of the intermediate portion  56  of the plunger between the retaining wall  60  of the proximal end portion  46  of the plunger housing  14  and the proximal end portion of the plunger. Such an adjustable washer would limit the proximal travel of the plunger  16  by contacting the retaining wall  60  before the proximal end portion  58  of the plunger. Such an adjustable washer would be movable axially to different positions along the outer surface of the intermediate portion  56  of the plunger  16  and fixed in placed in a desired position using a set screw or other locking mechanism. As shown, the proximal end portion  58  of the plunger  16  has an outer periphery or outer shape that is square. The proximal end portion  58  may, however, have a circular outer shape or any other convenient outer shape so long as the outer periphery of the proximal end portion is greater than the outer periphery of the intermediate portion  56 . 
     The proximal end portion  58  of the plunger  16  has a proximal end face  62 , which can engage a distal end face  64  of the end cap  22 . The end cap  22  is attached to the proximal end portion  58  of the plunger  16  via a hinge  66 , as shown schematically in  FIGS. 1 and 2 . The end cap  22  may thus be pivoted in a first direction around the hinge  66  away from the proximal end portion  58  of the plunger  16  so that the proximal end face  62  of the proximal end portion is exposed. The end cap  22  may also be pivoted in a second, opposite direction around the hinge  66  toward the proximal end portion  58  of the plunger  16  so that the proximal end face  62  of the proximal end portion is covered by the end cap. To retain the cap  22  in a position covering the proximal end face  62  of the proximal end portion  58  of the plunger  16 , the distal end face  64  of the end cap and the proximal end face of the proximal end portion  58  of the plunger  16  may have complementary configurations so that the end cap is held against the proximal end portion of the plunger via a friction fit or a snap fit. Alternatively, a latch mechanism (not shown) may have one portion attached to the end cap  22  and a second portion attached to the proximal end portion  58  of the plunger  16  so that the first and second portions of the latch mechanism may be engaged with one another to hold the distal end face  64  of the end cap against the proximal end face  62  of the proximal end portion of the plunger. Also, one or both of the distal end face  64  of the end cap  22  and the proximal end face  62  of the proximal end portion  58  of the plunger  16  may be formed with a groove  68  to receive a gasket (not shown), which provides a fluid seal between the cap and the proximal end portion of the plunger. 
     The plunger  16  has a longitudinally extending plunger wall  70 . The plunger wall has an inner surface  72  that extends throughout the length of the plunger. The inner surface  72  defines a plunger lumen  74  that also extends through the entire length of the plunger  16 . Throughout a majority of its length, the inner surface  72  can have a circular cross-section and, thus, the plunger lumen  74  can have a corresponding circular cross-section. Adjacent the proximal end face  62  of the proximal end portion  58  of the plunger  16 , however, the inner surface  72  has a different, orientation-specific cross-section or configuration. In particular, the proximal end face can define an orientation-specific opening. As shown in  FIGS. 3 and 4 , for example, the orientation-specific opening is square, but other configurations may be used, such as triangular or star-shaped. Suitable orientation-specific openings are selected in conjunction with the shape of the cutting needle  20 . Specifically, the cutting needle  20  is received in the plunger lumen  74 . The cutting needle  20  has a longitudinally extending needle wall  76 . The needle wall  76  has an inner surface  78  and an outer surface  80 . The inner surface  78  defines a needle lumen  82  that extends longitudinally throughout the entire length of the cutting needle  20 . Throughout its length, the inner surface  78  can have a circular cross-section and, thus, the needle lumen  82  can have a corresponding circular cross-section. For a majority of its length, the outer surface  80  also can have a circular cross-section. In a proximal end portion  84  of the cutting needle  20 , however, the outer surface  80  has a different, orientation-specific cross-section or configuration. In particular, the proximal portion of the needle can have a proximal end key having an orientation-specific configuration complimentary to and releasably lockable into the orientation specific opening in the proximal portion of the plunger. As shown in  FIGS. 3 and 4 , for example, the orientation-specific proximal end key is square, but other configurations may be used. 
     The orientation-specific configuration of the outer surface  80  of the needle wall  76  and thus the cutting needle  20  is complementary to and fits within the orientation-specific configuration of the inner surface  72  of the plunger wall  70  adjacent the proximal end face  62  of the proximal end portion  58  of the plunger  16 . The complementary orientation-specific configurations limit the number of orientations of the cutting needle  20  relative to the plunger  16  and to a longitudinal central axis of the plunger. With a square configuration, the number of possible relative orientations is limited to four. If the configuration were a triangle, the number of possible relative orientations would be limited to three. Other orientation-specific configurations might limit the number of possible relative orientations to two or one or to a number greater than four. 
     The complementary orientation-specific configurations of (a) the outer surface  80  of the needle wall  76  in the proximal end portion  84  of the cutting needle  20  and (b) the inner surface  72  of the plunger wall  70  adjacent the proximal end face  62  of the proximal end portion  58  of the plunger  16  facilitate the delivery of fluid, such as a liquid anesthetic, to the needle lumen  82  and also help to ensure a known orientation among the outer cannula  12 , including its sharpened and pointed tip  42 , a distal end portion  86  of the cutting needle, and the handle (e.g. finger grips  24 ). More particularly, the plunger wall  70  has an outer surface  88  that defines the outer periphery or outer shape of the plunger  16 . In the proximal end portion  58  of the plunger  16 , the outer surface  88  of the plunger wall  70  can have a square configuration with four sides  90 . At least one of the sides  90  is provided with a plunger port  92 , which is a bore or passageway that extends from the outer surface  88  of the plunger wall  70  to the inner surface  72 . The plunger port  92  thus permits the delivery of fluid from outside of the plunger  16  to the plunger lumen  74 . 
     Similarly, in the proximal end portion  84  of the cutting needle  20 , the outer surface  80  of the needle wall  76  also can have a square configuration with four sides  94 . At least one of the sides  90  can be provided with a needle port  96 , which is a bore or passageway that extends from the outer surface  80  of the needle wall  76  to the inner surface  78  of the needle wall. The needle port  96  thus permits the delivery of fluid from outside of the cutting needle  20  to the needle lumen  82 . The complementary orientation-specific configurations of (a) the outer surface  80  of the needle wall  76  in the proximal end portion  84  of the cutting needle  20  and (b) the inner surface  72  of the plunger wall  70  adjacent the proximal end face  62  of the proximal end portion  58  of the plunger  16  help to ensure that the plunger port  92  can be readily aligned with the needle port  96  to permit the delivery of fluid, such as a liquid anesthetic, to the needle lumen  82 . 
     In addition to or as an alternative to communicating with the needle port  96 , the needle lumen  82  may extend into a distal end face  98  of the proximal end portion  84  of the cutting needle  20 . By providing an appropriate cap port  100 , which is a bore or passageway that extends from an outer surface  102  of the end cap  22  to the distal end face  64  of the end cap, fluid may be delivered from outside of the end cap to the proximal end of the needle lumen  82 . Such a cap port  100  permits the delivery of fluid to the needle lumen regardless of the orientation of the cutting needle  20  relative to the plunger  16 , but adds some complexity to the design of the end cap  22 . 
     As mentioned above, the complementary orientation-specific configurations of (a) the outer surface  80  of the needle wall  76  in the proximal end portion  84  of the cutting needle  20  and (b) the inner surface  72  of the plunger wall  70  adjacent the proximal end face  62  of the proximal end portion  58  of the plunger  16  also help to ensure a known orientation among the outer cannula  12 , including its sharpened and pointed tip  42 , the distal end portion  86  of the cutting needle, and the handle such as finger grips  24 . More particularly, the distal end portion  86  of the cutting needle  20  may have a configuration, such as the slotted cutting tip shown in  FIG. 5 , that makes it important for the surgeon or other healthcare professional using the needle assembly  10  to be able confidently to know the orientation of the distal end portion without being able to see the distal end portion directly (i.e., without the aid of ultrasound, x-ray, or other imaging technology). 
     To facilitate grasping and manipulating the needle assembly  10 , the handle such as finger grips  24  are fixed, secured, or permanently attached to the plunger housing  14  in a desired orientation, such as, on opposites sides of the plunger housing. Because the outer cannula  12  is also fixed, secured, or permanently attached to the plunger housing  14 , the handle, such as finger grips  24 , are disposed in fixed or known orientation relative to the outer cannula, including its sharpened and pointed tip  42 . By appropriately arranging the complementary orientation-specific configurations of the outer surface  80  of the needle wall  76  in the proximal end portion  84  of the cutting needle  20  and the inner surface  72  of the plunger wall  70  adjacent the proximal end face  62  of the proximal end portion  58  of the plunger  16 , the handle, such as finger grips  24 , will also be disposed in fixed or known orientation relative to the cutting needle, including its specially configured distal end portion  86 . When the surgeon or other healthcare professional using the needle assembly  10  grasps the needle assembly by placing two fingers in the finger grips  24 , the surgeon or other healthcare professional will be able to establish the relative orientations of his or her hand grasping the needle assembly, the outer cannula, including its sharpened and pointed tip  42 , and the cutting needle  20 , including its specially configured distal end portion  86 . The surgeon or other healthcare professional using the needle assembly  10  will then be able confidently and reliably to manipulate the needle assembly to treat a patient. 
     The needle assembly  10  will typically be assembled, for example, at a manufacturing facility, such that the finger grips  24  and the proximal end portion  40  of the outer cannula  12  are fixed, secured, or permanently attached to the plunger housing  14 , the distal end portion  54  and the intermediate portion  56  of the plunger  16  are received in the plunger housing, and the spring  18  is also received in the plunger housing between the wall  52  and the distal end portion of the plunger. To prepare the needle assembly  10  for a particular procedure, a surgeon or other healthcare provider will select a particular cutting needle  20  with a desired configuration of its distal end portion  86  and move or pivot the end cap  22  around the hinge  66  away from the proximal end face  62  of the proximal end portion  58  of the plunger  16  to expose the open proximal end of the plunger lumen  74 . The surgeon or other healthcare provider will insert the distal end portion  86  of the cutting needle  20  lengthwise or longitudinally into the plunger lumen  74  and push the cutting needle through the central opening of the spring  18  and into the cannula lumen  36  of the outer cannula  12 . The surgeon or other healthcare provider will then manipulate the cutting needle  20  so that the orientation-specific configuration of the outer surface  80  of the needle wall  76  and, thus, the cutting needle fits within the orientation-specific configuration of the inner surface  72  of the plunger wall  70  adjacent the proximal end face  62  of the proximal end portion  58  of the plunger  16 . By pressing the cutting needle  20  until it seats within the orientation-specific configuration of the inner surface  72  of the plunger wall  70  adjacent the proximal end face  62  of the proximal end portion  58  of the plunger  16 , the surgeon or other healthcare provider will have established the relative orientations of the finger grips  24 , the outer cannula  12 , including its sharpened and pointed tip  42 , and the cutting needle, including its specially configured distal end portion  86 . To hold the cutting needle  20  in position, the cap  22  will be moved or pivoted around the hinge  66  until the distal end face  64  of the cap engages and locks into position relative to the proximal end face  62  of the proximal end portion  58  of the plunger  16 . 
     In use, after the assembly procedure set out above, the finger grips  24  of the needle assembly  10  will be grasped by the surgeon or other healthcare provider. If a procedure to be performed by the surgeon or other healthcare provider includes injecting a fluid, such as a liquid anesthetic, into a patient&#39;s tissue, a source of the fluid (not shown) will be connected in fluid communication with the plunger port  92  and/or the cap port  100 . The surgeon or other healthcare provider will then insert the sharpened and pointed tip  42  of the outer cannula  12  into the patient&#39;s tissue. When the outer cannula  12  is appropriately positioned in the patient&#39;s tissue, the surgeon or other healthcare provider may deploy the distal end portion  86  of the cutting needle  20  by pressing on the end cap  22  with his or her thumb to move the cap, the plunger  16  and the cutting needle in a distal direction so that the distal end portion of the cutting needle moves into the patient&#39;s tissue. The surgeon or other healthcare provider may then allow the distal end portion  86  of the cutting needle  20  to retract or move in a proximal direction into the outer cannula  12  under the bias of the spring  18 . The surgeon or other healthcare provider may repeat the process of distal extension and proximal retraction of the cutting needle  20  on an intermittent basis while manipulating the outer cannula  12  to adjust the position of the sharpened and pointed tip  42  of the outer cannula in the patient&#39;s tissue. 
     Although the handle is illustrated in the figures as opposing finger grips  24  having ring shapes to accommodate a user&#39;s fingers, the handle can have other configurations as well, such as a trigger shape that is pressed or pulled to actuate components of the needle assembly. 
     Once the cutting needle  20  is fully deployed or extended longitudinally relative to the outer cannula  12  to the full extent of the available travel of the plunger  16  in the plunger housing  14 , the surgeon or other healthcare provider may desire to keep the cutting needle fully deployed without applying continuous pressure on the cap  22 . To permit keeping the cutting needle  20  fully deployed without applying continuous pressure on the cap  22 , the needle assembly  10  may be provided with an optional lock assembly  104 . As shown in  FIGS. 1 and 2 , the optional lock assembly  104  includes a first latch portion  106  attached to the proximal end portion  58  of the plunger  16  and a second latch portion  108  attached to one of the finger grips  24 . Interference engagement between the first and second latch portions  106  and  108  holds the lock assembly  104  in its latched condition and keeps the cutting needle  20  fully deployed. Although a particular lock assembly  104  is shown, other lock assemblies may be used. 
     While the foregoing description of a procedure in which a surgeon or other healthcare provider uses the needle assembly  10  involves the use of a cutting needle  20  having a particular configuration for its distal end portion  86 , the surgeon or other healthcare provider may wish to employ a plurality of cutting needles  20  having different configurations for their respective distal end portions  86 . Because the cutting needle  20  is installed in the needle assembly  10  by inserting the cutting needle lengthwise or longitudinally into the plunger lumen  74  and the cannula lumen  36 , the cutting needle may be removed from the needle assembly by extracting the cutting needle lengthwise or longitudinally from the cannula lumen and the plunger lumen. A particular cutting needle  20  may thus be removed from the needle assembly  10  and replaced with a different cutting needle by a surgeon or other healthcare provider during a procedure without removing the needle assembly from a patient&#39;s tissue or adjusting the position of the sharpened and pointed tip  42  of the outer cannula  12 . The surgeon or other healthcare provider may thereby use different cutting needles  20  having different properties and capabilities, such different distal end portions  86  or different surface roughnesses, during a single surgical procedure. 
       FIG. 5  illustrates a particular configuration for the distal end portion  86  of the cutting needle  20 . Other configurations may be more appropriate for various procedures, however. Three such other configurations and other distal end portions  86   a ,  86   b , and  86   c  are shown in  FIGS. 6A, 6B, and 6C . In each of  FIGS. 6A, 6B, and 6C , a side view of each distal end portion  86   a ,  86   b  or  86   c  is shown above a view taken from a position ninety (90°) degrees away from the side view. Other configurations may also be provided for the sharpened and pointed tip  42  of the outer cannula  12 . One such other configuration and sharpened and pointed tip  42   a  is shown in  FIG. 7 , together with a different configuration for the distal end portion  86   a  of the cutting needle  20 . The cutting needle  20  may optionally not have an inner surface  78  or a needle lumen  82 . Such an optional solid needle would still have a distal end portion suitable for fenestration and/or transection, but would not be capable of delivering a fluid to a patient&#39;s tissue. 
     While the needle assembly  10  has been described as being configured to deliver a fluid to and through the needle lumen  82 , it may also be desirable to deliver fluid to or extract fluid from the cannula lumen  36 . To enable such delivery or extraction of fluid, a cannula port  110 , which is a bore or passageway that extends from the outer surface  34  of the outer cannula  12  to the inner surface  32  of the outer cannula, may be provided in the outer cannula. Such a cannula port  110  permits the delivery of fluid from outside the outer cannula  12  to the cannula lumen  36  and/or extraction of fluid from the cannula lumen to the outside of the outer cannula. 
     In addition, while the cutting needle  20  and the outer cannula  12  have been shown as being straight along their respective lengths, they may also be curved in a longitudinal direction. If the outer cannula  12  is curved, the cutting needle  20  may either have a complementary curved configuration along its length or be sufficiently flexible to accommodate being received in a curved outer cannula. Further, for certain procedures, the cutting needle  20  may not perform any cutting, but may simply be used for fenestration of a patient&#39;s tissue. In such a situation, the cutting needle  20  may simply have a pointed tip, like a typical injection needle. Further still, it may be desirable initially to position the outer cannula  12  using a solid stylet, which would be removed and replaced with a cutting needle  20  or fenestration needle after the outer cannula is appropriately positioned. 
     From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes, and/or modifications within the skill of the art are intended to be covered by the appended claims. For example, while the above described assembly has been disclosed with respect to a needle assembly, another instrument could be used with components of the assembly. For example, an instrument could be inserted into the cannula lumen of the the outer cannula and lock into the plunger proximal portion. Such an instrument could be used to cut tissue but also could be used to fenestrate tissue or be blunt to dissect or manipulate tissue. Also this instrument may or may not have an inner lumen itself through which fluid could be injected via a side port of the plunger. As such, the present disclosure covers various assemblies with an ultrasound guided surgical port through which a variety of instruments could be inserted in a locked orientation into an outer cannula.