34 is visible to the physician. Indicia (not shown) may be provided on the outer surface 52 of the chamber 32 to provide the physician with an amount of the curable material within the dispensing volume 34, and/or the amount of the curable material dispensed from the dispensing volume 34; i.e., based on a determined distance traveled by the plunger 42 within the dispensing volume 34. The indicia may be numerical graduations corresponding to a volume of the dispensing volume 34 (e.g., in cubic centimeters).

Referring to FIG. 5, the plunger 42 is slidably disposed within the dispensing volume 34. The plunger 42 is movable within the dispensing volume 34 in a distal direction (D) and a proximal direction (P). In particular, the plunger 42 is adapted to be advanced in the distal direction, to urge and/or compress the curable material (CM) within the dispensing volume 34, thereby urging at least a portion of the compressed curable material from the distal outlet 38. To facilitate the distal advancement of the plunger 42, the curable material dispensing system 30 includes a first control surface 60 adapted to receive a primary input from a user, and a lead screw 62 operably coupled to the first control surface 60. The plunger 42 is coupled to the lead screw 62, for example, at or near a distal end 64 of the lead screw 62, as shown in FIGS. 3 and 5. The lead screw 62 may be rotatably fixed relative to the first control surface 60. In a manner to be further described, the application of the primary input force, for example, a first torque input to the first control surface 60 in a first direction provides for rotation of the lead screw 62 with corresponding distal advancement of the plunger 42 within the dispensing volume 34. Conversely, the application of a second torque input to the first control surface 60 in a second direction opposite the first direction may provide for rotation of the lead screw 62 with corresponding movement of the plunger 42 in the proximal direction within the dispensing volume 34. It is contemplated that the plunger 42 may be rotatable relative to the lead screw 62 in a manner to reduce friction between the plunger 42 and the lead screw 62. The reduced friction between the plunger 42 and the lead screw 62 may facilitate backdriving of the system 30, such as during the movement of the plunger 42 in the proximal direction.

Referring now to FIGS. 3-5 and 8, the lead screw 62 includes the distal end 64 and a proximal end 66 opposite the distal end 64. A translation axis (TA) may be defined between the proximal and distal ends 64, 66 of the lead screw 62. The first control surface 60 may be associated with a handle 68. The handle 68 may include a proximal end 70, a distal end 72, and a lumen 74 at least partially extending between the proximal and distal ends 70, 72 of the handle 68. The lumen 74 may be coaxially disposed on the translation axis with at least a portion of the handle 68 extending from the interior 56 of the housing 50. The proximal end 66 of the lead screw 62 may be positioned within the lumen 74, as best shown in FIGS. 3-5. The handle 68 may further include drive features 76 defining at least a portion of the lumen 74. The drive features 76 of the handle 68 are adapted to engage with driven features 78 of the lead screw 62 complimentary to the drive features 76 such that the lead screw 62 is rotatably fixed relative to the first control surface 60 of the handle 68. With reference to FIG. 9, for example, the drive features 76 may define a rectangular-shaped lumen at least partially extending between the proximal and distal ends 70, 72 of the handle 68. The drive features 76 may further include slots 77 at least partially defining the lumen 74. The driven features 78 may be defined by the proximal end 66 of the lead screw 62 being at least substantially rectangular and sized to the lumen 74 of the handle 68. The driven features 78 may further include at least one ridge 79 (e.g., defined by a chord of the lead screw 62) extending longitudinally along the lead screw 62. The drive and driven features 76, 78 are engaged to prevent relative rotation between the lead screw 62 and the handle 68, but permit axial movement of the lead screw 62 relative to the first control surface 60 of the handle 68 along the translation axis.

The handle 68 may include a shaft 80 and a grip portion 82 coupled to the shaft 80. The grip portion 82 at least partially defines the first control surface 60. FIG. 8 shows the grip portion 82 positioned proximal to and extending radially outwardly from the shaft 80. The grip portion 82 is sized to be griped by one hand of the physician during operation. The first control surface 60 may be annularly disposed about the grip portion 82. At least the first control surface 60 of the grip portion 82 may be formed from material(s) with increased tack (e.g., rubber) to prevent inadvertent slipping of the hand during application of the first and second torque inputs to the first control surface 60. Further, at least the first control surface 60 of the grip portion 82 may include indentations and/or ridges to facilitate improved grip during use. Directional indicia (not shown) may be disposed on the handle 68 to provide guidance to the physician as to the first direction of rotation.

When the lead screw 62 is rotatably fixed relative to the first control surface 60, providing the first and second torque inputs to the first control surface 60 imparts rotation of the handle 68 and therefore, rotation of the lead screw 62. Yet the distal and proximal movement of the plunger 42 along the translation axis requires corresponding distal and proximal movement of the lead screw 62 coupled to the plunger 42. To facilitate, for example, distal movement of the plunger 42 and the lead screw 62 along the translation axis, the curable material dispensing system 30 includes a locking nut 90 including internal threads 92. With particular reference to FIGS. 8 and 8, the internal threads 92 of the locking nut 90 threadably engage external threads 94 of the lead screw 62 at least partially extending between its proximal and distal ends 64, 66. The locking nut 90 may be disposed within the interior 56 of the housing 50 and disposed coaxially on the translation axis. The locking nut 90 includes an aperture 96 for receiving the lead screw 62. FIG. 7 shows the lead screw 62 coaxially extending through the aperture 96 of the locking nut 90 with the internal threads 92 of the locking nut 90 in threadable engagement with the external threads 94 of the lead screw 62. The threadable engagement of the internal threads 92 of the locking nut 90 and the external threads 94 of the lead screw 62 provides for the distal advancement of the lead screw 62 (and the plunger 42) relative to the locking nut 90 in response to the first control surface 60 receiving the first torque input from the user. It is noted that the internal threads 92 of the locking nut 90 extend about an entirety of the aperture 96 (i.e., 360 degrees), whereas the external threads 94 encircle less than an entirety of the lead screw 62 to define partial threading (e.g., 90, 180, 270 degrees, etc.). The ridge(s) 79 extend between portions of the lead screw 62 not having the external threads 94. Alternatively, the internal threads 92 and/or the external threads 94 may extend about and encircle, respectively, all or less than 360 degrees.

FIGS. 8, 10 and 13 best show the locking nut 90 including a hub 100 and a ring gear 102 coupled to the hub 100. The hub 100 defines the aperture 96 and includes the internal threads 92 disposed about the aperture 96. The hub 100 may be disposed within a recess defined by the ring gear 102. The aperture 96 may be defined by the hub 100 and sized to receive the lead screw 62. The locking nut 90 may be formed from suitable materials including polymers, metals, combinations thereof, and the like.

The curable material dispensing system 30 provides for selectively preventing rotation of the locking nut 90 about the translation axis, resulting in the locking nut 90 providing for the distal advancement of the lead screw 62 with rotation of the same. Otherwise, when the locking nut 90 is permitted to rotate about the translation axis, rotation of the lead screw 62 results in concurrent rotation of the lead screw 62 and the locking nut 90 (due to characteristics of the internal threads 92 and the external threads 94) with minimal distance advancement of the lead screw 62 relative to the locking nut 90. Yet when the locking nut 90 is prevented from rotation about the translation axis, rotation of the lead screw 62 results in the distal advancement of the lead screw 62 relative to the locking nut 90 due to the threadable engagement between the internal threads 92 of the locking nut 90 and the external threads 94 of the lead screw 62. Likewise, when the locking nut 90 is prevented from rotation relative to the housing 50, rotation of the lead screw 62 results in the distal advancement of the lead screw 62 relative to the housing 50 due to the threadable engagement between the internal threads 92 of the locking nut 90 and the external threads 94 of the lead screw 62.

In order to selectively prevent rotation of the locking nut 90 about the translation axis, the locking nut 90 may include an engagement feature 98. In a manner to be described, the engagement feature 98 is adapted to be engaged (with application of a secondary input force) to prevent rotation of the locking nut 90 about the translation axis. The engagement feature 98 may include a plurality of teeth 118. The teeth 118 may extend radially from the ring gear 102, and more particularly, be disposed annularly about the ring gear 102 of the locking nut 90. The teeth 118 may be disposed about the distal and/or proximal rings 104, 105 forming the ring gear 112 of the locking nut 90. Alternatively, the engagement feature may be a notch, protrusion, etc.

Returning again to FIGS. 3 and 4, the system 30 may include an actuator 120 adapted to selectively engage the engagement feature 98 of the locking nut 90. The actuator 120 includes a second control surface 122 adapted to receive the secondary input force from the user. The actuator 120 further includes an engagement feature 123 complimentary to the engagement feature 98 of the locking nut 90, for example, complimentary teeth 124. With concurrent reference to FIG. 14, the actuator 120 may be a lever 126 pivotably coupled to the housing 50. The illustrated lever 126 is generally rectangular in shape and defines the second control surface 122 oriented away from the housing 50 so as to receive the secondary input force from the user. Alternatively, the actuator 120 may be a button, toggle switch, slider, and the like.

The teeth 124 are coupled to the actuator 120 and positioned generally opposite to the second control surface 122 so as to be oriented towards the locking nut 90. The teeth 124 may be arranged in a manner complimentary to an arcuate portion of the teeth 118 extending annularly about the locking nut 90. It is further contemplated that the actuator may be movable coupled to the housing 50 in other ways beyond pivotable coupling, such as slidable engagement, etc. The actuator 120 is operable between an engaged position and a disengaged position. In the engaged position, the complimentary engagement feature 123 engages the engagement feature 98 of the locking nut 90 to prevent rotation of the locking nut 90 about the translation axis. For example, the teeth 124 of the actuator 120 engage the teeth 118 of the locking nut 90. With the actuator 120 coupled to the housing 50, the locking nut 90 is rotatably fixed relative to the housing 50 when the actuator 120 is in the engaged position. In the disengaged position, the teeth 124 of the actuator 120 are spaced away from or otherwise disengaged from the teeth 118 of the locking nut 90. The locking nut 90 may rotate about the translation axis and relative to the housing 50 when the actuator 120 is in the disengaged position. The secondary input force provided to the second control surface 122 moves the actuator 120 between the engaged and disengaged positions. For example, the lever 126 may be initially in the disengaged position represented in FIG. 3. The user applies the secondary input force, such as a downward force to the lever 126 while supporting the housing 50. The lever 126 pivots relative to the housing 50 with the teeth 124 of the actuator 120 moving towards the teeth 118 of the locking nut 90. The teeth 118, 124 mesh to further define the engaged position of the actuator 120.

The system 30 may include a biasing member 128 operably coupled to the actuator 120. The biasing member 128 may bias the actuator 120 towards the disengaged position. For example, FIG. 3 shows the biasing member 128 being a coil spring adapted to engage a recess 129 on an underside of the actuator 120 (see FIG. 9). When the actuator 120 is in the engaged position, as shown in FIG. 4, the coil spring is compressed between the actuator 120 and the housing 50. Thus, the biasing member 128 may be adapted to bias the lever 126 away from the housing 50. As a result, application of the secondary input force to the second control surface 122 overcomes a biasing force provided by the biasing member 128 to move the actuator 120 from the disengaged position to the engaged position. Conversely, removal of secondary input force from the second control surface 122 provides for the biasing member 128 moving the actuator 120 from the engaged position to the disengaged position. The biasing member 128 may alternatively be a torsion spring, spring clip, constant force spring, or other suitable mechanism for biasing the actuator 120 to the disengaged position.

Alternatively, it is contemplated that the biasing member may be coupled to the in a manner that biases the actuator 120 to the engaged position, and the secondary input force applied to the second control surface 122 moves the actuator 120 from the engaged position to the disengaged position (i.e., the converse arrangement than as previously described). In such an implementation, the engagement feature 98 of the locking nut 90 may be engaged with, for example, teeth (not shown) positioned opposite the locking nut 90 from the actuator 120. The teeth are biased into engagement with the engagement feature 98 in the absence of the input of the secondary input force to the second control surface 122. The actuator 120 is biased into a position away from the locking nut 90 (e.g., the position shown in FIG. 2). Further, the actuator 120 is operably coupled to the teeth positioned opposite the locking nut 90. The application of the secondary input force to the second control surface 122 moves the actuator 120 towards the housing 50, which disengages the teeth from the engagement feature 98 against the biasing force provided by the biasing member. The locking nut 90, no longer constrained by the teeth rotatably fixed relative to the housing 50, may then rotate about the translational axis for reasons described throughout the present disclosure.

With the actuator 120 in the engaged position, application of the primary input force to the first control surface 60 results in rotation of the lead screw 62 about the translation axis and distal advancement along the translation axis due to the threadable engagement between the lead screw 62 and the locking nut 90. The distal advancement of the lead screw 62 results in the distal advancement of the plunger 42 within the dispensing volume 34. The curable material within the dispensing volume 34 is compressed and/or dispensed from the distal outlet 38. In the context of an exemplary surgical procedure for use with the curable material dispensing system 30, namely a vertebroplasty, the curable material may be dispensed to the extension tube 190 and through the access cannula directed through the cortical bone and into the cancellous region of the vertebral body.

Yet for any number of reasons, it may be desirable for the physician to immediately cease delivery of the curable material into, for example, the cancellous region of the vertebral body. As mentioned, one example is recognition an excessive amount of the curable material being introduced into the body. Despite removal of the physician's input, many known systems result in “drool” and additional curable material being delivered into the patient, contrary to the intentions of the physician. One of the many advantageous features of the system 30 of the present disclosure includes providing for proximal movement of the lead screw 62 (and the plunger 42) in a manner that minimizes or eliminates drool from the distal outlet 38 of the dispensing volume 34. In a manner to be explained in greater detail, the internal threads 92 of the locking nut 90 and the external threads 94 of the lead screw 62 are configured to provide for rotation of the locking nut 90 about the translation axis when the actuator 120 is in the disengaged position. The rotation of the locking nut 90 permits the plunger 42 to move proximally along the translation axis, and further permit the compressed curable material to at least partially decompress within the dispensing volume 34, as opposed to decompressing through the distal outlet 38.

Returning to FIG. 4, the system 30 is shown with the actuator 120 in the engaged position. In particular, the lever 126 may be positioned adjacent the housing 50 with the second control surface 122 substantially flush with the housing 50. The teeth 124 of the actuator 120 engage the teeth 118 of the locking nut 90 such that the locking nut 90 is rotatably fixed relative to the housing 50. As previously described, application of the first torque input to the first control surface 60 results in rotation of the lead screw 62 relative to the locking nut 90, which further provides for advancement of the lead screw 62 in the distal direction (D) along the translation axis (TA). The distal advancement of the lead screw 62 results in advancement of the plunger 42 in the distal direction and corresponding compression of the curable material (CM) within the dispensing volume 34 (see FIG. 5). In certain operating conditions, the curable material may be compressed to 200, 500, 1000, 3000, or 5000 or more pounds per square inch (psi). The compression of the curable material results in forces on the plunger 42 along the translation axis in the proximal direction (P).

Should the physician desire to immediately cease delivery of the curable material from the dispensing volume 34, the secondary input force provided to the second control surface 122 is simply removed. In manners previously described, the biasing member 128 biases the actuator 120 away from the housing 50 and from the engaged position to the disengaged position. Upon release of the secondary input force, the teeth 124 of the actuator 120 automatically disengage from the teeth 118 of the engagement feature 98 of the locking nut 90. The locking nut 90, no longer constrained by the actuator 120 rotatably fixed relative to the housing 50, may rotate about the translation axis.

The rotation of the locking nut 90 about the translation axis permits the lead screw 62 to move in the proximal direction along the translation axis. The lead screw 62 is urged in the proximal direction along the translation axis by the forces on the plunger 42 from the curable material compressed within the dispensing volume 34. The lead screw 62 translates in the proximal direction without rotation as the locking nut 90 rotates about the translation axis without translation. It is contemplated that some translation of the locking nut 90 may be provided or occur. The translation of the lead screw 62 in the proximal direction results in an increase in the dispensing volume 34 accessible to the compressed curable material. In other words, a portion of the dispensing volume 34 defined within the chamber 32 distal to the plunger 42 is increased. The curable material at least partially decompresses within the increased portion of the dispensing volume 34 now accessible to the compressed curable material. Further, with a diameter of the chamber 32 often being greater than a diameter of the distal outlet 38, even minimal movement of the plunger 42 in the proximal direction provides increased volume within the dispensing volume 34 for the curable material to decompress. In other words, the compressed curable material encounters less resistance within the increased portion of the dispensing volume 34 as opposed to exiting the distal outlet 38. The curable material is decompressed sufficiently to reduce the pressure gradient between the dispensing volume 34 and the surgical site in view of the viscosity of the partially compressed curable material. Therefore, the likelihood of drool is minimized or eliminated with the curable material dispensing system 30.

The movement of the lead screw 62 in the proximal direction is based on the interaction between the internal threads 92 of the locking nut 90 and the external threads 94 of lead screw 62. In other words, the internal threads 92 of the locking nut 90 and the external threads 94 of lead screw 62 are configured to provide for a backdrivable system. The backdrivable system may include the internal threads 92 of the locking nut 90 and the external threads 94 of lead screw 62 being defined by a screw efficiency of greater than 50%. In other words, if the screw efficiency is less than 50%, based on, for example, pitch of the threads 92, 94, friction between the threads 92, 94, and the like, the system 30 will not be backdrivable and the locking nut 90 will not rotate in response to the torque being transferred from the lead screw 62 being urged proximally by the compressed curable material. Stated differently, the forces from the compressed curable material on the plunger 42 and the lead screw 62 in the proximal direction results in a torque on the locking nut 90 greater than a backdriving torque (T_b) of the system 30 according to Equation 1:

$\begin{matrix} T_{b} = \frac{(F * P * n_{2})}{2 π}, & (1) \end{matrix}$

where F is the axial load, P is the screw lead, and 112 is the efficiency of the screw. Consequently, if the backdriving torque (T_b) of the system 30 is greater than the total friction torque, backdriving will occur. It is contemplated that any suitable material and dimensional design characteristics may be provided to the lead screw 62 and/or the locking nut 90 in order to achieve screw efficiency of greater than 50% and provide for translation of the lead screw 62 along the translation axis with corresponding rotation of the locking nut 90 about the translation axis. For example, having the external threads 94 not fully encircle the lead screw 62 may facilitate achieving lesser friction and greater screw efficiency.

In addition to minimizing or eliminating drool, the design of the lead screw 62 of the system 30, including the screw efficiency, provides for several additional benefits to be described. First, the forces from the compressed curable material on the plunger 42 (e.g., backpressure) is more efficiently transmitted to the hand(s) of the physician holding the system 30, and in particular the first control surface 60. This improves tactile feel for the physician, which may further provide for improved awareness of the volume of the curable material being dispensed from the dispensing volume 34 during use of the system 30. In other words, frictional losses within the system 30 are minimized, and thus more precise control is realized with each first torque input to the first control surface 60 resulting in predictable and precise volumes being dispensed from the dispensing volume 34. Second, efficiency is not sacrificed with the improved tactile feel provided to the physician. The mechanical advantage of the system 30 is substantially preserved, which among other things, limits physician fatigue and avoids loss of procedure operating time often hampering less robust systems. Third, the preserved mechanical advantage of the system 30 also results in the compressed curable material being rapidly delivered to the patient per torque input of the physician (i.e., a “fast start”). In other words, the lead screw 62 requires less turns to dispense the same amount of curable material to the patient relative to known systems with appreciable frictional losses. In one example, approximately 0.8 to 1.0 cubic cementers of curable material may be delivered per 360° revolution of the first control surface 60 without significant loss in mechanical advantage. Known systems with lead screws are limited to less than 0.5 cubic cementers per 360° revolution; otherwise, the frictional losses associated with a higher pitched lead screws require undesirably high inputs from the physician with associated increase in fatigue and working time. It is further contemplated that the internal threads 92 of the locking nut 90 and the external threads 94 of lead screw 62 may be modified as desired to alter the characteristics of the fast start. Likewise, lubricants and/or coatings may be applied to the lead screw 62 and/or the locking nut 90 to alter the characteristics of the fast start.

When the plunger 42 and the lead screw 62 are moving in the proximal direction, in particular during the backdriving of the system 30, it is desirable to limit or eliminate translation of the locking nut 90 along the translation axis. In particular, limiting or eliminating translation of the locking nut 90 along the translation axis more efficiently provides for rotation of the locking nut 90 about the translation axis for reasons previously described. Therefore, it is contemplated to include one or more bushings 63 and/or one or more bearings 65 positioned adjacent to or in abutment with the locking nut 90 within the interior 56 of the housing 50. FIGS. 6 and 8 shows the system 30 including two bushings 63 with the bearing 65 being a thrust bearing positioned intermediate the two bushings 63. Suitable means for reducing friction other than the thrust bearing are contemplated, such as ball bearings, needle bearings, lubricants, coatings, and the like. The tolerances between the bushings 63, the bearing 65, and the proximal ring 49 are designed to minimize or eliminate translation of the locking nut 90 in the proximal direction along the translation axis, and the bearing 65 is configured to facilitate rotation of the locking nut 90 about the translation axis.

As the plunger 42 is urged in the proximal direction along the translation axis by the forces on the plunger 42 from the curable material compressed within the dispensing volume 34, the axial forces are transmitted to the lead screw 62 and the locking nut 90 in threadable engagement with the lead screw 62. At least portion of the chamber mount 44, in particular the proximal ring 49, may define a loadbearing surface 67, is adapted to accommodate stress, strain, fatigue, wear, and the like, associated with appreciable forces transmitted from the compressed curable material to the lead screw 62 and the locking nut 90. In particular, the chamber mount 44 may define the void 47 sized to receive the locking nut 90, the bushing(s) 63, and/or the bearing 65. The axial forces may be transmitted from the locking nut 90, the bushings 63, and the bearing 65, to the loadbearing surface 67 and the opposing struts 45 fixed to the chamber 32. In such an implementation, the housing 50 may be considered non-loadbearing, and thus may be formed from less robust materials and/or less complex manufacturing processes. In particular, the void 47 accommodating the locking nut 90 is effectively integral into the chamber 32 (via the opposing struts 45) such that, when the chamber 32 is coupled to the housing 50, forces transmitted from the compressed curable material to the lead screw 62 and the locking nut 90 are internalized or dissipated within the chamber 32 itself.

Other suitable designs of the chamber 32, the chamber mount 44, and/or the housing 50 are contemplated consistent with the objects of the above disclosure. In one example, the second control surface 122 is operably coupled to the chamber 32 (as opposed to the housing 50) with the engagement features 98 coupled to the second control surface 122 configured to engage the teeth 118 of the locking nut 90 manners previously described. In such an example, any loading on the second control surface 122 (e.g., at the pivot of the lever 126) is internalized or dissipated within the chamber 32 itself, further rendering the housing 50 non-loadbearing.

As previously described in detail, the curable material dispensing system 30 provides for distal advancement of the plunger 42 in response to the first control surface 60 receiving the primary input force (e.g., the first torque input to the handle 68) with the actuator 120 in the engaged position. This may be effectuated by the physician applying the secondary input force to the second control surface 122 to maintain the actuator 120 in the engaged position with one hand, while simultaneously applying the first torque input to the first control surface 60 with another hand. For any number of reasons, the physician may remove the first hand from the first control surface 60. Most often, the physician does so in order to reset his or her hand for a subsequent application of the first torque input. Another example may include the physician needing to perform another aspect of the surgical procedure with the first hand while supporting the system 30 with the second hand. Yet based on the backdrivable aspects of the lead screw 62 and the locking nut 90, removing the primary input force from the first control surface 60 (with the actuator 120 in the engaged position) would otherwise result in the compressed curable material within the dispensing volume 34 forcing the plunger 42 and the lead screw 62 to rotate (and move in the proximal direction) with corresponding rotation of the first control surface 60. In other words, with the actuator 120 in the engaged position, the threads 92, 94 would cause the lead screw 62 to rotate within the locking nut 90 rotatably fixed relative to the housing 50. The rotation of the lead screw 62 in the second direction would sacrifice the distal advancement of the plunger 42, and undesirably require the physician to reestablish the position of the plunger 42 before continuing with the procedure. To overcome this potential shortcoming, the curable material dispensing system 30 includes the unidirectional torque mechanism 130.

Referring now to FIGS. 2-5, 9, 14 and 15, the unidirectional torque mechanism 130 may be operably coupled to the first control surface 60. The unidirectional torque mechanism 130 may be adapted to permit for rotation of the first control surface 60 about the translation axis in the first direction (e.g., R₁of FIG. 2), and generally prevent rotation of the first control surface 60 about the translation axis in the second direction (e.g., R₂of FIG. 2). More specifically, the unidirectional torque mechanism 130 permits the distal advancement of the lead screw 62 during application of the first torque input to the handle 68 in the first direction, and prevent proximal movement of the lead screw 62 upon removal of the first torque input. As a result, the physician is free to rotate the handle 68 in the first direction to distally advance the plunger 42 by a desired extent, then reset his or her hand on the handle 68 and/or perform another aspect of the surgical procedure without sacrificing the distal advancement of the plunger 42.

The unidirectional torque mechanism 130 may be a ratcheting mechanism including a ratchet member such as a ratchet ring 132 and at least one pawl 134. The pawl 134 is seated within a recess 136 defined by a flange 137 coupled to the handle 68. FIG. 9 shows a lug 138 extending radially outwardly from the shaft 80 of the handle 68 such that the lug 138 is coaxially disposed on the translation axis. The lug 138 may be provided at any suitable position on the shaft 80 between the proximal and distal ends 70, 72 of the handle 68. More than one recess 136 may be provided, such as the two recesses positioned on opposing sides of the lug 138. The pawl 134 is dimensioned to be at least partially seated within the recess 136. A biasing element 144 may be provided and operably coupled to the handle 68 and the pawl 134. The biasing element 144, for example, a coil spring or a torsion spring, biases the pawl 134 radially outwardly, thereby exposing the pawl 134 beyond the outer circumference of the lug 138 to engage the ratchet ring 132 in a manner to be described.

The ratchet ring 132 may be coaxially disposed on the translation axis and coaxially aligned with the lug 138 of the handle 68. The ratchet ring 132 is further positioned to encircle the lug 138 such that an inner surface 146 of the ratchet ring 132 is oriented towards the lug 138, and more particularly towards the pawl 134 seated within the lug 138 (see FIGS. 9 and 14). In other words, the ratchet ring 132 is operably coupled to the first control surface 60 at an interface between the inner surface 146 and the pawl 134 coupled to the lug 138. With reference to FIGS. 13 and 14, the ratchet ring 132 includes the inner surface 146 opposite an outer surface 148 and defining a proximal portion 150 of the ratchet ring 132. The ratcheting mechanism includes ratchet teeth 152 circumferentially disposed about the inner surface 146 of the ratchet ring 132. Each of ratchet teeth 152 may be asymmetrical and defined by a trailing edge facing the first direction (R₁) and a leading edge facing the second direction (R₂). With the first torque input provided to the primary control surface 60 in the first direction, the handle 68 and the pawl 134 coupled to the handle 68 rotate in the first direction about the translation axis. The pawl 134, biased towards the inner surface 146 with the biasing element 144, contacts the leading edge of the one of the ratchet teeth 152. Based on the shape of the leading edge (e.g., a ramp-like surface), the pawl 134 is urged away from the inner surface 146 with the biasing element 144 being resiliently deformed as the pawl 134 moves past each of the ratchet teeth 152. Assuming the locking nut 90 is rotatably fixed about the translation axis, the first control surface 60 is rotated with relatively little resistance with corresponding distal advancement of the lead screw 62.

With the second torque input provided to the primary control surface 60 in the second direction, the handle 68 and the pawl 134 coupled to the handle 68 rotate in the second direction about the translation axis until the pawl 134 engages the trailing edge of one of the ratchet teeth 152. The trailing edge of the ratchet 152 and a tip of the pawl 134 are shaped to firmly engage such that the primary control surface 60 cannot be further rotated in the second direction (in the absence of a defeatable mechanism to be described). Thus, the unidirectional torque mechanism 130 is adapted to permit for rotation of the first control surface 60 about the translation axis in the first direction, and generally prevent rotation of the first control surface 60 about the translation axis in the second direction. It is to be understood that the second torque input may originate from the lead screw 62 being urged proximally under the influence of the compressed curable material within the dispensing volume 34. Thus, the unidirectional torque mechanism 130 prevents proximal movement of the lead screw 62 rotatably fixed to the primary control surface 60 (and when the locking nut 90 is rotatably fixed about the translation axis).

Operation of the curable material dispensing system 30 may provide an audible indication and/or a tactile feedback to the physician. The unidirectional torque mechanism 130 may be configured to provide for an impact that may be heard and/or be felt by the hand of the physician holding the handle 68. In one non-limiting example, the biasing element 144 biases the pawl 134 towards the inner surface 146 of the ratchet ring 132. As the pawl 134 passes the trailing edge of each of the ratchet teeth 152 in the first direction, a brief moment occurs where a small gap exists between the pawl 134 and the inner surface 146 with the biasing element 144 being resiliently deformed. In other words, trailing edge of the ratchet teeth 152 may be shaped as a “plateau” relative to the inner surface 146 of the ratchet ring 132. Immediately upon passing the trailing edge at which the biasing element 144 is resiliently deformed, the biasing element 144 urges the pawl 134 towards the inner surface 146, quickly closing the gap. The impact between the pawl 134 and the inner surface 146 may provide the audible indication and/or the tactile feedback to the physician. In other words, the pawl 134 and the ratchet ring 132 may be formed from materials, such as metal or plastic, to provide a “click” as the pawl 134 strikes the inner surface 146 of the ratchet ring 132. Likewise, the pawl 134 strikes the inner surface 146 of the ratchet ring 132 may be with suitable force to be felt by the hand of the physician holding the handle 68.

With continued reference to FIG. 14, the ratchet teeth 152 may be circumferentially spaced equally about the inner surface 146 of the ratchet ring 152. As a result, an angular displacement of rotation of the first control surface 60 about the translation axis may be fixed between each successive audible indication and/or tactile feedback. Provided the locking nut 90 is rotatably fixed about the translation axis during the input of the first torque input to the first control surface 60, the angular displacement between each one of the equally spaced ratchet teeth 152 is associated with a fixed distance of the distal advancement of the lead screw 62 and the plunger 42 along the translation axis. By extension, the fixed distance of the distal advancement of the lead screw 62 and the plunger 42 along the translation axis may be associated with a fixed volume of compressed curable material dispensed from the dispensing volume 34. For example, each successive audible indication and/or tactile feedback may be associated with 0.05, 0.10, 0.25, 0.50, or 1.0 cc being dispensed from the dispensing volume 34. The fixed volume associated with each successive audible indication and/or tactile feedback may be based, at least in part, on circumferential spacing between the ratchet teeth 152, the pitch of the internal threads 92 of the locking nut 90 and the external threads 94 of the lead screw 62, and the like. While the movement of the plunger 42 may also be visible through the chamber 32 when formed from transparent materials, the audible indications and/or tactile feedback being associated with a fixed volume of curable material provides supplemental means for the physician to assess the amount of the curable material being dispensed from the system 30.

Alternatively, the unidirectional torque mechanism 130 may not include the biasing element 144 biasing the pawl 134 towards the inner surface 146 of the ratchet ring 132. The pawl 134 may be formed from resilient, semi-rigid, and/or shape memory material(s) (e.g., Nitinol) adapted to deflect under the forces from the ratchet teeth 152 as the pawl 134 moves past each of the ratchet teeth 152, then return to an original shape (in contact with the inner surface 146) after passing the trailing edge of the ratchet teeth 152 in the first direction. It should be also be appreciated that the ratchet ring may have alternative shapes and configurations other than what is shown, such as a polygonal shape. In certain implementations, the unidirectional torque mechanism 130 may be an overrunning clutch with a driver wheel adapted to be in engagement with a driven wheel. Other constructions of imparting unidirectional rotation between two structures may be implemented into the system of the present disclosure.

As previously described in detail, the curable material dispensing system 30 includes the safety feature of providing for proximal movement of the lead screw 62 along the translation axis in response to the actuator 120 being in the disengaged position. In implementations where the biasing member 128 biases the second control surface 122 away from the locking nut 90 (i.e., biases the second control surface such that the actuator is in the disengaged position), the safety feature can be activated by merely releasing the lever 126 with the lever 126 or other control surface acting as a so-called “dead man's switch.” Yet for any number of reasons, the physician may wish to provide for proximal movement of the lead screw 62 along the translation axis, for example, in addition to the proximal movement associated with the release of the “dead man's switch.” It is readily appreciated that the threads 92, 94 typically would provide for proximal movement of the lead screw 62 along the translation axis but for the unidirectional torque mechanism 130.

The curable material dispensing system 30 may include a defeatable unidirectional mechanism 160. The defeatable unidirectional mechanism 160 may operably couple the first control surface 60 and the housing 50. The defeatable unidirectional mechanism 160 permits proximal movement of the lead screw 62 in response to the first control surface 60 receiving the second torque input exceeding a torque threshold. By extension, the defeatable unidirectional mechanism 160 prevents for the proximal movement of the lead screw 62 when the second torque input does not exceed the torque threshold. In a practical sense, the defeatable unidirectional mechanism 160 is configured to prevent the rotation of the handle 68 in the second direction when the lead screw 62 is urged proximally under the influence of the compressed curable material within the dispensing volume 34 (e.g., when the physician resets his or her hand), but permit the rotation of the handle 68 in the second direction from the physician deliberating applying sufficient torque to the primary control surface 60, which would result in the proximal movement of the lead screw 62. It is to be understood that the torque threshold may be based primarily on a frictional relationship defining a clutch mechanism (generally referred to as 172) to be described, but also may further be based on friction between the internal and external threads 92, 94, the forces provided by the compressed curable material, and the like. Consequently, the torque threshold may be specifically designed (based on the characteristics of the clutch mechanism 172) such that the typical torque on the handle 68 from only the lead screw 62 being backdriven and urged proximally is less than the torque threshold.

The defeatable unidirectional mechanism 160 may be configured to permit for the distal advancement of the lead screw 62 in response to the first control surface 60 receiving the first torque input less than the torque threshold. In other words, in the first direction, the handle 68 may be easily rotatable at a torque relatively less than that required to rotate the handle 68 in the second direction (e.g., as the pawl 143 moves passed the teeth 152 in the first direction). It is understood that as the curable material becomes increasingly compressed within the dispensing volume 34, the first torque input required to distally advance the lead screw 62 (against the forces from the compressed curable material) may increase beyond the torque threshold.

Referring now to FIGS. 3-5, 13 and 14, the defeatable unidirectional mechanism 160 may include the unidirectional torque mechanism 130 previously described. In other words, the unidirectional torque mechanism 130 may be a functional component of the defeatable unidirectional mechanism 160. With concurrent reference to FIG. 8, the unidirectional torque mechanism 130 is positioned in the frictional relationship with the chamber mount 44 that is fixed relative to the housing 50, and the clutch mechanism 172 may be defined at the frictional interface (e.g., the unidirectional torque mechanism 130 “slips” relative to the chamber mount 44). The clutch mechanism 172 is configured to permit rotation of the ratchet ring 132 (operably coupled to the first control surface 60) in the first and second directions when the ratchet ring 132 receives a torque input exceeding the torque threshold sufficient to overcome the frictional relationship.

The ratchet ring 132 includes the inner surface 146 opposite the outer surface 148 to define the proximal portion 150 of the ratchet ring 132. The ratchet ring 132 may also includes a distal portion 151 coupled to the proximal portion 150. The distal portion 151 is positioned distally the proximal portion 150 and along the translation axis. Similar to the proximal portion 150, the distal portion 151 may be generally ring-shaped and defined between an inner annular surface 174 and an outer annular surface 176, as shown in FIGS. 12, 13 and 15. The outer annular surface 176 of the distal portion 151 may be in the frictional relationship with the chamber mount 44 to define the clutch mechanism 172. One or more frictional elements 180 may be provided at the interface between the outer annular surface 176 and an inner surface of the proximal ring 49 of the chamber mount 44 (see FIGS. 3-5 and 8) to increase the frictional relationship to achieve a desired torque threshold. In other words, if a relatively greater frictional relationship is associated with the clutch mechanism 172, the physician is required to provide a larger second torque input to the first control surface 60 to overcome the frictional relationship and move the lead screw 62 in the proximal direction along the translation axis. FIGS. 13 and 14 show the frictional elements being an O-ring disposed within a recess within the outer annular surface 176 of the distal portion 151. More than one O-ring may be provided. The O-ring(s) have a thickness slightly greater than a depth of the recesses in order to contact the inner surface of the chamber mount 44.

The clutch mechanism 172 is configured to permit rotation of the first control surface 60 in the first and second directions in response to receiving the first and second torque inputs, respectively, exceeding the torque threshold, and the unidirectional torque mechanism 130 is adapted to permit for rotation of the first control surface 60 in the first direction, and prevent rotation of the first control surface 60 about the translation axis in the second direction. Thus, with the unidirectional torque mechanism 130 and the clutch mechanism 172 functionally integrated, the first control surface 60 may be rotatable in the first direction when the first torque input is below the torque threshold.

A first magnitude of the first torque input is required to be provided to the primary control surface 60 to overcome the force of the biasing members 128 biasing the pawl 134 as the pawl 134 passes the ratchet teeth 152 in the first direction, along with the forces associated with the curable material compressed within the dispensing volume 34. A second magnitude of the first torque input defines the torque threshold associated with the clutch mechanism 172. The first magnitude is less than the second magnitude. In other words, the frictional engagement defining the clutch mechanism 172 should never be overcome as the handle 68 is rotated in the first direction, since the pawl 134 is configured to much more easily move past the ratchet teeth 152. In the second direction, however, the tip of the pawl 134 firmly engages the ratchet teeth 152, and increasing application of the second torque input is insufficient to overcome the engagement. The second torque input is effectively transferred from the handle 68, to the pawl 134, then to the ratchet teeth 152 of the ratchet ring 132. With continued increasing application of the second torque input, eventually the second torque input exceeds the torque threshold such that the frictional engagement of the clutch mechanism 172 is overcome and the ratchet ring 132 rotates relative to the chamber mount 44, and thus relative to the housing 50. The torque threshold may be two, three, five or time times greater than the first torque input required to rotate the handle 68 in the first direction. With the locking nut 90 in the engaged position, the second torque input above the torque threshold causes the lead screw 62 to move in the proximal direction relative to the locking nut 90. The above disclosure delineates that the defeatable unidirectional mechanism 160 is advantageously configured to provide for the distal advancement of the lead screw 62 with the first torque input less than the torque threshold; prevent for the proximal movement of the lead screw 62 with the second torque input less than the torque threshold; and permit for the proximal movement of the lead screw 62 with the second torque input exceeding the torque threshold. Consequently, with the actuator 120 engaging the locking nut 90, the physician may distally advance the plunger 42 within the dispensing volume 34 by rotating the handle 68 in the first direction with relative ease. The physician may release his or her hand to reset it (or for any other reason), and the handle 68 is prevented from rotating in the second direction by the defeatable unidirectional mechanism 160. The physician may cause the proximal movement of the plunger 42 in two ways: releasing the secondary input force to the second control surface 122, and/or rotating the handle 68 in the second direction with relative effort to overcome the frictional relationship.

In an alternative implementation, at least a portion of the defeatable unidirectional mechanism 160 may be rotatably fixed relative to the housing 50. For example, the defeatable unidirectional mechanism 160 may include a friction ring is rotatably fixed relative to the housing 50 with the first control surface 60 is movable (e.g., rotatable) relative to the friction ring. In another alternative implementation, the trailing edge of the ratchet teeth 152 and the tip of the pawl 134 are complimentarily shaped so as to cause defeatable engagement such that the primary control surface 60 can be rotated in the second direction when the second torque input exceeds the torque threshold.

In view of the foregoing description of the curable material dispensing system 30, methods of operating the system 30 are provided with reference to FIG. 16. The system 30 may be operated by the physician including first hand (FH) and second hand (SH) each includes a palm (P) and an index finger (I), a middle finger (M), and a thumb (T) extending from the palm (see FIG. 21). The housing 50 may be supported in the palm of the second hand of the physician. The secondary input force is applied to the second control surface 122 to move the second control surface 122 from the disengaged position to the engaged position. The secondary input force may be provided while the second hand supports the housing 50, such as with the index finger, middle finger, and/or the thumb of the second hand. The actuator 120 is moved into engagement with the locking nut 90 to prevent rotation of the locking nut 90 about the translation axis. The second control surface 122 is maintained in the engaged position against a force provided by the biasing member 128. The second control surface 122 with the index finger, middle finger, and/or the thumb of the second hand while supporting the primary control surface 60 with the first hand.

With the second control surface maintained in the engaged position, the primary input force is provided to the first control surface 60. The primary input force may be rotation provided by the index finger, middle finger, and/or the thumb of the first hand. The unidirectional torque mechanism permits the distal movement of the lead screw 62 with rotation of the first control surface 60 about the translation axis in the first direction with relative ease. The lead screw 62 moves distally along the translation axis to compress the curable material within the dispensing volume 34. The physician may remove the secondary input force provided to the second control surface 122. In particular, the index finger, middle finger and/or the thumb of the second hand may be removed from the second control surface 122 while supporting the housing 50 with the palm of the second hand, and while supporting the first control surface 60 with the first hand. The biasing member 128 resiliently moves the second control surface 122 from the engaged position to the disengaged position. The actuator 120 is moved out of engagement with the locking nut 90. The locking nut 90 is now rotatable about the translation axis and provides for movement of the lead screw 62 in the proximal direction along the translation axis to permit the compressed curable material to at least partially decompress within the dispensing volume 34.

According to another exemplary method of the curable material dispensing system 30, the actuator 120 is initially biased into engagement with the locking nut 90 with a force provided by the biasing member 128. In other words, without the secondary input force provided to the second control surface 122, the locking nut 90 is rotatably fixed about the translation axis. The primary input force is provided to the first control surface 60 while the locking nut 90 is rotatably fixed with the actuator 120 in the engaged position. The secondary input force is applied to the second control surface 122 with the secondary input force being sufficient to overcome the force provided by the biasing member 128 and move the actuator 120 to the disengaged position. The locking nut 90 is now rotatable about the translation axis and provides for movement of the lead screw 62 in the proximal direction along the translation axis to permit the compressed curable material to at least partially decompress within the dispensing volume 34. The secondary input force may be released from the second control surface 122, after which the biasing member 128 returns the actuator 120 to the engaged position with the locking nut 90. The threadable engagement between the internal threads 92 of the locking nut 90 and the external threads 94 of the lead screw provide for translation of the lead screw 62 distally along the translation axis to compress the curable material within the dispensing volume 34. The compressed curable material is dispensed from the distal outlet 38 of the chamber 32 in communication with the dispensing volume 34.

With continued reference to FIG. 16 and further reference to FIG. 1, as previously mentioned, the extension tube 190 may be coupled to the distal coupler 46 of the chamber 32. The extension tube 190 is adapted to be coupled to the surgical instrument secured within the patient, such as the access cannula penetrating bony anatomy. The extension tube 190 includes the elbow coupler 192, and a flexible tube 194 rotationally and/or pivotally coupled to the elbow coupler 192. The flexible tube 194 may be formed from flexible tubing, but it is contemplated that the flexible tube 194 may be of suitably rigid construction. It should be further appreciated that the components of the extension tube