Patent Publication Number: US-2013231609-A1

Title: Device for mixing and delivering fluids for tissue repair

Description:
RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. §120 of U.S. application Ser. No. 11/883,985, entitled “DEVICE FOR MIXING AND DELIVERING FLUIDS FOR TISSUE REPAIR” filed on Jul. 3, 2008, which is herein incorporated by reference in its entirety. Application Ser. No. 11/883,985 is a National Stage Application of PCT/US2006/004445 which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application Ser. No. 60/651,329, entitled “DELIVERY DEVICE FOR TISSUE REPAIR” filed on Feb. 9, 2005, which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a device for mixing and delivering viscous fluids for tissue repair, and more particularly, to a device for arthroscopically delivering a scaffold of platelet rich plasma and collagen mixture to repair the tissue. 
     2. Description of the Related Art 
     Over half a million people in the U.S. suffer an intra-articular injury every year. Approximately 100,000 of the injuries are due to a tear in the anterior cruciate ligament (ACL) in the knee. Over 500,000 injuries are caused by meniscal tears. 
     Various procedures have been developed to repair a damaged ligament. For example, one method of repairing a torn or ruptured ACL requires a tunnel to be drilled in both the tibia and the femur. A substitute ACL graft is inserted to extend from one tunnel to another and the ends of the graft are secured to the walls of the tunnel using interference screws or the like. The necessary incisions are large and invasive. Procedure and recovery times for such a procedure are extensive. 
     Biologically, the ACL and other intra-articular tissues do not heal easily. Typically, the ACL has an impaired response to the injury. Blood clots, which are the foundation for the healing, cannot form in the knee joint. Moreover, physical reconstruction is difficult. One reason is the elasticity. An ACL has a Young&#39;s modulus of approximately 1 GPa. For reference, steel has a typical modulus of approximately 200 GPas. 
     Another problem with traditional joint tissue repair procedures, including treatment of the ACL, meniscus and articular cartilage are the amount of instruments, and incisions therefor, that are required. In addition to the surgical instruments, the physician may also need to use an arthroscope to view the surgical field. The instrumentation is costly. 
     Thus, there is a need to provide a more simple, less invasive and enhanced procedure to repair injured tissue. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention is to enhance tissue repair by using a bioactive scaffold, which stimulates healing of the tissues. 
     Another aspect of the present invention is to deliver the scaffold arthroscopically using a minimally invasive technique that will decrease operative complications and speed patient recovery. 
     Yet another aspect of the present invention is to provide a scaffold that has been thoroughly mixed and delivered at a precise viscosity and temperature. 
     Still another aspect of the invention is to mix and dispense the scaffold with a device that is easy to maneuver, control and use in a sterile environment. 
     In accomplishing these and other aspects of the present invention there is provided a device for mixing and delivering a mixture of fluids to a target site. The device includes a tube for containing the mixture. The tube has a proximal and a distal end. A compressible auger for mixing the fluids is movably disposed within the tube, one end of the auger being free at the distal end of the tube. A plunger is also movable within the tube. A first end of the plunger is in communication with the other end of the auger and a second end of the plunger extends from the proximal end of the tube. When the plunger is moved axially within the tube the auger also moves axially and the auger is compressed. 
     In accomplishing these and other aspects of the present invention there is also provided a device to be disposed on an arthroscopic sheath for mixing and delivering viscous fluids for the arthroscopic repair of tissue. The device includes a secondary elongated sheath removably disposed along an axial length of the arthroscopic sheath and has opposed ends. One of the ends of the secondary sheath has a tip located at an operating end of the arthroscopic sheath. 
     In accomplishing these and other aspects of the present invention there is provided a device for mixing and delivering viscous fluids for the repair of tissue. The device includes a barrel having opposed ends. A mixing and delivery device is disposed on the barrel in communication with the injector. The mixing and delivery device includes a tube for containing the fluids. An auger is movably disposed within a mixing chamber of the tube for mixing the fluids. A plunger is movably disposed within the tube for delivering a mixture of the fluids to an injector. A handle is disposed at the other end of the barrel. A trigger mechanism is movably mounted on the barrel for actuating the plunger to move the same within the tube to deliver the mixture to the injector. A dryer mechanism is located in the barrel in communication with the injector for removing excess fluid from the injury site. A heater located on the barrel heats one or more of the fluids. 
     There is also provided a method for repairing an injured tissue including the steps of providing a tube having a plunger movably disposed therein for receiving a plurality of fluids to be mixed. The tube has a mixing chamber for containing the fluids, and a collapsible auger movably disposed within the mixing chamber of the tube for mixing the fluids. An injector is attached at one end of the tube, the injector being in fluid communication with the mixing chamber. The mixing chamber of the tube is loaded with a desired amount of each of the fluids. The auger is rotated to mix the fluids. The mixture of fluids is heated and the injury site is dried to remove any excess moisture. The injector is inserted into the patient and the mixture is injected through the injector to the injury site. 
     These and other features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiment relative to the accompanied drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates the healing process of an injured tissue according to the present invention. 
         FIG. 2  is a cross-sectional view of the mixing and delivery device of the present invention. 
         FIG. 3  is a perspective view of the mixing tube of the present invention. 
         FIG. 4  is a cross-sectional view of the tube of  FIG. 3  taken along line I-I. 
         FIG. 5  is a side view of the mixing element of the present invention. 
         FIG. 6  is a perspective view of the mixing element of  FIG. 5 . 
         FIG. 7  is a cross-sectional view of the mixing element taken along line II-II of  FIG. 6 . 
         FIG. 8A  illustrates one embodiment of the fluid distribution of the present invention. 
         FIG. 8B  illustrates another embodiment of the fluid distribution of the present invention. 
         FIG. 9  is a perspective view of an embodiment of the delivery and mixing device for an arthroscopic sheath. 
         FIG. 10  is a cross-sectional view of the primary and secondary sheaths taken along line III-III of  FIG. 9 . 
         FIGS. 11A-11E  are different embodiments of the tip of the secondary sheath of  FIG. 9 . 
         FIG. 12  is a top view of the mixing and delivery device disposed within a heating or cooling element. 
         FIG. 13  is a perspective view of yet another embodiment of a mixing and delivery device of the present invention. 
         FIG. 14  is a back view of the device of  FIG. 13 . 
         FIG. 15  is a perspective view of the device of  FIG. 13  with the cover of the handle removed. 
         FIGS. 16A and 16B  illustrate an alternative embodiment of a mixing and delivery device according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention relates to enhancing tissue repair by using a bioactive scaffold that stimulates healing of the tissue, for example, an ACL. The scaffold consists of a viscous fluid mixture of platelets rich plasma (PRP) and soluble collagen gel. Together the mixture forms a glue, which when delivered arthroscopically to the injury fills the wound site and serves as a provisional scaffold on which healing can proceed. As shown in  FIG. 1  ( a )-( d ), the mixture of fluids is delivered to a rupture in the ligament. The mixture includes platelets and collagen. Collagen can be made from tissue rich in collagen including ligament, tendon, skin, fascia, or scar tissue. The mixture acts as a bridge to glue the tear. Cells invade the mixture and eventually the tear heals. Although the fluid mixture is described as platelet rich plasma and collagen, it should be appreciated that other fluids, gels and mixtures are contemplated by the present invention. 
     The present invention provides an enhanced arthroscopic device and system for repairing a ligament or other injured tissue in a sterile environment. Two or more viscous fluids are blended to a microscopic level. Viscosity control requires that the injected fluid not be too runny as to drip off of the ligament, but not to viscous as to be damaged on injection. 
     Referring to  FIG. 2 , a delivering and mixing device  10  includes a hollow tube or syringe  12 , a mixing element  14  and a plunger  16 . As will be described further herein, mixing element  14  and plunger  16  are axially and rotatably movable within tube  12 . A mixture of fluids  20  is contained in a mixing chamber  18  formed by the sealed engagement of plunger  16  and an inner diameter of tube  12 . 
     As shown in  FIGS. 3 and 4 , tube  12  has a proximal end  22  and a distal end  24 . Proximal end  22  is sized to receive mixing element  14  and plunger  16 . Located at distal end  24  is a discharge opening  26  that communicates with mixing chamber  18 . As will be described further herein, when auger  14  and plunger  16  are moved axially within tube  12  toward end  24  the mixture contained within chamber  18  is dispensed through discharge opening  26 . 
     In one embodiment mixing element  14  is a collapsible or compressible auger. Auger size, clearance and pitch are chosen to optimize auger geometry. Tooth profile, lead angle, thickness, width, clearance and length are some key mixing parameters. For example, a lead angle of 5-10 rotations per inch with a tall, narrow tooth profile is acceptable. Further optimization of such parameters can reduce the mixing time below 20-30 seconds. 
     The collapsible auger is derived from a rectangular cross-section spring. As will be described further herein, it is attached at the front of the plunger, and free to move axially at the other end. The torsional stiffness of the spring allows it to resist loading from the mixing of the fluids without significant deformation. Unlike a conventional auger, however, it can be compressed by a plunger from behind. This eliminates a significant portion of the dead volume between the threads of the auger, and so maximizes the amount of injected fluid. As shown in  FIG. 2 , the plunger seals both the outer casing, and the auger shaft to prevent leakage of the fluid. The auger shaft is constrained axially, so movement of the plunger pushing on the free end of the auger acts to compress it. 
     A number of additional active-type mixing elements are available. Active mixing uses a moving element inside the fluid reservoir to force the fluids to interact. In this strategy, the mixing quality is determined by the length of time and type of moving element. These include helical impellers, anchors, open impellers, whips and the mechanical equivalents thereof. Helical impellers are of a spiral-type design with a relatively large surface area, and include augers. Anchors resemble a fisherman anchor, with two arms forming a u-shape. Impellers have a similar shape as propellers, but are used for internal flow. Whips can be mixing elements having an eccentric mixing portion. Once again it should be appreciated that the present invent contemplates passive and vibrational mixing, as well as the above-described active mixing. 
     Passive mixing uses a dividing helix, or similar device, to mix the fluid as it flows through a tube. In this strategy, the mixing quality is determined by the length and fineness of the mixing section. Vibrational mixing can include the introduction of metal spheres into a mixing tube, with a vibrator on the outside. The vibrator forces the spheres to shake and mix the fluids. Another type of vibration mixing is vortex shaking and is considered the medical industry standard for mixing low viscosity fluids. 
     Referring to  FIG. 5 , mixing element or auger  14  has a first end  32  and a second end  34 . When auger  14  is located within tube  12 , end  32  is freely disposed at distal end  24  of the tube. End  34  of the auger can be fixed to a first end  36  of plunger so that auger  14  is integrally formed with plunger  16 . It should be appreciated that elements  14  and  16  can be formed separately as well and attached together via other conventional manners. The other end  38  of plunger  16  extends from proximal end  22  of tube  12 . 
     Referring back to  FIG. 2 , there is limited clearance between the outer diameter of auger  14  and the tube inner diameter. A fluid return path exists therebetween and ensures that the fluids did not remain stratified. As shown in  FIGS. 6 and 7 , auger  14  also includes an internal discharge passage  40  that extends along its axial length. Discharge passage  40  also acts as a fluid passage for the mixture. The outer diameter of discharge passage  40  may be less than an inner diameter of tube discharge opening  26 . 
     When plunger  16  is activated and moved axially toward the discharge opening of the tube free end  32  of the auger abuts against distal end  24  of the tube and the auger is compressed or collapsed to discharge the mixture from tube  12 . To prevent leakage of the mixture during dispensing at least one seal  28 , such as an o-ring, can be located between the plunger and an inner diameter of the tube. 
     In addition to pushing the mixture from tube  12 , displacing the mixture by blowing a secondary fluid can also be done. Moreover, squeezing the mixture by using a reduction in a flexible container volume by a applying a force on the outside is contemplated. Pumping is another mixture delivery method, as is spinning the auger backwards. This would force the fluid towards the front of the auger and out of the tube. 
     In addition to being axially movable within tube  12 , auger  14  and plunger  16  are also rotatable within the tube. As shown in  FIG. 5 , plunger  16  includes a shaft  30  that extends from end  38 . Shaft  30  is connected to a motor to rotate the same. The auger and plunger can be driven by a small motor, for example, a Mabuchi RE-260 hobby motor with a 5.25:1 gear reduction. 
     An injector  42  ( FIG. 9 ), such as a needle, is located in the discharge opening  26  of the tube. The mixing chamber of tube  12  can be preloaded with a quantity of a first fluid component, for example, collagen. The tube or syringe can be capped and the assembly placed in a sterile pack or kit. Later, for example at an operation site, platelets can be extracted from the patient immediately prior to the procedure and the platelets and plasma delivered to the mixing chamber by uncapping the tube and inserting the injector into the fluid and drawing the fluid through the injector by movement of the plunger. In another embodiment, the mixing chamber of the syringe could have two compartments separated by a membrane. One of the compartments could be loaded with unneutralized collagen and one with a neutralization solution. When the membrane is broken, for example by the spinning motion of the mixing element. Alternatively, the membrane could be made of a dissolvable material, such as a material that dissolves at room temperature. Upon disruption of the membrane, the two fluids could be mixed, for example, just before drawing in the PRP. Additionally, the plunger could be activated to move only half-way to draw up one component, and then drawn completely up to add the second component. Alternatively, the fluid could be tapped down and air purged before drawing in the other fluid. 
     Alternatively and as shown in  FIG. 8A , the fluids can be each disposed in sealed vial(s) or cartridges  44 . One cartridge can contain the collagen and/or gel and another cartridge, platelets or the platelet rich plasma. In one embodiment, the mixing and delivery device can be sequentially inserted into the vials and the desired quantity of fluid drawn into the device  10 . In another embodiment, shown in  FIG. 8B , the fluids are contained in the separate vials or cartridges  44  each in communication with a three-way portal  45 . When the plunger of mixing and delivery device  10  is activated desired quantities of each fluid are simultaneously drawn from vials  44 , through portal  45 , injector  42  and into the mixing chamber of device  10 . It should be appreciated that the fluids can be drawn into the tube by creating pressure on the opposite side of the mixer. 
     Referring to  FIGS. 9 and 10 , a preferred embodiment of a device  50  for mixing and delivering the viscous fluids for the arthroscopic repair of tissue is shown. A primary arthroscopic sheath  52  is used for the delivery of fluids, suction or a camera as is known. A first portal  46  communicates with sheath  52  to deliver fluids or supply air or suction. A secondary sheath  54  is disposed below primary sheath  52  and extends parallel to the axially length thereof. Secondary sheath  54  is used to deliver the collagen and platelet gel as described above. Secondary sheath  54  can be permanently or removably attached to the primary sheath. Although secondary sheath  54  is shown as being disposed below the primary sheath other positions are contemplated by the present invention. 
     Secondary sheath  54  has opposed ends, one end has a tip  56 , which will be described further herein, and the other end  58  communicates with a second portal  48 . The mixing and delivery device  10  loaded with the mixture is removably attachable to portal  48  to deliver the mixture to secondary sheath  54 . Portal  48  includes an interlocking connection  49  to lock the mixing and delivery device  10  therein. As shown in  FIG. 10 , the diameter of the secondary sheath is smaller than the diameter of the primary sheath. 
     Referring to  FIGS. 11A-11E , different embodiments of tip  56  are illustrated. As shown in  FIG. 11A , tip  56  can be straight. Alternatively, as shown in  FIG. 11B , tip  56  can be bent at an angle with respect to the primary sheath tip. The tip can be angled downward in a range of 0-90°, and more particularly, between 30 to 70°. The tip can be bent at 30° to match a standard lens angle or 70° to match a 70° lens of a camera sheath. The tip can also be fan-shaped as shown in  FIG. 11C . Tip  56  can also be made of a flexible material so that it can be pushed and inserted into nooks or crannies of the joint as shown in  FIG. 11D . In order for the surgeon to be able to change the direction of the tip to control the handpiece, tip  56  can be steerable as shown in  FIG. 11E . When the sheaths are located at the injury site, the physician can direct the collagen mixture to the tear or rupture to deliver the same. Depending on the type of delivery desired the tip of the secondary sheath can have one of the above shapes. 
     As shown in  FIG. 12 , the syringe filled with the mixture can be placed in a heating bed  60  to heat the fluid. Drive shaft  30  of the plunger can be connected to a motor  64  which rotates the plunger and auger within the syringe. The heating element and motor can be located on a sterile table remote from the procedure site, but convenient to the operating physician. Mixing and heating the mixture gets the mixture to the desired viscosity, uniformity and temperature. 
     The viscosity of the injected fluid determines whether or not the mixture functions as an effective scaffold. If the viscosity is too low, the fluid will drip out of the target injury site, and will be of no use. If the viscosity is too high, the molecular structure of the fluid is ripped apart when injected through the injector or needle. The viscosity is determined by the initial collagen makeup and the degree of cross linking. The collagen makeup is done in the lab, and results in a solution roughly as viscous as corn syrup. The cross linking dictates the viscosity in that as the cross links are formed during the curing process, the molecules become more intertwined, and more resistant to flow. If too far advanced, these bonds are destroyed when injecting. A degree of cross linking must be attained in order to meet the minimum viscosity specification. Since, the rate of cross linking is temperature dependent, a time-heat method is used to control the viscosity. 
     The present invention contemplates different ways to heat the fluid, for example, an internal viscous heater, an external heater, or a thermal mass. The viscous heater operates by shear friction between the mixing element and the fluid. The external element is heated and surrounds all or a portion of the fluid container. The thermal mass is charged to an appropriate temperature, and then inserted to transfer heat. A viscous shear heater does not require additional components. The fluid is heated by running the mixer for a longer period of time. However, damaging the collagen-PRP matrix as it begins to crosslink may occur. Once the two chemical begin to crosslink, the rotation of the mixer could act to rip apart the bonds, so mixing should be carefully controlled. 
     A resistance heater generates heat when current passes though, i.e., by joule heating. Resistance heaters have well defined performance characteristics and can be controlled relatively easily. The electrical energy required is also well within the available energy stored in a 9V battery. 
     The thermal mass method can be implemented with an external mass, such as a block of aluminum, or with a fluid, such as the plasma. Here the energy is stored in the thermal mass, instead of the electric charge. This offers the advantage of being rechargeable via a hot water bath, as well as, eliminating potentially complicated control aspects. It simplifies sterility aspects in the preparation stage as it is only a block of metal to autoclave. However it requires a sterile hot-water bath. 
     A resistive heating element has the ability to control heat output, as well as the existing presence of electrical storage for the motor. Heating element  60  can be a 5 W heater capable of heating the fluid to the necessary injection temperature in a short period of time, for example, 2-5 minutes. The system can be run open-loop, using either external measurement, or a specified time, based on initial temperature and experimental results. A production model could include closed loop electronics to control the temperature automatically. With closed loop control, a more aggressive heating pattern could be followed as well, potentially reducing the heating time as low as approximately 1 minute. A low-complexity design could be a hand-cranked mixer with a thermal mass heater. Although the heating element  60  is described as a resistive heating element, it should be appreciated that the device of the present invention contemplates a variety of heating designs in addition to those described above. Moreover, viscosity can be measured indirectly by drag on the motor. A viscosity sensor  65  ( FIG. 12 ) could likewise be located within the motor, mixing tube, injection portal or other location. 
     After the desired temperature and viscosity has been reached the mixing and delivering device  10  is removed from the heating bed and located into portal  48  to deliver the heated and mixed fluid to the injury site via secondary sheath  54 . 
     Alternatively, the mixing and heating device  10  can be inserted in a chilling element  62  in the same manner as above. The chilling element can keep the collagen and/or mixture cold until it is ready for use to avoid premature setting. 
     Chilling element  62  may have a refrigeration element designed to maintain the collagen component at a desired temperature, for example, 4° C. Conforming chill packs, a refrigeration element, gas, cold water circulation or other mechanical equivalents, are examples of cooling sources that can be incorporated in element  62 . The cooling source surrounds a sterile core into which the collagen syringe can be kept until ready to mix with the platelets. 
     In order for the glue scaffold to adhere to the injured tissue it is necessary to remove fluid from the target site. Some strategies to meet this drying requirement are to wipe/sponge, remove moisture via suction, or blow dry the ligament. Wiping would use capillary action in a material to remove moisture from the operation site. A pressurized gas can provide a blow drying technique to force fluid particles off of the operation site with a stream of air. It also facilitates evaporation through the introduction of a gas with a low moisture partial pressure. However, the operating arena may not have a source for pressurized gas. In that case and to make the device portable, the use of a compressed gas cartridge may be necessary. Typical gas cartridges are filled at 300 psi. therefore, it may be necessary to incorporate a flow regulator in order to control flow rate and prevent damage to the patient tissue. Alternatively the site can be dried by using a suction source. In the embodiment of  FIG. 9 , a pressurized gas delivered through primary sheath  52  or a suction source applied to primary sheath  52  can be used to dry the target site prior to delivering the scaffold. 
     Referring to  FIGS. 13-15  another embodiment of the present invention is shown. A hand-held device  70  for mixing and delivering the viscous fluids includes a barrel  72  having ends  74  and  76 . The mixing and delivery device  10  is removably located at end  74  of the barrel. A handle  78  is formed at the other end of the barrel. A trigger mechanism  80  is pivotally connected to the barrel  72 . Trigger  80  communicates with a shoulder  31  ( FIG. 5 ) of shaft  30  such that when the user activates trigger  80  it pushes plunger  16  into tube  12  to compress auger  14  and dispense the fluid through injector  42 . 
     A heater  82  is mounted on barrel  72  and communicates with mixing and delivering device  10 . As previously described herein, heater  82  heats the fluids to control the viscosity of the same. A battery  84  located on or within barrel  72  can provide the power source for heater  82 . 
     A mechanism  86  for drying the injury site is also removably located on the barrel. Dryer  86  can be a nozzle that snaps on barrel end  74 . Nozzle  86  includes a sheath  88  that receives the needle or injector  42  when the nozzle is fitted on the device. A CO 2  cartridge and flow regulator can be located within handle  78  and can connect with sheath  88  via tubing. Alternatively, handle  78  can include a port for connecting a source of gas or suction to dry the injury site. 
     As discussed above, it may be necessary to incorporate a flow regulator in order to control flow rate and prevent damage to the patient tissue. A CO 2  nozzle was designed to both protect the fluid carrying needle and to deliver the CO 2  to the target site. The nozzle uses thin-wall steel tubing as an outer case. The nozzle connects to the body of the gun using an out-of line quick-connect fitting that also serves to stabilize the nozzle. The CO 2  enters the nozzle from the bottom, and proceeds to the tip, where a dome-shaped fitting centers the needle while allowing CO 2  to pass. The needle pierces a septum on the back of the nozzle, which prevents the CO 2  from flowing out the wrong end. 
     A motor  90  to mix the fluids is located on the barrel as previously described. Motor  90  can be driven by battery  84  or connectable to a remote AC power source via wiring  92 . 
     Referring to  FIGS. 16A and 16B , an alternative way to deliver the collagen and PRP is shown. A plurality of preloaded cartridges  94  each having a desired quantity of collagen and PRP can be provided. A one-way valve  96  communicates with a respective cartridge and the mixing and delivery device  10 . When the valves are open the plunger can be used to act as a displacement pump to draw the fluids simultaneously or in parallel into the mixing device. Another valve disposed downstream of the cartridges can remain closed until it is time to dispense the mixture. 
     In order for the device to be used in an operating room environment, it must be sterile. Therefore, the device of the present invention, i.e., the gun, mixing and delivery device can be made of disposable and/or autoclavable parts. The gun shell and the needle would have to be sterilized, as they would be in direct contact with bodily fluids. Also, the battery, and CO 2  canister would have to be replaced once the stored element was exhausted. The more expensive parts, such as the needle, tip, motors, etc, can be sterilized. The cheaper plastic, injection molded parts such as the auger/injector system, could be disposable. In addition, the layout of the operating room makes any secondary, external operation more difficult. The various parts can be sterilized and packaged in a kit that can be sealed and brought to the operating arena. 
     In use, one process of mixing the collagen and platelet rich plasma (PRP) and injecting it once it has reached the appropriate viscosity is as follows. First, dip the needle into the collagen and extract an appropriate amount thereof, for example, approximately 1.5 ccs. Then, dip the needle into the PRP and extract a desired amount, for example, 1.5 ccs of plasma. Point the gun upwards and purge the syringe of any air. Then snap on a CO 2  nozzle, mix the scaffold, for example, for 10 seconds, and heat the scaffold (i.e., for 4 minutes. The system is then purged of any unmixed fluid that has remained in the needle. The ligament is dried via, for example, the CO 2  flow, and the mixtures of collagen and PRP is injected at the target site. 
     The present invention also contemplates a visual feedback means that will enable the doctor to verify that the mixture must be injected within a certain time frame either through for example, lights or a display. Additionally, the device could have means to control the viscosity using feedback from measuring the power draw on the motor. A pressure regulator can be included in addition to the flow regulator within the CO 2  delivery system to better control the pressure of the fluid released over time. Additionally, a precise specification of the flow rate and pattern required should be determined by the doctor to ensure that the canisters will provide enough fluid for the entire procedure time. 
     The integration of all the components into a cohesive form allowed for convenient use by the operating doctor. The main considerations are intuitive control location, ergonomics, and routing of the high-pressure CO 2 . In order to allow for comfortable, but precise manipulation by the doctor, a pistol-grip form was selected. The intuitive control allows doctors to use the gun as any other device. The controls are located in an ambidextrous fashion, with the exception of the heater switch. The heater switch is located on the side. The CO 2  lines are routed so as to be as short and straight as possible. This is to minimize the possibility of leakage or damage to the tubing, which can lead to the catastrophic failure of the CO 2  system. 
     The integration methods described earlier, the single embedded syringe-mixer and the dual-cartridge displacement-pump/mixer, should be considered in terms of the overall process and considerations to sterility. With regard to dimensions associated with device, the most critical dimensions are associated with the sealing in the syringe and in the drive train/gear system. The inner dimension for the rotary seal on the plunger should ideally be made to within 0.001 in. so that the friction associated with the seal remains as uniform as possible. Critical dimensions associated with the drive train are the gear spacing and the allowable shaft misalignment. The spacing between the pinion and spur gear (not shown) should be held to within 0.005 in. to insure the proper spacing. Binding will occur if the shaft has worse than 0.008 radians axial misalignment with the bearing. Since the end of the shaft is constrained by the syringe, it must be put on the gun with no more than 0.04 in. offset from the shaft. 
     The majority of the components of the device can be manufactured using rapid prototyping techniques, for example, injection molded. The left and right shell, the CO 2  canister cover, the left and right syringe pusher blocks, the trigger, and the front of the device can be made using stereo lithography. The collapsible auger can be made, for example, using selective laser sintering because it is subjected to higher stresses. The mixing and delivery device can be made of Radel®, Peek®, or Tecapro®, or another high performance medical grade plastic. The bearing and the seal piston can be machined from Delrin. 
     The present invention provides a unique injection system for the enhanced ACL repair. Although the device and system of the present invention has been described for repairing an injured ACL, it should be appreciated that it can be used for numerous different procedures, for example, fibrin sealants in cardiac surgery. The system of the present invention integrates a sample extractor, mixer, dryer, heater, and injector into one unit. Shown by experimental data, the injection system is capable of performing the enhanced repair processes while remaining totally sterile. By coupling features like a viscosity sensor and a thermometer, the system can be used to monitor the process and give surgeons feedback if required. Also, the system is specialized for mixing of highly viscous solutions, which makes it a powerful tool for various processes like bone cement or epoxy mixing. 
     Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.