US20040267272A1 - Bone cement mixing and delivery system - Google Patents

Abstract

A bone cement mixing and delivery system is provided. The system includes a mixing cartridge for receiving liquid and powder components of bone cement, a mixing device for mixing the components, and a delivery gun for discharging the bone cement from the mixing cartridge. The mixing cartridge comprises a cylinder having proximal and distal ends with a cylinder wall extending between the ends. A piston is locked at the distal end by a locking member that includes a pair of locking tabs protruding into slots in the cylinder wall. With the piston in the locked position, the mixing device, e.g., a mixing shaft and blade, mixes the components. After mixing, the cartridge is placed in the delivery gun and release buttons on the locking member are engaged by a release mechanism on the delivery gun to release the piston from the locked position.

Description

RELATED APPLICATIONS
• This application claims the benefit of U.S. provisional patent application Ser. No. 60/469,651, filed May 12, 2003 and U.S. provisional patent application Ser. No. 60/520,877, filed Nov. 18, 2003, the advantages and disclosures of which are herein incorporated by reference.[0001]
FIELD OF THE INVENTION
• The present invention generally relates to a bone cement mixing and delivery system. More specifically, the present invention relates to a mixing cartridge for receiving liquid and powder components of bone cement to be mixed, a mixing device for mixing the components, and a delivery gun for discharging the bone cement from the mixing cartridge into an anatomical site of a patient.[0002]
BACKGROUND OF THE INVENTION
• Bone cement mixing and delivery systems are well known for mixing liquid and powder components of bone cement and delivering the prepared bone cement to an anatomical site during various surgical procedures. Bone cement is particularly useful in orthopedic procedures in which a prosthetic device is fixed to a bone or joint structure to improve the strength, rigidity, and movement of the structure. In a total hip arthroplasty (THA) procedure, in which a hip joint is replaced with a prosthetic device, bone cement is used to fix the prosthetic device in place in a medullary canal of a femur.[0003]
• Typically, the bone cement is prepared in a mixing cartridge. The mixing cartridge includes a cylinder having proximal and distal ends with a mixing chamber defined between the ends. The mixing cartridge further includes a cap covering the proximal end of the cylinder and a piston disposed in the distal end of the cylinder such that the mixing chamber is further defined between the cap and the piston. The piston may be releasably secured in a locked position in the cylinder by a cotter pin. The cap supports a mixing device, i.e., a mixing shaft and blade, for mixing the liquid and powder components of the bone cement in the mixing chamber.[0004]
• Once the bone cement is mixed, the mixing cartridge is prepared for inserting into a delivery gun to discharge the bone cement. This may include disengaging the mixing shaft and coupling a nozzle to the cap to provide a discharge point for the bone cement. At the same time, the piston is released from the locked position in the distal end of the cylinder by pulling the cotter pin. This allows the piston to be driven by the delivery gun through the mixing chamber to discharge the bone cement from the nozzle. An alternative solution for securing and releasing the piston is shown in U.S. Pat. No. 5,328,262 to Lidgren et al.[0005]
• In Lidgren et al., the piston is releasably secured in the locked position in the distal end of the cylinder by a gripping portion in the form of a flange, which extends along only a portion of an inner periphery of the cylinder. The piston in Lidgren et al. has a corresponding gripping portion in the form of an outwardly directed lip that protrudes behind the flange. The lip defines a groove with an outer surface of the piston to receive the flange. To release the piston from the locked position, the flange is rotated through the groove until the flange has been rotated past the lip. Lidgren et al. discloses a base that is used to secure the piston from rotation while a user rotates the cylinder relative to the piston to release the piston from the locked position. This method of releasing the piston from the locked position, much like pulling the cotter pin, requires additional manipulation by a user.[0006]
• Once the piston is released from the locked position, the mixing cartridge is inserted into the delivery gun. A typical delivery gun includes a ram disk that engages the piston and drives the piston through the mixing chamber to discharge the bone cement from the nozzle. The delivery gun includes a cradle for supporting the mixing cartridge and a casing for supporting a drive rod that engages the ram disk and advances the ram disk to drive the piston. The drive rod includes a plurality of teeth and a pawl member engages the teeth to advance the drive rod. A trigger supports the pawl member and the casing rotatably supports the trigger. Actuation of the trigger relative to the casing urges the pawl member against the teeth to advance the drive rod.[0007]
• An example of such a delivery gun is illustrated in U.S. Pat. No. 5,431,654 to Nic. In the '654 patent to Nic, two pawl members are used to independently advance the drive rod and the ram disk. The pawl members provide high speed/low force and low speed/high force advancement of the drive rod. A switch is used to select between the speeds. When high speed is selected, both pawl members engage the drive rod, while only the high-speed pawl member actually advances the drive rod. When low speed is selected, the high-speed pawl member is isolated from the teeth such that only the low speed pawl member engages the teeth to advance the drive rod. However, in Nic, the trigger directly supports each of the pawl members which results in a low mechanical advantage to advance the drive rod and ram disk.[0008]
BRIEF SUMMARY OF THE INVENTION
• A mixing cartridge for receiving liquid and powder components of bone cement to be mixed for medical use. The mixing cartridge comprises a cylinder having proximal and distal ends with a mixing chamber defined therebetween. The cylinder includes a cylinder wall extending between the ends about a longitudinal axis of the cylinder. A piston is disposed in the cylinder at the distal end such that the mixing chamber is further defined between the proximal end and the piston. A locking member is coupled to the piston to lock the piston in the distal end. The locking member includes a male portion engaging a female portion in the cylinder wall to place the piston in a locked position at the distal end of the cylinder. The locking member includes a resilient portion for biasing the male portion into mating engagement with the female portion. The piston remains in the locked position at the distal end of the cylinder while mixing the liquid and powder components.[0009]
• One advantage of the mixing cartridge is the conveniently positioned locking member used to lock the piston in the distal end. By using the resilient portion to bias the male portion into mating engagement with the female portion, a user can easily release the piston from the locked position by either manually or mechanically acting against the bias of the resilient portion to disengage the male and female portions.[0010]
• A delivery gun is also provided for discharging the bone cement from the cartridge once the bone cement is prepared. The delivery gun comprises a casing for supporting the cartridge. A drive mechanism is supported by the casing and advanceable relative to the casing to force the bone cement from the cartridge. The casing pivotally supports a trigger operatively connected to the drive mechanism to advance the drive mechanism upon actuation of the trigger to force the bone cement from the cartridge. A linkage system works in conjunction with the trigger to advance the drive mechanism. The linkage system comprises a first link pivotally connected to the casing and a second link interconnecting the first link and the trigger such that actuating the trigger moves the second link and the first link to advance the drive mechanism.[0011]
• An advantage of the delivery gun is the use of the linkage system to increase the mechanical advantage needed to successfully advance the drive mechanism and force the bone cement from the cartridge while minimizing fatigue to a user of the delivery gun.[0012]
• In one aspect of the delivery gun, the drive mechanism includes a drive rod and gripper plates to advance the drive rod. The gripper plates frictionally engage the drive rod to advance the drive rod when the trigger is actuated. In one embodiment, the gripper plates include mating pegs and notches to align adjacent gripper plates. In another embodiment, the gripper plates are coated to increase lubricity and corrosion resistance thereof.[0013]
• In another aspect of the delivery gun, the drive mechanism includes a drive rod and first and second pawl members to advance the drive rod. In one embodiment, the second pawl member is movable into engagement with teeth on the drive rod for high-speed advancement of the drive rod and out from engagement with the teeth for low-speed advancement. During low-speed advancement, only the first pawl member engages the teeth to advance the drive rod. During high-speed advancement, both pawl members engage the teeth, but only the second pawl member works to advance the drive rod.[0014]
• A bone cement mixing and delivery system is also provided. The mixing and delivery system includes the cartridge and the delivery gun. In this aspect of the invention, the locking member includes a release button to release the piston from the locked position. At the same time, the delivery gun includes a release mechanism integrated into the drive mechanism to engage the release button. When the cartridge is placed into the cradle of the delivery gun, the drive mechanism is advanced and the release mechanism engages the release button to release the piston from the locked position. This configuration reduces the number of steps typically associated with releasing the piston. By incorporating the release mechanism into the drive mechanism, when the drive mechanism is advanced, the piston is automatically released.[0015]
• A bone cement loading system for receiving the liquid and powder components of the bone cement is also provided. The loading system includes the cylinder with the piston locked in the distal end. A base defining a cavity is provided for receiving and securing the distal end of the cylinder. A funnel is provided for coupling to the proximal end of the cylinder to channel the powder component of the bone cement into the mixing chamber. The funnel has a proximal end with an oblong oval-shaped periphery to facilitate loading of the powder component of the bone cement into the mixing chamber and a distal end with a circular periphery for snugly fitting into the proximal end of the cylinder. One particular advantage to this loading system is the use of the oblong oval-shaped funnel. The shape of the funnel reduces any mess typically associated with filling the mixing chamber with powder.[0016]
• A bone cement mixing system comprising the mixing cartridge and a mixing shaft and blade is also provided. The blade is coupled to the mixing shaft and disposed in the mixing chamber for rotating with the mixing shaft about the longitudinal axis to mix the liquid and powder components of the bone cement. The blade includes a center hub coupled to the mixing shaft and an outer ring extending from the center hub. The outer ring forms an acute angle with the longitudinal axis of between twenty and seventy degrees to ensure adequate mixing of the bone cement in the mixing chamber.[0017]
• A method of mixing the liquid and powder components of the bone cement in the mixing chamber is also provided. The method includes using a rotary power tool connected to a portion of the mixing shaft extending outside of the mixing chamber to mix the liquid and powder components of the bone cement. The blade is disposed in the mixing chamber while being operatively connected to the portion of the mixing shaft extending outside of the mixing chamber. In the method, the rotary power tool is first connected to the portion of the mixing shaft extending outside of the mixing chamber. Then the rotary power tool is actuated to rotate the blade and mix the liquid and powder components of the bone cement. At the same time, the rotary power tool is axially displaced relative to the mixing cartridge to completely mix the liquid and powder components of the bone cement. Once mixing is complete, the operative connection between the blade and the portion of the mixing shaft extending outside of the mixing chamber is removed.[0018]
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
• Advantages of the present invention 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 wherein:[0019]
• FIG. 1 is an exploded perspective view of a mixing cartridge of the present invention in combination with a mixing shaft and blade;[0020]
• FIG. 2 is an assembled perspective view of the mixing cartridge with the mixing shaft and blade supported therein;[0021]
• FIG. 3 is an exploded perspective view of a cap of the mixing cartridge;[0022]
• FIG. 4 is a cross-sectional view of the cap of FIG. 3 and a partial cross-sectional view of a cylinder of the mixing cartridge to illustrate fitting of the cap to the cylinder;[0023]
• FIG. 5 is an exploded perspective view of the cap and the mixing shaft and blade;[0024]
• FIG. 6 is an assembled perspective view of the cap with the mixing shaft and blade supported therein;[0025]
• FIG. 7 is a perspective view of the blade;[0026]
• FIG. 7A is a side elevational view of the blade of FIG. 7;[0027]
• FIGS. 8-8A and[0028]9 are perspective views of alternative blades;
• FIG. 10 is a an exploded perspective view of the mixing shaft and a latch rod;[0029]
• FIG. 11 is an elevational end view of the mixing shaft and latch rod of FIG. 10;[0030]
• FIG. 12 is a cross-sectional view of the mixing shaft and latch rod of FIGS. 10 and 11;[0031]
• FIG. 13 is an exploded perspective view of a release latch coupling the mixing shaft and latch rod;[0032]
• FIGS. 14A-14C illustrate the release of the blade from the mixing shaft;[0033]
• FIG. 15 is an exploded perspective view of a piston of the mixing cartridge;[0034]
• FIG. 16 is a cross-sectional view of the piston of FIG. 15;[0035]
• FIG. 17 is a perspective view of an alternative piston of the mixing cartridge;[0036]
• FIG. 18 is a top view of the alternative piston of FIG. 17;[0037]
• FIG. 19 is an exploded perspective view of the cap and a nozzle;[0038]
• FIG. 20 is an assembled perspective view of the cap and nozzle;[0039]
• FIG. 21 is a blown-up view of a locking mechanism of the cap and nozzle;[0040]
• FIGS. 22-23 are perspective views of the nozzle;[0041]
• FIG. 24 is a perspective view of a delivery gun of the present invention illustrating a linkage system of the delivery gun;[0042]
• FIGS. 24A-24B illustrate alternative linkage systems of the present invention;[0043]
• FIG. 25 is an elevational view illustrating release of a locking member securing the piston;[0044]
• FIG. 26 is a partial perspective view of an alternative linkage system and drive mechanism of the delivery gun;[0045]
• FIG. 27 is a partial perspective view of the alternative linkage system and drive mechanism of FIG. 26 employing a striker to prevent freeze-up of the drive mechanism;[0046]
• FIGS.[0047]28 is an elevational view of a second alternative embodiment of the linkage system and drive mechanism of the delivery gun in a low-speed position;
• FIG. 29 is a perspective view of the second alternative embodiment of the linkage system and drive mechanism in the low-speed position;[0048]
• FIG. 30 is an elevational view of the second alternative embodiment of the linkage system and drive mechanism in a high-speed position;[0049]
• FIG. 31 is a perspective view of the second alternative embodiment of the linkage system and drive mechanism in the high-speed position;[0050]
• FIG. 32 is an exploded view of a cylinder of the mixing cartridge and a base and funnel used to fill the cylinder with components of bone cement; and[0051]
• FIGS. 33-42 illustrate various steps associated with the present invention.[0052]
DETAILED DESCRIPTION OF THE INVENTION
• Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a bone cement mixing and delivery system is generally shown. The bone cement mixing and delivery system comprises a mixing[0053]cartridge100 for receiving liquid monomer and powdered copolymer components of bone cement to be mixed, a mixing device (mixingshaft150 and blade152) for mixing the components, and a delivery device, e.g., adelivery gun500, for discharging the bone cement from the mixingcartridge100 into an anatomical site (not shown). An exemplary use for the bone cement is to secure a prosthetic device used to replace a joint structure such as in a total hip arthroplasty (THA) procedure.
• Referring to FIGS. 1 and 2, the bone cement mixing system comprises the mixing[0054]cartridge100 in combination with the mixingshaft150 andblade152 used to mix the components of the bone cement in the mixingcartridge100. The mixingcartridge100 includes acylinder102 having proximal104 and distal106 ends. A mixingchamber108 is defined between theends104,106. Thecylinder102 includes acylinder wall110 extending between theends104,106, about a longitudinal axis L. Acap112 is coupled to thecylinder102 at theproximal end104 and apiston114 is disposed in thecylinder102 at thedistal end106 such that the mixingchamber108 is further defined between thecap112 and thepiston114. The components of the bone cement are placed in the mixingchamber108 and mixed by the mixingshaft150 andblade152, as will be described further below.
• In the preferred embodiment, the[0055]cylinder102 has lockingstrips116 disposed on thecylinder wall110 at theproximal end104 to insert into lockingslots118 on thecap112. Each of the locking strips116 include a straight portion lying perpendicular relative to the longitudinal axis L and an angled portion lying at an angle relative to the straight portion. As should be appreciated, the locking strips116 and lockingslots118 could be reversed, i.e., the locking strips116 positioned on thecap112 and the lockingslots118 defined in thecylinder wall110. The locking strips116 and lockingslots118 are configured to provide quick locking of thecap112 onto thecylinder102 with a one-quarter turn of thecap112. Those of ordinary skill in the art will appreciate that numerous methods are available for connecting thecap112 to thecylinder102, such as mating threads, snap-fit connections, etc. Agroove120 is formed in thecylinder102 at theproximal end104 to seat an o-ring seal122. The o-ring seal122 assists in sealing thecap112 to thecylinder102.
• Referring to FIGS. 3-4, the[0056]cap112 includes radially inwardly protrudingramps124 that lead into the lockingslots118 to facilitate the fit with the locking strips116 on thecylinder wall110. When first placing thecap112 on thecylinder102, the locking strips116 are positioned between theramps124. As thecap112 is rotated, theramps124 cam the locking strips116 proximally to urge theproximal end104 of thecylinder102 into a sealed relationship with thecap112, as shown in FIG. 4 (only a portion of thecylinder wall110 with two lockingstrips116 is shown in FIG. 4 for illustrative purposes). In the preferred embodiment, there are four lockingstrips116 and four lockingslots118 to facilitate the sealed relationship between thecap112 and thecylinder102.
• Referring specifically to FIG. 4, an o-[0057]ring seal126 anddynamic seal128 operate together within anorifice130 in thecap112 to movably support and seal to the mixingshaft150. The mixingshaft150 slides through theorifice130 and thedynamic seal128 and is movably supported therein. Thedynamic seal128 allows nearly frictionless rotational, as well as axial movement of the mixingshaft150 within the mixingchamber108 to mix the liquid and powder components of the bone cement, while maintaining a snug fit within theorifice130. Afilter132 andliner134 are positioned on an interior of thecap112 to allow a vacuum to be drawn in the mixingchamber108 by way of avacuum port136. Thevacuum port136 is isolated from the mixingchamber108 by thefilter132 andliner134 to prevent fouling of a vacuum pump (not shown). Referring to FIGS. 5-6, avacuum tube138 is shown attached to thevacuum port136 to draw the vacuum in the mixingchamber108 during mixing.
• Referring to FIG. 7, the[0058]preferred blade152 used to mix the bone cement is shown. Theblade152 is integrally formed from plastic in one piece and has anouter ring154 connected to acenter hub156 byvanes158.Ears160 protrude radially inwardly from thecenter hub156 to facilitate a releasable connection to the mixingshaft150. The releasable connection is described further below. Referring to FIG. 7A, theouter ring154 forms an acute angle a with the longitudinal axis L of the cylinder102 (which is also a rotational mixing axis of the blade152). The acute angle a is important for efficient mixing of the bone cement. The acute angle a is preferably between twenty and seventy degrees, and more preferably sixty degrees. Theblade152 has an effective height H that is greater than one quarter inch to ensure adequate mixing. Preferably, the effective height H of theblade152 is approximately one half inch.
• Referring back to FIG. 7, two radially inwardly protruding[0059]fingers157 are attached to theouter ring154. One of thefingers157 protrudes radially inwardly in a first plane and theother finger157 protrudes radially inwardly in a second plane spaced from and parallel to the first plane. Thecenter hub156 is positioned between the planes. Thefingers157 are used to scrape proximal and distal regions of the mixingchamber108 to ensure complete mixing. A protrudingnode159 is also attached to theouter ring154. Thenode159 protrudes radially outwardly to control spacing between theblade152 and an inner periphery of thecylinder wall110 by scraping along the inner periphery of thecylinder wall110 in the mixingchamber108.
• FIGS. 8 and 8A illustrate[0060]alternative blades252,352 that could also be used to mix the bone cement. Each of theblades152,252,352 is designed to flatten at theproximal end104 of thecylinder102 adjacent to thecap112 after theblade152,252,352 is released from the mixingshaft150 in the mixingchamber108. This ensures that the maximum possible amount of bone cement can be discharged from the mixingcartridge100. In the case of thepreferred blade152, theblade152 is flexible and theouter wall154 flattens into a plane perpendicular to the longitudinal axis L and occupied by thecenter hub156, as illustrated by hidden lines in FIG. 7A. Thus, the effective height H is reduced and the acute angle a becomes close to ninety degrees. This is accomplished by twisting at thevanes158.Spaces155,255,355 formed in thecenter hub156,256,356 ensure that once theblade152,252,352 is flattened, the bone cement can pass through theblade152,252,352 when discharged from the mixingcartridge100. To further facilitate the discharge of the bone cement past theblades152,252,352, each of thecenter hubs156,256,356 are sized to partially fit within theaperture130 defined in thecap112.
• Another[0061]alternative blade452 is shown in FIG. 9. Thisblade452 is a relativelythick disk452 with chamfered ends453 forming an acute chamfer angle with asidewall457. The chamfer angle is preferably sixty degrees. In the preferred embodiment, the disk is about one half inch thick and about one eighth inch less in diameter than the inner periphery of thecylinder wall110. In one embodiment, the inner periphery of thecylinder wall110 is about two and one quarter inches in diameter. As should be appreciated, the slight distance between theside wall457 of thedisk452 and the inner periphery of thecylinder wall110 creates a shear force on the bone cement as thedisk452 is rotated and moved axially in the mixingchamber108. The shear force is the force applied to the bone cement to mix the bone cement. Thisblade452 also includes a space455 formed in a center of thedisk452 andears460 for releasably attaching to the mixingshaft150.
• Referring to FIGS. 10-13 the mixing[0062]shaft150 has arelease latch162 for releasing theblade152 from the mixingshaft150 once mixing of the bone cement is complete. Therelease latch162 moves between a holding position and a releasing position. In the holding position, theblade152 is secured to the mixingshaft150 to mix the bone cement in the mixingchamber108. In the releasing position, theblade152 is released from the mixingshaft150 to remain in the mixingchamber108 while the mixingshaft150 is removed from thecap112 to make way for anozzle204, as will be described further below. Therelease latch162 is operatively connected to alatch rod164, which latches theblade152 to the mixingshaft150 in the holding position. Thelatch rod164 defines asplit cavity166 for receiving splitlegs168 of therelease latch162 in a snap-fit manner. Thelatch rod164 is rotatably supported within the mixingshaft150.
• Referring to FIGS. 14A-14C, the transition of the[0063]release latch162 between the holding position and the releasing position is illustrated. Referring first to FIG. 14C, theexposed end170 of thelatch rod164 is generally “T” shaped. Thecorresponding end172 of the mixingshaft150 has opposednotches174 that are adapted to receive theears160 on thecenter hub156 of theblade152. Initially, theears160 are positioned in thenotches174 and theexposed end170 is positioned over theears160 to hold theblade152 to the mixingshaft150. See FIG. 14A. To release theblade152, therelease latch162 is depressed and rotated. Rotating therelease latch162 rotates thelatch rod164 with respect to the mixingshaft150 thus rotating theexposed end170 away from theears160 to release theblade152. See FIG. 14B. With theblade152 released, the mixingshaft150 is withdrawn from thecap112 while theblade152 remains in the mixingchamber108.
• A[0064]proximal end176 of the mixingshaft150, which represents a portion of the mixingshaft150 extending outside of the mixingchamber108 during mixing, is adapted to engage a rotary power tool177 (see FIG. 37), such as a reamer drill, used to rotate the mixingshaft150 andblade152 and mix the bone cement. Theproximal end176 of the mixingshaft150 is operatively connected to theblade152 to transfer the rotation of therotary power tool177 to theblade152. When theblade152 is released from the mixingshaft150, the operative connection is removed. The operative connection is also removed if the portion of the mixingshaft150 extending outside of the mixingchamber108 is severed from the rest of the mixingshaft150 in the mixingchamber108, as in alternative embodiments. A manually operated mixing handle (not shown) could engage the mixingshaft150 at theproximal end176 to mix the bone cement in other embodiments.
• Referring to FIGS. 15-16, the[0065]piston114 is positioned within thedistal end106 of thecylinder102 to further seal themixing chamber108. Thepiston114 has askirt178 extending about the inner periphery of thecylinder wall110. Thepiston114 also includes aproximal end180 and adistal end182 defining acavity184.
• Referring specifically to FIG. 16, the[0066]piston114 is releasably secured in a locked position in thedistal end106 of thecylinder102 by a lockingmember186. The lockingmember186 is disposed in thecavity184 and includes diametrically opposed lockingtabs188 protruding into diametricallyopposed slots190 defined in thecylinder wall110 to secure thepiston114 to thecylinder102. It should be appreciated that theslots190 could be in the form of any suitable female portion, e.g., slot, groove, channel, etc., used for interlocking with a corresponding male portion such as the lockingtabs188. Furthermore, while the embodiment of FIG. 16 illustrates two-way locking, i.e., thepiston114 being locked from moving proximally and distally, the lockingmember186 could also be used for one-way locking, i.e., for preventing only proximal movement of thepiston114.
• The locking[0067]member186 is integrally formed from plastic and aresilient portion192 of the lockingmember186 biases the lockingtabs188 radially outwardly from the longitudinal axis L into theslots190. Theresilient portion192 is in the form of a thinresilient ribbon192 acting like a spring and extending is a winding shape between the lockingtabs188. The lockingtabs188 couple the lockingmember186 to thepiston114 by protruding throughcarrier slots194 formed in theskirt178. In the preferred embodiment, astep196 protrudes into each of thecarrier slots194 to define a guide for sliding engagement within achannel198 partially defined in each of the lockingtabs188. In the locked position, thecarrier slots194 are axially and radially aligned with theslots190 formed in thecylinder wall110.
• The[0068]piston114 is locked at thedistal end106 of thecylinder102 while the liquid and powder components are added and mixed in the mixingcartridge100. Thepiston114 is released from the locked position after mixing of the bone cement is complete.Release buttons200, integrally formed with the lockingtabs188, are used to release thepiston114 from the locked position. Therelease buttons200 are disposed on the lockingtabs188 and protrude distally therefrom. Each of therelease buttons200 includes acam surface202 forming an acute angle with the longitudinal axis L. Thepiston114 is released from the locked position by squeezing therelease buttons200 radially inwardly against the bias of theresilient portion192 to withdraw the lockingtabs188 from theslots190. This action can be performed either manually or mechanically, as will be described further below. After release from theslots190, the lockingtabs188 remain coupled to thepiston114 in thecarrier slots194.
• Referring to FIGS. 17-18, an[0069]alternative locking member386 is shown. Thealternative locking member386 includes lockingtabs388 that are biased radially outwardly from the longitudinal axis L of thecylinder302 to engage theslots390 in thecylinder wall310. In this embodiment, fourslots390 are defined in thecylinder wall310 to receive the lockingtabs388. Theresilient portion392 is further defined as aresilient base392 resiliently supporting each of the lockingtabs388 on thepiston314 with each of the lockingtabs388 being radially biased outwardly from theskirt378 of thepiston314 to engage theslots390 in thecylinder wall310. Therelease buttons400 are further defined asfingers400 extending radially inwardly toward the longitudinal axis L of thecylinder302 with thefingers400 being engageable to urge the lockingtabs388 radially inwardly and withdraw the lockingtabs388 from theslots390 in thecylinder wall310 to release thepiston314 from the locked position.
• Referring to FIGS. 19-23, once the bone cement is mixed, and the mixing[0070]shaft150 is withdrawn from thecap112, thenozzle204 is positioned on thecap112. In the disclosed embodiment, thenozzle204 is set in place by pushing ahollow shaft205 of thenozzle204 down into theorifice130 of thecap112 and then twisting thenozzle204 slightly, about one-quarter turn. Thenozzle204 is attached to thecap112 to prepare the mixingcartridge100 for placement into thedelivery gun500.
• The[0071]cap112 has a nipple206 protruding from anouter surface208 thereof. The nipple206 hastabs210, which engagedetent members212 in thenozzle204. After thenozzle204 is fully rotated into position, thetabs210 fully engage thedetent members212 while being positioned proximal to thedetent members212 to secure thenozzle204 in place. Astop214 on thecap112, best shown in FIG. 19, prevents thenozzle204 from rotating freely in the clockwise direction after thetabs210 have engaged thedetent members212. Thestop214 extends downwardly from one of thetabs210 to abut aside surface216 of one of thedetent members212 to prevent further clockwise rotation.
• The[0072]nozzle204 andcap112 have first218 and second220 locking protrusions. Thefirst locking protrusion218 acts as a detent and slides over thesecond locking protrusion220 to a locked position as illustrated in FIG. 21. In this position, rearflat surfaces222,224 of the lockingprotrusions218,220, abut one another to prevent thenozzle204 from being turned in the opposite direction, thereby preventing removal of thenozzle204 from thecap112. Thenozzle204 can be removed by deflecting anouter skirt226 of thenozzle204 and rotating thenozzle204 counterclockwise thereby disengaging the lockingprotrusions218,220. Both thenozzle204 andcap112 are formed from plastic, which facilitates the detent-like locking and unlocking of thenozzle204 to thecap112.
• With the[0073]nozzle204 in place, the mixingcartridge100 is ready to be placed within thedelivery gun500. Referring to FIG. 24, thedelivery gun500 of the present invention includes acradle502 for supporting the mixingcartridge100 and acasing504 fixed to thecradle502 for supporting adrive mechanism506, alinkage system508, and corresponding components. Thecradle502 includes anendplate510, which has anopening512 for receipt of thenozzle204. Theendplate510 holds the mixingcartridge100 in position in thecradle502. In the preferred embodiment, thecasing504 and theendplate510 are connected by two connecting bars514 (one on each side of the mixing cartridge100) to reduce the weight of thedelivery gun500. Ahandle516 is integrally formed with thecasing504 to maneuver thedelivery gun500 during use.
• To dispense the bone cement from the mixing[0074]cartridge100, thepiston114 must first be released from the locked position. Referring to FIG. 25, this is accomplished using arelease mechanism518 integrated into thedelivery gun500. Once the mixingcartridge100 is in place in thecradle502, aram disk520 protrudes into thecavity184 in thedistal end182 of thepiston114. Therelease mechanism518 is integrated into theram disk520. Therelease mechanism518 includes abearing surface522 forming an acute angle with the longitudinal axis L for catching therelease buttons200 to cam therelease buttons200 radially inwardly. More specifically, the cam surfaces202 of therelease buttons200 slide along the bearingsurface522, while being cammed radially inwardly. This action pulls the lockingtabs188 radially inwardly to withdraw the lockingtabs188 from theslots190 in thecylinder wall110 and release thepiston114 from the locked position (when thealternative piston314 is used, the ram disk has a flat bearing surface that axially presses thefingers400 proximally to bend eachresilient base392 inwardly and urge the lockingtabs388 radially inward). A centeringpin800 can be used to center theram disk520 in a centeringcavity802 of thepiston114 to facilitate the release of thepiston114 from the locked position.
• Referring back to FIG. 24, once the[0075]piston114 is released, thepiston114 can be driven through the mixingchamber108 by thedrive mechanism506 to force the bone cement from thenozzle204. Thedrive mechanism506 includes adrive rod524 movably supported bybushings526 in thecasing504. Theram disk520 is fixed to thedrive rod524. Thedrive mechanism506 further includes afirst gripper plate528 responsive to movement of thelinkage system508 upon actuation of atrigger530. Thefirst gripper plate528 defines an aperture surrounding thedrive rod524. Thefirst gripper plate528 frictionally engages thedrive rod524 to advance thedrive rod524. Thefirst gripper plate528 is urged forward while in frictional contact with thedrive rod524 by thelinkage system508 when thetrigger530 is actuated. Thefirst gripper plate528 thereby advances thedrive rod524 andram disk520 relative to thecasing504 to drive thepiston114 and force the bone cement from the mixingcartridge100. Thetrigger530 is pivotally supported by thecasing504 and operatively connected to thedrive mechanism506 to advance thedrive mechanism506 upon actuation of thetrigger530.
• The[0076]linkage system508 includes afirst link532, which is pivotally mounted to thecasing504 about a pivot axis A adjacent to thefirst gripper plate528. Thefirst link532 is adapted to engage thefirst gripper plate528 when thefirst link532 pivots about the pivot axis A. Asecond link536 pivotally interconnects thetrigger530 to thefirst link532 via support pins538,540. Thelinks532,536 and trigger530 are interconnected to move in unison upon rotation of thetrigger530 about a second pivot axis B. When thetrigger530 is pulled, thesecond link536 rotates thefirst link532 about the pivot axis A, which engages thefirst gripper plate528 and urges thefirst gripper plate528 forward while thefirst gripper plate528 is in frictional engagement with thedrive rod524 thereby advancing thedrive rod524. Areturn spring542 returns thelinks532,536 and thetrigger530 to an initial position upon release of thetrigger530. At the same time, afirst spring534 momentarily disengages thefirst gripper plate528 from thedrive rod524 to slide thefirst gripper plate528 back to an initial position to await the next pull of thetrigger530. Thecasing504 pivotally supports thefirst link532 and thetrigger530 about the pivot axes A and B via support pins544,546.
• A speed-changing[0077]link548 is pivotally connected to thesecond link536 about asupport pin549. The speed-changinglink548 selectively pivots into and out from engagement with thefirst gripper plate528 by way of aswitch550. The speed-changinglink548 pivots between a high-speed position and a low-speed position about the support pin549 (the low-speed position is shown in FIG. 24). The high-speed position corresponds to faster advancement of thedrive rod524 at a lower force. This allows the user to quickly advance thedrive rod524 to drive thepiston114 and dispense high volumes of bone cement at low pressure. The low-speed position corresponds to slower advancement of thedrive rod524 at a higher force, which exerts more force on thepiston114 to pressurize the bone cement.
• The[0078]first gripper plate528 and the speed-changinglink548 have complementary first andsecond coupling devices552,554 used to couple thefirst gripper plate528 with the speed-changinglink548 in the high-speed position. More specifically, in the embodiment of FIG. 24, thefirst gripper plate528 has ashoulder552 that is received within achannel554 on the speed-changinglink548. The speed-changinglink548 engages theshoulder552 in the high-speed position. In the high-speed position, a user's gripping force is transmitted through thetrigger530 to thesecond link536 and the speed-changinglink548 to engage thefirst gripper plate528 and advance thedrive rod524. The speed-changinglink548 is isolated from thefirst gripper plate528 in the low-speed position. The low-speed position corresponds to the speed-changinglink548 being switched or disconnected from theshoulder552. In the low-speed position, the user's gripping force is transmitted through thetrigger530 to both the first532 and second536 links to engage thefirst gripper plate528 and advance thedrive rod524. This results in slower advancement of thedrive rod524, but at a much higher mechanical advantage than the high-speed position. As a result, the user can better pressurize the bone cement during injection.
• The pivot axes A and B and the[0079]links532,536,548 are positioned above thedrive rod524, while thetrigger530 extends below thedrive rod524. Achannel556 defined in thetrigger530 facilitates this configuration. There are several advantages to this configuration. Moving the second pivot axis B away from a user's hand results in better usage of the stronger index and ring fingers by allowing those fingers more travel distance as thetrigger530 is actuated. This configuration also allows thehandle516 to be closer to thedrive rod524, which is believed to reduce wrist strain when the user pushes thedelivery gun500 forward during cement pressurization. Another benefit is that it allows for a more streamlined casing design and better weight distribution.
• In one embodiment, shown in FIG. 24, a[0080]secondary gripper plate562 is mounted about thedrive rod524 adjacent to thefirst gripper plate528. The addition of one or moresecondary gripper plates562 to thefirst gripper plate528 adds strength to thedelivery gun500 while still permitting proper operation. By using two ormore gripper plates528,562, increased frictional contact with thedrive rod524 is obtained without adversely affecting performance.
• A[0081]release pin558 disengages thegripper plates528,562 to allow a user to freely move thedrive rod524 by hand. Therelease pin558 is connected to aretainer plate560 and is adapted to engage thefirst gripper plate528. When theretainer plate560 is pushed by the user, therelease pin558 engages thefirst gripper plate528 which forces thefirst gripper plate528 to tilt back against the bias of thefirst spring534 thus releasing thedrive rod524. Anysecondary gripper plates562 follow. As should be appreciated, pushing theretainer plate560 also pivots theretainer plate560 releasing its engagement with thedrive rod524. With both theretainer plate560 and thegripper plates528,562 released, thedrive rod524 is free to move. This allows the user to manually move thedrive rod524 with respect to thecasing504.
• The[0082]delivery gun500 is unique among bone cement guns with a friction-plate mechanism in the way that it handles wear and deformation of thegripper plates528,562. In the disclosed embodiments, thegripper plates528,562 are tilted by thefirst spring534 into frictional contact with thedrive rod524. Regardless of the amount of wear or deformation of thegripper plates528,562 or thedrive rod524, thegripper plates528,562 require no further tilting to engage thedrive rod524 upon actuation of thetrigger530. Thus, advancement of thedrive rod524 is produced over the entire actuation of thetrigger530 and efficiency is maintained throughout the life of thedelivery gun500.
• Referring to FIGS. 24A and 24B, alternatives of the[0083]linkage system508′ and508″ are shown. These alternatives are represented with similar numerals to the embodiment of FIG. 24 to indicate like parts. FIG. 24A illustrates a configuration of thelinkage system508′ in which thelinkage system508′ lies beneath thedrive rod524′. Furthermore, the speed-changinglink548′ in this embodiment is pivotally connected to thefirst gripper plate528′ and includes a hook-shaped end to engage thesupport pin538′ in the high-speed position and disengage thesupport pin538′ in the low-speed position. FIG. 24B illustrates a configuration of thelinkage system508″ in which thefirst gripper plate528″ is pushed by thelinkage system508″, as opposed to being pulled by thelinkage system508 and508′ in FIGS. 24 and 24A. Here, the speed-changinglink548″ is pivotally connected to thefirst gripper plate528″ to pivot into engagement with anotch555″ defined in thetrigger530″ in the high-speed position and out from engagement with thenotch555″ in the low-speed position. These alternatives of thelinkage system508′ and508″ illustrate the flexibility of design, e.g., the selection of mechanical advantage, provided by the linkage system of the present invention.
• Referring to FIGS. 26-27, an alternative embodiment of the[0084]drive mechanism606 andlinkage system608 is shown (only a portion of thedrive mechanism606 andlinkage system608 is shown for illustrative purposes). In this embodiment, thelinkage system608 comprises the same components as previously described with an improvedfirst link632 andgripper plates628,662. In this embodiment, a plurality ofsecondary gripper plates662 are aligned along thedrive rod624 next to thefirst gripper plate628. Thefirst link632 defines afemale recess664 and thefirst gripper plate628 includes amale member668 for mating engagement with thefemale recess664. Thesecondary gripper plates662 are aligned relative to thefirst gripper plate628 viamating notches670 and pegs672 formed therein. Thenotches670 and pegs672 assume the same shape to mate with one another and maintain alignment. This arrangement minimizes alignment changes that may cause slipping or uneven wear. The arrangement also reduces contact between thegripper plates628,662 and an interior wall of thecasing504. Thegripper plates628,662 are shown spaced in FIG. 26 for illustration only. In practice, thegripper plates628,662 abut one another, as shown in FIG. 27.
• In this embodiment, each of the[0085]gripper plates628,662 also defines a pair ofsemi-spherical grooves674. In FIG. 26, only the first of the pair ofgrooves674 are shown in each of thegripper plates628,662. The other of the pair ofgrooves674 is located in a rear surface of each of thegripper plates628,662, cater-cornered from the first of the pair ofgrooves674. Thesegrooves674 increase the frictional contact with thedrive rod624. When thegripper plates628,662 are urged forward while in frictional engagement with thedrive rod624 by thefirst link632, a substantial portion of arim676 defined by each of thegrooves674 frictionally contacts thedrive rod624.
• Referring to FIG. 27, autoclave sterilization of the[0086]delivery gun500 can create a tendency for thegripper plates628,662 to adhere to thedrive rod624 beyond their initial positions when thetrigger630 is released. In this situation thefirst spring634 cannot produce enough force to disengage thegripper plates628,662 from thedrive rod624, and thegripper plates628,662 do not return to their initial positions. FIG. 27 shows a way to prevent this condition. Astriker678, in the form of a downwardly protruding portion of thesecond link636, closely follows one of thegripper plates628,662 during actuation of thetrigger630. In the event that any of thegripper plates628,662 do not properly disengage thedrive rod624 upon release of thetrigger630, thestriker678 will contact thenotch670 in theclosest gripper plate628,662 and dislodge thegripper plate628,662 from thedrive rod624. Thefirst spring634 can then properly return thegripper plates628,662 to their initial positions.
• A coating has been added to an exterior of each of the[0087]gripper plates528,562,628,662 in FIGS. 24 and 26-27. The coating increases lubricity and corrosion resistance. This facilitates sliding between thegripper plates528,562,628,662 as they engage thedrive rod524,624. The coating also reduces corrosion due to autoclave sterilization that may cause thegripper plates528,562,628,662 to adhere to one another and prevent proper engagement with thedrive rod524,624. The coating used may be Electroless-Nickel with polytetrafluoroethylene (PTFE) or other like coatings possessing the same or similar properties.
• Referring to FIGS. 28-31, another alternative embodiment of the[0088]drive mechanism706 andlinkage system708 is shown. This embodiment also provides selective high-speed and low-speed advancement of thedrive rod724. Thisalternative drive mechanism706 eliminates the gripper plate by providingteeth780 on thedrive rod724. A cross-section of thedrive rod724 shows theteeth780 on a flatupper surface782, while alower surface784 is smooth and round. Thefirst link732, which in previous embodiments urged thefirst gripper plate528,628 forward with thedrive rod524,624, now pivotally supports afirst pawl member786. Thefirst pawl member786 is spring-biased into engagement with theteeth780.
• A[0089]second pawl member788 is pivotally supported by thesecond link736. Thesecond pawl member788 is pivotable between a high-speed position in which thesecond pawl member788 is spring-biased into engagement with theteeth780 to advance thedrive rod724, and a low-speed position in which thesecond pawl member788 is disengaged and isolated from theteeth780. In the low-speed position, thefirst pawl member786 advances thedrive rod724. The low-speed position is illustrated in FIGS. 28-29. In the high-speed position, with thesecond pawl member788 engaging theteeth780, thefirst pawl member786 remains in engagement with theteeth780, but only ratchets along theteeth780 as thesecond pawl member788 advances thedrive rod724. The high-speed position is illustrated in FIGS. 30-31. The principle of increasing mechanical advantage in the low-speed position relative to the high-speed position also applies in this embodiment.
• The[0090]switch750 is used to pivot thesecond pawl member788 out from engagement with theteeth780 of thedrive rod724 in the low-speed position (see FIGS. 28-29) and into engagement with theteeth780 in the high-speed position (see FIGS. 30-31). A switch similar to that shown in U.S. Pat. No. 5,431,654 to Nic, herein incorporated by reference, can be used for this purpose. Theswitch750 extends through thecasing704 and terminates in a button that is manipulated by a user to move thesecond pawl member788 between the high-speed and low-speed positions (see briefly FIGS. 41-42). This also applies to theswitch550 used to move the speed-changinglink548 in previous embodiments.
• In this embodiment, the[0091]retainer plate560 can be removed. In its place, a spring-biasednon-return pawl member790 retains thedrive rod724 in position upon advancement. Thedrive rod724 can be freely moved in thecasing704 by rotating thedrive rod724 one hundred and eighty degrees such that thepawl members786,788,790 are out of engagement with theteeth780. Upon such rotation, thepawl members786,788,790 ride on the smoothlower surface784 of thedrive rod724 allowing the user to freely pull thedrive rod724 relative to thecasing704. This is generally disclosed in the '654 patent to Nic.
• Each of the[0092]pawl members786,788,790 are pivotally supported by pins. Springs, such as those shown in the '654 patent to Nic, bias the pawl members into engagement with theteeth780 on the drive rod724 (except when theswitch750 acts against the bias of the spring in the low-speed position to disengage thesecond pawl member788 from the teeth780).
• Mixing and delivery of the bone cement will now be described with reference to FIGS. 32-42. Referring first to FIG. 32, a bone cement loading system is shown. The bone cement loading system comprises a base[0093]900 supporting thecylinder102 while loading the liquid and powder components of the bone cement into the mixingchamber108. The base includes a cavity for receiving thedistal end106 of thecylinder102.Detents903 are formed in the cavity. Agroove905 is defined in an outer surface of thecylinder102 to receive thedetents903 and facilitate a snug fit between the base900 and thecylinder102. It should be appreciated that thedetents903 could be formed on thecylinder102 with thegroove905 defined in thebase900. Thedistal end106 of thecylinder102 may also be press fit into thebase900. Thebase900 is oblong and oval in shape to fully support thecylinder102 on a work surface, while the cavity is circular in shape to fit the circular shapedcylinder102. Afunnel902 couples to thecylinder102 to channel the powder into thecylinder102 during loading. Thefunnel902 includes aproximal end911 having an oblong oval-shaped periphery to facilitate the loading of the powder into the mixingchamber108 and adistal end909 having a circular periphery to snugly fit inside theproximal end104 of thecylinder102.
• FIGS. 33-42 illustrate ten steps for preparing and injecting the bone cement. The mixing[0094]cartridge100,delivery gun500, and other components are generically shown in each step for illustrative purposes only.
• In[0095]STEP1, shown in FIG. 33, thefunnel902 is coupled to thecylinder102 and the powder is poured into the mixingchamber108.
• In[0096]STEP2, shown in FIG. 34, after the powder is poured into the mixingchamber108, thefunnel902 is removed, and the liquid component, e.g., liquid monomer, of the bone cement is added. In this manner, the present invention avoids wetting of thefunnel902 and the associated clean-up.
• In[0097]STEP3, shown in FIG. 35, thecap112 with the mixingshaft150 andblade152 supported therein is attached to thecylinder102.
• In[0098]STEP4, shown in FIG. 36, thevacuum line138 is attached to thevacuum port136 and a vacuum is drawn in the mixingchamber108 with the liquid and powder components therein.
• In[0099]STEP5, shown in FIG. 37, with the vacuum drawn, the power tool (reamer) is then connected to the mixingshaft150.
• In[0100]STEP6, shown in FIG. 38, with the vacuum still drawn, the mixingshaft150 is moved axially with respect to the mixingcartridge100 and rotated by the power tool. The blade152 (not shown in FIG. 38) is moved axially the entire extent of the mixingcartridge100 while rotating to ensure that the liquid and powder components are fully mixed.
• In[0101]STEP7, shown in FIG. 39, once mixed, therelease latch162 is moved to release the blade152 (not shown in FIG. 39). Theblade152 remains in the mixingchamber108 once released. The mixingshaft150 is then removed from the mixingcartridge100. Mixing is now complete.
• In[0102]STEP8, shown in FIG. 40, thenozzle204 is pushed down on thecap112 and rotated into place.
• In[0103]STEP9, shown in FIG. 41, the mixingcartridge100 is positioned in thecradle502.
• In STEP, shown in FIG. 42, the[0104]piston114 is released from thedistal end106 of thecylinder102 and thedelivery gun500 is primed and ready to discharge the bone cement from the mixingcartridge100.
• It will be appreciated that the above description relates to the disclosed embodiments by way of example only. Many apparent variations of the disclosed invention will be known to those of skill in this area and are considered to be within the scope of this invention and are considered to be within the scope of the following claims. Obviously, many modifications and variations of the present invention are possible in light of the above teachings.[0105]

Claims (72)

What is claimed is:

1. A mixing cartridge for receiving liquid and powder components of bone cement to be mixed for medical use, said mixing cartridge comprising:

a cylinder having proximal and distal ends and defining a mixing chamber therebetween for receiving the liquid and powder components of the bone cement, said cylinder including a cylinder wall extending between said ends about a longitudinal axis thereof and said cylinder wall defining at least one female portion at said distal end;

a piston disposed in said cylinder at said distal end;

a locking member coupled to said piston and including at least one male portion for mating with said at least one female portion in said cylinder wall to place said piston in a locked position in said distal end of said cylinder; and

said locking member including a resilient portion for biasing said at least one male portion into mating engagement with said at least one female portion in said cylinder wall whereby said piston remains in said locked position while mixing the liquid and powder components of the bone cement.

2. A mixing cartridge as set forth inclaim 1 wherein said female portion is further defined as at least one slot and said male portion is further defined as at least one locking tab protruding radially outwardly from said longitudinal axis into said at least one slot in said locked position.

3. A mixing cartridge as set forth inclaim 2 wherein said piston includes a proximal end and a distal end with a cavity defined in said distal end and said locking member is disposed in said cavity.

4. A mixing cartridge as set forth inclaim 2 wherein said at least one slot is further defined as a pair of diametrically opposed slots and said at least one locking tab is further defined as a pair of diametrically opposed locking tabs protruding radially outwardly into said slots in said cylinder wall under the bias of said resilient portion.

5. A mixing cartridge as set forth inclaim 4 wherein said resilient portion extends between said locking tabs to bias said locking tabs radially outwardly from said longitudinal axis of said cylinder.

6. A mixing cartridge as set forth inclaim 5 wherein said resilient portion is integral with said locking tabs and extends in a thin resilient ribbon between said locking tabs.

7. A mixing cartridge as set forth inclaim 6 wherein said piston defines a pair of carrier slots for receiving and axially securing said locking tabs when said piston is in said locked position and after said piston is released from said locked position.

8. A mixing cartridge as set forth inclaim 7 wherein said piston includes a step extending partially into each of said carrier slots and each of said locking tabs defines a channel partially extending therein for receiving said step when said piston is in said locked position and after said piston is released from said locked position.

9. A mixing cartridge as set forth inclaim 4 wherein said locking member includes a pair of release buttons for releasing said piston from said locked position.

10. A mixing cartridge as set forthclaim 9 wherein said release buttons are integrally formed with said locking tabs and said release buttons extend distally from said locking tabs to protrude distally from said piston.

11. A mixing cartridge as set forth inclaim 10 wherein each of said release buttons include a cam surface extending at an acute angle to said longitudinal axis of said cylinder with said cam surfaces being engageable to cam said release buttons radially inwardly toward said longitudinal axis to withdraw said locking tabs from said slots in said cylinder wall and release said piston from said locked position.

12. A mixing cartridge as set forth inclaim 2 wherein said at least one slot is further defined as a plurality of slots and said at least one locking tab is further defined as a plurality of locking tabs protruding into said slots in said locked position.

13. A mixing cartridge as set forth inclaim 12 wherein said resilient portion is further defined as a resilient base resiliently supporting each of said plurality of locking tabs on said piston with each of said locking tabs being radially biased outwardly from said piston to engage said slots in said cylinder wall.

14. A mixing cartridge as set forth inclaim 13 wherein said locking member includes a plurality of release buttons for releasing said piston from said locked position.

15. A mixing cartridge as set forth inclaim 14 wherein said release buttons are integrally formed with said tabs.

16. A mixing cartridge as set forth inclaim 15 wherein said release buttons are further defined as fingers extending radially inwardly toward said longitudinal axis of said cylinder with said fingers being engageable to urge said locking tabs radially inwardly and withdraw said locking tabs from said slots in said cylinder wall to release said piston from said locked position.

17. A mixing cartridge as set forth inclaim 1 including a cap sealed to said cylinder at said proximal end.

18. A mixing cartridge for use with a delivery device having a release mechanism to discharge bone cement from the mixing cartridge, said mixing cartridge comprising:

a cylinder having proximal and distal ends and defining a mixing chamber therebetween for receiving liquid and powder components of the bone cement, said cylinder including a cylinder wall extending between said ends about a longitudinal axis thereof and said cylinder wall including one of a male portion or a female portion at said distal end;

a piston disposed in said cylinder at said distal end;

a locking member coupled to said piston and including the other of said male portion or said female portion for engaging said male portion or said female portion of said cylinder wall to place said piston in a locked position in said distal end of said cylinder; and

said locking member including at least one release button for being engaged by the release mechanism of the delivery device to disengage said male and female portions and release said piston from said locked position.

19. A mixing cartridge as set forth inclaim 18 wherein said cylinder wall includes said female portion and said female portion is further defined as at least one slot and said locking member includes said male portion with said male portion being further defined as at least one locking tab protruding radially outwardly from said longitudinal axis into said at least one slot in said locked position.

20. A mixing cartridge as set forth inclaim 19 wherein said at least one slot is farther defined as a pair of diametrically opposed slots and said at least one locking tab is further defined as a pair of diametrically opposed locking tabs protruding radially outwardly into said slots in said cylinder wall under the bias of said resilient portion.

21. A mixing cartridge as set forth inclaim 20 wherein said locking member includes a resilient portion extending between said locking tabs to bias said locking tabs radially outwardly from said longitudinal axis.

22. A mixing cartridge as set forth inclaim 20 wherein said at least one release button is further defined as a pair of release buttons for being engaged by the release mechanism of the delivery device to release said piston from said locked position.

23. A mixing cartridge as set forthclaim 22 wherein said release buttons are integrally formed with said locking tabs and said release buttons extend distally from said locking tabs to protrude distally from said piston.

24. A mixing cartridge as set forth inclaim 23 wherein each of said release buttons include a cam surface extending at an acute angle to said longitudinal axis of said cylinder with said cam surfaces being engageable to cam said release buttons radially inwardly toward said longitudinal axis to withdraw said locking tabs from said slots in said cylinder wall and release said piston from said locked position.

25. A delivery gun for receiving a cartridge containing bone cement to deliver the bone cement to an anatomical site by discharging the bone cement from the cartridge, said delivery gun comprising:

a casing;

a drive mechanism supported by said casing and advanceable relative to said casing to discharge the bone cement from the cartridge;

a trigger pivotally supported by said casing and operatively connected to said drive mechanism to actuate said drive mechanism upon actuation of said trigger; and

a linkage system operatively interconnecting said trigger with said drive mechanism to actuate said drive mechanism, said linkage system comprising a first link pivotally connected to said casing and a second link pivotally interconnecting said first link and said trigger such that actuating said trigger moves said second link and said first link to actuate said drive mechanism and advance said drive mechanism to discharge the bone cement from the cartridge.

26. A delivery gun as set forth inclaim 25 wherein said drive mechanism includes a drive rod supported by said casing.

27. A delivery gun as set forth inclaim 26 wherein said drive mechanism further includes a first gripper plate responsive to movement of said linkage system upon actuation of said trigger wherein said first gripper plate defines an aperture surrounding said drive rod and said first gripper plate frictionally engages said drive rod to advance said drive rod when said trigger is actuated.

28. A delivery gun as set forth inclaim 27 including a speed-changing link pivotally supported by one of said drive mechanism or said linkage system for pivoting between a high-speed position and a low-speed position.

29. A delivery gun as set forth inclaim 28 wherein said first gripper plate includes a first coupling device and said speed-changing link defines a second coupling device for coupling with said first coupling device in said high-speed position with said speed-changing link being isolated from said first gripper plate in said low-speed position.

30. A delivery gun as set forth inclaim 29 wherein said first coupling device is a shoulder and said second coupling device is a channel for engaging said shoulder in said high-speed position.

31. A delivery gun as set forth inclaim 27 including a second gripper plate aligned with said first gripper plate to increase frictional contact with said drive rod to advance said drive rod.

32. A delivery gun as set forth inclaim 31 wherein said second gripper plate includes a peg engaging a notch in said first gripper plate to align said second gripper plate with said first gripper plate.

33. A delivery gun as set forth inclaim 32 including a spring positioned over said drive rod between said casing and said gripper plates to bias said gripper plates into frictional engagement with said drive rod.

34. A delivery gun as set forth inclaim 26 wherein said drive rod includes a plurality of teeth along a length thereof.

35. A delivery gun as set forth inclaim 34 wherein said drive mechanism includes at least one pawl member for engaging said teeth to advance said drive rod.

36. A delivery gun as set forth inclaim 34 wherein said drive mechanism includes a pair of pawl members for engaging said teeth to advance said drive rod.

37. A delivery gun as set forth inclaim 36 wherein said pawl members are further defined as a first pawl member and a second pawl member with said first pawl member being pivotally supported by said linkage system and said second pawl member being pivotally supported by said linkage system for moving between a high-speed position in which the second pawl member engages said teeth and a low-speed position in which said second pawl member is isolated from said teeth.

38. A delivery gun as set forth inclaim 37 including biasing devices for biasing each of said pawl members into engagement with said teeth on said drive rod.

39. A delivery gun as set forth inclaim 38 including a switch engaging said second pawl member to move said second pawl member between said high speed and said low speed positions.

40. A delivery gun as set forth inclaim 39 wherein said trigger is pivotally supported by said casing about a pivot axis and said pivot axis is positioned above said drive rod while said trigger extends downwardly below said drive rod with said trigger defining a channel therethrough for receiving said drive rod.

41. A delivery gun as set forth inclaim 40 wherein said first and second links are positioned above said drive rod.

42. A delivery gun as set forth inclaim 26 wherein said drive mechanism includes a ram disk fixed to said drive rod to discharge the bone cement from the cartridge and said ram disk includes a release mechanism for releasing a piston of the cartridge from a locked position.

43. A delivery gun as set forth inclaim 42 wherein said release mechanism includes a bearing surface for engaging release buttons on the piston to cam the release buttons radially inwardly and release the piston from the locked position.

44. A delivery gun for receiving a cartridge containing bone cement to deliver the bone cement to an anatomical site by discharging the bone cement from the cartridge, said delivery gun comprising:

a casing;

a drive rod supported by said casing and advanceable relative to said casing to discharge the bone cement from the cartridge;

a trigger pivotally supported by said casing; and

a first gripper plate responsive to actuation of said trigger wherein said first gripper plate surrounds said drive rod and frictionally engages said drive rod to advance said drive rod when said trigger is actuated.

45. A delivery gun as set forth inclaim 44 including at least one second gripper plate aligned with said first gripper plate about said drive rod to increase frictional contact with said drive rod when advancing said drive rod upon actuation of said trigger.

46. A delivery gun as set forth inclaim 45 wherein said at least one second gripper plate includes a peg and said first gripper plate defines a notch for receiving said peg to align said at least one second gripper plate with said first gripper plate.

47. A delivery gun as set forth inclaim 44 including a linkage system operatively interconnecting said trigger with said first gripper plate, said linkage system comprising a first link pivotally connected to said casing and a second link interconnecting said first link and said trigger whereby actuating said trigger moves said second link and said first link to engage said first link with said first gripper plate and advance said drive rod to discharge the bone cement from the cartridge.

48. A delivery gun as set forth inclaim 47 wherein said second link includes a striker extending downwardly therefrom for engaging said first gripper plate to dislodge said first gripper plate from said drive rod when said first gripper plate does not return to an initial position upon release of said trigger.

49. A delivery gun as set forth inclaim 44 including a spring positioned over said drive rod between said casing and first gripper plate to bias said first gripper plate into frictional engagement with said drive rod.

50. A delivery gun as set forth inclaim 45 including a coating applied to each of said gripper plates to increase lubricity and corrosion resistance.

51. A delivery gun as set forth inclaim 50 wherein said coating is electroless-nickel with polytetrafluoroethylene.

52. A bone cement mixing and delivery system for combining liquid and powder components of bone cement and delivering the bone cement to an anatomical site of a patient, said system comprising:

a cartridge comprising;

a cylinder having proximal and distal ends and defining a mixing chamber therebetween with said cylinder including a cylinder wall extending between said ends about a longitudinal axis thereof,

a piston releasably secured in said cylinder at said distal end, and

a locking member for releasably securing said piston in a locked position at said distal end with said locking member including at least one release button for releasing said piston from said locked position,

in combination with a delivery device adapted to hold said cartridge comprising;

a casing, and

a drive mechanism supported by said casing and advanceable relative to said casing to discharge the bone cement from said cartridge wherein said drive mechanism includes a release mechanism for engaging said at least one release button to release said piston from said locked position.

53. A bone cement mixing and delivery system as set forth inclaim 52 wherein said cylinder wall defines a plurality of slots at said distal end and said locking member includes a plurality of locking tabs radially protruding outwardly into said slots in said locked position.

54. A bone cement mixing and delivery system as set forth inclaim 53 wherein said at least one release button is further defined as a plurality of release buttons for releasing said piston from said locked position.

55. A bone cement mixing and delivery system as set forth inclaim 54 wherein each of said release buttons include a cam surface extending at an acute angle to said longitudinal axis of said cylinder with said cam surfaces being engagable by said release mechanism to cam said buttons radially inwardly to withdraw said locking tabs from said slots in said cylinder wall and release said piston from said locked position.

56. A bone cement mixing and delivery system as set forth inclaim 55 wherein said release mechanism includes a bearing surface for engaging said cam surfaces of said release buttons to cam said release buttons radially inwardly and release said piston from said locked position.

57. A bone cement mixing and delivery system as set forth inclaim 54 wherein said plurality of release buttons are further defined as fingers extending radially inwardly toward said longitudinal axis of said cylinder with said fingers being engagable by said release mechanism to urge said locking tabs radially inwardly and withdraw said locking tabs from said slots in said cylinder wall to release said piston from said locked position.

58. A bone cement loading system for receiving liquid and powder components of bone cement to be mixed for medical use, comprising:

a cylinder having an open proximal end and a closed distal end and defining a mixing chamber between said ends;

a piston locked in said cylinder to define said closed distal end;

a base defining a cavity for receiving and securing said closed distal end of said cylinder to support said cylinder while loading the liquid and powder components therein;

a funnel for coupling to said open proximal end of said cylinder to channel the powder component of the bone cement into said mixing chamber, said funnel having a proximal end and a distal end wherein said distal end has a circular periphery for snugly fitting into said open proximal end of said cylinder and said proximal end has an oblong oval-shaped periphery to facilitate the transfer of the powder component of the bone cement into said mixing chamber.

59. A bone cement loading system as set forth inclaim 58 wherein said base is oblong in shape and said cavity is circular in shape.

60. A bone cement loading system as set forth inclaim 59 wherein one of said base and said cylinder includes a plurality of detents and the other of said base and said cylinder defines a groove in a surface thereof for releasably receiving said detents to facilitate a snug fit between said base and said cylinder.

61. A bone cement mixing system for mixing liquid and powder components of bone cement for medical use, comprising:

a cartridge including a cylinder having proximal and distal ends and defining a mixing chamber between said ends;

a mixing shaft rotatably supported by said cartridge for rotation about an axis and including a portion extending outside of said mixing chamber; and

a blade operatively connected to said portion and disposed in said mixing chamber for rotating with said mixing shaft about said axis to mix the liquid and powder components of the bone cement, said blade including a center hub coupled to said mixing shaft and an outer ring extending from said center hub wherein said outer ring forms an acute angle with said axis and said acute angle is between twenty and seventy degrees to ensure adequate mixing of the bone cement.

62. A bone cement mixing system as set forth inclaim 61 wherein said blade is adapted to remain in said mixing chamber after mixing is complete and said portion of said mixing shaft extending outside of said mixing chamber is adapted to be removed from said operative connection with said blade after mixing.

63. A bone cement mixing system as set forth inclaim 61 wherein said blade has an effective height that is greater than one quarter inch to further ensure adequate mixing of the bone cement.

64. A bone cement mixing system as set forth inclaim 63 wherein said blade is flexible and adapted to flatten in said mixing chamber such that said effective height of said blade is reduced and said acute angle is increased to approximately ninety degrees to minimize axial space occupied by said blade in said mixing chamber.

65. A bone cement mixing system as set forth inclaim 61 wherein said blade has an effective height that is approximately one half inch and said acute angle is approximately sixty degrees to ensure adequate mixing of the bone cement.

66. A bone cement mixing system as set forth inclaim 61 including a plurality of radially inwardly protruding fingers attached to said outer ring wherein one of said plurality of fingers protrudes radially inwardly in a first plane and another of said plurality of fingers protrudes radially inwardly in a second plane spaced from and parallel to said first plane.

67. A bone cement mixing system as set forth inclaim 61 including a protruding node attached to said outer ring and protruding radially outwardly to control spacing between said blade and an inner periphery of said cylinder by scraping along said inner periphery of said cylinder.

68. A method of mixing liquid and powder components of bone cement in a mixing chamber of a mixing cartridge using a rotary power tool with a portion of a mixing shaft extending outside of the mixing chamber to connect to the rotary power tool and a blade being operatively connected to the portion and disposed within the mixing chamber to mix the liquid and powder components of the bone cement, said method comprising the steps of:

connecting the rotary power tool to the portion of the mixing shaft extending outside of the mixing chamber;

actuating the rotary power tool once connected to the portion of the mixing shaft to rotate the blade and mix the liquid and powder components of the bone cement;

displacing the rotary power tool during actuation relative to the mixing cartridge to completely mix the liquid and powder components of the bone cement; and

removing the operative connection between the blade and the portion of the mixing shaft extending outside of the mixing chamber once mixing is complete.

69. A method as set forth inclaim 68 wherein removing the operative connection between the blade and the portion of the mixing shaft extending outside of the mixing chamber is further defined as releasing the blade from the mixing shaft.

70. A method as set forth inclaim 69 wherein axially displacing the rotary power tool during actuation includes moving the rotary power tool both proximally and distally during actuation to completely mix the liquid and powder components of the bone cement.

71. A method as set forth inclaim 68 wherein removing the operative connection between the blade and the portion of the mixing shaft extending outside of the mixing chamber is further defined as severing the portion of the mixing shaft extending outside of the mixing chamber.

72. A method as set forth inclaim 68 wherein displacing the rotary power tool during actuation relative to the mixing cartridge is further defined as axially displacing the rotary power tool during actuation relative to the mixing cartridge.

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