Patent Publication Number: US-2022211527-A1

Title: Pliant members for receiving and aiding in the deployment of vascular prostheses

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/068,521 filed on Oct. 12, 2020 and titled “Pliant Members for Receiving and Aiding in the Deployment of Vascular Prostheses” which is a continuation of U.S. patent application Ser. No. 15/718,419, filed on Sep. 28, 2017, now U.S. Pat. No. 10,799,378 and titled, “Pliant Members for Receiving and Aiding in the Deployment of Vascular Prostheses,” which claims priority to U.S. Provisional Application No. 62/401,628 filed on Sep. 29, 2016 and titled, “Pliant Members for Receiving and Aiding in the Deployment of Vascular Prostheses,” all of which are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to medical devices. More specifically, the present disclosure relates to vascular prosthesis deployment devices, including deployment devices for self-expanding vascular prostheses such as stents and stent-grafts. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments disclosed herein will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. The drawings depict only typical embodiments, which embodiments will be described with additional specificity and detail in connection with the drawings in which: 
         FIG. 1  is a perspective view of a deployment device. 
         FIG. 2  is a cross-sectional view of a portion of the deployment device of  FIG. 1 . 
         FIG. 3A  is a perspective view of a ratchet slide component of the deployment device of  FIGS. 1 and 2 . 
         FIG. 3B  is a cross-sectional view of the ratchet slide of  FIG. 3A . 
         FIG. 4  is a side view of a carrier component of the deployment device of  FIGS. 1 and 2 . 
         FIG. 5  is a cross-sectional view of another portion of the deployment device shown in  FIGS. 1 and 2 . 
         FIG. 6  is a cross-sectional view of yet another portion of the deployment device shown in  FIGS. 1 and 2 . 
         FIG. 7  is a front view of the deployment device of  FIG. 1 , illustrating certain cross-sectional planes described herein. 
         FIG. 8  is a perspective view of the safety member of the deployment device of  FIG. 1 . 
         FIG. 9  is a side view of a portion of the delivery catheter assembly of the deployment device of  FIG. 1 . 
         FIG. 10  is a side view of another portion of the delivery catheter assembly of the deployment device of  FIG. 1 . 
         FIG. 11A  is a perspective view of another embodiment of a deployment device. 
         FIG. 11B  is a cross-sectional view of a portion of a delivery catheter assembly of the deployment device of  FIG. 11A  along plane  11 B- 11 B. 
         FIG. 11C  is a cross-sectional view of a portion of the delivery catheter assembly of the deployment device of  FIG. 11A  along plane  11 C- 11 C. 
         FIG. 11D  is a side view of another portion of the delivery catheter assembly of the deployment device of  FIG. 11A . 
         FIG. 12A  is a side view of yet another portion of the delivery catheter assembly of the deployment device of  FIG. 11A  with a prosthesis in a first state. 
         FIG. 12B  is a side view of the portion of the delivery catheter assembly of  FIG. 12A  in a second state. 
         FIG. 12C  is a side view of the portion of the delivery catheter assembly of  FIG. 12A  in a third state. 
         FIG. 13A  is a cross-sectional view of a portion of another embodiment of a delivery catheter assembly. 
         FIG. 13B  is a side view of the portion of the delivery catheter assembly of  FIG. 13A , wherein an outer sheath has been removed. 
         FIG. 14  is a perspective view of another embodiment of a deployment device. 
         FIG. 15  is a cross-sectional view of a portion of the deployment device of  FIG. 14 . 
         FIG. 16A  is a perspective view of a ratchet slide component of the deployment device of  FIGS. 14 and 15 . 
         FIG. 16B  is a cross-sectional view of the ratchet slide of  FIG. 16A . 
         FIG. 17  is a side view of a carrier component of the deployment device of  FIGS. 14 and 15 . 
         FIG. 18  is a cross-sectional view of another portion of the deployment device shown in  FIGS. 14 and 15 . 
         FIG. 18A  is a partial cut-away view of a portion of the deployment device shown in  FIG. 18 . 
         FIG. 19  is a cross-sectional view of yet another portion of the deployment device shown in  FIGS. 14 and 15 . 
     
    
    
     DETAILED DESCRIPTION 
     Deployment devices may be configured to deliver a medical appliance to a location within a patient&#39;s body and deploy the medical appliance within the patient&#39;s body. Though specific examples recited herein may refer to deployment of devices within the vasculature, analogous concepts and devices may be used in various other locations within the body, including for placement and deployment of medical appliances in the gastrointestinal tract (including, for example, within the esophagus, intestines, stomach, small bowel, colon, and biliary duct); the respiratory system (including, for example, within the trachea, bronchial tubes, lungs, nasal passages, and sinuses); or any other location within the body, both within bodily lumens (for example, the ureter, the urethra, and/or any of the lumens discussed above) and within other bodily structures. 
     Furthermore, though specific examples herein may refer to deployment of vascular prostheses such as stents, deployment of a wide variety of medical appliances are within the scope of this disclosure, including stents, stent-grafts, shunts, grafts, and so forth. Additionally, the deployment device disclosed herein may be configured to deliver and deploy self-expanding medical appliances, including stents configured to expand within a bodily lumen upon deployment. 
     As used herein, delivery of a medical appliance generally refers to placement of a medical appliance in the body, including displacement of the appliance along a bodily lumen to a treatment site. For example, delivery includes displacement of a crimped stent along a vascular lumen from an insertion site to a treatment location. Deployment of a medical appliance refers to placement of the medical appliance within the body such that the medical appliance interacts with the body at the point of treatment. For example, deployment includes releasing a crimped or otherwise constrained self-expanding stent from a deployment device such that the stent expands and contacts a lumen of the vasculature. 
     Deployment devices within the scope of this disclosure may be configured to incrementally deploy a medical appliance. Incremental deployment may facilitate desired placement of the medical appliance due to the degree of control afforded a practitioner during deployment. A practitioner may, for example, desire to deploy a portion of a stent, make adjustments to placement within the vasculature or confirm the location of the stent, prior to deploying the remaining portion of the stent. Such processes may be iterative, with a practitioner deploying a portion of a stent, confirming placement, deploying an additional portion, again confirming placement, and so forth until the stent is fully deployed. 
     Deployment devices within the scope of this disclosure may be configured to provide visual, audible, tactile, or other feedback relating to the degree to which a medical appliance has been deployed. Multiple types of feedback may enhance a practitioner&#39;s level of control over the procedure due to the multiple indications regarding location or degree of deployment of the medical appliance. 
     Moreover, deployment devices within the scope of this disclosure may provide a degree of mechanical advantage during deployment, for example, through the use of levers to decrease the force used to deploy a device. Mechanical advantage may thus increase a user&#39;s comfort and level of control during use. Still further, deployment devices within the scope of this disclosure may be ergonomically designed, presenting an actuation input disposed such that a practitioner can directly engage and utilize the device, without repositioning his or her hand or body. Deployment devices within the scope of this disclosure may also be configured for one-handed actuation and may be configured for ambidextrous use. 
     It will be readily understood that the components of the embodiments as generally described and illustrated in the figures herein could be arranged and designed in a wide variety of configurations. Thus, the following more detailed description of various embodiments, as represented in the figures, is not intended to limit the scope of the disclosure, but is merely representative of various embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated. 
     The phrases “connected to” and “coupled to” refer to any form of interaction between two or more entities, including mechanical, electrical, magnetic, electromagnetic, fluidic, and thermal interaction. Two components may be coupled to each other even though they are not in direct contact with each other. For example, two components may be coupled to each other through an intermediate component. 
     The directional terms “proximal” and “distal” are used herein to refer to opposite locations on a medical device. The proximal end of the device is defined as the end of the device closest to the practitioner when the device is in use by the practitioner. The distal end is the end opposite the proximal end, along the longitudinal direction of the device, or the end furthest from the practitioner. 
     Again, though the embodiments specifically described below may reference a stent deployment device specifically, the concepts, devices, and assemblies discussed below may be analogously applied to deployment of a wide variety of medical appliances in a wide variety of locations within the body. 
       FIG. 1  is a perspective view of a deployment device  100 . The deployment device  100  comprises a handle assembly  102  adjacent the proximal end of the deployment device  100 . An elongate delivery catheter assembly  104  extends distally from the handle assembly  102  to a distal tip or delivery tip  174 . The handle assembly  102  may provide a proximal user input, with one or more components configured to allow a practitioner to deploy or otherwise manipulate a stent disposed within the delivery catheter assembly  104 . 
     In use, the handle assembly  102  may be disposed outside of a patient&#39;s body, while the delivery catheter assembly  104  is advanced to a treatment location within the patient&#39;s body. For example, the delivery catheter assembly  104  may be advanced from an insertion site (such as, for example, a femoral or jugular insertion site) to a treatment location within the vasculature. As further detailed below, the delivery catheter assembly  104  may be configured to be advanced through bends, turns, or other structures within the anatomy of the vasculature. Again, as detailed below, a stent may be disposed within a portion of the delivery catheter assembly  104  such that a practitioner may deploy the stent from a distal end of the delivery catheter assembly  104  through manipulation of one or more components of the handle assembly  102 . 
       FIG. 2  is a cross-sectional view of a portion of the deployment device  100  of  FIG. 1 . Specifically,  FIG. 2  is a side view of a portion of the deployment device  100  of  FIG. 1 , taken through a cross-sectional plane extending vertically and intersecting a longitudinal axis of the deployment device  100 , when the deployment device  100  is positioned as shown in  FIG. 1 . The longitudinal axis of the deployment device  100  extends along the center of the delivery catheter assembly  104 , including along the center of components of the delivery catheter assembly  104  which overlap with the handle assembly  102 , such as the intermediate sheath  160 , as shown in  FIG. 2 . 
     As the handle assembly  102  is configured to be grasped or otherwise manipulated by a user and the delivery catheter assembly  104  is configured to extend to a treatment location within a patient&#39;s body, along the longitudinal axis, the delivery catheter assembly  104  extends in a distal direction away from the handle assembly  102 . The proximal direction is opposite, correlating to a direction defined along the longitudinal axis, extending from the distal tip  174  toward the handle assembly  102 . 
       FIG. 2  depicts various internal components of the handle assembly  102 , exposed by the cross-sectional view. A portion of the delivery catheter assembly  104  is also shown extending from the handle assembly  102 . The handle assembly  102  comprises a housing  110 . The housing  110  surrounds certain components of the handle assembly  102 , as shown, providing a grip surface for a practitioner. 
     The housing  110  is operably coupled to an actuator  120 . Manipulation of the actuator  120  with respect to the housing  110  may be configured to deploy the stent, as further detailed below. In the depicted embodiment, the actuator  120  is rotatably coupled to the housing  110  by a pin  112 . The pin  112  extends from the housing  110  and may be integrally formed with one or more other portions of the housing  110 . As shown, the pin  112  extends through a pin aperture  122  in the actuator  120 . 
     Other arrangements for operably coupling the actuator  120  and the housing  110  are within the scope of this disclosure. For example, the pin  112  may be integral with a portion of the actuator  120  and may be received in an opening, sleeve, or aperture formed in the housing  110 . Other types of designs of rotatable couplings, including a separate coupling component such as a hinge are within the scope of this disclosure. Still further, a compliant mechanism, such as a deformable flange, may be utilized to rotatably couple the actuator  120  and the housing  110 , including compliant couplings integrally formed with the actuator  120 , the housing  110 , or both. Moreover, it is within the scope of this disclosure to slidably couple an actuator (such as actuator  120 ) to a housing (such as housing  110 ). Configurations wherein the actuator  120  is manipulated through rotation, translation, or other displacement relative to the housing  110  are all within the scope of this disclosure. 
     The actuator  120  comprises an input portion  121  extending from the aperture  122 . In the depicted embodiment, the input portion  121  comprises a surface, at least partially exposed with respect to the housing  110 . In operation, a user may manipulate the actuator  120  by exerting a force on the input portion  121 , illustrated by the arrow labeled “input” in  FIG. 2 , displacing the input portion  121  generally toward the longitudinal axis of the deployment device ( 100  of  FIG. 1 ) and causing the actuator  120  to rotate about the pin  112  with respect to the housing  110 . Displacement of the actuator  120  due to a force such as illustrated by the arrow labeled “input” corresponds to “depression” of the actuator  120  or “depression of the actuator  120  with respect to the housing  110 .” 
     The actuator  120  may further comprise a transfer arm  123  extending from the pin aperture  122 . The transfer arm  123  may be rigidly coupled to the input portion  121 , including embodiments wherein both the transfer arm  123  and the input portion  121  are integrally formed with the rest of the actuator  120 . The transfer arm  123  extends to a ratchet slide engaging portion  124 . Depression of the input portion  121 , in the direction shown by the arrow labeled “input” displaces the transfer arm  123  as the actuator  120  is rotated about the pin  112 . 
     Depression of the input portion  121  thus causes displacement of the ratchet slide engaging portion  124  with respect to the housing  110 . This displacement of the ratchet slide engaging portion  124  can be understood as rotation about the pin  112  having a proximal translation component and a vertical translation component, as rotation of the input portion  121  in the direction indicated by the arrow labeled “input” will displace (with respect to the housing  110 ) the ratchet slide engaging portion  124  both proximally and vertically. 
     A spring  115  may be disposed between the actuator  120  and the housing  110 . The spring  115  may be configured to resist displacement of the actuator  120  in the direction indicated by the arrow labeled “input” and may be configured to return the actuator to the relative position shown in  FIG. 2  after it has been depressed by a user. When the handle assembly  102  is unconstrained, the spring  115  may thus maintain (or return to) the relative position of the actuator  120  with respect to the housing  110  as shown in  FIG. 2 . 
     In the illustrated embodiment, the spring  115  engages with a spring ledge  125  of the actuator  120  and spring protrusions  111  of the housing  110 . The spring protrusions  111  may provide a bearing surface for the spring  115  offset from movable internal components of the handle assembly  102  (such as a carrier  140  further detailed below). Though three spring protrusions  111  are shown in the depicted embodiment, more or fewer protrusions, or use of other features such as ridges, ledges, shoulders, and so forth are within the scope of this disclosure. 
     The depicted embodiment comprises a leaf spring  115 . Other biasing elements, such as coil springs, piston assemblies, compliant mechanisms, and so forth are likewise within the scope of this disclosure. In some instances, a compliant portion of one or both of the housing  110  and actuator  120  may provide a biasing force analogous to that provided by the spring  115 . Leaf springs, such as spring  115 , may be configured to provide a relatively constant biasing force notwithstanding compression of the spring  115  as the actuator  120  is rotated or depressed with respect to the housing  110 . 
     As the actuator  120  is depressed with respect to the housing  110 , the spring  115  compresses and the ratchet slide engaging portion  124  is displaced as described above. Again, the displacement of the ratchet slide engaging portion  124  with respect to the housing  110  can be understood as having a proximal component and a vertical component. 
     The ratchet slide engaging portion  124  may be operably coupled to a ratchet slide  130  such that displacement of the ratchet slide engaging portion  124  likewise displaces the ratchet slide  130 . The ratchet slide  130  may be constrained such that the ratchet slide  130  is configured only for proximal or distal displacement with respect to the housing  110 . Thus, operable coupling of the ratchet slide engaging portion  124  to the ratchet slide  130  may allow for sliding interaction between the ratchet slide engaging portion  124  and the ratchet slide  130  such that only the proximal or distal component of the displacement of the ratchet slide engaging portion  124  is transferred to the ratchet slide  130 . Stated another way, the ratchet slide  130  may be displaced in a direction parallel to the longitudinal axis of the deployment device  100  while the input displacement may be at an angle to the longitudinal axis of the deployment device  100 . It is noted that, in the configuration shown in  FIG. 2 , a safety member  180  may prevent proximal displacement of the ratchet slide  130 . The safety member  180 , including removal thereof, is discussed in more detail below. Discussion herein relating to displacement of the ratchet slide  130  and related components may thus be understood as disclosure relevant to a configuration of the handle assembly  102  in which the safety member  180  has been removed. 
     As the actuator  120  is depressed with respect to the housing  110 , the ratchet slide  130  may thus be proximally displaced with respect to the housing  110 . One or both of the ratchet slide  130  and actuator  120  may also interact with the housing  110  such that there is a positive stop to arrest the depression of the actuator  120  and/or proximal displacement of the ratchet slide  130 . This positive stop may be an engaging ledge, shoulder, lug, detent, or other feature coupled to the housing  110 , including features integrally formed on the housing  110 . 
     A full stroke of the actuator  120  may thus correspond to displacement from the unconstrained position shown in  FIG. 2 , to the positive stop caused by interaction with the housing  110  when the actuator  120  is depressed. Release of the actuator  120  following a full or a partial stroke may then result in a return of the actuator  120  to the unconstrained state, due to the biasing force provided by the spring  115 . The unconstrained state shown in  FIG. 2  refers to lack of constraint due to user input. In this state, the spring  115  may be partially compressed, and interaction between the actuator  120  and the housing  110  may prevent rotation of the actuator  120  about the pin  112  in the opposite direction to depression of the actuator  120 , or the return direction. In other words, interaction between the actuator  120  and the housing  110  (or features of the housing  110 ) may create a positive stop to the return motion of the actuator  120  as well. 
     Referring to both  FIGS. 1 and 2 , the actuator  120  and the housing  110  may be coupled such that pinching of external materials (such as a practitioner&#39;s hand or a surgical drape) is minimized when the actuator  120  is depressed or returned. For instance, the actuator  120  may comprise a shell configured to mate with, and slide into, the housing  110 . Though the components may slide and rotate with respect to each other, the interface of the components may be sufficiently close and/or smooth to minimize pinching or other engagement of external materials. This close and/or smooth interface may refer to interaction at the edges of the actuator  120  as it is displaced into the housing  110  and/or to interaction at the portion of the actuator  120  near the pin  112 , as the actuator  120  returns to the unconstrained position. 
     As also shown in  FIGS. 1 and 2 , the input portion  121  of the actuator  120  may also comprise ridges or other features to facilitate handling or gripping of the actuator  120  during use. 
     Referring again to  FIG. 2 , the ratchet slide  130  may thus be proximally displaced during depression of the actuator  120 . Again, such displacement may correspond to a configuration in which the safety member  180  shown in  FIG. 2  has been removed. Proximal displacement of the ratchet slide  130  may also proximally displace the carrier  140  due to interaction between one or more carrier engaging ratchet lugs  136  on the ratchet slide  130  and a ratchet slide engaging arm  146  coupled to the carrier  140 . 
       FIG. 3A  is a perspective view of the ratchet slide  130  of the deployment device  100  of  FIGS. 1 and 2 .  FIG. 3B  is a cross-sectional view of the ratchet slide  130  of  FIG. 3A , taken through a vertical plane disposed along a longitudinal centerline of the ratchet slide  130 . When the ratchet slide  130  is disposed within the handle assembly  102  of  FIG. 2 , this cross-sectional plane would intersect the longitudinal axis of the deployment device  100 . 
     As shown in  FIGS. 2, 3A, and 3B , the ratchet slide  130  may comprise a plurality of carrier engaging ratchet lugs  136 . The carrier engaging ratchet lugs  136  may be spaced at even intervals along the longitudinal direction of the ratchet slide  130 . In the figures, exemplary carrier engaging ratchet lugs are denoted with reference numeral  136 , while the distal most carrier engaging ratchet lug, disposed at the distal end of the ratchet slide  130  is denoted with reference numeral  136   a.    
     The ratchet slide  130  further comprises a ratchet slide safety opening  139  and an actuator engaging opening  134 . These features are discussed in more detail below. 
     As noted above, interaction between the ratchet slide engaging portion  124  of the actuator  120  and the ratchet slide  130  may proximally displace the ratchet slide  130  with respect to the housing  110 . Engagement between the carrier  140  and one of the carrier engaging ratchet lugs  136  may also proximally displace the carrier  140  as the ratchet slide  130  is proximally displaced with respect to the housing  110 . In the configuration of  FIG. 2 , the ratchet slide engaging arm  146  of the carrier  140  is engaged with the distal most carrier engaging ratchet lug  136   a.    
       FIG. 4  is a side view of the carrier  140  of the deployment device  100  of  FIGS. 1 and 2 . As shown in  FIG. 4 , the ratchet slide engaging arm  146  extends radially away from a longitudinal axis of the carrier  140 . When the carrier  140  is disposed within the handle assembly  102  of  FIG. 2 , the longitudinal axis of the carrier  140  is disposed along the longitudinal axis of the deployment device  100 . 
       FIG. 5  is a cross-sectional view of a portion of the deployment device  100  shown in  FIGS. 1 and 2 . Specifically, the actuator  120 , ratchet slide  130 , and carrier  140  are shown in  FIG. 5 , in the same relative positions, and along the same cross-sectional plane as in  FIG. 2 . 
     Referring to  FIGS. 2-5 , during depression of the actuator  120  with respect to the housing  110 , the actuator  120  rotates around the pin aperture  122 . This rotation causes displacement of the ratchet slide engaging portion  124  of the actuator  120 . The component of this displacement correlating to proximal displacement of the ratchet slide engaging portion  124  also proximally translates the ratchet slide  130  due to interaction between the ratchet slide engaging portion  124  of the actuator  120  and the actuator engaging opening  134  of the ratchet slide  130 . Stated another way, the walls or faces that define the actuator engaging opening  134  may contact the ratchet slide engaging portion  124  such that the ratchet slide  130  is displaced when the actuator  120  is displaced. 
     Proximal displacement of the ratchet slide  130  also proximally displaces the carrier  140  due to interaction between the carrier engaging ratchet lugs  136  and the ratchet slide engaging arm  146 . In the depicted embodiment, a distal surface of the ratchet slide engaging arm  146  is in contact with a proximal face of the distal most carrier engaging ratchet lug  136   a . This contact exerts proximal force on the distal surface of the ratchet slide engaging arm  146 , displacing the carrier  140  in a proximal direction. Accordingly, the ratchet slide  130  and carrier  140  will move proximally until the actuator  120  reaches the end of the stroke. 
       FIG. 6  is a cross-sectional view of the housing  110  and the carrier  140  in the same relative positions shown in  FIG. 2 . The cross-sectional plane of  FIG. 6  extends along the longitudinal axis of the deployment device; however, the cross-sectional plane of  FIG. 6  extends horizontally, orthogonal to the cross-sectional planes of  FIGS. 2, 3B , and  5 . 
     As shown in  FIG. 6 , the carrier  140  comprises a housing engaging arm  148  extending radially away from a longitudinal axis of the carrier  140 . The housing  110  comprises a plurality of carrier engaging housing lugs  118 . In  FIG. 6 , exemplary carrier engaging housing lugs are denoted by reference numeral  118 , with the distal most carrier engaging housing lug denoted by reference numeral  118   a.    
     Referring to  FIGS. 2-6 , as interaction between the actuator  120 , ratchet slide  130 , and carrier  140  displaces the carrier  140  with respect to the housing  110  (as shown and described above), the housing engaging arm  148  (shown in  FIG. 6 ) of the carrier  140  will deflect radially inward due to contact with one of the carrier engaging housing lugs  118 . For example, from the position shown in  FIG. 6 , as interaction between the distal most carrier engaging ratchet lug  136   a  and the ratchet slide engaging arm  146  of the carrier  140  draws the carrier  140  proximally, the distal most carrier engaging housing lug  118   a  causes the housing engaging arm  148  to displace radially inward. The housing engaging arm  148  will continue to deflect radially inward until the distal end of the housing engaging arm  148  is positioned proximal of the distal most carrier engaging housing lug  118   a , at which point the housing engaging arm  148  will return to the radially outward configuration shown in  FIG. 6 . The point at which the housing engaging arm  148  moves proximally of the distal most carrier engaging housing lug  118   a , may correspond to the stroke of the actuator  120 , such that engagement between the housing engaging arm  148  and the next carrier engaging housing lug  118  (moving in a proximal direction) occurs at the end of the stroke, which may correspond to contact between the ratchet slide  130  and/or actuator  120  and a positive stop on the housing  110  defining the end of the stroke. 
     As the actuator  120  is released following the stroke, interaction between the spring  115 , the housing  110 , and the actuator  120  will return the actuator  120  to the unconstrained position (the position shown in  FIG. 2 ) as discussed above. Corresponding rotation of the actuator  120  about the pin aperture  122  will thus correlate to displacement of the ratchet slide engaging portion  124 , including a component of displacement in the distal direction. Interaction between the ratchet slide engaging portion  124  and the actuator engaging opening  134  will then correlate to distal displacement of the ratchet slide  130 . Thus, when the actuator  120  is released at the end of a stroke, the actuator  120 , the spring  115 , and the ratchet slide  130  return to the same positions relative to the housing as shown in  FIG. 2 . 
     As the actuator  120  returns to the unconstrained position, however, interaction between the housing engaging arm  148  and the carrier engaging housing lug  118  prevents distal displacement of the carrier  140 . Specifically, the distal surface of the housing engaging arm  148  will be in contact with a proximal facing surface of a carrier engaging housing lug  118 , the interaction preventing the carrier  140  from returning to the pre-stroke position. In the exemplary stroke discussed above, the distal most carrier engaging housing lug  118   a  displaced the housing engaging arm  148  during the stroke, and the housing engaging arm  148  engaged with the distal most carrier engaging housing lug  118   a  following the stroke. Subsequent strokes move the carrier  140  along the plurality of carrier engaging housing lugs  118  in a proximal direction. 
     As the actuator  120  returns to the unconstrained state, radially inward displacement of the ratchet slide engaging arm  146  of the carrier  140  allows the ratchet slide  130  to move distally with respect to the carrier  140 , as engagement between the carrier  140  and the carrier engaging housing lugs  118  arrest distal displacement of the carrier  140 . 
     Referring to  FIGS. 2-6 , with particular reference to the view of  FIG. 5 , distal displacement of the ratchet slide  130  with respect to the carrier  140  creates interaction between the carrier engaging ratchet lugs  136  and the ratchet slide engaging arm  146  causing the ratchet slide engaging arm  146  to displace radially inward. The proximal facing surface of the carrier engaging ratchet lugs  136  may be angled to facilitate this interaction. In the exemplary stroke discussed above, engagement between the distal most carrier engaging ratchet lug  136   a  displaced the carrier  140  in a proximal direction; during the return of the actuator  120 , the next carrier engaging ratchet lug  136  (in a proximal direction) causes the radially inward displacement of the ratchet slide engaging arm  146  until the ratchet slide engaging arm  146  is proximal of the carrier engaging ratchet lug  136 . At that point the ratchet slide engaging arm  146  returns to a radially outward position (analogous to that shown in  FIG. 5 ) though the distal surface of the ratchet slide engaging arm  146  is now engaged with a proximal face of the next carrier engaging ratchet lug  136  (again in a proximal direction). Displacement of the ratchet slide  130  sufficient to move to engagement with a subsequent carrier engaging ratchet lug  136  may correspond with the magnitude of ratchet slide  130  displacement corresponding to a return of the actuator  120 . Subsequent returns of the actuator  120  following strokes move the ratchet slide  130  such that the plurality of carrier engaging ratchet lugs  136  may serially engage the carrier  140 , stroke after stroke. 
     Accordingly, as described above, depressing the actuator  120  for a full stroke, then allowing the actuator  120  to return to the unconstrained position, displaces the carrier  140  with respect to the housing  110  in discrete increments, corresponding to the distance between adjacent carrier engaging housing lugs  118  along the longitudinal direction. Interaction of the actuator  120  and positive stops associated with the housing  110 , carrier arms (e.g., ratchet slide engaging arm  146  and housing engaging arm  148 ), and lugs (e.g., carrier engaging housing lugs  118  and carrier engaging ratchet lugs  136 ) may also combine to give a user tactile and audible feedback as the carrier  140  is incrementally displaced. Further, one or more opening in the housing  110  may allow a user to observe the relative position of the carrier  140  providing further feedback as to carrier  140  position. 
     As detailed below, the relative position of the carrier  140  with respect to the housing  110  may correlate to the degree of deployment of a stent from the deployment device  100 . Thus, visual, audible, and tactile feedback as to the position of the carrier  140  provides a user with information regarding stent deployment during use of the deployment device  100 . This information may correlate to increased control during deployment as the practitioner quickly and intuitively can surmise the degree of stent deployment. 
     As outlined above, tactile and/or audible feedback result from the interactions of the carrier  140 , ratchet slide  130 , housing  110 , and/or actuator  120 . For example, as the ratchet slide engaging arm  146  or housing engaging arm  148  of the carrier  140  deflects radially inward then return outward, there may be an audible and/or tactile response. 
     The device may be configured for visual feedback of, or relating to, the relative deployment of a stent. For example, in some embodiments, the housing  110  may comprise viewing windows to allow a practitioner to observe the position of the carrier  140  relative to the housing  110 . Further, indicia on the housing  110  may correlate the position of the carrier  140  to the degree of deployment of a stent. 
     The increments of displacement of the carrier  140  may correlate to standard stent lengths or units of measure. For example, many stents are sized in 1 cm increments. Configuration of the increments of displacement on the carrier  140  in 1 cm increments would thus directly correlate with stent length at a 1:1 ratio. Any other ratio, including embodiment wherein a stroke correlates to a greater length (such as 2, 3, 4, or 5 cm) or a lesser length (such as 0.01, 0.1, 0.25, 0.5, or 0.75 cm) are likewise within the scope of this disclosure. 
     In some embodiments, interaction between the carrier  140 , the ratchet slide  130 , the housing  110 , and/or the actuator  120  may comprise additional carrier engaging ratchet lugs  136  and/or carrier engaging housing lugs  118 . For example, the carrier engaging ratchet lugs  136  may be spaced to enable semi-continuous ratcheting of the ratchet slide  130  with respect to the actuator  120  and/or the housing  110 . Such an embodiment is described in further detail below in reference to the deployment device  400  depicted in  FIGS. 14-19 . 
     The deployment device  100  may be configured as a universal device operable with various stent lengths. In some embodiments a practitioner may directly equate the number of strokes needed to deploy a stent with the length of the stent loaded in the deployment device  100  (such as four strokes for a four centimeter stent). Further, a single design of deployment device  100  may be utilized with various lengths of stents, with a maximum length related to the maximum length of travel of the carrier  140 . 
     The nature of depression of the actuator  120  may facilitate one-handed operation and may be ergonomically designed. First, a practitioner need only grip the deployment device with one hand to depress the actuator, leaving a second hand free for other therapy needs. Further, the direction with which the deployment device is gripped, with the practitioner&#39;s hand extending laterally away from the longitudinal axis of the deployment device and the lateral direction of depression, as opposed, for example, to longitudinal gripping to actuate, may be ergonomically desirable. Lateral gripping and input may more readily present the deployment device  100  for use when the delivery catheter assembly  104  is disposed within a patient&#39;s body, not requiring the practitioner to move to an awkward stance with respect to other therapy tools. Further, the input portion  121  of the actuator  120  may provide additional surface for a practitioner to grip, facilitating use of a greater portion of a practitioner&#39;s hand for actuation, as compared to a finger trigger or similar actuation mechanism. 
     The incremental displacement of the carrier  140  may further facilitate partial deployment of a stent, allowing a practitioner to deploy the stent in increments, potentially adjusting or confirming the position of the stent between these increments. 
     Still further, the deployment device  100  may be configured for use with either the right or left hand, or gripped with the fingers or palm in contact with the actuator  120  without changing the design of the deployment device  100 . These features may further increase user comfort and control. Viewing windows in the housing  110  to confirm the position on the carrier  140  may be located on one or both sides of the housing  110  and may be associated with indicia correlating to stent length or other factors. 
     Moreover, the relative lengths of the input portion  121  and transfer arm  123  of the actuator  120  may be configured to provide mechanical advantage when deploying a stent. This may increase comfort and control during use. The ratio of the length of the input portion  121 —from its distal end to the pin aperture  122 —to the length of the transfer arm  123 —from the pin aperture  122  to the ratchet slide engaging portion  124 —may be greater than or equal to 1.5:1, including 2:1, 2.5:1, 3:1, 3.5:1 or greater. This ratio correlates to the mechanical advantage provided by the device. In some instances the mechanical advantage provided may be 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or greater. Stated another way, the ratio of length of travel of the input portion  121  to the corresponding length of travel of the ratchet slide engaging portion  124  may be 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or greater. Accordingly, the input force applied against the input portion  121  may result in a greater force exerted by the ratchet slide engaging portion  124  on the ratchet slide  130 . The ratio of the force exerted on the ratchet slide  130  to the input force may be 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or greater. 
       FIG. 7  is a front view of the deployment device  100 , illustrating two cross-sectional planes. Specifically, plane A-A extends vertically along the longitudinal axis of the deployment device  100  viewing the exposed components in a right to left direction. Plane A-A corresponds to the cross-sectional plane of  FIGS. 2, 3B, and 5 . Plane B-B also extends from the longitudinal axis of the deployment device  100 , though Plane B-B extends horizontally therefrom. Plane B-B corresponds to the cross-sectional plane of  FIG. 6 , and is viewed from a top to bottom direction. The longitudinal axis of the deployment device  100  is in both planes A-A and B-B, with the line defined as the intersection between these planes being the same line as the longitudinal axis as referenced herein. 
     Additionally, as stated above, the deployment device  100  may comprise a safety member  180 .  FIG. 8  is a perspective view of the safety member  180  of the deployment device  100 . The safety member  180  may be configured with a circular or partially circular opening configured to snap onto an outside surface of a portion of the deployment device  100 . Referring to both  FIG. 2  and  FIG. 8 , the safety member  180  may comprise a safety lug  189  that extends through a ratchet slide safety opening ( 139  of  FIG. 3A ) and a similar safety opening in the housing  110  (not shown). When the safety lug  189  is disposed within these openings, the safety lug  189  may prevent proximal displacement of the carrier  140  and the ratchet slide  130 , thus preventing inadvertent deployment of a stent. A practitioner may leave the safety member  180  in place during displacement of the delivery catheter assembly  104  to a treatment region. Due to interactions between the carrier  140 , ratchet slide  130 , and actuator  120 , the safety member  180  likewise prevents displacement of the actuator  120  when the safety lug  189  extends through the openings. 
     In the depicted embodiment, the safety lug  189  extends through a bottom portion of the housing  110  and ratchet slide  130 . In other embodiments, the safety lug  189  may extend through a top surface of the housing  110 , interacting with the carrier  140  but not directly with the ratchet slide  130 . Nevertheless, prevention of proximal displacement on the carrier  140  only, will also prevent displacement of the ratchet slide  130  and the actuator  120  due to the interaction between these elements. 
     In some embodiments, the safety member  180  may be tethered to the deployment device  100 , or may comprise a sliding switch or other element operably coupled to the housing  110  or other components of the deployment device  100 . In the depicted embodiment, the safety member  180  is removably coupled. 
       FIG. 9  is a side view of a portion of the delivery catheter assembly  104  of the deployment device  100 . Specifically,  FIG. 9  is a side view of a distal section of the delivery catheter assembly  104 .  FIG. 10  is a side view of the same longitudinal section of the delivery catheter assembly  104  as shown in  FIG. 9 ; however, the outer sheath ( 150  of  FIG. 9 ) has been removed to show other components. 
     Referring to  FIGS. 1, 2, 9, and 10 , the delivery catheter assembly  104  may be configured to deploy a stent as the deployment device  100  is manipulated, as discussed above. The delivery catheter assembly  104  may comprise an outer sheath  150 , extending from the handle assembly  102 . The outer sheath  150  may be fixedly coupled to the carrier  140 . The delivery catheter assembly  104  may further comprise an intermediate sheath  160  and an inner sheath  170 , both disposed within the outer sheath  150 , and both fixedly coupled to the housing  110 . Thus, proximal displacement of the carrier  140  with respect to the housing  110  will proximally displace the outer sheath  150  with respect to both the intermediate sheath  160  and the inner sheath  170 . 
     The outer sheath  150  may comprise a shaft section  156  extending from the carrier  140  in a distal direction. At the distal end of the shaft section  156  the outer sheath  150  may comprise a flex zone  154  extending from the shaft section  156  in a distal direction. Finally, the outer sheath  150  may comprise a pod  152  extending from the flex zone  154  in a distal direction. (As shown in  FIG. 9 , the pod  152  may be transparent.) 
     The shaft section  156  of the outer sheath  150  may have a different stiffness and/or durometer than the flex zone  154  and/or the pod  152 . The flexibility toward the distal end of the outer sheath  150  may improve trackability of the delivery catheter assembly  104  over a guidewire and may be less traumatic, while a stiffer shaft may be more kink resistant and/or transmit displacement and/or torque along the shaft section  156 . 
     The pod  152  may be configured to retain a crimped or otherwise constrained stent. Removal of the pod  152  from the stent may allow the stent to self-expand, and thereby deploy. It is within the scope of this disclosure for the pod  152  to be any relative length, the flex zone  154  to be any relative length, and the shaft section  156  to be any relative length. Thus, in some instances, a constrained stent may be in one, two, or all three of these portions of the outer sheath  150 . For example, in the illustrated embodiment, an annular space  176  (described further below) is configured to receive a crimped stent extending along the pod  152  as well as portions of the flex zone  154  and shaft section  156 . In other embodiments, the annular space  176  may correlate just to the pod  152  segment, meaning the device is configured to retain a crimped stent only within the pod  152  segment. 
     The distal tip  174  of the delivery catheter assembly  104  may be coupled to and/or integrally formed with the inner sheath  170 . A lumen  172  may extend along the inner sheath  170  from the proximal end of the deployment device  100  to the distal tip  174 . A luer fitting  113  coupled to the housing  110  may be in communication with the lumen  172 . A guidewire may thus extend through the luer fitting  113 , through the lumen  172 , and out of the distal tip  174 . Further, fluid introduced into the luer fitting  113  may be utilized to flush the lumen  172 . 
     The inner sheath  170  may be fixed to the housing, for example, at the proximal end of the inner sheath  170 . An intermediate sheath  160 , also fixed to the housing  110 , may extend over a portion of the inner sheath  170 . The intermediate sheath  160  and inner sheath  170  may or may not be directly fixed to each other. In some embodiments, the intermediate sheath  160  may be a close slip fit over the inner sheath  170 . 
     The inner sheath  170  extends distally beyond a distal end of the intermediate sheath  160 , creating an annular space  176  between the inner sheath  170  and the outer sheath  150  adjacent the distal tip  174 , extending proximally to the distal end of the intermediate sheath  160 . This annular space  176  may be configured to retain a crimped stent. 
     As the deployment device  100  is manipulated to incrementally displace the carrier  140  with respect to the housing  110 , the outer sheath  150  is incrementally displaced proximally with respect to the inner sheath  170  and intermediate sheath  160 . The distal end of the intermediate sheath  160  interacts with the proximal end of the stent, preventing the stent from being drawn back with the outer sheath  150 . Thus, the stent is incrementally exposed, and allowed to self-expand and deploy. 
     In some embodiments, a fluid aperture  162  in the intermediate sheath  160  may extend through the wall of the intermediate sheath  160  and the wall of the inner sheath  170 , into fluid communication with the inner lumen  172 . This fluid aperture  162  may thus provide fluid communication between the annular space  176  and the inner lumen  172 , as fluid within the inner lumen  172  can move through the fluid aperture  162  and into the annular space  176 . This communication may be used to flush the annular space  176  during use, which may be configured to remove air or other unwanted materials in the annular space  176  or around the crimped stent. 
     The distal tip  174  may comprise a flexible material and may be configured to be atraumatic. The distal tip  174  may comprise nylons, including PEBAX® polyether block amides. 
     In some instances braided or coil reinforcements may be added to the outer sheath  150 , the intermediate sheath  160 , and/or the inner sheath  170  to increase kink resistance and/or elongation. Reinforcing members may comprise stainless steel, nitinol, or other materials and may be round, flat, rectangular in cross section, and so forth. 
     One, two, or all of the outer sheath  150 , the intermediate sheath  160 , and/or the inner sheath  170  may be configured with varying durometers or other properties along the length thereof. In some instances the outer sheath  150  may be configured with a proximal section with a durometer between 72 and 100 on the Shore D scale or may be greater than 100 on the Shore D scale. A second portion of the outer sheath  150  may comprise a durometer of 63 on the Shore D scale, and a distal section with a durometer between 40 and 55 on the Shore D scale. Any of these values, or the limits of any of the ranges, may vary by 15 units in either direction. In some instances the second portion will begin about six inches from the distal end of the outer sheath  150 , and the distal section will begin about three inches from the distal end of the outer sheath  150 . These sections may or may not correspond to the shaft section  156 , the flex zone  154 , and the pod  152  as described above. The intermediate sheath  160  may be configured with varying durometer zones within the same ranges of hardness and length. 
     Any of the inner sheath  170 , intermediate sheath  160 , and outer sheath  150  may have differing durometer or flex zones along their lengths, and these zones may overlap in various ways to create various stress/strain profiles for the overall delivery catheter assembly  104 . Overlapping of such zones may reduce tendency to kink, including tendency to kink at transition zones. Further, the housing  110  may be coupled to a strain relief member  116  (as shown in  FIG. 2 ). 
     Any of the outer sheath  150 , the intermediate sheath  160 , and the inner sheath  170  may be comprised of nylons, including PEBAX® polyether block amides. Further, during manufacture, any of these members may be configured with a low friction outer surface, including through “frosting” the materials, by blowing air across the material during extrusion, or by using additives during extrusion to reduce friction. 
     In some instances, during manufacture the distal tip  174  may be pulled into interference with the outer sheath  150 , prestressing the inner sheath  170  in tension. This may reduce any effects of material creep or elongation during sterilization, keeping the distal tip  174  snugly nested with the outer sheath  150 . Further, during manufacture, the interface zone between the outer sheath  150  and the carrier  140  may be configured with a tolerance zone, meaning the outer sheath  150  can be coupled to the carrier  140  at multiple points along an inside diameter of the carrier  140 . This tolerance may enable manufacturing discrepancies or variations to be taken up during assembly to ensure a snug nest between the distal tip  174  and the outer sheath  150 . The same tolerance fit may be applied to the inner sheath  170  and/or the intermediate sheath  160  wherein these members couple to the housing  110 , including a fit zone along an inside diameter of the luer fitting  113 . 
     In some instances, the outer sheath  150  may include indicia correlating to the degree to which a stent has been deployed. These indicia may correspond to the position of the outer sheath  150  with respect to the housing  110 . For example, as the outer sheath  150  is drawn into the housing  110 , different indicia are exposed and/or covered. 
     Further, in some instances, the deployment device  100  may be configured such that the outer sheath  150  may be distally displaced after the stent is deployed to nest the distal tip  174  in the outer sheath  150  during withdrawal of the deployment device  100  from a patient. Such configurations may include features of the handle assembly  102  that disengage the carrier  140  from one or more elements after stent deployment. 
       FIGS. 11A-11D  depict an embodiment of a deployment device  200  that resembles the deployment device  100  described above in certain respects. Accordingly, like features are designated with like reference numerals, with the leading digits incremented to “2.” For example, the embodiment depicted in  FIGS. 11A-11D  includes a distal tip  274  that may, in some respects, resemble the distal tip  174  of FIGS.  1 ,  9 , and  10 . Relevant disclosure set forth above regarding similarly identified features thus may not be repeated hereafter. Moreover, specific features of the deployment device  200  and related components shown in  FIGS. 1-10  may not be shown or identified by a reference numeral in the drawings or specifically discussed in the written description that follows. However, such features may clearly be the same, or substantially the same, as features depicted in other embodiments and/or described with respect to such embodiments. Accordingly, the relevant descriptions of such features apply equally to the features of the deployment device  200  and related components depicted in  FIGS. 11A-11D . Any suitable combination of the features, and variations of the same, described with respect to the deployment device  100  and related components illustrated in  FIGS. 1-10 , can be employed with the deployment device  200  and related components of  FIGS. 11A-11D , and vice versa. This pattern of disclosure applies equally to further embodiments depicted in subsequent figures and described hereafter, wherein the leading digits may be further incremented. 
       FIG. 11A  is a perspective view of the deployment device  200 . The deployment device  200  comprises a handle assembly  202  adjacent the proximal end of the deployment device  200 . An elongate delivery catheter assembly  204  extends distally from the handle assembly  202  to the distal tip  274 . The handle assembly  202  may provide a proximal user input, with one or more components configured to allow a practitioner to deploy or otherwise manipulate a prosthesis disposed within the delivery catheter assembly  204 . As discussed above, though specific examples herein may refer to prostheses such as stents, other prostheses are also within the scope of this disclosure, including, but not limited to, vascular prostheses, stents, stent-grafts, shunts, grafts, and so forth. 
       FIG. 11B  is a cross-sectional view of a portion of the delivery catheter assembly  204  of the deployment device  200  of  FIG. 11A  along plane  11 B- 11 B. Specifically,  FIG. 11B  is a cross-sectional view of a distal portion of the delivery catheter assembly  204 .  FIG. 11C  is a cross-sectional view of a portion of the delivery catheter assembly  204  of the deployment device  200  of  FIG. 11A  along plane  11 C- 11 C.  FIG. 11D  is a side view of the same longitudinal section of the delivery catheter assembly  204  as shown in  FIG. 11B ; however, the outer sheath ( 250  of  FIG. 11B ) has been removed to show other components. 
     Referring to  FIGS. 11B-11D , the delivery catheter assembly  204  may comprise an outer sheath  250 . The delivery catheter assembly  204  may further comprise an intermediate sheath  260  and an inner sheath  270 , each of which can be disposed within the outer sheath  250 . Additionally, the inner sheath  270  can be disposed within the intermediate sheath  260 . In certain embodiments, the delivery catheter assembly  204  may lack the intermediate sheath  260 . In some embodiments, the outer sheath  250  may be displaced with respect to each of the intermediate sheath  260  and the inner sheath  270 . 
     An annular space  276  may be disposed between each of the outer sheath  250  and the inner sheath  270 . In certain embodiments, the annular space  276 , or a portion of the annular space  276 , may be configured to receive and/or retain a crimped or otherwise constrained stent. Removal or displacement of the outer sheath  250  from around the constrained stent may allow the stent to self-expand, and thereby deploy. It is within the scope of this disclosure for the annular space  276  to be any relative length. Thus, in some instances, a constrained stent may be disposed along only a portion of a length of the annular space  276 . In some other instances, a constrained stent may be disposed along substantially the entire length of the annular space  276 . 
     In various embodiments, the intermediate sheath  260  may be directly coupled to the inner sheath  270 . In various other embodiments, the intermediate sheath  260  may not be directly coupled to the inner sheath  270 . For example, the intermediate sheath  260  may be a close slip fit over the inner sheath  270 . 
     As depicted, the inner sheath  270  can extend distally beyond a distal end of the intermediate sheath  260 , creating or forming the annular space  276  between the inner sheath  270  and the outer sheath  250  adjacent the distal tip  274 . Furthermore, the annular space  276  may extend proximally from adjacent the distal tip  274  to adjacent the distal end of the intermediate sheath  260 . The annular space  276  may be configured to retain a crimped or constrained stent. 
     A pliant member  290  may partially surround or be disposed around the inner sheath  270 . As shown, the pliant member  290  may be disposed around a circumference of the inner sheath  270 . For example, the pliant member  290  may be coupled to a portion of an exterior surface of the inner sheath  270 . The pliant member  290  may also be disposed within a portion of the annular space  276 . In some embodiments, the pliant member  290  may be configured to engage and/or retain a stent or a constrained stent. Stated another way, the pliant member  290  may at least partially grip, anchor, hold, and/or grasp the stent or the constrained stent. In certain embodiments, the stent may be disposed around the pliant member  290  and then the stent may be constrained, crimped, and/or loaded around the pliant member  290 . Further, a portion of the loaded stent (e.g., an inner surface of the loaded stent) may imprint within a portion of the pliant member  290  (e.g., an outer surface of the pliant member  290 ) as discussed in further detail below. 
     In some embodiments, the pliant member  290  may comprise two or more layers. In certain embodiments, the pliant member  290  may comprise two or more materials. Each of the materials may have different or various properties, for example, variations in thickness, durometer, elasticity, etc. In certain embodiments, the pliant member  290  may comprise an inner layer, wherein the inner layer is configured to adhere to or couple with the inner sheath  270  (e.g., the inner layer may be designed for optimal adhesion to the inner sheath  270 ). Furthermore, the pliant member  290  may comprise an outer layer, wherein the outer layer is configured to comply or imprint with the stent or the constrained stent. For example, the inner layer of a pliant member may comprise a grafted polyolefin (e.g., OREVAC®), and an outer layer of the pliant member may comprise a thermoplastic elastomer (e.g., CHRONOPRENE™). A portion of the inner sheath  270  may be formed from a polyether block amide (e.g., PEBAX®), and the OREVAC® inner layer can couple with or form a bond with (e.g., a strong bond with) the PEBAX® inner sheath. Stated another way, the OREVAC® may be used as a tie layer between each of the PEBAX® and the CHRONOPRENE™. 
     In some embodiments, the pliant member  290  may be configured to limit or prevent longitudinal displacement of the constrained stent. For example, the pliant member  290  may grip the constrained stent such that longitudinal displacement of the constrained stent is limited or prevented. In certain embodiments, the pliant member  290  may be configured to limit or prevent the constrained stent from collapsing or accordioning (e.g., longitudinally folding on itself). For example, the pliant member  290  may provide axial support to the constrained stent. Further, the pliant member  290  may be configured to partially surround one or more portions of the constrained stent, meaning that the pliant member  290  may conform to at least a portion of the constrained stent. For example, the pliant member  290  may conform to portions of the inner surface, shape, edges, and/or texture of the constrained stent. 
     The constrained stent (e.g., the inner surface of the constrained stent) may at least partially imprint around the pliant member  290 . In some embodiments, imprinting of a helical stent (e.g., a stent having a helical stent geometry) around the pliant member  290  may support rows of coils of the helical stent. Imprinting of the helical stent around the pliant member  290  may support each row of coils of the helical stent. In some other embodiments, imprinting of a non-helical stent (e.g., a stent having a non-helical stent geometry) around the pliant member  290  may support rows of coils of the non-helical stent. Imprinting of the non-helical stent around the pliant member  290  may support each row of coils of the non-helical stent. 
     In certain embodiments, the presence of the pliant member  290  may increase the force needed to proximally displace or pull back on the outer sheath  250 . For example, disposition of the pliant member  290  and/or a constrained stent within the annular space  276  may cause or form a tighter fit between each of the inner sheath  270  and the outer sheath  250 . However, due at least in part to the mechanical advantage that can be provided by the deployment device, as discussed above, the stent can still be readily deployable by a user. 
     In various embodiments, the delivery catheter assembly  204  may be coupled to a deployment device including an actuator, wherein the actuator is analogous to the actuator  120 . The actuator  120  can provide a mechanical advantage to the deployment device. Furthermore, such a mechanical advantage can assist a practitioner in using the deployment device to deploy a stent that is disposed around the pliant member  290 . 
     The pliant member  290  can be formed from one or more materials that are flexible, malleable, moldable, pliable, and/or supple. For example, the pliant member  290  may comprise one or more silicones, polyether block amides (e.g., PEBAX®), thermoplastic elastomers (e.g., CHRONOPRENE™), and/or other suitable materials. As discussed above, the pliant member  290  may be formed from multiple materials (e.g., the pliant member  290  may include two or more layers). The pliant member  290  may be applied to or disposed on the inner sheath  270  using dip, spray, and/or reflow techniques. Other suitable methods of applying or disposing the pliant member  290  onto a surface (e.g., a surface of the inner sheath  270 ) are also within the scope of this disclosure. 
     As illustrated, the pliant member  290  can extend longitudinally along a portion of the inner sheath  270  and/or through a portion of the annular space  276 . The pliant member  290  may have varying lengths. In some embodiments, the pliant member  290  may extend from adjacent a proximal end of the distal tip  274  to a position adjacent the distal end of the intermediate sheath  260 . In some other embodiments, the pliant member  290  may extend along only a portion of a longitudinal distance between each of the proximal end of the distal tip  274  and the distal end of the intermediate sheath  260 . As depicted, the distal end of the intermediate sheath can be disposed proximally of the pliant member  290 . 
     The delivery catheter assembly  204  may be configured to receive and/or retain stents having varying lengths. In various embodiments, the pliant member  290  may have a length that is greater than a length of the stent. In various other embodiments, the pliant member  290  may have a length that is substantially equal to the length of the stent. In various other embodiments, the pliant member  290  may have a length that is less than the length of the stent. 
     In some embodiments, the pliant member  290  can be longitudinally continuous along the length of the stent. For example, the pliant member  290  may extend longitudinally along the entire length of a constrained stent. In certain embodiments, the pliant member  290  can be circumferentially continuous along an inside surface of the stent. For example, the pliant member  290  may extend along the entire inner circumference of a constrained stent. 
     The pliant member  290  may have varying durometers. In some embodiments, the durometer of the pliant member  290  may be about 10 to about 60 on the Shore A scale, about 15 to about 45 on the Shore A scale, about 20 to about 30 on the Shore A scale, about 23 to about 27 on the Shore A scale, or another suitable durometer. In some other embodiments, the durometer of the pliant member  290  may be about 25 on the Shore A scale. 
     The pliant member  290  may also a range of wall thicknesses (e.g., the distance from an interior surface of the pliant member  290  to an exterior surface of the pliant member  290 ). In certain embodiments, the wall thickness of the pliant member  290  may be from about 0.0005 inch to about 0.050 inch, including from about 0.001 inch to about 0.050 inch, or another suitable thickness. 
     In some embodiments, a compound or drug may be loaded in the pliant member  290  and/or on an outer surface of the pliant member  290 . For example, an anticoagulant drug may be loaded in and/or coated on the pliant member  290 . 
     Analogous to the discussion above regarding the distal tip  174 , the distal tip  274  of the delivery sheath assembly  204  may be coupled to and/or integrally formed with the inner sheath  270 . Furthermore, a lumen  272  may extend along the inner sheath  270  from the proximal end of the deployment device  200  to the distal tip  274 . 
     In certain embodiments, the outer sheath  250  may be displaced or incrementally displaced proximally with respect to each of the inner sheath  270  and the intermediate sheath  260 . The distal end of the intermediate sheath  260  can engage or interact with the proximal end of the stent, limiting or preventing the stent from being drawn back with the outer sheath  250 . Thus, the stent can be incrementally exposed and allowed to self-expand and deploy. 
     As discussed above regarding the delivery catheter assembly  104 , the outer sheath  250 , the intermediate sheath  260 , and/or the inner sheath  270  may be configured with varying durometers or other properties along the length thereof. 
       FIG. 13A  is a cross-sectional view of a portion of another embodiment of a delivery catheter assembly  304 .  FIG. 13B  is a side view of the portion of the delivery catheter assembly  304 , wherein an outer sheath ( 350  of  FIG. 13A ) has been removed to show other components. As illustrated, a pliant member  390  may include a plurality of annular rings  392 . Each of the annular rings  392  can be a discrete or separate annular ring. In some embodiments, the annular rings  392  may be substantially evenly spaced along a portion of a length of an inner sheath  370 . In some other embodiments, the annular rings  392  may be spaced in an uneven pattern along a portion of the length of the inner sheath  370 . Stated another way, the annular rings  392  may be disposed in an intermittent manner along a portion of the length of the inner sheath  370 . 
     An annular ring  392  can partially surround or be disposed around the inner sheath  370 . As shown, each of the annular rings  392  of the pliant member  390  can be disposed around a circumference of the inner sheath  370 . For example, each of the annular rings  392  of the pliant member  390  may be coupled to a portion of an exterior surface of the inner sheath  370 . In some embodiments, a subset of the annular rings  392  may fully surround the inner sheath  370 , and another subset of the annular rings  392  may only partially surround the inner sheath  370 . 
     Each of the annular rings  392  of the pliant member  390  may also be disposed within a portion of an annular space  376 . In some embodiments, one or more of the annular rings  392  of the pliant member  390  may be configured to engage and/or retain a stent or a constrained stent. Stated another way, one or more of the annular rings  392  of the pliant member  390  may at least partially grip, anchor, hold, and/or grasp the stent or the constrained stent. 
     In certain embodiments, the stent may be disposed around a first annular ring  392  disposed to align with a distal end portion of the stent, a second annular ring  392  disposed to align with a middle portion of the stent, and/or a third annular ring  392  disposed to align with a proximal end portion of the stent. In certain other embodiments, a plurality of annular rings  392  may be disposed to align with only one of the distal end portion, the middle portion, or the proximal end portion of the stent. Other configurations (i.e., dispositions) of the one or more annular rings  392  in relation to a stent are also within the scope of this disclosure. 
     The stent may be constrained, crimped, and/or loaded around the one or more annular rings  392  of the pliant member  390 . Further, a portion of the loaded stent (e.g., an inner surface of the loaded stent) may imprint within a portion of the one or more annular rings  392  of the pliant member  390  (e.g., an outer surface of the one or more annular rings  392  of the pliant member  390 ). 
     The constrained stent (e.g., the inner surface of the constrained stent) may at least partially imprint around the one or more annular rings  392  of the pliant member  390 . In some embodiments, imprinting of a helical stent (e.g., a stent having a helical stent geometry) around the one or more annular rings  392  of the pliant member  390  may support rows of coils of the helical stent. Imprinting of the helical stent around the one or more annular rings  392  of the pliant member  390  may support each row of coils of the helical stent. In some other embodiments, imprinting of a non-helical stent (e.g., a stent having a non-helical stent geometry) around the one or more annular rings  392  of the pliant member  390  may support rows of coils of the non-helical stent. Imprinting of the non-helical stent around the one or more annular rings  392  of the pliant member  390  may support each row of coils of the non-helical stent. 
     As illustrated, the plurality of annular rings  392  of the pliant member  390  can extend longitudinally along a portion of the inner sheath  370  and/or through a portion of the annular space  376  (i.e., from the proximal-most annular ring  392  to the distal-most annular ring  392 ). In some embodiments, the plurality of annular rings  392  of the pliant member  390  may extend from adjacent a proximal end of a distal tip  374  to a position adjacent the distal end of an intermediate sheath  360 . In some other embodiments, the plurality of annular rings  392  of the pliant member  390  may extend along only a portion of a longitudinal distance between each of the proximal end of the distal tip  374  and the distal end of the intermediate sheath  360 . As depicted, the distal end of the intermediate sheath  360  can be disposed proximally of the plurality of annular rings  392  of the pliant member  390 . 
     The delivery catheter assembly  304  may be configured to receive and/or retain stents having varying lengths. In various embodiments, the plurality of annular rings  392  of the pliant member  390  may have a length that is greater than a length of the stent (i.e., the length from the proximal-most annular ring  392  to the distal-most annular ring  392 ). In various other embodiments, the plurality of annular rings  392  of the pliant member  390  may have a length that is substantially equal to the length of the stent. In various other embodiments, the plurality of annular rings  392  of the pliant member  390  may have a length that is less than the length of the stent. 
       FIG. 12A  is a side view of the distal portion of the delivery catheter assembly  204  of the deployment device  200  of  FIG. 11A  in a first state.  FIGS. 12B and 12C  are side views of the distal portion of the delivery catheter assembly  204  in a second state and a third state, respectively. 
     With reference to  FIG. 12A , a stent  35  may be constrained, crimped, or disposed around the pliant member  290  and/or within the annular space  276 . In the first state, as illustrated, the outer sheath  250  may be disposed over the stent  35  such that the stent  35  is in a constrained configuration. The constrained stent  35  can extend from the proximal end of the distal tip  274  along only a portion of the pliant member  290 , such that a gap or space is present along the pliant member  290  (e.g., between a proximal end of the constrained stent  35  and the distal end of the intermediate sheath  260 ). In some embodiments, the constrained stent  35  may extend along substantially an entire length of the pliant member  290 . In some other embodiments, the constrained stent  35  may be longer than the pliant member  290 . For example, in some instances, only a portion of the constrained stent  35  is disposed in the pliant member  290 . 
       FIG. 12B  depicts the distal portion of the delivery catheter assembly  204  in the second state. As illustrated, the distal portion of the delivery catheter assembly  204  can be disposed within a vessel  45  (e.g., a vessel of a patient). To deploy the stent  35 , the outer sheath  250  may be displaced proximally in relationship to the intermediate sheath  260 , the inner sheath  270 , and/or the pliant member  290 . For clarity, the pattern depicted on the pliant member  290  in  FIGS. 12B and 12C  differs in certain respects, for example, from the pattern depicted on the pliant member  290  in  FIG. 11D . The disclosure herein directed to the pliant member  290  of  FIGS. 12B and 12C , however, is relevant to the pliant member  290  of  FIG. 11D , and vice versa. In some embodiments, the outer sheath  250 , the intermediate sheath  260 , and/or the inner sheath  270  may be operably coupled to an actuator, as discussed above in reference to deployment device  100 . In some other embodiments, the outer sheath  250 , the intermediate sheath  260 , and/or the inner sheath  270  may be operably coupled to a housing, as discussed above in reference to deployment device  100 , and the housing may be operably coupled to the actuator. 
     Furthermore, displacement of the actuator may be configured to displace the outer sheath  250  relative to the inner sheath  270  and/or the intermediate sheath  260 . As noted above, some embodiments of the delivery catheter assembly  204  may lack an intermediate sheath  260 . Proximal displacement of the outer sheath  250  may expose a portion of the constrained stent  35 , and as such the stent  35  may at least partially deploy. For example, as portions of the pliant member  290  and the constrained stent  35  are disposed distally of the distal end of the outer sheath  250 , a distal portion of the stent  35  may expand radially away from the pliant member  290  and partially deploy. 
     In certain embodiments, as noted above, the deployment device and/or the actuator may be configured to incrementally deploy the stent  35 . For example, the outer sheath  250  may be configured to be proximally displaced relative to the inner sheath  270 , the pliant member  290 , and the constrained stent  35  in a step-wise or incremental manner. In various embodiments, the pliant member  290  may aid or enhance the deployment of the stent  35 . For example, the pliant member  290  may limit or prevent over-deployment of the stent  35  (e.g., “jumping” of the stent  35  out of the delivery catheter assembly  204  and/or jumping of the stent  35  off of the inner sheath  270 ) during deployment of the stent  35 . Further, the pliant member  290  may enhance the accuracy of the deployment of the stent  35 , for example, by limiting or preventing over-deployment or jumping of the stent. 
     In certain embodiments, the pliant member  290  may grip or support a constrained portion of the stent  35  such that the deployed portion of the stent  35  can be pushed and/or shortened during deployment of the stent  35 . For example, the delivery catheter assembly  204  and/or the deployment device  200  may be moved or manipulated such that a portion of the stent  35 , which is at least partially disposed in the pliant member  290 , can be pushed and/or shortened during deployment of the stent  35 . 
     In some embodiments, the delivery catheter assembly  204  may be configured to adjust a length of the stent  35  (e.g., the stent  35  may be shortened) during deployment of the stent  35  such that a user may select a length of the stent  35  (e.g., a custom length of the stent  35 ) based on a characteristic such as patient anatomy. In certain embodiments, the delivery catheter assembly  204  may have sufficient rigidity and/or deployment control such that a user may push and/or pull the stent  35  to control or determine the length of the stent  35  during deployment of the stent  35 . In various embodiments, the pliant member  290  may be configured such that the stent  35  can remain in communication (e.g., direct, physical communication) with the delivery catheter assembly  204  and/or the deployment device  200  for the majority of the deployment of the stent  35 . 
     In some embodiments, the stent may be configured to allow or permit nesting and/or telescoping of the rows of the stent. For example, the stent may comprise a plurality of rows, wherein each row of the plurality of rows is configured to be disposed around at least a portion of an outer surface of an adjacent row. Such a configuration may provide a stent wherein an effective length of the stent can be adjusted during deployment of the stent by a user. 
     Upon deployment of a portion of the stent  35 , the stent  35  (e.g., the distal end of the stent  35 ) can be disposed against or engaged with a wall  47  of the vessel  45  (see, e.g.,  FIG. 12B ). Pushing or pulling on the stent  35  via the deployment device  200  can compress the stent  35  (i.e., reduce the distance between the coils of the stent  35 ) and/or stretch the stent  35  (i.e., increase the distance between the coils of the stent  35 ) along a portion of the stent  35  that is deployed but that is not engaged with the wall  47 . During such length adjustments, at least a portion of the non-deployed portion of the stent  35  may be engaged by the pliant member  290 . Such a configuration can provide a practitioner with enhanced flexibility during deployment of the stent  35 . For example, the practitioner can make adjustments (e.g., small adjustments) to the length of the stent  35 , for example, at or around branch vessels or other structures within a patient. Without the pliant member  290 , the stent  35  may collapse or accordion within the delivery catheter assembly  204  and/or the annular space  276  during an attempted length adjustment as described above. 
       FIG. 12C  depicts the delivery catheter assembly  204  in the third state, wherein the distal end of the outer sheath  250  has been proximally displaced relative to the proximal end of the stent  35 . Accordingly, in the third state the stent  35  may fully deploy within the vessel  45 . In some embodiments, the stent  35  may deploy such that it engages or interacts with the wall  47  of the vessel  45 . 
     Methods of preparing or loading a deployment device  200  are disclosed herein. In some embodiments, the methods of preparing the deployment device  200  can include obtaining a delivery catheter assembly  204 . The delivery catheter assembly  204  can include an outer sheath  250  and an inner sheath  270 , wherein the inner sheath  270  is disposed within the outer sheath  250 . 
     In certain embodiments, the delivery catheter assembly  204  may further include an intermediate sheath  260 , wherein the intermediate sheath  260  is disposed between the outer sheath  250  and the inner sheath  260 . Additionally, a distal end of the intermediate sheath  260  may be disposed proximally of the distal end of the outer sheath  250  and the distal end of the inner sheath  270 . 
     In various embodiments, the methods of preparing the deployment device  200  may include applying a pliant member  290  on at least a portion of the inner sheath  270 . For example, the pliant member  290  may be applied onto an outer surface of the inner sheath  250 , and the pliant member  290  may be coupled to the inner sheath  270 . The pliant member  290  may be applied to the inner sheath  270  by at least one of dipping, spraying, extrusion, reflowing, or another suitable technique. 
     As described above, the pliant member  290  may be configured to engage and/or retain a stent  35 . Furthermore, a stent  35  may be disposed or positioned around at least a portion of the pliant member  290 , and the stent  35  may be constrained, crimped, or loaded within the pliant member  290 . 
     The methods of preparing the deployment device  200  may further include disposing the outer sheath  250  over a portion of the stent  35 . Such a configuration of the outer sheath  50  in relation to the stent  35  may aid in constraining the stent  35  within the pliant member  290 . When the stent  35  is in the constrained configuration, a distal end of the intermediate sheath  260  may be disposed proximally of a proximal end of the pliant member  290 . 
     Methods of deploying a stent  35  are also provided. In some embodiments, a delivery catheter assembly  204  may be obtained. The delivery catheter assembly  204  may comprise an outer sheath  250 , an intermediate sheath  260 , and an inner sheath  270 . Furthermore, a pliant member  290  can surround a portion of the inner sheath  270 . The methods of deploying the stent  35  may include positioning the stent  35  around the pliant member  290  and/or constraining the stent  35  within the pliant member  290 . In various embodiments, the outer sheath  250  may also be disposed over the stent  35  (e.g., such that the stent  35  is constrained within a portion of the pliant member  290 ). 
     In certain embodiments, methods of deploying the stent  35  may further include displacing an actuator, for example, an actuator that is operably coupled to the delivery catheter assembly  204 . Displacement of the actuator can be configured to proximally displace the outer sheath  250  relative to each of the pliant member  290  and the constrained stent  35  such that the stent  35  is partially deployed. As described above, the actuator may be configured to incrementally deploy the stent  35 . Accordingly, methods of deploying the stent  35  can also include adjusting the position of the partially deployed stent  35  after each displacement of the actuator. The actuator can be displaced and/or the position of the stent  35  adjusted until the stent  35  is fully deployed. As can be appreciated, each of the methods provided herein can also be adapted for use with the deployment device  100  and the components thereof. 
       FIG. 14  is a perspective view of a deployment device  400 . The deployment device  400  comprises a handle assembly  402  adjacent the proximal end of the deployment device  400 . An elongate delivery catheter assembly  404  extends distally from the handle assembly  402  to a distal tip or delivery tip  474 . The handle assembly  402  may provide a proximal user input, with one or more components configured to allow a practitioner to deploy or otherwise manipulate a stent disposed within the delivery catheter assembly  404 . 
     As discussed above in reference to the deployment device  100 , while in use, the handle assembly  402  may be disposed outside of a patient&#39;s body, while the delivery catheter assembly  404  is advanced to a treatment location within the patient&#39;s body. As detailed below, a stent may be disposed within a portion of the delivery catheter assembly  404  such that a practitioner may deploy the stent from a distal end of the delivery catheter assembly  404  through manipulation of one or more components of the handle assembly  402 . 
       FIG. 15  is a cross-sectional view of a portion of the deployment device  400  of  FIG. 14 . Specifically,  FIG. 15  is a side view of a portion of the deployment device  400  of  FIG. 14 , taken through a cross-sectional plane extending vertically and intersecting a longitudinal axis of the deployment device  400 , when the deployment device  400  is positioned as shown in  FIG. 14 . The longitudinal axis of the deployment device  400  extends along the center of the delivery catheter assembly  404 , including along the center of components of the delivery catheter assembly  404  which overlap with the handle  402  assembly, such as an intermediate sheath  460 , as shown in  FIG. 15 . 
     As the handle assembly  402  is configured to be grasped or otherwise manipulated by a user and the delivery catheter assembly  404  is configured to extend to a treatment location within a patient&#39;s body, along the longitudinal axis, the delivery catheter assembly  404  extends in a distal direction away from the handle assembly  402 . The proximal direction is opposite, correlating to a direction defined along the longitudinal axis, extending from the distal tip  474  toward the handle assembly  402 . 
       FIG. 15  depicts various internal components of the handle assembly  402 , exposed by the cross-sectional view. A portion of the delivery catheter assembly  404  is also shown extending from the handle assembly  402 . The handle assembly  402  comprises a housing  410 . The housing  410  surrounds certain components of the handle assembly  402 , as shown, providing a grip surface for a practitioner. 
     The actuator  420  is operably coupled to the housing  410 . Manipulation of the actuator  420  with respect to the housing  410  may be configured to deploy the stent, as further detailed below. In the depicted embodiment, the actuator  420  is rotatably coupled to the housing  410  by a pin  412 . The pin  412  extends from the housing  410  and may be integrally formed with one or more other portions of the housing  410 . As shown, the pin  412  extends through a pin aperture  422  in the actuator  420 . As discussed above in reference to the actuator  120  and the housing  110 , other arrangements for operably coupling the actuator  420  and the housing  410  are also within the scope of this disclosure. 
     The actuator  420  comprises an input portion  421  extending from the pin aperture  422 . In the depicted embodiment, the input portion  421  comprises a surface, at least partially exposed with respect to the housing  410 . In operation, a user may manipulate the actuator  420  by exerting a force on the input portion  421 , illustrated by the arrow labeled “input” in  FIG. 15 , displacing the input portion  421  generally toward the longitudinal axis of the deployment device ( 400  of  FIG. 14 ) and causing the actuator  420  to rotate about the pin  412  with respect to the housing  410 . Displacement of the actuator  420  due to a force such as illustrated by the arrow labeled “input” corresponds to “depression” of the actuator  420  or “depression of the actuator  420  with respect to the housing  410 .” 
     The actuator  420  may further comprise a transfer arm  423  extending from the pin aperture  422 . The transfer arm  423  may be rigidly coupled to the input portion  421 , including embodiments wherein both the transfer arm  423  and the input portion  421  are integrally formed with the rest of the actuator  420 . The transfer arm  423  extends to a ratchet slide engaging portion  424 . Depression of the input portion  421 , in the direction shown by the arrow labeled “input,” displaces the transfer arm  423  as the actuator  420  is rotated about the pin  412 . 
     Depression of the input portion  421  thus causes displacement of the ratchet slide engaging portion  424  with respect to the housing  410 . This displacement of the ratchet slide engaging portion  424  can be understood as rotation about the pin  412  having a proximal translation component and a vertical translation component, as rotation of the input portion  421  in the direction indicated by the arrow labeled “input” will displace (with respect to the housing  410 ) the ratchet slide engaging portion  424  both proximally and vertically. 
     A spring  415  may be disposed between the actuator  420  and the housing  410 . The spring  415  may be configured to resist displacement of the actuator  420  in the direction indicated by the arrow labeled “input” and may be configured to return the actuator  420  to the relative position shown in  FIG. 15  after it has been depressed by a user. When the handle assembly  402  is unconstrained, the spring  415  may thus maintain (or return to) the relative position of the actuator  420  with respect to the handle  410  as shown in  FIG. 15 . 
     As the actuator  420  is depressed with respect to the housing  410 , the spring  415  compresses and the ratchet slide engaging portion  424  is displaced as described above. Again, the displacement of the ratchet slide engaging portion  424  with respect to the housing  410  can be understood as having a proximal component and a vertical component. 
     The ratchet slide engaging portion  424  may be operably coupled to a ratchet slide  430  such that displacement of the ratchet slide engaging portion  424  likewise displaces the ratchet slide  430 . The ratchet slide  430  may be constrained such that the ratchet slide  430  is configured only for proximal or distal displacement with respect to the housing  410 . Thus, operable coupling of the ratchet slide engaging portion  424  to the ratchet slide  430  may allow for sliding interaction between the ratchet slide engaging portion  424  and the ratchet slide  430  such that only the proximal or distal component of the displacement of the ratchet slide engaging portion  424  is transferred to the ratchet slide  430 . Stated another way, the ratchet slide  430  may be displaced in a direction parallel to the longitudinal axis of the deployment device  400  while the input displacement may be at an angle to the longitudinal axis of the deployment device  400 . It is noted that, in the configuration shown in  FIG. 15 , a safety member  480  (similar to the safety member  180 ) may prevent proximal displacement of the ratchet slide  430 . Discussion herein relating to displacement of the ratchet slide  430  and related components may thus be understood as disclosure relevant to a configuration of the handle assembly  402  in which the safety member  480  has been removed. 
     As the actuator  420  is depressed with respect to the housing  410 , the ratchet slide  430  may thus be proximally displaced with respect to the housing  410 . One or both of the ratchet slide  430  and actuator  420  may also interact with the housing  410  such that there is a positive stop to arrest the depression of the actuator  420  and/or proximal displacement of the ratchet slide  430 . This positive stop may be an engaging ledge, shoulder, lug, detent, or other feature coupled to the housing  410 , including features integrally formed on the housing  410 . As depicted, the positive stop can be disposed proximally of a proximal end of the ratchet slide  430 . For example, the proximal end of the ratchet slide  430  can interact with a portion of the housing  410  (e.g., a ledge, shoulder, etc.) disposed proximally of the proximal end of the ratchet slide  430 . Accordingly, the handle assembly  402  may be configured such that the ratchet slide  430  is displaced or “travels” as much as possible during depression of the actuator  420 . 
     A full stroke of the actuator  420  may thus correspond to displacement from the unconstrained position shown in  FIG. 15 , to the positive stop caused by interaction with the housing  410  when the actuator  420  is depressed. A partial stroke of the actuator  420  may correspond to displacement from the unconstrained position shown in  FIG. 15 , to each and/or any position prior to the positive stop caused by interaction with the housing  410  when the actuator  420  is depressed. Release of the actuator  420  following a full stroke or a partial stroke may then result in a return of the actuator  420  to the unconstrained state, due to the biasing force provided by the spring  415 . The unconstrained state shown in  FIG. 15  refers to lack of constraint due to user input. In this state, the spring  415  may be partially compressed, and interaction between the actuator  420  and the housing  410  may prevent rotation of the actuator  420  about the pin  412  in the opposite direction to depression of the actuator  420 , or the return direction. In other words, interaction between the actuator  420  and the housing  410  (or features of the housing  410 ) may create a positive stop to the return motion of the actuator  420  as well. 
     With continued reference to  FIG. 15 , the ratchet slide  430  may thus be proximally displaced during depression of the actuator  420 . Again, such displacement may correspond to a configuration in which the safety member  480  has been removed. Proximal displacement of the ratchet slide  430  may also proximally displace a carrier  440  due to interaction between one or more carrier engaging ratchet lugs  436  on the ratchet slide  430  and a ratchet slide engaging arm  446  coupled to the carrier  440 . In some embodiments, the carrier  440  may be coupled to an outer sheath  450 . For example, the carrier  440  may be fixedly and/or rigidly coupled to the outer sheath  450 . In certain embodiments, an inner sheath  470  may be coupled to the handle assembly  402 . For example, the inner sheath  470  may be fixedly and/or rigidly coupled to the handle assembly  402 . 
       FIG. 16A  is a perspective view of the ratchet slide  430  of the deployment device  400  of  FIGS. 14 and 15 .  FIG. 16B  is a cross-sectional view of the ratchet slide  430  of  FIG. 16A , taken through a vertical plane disposed along a longitudinal centerline of the ratchet slide  430 . When the ratchet slide  430  is disposed within the handle assembly  402  of  FIG. 15 , this cross-sectional plane would intersect the longitudinal axis of the deployment device  400 . 
     As shown in  FIGS. 15, 16A, and 16B , the ratchet slide  430  may comprise a plurality of carrier engaging ratchet lugs  436 . The carrier engaging ratchet lugs  436  may be spaced at even intervals along the longitudinal direction of the ratchet slide  430 . As depicted, the plurality of carrier engaging ratchet lugs  436  may be disposed semi-continuously. For example, consecutive carrier engaging ratchet lugs  436  may be spaced about 5 mm or less from each other, about 4 mm or less from each other, about 3 mm or less from each other, about 2 mm or less from each other, about 1 mm or less from each other, or any other suitable distance from each other. In the figures, exemplary carrier engaging ratchet lugs are denoted with reference numeral  436 , while the distal most carrier engaging ratchet lug, disposed at the distal end of the ratchet slide  430 , is denoted with reference numeral  436   a.    
     The ratchet slide  430  further comprises a ratchet slide safety opening  439  (similar to the ratchet slide safety opening  139 ). The ratchet slide  430  can further comprise an actuator engaging opening  434 , which is discussed in more detail below. 
     As noted above, interaction between the ratchet slide engaging portion  424  of the actuator  420  and the ratchet slide  430  may proximally displace the ratchet slide  430  with respect to the housing  410 . Engagement between the carrier  440  and one of the carrier engaging ratchet lugs  436  may also proximally displace the carrier  440  as the ratchet slide  430  is proximally displaced with respect to the housing  410 . In the configuration of  FIG. 15 , the ratchet slide engaging arm  446  of the carrier  440  is engaged with the distal most carrier engaging ratchet lug  436   a.    
       FIG. 17  is a side view of the carrier  440  of the deployment device  400  of  FIGS. 14 and 15 . As shown in  FIG. 17 , the ratchet slide engaging arm  446  extends radially away from a longitudinal axis of the carrier  440 . When the carrier  440  is disposed within the handle assembly  402  of  FIG. 15 , the longitudinal axis of the carrier  440  is disposed along the longitudinal axis of the deployment device  400 . 
     As depicted, the ratchet slide engaging arm  446  comprises an angled portion or “toenail” portion  447  at a distal end of the ratchet slide engaging arm  446 . As shown, the angled portion  447  extends radially away from the longitudinal axis of the carrier  440  at a greater angle than the radial extension of the ratchet slide engaging arm  446  in relation to the longitudinal axis of the carrier  440 . In some embodiments, the angled portion  447  can enhance engagement between the ratchet slide engaging arm  446  and a given carrier engaging ratchet lug  436  as compared to a ratchet slide engaging arm lacking an angled portion. For example, due at least in part to the semi-continuous disposition of the plurality of the carrier engaging ratchet lugs  436  (as shown in  FIGS. 16A and 16B ), the angled portion  447  of the ratchet slide engaging arm  446  can allow or permit the ratchet slide engaging arm  446  to deflect radially adjacent to or against at least a portion of the ratchet slide  430  at or adjacent the given carrier engaging ratchet lug  436 . The angled portion  447  can provide clearance for the ratchet slide engaging arm  446 , allowing the angled portion to engage carrier engaging ratchet lugs  436  (even when closely spaced) without adjacent lugs interfering with the position of the ratchet slide engaging arm  446  and preventing full engagement. 
       FIG. 18  is a cross-sectional view of a portion of the deployment device  400  shown in  FIGS. 14 and 15 . Specifically, the actuator  420 , the ratchet slide  430 , and the carrier  440  are shown in  FIG. 18 , in the same relative positions, and along the same cross-sectional plane as in  FIG. 15 .  FIG. 18A  is a partial cut-away view of a portion of the cross-sectional view of  FIG. 18 . As shown, a portion of the ratchet slide  430  has been cut away in this view to show an engagement of the ratchet slide engaging portion  424  with the actuator engaging opening  434 . 
     Referring to  FIGS. 15-18A , during depression of the actuator  420  with respect to the housing  410 , the actuator  420  rotates around the pin aperture  422 . This rotation causes displacement of the ratchet slide engaging portion  424  of the actuator  420 . The component of this displacement correlating to proximal displacement of the ratchet slide engaging portion  424  also proximally translates the ratchet slide  430  due to interaction between the ratchet slide engaging portion  424  of the actuator  420  and the actuator engaging opening  434  of the ratchet slide  430 . Stated another way, the walls or faces that define the actuator engaging opening  434  may contact the ratchet slide engaging portion  424  such that the ratchet slide  430  is displaced when the actuator  420  is displaced. 
     Proximal displacement of the ratchet slide  430  also proximally displaces the carrier  440  due to interaction between the carrier engaging ratchet lugs  436  and the ratchet slide engaging arm  446 . In the depicted embodiment, a distal surface of the angled portion  447  of the ratchet slide engaging arm  446  is in contact with a proximal face of the distal most carrier engaging ratchet lug  436   a . This contact exerts proximal force on the distal surface of the angled portion  447  of the ratchet slide engaging arm  446 , displacing the carrier  440  in a proximal direction. Accordingly, the ratchet slide  430  and carrier  440  will move proximally until the actuator  420  reaches the end of the stroke (e.g., either a partial stroke or a full stroke). 
       FIG. 19  is a cross-sectional view of the housing  410  and the carrier  440  in the same relative positions shown in  FIG. 15 . The cross-sectional plane of  FIG. 19  extends along the longitudinal axis of the deployment device  400 ; however, the cross-sectional plane of  FIG. 19  extends horizontally, orthogonal to the cross-sectional planes of  FIGS. 15, 16B, and 18 . 
     As shown in  FIG. 19 , the carrier  440  comprises a housing engaging arm  448  extending radially away from a longitudinal axis of the carrier  440 . The housing  410  comprises a plurality of carrier engaging housing lugs  418 . In  FIG. 19 , exemplary carrier engaging housing lugs are denoted by reference numeral  418 , with the distal most carrier engaging housing lug denoted by reference numeral  418   a.    
     As depicted, the housing engaging arm  448  comprises an angled portion or “toenail” portion  449  at a distal end of the housing engaging arm  448 . As shown, the angled portion  449  extends radially away from the longitudinal axis of the carrier  440  at a greater angle than the radial extension of the housing engaging arm  448  in relation to the longitudinal axis of the carrier  440 . In some embodiments, the angled portion  449  can enhance engagement between the housing engaging arm  448  and a given carrier engaging housing lug  418  as compared to a housing engaging arm lacking an angled portion. For example, due at least in part to the semi-continuous disposition of the plurality of the carrier engaging housing lugs  418 , the angled portion  449  of the housing engaging arm  448  can allow or permit the housing engaging arm  448  to deflect radially adjacent to or against at least a portion of the ratchet slide  430  at or adjacent the given carrier engaging housing lug  418 . As with the angled portion  447  discussed above, the angled portion  449  can provide clearance for the housing engagement arm  448 , allowing the angled portion  449  to engage carrier engaging housing lugs  418  (even when closely spaced) without adjacent lugs interfering with the position of the housing engagement arm  448  and preventing full engagement. 
     Referring to  FIGS. 15-19 , as interaction between the actuator  420 , ratchet slide  430 , and carrier  440  displaces the carrier  440  with respect to the housing  410  (as shown and described above), the housing engaging arm  448  (shown in  FIG. 19 ) of the carrier  440  will deflect radially inward due to contact with one of the carrier engaging housing lugs  418 . For example, from the position shown in  FIG. 19 , as interaction between the distal most carrier engaging ratchet lug  436   a  and the ratchet slide engaging arm  446  of the carrier  440  draws the carrier  440  proximally, the distal most carrier engaging housing lug  418   a  causes the housing engaging arm  448  to displace radially inward. The housing engaging arm  448  will continue to deflect radially inward until the distal end of the housing engaging arm  448  is positioned proximal of the distal most carrier engaging housing lug  418   a , at which point the housing engaging arm  448  will return to the radially outward configuration shown in  FIG. 19 . The point at which the housing engaging arm  448  moves proximally of the distal most carrier engaging housing lug  418   a  may correspond to the stroke of the actuator  420  (e.g., a partial stroke or a full stroke), such that engagement between the housing engaging arm  448  and the next carrier engaging housing lug  418  (moving in a proximal direction) occurs at the end of the stroke. In some embodiments, each carrier engaging housing lug  418  (or at least a portion of each of the carrier engaging housing lugs  418 ) may be disposed such that a position of the carrier engaging housing lug  418  corresponds to a position of a carrier engaging ratchet lug  436 . 
     Further, a stroke of the actuator  420  can correspond to displacement of the carrier  440  past multiple carrier engaging housing lugs  418 . For closely spaced carrier engaging housing lugs  418 , the actuator  420  may thus be configured to displace the carrier  440  over a semi-continuous range as the carrier  440  is advanced along the carrier housing engaging lugs  418 . Partially depressing the actuator  420  may displace the carrier  440  along and past the carrier engaging housing lugs  418 , and upon release of the actuator  420 , the carrier  440  may remain engaged with the most-recently passed carrier housing engaging lug  418 . Thus, increments of displacement of the carrier  440  may correspond to the spacing the carrier housing engaging lugs  418 , rather than the length of the stroke of the actuator  420 . 
     As the actuator  420  is released following the stroke, interaction between the spring  415 , the housing  410 , and the actuator  420  will return the actuator  420  to the unconstrained position (the position shown in  FIG. 15 ) as discussed above. Corresponding rotation of the actuator  420  about the pin aperture  422  will thus correlate to displacement of the ratchet slide engaging portion  424 , including a component of displacement in the distal direction. Interaction between the ratchet slide engaging portion  424  and the actuator engaging opening  434  will then correlate to distal displacement of the ratchet slide  430 . Thus, when the actuator  420  is released at the end of a stroke, the actuator  420 , the spring  415 , and the ratchet slide  430  return to the same positions relative to the housing  410  as shown in  FIG. 15 . 
     As the actuator  420  returns to the unconstrained position, however, interaction between the housing engaging arm  448  and the carrier engaging housing lug  418  prevents distal displacement of the carrier  440 . Specifically, the distal surface of the angled portion  449  of the housing engaging arm  448  will be in contact with a proximal facing surface of a carrier engaging housing lug  418 , the interaction preventing the carrier  440  from returning to the pre-stroke position. In the exemplary stroke discussed above, the distal most carrier engaging housing lug  418   a  displaced the housing engaging arm  448  during the stroke, and the housing engaging arm  448  engaged with the distal most carrier engaging housing lug  418   a  following the stroke. Subsequent strokes move the carrier  440  along the plurality of carrier engaging housing lugs  418  in a proximal direction. 
     As the actuator  420  returns to the unconstrained state, radially inward displacement of the ratchet slide engaging arm  446  of the carrier  440  allows the ratchet slide  430  to move distally with respect to the carrier  440 , as engagement between the carrier  440  and the carrier engaging housing lugs  418  arrest distal displacement of the carrier  440 . 
     Referring to  FIGS. 15-19 , with particular reference to the view of  FIG. 18 , distal displacement of the ratchet slide  430  with respect to the carrier  440  creates interaction between the carrier engaging ratchet lugs  436  and the angled portion  447  of the ratchet slide engaging arm  446  causing the ratchet slide engaging arm  446  to displace radially inward. The proximal facing surface of the carrier engaging ratchet lugs  436  may be angled to facilitate this interaction. During depression of the actuator  420 , engagement between the distal most carrier engaging ratchet lug  436   a  can displace the carrier  440  in a proximal direction; during the return of the actuator  420 , another carrier engaging ratchet lug  436  (in a proximal direction) can cause the radially inward displacement of the ratchet slide engaging arm  446  until the angled portion  447  of the ratchet slide engaging arm  446  is proximal of that carrier engaging ratchet lug  436 . At that point the ratchet slide engaging arm  446  returns to a radially outward position (analogous to that shown in  FIG. 18 ) though the distal surface of the angled portion  447  of ratchet slide engaging arm  446  is now engaged with a proximal face of another carrier engaging ratchet lug  436  (again in a proximal direction). 
     During a full stroke, engagement between a first carrier engaging ratchet lug  436  can displace the carrier  440  in a proximal direction; during the return of the actuator  420 , a plurality of the next carrier engaging ratchet lugs  436  (in a proximal direction) can cause a plurality of radially inward displacements of the ratchet slide engaging arm  446  as the angled portion  447  of the ratchet slide engaging arm  446  moves proximally in relation to a plurality of the carrier engaging ratchet lugs  436  during the full stroke. At that point the angled portion  447  of the ratchet slide engaging arm  446  returns to a radially outward position (analogous to that shown in  FIG. 18 ) though the distal surface of the angled portion  447  of ratchet slide engaging arm  446  is now engaged with a proximal face of a second carrier engaging ratchet lug  436  (again in a proximal direction). In such a configuration, a plurality of carrier engaging ratchet lugs  436  may be disposed between the first carrier engaging ratchet lug  436  engaged during the stroke and the second carrier engaging ratchet lug  436  engaged at the end of that same stroke. For example, 1, 2, 3, 4, 5, 6, or more carrier engaging ratchet lugs  436  may be disposed between the first carrier engaging ratchet lug  436  engaged during a single stroke and the second carrier engaging ratchet lug  436  engaged at the end of that single stroke. 
     Displacement of the ratchet slide  430  sufficient to move to engagement with a subsequent carrier engaging ratchet lug  436  may correspond with the magnitude of ratchet slide  430  displacement corresponding to a return of the actuator  420 . One return of the actuator  420  following at least a partial stroke can move the ratchet slide  430  such that a plurality of carrier engaging ratchet lugs  436  may serially engage the carrier  440  during the stroke. 
     Accordingly, as described above, depressing the actuator  420  for a full stroke, then allowing the actuator  420  to return to the unconstrained position, displaces the carrier  440  with respect to the housing  410  in discrete increments, corresponding to the distance between a plurality of carrier engaging housing lugs  418  along the longitudinal direction. Depressing the actuator  420  for a partial stroke, then allowing the actuator  420  to return to the unconstrained position, can displace the carrier  440  with respect to the housing  410  in discrete increments, corresponding to the distance between adjacent carrier engaging housing lugs  418  along the longitudinal direction. 
     As detailed below, the relative position of the carrier  440  with respect to the housing  410  may correlate to the degree of deployment of a stent from the deployment device  400 . Thus, visual, audible, and tactile feedback as to the position of the carrier  440  provides a user with information regarding stent deployment during use of the deployment device  400 . This information may correlate to increased control during deployment as the practitioner quickly and intuitively can surmise the degree of stent deployment. 
     In some configurations, at least a portion of the elongate delivery catheter assembly  404  may lengthen and/or stretch during use of the deployment device  400 . The configuration of the deployment device  400  (e.g., comprising the semi-continuous disposition of the plurality of the carrier engaging ratchet lugs  436 ) can allow or permit more than one increment of displacement of the carrier  440  in relation to the ratchet slide  430 . Furthermore, the configuration of the deployment device  400  can allow or permit finely tuned deployment of the stent. For example, the stent can be deployed in about a 1 mm increment, about a 2 mm increment, about a 3 mm increment, about a 4 mm increment, about a 5 mm increment, or any other suitable increment. 
     The increments of displacement of the carrier  440  may be about 0.5 mm, about 1 mm, about 2 mm, about 3 mm, about 4 mm, about 5 mm, about 10 mm, about 25 mm, about 50 mm, about 100 mm, or any other suitable increment of displacement. The incremental displacement of the carrier  440  may further facilitate partial deployment of a stent, allowing a practitioner to deploy the stent in increments, potential adjusting or confirming the position of the stent between these increments 
     Without further elaboration, it is believed that one skilled in the art can use the preceding description to utilize the present disclosure to its fullest extent. The examples and embodiments disclosed herein are to be construed as merely illustrative and exemplary and not a limitation of the scope of the present disclosure in any way. It will be apparent to those having skill in the art, and having the benefit of this disclosure, that changes may be made to the details of the above-described embodiments without departing from the underlying principles of the disclosure herein.