Patent Publication Number: US-2022234014-A1

Title: Mixing Device and Methods For Making Bone Cement

Description:
PRIORITY CLAIM 
     This application claims priority to and all the benefits of U.S. Provisional Patent Application No. 62/861,698, filed Jun. 14, 2019, the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND 
     A common source of back pain is a vertebral compression fracture in which a weakened or injured vertebral body loses height or collapses. The weakening of the vertebral body may be due to acute injury or, more often, degenerative changes such as osteoporosis. One treatment modality includes vertebral augmentation in which the height of the vertebral body is elevated or restored, and stabilized at the elevated or restored height with curable bone cement. The bone cement typically includes bone cement components (e.g., a powdered polymer and a liquid monomer), which are packaged separately and mixed immediately prior to or during the vertebral augmentation procedure. Efficient, uniform, safe, and reproducible mixing of the bone cement components is an area of particular interest in development to ensure the bone cement has the expected mechanical properties and characteristics. Known devices requiring manual mixing (e.g., “open bowl” or vacuum techniques) are inefficient by requiring operating room staff intensely agitate the bone cement components. Different staff may mix the bone cement components with varying or differing intensities and/or for varying or differing durations that may result in the bone cement not being particularly uniform or reproducible. Further, certain manual mixing devices may undesirable expose the staff to the bone cement components. Known motorized mixing devices may overcome some of the aforementioned issues, but require the staff to engage a workflow that is overly complex, especially if the staff is unfamiliar with the device. Therefore, there is a need in the art for an improved mixing device and methods for making bone cement that overcome one or more of the aforementioned shortcomings. 
     SUMMARY 
     A first aspect of the present disclosure is directed to a mixing device for making bone cement from bone cement components. A chamber defines an inlet opening and has first and second ends and a longitudinal axis extending between the first and second ends. A first region of the chamber is defined longitudinally between the first end of the chamber and an end of the inlet opening nearest to the second end of the chamber. A second region of the chamber is defined longitudinally between the first region and the second end of the chamber. The mixing device includes a piston disposed in the chamber. The piston includes a face. The mixing device includes a mixing paddle rotatable within the chamber. The face of the piston is configured to be located within the first region of the chamber such that the chamber is at or below atmospheric pressure as the mixing paddle rotates to mix the bone cement components to make a bone cement mixture. The piston is movable along the longitudinal axis to position the face within the second region of the chamber to provide a fluid-tight closure between the piston and the chamber such that further movement of the piston within the second region compresses the bone cement mixture within the chamber. 
     In some implementations, a motor is operably coupled to the piston and the mixing paddle and configured to effectuate at least one of movement of the piston and rotation of the mixing paddle. The housing further may define an outlet port adjacent the second end of the chamber. A first switch may be coupled to the housing and connected to the motor. The first switch may be movable to an activated state in which the first switch activates the motor while the piston is within the first region. The first switch may be a momentary switch biased toward the deactivated state. A second switch may be coupled to the housing and connected to the motor. The second switch may be movable to a deactivated state in which the second switch deactivates the motor while the piston is within the second region. The second switch may be a non-momentary switch initially in the activated state. The first and second switches may be wired in series with the motor. 
     In some implementations, an actuator is coupled to the housing and movable to engage the switch and maintain the switch in the activated state against the bias while the piston moves from the first region to the second region. A transfer gear may be coupled to the motor and rotatable during the operational cycle. A stop nut may be configured to translate along the transfer gear and engage the actuator while the piston is within the second region. 
     A second aspect of the disclosure involves a method of making bone cement with the mixing device according to the first aspect of the disclosure, and optionally, any of its corresponding implementations. 
     A third aspect of the present disclosure is directed to a mixing device for making bone cement from bone cement components. The mixing device includes a housing, and a chamber within the housing. The chamber has a first region, and a second region separate from the first region. The mixing device includes a mixing paddle rotatable within the chamber to mix bone cement components to make a bone cement mixture. A piston is movable within the chamber to compress the bone cement components. A motor is coupled to the piston and the mixing paddle. A first switch is connected to the motor. The first switch being momentary and biased to a deactivated state in which the first switch prevents activation of the motor. The first switch is configured to move from the deactivated state to an activated in which the switch initiates an operational cycle by activating the motor to effectuate at least one of movement of the piston and rotation of the mixing paddle. A second switch is wired in series with the first switch and the motor. The second switch is non-momentary and initially disposed an activated state to permit activation of the motor. The second switch is configured to be moved from the activated state to a deactivated state in which the motor is deactivated to terminate the operational cycle. The piston is configured to move within the chamber from a first region to a second region to mix and compresses the bone cement mixture within the chamber. The piston is within the first region during actuation of the first switch, and within the second region during actuation of the second switch. 
     In some implementations, the chamber is at or below atmospheric pressure with the piston in the first region, and the chamber is above atmospheric pressure with the piston in the second region. An actuator may be coupled to the housing and movable between a first position in which the actuator is spaced apart from the first switch, and a second position in which the actuator engages the first switch to actuate the first switch. 
     A fourth aspect of the disclosure involves a method of making bone cement with the mixing device according to the third aspect of the disclosure, and optionally, any of its corresponding implementations. 
     A fifth aspect of the present disclosure is directed to a mixing device for making bone cement from bone cement components. The mixing device includes a housing, and a chamber within the housing. The chamber defines an inlet opening configured to receive bone cement components. A mixing paddle is rotatable within the chamber to mix the bone cement components to make a bone cement mixture. A piston is movable within the chamber to compress the bone cement components. A motor is coupled to the piston and the mixing paddle. A first switch is mounted to the housing connected to the motor, the first switch initially in a deactivated state. A second switch is mounted to the housing and spaced from the first switch. The second switch is in an activated state. The first and second switches wired in series with the motor. An actuator is coupled to the housing and movable between a first position in which the actuator is spaced apart from the first switch and the inlet opening is open to the ambient environment, and a second position in which the actuator engages the first switch to move the first switch from the deactivated state to the activated state. A stop nut is movable to be engaged with the second switch to move the second switch from the activated state to the deactivate state. 
     In some implementations, the actuator is a slider comprising a slider body, an arm extending from an underside of the slider body. The arm is configured to be deflected laterally and into engagement with the first switch. The first and second switches may be directly mounted to the housing at separate locations without being coupled to a printed circuit board. 
     A sixth aspect of the disclosure involves a method of making bone cement with the mixing device according to the fifth aspect of the disclosure, and optionally, any of its corresponding implementations. 
     A seventh aspect of the present disclosure is directed to a mixing device for making bone cement. The mixing device includes a housing, and a chamber within the housing. The chamber defines an inlet opening configured to receive bone cement components. The mixing device includes a mixing paddle rotatable within the chamber to mix the bone cement components to make a bone cement mixture. A piston is movable within the chamber to compress the bone cement components. A motor is coupled to the piston and the mixing paddle. A switch is connected to the motor. An actuator is coupled to the housing and movable between a first position and a second position. In the first position, the actuator is spaced apart from the switch and the inlet opening is open to the ambient environment. In the second position, the actuator engages the switch to simultaneously (i) move the switch from a deactivated state to an activated state in which the switch initiates an operational cycle by activating the motor to effectuate at least one of movement of the piston and rotation of the mixing paddle, and (ii) close the inlet opening. 
     In some implementations, the housing defines an aperture. The actuator may include a door arranged to be positioned between the inlet opening and the aperture when the actuator is in the second position. The inlet opening is positioned beneath the aperture such that the bone cement components being directed through the aperture further pass through the inlet opening and into the chamber under the influence of gravity. A funneling device may include a widened portion, and a stem sized to be received within the aperture of the housing. A flexible tether may couple the funneling device with the housing. The funneling device may include a detent on the stem. The detent is configured to releasably engage a complementary locking feature of the housing. 
     In some implementations, the actuator of the ninth aspect may be included on the mixing device of any one of first, third, fifth, and seventh aspects, and optionally, any of their corresponding implementations. 
     An eighth aspect of the disclosure involves a method of making bone cement with the mixing device according to the seventh aspect of the disclosure, and optionally, any of its corresponding implementations. 
     A ninth aspect is directed to a mixing device for making bone cement. The mixing device includes a housing having an upper shell, and a lower shell coupled to the upper shell. A chamber is within the housing. The chamber defines an inlet opening configured to receive bone cement components. A mixing paddle is rotatable within the chamber to mix the bone cement components to make a bone cement mixture. A piston is within the chamber to compress the bone cement components. A motor is coupled to the piston and the mixing paddle. The upper shell comprises a funnel having a sloped surface defining an aperture in communication with the inlet opening. 
     In some implementations the upper shell has an upper surface with the sloped surface extending downwardly away from the upper surface. The funnel may be frustoconical in shape. 
     In some implementations, the integrated funnel of the ninth aspect may be included on the mixing device of any one of first, third, fifth, and seventh aspects, and optionally, any of their corresponding implementations. 
     A tenth aspect of the disclosure involves a method of making bone cement with the mixing device according to the ninth aspect of the disclosure, and optionally, any of its corresponding implementations. 
     An eleventh aspect is directed to a mixing device for making bone cement. The mixing device includes a housing, and a chamber within the housing and defining an inlet opening configured to receive bone cement components. A mixing paddle is rotatable within the chamber to mix the bone cement components to make a bone cement mixture. A piston is movable within the chamber to compress the bone cement components. A motor is coupled to the piston and the mixing paddle. A display is coupled to the housing and configured to display information indicative of the operation of the mixing device. 
     In some implementations, the display is a liquid crystal display (LCD), a series of lights, a digital timer, or an analog timer. The information may be one of remaining time for operation of the mixing device, elapsed time of working with the bone cement, and estimated remaining time of working with the bone cement. 
     In some implementations, the display of the eleventh aspect may be included on the mixing device of any one of first, third, fifth, seventh, and ninth aspects, and optionally, any of their corresponding implementations. 
     A twelfth aspect of the disclosure involves a method of making bone cement with the mixing device according to the ninth aspect of the disclosure, and optionally, any of its corresponding implementations. 
     A thirteenth aspect of the present disclosure is directed to a mixing device for making bone cement. The mixing device includes a housing, and a chamber within the housing. The chamber has a first region, and a second region separate from the first region. The mixing device includes a mixing paddle rotatable within the chamber to mix bone cement components to make a bone cement mixture. A piston is movable within the chamber to compress the bone cement components. A motor is coupled to the piston and the mixing paddle. A switch is connected to the motor. The switch is configured to move between an activated state in which the switch initiates an operational cycle by activating the motor to effectuate at least one of movement of the piston and rotation of the mixing paddle, and a deactivated state in which the switch terminates the operational cycle by deactivating the motor. The switch is biased toward the deactivated state. An actuator is coupled to the housing and movable between a first position in which the actuator is spaced apart from the switch, and a second position in which the actuator engages the switch to move the switch from the deactivated state to the activated state and maintains the switch in the activated state against the bias. The piston is configured to move within the chamber from the first region to the second region such that, when the piston is within the second region, the actuator is mechanically disengaged from the switch to permit the biased return of the switch from the activated state to the deactivated state. 
     In some implementations, the switch is a momentary switch. A transfer gear may be coupled to the motor and rotatable during the operational cycle. A stop nut may be coupled to the transfer gear rotationally constrained relative to the transfer gear such that the stop nut is configured to translate along the transfer gear and engage the actuator to effectuate the mechanical disengagement of the actuator from the switch. The stop nut may include a nut portion having an inner diameter threadably engaging an outer diameter of the transfer gear, and a flange portion extending from the nut portion with the flange portion configured to engage the actuator to effectuate the mechanical disengagement of the actuator from the switch. 
     In some implementations, the actuator is a slider having a slider body, an arm extending from an underside of the slider body, and a stop feature coupled to the arm and configured to engage the switch. The slider may further include a ramping surface coupled to the arm and arranged to be engaged by the stop nut as the stop nut translates with rotation of the transfer gear, wherein the engagement of the stop nut with the ramping surface imparts flexion to the arm and disengage the stop feature from the switch. 
     A fourteenth aspect of the disclosure involves a method of making bone cement with the mixing device according to the third aspect of the disclosure, and optionally, any of its corresponding implementations. 
     A fifteenth aspect of the present disclosure is directed to a kit for performing a vertebral augmentation procedure with bone cement. The kit includes a mixing device for mixing bone cement components to make a bone cement mixture and compressing the bone cement mixture. The mixing device includes a chamber, a piston movable within the chamber, and a mixing paddle movable within the chamber. The chamber defines an inlet opening, and an outlet port in communication with the inlet opening. The kit includes a delivery device comprising a chamber defining an inlet port for receiving the bone cement from the mixing device. The kit further includes packaging sized to accommodate the mixing device and the delivery device. The inlet port of the delivery device is in communication with the outlet port of the mixing device such that the mixing device and the delivery device are removably coupled to one another within the packaging. The mixing device and the delivery device are configured to be removed from the packaging as a single unit. 
     In some implementations, a longitudinal axis of the chamber of the mixing device and a longitudinal axis of a chamber of the delivery device are parallel when the mixing device and the delivery device are removably coupled to one another such that the mixing device and the delivery device are disposed within the packaging in a side-by-side arrangement. The outlet port of the mixing device and the inlet port of the delivery device may be arranged perpendicular to each of the respective longitudinal axes to facilitate the side-by-side arrangement. 
     In some implementations, the kit includes a funneling device, and a flexible tether coupling the funneling device and the mixing device. The funneling device is configured to be removed from the packaging as the single unit. Alternatively, the funneling device may be integrated into the housing. The kit may further include a liquid monomer and a powdered polymer disposed within the sterile packaging. The packaging may be a blister pack. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages of the present disclosure will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings. It is to be understood that the drawings are purely illustrative and are not necessarily drawn to scale. 
         FIG. 1  is a rear perspective view of a mixing and delivery system including a mixing device and a delivery device. 
         FIG. 2  is a front perspective view of the mixing device. 
         FIG. 3  is a front perspective view of the mixing device with an upper shell of the housing removed. 
         FIG. 4  is a sectional elevation view of the mixing device showing a piston positioned within a first region of a chamber of the mixing device. 
         FIG. 5  is a sectional elevation view of the mixing device showing the piston positioned within a second region of the chamber of the mixing device. 
         FIG. 6  is a perspective view of a subassembly of the mixing device including a switch, the piston, and a mixing paddle. 
         FIG. 7  is a perspective view of a geartrain of the mixing device coupled to the piston and the mixing paddle. 
         FIG. 8  is an elevation view of the geartrain, the piston, and the mixing paddle. 
         FIG. 9  is an elevation view of the geartrain and the mixing paddle of  FIG. 7  with a transfer gear and a translation shaft removed to show the paddle drive gear coupling the mixing paddle to the geartrain. 
         FIG. 10  is an exploded view of a subassembly of the mixing device configured to effectuate longitudinal movement of the piston (and the mixing paddle) within the chamber, the subassembly including the transfer gear, the translation shaft, a rear chamber housing, and a push cap. 
         FIG. 11  an elevation view of components of the mixing device configured to effectuate automatic termination of the operational cycle, the components including a stop nut disposed on the transfer gear in a first position. 
         FIG. 12  an elevation view of the components of  FIG. 11  with the stop nut disposed on the transfer gear in a second position and engaging an actuator. 
         FIG. 13  is a perspective view of a slider forming the actuator. 
         FIG. 14  is a perspective view of the stop nut. 
         FIG. 15  is a top perspective view of a portion of the mixing device in which an implementation of the actuator is laterally deflected into engagement with an implementation of the switch. 
         FIG. 16  a top perspective view of a portion of the mixing device which an implementation of the stop nut is configured to engage a second switch to effectuate automatic termination of the operational cycle. 
         FIG. 17  is a rear perspective view of the mixing device with a release assembly in an unlocked position. 
         FIG. 18  is a perspective view of a front chamber housing including a transfer conduit. 
         FIG. 19A  is a detailed view of the transfer conduit and release assembly of  FIG. 17  within broken lines  19 A- 19 A. 
         FIG. 19B  is a detailed view of another implementation of the transfer conduit and release assembly. 
         FIG. 20  is a perspective view of the release assembly of  FIG. 19A . 
         FIG. 21  is a pictorial representation of a step of a method of using a kit including the mixing and delivery system of  FIG. 1 . 
         FIG. 22  is a pictorial representation of another step of the method. 
         FIG. 23  is a pictorial representation of another step of the method. 
         FIG. 24  is a pictorial representation of another step of the method. 
         FIG. 25  is a pictorial representation of another step of the method. 
         FIG. 26  is a front perspective view of a mixing and delivery system including a mixing device and a delivery device. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the figures, wherein like numerals indicate corresponding parts throughout the several views, a mixing and delivery system  100  is shown in  FIG. 1 . The system  100  includes a mixing device  102  for mixing a plurality of components to make a mixture, and a delivery device  104  for delivering the mixture to a target site. The system  100  is useful for any procedure where delivery of the mixture to the target site is indicated. In one example, the mixing device  102  mixes bone cement components to make a bone cement mixture, and the bone cement mixture is transferred to the delivery device  104 . In particular, the mixing device  102 , upon actuation, automatically performs an operational cycle including a mixing phase and a compression phase, and automatically transfers the bone cement to the delivery device  104  in an intuitive workflow to be described. The intuitive workflow promotes efficiency in the surgical suite as well as consistency of the bone cement mixture while reducing user exposure to the bone cement components. Once transferred to the delivery device  104 , the delivery device  104  is operated by the user to deliver the bone cement, for example, within the vertebral body during a vertebroplasty or a kyphoplasty procedure. An example of the delivery device  104  suitable for the present system is disclosed in commonly owned International Publication No. WO2019/200091, published Oct. 17, 2019, the entire contents of which is hereby incorporated by reference. Another example of the delivery device  104  suitable for the present system is disclosed in commonly owned U.S. Pat. No. 6,547,432, issued Apr. 15, 2003, the entire contents of which is hereby incorporated by reference. 
       FIG. 1  shows the delivery device  104  removably coupled to the mixing device  102 . The delivery device  104  includes an inlet port  106  configured to be removably positioned in sealed fluid communication with an outlet port  108  of the mixing device  102 . A release assembly  110  to be described in greater detail facilitates the connection between the mixing device  102  and the delivery device  104 , thereby establishing the communication between the inlet and outlet ports  106 ,  108 . The communication between the inlet and outlet ports  106 ,  108  further establishes fluid communication between a chamber  112  (see  FIGS. 4 and 5 ) of the mixing device  102  and a chamber (not identified) internal to the delivery device  104  for transferring of the bone cement mixture. 
     The mixing device  102  includes a housing  116 .  FIG. 1  and  FIGS. 2 and 3  show implementations of the housing  116  in which like numbers are like components, but with differences in features and design. The housing  116  of  FIG. 1 , for example, includes a cradle  114  and/or a hook  117  coupled to the housing  116  for supporting the delivery device  104 . The cradle  114  is sized and shaped to facilitate ease with decoupling the housing  118  of the delivery device  104  from the mixing device  102 , and the hook  117  may be sized and shaped to facilitate ease with transporting and decoupling an extension tube  105  of the delivery device  104 .  FIG. 1  shows the cradle  114  as an arcuate projection generally sized to a portion of the housing  118  of the delivery device  104 . In such a coupled configuration, the cradle  114  cooperates with the release assembly  110  to permit the system  100  to be moved as a unit, for example, with one hand. In one configuration, the outlet port  108  being located on a side of the mixing device  102  permits the delivery device  104  and the mixing device  102  to be packaged in the coupled configuration before deployment in the surgical suite with advantages to be later explained in greater detail. However, other locations of the outlet port  108  are also contemplated. 
     The implementation of  FIG. 2  shows the cradle  114  further including a control surface  115  configured to receive an input from a user to permit removal of the housing  118  of the delivery device  104  from the cradle  114 . In particular, the cradle  114  may be formed from materials permitting the cradle  114  to flex upon the input from the user. Absent the user input, the cradle  114  may provide a retention force to the housing  118  of the delivery device  104 . In another implementation, the retention force from a transfer conduit  306 ,  306 ′ of the mixing device  102  and a release assembly  110  of the delivery device  104  (see  FIGS. 17-20 ) is sufficient to maintain relative position of the mixing device  102  and the delivery device  104 . The cradle  114  supports the delivery device  104 , but otherwise provides no retention force. 
     Referring now to  FIG. 2 , the mixing device  102  includes the housing  116 , which may be formed from suitable materials and manufacturing processes. The housing  116  may include an upper shell  120 , and a lower shell  122  coupled to the upper shell  120 . Cavities defined by each of the upper and lower shells  120 ,  122  are sized to accommodate most of the components of the mixing device  102 . The upper and lower shells  120 ,  122  may be removably or permanently coupled to one another. With the mixing device  102  possibly being a disposable component after a single use, the need to access an interior  124  of the housing  116  may be infrequent. Yet in such instances, the housing  116  may include a decoupling feature  126  configured to receive an input from the user to decouple the upper shell  120  from the lower shell  122 , thereby exposing the components housed within the interior  124  of the housing  116 .  FIG. 1  shows the decoupling feature  126  as a tab  128  adjacent a grip feature  130  at the interface between the upper and lower shells  120 ,  122 . The input applied to the tab  128  while maintaining a position of the grip feature  130  overcomes the retention force provided by detents at the interface between the upper and lower shells  120 ,  122  ( FIG. 3  identifies female portions  132  of the detents). Another grip feature  134  extending around at least a portion of the upper shell  120  may be provided to permit the housing  116 , and the system  100  if desired, to be moved as a unit, for example, with one hand as mentioned. 
     With continued reference to  FIG. 2 , the housing  116  includes or defines an aperture  135 . The aperture  135  extends through an upper wall of the upper shell  120  of the housing  116 . The aperture  135 , in the broadest sense, is the orifice through which the bone cement components are introduced to the chamber  112  prior to initiation of the operation cycle including the mixing, compression, and transferring phases.  FIGS. 4 and 5  show the chamber  112 , and more particularly a front chamber housing  164 , including or defining an inlet opening  136  in communication with the aperture  135  and the chamber  112 . The inlet opening  136  may be positioned directly beneath the aperture  135  such that the bone cement components directed through the aperture  135  further pass through the inlet opening  136  and into the chamber  112  under the influence of gravity. The chamber  112  is disposed within the housing  116 . 
     To facilitate effective introduction of the bone cement components through the aperture  135 , a funneling device  138  may be provided. The bone cement components typically include a liquid monomer and a powdered polymer. The funneling device  138  includes a widened opening opposite a narrowed opening defined by a stem  140  sized to be received within the aperture  135  of the housing  116 . Further, the funneling device  138  may include a flexible tether  142  coupling the funneling device  138  to the housing  116 . The flexible tether  142  may be retained through a slot in the upper shell  120  of the housing  116 , but other suitable joining means are contemplated. Among other advantages, the flexible tether  142  allows the funneling device  138  to be packaged as coupled to the housing  116  and further permits the system  100  including the funneling device  138  to be moved as a unit, for example with one hand. Known systems including a funnel require the funnel to be handled separately and require additional transfers across the sterile barrier of the surgical suite. The flexible tether  142  is coupled to the housing  116  with the funneling device  138  inverted in an initial configuration, as shown in  FIGS. 1 and 2 . During a step of the intuitive workflow, the user manipulates the funneling device  138  to position the stem  140  within the aperture  135 . This may be considered the first step of the workflow, as indicated by the indicia  144  on the funneling device  138  being the number “1.” In some implementations, the funneling device  138  may include a detent (not shown) disposed on the stem  140 . The detent is configured to releasably engage a complementary opening  143  defined within the housing  116  near the aperture  135 . The engagement of the detent provides an audible and/or tactile feedback to the user that the funneling device  138  is properly installed to receive the bone cement components. Thereafter, the user introduces the bone cement components into the funneling device  138  to be directed to the chamber  112 . 
     The user actuates an actuator  148 , for example a slider  150  movably coupled to the housing  116  and to be further described, to initiate the operational cycle. The actuator  148  may include indicia  152 , in this case the number “2,” corresponding to the second step of the intuitive workflow. 
     The operational cycle includes the mixing phase in which a mixing paddle  154  disposed within the chamber  112  mixes the bone cement components, and the compression and transferring phases in which a piston  156  disposed within the chamber  112  compresses and transfers the bone cement through the outlet port  108  to the delivery device  104 , respectively. Referring now to  FIGS. 4 and 5 , sectional elevation views of the mixing device  102  are shown with  FIG. 4  depicting the mixing device  102  during the mixing phase and  FIG. 5  depicting the mixing device  102  during the compression and transferring phase. 
     The mixing phase, in the broadest sense, occurs when the piston  156  is located in a first region  158  of the chamber  112  such that the bone cement components enclosed within the chamber  112  are at a first pressure, and transferring phase, in the broadest sense, occurs when the piston  156  is located in a second region  160  of the chamber  112  such that the bone cement components are compressed to a second pressure greater than the first pressure. In one example, the first pressure is at or below atmospheric pressure (e.g., at or near one atmosphere, substantially equal to ambient pressure, etc.), and the second pressure is greater than atmospheric pressure (e.g., four to seven atmospheres). The chamber  112  may be defined by or within the front chamber housing  164  (see  FIG. 18 ) coupled to a rear chamber housing  166  (see  FIG. 10 ). With concurrent reference to  FIG. 3 , the front chamber housing  164  may be cylindrical in shape and extend beyond the housing  116 . The front chamber housing  164  may include an interior face  168  at least partially defining the chamber  112 . The rear chamber housing  166  may be a cap-like feature complementary to the front chamber housing  164  and define a front face  170  at least partially defining the chamber  112  opposite the interior face  168  (see  FIG. 10 ). For convention and as illustrated in  FIGS. 4 and 5 , the front face  170  of the rear chamber housing  166  may define a first end  162  of the chamber  112 , and the interior face  168  of the front chamber housing  164  may define a second end  163  of the chamber  112 . 
     The first and second regions  158 ,  160  are represented schematically in  FIGS. 4 and 5 . The first region  158  of the chamber  112  may be defined in elevation between the first end  162  of the chamber  112  an end  172  of the inlet opening  136  nearest the interior face  168 . More particularly, the first region  158  may be defined between the first end  162  of the chamber  112  and a plane intersecting the end  172  of the inlet opening  136  and perpendicular to the longitudinal axis LA of the chamber  112 . In other words and to be explained further, when a face  174  of the piston  156  moving along the longitudinal axis LA has not yet reached the end  172  of the inlet opening  136  defining the boundary between the first and second regions  158 ,  160 , the face  174  is in the first region  158  and at least a portion of the inlet opening  136  is generally open to ambient and the chamber  112  is at least substantially at atmospheric pressure. The second region  160  may be defined between the end  172  of the inlet opening  136  and the interior face  168 . In other words, when the face  174  of the piston  156  moving along the longitudinal axis LA is in the second region  160 , the face  174  has passed the inlet opening  136 , a fluid-tight closure may be formed between the piston  156  and the housing  116  to seal the chamber  112  from the ambient. Thus, in operation, with the face  174  of the piston  156  in the first region  158  of the chamber  112  extending longitudinally between the first housing end  162  and the opening end  172 , the bone cement components are mixed at the first or atmospheric pressure with the mixing paddle  154  to make the bone cement mixture. Subsequently, the piston  156  is moved along the longitudinal axis LA to be located in the second region  160  extending longitudinally between the opening end  172  and the second housing end  163  to compress the bone cement mixture in the chamber  112  to the second pressure greater than the first or atmospheric pressure. The bone cement mixture may also be transferred to the delivery device  104  through the outlet port  108  in communication with the chamber  112 . Among other advantages to be readily appreciated, the piston  156  passing the inlet opening  136  to seal the chamber  112  during compression and transfer of the bone cement to the delivery device  104  reduces or eliminates the need for many high-pressure components required of existing systems. For example, existing systems may require an attachable lid, and the lid and the manner by which the lid is joined to the device must be designed to withstand the heightened pressures associated with the compression phase. The lid and its interface are often prone to acute failure. The lid and its interface may not be intuitive to users and consequently are prone to installation errors and resultant failures. The lid must be transferred to the sterile field separately from the mixer, which increases the risk of contamination of sterile surfaces. The lid may also be dropped on the floor, or may roll off the table onto the floor, rendering the mixing unit unusable. The piston  156  passing the inlet opening  136  to seal the chamber  112  eliminates the need for an attachable lid. Consequently, the self-sealing nature of the chamber  112  of the mixing device  102  reduces or eliminates the likelihood of inadvertent user exposure to the bone cement mixture under heightened pressures. 
     The mixing device  102  may include a sealing element (not identified) coupled to the piston  156  to provide a fluid-tight closure between the piston  156  and the housing  116 . Near the face  174  of the piston  156 , the piston  156  may include a recess  175 . The recess  175  may extend annularly around the piston  156 , and the sealing element, for example an O-ring gasket, is at least partially seated within the recess  175 . The sealing element interacts with the interior surface of the housing  116  to provide the fluid-tight closure between the piston  156  and the housing  116 . 
     The electromechanical operation of the mixing device  102  to impart rotation of the mixing paddle  154  during the mixing phase will now be described with reference to  FIGS. 4-9 . The mixing device  102  may be electrically powered by a battery pack  176  including a plurality of batteries shown in  FIGS. 4 and 5 . In one example, the battery pack  176  includes eight conventional double-A batteries; however, alternatives are contemplated such as lithium ion and/or other disposable or rechargeable batteries. While less convenient for the surgical suite, the mixing device  102  may also be adapted to be powered in a corded arrangement. The mixing device  102  further includes a motor  178  in communication with the battery pack  176 . Further, the mixing device  102  further includes a switch  180  in communication with the motor  178  and configured to be actuated between an activated state and a deactivated state. In one example, the switch  180  is a momentary microswitch internally biased to the deactivated state. This advantageously provides for returning the switch  180  to its original position to cease operation of the mixing device  102 , as necessary. In another example, the switch  180  is a non-momentary switch, for example, a toggle switch. Upon actuation of the switch  180  in manners to be explained in greater detail, the motor  178  is operated to provide a rotational output to an output shaft  182  of the motor  178 . It is contemplated that the motor  178  is optional, and the mixing device  102  may be a manual mixing device. In such an example, the piston may be akin to a plunger and mixing paddle on a shaft configured to receive an input from the user. The plunger may be within the first region  158  as the bone cement components are mixed with the mixing paddle  154  at atmospheric pressure, and the plunger may be moved, in response to an input from the user, to the second region  160  to compress the bone cement mixture in the chamber  112  to a pressure greater than atmospheric pressure. Alternatively, manual mixing may be performed with a mixing blade on a shaft configured to receive an axial and rotational input to the user, as disclosed in the aforementioned U.S. Pat. No. 6,547,432. Another non-motorized configuration may include a manually operated crank operating a geartrain that both rotates the mixing paddle  154  and advances the piston  156 . 
     The output shaft  182  is operably coupled to a geartrain  184  best shown in  FIGS. 7-9 . The geartrain  184  shown is a stacked spur configuration, but other suitable configurations are contemplated (e.g., planetary, helical spur, helical planetary, etc.). The geartrain  184  includes a pinion gear  186  coupled to the output shaft  182  of the motor  178 . A first spur gear  188  is operably coupled to the pinion gear  186 . The first spur gear  188  includes a first spur  190  having a larger outer diameter with the first spur  190  coupled to the pinion gear  186 , and a second spur  182  having a smaller outer diameter. A second spur gear  194  is operably coupled to the first spur gear  188 . The second spur gear  194  includes a first spur  196  having a larger outer diameter with the first spur  196  coupled to the second spur  182  of the first spur gear  188 , and a second spur  198  having a smaller outer diameter. A third spur gear  200  is operably coupled to the second spur gear  194 . The second spur gear  200  includes a first spur  202  having a larger outer diameter with the first spur  202  coupled to the second spur  198  of the first spur gear  194 , and a second spur  204  having a smaller outer diameter. The third spur gear  200 , and more particularly the first spur  202  of the third spur gear  200 , is operably coupled to an input spur  206  of the paddle drive gear  208 . The third spur gear  200  is also operably coupled to a fourth spur gear  210 . The fourth spur gear  210  includes a first spur  212  having a larger outer diameter with the first spur  212  coupled to the second spur  204  of the third spur gear  200 , and a second spur  214  having a smaller outer diameter coupled to a transfer gear  216  to be described.  FIGS. 6 and 7  collectively show the geartrain  184  being disposed within front and rear geartrain housings  218 ,  220  operably coupled to one another. Further, the rear chamber housing  166  is operably coupled to the front geartrain housing  218 . 
     In certain implementations, vibration and noise may be reduced by employing damping and/or vibration isolation between the motor  178  and/or geartrain  184 , and complementary components of the geartrain housing  218 . Damping may be achieved by manufacturing one or more gears from a reduced elastic modulus (i.e. more compliant) material, for example an elastomeric polyester such as Hytrel® produced by DuPont de Nemours, Inc. (Wilmington, Dela.). Isolation of vibration may be achieved by placing a compliant material, such as an elastomer or foam, between a vibrating component and adjacent components, for example between the motor  178  and adjacent portions of the geartrain housing  218  (see  FIG. 6 ) or between the geartrain housings and the mixer housings. Other suitable locations for damping or isolation include the first and second spur gears  188 ,  200 , which are rotating most quickly in the geartrain  184  and therefore responsible for the most noise. It is further contemplated that some compliance may be provided between the pinion gear  186  and the first spur gear  188  to further reduce noise as well as the sensitivity of alignment in the component stack. 
     With particular reference to  FIG. 9 , the mixing paddle  154  may be coupled to an end of an output shaft  222  of the paddle drive gear  208  that is coupled to the input spur  206 . The output shaft  222  includes longitudinally extending rails configured to couple with complementary features within a stem  224  of the mixing paddle  154  to rotationally fix the mixing paddle  154  to the paddle drive gear  208 . The mixing paddle  154  further includes a face portion  226  generally extending radially from the stem  224 . The face portion  226  is positioned adjacent and rotatable relative to the face  174  of the piston  156 , as appreciated from  FIGS. 6 and 7 . A mixing feature  228  is coupled to the face portion  226 . The mixing feature  228  extends longitudinally forward of the face portion  226  and includes at least one leg  230  for agitating the mixture components during rotation of the mixing paddle  154 .  FIGS. 7 and 9  show two of the legs  230  coupled to one another with a head  232  to form a generally U-shaped mixing feature  228 . Each of the legs  230  and the head  232  may be plate-like in construction with the head  232  angled inwardly relative to the legs  230  to impart collapsing or buckling of the mixing feature  228  relative to the face portion  226  during the compression and transferring phase in a manner to be described in greater detail. Other configurations of the mixing paddle  154  configurations are also contemplated. 
     In operation, the switch  180  is moved from the deactivated state to the activated state. The motor  178  draws power from the battery pack  176  or other power source and is operated to supply torque to the geartrain  184 . This may be considered the initiation of the operational cycle, and more particularly the mixing phase of the operational cycle. According to known speed versus torque characteristics associated with gearing, the torque is transferred from the pinion gear  186  through each of the first, second, and third spur gears  188 ,  194 ,  200 , and through the paddle drive gear  208  to the mixing paddle  154 . 
     The step of rotating the mixing paddle  154  effectuates mixing of the bone cement components within the chamber  112 . Referring again to  FIG. 4 , the mixing paddle  154  may be rotated while the piston  156  is positioned within the first region  158  of the chamber  112 . Again, the face  174  of the piston  156  is located between the first end  162  of the chamber  112  and the boundary separating the first and second regions  158 ,  160 , such that the mixing paddle  154  mixes the bone cement components with the chamber  112  at least substantially at atmospheric pressure. It is appreciated that a door  234  of the slider  150  is positioned to cover the inlet opening  136  during the operational cycle including the mixing phase to prevent egress of debris from the mixing device  102 ; however, the door  234  may not result in more than minimal pressurization of the chamber  112  during movement of the piston  156 . The door  234  may be positioned between the aperture  135  defined by the housing  116  and the inlet opening  136  defined by the chamber  112  when the actuator  148  is in the second position. At least in part because the bone cement components are mixed in the chamber  112  at atmospheric pressure, a sealing element  236  disposed within the outlet port  108  of the mixing device  102  prevents egress or premature transferring of the bone cement mixture from the mixing device  102  to the delivery device  104 . As a result, less complex and more cost-effective valves may be utilized to form the sealing element  236 . 
     As further appreciated from  FIG. 4 , the legs  230  of mixing paddle  154  extend forward from the piston  156  such that the head  232  of the mixing paddle  154  is positioned near or adjacent the interior face  168  of the front chamber housing  164 . The arrangement results in the mixing paddle  154  being capable of accessing substantially an entirety of the chamber  112  to prevent any portion of the bone cement components from being insufficiently mixed or agitated. In other words, the legs  230  may effectively dislodge any of the bone cement components adhering to a sidewall at least partially defining the chamber  112 , and the head  232  may effectively dislodge any of the bone cement components adhering to the interior face  168  at least partially defining the chamber  112 . As mentioned and as to be further explained, however, the piston  156  moves from the first region  158  to the second region  160  for the compression and transferring phase. As a result, the mixing paddle  154  must accommodate such longitudinal movement of the piston  156  within the chamber  112 . To that end, the mixing paddle  154  is configured to collapse or buckle while the piston  156  is compressing the bone cement mixture in the chamber  112 . The piston  156  and the mixing paddle  154  move along the longitudinal axis LA until the head  232  of the mixing paddle  154  encounters the interior face  168  of the front chamber housing  164 . Owing to the inwardly angled orientation of the head  232  relative to the legs  230 , the continued force provided by the piston  156  results in the legs  230  deforming at an interface  238  between the legs  230  and the face portion  226  (see  FIGS. 7 and 8 ). The deformation may be considered buckling at pivot points induced by the interface  238 . An axial profile of the face portion  226  relative to the face  174  of the piston  156  is shaped to accommodate the legs  230  and the head  232  such that when nearly or fully collapsed, the mixing feature  228  is substantially flat and in abutment or adjacent with the face  174  of the piston  156 . Among other advantages, the arrangement allows the piston  156  to longitudinally move across nearly an entirety of the chamber  112  to compress and transfer the bone cement mixture through the outlet port  108  positioned near the second end  163  of the chamber  112  (see  FIG. 5 ). 
     The electromechanical operation of the mixing device  102  to impart longitudinal movement of the piston  156  (and the mixing paddle  154 ) will now be described with reference to  FIGS. 4, 5, 8, 9 and 10 . As mentioned, the fourth spur gear  210  includes the second spur  214  coupled to the transfer gear  216 .  FIGS. 7, 8 and 10  best show the transfer gear  216  including a transfer spur  240  and a threaded shaft  242  extending from the transfer spur  240 . The transfer spur  240  is coupled to the second spur  214  of the fourth spur gear  210  such that rotation of the geartrain  184  including the fourth spur gear  210  imparts rotation to the transfer gear  216 . The transfer gear  216 , and more particularly the threaded shaft  242 , defines a lumen  246  extending through the transfer gear  216 , as best shown in  FIG. 10 . At least one rail feature  248  is disposed within the lumen  246  and oriented along a length of the lumen  246 .  FIG. 10  shows two rail features  248  positioned diametrically opposite one another. The lumen  246  is further defined by a front face (not identified) of the transfer spur  240  at the rear end of the lumen  246 . A borehole (not shown) having a smaller diameter than the lumen  246  extends through the transfer spur  240  with the borehole sized to permit the output shaft  222  of the paddle drive gear  208  to be positioned through the transfer gear  216  as shown in  FIGS. 4 and 5  and further generally appreciated from viewing  FIGS. 7 and 9  in combination. 
     With particular reference to  FIGS. 8 and 10 , a translating shaft  244  is movably disposed within the lumen  246  of the transfer gear  216 . The translating shaft  244  includes an outer diameter smaller than the inner diameter of the lumen  246  to be slidably movable within the lumen  246 . Further, the translating shaft  244  includes threads  250  disposed about an outer surface with function to be described. The threads  250  may define at least one slot  252  extending longitudinally between opposing ends  245 ,  247  of the translating shaft  244 .  FIG. 10  identifies one slot  252 , but it is appreciated there is another slot diametrically opposite with the slots  252  configured to engage the rail features  248  of the transfer gear  216 . The engagement of the rail features  248  and the slots  252  prevents relative rotation while permitting translation between the translating shaft  244  and the transfer gear  216 . The translating shaft  244  may also define a lumen  254  extending between the opposing ends  245 ,  247  with the lumen  254  sized to permit the output shaft  222  of the paddle drive gear  208  to be positioned through the translating shaft  244  as shown in  FIGS. 4 and 5  and further generally appreciated from viewing  FIGS. 7 and 9  in combination. Thus, the paddle drive gear  208 , the translating shaft  244 , and the transfer gear  216  may be in a coaxial arrangement. 
     A biasing element (not shown), for example a coil spring, is disposed within the lumen  246  of the transfer gear  216 . The biasing element includes an end positioned in abutment with the transfer spur  240 , and another end positioned in abutment with the rear end  247  of the translating shaft  244 . The biasing element urges the front end  245  opposite the rear end  247  of the translating shaft  244  towards and into contact with the rear chamber housing  166 . With continued reference to  FIG. 10 , the rear chamber housing  166  defines an aperture  256  with internal threads  258 . The aperture  256  may be coaxially aligned with the paddle drive gear  208 , the translating shaft  244 , and/or the transfer gear  216 . The aperture  256  is sized to permit the output shaft  222  of the paddle drive gear  208  to be positioned through the rear chamber housing  166 , and further sized such that the internal threads  258  are configured to threadably engage the threads  250  of the translating shaft  244 . It is appreciated that the rear chamber housing  166  is a stationary component of the mixing device  102  such that threadable engagement between the internal threads  258  and the threads  250  of the translating shaft  244  imparts translational movement of the translating shaft  244  relative to the rear chamber housing  166  (and relative to the transfer gear  216 ). 
     The rear chamber housing  166  may define a bore  260  in communication with the aperture  256  and positioned on a side of the rear chamber housing  166  opposite the translating shaft  244 . The bore  260  is sized to initially receive at least a portion of a push cap  262 .  FIG. 10  shows the push cap  262  as a ring-like structure including an outer portion  264  sized to be received within the bore  260  and positioned adjacent a front face  266  of the bore  260  adjacent the internal threads  258 . The push cap  262  includes an aperture  268  sized to permit the output shaft  222  of the paddle drive gear  208  to be positioned through the push cap  262 . The outer portion  264  of the push cap  262  opposite that engaging the front face  266  is configured to engage an annular slot (not shown) on a rear side of the piston  156 . 
     In operation, the switch  180  is moved from the deactivated state to the activated state. The motor  178  draws power from the battery pack  176  and is operated to supply torque to the geartrain  184  to activate the mixing paddle  154 . As previously described, this may be considered the initiation of the mixing phase of the operational cycle, and torque is transferred from the pinion gear  186  through each of the first, second, and third spur gears  188 ,  194 ,  200 , and through the paddle drive gear  208  to the mixing paddle  154  in the geartrain  184  shown. The mixing paddle  154  begins rotating immediately. Simultaneously, torque is transferred through each of the first, second, and third spur gears  188 ,  194 ,  200 , and from the fourth spur gear  210  to the transfer gear  216 . The transfer gear  216  beings rotating immediately, albeit at a different speed than that of the mixing paddle  154 . Owing to the rotational constraint provided by the rail features  248  of the transfer gear  216  engaging the slots  252  of the translating shaft  244 , the translating shaft  244  rotates with the transfer gear  216 . Meanwhile, the biasing element urges the front end  245  into contact with the rear chamber housing  166  such that the threads  250  of the translating shaft  244  being to engage the internal threads  258  of the rear chamber housing  166 . The threadable engagement of the threads  250 ,  258  results in translating movement of the translating shaft  244  relative to the transfer gear  216 . In other words, the translating shaft  244  may be simultaneously rotating and translating. 
     As mentioned, at least a portion of the push cap  262  is initially situated within the bore  260  adjacent the front face  266 . Further,  FIG. 10  shows the aperture  256  of the rear chamber housing  166  having a depth or length defined between the front face  266  opposite a rear face (not shown). The depth of the aperture  256  is the distance the translating shaft  244  is required to travel before the front end  245  of the translating shaft  244  engages an inner portion  270  of the push cap  262 , and consequently moves the push cap  262  to move the piston  156 . This distance, in combination with the thread pitch of the threads  250 ,  258 , is specifically tailored to provide a time lag between the mixing phase of the operational cycle and the compression and transferring phase of the operational cycle. In other words, during the time lag that the translating shaft  244  is moving through the depth of the aperture  256 , the mixing paddle  154  is rotating and mixing the bone cement components in the manner previously described. In one example, the time lag is thirty seconds; however, other timeframes are contemplated. Once the translating shaft  244  urges the push cap  262  into the piston  156 , a continued torque provided through the geartrain  184  causes the piston  156  to move along the longitudinal axis. This may be considered a transition phase of the operational cycle, as the piston  156  is moving but the face  174  of the piston  156  has yet to enter the second region  160  of the chamber  112  (e.g., the face  174  of the piston  156  may have only partially passed the inlet opening  136 ). Thus, the chamber  112  may remain generally at atmospheric pressure during the transition phase. It is further appreciated that, at least for a brief period, the piston  156  may be moving along the longitudinal axis LA while the mixing paddle  154  is fully extended and rotating (as the head  232  of the mixing paddle  154  has yet to contact the interior face  168  and begun to collapse or buckle as previously described). 
     Relative to  FIG. 4 ,  FIG. 5  shows the translating shaft  244  moved along the longitudinal axis LA and spaced apart from the rear chamber housing  166  with the push cap  262  and the piston  156  moving in a corresponding manner (the mixing paddle  154  is removed for clarity). As previously mentioned, the face  174  of the piston  156  passes the inlet opening  136 , and more particularly the end  172  of the inlet opening  136 , such that a fluid-tight closure is formed between the piston  156  and the housing  116  to seal the chamber  112  from the ambient.  FIG. 5  shows the face  174  of the piston  156  in the second region  160 . The piston  156  compresses the bone cement mixture in the chamber  112  to a pressure greater than atmospheric pressure, and the bone cement may also be transferred to the delivery device  104  through the outlet port  108  in communication with the chamber  112 . From the above description, it is readily appreciated that through a single actuation of the switch  180 , the mixing device  102  advantageously performs the mixing phase and the time-lagged compression and transferring phase in a manner that mixes the bone cement components at atmospheric pressure and compresses and transfers the bone cement mixture in a self-sealing, closed system. 
     Moreover, the mixing device  102  is further configured to automatically terminate the operational cycle after a predetermined period that is based on the end of the mixing, compression and transferring phases. Referring again to  FIGS. 4 and 5  and with further reference to  FIGS. 11-14 , the user actuates the actuator  148 , for example the slider  150  movably coupled to the housing  116  to initiate the operational cycle. The slider  150  and the switch  180  are complementarily arranged such that movement of the slider  150  from a first position (see  FIG. 1 ) to a second position (see  FIGS. 4, 5, 11, 12 and 17 ), moves the switch  180  from the deactivated state to the activated state to initiate the operational cycle. In one implementation, the switch  180  may be biased to the deactivated state; and with the slider  150  in the second position, the switch  180  is maintained in the activated state against the bias. When the piston  156  is within the second region  160 , the actuator  148  is mechanically disengaged from the switch  180  to permit the biased return of the switch  180  from the activated state to the deactivated state. In one example and in a manner to be explained in greater detail, a stop nut  272  is configured to disengage the slider  150  from the switch  180 , thereby permitting the bias of the switch  180  to return it to the deactivated state to terminate the operational cycle. In another example, a structure coupled to the piston  156  such as a flange or arm, may disengage the slider  150  from the switch  180 , thereby permitting the bias of the switch  180  to return it to the deactivated state. In another implementation to be described in greater detail, the stop nut  272 ′ is configured to engage a second switch  181 ′ to return the mixing device  102  to the deactivated state to terminate the operational cycle. In still another example, an action may occur such as a cable being severed when the piston  156  is appropriately within the second region  160  with the action resulting in the bias of the switch  180  to return it to the deactivated state. Alternatively, it is contemplated that the switch  180  is a non-momentary switch, as mentioned, and when the piston  156  is within the second region  160 , the switch  180  is automatically and mechanically moved to the deactivated state to terminate the operational cycle and deactivate the motor  178 . 
       FIG. 13  is a perspective view of the slider  150  forming the actuator  148 . The slider  150  includes a slider body  274  including a control surface  276  opposite an underside  278 . The control surface  276  may be considered the surface configured to receive the user input, for example to move the slider  150  from the first position to the second position. The slider  150  also includes a first arm  280  and a second arm  282  separate from the first arm  280 . The first and second arms  280 ,  282  extend from or are coupled to the underside  278 . In particular,  FIGS. 11-13  show the slider body  274  of the slider  150  including a projection  284  extending downwardly from the underside  278  with each of the first and second arms  280 ,  282  extending generally laterally from the projection  284 . The projection  284  serves to space apart the first and second arms  280 ,  282  from the underside  278  of the slider body  274  such that the first and second arms  280 ,  282  are disposed within the interior  124  of the housing  116  while the slider body  274  including the control surface  276  are external to the housing  116  for user actuation. 
     The door  234  is coupled to the first arm  280 . The door  234 , as previously mentioned, is sized and contoured to cover the inlet opening  136  of the chamber  112 , more particularly, when the slider  150  is in the second position. The door  234  covering the inlet opening  136  provides a closure that is not pressurized and may not be considered fluid-tight, yet prevents egress of the bone cement components from the chamber  112  during the mixing phase of the operational cycle. An engagement member  286  is coupled to the second arm  282  and includes a stop feature  288  and a ramping surface  290 .  FIG. 13  shows the stop feature  288  as a flange extending laterally from the engagement member  286 . As the slider  150  is moved from the first position to the second position, the stop feature  288  of the engagement member  286  engages the switch  180  to move the switch  180  from the deactivated state to the activated state. The stop feature  288  further maintains the switch  180  in the activated state against the internal bias of the switch  180  until disengaged from the switch  180  by the stop nut  272  in a manner to be further explained.  FIGS. 11, 12 and 15  show the slider  150  in the second position such that the switch  180  is engaged and in the activated (several supporting structures of  FIGS. 11, 12, 15 and 16  are removed for clarity to show relative positions between the components shown). 
       FIG. 14  shows the stop nut  272  including a nut portion  292  and a flange portion  294 . The nut portion  292  is ringed-shaped in construction and includes a lumen  296  and internal threads  298  sized and shaped to threadably engage the threaded shaft  242  of the transfer gear  216  (see  FIGS. 4, 5, 7 and 10-12 ). The flange portion  294  includes at least one flange  300  extending generally radially outwardly from an outer surface of the nut portion  292 .  FIG. 14  shows two of the flanges  300  separated by a slot, but a singular flange is also contemplated. Each of the flanges  300  include a lateral surface  302  configured to engage surfaces defining a slot  304  in the upper shell  120  of the housing  116 . With reference to  FIG. 6 , one of the flanges  300  is shown disposed within the slot  304 . As a result, rotation of the stop nut  272  relative to the housing  116  is prevented, and thus rotation of the transfer gear  216  results in translation of the stop nut  272  along the threaded shaft  242  of the transfer gear  216 . 
     In operation, the user provides the input to the actuator  148 , for example at the second step of the intuitive workflow. The slider  150  is moved from the first position to the second position. The door  234  coupled to the first arm  280  is moved to cover the inlet opening  136 , and the stop feature  288  coupled to the second arm  282  is moved to engage the switch  180  and move the switch  180  from the deactivated state to the activated state. Thus, the single action of providing the input to the actuator  148 , simultaneously provides a barrier over the inlet opening  136  and initiates the operational cycle. At this point, the mixing device  102  may be as shown in  FIG. 4 , and the stop nut  272  is positioned on the threaded shaft  242  near or adjacent the transfer spur  240 . The internal threads  298  of the nut portion  292  are engaging the threads of the threaded shaft  242 . With the switch  180  in the activated state, the motor  178  supplies the torque to the geartrain  184 , namely through each of the first, second, and third spur gears  188 ,  194 ,  200 , and from the fourth spur gear  210  to the transfer gear  216 . As transfer gear  216  rotates and with the stop nut  272  prevented from rotation (owing to the lateral surfaces  302  of the flange portion  294  disposed within the slot  304  of the housing), the stop nut  272  translates along the threaded shaft  242 . With reference to  FIG. 12 , the flange portion  294  of the stop nut  272  eventually encounters the engagement member  286 , and more particularly the ramping surface  290  of the engagement member  286 . The second arm  282  of the slider  150  is configured to flex, and with further translation of the stop nut  272  along the threaded shaft  242 , the flange portion  294  engages the ramping surface  290  to upwardly flex the second arm  282  and the engagement member  286  coupled to the second arm  282 . The extent of the flexion is such that the stop feature  288  disengages from the switch  180  (i.e., moved upwardly out of interference), and the switch  180  is permitted to automatically return to the deactivated state under its internal bias. With the switch  180  in the deactivated state, the motor  178  ceases operation and the movement of the piston  156  and the rotation of the mixing paddle  154  is ceased, which may be considered the end of the operational cycle. It should be appreciated that a single component that may be molded and inexpensive, facilitates the barrier over the inlet opening  136 , initiating the operational cycle, and ceasing the operational cycle. 
     Another implementation by which the mixing device  102  automatically terminates the operational cycle after a predetermined period is described with reference to  FIGS. 15 and 16 .  FIG. 15  shows the actuator  148  in the second position, i.e., after receiving the input, to contact the switch (hereinafter first switch  180 ′) to initiate the operational cycle. The first switch  180 ′ is a momentary switch internally biased to the deactivated state. As the actuator  148  is moved from the first position to the second position, the second arm  282  translates down a channel  221  within the front and/or rear geartrain housings  218 ,  220  and encounters a ramped surface  223  defining the channel  221 . The second arm  282  may deflect laterally (to the left in  FIG. 15 ) to contact the first switch  180 ′. The first switch  180 ′ is moved from the deactivated state to the activated state by the mechanical force from the engagement member  286 ′ of the second arm  282 . The second arm  282  may be constrained from resiliently flexing to its original position by the ramped surface  223  of the rear geartrain housings  218 ,  220 . The mixing device  102  initiates the operational cycle as previously described. 
     With the switch  180 ′ in the activated state, the motor  178  supplies the torque to the geartrain  184 , namely through each of the first, second, and third spur gears  188 ,  194 ,  200 , and from the fourth spur gear  210  to the transfer gear  216 .  FIG. 16  shows the stop nut  272 ′ threadably engaged with the transfer gear  216  with the flange portion  294 ′ extending laterally from the same. The stop nut  272 ′ is prevented from rotation as the stop nut  272 ′ translates along the threaded shaft  242 . The mixing device  102  includes a second switch  181 ′ separate from the first switch  180 ′. The second switch  181 ′ is coupled to the housing  116  so as to be aligned with the flange portion  294 ′ of the stop nut  272 ′. The second switch  181 ′ may be a non-momentary switch initially in the activated state. Once the stop nut  272 ′ translates along the threaded shaft  242 , the flange portion  294 ′ of the stop nut  272 ′ eventually encounters the second switch  181 ′ to move the second switch  181 ′ from the activated state to the deactivated state. With the switch  181 ′ in the deactivated state (even with the first switch  180 ′ remaining in the activated state), the motor  178  ceases operation and the movement of the piston  156  and the rotation of the mixing paddle  154  is ceased, which may be considered the end of the operational cycle. The elapsed time of the operational cycle may be specifically tuned as desired. Based on distance the stop nut  272  must travel along the threaded shaft  242  to encounter the second switch  181 ′. 
     The first and second switches  180 ′,  181 ′ may be wired in series between the battery  176  and the motor  178 . Thus, with either the first switch  180 ′ or the second switch  181 ′ in the deactivated stated, the motor  178  is inoperable. In the above example, the first switch  180 ′ was initially in the deactivated state, and the second switch  181 ′ was initially in the activated state. Once the input from the user moves the actuator  148 , both the first and second switch  180 ′,  181 ′ are in the activated state, and the motor  178  is operational. Once the stop nut  272 ′ eventually encounters the second switch  181 ′, the second switch  181 ′ is in the deactivated state, and the first switch is in the activated state; the motor  178  is again inoperable. The motor  178  ceases operation and the movement of the piston  156  and the rotation of the mixing paddle  154  is ceased, which may be considered the end of the operational cycle. 
     As mentioned, the delivery device  104  is removably coupled to the mixing device  102  to establish communication between the inlet and outlet ports  106 ,  108  for transferring the bone cement mixture, and the release assembly  110  facilitates the removable connection between the mixing device  102  and the delivery device  104 .  FIGS. 1 and 2  show the release assembly  110  in an initial or locked position. The release assembly  110  is configured to be moved from the initial or locked position to an unlocked position to permit decoupling of the delivery device  104  from the mixing device  102 .  FIGS. 17 and 19A  show the release assembly  110  in the unlocked position. Referring now to  FIGS. 17-20  the housing  116  includes a transfer conduit  306  in communication with the outlet port  108 . As best shown in  FIG. 18 , the transfer conduit  306  may include a boss extending outwardly from the front chamber housing  164 . A first end  308  of the transfer conduit  306  may include an interior wall  310  defining the outlet port  108 . Alternatively, the interior wall  310  may be associated with the sidewall of the front chamber housing  164 . A length of the transfer conduit  306  is defined between the first end  308  opposite a second end  309  with the length sized to receive the sealing element  236 , as shown in  FIG. 19A . In particular, the sealing element  236  may be bucket-shaped with a slit or self-closing orifice (not identified) within its base  312  with the base  312  positioned adjacent or in abutment with the interior wall  310  of the transfer conduit  306 . The slit or self-closing orifice is configured to open when subjected to sufficiently high pressures from the bone cement mixture within the chamber  112 , in particular during the compression and transfer phase of the operational cycle. During the mixing phase of the operational cycle performed at or near atmospheric pressure, by contrast, the slit or self-closing orifice is capable of preventing premature egress of the bone cement components or mixture. The sealing element  236  may include at least one sidewall  314  extending from the base  312  and terminating near the second end  309  of the transfer conduit  306 . An inner diameter defined at least partially by the sidewall  314  is sized to removably receive a complementary male component of the delivery device  104  to provide the sealed fluid communication between the outlet port  108  of the mixing device  102  and the inlet port  106  of the delivery device  104 . 
     With continued reference to  FIGS. 18 and 19A , the transfer conduit  306  may include first coupling feature  316  and/or second coupling feature  318  configured to selectively engage complementary features of the release assembly  110  to be described to facilitate the desired movement and operation of the release assembly  110 . The first coupling feature  316  may be a rib  320  extending along an outer surface of the transfer conduit  306 , in particular extending between the first and second ends  308 ,  309 .  FIGS. 18 and 19A , when viewed on combination, show two of the ribs  320  positioned diametrically opposite one another. The first coupling feature  316  is configured to provide interference to limit range of motion of the release assembly  110  relative to the transfer conduit  306  in a manner to be described. In one example the maximum range of motion is ninety degrees of counterclockwise rotation, for example as shown in  FIG. 17  relative to  FIG. 1 . The second coupling feature  318  may include a rib  322  extending along the outer surface of the transfer conduit  306 , in particular subtending an arc at or near the second end  309 .  FIGS. 18 and 19A , show two of the ribs  322  positioned diametrically opposite one another. The ribs  322  are configured to axially retain the release assembly  110  on the transfer conduit  306 . Moreover, the transfer conduit  306  may include at least one defeatable feature  324  (one identified as hidden but not shown in  FIG. 19A ), for example a protrusion or bump-like structure extending outwardly from the outer surface of the transfer conduit  306 . The defeatable feature  324  may be positioned adjacent (behind) one or both of the ribs  322  forming the second coupling feature  318 . The defeatable feature  324  is configured to maintain the release assembly  110  in the locked position to avoid inadvertent unlocking of the delivery device  104  from the mixing device  102 . Once an input from the user is provided to the release assembly  110  with suitable force to overcome the interference engagement of the defeatable feature  324 , the release assembly  110  may be moved to the unlocked position. 
     The release assembly  110  will be described with reference to  FIGS. 19A and 20 . The release assembly  110  includes a head portion  326  and a body portion  328  coupled to the head portion  326 . The head portion  326  may be generally tubular in form and include at least one sidewall  330  defining a lumen  332 . An inner diameter of the lumen  332  is slightly greater than an outer diameter of the transfer conduit  306  such that the head portion  326  receives the transfer conduit  306  in the lumen  332 , as shown in  FIG. 19A . The head portion  326  includes at least one projection  334  extending inwardly from the sidewall  330  and positioned within the lumen  332 . The at least one projection  334  may be two projections (one shown) positioned diametrically opposite to one another. The projections  334  are configured to cooperate with the first coupling feature  316 , namely the ribs  320 , to limit the range of motion of the release assembly  110 .  FIG. 19A  shows one of the projections  334  engaging one of the ribs  320  with the release assembly  110  in the unlocked configuration such that the release assembly  110  has a maximum range of motion of counterclockwise rotation of ninety degrees relative to the locked configuration. Further, the projections  334  selectively engage the second coupling feature  318 , namely the ribs  322 , to prevent axial removal of the release assembly  110  from the transfer conduit  306 . More particularly, during assembly of the mixing device  102 , prior to the coupling of the upper shell  120  of the housing  116  with the lower shell  122  of the housing  116 , the projections  334  are directed through gaps defined between the ribs  322  forming the second coupling feature  318 . At this time, the release assembly  110  is in an exaggerated clockwise orientation relative to the locked position. The release assembly  110  is rotated counterclockwise such that the projections  334  assume a position behind the ribs  322 , and the upper shell  120  of the housing  116  with the lower shell  122  of the housing  116 . The interference between the body portion  328  of the release assembly  110  and the upper shell  120  of the housing  116  prevents clockwise rotation of the release assembly  110  in which the projections  334  may again become aligned with the gaps (thereby permitting axial removal of the release assembly  110 ). With the body portion  328  of the release assembly  110  supported on a recess  336  defined within the upper shell of the housing  116  (see  FIG. 17 ), the release assembly  110  may be considered in the locked position. 
     Another implementation of the transfer conduit  306 ′ is shown in  FIG. 19B . The transfer conduit  306 ′ includes a boss  311  extending from the interior wall  310 ′. The boss  311  may be coaxially disposed within the head portion  326 ′. The boss  311  includes the sidewall  314 ′ defining a lumen in communication with the chamber  112  of the mixing device  102 . The annular space between the boss  311  and the head portion  326 ′ may be sized to accommodate the sealing element (not shown) that is coupled to the delivery device  104  in the present implementation. The head portion  326 ′ may include the second coupling feature  318 ′, in particular a rib  321  extending along an inner surface of the transfer conduit  306 ′. The rib  321  may be in a helical arrangement to define a groove  323  that is helical in shape. The groove  323  provides a female thread that is configured to threadably engage a male thread (not shown) disposed on the delivery device  104 . More particularly, as the release assembly  110  is rotated from the unlocked position the locked position, for example, during assembly and packaging the system  100 , the groove  323  rotates so as to draw the delivery device  104  towards the mixing device  102 , thereby ensuring sealing engagement between the two. The sealing engagement further avoids inadvertent unlocking of the delivery device  104  from the mixing device  102 . As the release assembly  110  is rotated from the locked position to the unlocked position, for example, prior to deployment of the delivery device  104 , the groove  323  rotates so as to move the delivery device  104  away from the mixing device  102 . 
     The body portion  328  may be an elongate structure extending from the head portion  326 .  FIG. 20  shows the body portion  328  including two legs  338  forming a generally right angle. One of the legs  338  includes a control surface  340  configured to receive the input from the user. One of the legs  338  may also include indicia  342 , in this case the number “3,” which may corresponding to the third step of the intuitive workflow. The third step of the workflow occurs after completion of the second step of the intuitive workflow, namely completion of the operational cycle of the mixing device  102 , including the transferring phase in which the bone cement mixture is transferred to the delivery device  104 . Once it is desired to decouple the delivery device  104  from the mixing device  102 , the user provides an input to the control surface  340  to move the release assembly  110  from the locked position to the unlocked position. In particular, the release assembly  110  is rotated counterclockwise relative to the transfer conduit  306 , during which the projections  334  encounter the defeatable features  324 . Further input is provided with a suitable force to overcome the interference engagement of the defeatable feature  324 , and the release assembly  110  is moved to the unlocked position shown in  FIGS. 17, 19A and 19B . 
       FIG. 20 , viewed in combination with  FIG. 1 , generally shows the release assembly  110  in the locked position. The head portion  326  of the release assembly  110  includes a lip  344  extending axially outwardly and subtending an arc such that a void is defined between two edges  346  of the lip  344 . The void may be sized to be at least equal to a width of the complementary coupling feature of the delivery device  104  (e.g., a boss extending from the housing  118  and at least partially defining the inlet port  106 ). The lip  344  and the head portion  326  define a groove  348  at least substantially extending circumferentially between the edges  346  of the lip  344 . The groove  348  include a first groove portion  350  and second groove portions  352  (one shown) disposed on each side on the first groove portion  350 . The first groove portion  350  is wider than the second groove portions  352 . The second groove portions  352  are sized and configured to retain the complementary coupling feature of the delivery device  104  (e.g., diametrically opposed tabs extending from the boss). The tabs on the delivery device  104  may be positioned at the six and twelve o&#39;clock positions when the delivery device  104  is coupled with the release assembly  110  such that the delivery device  104  may not be decoupled axially or moved radially through the void. 
     With the release assembly  110  in the unlocked position, the first groove portion  350  is in registration with one of the tabs on the delivery device  104 , and the void is in registration with another one of the tabs of the delivery device  104 . The relatively greater width of the first groove portion  350  permits some axial movement of the delivery device  104  relative to the release assembly  110  with the first groove portion  350  positioned at the six o&#39;clock position (see  FIG. 19A ). In combination, the void is positioned at the twelve o&#39;clock position and permits an upward manipulation of the delivery device  104  relative to the release assembly  110  to decouple the delivery device  104  from the release assembly  110  and the mixing device  102 . Another input may be provided to the control surface  115  of the cradle  114  to permit removal of the housing  118  of the delivery device  104  from the cradle  114 . 
     The mixing and delivery system  100  provides several advantages in the surgical suite. First, the mixing device  102  and the delivery device  104  may be efficiently packaged. Referring now to  FIGS. 19 and 20 , a kit is shown including the mixing device  102  and the delivery device  104 . The kit may further include packaging, for example, a blister pack  354  having a base  356  and a cover  358 . The base  356  may be a thermoformed plastic generally contoured to the mixing and delivery system  100 , and the cover  358  may be a peel away film coupled to the base  356  with adhesive. The space-conscious manner in which the mixing device  102  and the delivery device  104  are disposed within the base  356  of the blister pack  354  may accommodate including the bone cement components (i.e. the liquid monomer  360  (see  FIG. 25 ) and the powdered polymer  362 ) conveniently within the blister pack  354 . The entire contents of the blister pack  354  may be in a sterile state before the blister pack is opened. As such, the surgical technician need only present the blister pack  354  across the sterile barrier of the surgical suite without needing to separately retrieve, for example, each of the mixing device  102 , the delivery device  104 , the liquid monomer  360  and the powered polymer  362 . Alternatively, the blister pack  354  may include a packaging insert, for example a thermoformed tray, to protect the cover  358  from damage due to contact with the mixing and delivery system  100 . This packaging insert may include features to hold the liquid monomer  360  and powdered polymer  362 , allowing them to be transferred to the sterile field in one step. Furthermore, the mixing and delivery device  100 , liquid monomer  360 , and powdered polymer  362  may be packaged in an inner blister tray, covered with a tray insert, all of which can be transferred to the sterile field in one step. Fewer items being presented across the sterile barrier improves efficiency and lessens likelihood of contamination of the sterile field. In another example, the liquid monomer  360  and powdered polymer  362  may be coupled directly to the mixing device such that they can be removed from the packaging with the rest of the mixing and delivery device  100  as a single unit. In another example, the powdered polymer  362  may be packaged in the chamber  112 . This arrangement would eliminate the steps of transferring the powdered polymer  362  to the sterile field and introducing the powder through the funneling device  138 . In addition, the liquid monomer  360  may be packaged in a way that allows it to interface with the chamber  112  directly (e.g. a syringe, foil pouch, or dispensing device), thus eliminating the need for a funneling device. 
     Second, as previously mentioned, the side-by-side arrangement of the mixing device  102  and the delivery device  104  permits the mixing device  102  and the delivery device  104  to be compactly packaged in the coupled configuration before deployment in the surgical suite. Referring again to  FIG. 1 , the mixing device  102  includes the longitudinal axis LA M  of the chamber  112  previously described with reference to  FIGS. 4 and 5 . Further, the delivery device  104  includes a longitudinal axis LA D . The longitudinal axis LA D  of the delivery device  104  may generally be defined between ends of the housing  118  of the delivery device  104  and/or coaxial with the chamber of the delivery device  104 . As generally appreciated from  FIG. 1 , with the delivery device  104  coupled to the mixing device  102 , the respective longitudinal axes LA D , LA M  are parallel. The parallel arrangement of the respective longitudinal axes LA D , LA M  provide for the efficient packaging previously mentioned. To facilitate the parallel arrangement, the outlet port  108  defined by the transfer conduit  306  (and the inlet port  106  of the delivery device  104 ) is arranged perpendicular to each of the respective longitudinal axes LA D , LA M . In other words, the bone cement mixture being moved within the chamber  112  initially along the longitudinal axis LA M  is generally directed sideways to be directed through the outlet port  108  and into the inlet port  106  of the delivery device  104 . Thereafter, the bone cement mixture may be generally directed sideways to be moved within the chamber of the delivery device  104  along the longitudinal axis LA D . Moreover, with the delivery device  104  coupled to the mixing device  102 , the respective longitudinal axes LA D , LA M  are coplanar on a plane that is substantially horizontal to effectuate the side-by-side arrangement previously mentioned. The parallel and side-by-side arrangement permits the lengths of the respective housings  116 ,  118  to be generally equal in the coupled configuration (when viewed in plan). In other words, there are few, if any, structures of the mixing device  102  and the delivery device  104  extend beyond one another, thereby minimizing requiring unnecessary accommodations in the corresponding packaging. 
       FIG. 22  shows the mixing and delivery system  100  within the base  356  of the blister pack  354 , and  FIG. 23  shows the mixing and delivery system  100  being removed from the base  356  as a unit with one hand, the left hand (LH) of the user. Further, the flexible tether  142  allows the funneling device  138  to be moved with the one hand together with the mixing device  102  and the delivery device  104 . Furthermore, packaging the mixing and delivery system  100  in the coupled configuration before deployment in the surgical suite permits the user to immediately use of the system  100  without needing to couple the delivery device  104  to the mixing device  102 , either prior to or after commencement of the surgical procedure. Risk of user error is minimized, and the user can be confident a closed, sealed system is provided between the delivery device  104  and the mixing device  102 . 
     With the mixing and delivery system  100  in the sterile field of the surgical suite, the user may begin the three-step intuitive workflow, as generally shown in  FIGS. 22 and 23 . As indicated by the indicia  144  on the funneling device  138  being the number “1,” the first step includes the user inverting the funneling device  138  to be positioned within the aperture  135 . The number “1” indicia may also be included on the housing  116 , preferably near the aperture  135 , to help inform the user where to insert the funneling device  138 . The user introduces the liquid monomer  360  and the powered polymer  362  to the funneling device  138  to be directed to the chamber  112  within the mixing device  102 . As indicated by the indicia  152  on the actuator  148  being the number “2,” the second step includes the user providing an input to the actuator  148 , for example moving the slider  150  from the first position to the second position. In manners previously explained in detail, that through the actuation of the actuator  148 , the mixing device  102  automatically performs the operational cycle in a manner that mixes the bone cement components at atmospheric pressure and compresses and transfers the bone cement mixture in a self-sealing manner. Moreover, the mixing device  102  automatically deactivates to terminate the operational cycle after a predetermined period that is based on the end of the mixing, compression and transferring phases. Deactivation of the mixing device  102  indicates completion of step two of the intuitive workflow. The user may discern deactivation of the mixing device  102  from the elapsed time (e.g., less, equal to, or greater than one minute) and/or the absence of noise that may be associated with the motor  178 , the geartrain  184 , and the like. As indicated by the indicia  342  on the release assembly  110  being the number “3,” the third step of the intuitive workflow includes providing an input to the release assembly  110  to move the release assembly  110  from the locked position to the unlocked position, thereby permitting decoupling of the delivery device  104  from the mixing device  102 . The delivery device  104  is readied for use as shown in  FIG. 25 . 
     While bone cement compositions have been described as including the liquid monomer component and the powdered polymer component, other exemplary bone cement components may be mixed in accordance with the methods and systems described above, including those that include more than two components, those that include two liquid components, or those that include one or more paste components. In addition, the systems and methods described above may be used to deliver compositions other than bone cement, such as bone graft material, biological agents, other hardenable substances, and combinations thereof. 
     It is further contemplated that many modifications and variations are possible in light of the above teachings and the invention may be practiced otherwise than as specifically described. By way of examples and with reference to  FIG. 26 , the mixing and delivery system  100  is shown including stylized implementations of the mixing device  102  and the delivery device  104 . The delivery device  104  may be the same or similar as that shown in  FIG. 1 , disclosed in the aforementioned, International Publication No. WO2019/200091, or disclosed in the aforementioned U.S. Pat. No. 6,547,432, among others. Alternatively, the delivery device  104  may comprise a hydraulic mechanism, where mixing device  102  transfers bone cement into a cartridge capable of being pressurized by a hydraulic pump. 
     The mixing device  102  may include an internal structure and operation at least similar in many respects to the implementation previously discussed with only certain variations to be described in the interest of brevity. With continued reference to  FIG. 26 , the funneling device  138  may be integrated into the housing  116 . In particular, the upper shell  120  of the housing  116  defines the funnel  138 ′ being a sloped surface  139  extending downwardly from an upper surface. The funnel  138 ′ is in communication with the aperture (not shown) leading to the chamber (not shown). The integration of the funnel  138 ′ further reduces the footprint of the mixing device  102  and consequently the mixing and delivery system  100 . The reduced footprint may simplify packaging and consume less space in the operating suite. Moreover, the integration of the funnel  138 ′ may simplify the workflow for the user by removing the need for the user to insert the funneling device  138  of  FIG. 1  into the aperture  135 . 
     The release assembly  110  of the mixing device  102  may be a button  364  as opposed to the lever previously described.  FIG. 27  shows the button  364  disposed on the upper surface of the upper shell  122  of the housing  116  with “eject” indicia known to many. The button  364  may be actuated, and an internal mechanism (not shown) of the release assembly coupled to the button  364  may move the system  100  from the initial or locked position to the unlocked position to permit decoupling of the delivery device  104  from the mixing device  102 . As the release assembly  110  moves the system  100  from the initial or locked position to the unlocked position, the internal mechanism may be further configured to slightly move a portion of the delivery device  104  away from the mixing device  102  so as to provide a visual indication that the delivery device  104  is no longer docked and it is appropriate to fully remove the delivery device  104  for use. 
     In one implementation, the release or “undocking” of the delivery device  104  from the mixing device  102  may be based on movement of one or more components of the mixing device  102 . For example, mechanical, electromechanical, or electrical actuator(s) may detect when the piston  156  is located in a position within the second region  160  of the chamber  112  indicative of completion of the compression and transferring phases. Based on the position, the actuator(s) move the system  100  from the locked position to the unlocked position, and/or slightly move a portion of the delivery device  104  away from the mixing device  102 . 
     The mixing device  102  may include a display  366 , for example, a digital numeric display. The display  366  is shown as being disposed on a front surface of the upper shell  120 , but other suitable locations are contemplated. The display  366  is configured to provide information to the user regarding the operation of the system  100 , and more particularly the mixing device  102 . In one example, the display  366  displays a time remaining for the operational cycle. In other words, the display  366  counts down to zero from an initial time. In another example, the display  366  displays a time elapsed for the operational cycle. In other words, the display  366  counts up from zero. In still another example, the display  366  displays an estimation of remaining working time for the bone cement. A temperature sensor (not shown) may be included on the mixing device  102 . Owing to that total working time for bone cement is dependent on external temperature, an algorithm may be stored on memory (not shown) to determine total working time for the bone cement based on the temperature (e.g., room temperature) sensed by the temperature sensor. In combination with the timer function, a processor may determine the remaining working time as the difference between the total working time and the elapsed working time. In addition to the display  366  displaying the remaining working time as a numerical value, other types of visual indicia may be provided. The display  366  may change color (e.g., green, yellow, red) as the remaining working time falls below predetermined thresholds. Likewise, the display  366  may blink, and/or audible alarms may also be provided. Still further, the timer may be series of lights, a moving bar, an analog clock, or the like. 
     In certain implementations, the display  366  may be configured to selectively or automatically move between information regarding the operation of the mixing device  102 , or the bone cement. For example, the display  366  may provide a first output including time remaining for the operational cycle, as mentioned above. Then, after reaching zero, the display  366  may automatically move from the first output to a second output including counting up from zero to indicate the amount of elapsed working time. The user may selectively toggle between the first input, the second input, and/or any additional inputs. 
     The mixing device  102  may include at least one light  368 ,  370 ,  372  to enhance usability. In at least some respects, the lights  368 ,  370 ,  372  may be similar to the indicia  146 ,  152 ,  342  (see  FIGS. 2 and 20 ) to guide the user through the workflow. A first light  368  may be positioned near, on, about, or around the funneling device  138 , thus corresponding to the step of directing the bone cement components into the chamber  112  through the funneling device  138 . A second light  370  may be positioned near, on, about, or around a power button  374 , thus corresponding to the step of operating the mixing device  102  to initiate the operational cycle. A third light  372  may be positioned near, on, about, or around the button  364 , thus corresponding to the step of moving the release assembly  110  from the locked configuration to the unlocked configuration. The lights  368 ,  370 ,  372  may be light emitting diodes (LEDs) or other suitable light source. 
     The lights  368 ,  370 ,  372  may be in communication with the controller or processor. Based on certain actions, the controller may selectively control one or more of the lights  368 ,  370 ,  372  to illuminate to alert the user what to do next. In one workflow, the power button  374  may be actuated to turn on the mixing device  102 ; i.e., awake the mixing device  102  from a sleep-like state. The controller sends a signal to illuminate the first light  368 , as directing the bone cement components into the chamber  112  through the funneling device  138  may be the first step of the workflow. The first light  368  may remain illuminated until a sensor in communication with the controller (e.g., a load sensor within the chamber  112 , and optical sensor near the aperture  135 ) detect that the bone cement components have been directed into the chamber  112 . The controller, based on a signal received from the sensor, sends a corresponding signal to cease illumination of the first light  368  and illuminate the second light  370 , as pressing the power button  374  may be the second step of the workflow. The mixing device  102  beings the mixing, compression, and transferring phases of the operational cycle previously described. The display  366  may provide information regarding the status of the operational cycle. Once complete, the controller, sends a corresponding signal to cease illumination of the second light  370  and illuminate the third light  372 , as moving the release assembly  110  from the locked configuration to the unlocked configuration may be the third step of the workflow. The user may press the button  364 , and remove the delivery device  104  from the mixing device  102 . Once the button  364  is pressed, the display  366  may begin displaying the remaining working time as the difference between the total working time and the elapsed working time, for example, based on room temperature. 
     Certain implementations may be described with reference to the following exemplary clauses: 
     Clause 1—A method of making bone cement with a mixing device including a chamber defining an inlet opening, the chamber including a first end opposite a second end with the inlet opening between the first and second ends, the mixing device further including a piston disposed within the chamber, and a mixing paddle disposed within the chamber, the method comprising the steps of: with a face of the piston located within a first region of the chamber extending longitudinally between the first end of the chamber and the inlet opening, mixing with the mixing paddle the bone cement components at a first pressure to make a bone cement mixture; and moving the piston towards the second end of the chamber so that the face of the piston passes the inlet opening to be located within a second region of the chamber to compress the bone cement mixture at a second pressure greater than the first pressure. 
     Clause 2—The method of clause 1, wherein the first pressure is atmospheric pressure. 
     Clause 3—The method of clauses 1 or 2, further comprising the step of forming a fluid-tight closure between the piston and the chamber in the second region. 
     Clause 4—The method of any one of clauses 1-3, wherein the chamber further defines an outlet port adjacent the second end of the chamber, wherein the step of moving the piston further comprises moving the piston along the longitudinal axis within the second region to urge the bone cement out of the mixing device through the outlet port. 
     Clause 5—The method of any one of clauses 1-4, further comprising rotating the mixing paddle to mix of the bone cement components within the chamber. 
     Clause 6—The method of any one of clauses 1-5, further comprising the step of collapsing the mixing paddle with forces associated with each of the piston moving along the longitudinal axis and an interior face of the housing defining the second end of the chamber. 
     Clause 7—A method of making bone cement with a mixing device and transferring the bone cement to a delivery device coupled to the mixing device, the mixing device including a chamber defining an inlet opening, a piston disposed within the chamber, a mixing paddle disposed within the chamber, a motor coupled to the piston and the mixing paddle, an actuator coupled to the housing, and a door coupled to the actuator, the method comprising the steps of: introducing at least two bone cement components into the chamber through the inlet opening; and moving the actuator from the first position to a second position to cover the inlet opening with the door and simultaneously activate the motor while the piston is located within a first region, wherein activation of the motor rotates the mixing paddle to mix the at least two bone cement components in the chamber at atmospheric pressure to make a bone cement mixture, and moves the piston pass the inlet opening to within a second region of the chamber to (i) compress the bone cement mixture at a second pressure greater than atmospheric pressure, and (ii) transfer the bone cement to the delivery device. 
     Clause 8—The method as set forth clause 7, wherein the mixing device further includes a release assembly coupling the mixing device to the delivery device, the method further comprising the step of providing an input to move the release assembly from a locked position in which orientation features of the release assembly are engaging complementary orientation features of the delivery device, to an unlocked position in which the orientation features and complementary orientation features are disengage to permit decoupling of the delivery device from the mixing device. 
     Clause 9—The method of clauses 7 or 8, wherein the at least two bone cement components are a liquid monomer and a powdered polymer, wherein the step of introducing the bone cement components into the chamber further comprises directing both the liquid monomer and the powdered polymer through the inlet opening. 
     Clause 10—A mixing device for making bone cement, the mixing device comprising: a housing; a chamber within the housing, the chamber having a first region, and a second region separate from the first region; a mixing paddle rotatable within the chamber to mix bone cement components to make a bone cement mixture; a piston movable within the chamber to compress the bone cement components; a motor coupled to the piston and the mixing paddle; a switch connected to the motor with the switch configured to move between an activated state in which the switch initiates an operational cycle by activating the motor to effectuate at least one of movement of the piston and rotation of the mixing paddle, and a deactivated state in which the switch terminates the operational cycle by deactivating the motor, wherein the switch is biased toward the deactivated state; and an actuator coupled to the housing and movable between a first position in which the actuator is spaced apart from the switch, and a second position in which the actuator engages the switch to move the switch from the deactivated state to the activated state and maintains the switch in the activated state against the bias, wherein, the piston is configured to move within the chamber from the first region to the second region such that, when the piston is within the second region, the actuator is mechanically disengaged from the switch to permit the biased return of the switch from the activated state to the deactivated state. 
     Clause 11—The mixing device of clause 10, wherein the switch is a momentary switch. 
     Clause 12—The mixing device of clauses 10 or 11, further comprising: a transfer gear coupled to the motor and rotatable during the operational cycle; and a stop nut coupled to the transfer gear rotationally constrained relative to the transfer gear such that the stop nut is configured to translate along the transfer gear and engage the actuator to effectuate the mechanical disengagement of the actuator from the switch. 
     Clause 13—The mixing device of clause 12, wherein the stop nut further comprises a nut portion having an inner diameter threadably engaging an outer diameter of the transfer gear, and a flange portion extending from the nut portion with the flange portion configured to engage the actuator to effectuate the mechanical disengagement of the actuator from the switch. 
     Clause 14—The mixing device of any one of clause 10-13, wherein the actuator is a slider comprising a slider body, an arm extending from an underside of the slider body, and a stop feature coupled to the arm and configured to engage the switch. 
     Clause 15—The mixing device of clause 14, wherein the slider further comprises a ramping surface coupled to the arm and arranged to be engaged by the stop nut as the stop nut translates with rotation of the transfer gear, wherein the engagement of the stop nut with the ramping surface imparts flexion to the arm and disengage the stop feature from the switch. 
     Clause 16—A mixing device for making bone cement, the mixing device comprising: a housing; a chamber within the housing, the chamber having a first region, and a second region separate from the first region; a mixing paddle rotatable within the chamber to mix bone cement components to make a bone cement mixture; a piston movable within the chamber to compress the bone cement components; a motor coupled to the piston and the mixing paddle; a switch connected to the motor with the switch configured to move between an activated state in which the switch initiates an operational cycle by activating the motor to effectuate at least one of movement of the piston and rotation of the mixing paddle, and a deactivated state in which the switch terminates the operational cycle by deactivating the motor, wherein the switch is momentary and biased toward the deactivated state; and an actuator coupled to the housing and movable between a first position in which the actuator is spaced apart from the switch, and a second position in which the actuator engages the switch to move the switch from the deactivated state to the activated state and maintains the switch in the activated state against the bias. 
     The foregoing disclosure is not intended to be exhaustive or limit the invention to any particular form. The terminology which has been used is intended to be in the nature of words of description rather than of limitation.