Patent Publication Number: US-8986185-B2

Title: Syringe centrifuge systems

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Prov. App. No. 61/245,451 filed on Sep. 24, 2009, U.S. Prov. App. No. 61/294,994 filed on Jan. 14, 2010, and U.S. Prov. App. No. 61,322,277 filed on Apr. 8, 2010. The entire content of each of the foregoing applications is incorporated herein by reference. 
    
    
     BACKGROUND 
     There remains a need for improved devices and methods for isolating autologous fat in injectible form. 
     SUMMARY 
     A hand-cranked centrifuge is adapted for use in isolating autologous fat in injectible from. A number of syringes are hingeably coupled to a flywheel of the centrifuge. As the centrifuge turns, the syringe(s), which are supported at one end, move into a horizontal orientation and are centrifuged until the fats get separated from other liquids present in the syringes. A number of syringes, syringe holders and related devices are disclosed to accommodate centrifugation. 
     In one aspect, a centrifuge disclosed herein includes a base plate; a gearbox coupled to the base plate that transfers rotation of a crankshaft to a driveshaft, wherein the crankshaft is a sterilizable crankshaft removably and replaceably coupled to the gearbox and wherein the driveshaft is a sterilizable driveshaft removably and replaceably coupled to the gearbox; a flywheel coupled to the driveshaft through a clutch, the flywheel having a perimeter and a plurality of attachment points distributed near the perimeter, each attachment point adapted to hingeably support a syringe in a manner that permits a rotation of the syringe radially outward from the flywheel during centrifugation; and an attachment mechanism that secures the base plate to a working surface. 
     The base plate may be formed of stainless steel. The gearbox may provide a gearing ratio from the crankshaft to the drive shaft of about 1:5. The centrifuge may include a display that may provide visual feedback to a user concerning operation of the centrifuge. The display may provide a numerical indication of rpm of the centrifuge. The display may be an electronic display. The electronic display may be powered by conversion of energy from the crankshaft. The display operates mechanically to provide centrifuge status information to the user. The clutch may be a free-wheeling clutch that permits continued rotation of the flywheel when the driveshaft rotates more slowly than the flywheel. The clutch may include a power take-off that prevents the centrifuge from exceeding a predetermined rotational velocity. 
     The driveshaft may be keyed to the gearbox and secured to the gearbox with at least one of a clevis fastener and a cotter ring. The crankshaft may be keyed to the gearbox and secured to the gearbox with at least one of a clevis fastener and a cotter ring. Each attachment point of the flywheel may include a hole. The centrifuge may include a hook in each attachment point shaped to retain an end of a plunger for a syringe. The hook in each attachment point may include a lock to secure the plunger during centrifugation. The plurality of attachment points may include eight attachment points. The attachment mechanism may include a clamp. The attachment mechanism may include at least one suction cup. The flywheel may have a diameter of about 12 cm. The crankshaft may be powered by a foot pedal. 
     In another aspect, an apparatus disclosed herein includes an end support shaped and sized to retain a barrel of a syringe; an arm extending from the end support to a flywheel attachment shaped to secure the arm to a hole in a flywheel; and a plunger support on the arm that removably and replaceably couples to a plunger extending from the barrel of the syringe. 
     The plunger support may include a hook-and-loop fastener. The plunger support may include a plurality of fingers that springably engage the plunger. The plunger support may include a band with a snap to circumferentially secure the plunger. The plunger support may include a through-hole in the arm. The plunger support may include a protrusion. The end support may include a forked opening. The end support may include a hole that encircles the barrel. The end support may be shaped and sized to securely hold a 60 cc syringe barrel. The plunger support may be positioned to securely retain a plunger at an end of the plunger when the plunger may be fully retracted from the barrel. 
     In another aspect, a syringe disclosed herein includes a barrel having a lumen, an opening on a first end and a fluid port on an opposing end for passage of fluid into and out of the lumen; a plunger shaped to fit through the opening on the first end of the syringe, the plunger having a seal that slidably engages an interior wall of the barrel; and a lock to retain the plunger in a fixed position relative to the barrel. 
     The barrel may be formed of a clear plastic. The barrel may be gradated with markings that indicate volume within the lumen. The lumen may have a volume of at least 60 cubic centimeters. The opening on the first end of the barrel may include an interior rib that resists a passage of the seal out of the barrel. The fluid port may include a needle attachment. The needle attachment may be threaded. The lock may include a pin that passes through a wall of the barrel and fits into a mating hole in the plunger. The lock may include a fork that surrounds and restrains the seal of the plunger. The plunger may include a thumb rest with one or more holes for securing the syringe to a centrifuge. 
     In another aspect, a syringe cap disclosed herein includes an open end shaped and sized to fit about a plastic tip of a syringe; a closed end opposing the open end that retains material within the syringe when the syringe cap may be secured to the plastic tip; and a thread disposed within an interior of the syringe cap thereby providing a threaded region within the cap, the thread having a crest providing a sharp edge and sufficient hardness to cut into the plastic tip. 
     The syringe cap may include finger grips disposed on an outside of the syringe cap. The finger grips may include two opposing tabs. The interior may be tapered along the threaded region so that a first diameter toward the open end may be greater than a second diameter toward the closed end. The syringe cap may be formed of stainless steel. 
     In another aspect, an apparatus disclosed herein includes a barrier formed of a sheet of material, the barrier being a sterilizable barrier shaped and sized to fit about a gearbox of a hand-cranked centrifuge; a first opening in the barrier, the first opening positioned to receive a crankshaft for the gearbox and the first opening having a seal for the crankshaft; and a second opening in the barrier, the second opening positioned to receive a driveshaft for the gearbox and the second opening having a seal for the driveshaft. 
     The first opening may include a bearing to permit sealed rotation of the crankshaft. The second opening may include a bearing to permit sealed rotation of the driveshaft. The barrier may be formed of a disposable material provided for use in a sterile package. The barrier may extend a sufficient distance along a working surface for the gearbox to form a sterile barrier between the gearbox and a surrounding environment. 
    
    
     
       DRAWINGS 
       The foregoing and other objects, features and advantages of the invention will become apparent from the following description in conjunction with the accompanying drawings. The drawings are not necessarily to scale. Emphasis has instead been placed upon illustrating the principles of the invention. Of the drawings: 
         FIG. 1  shows a syringe centrifuge. 
         FIG. 2  shows a top view of a flywheel for a syringe centrifuge. 
         FIG. 3  is a perspective view of a syringe centrifuge. 
         FIG. 4  shows a method for using a syringe centrifuge. 
         FIG. 5  shows a syringe for use with a syringe centrifuge. 
         FIG. 6  shows a syringe holder. 
         FIG. 7  shows a syringe holder. 
         FIG. 8  illustrates the movement of a number of syringes on a syringe centrifuge during centrifugation. 
         FIG. 9  shows a cross section of a cap for a syringe. 
         FIG. 10  shows a sterilization barrier for a centrifuge 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Described herein are a number of syringe centrifuges and methods for using same. The methods and systems may be suitably employed in a variety of surgical augmentation procedures such as cosmetic augmentation, filling, contouring, and so forth. Still more generally, these methods and systems may be usefully employed in any procedure where fat or other substances might be usefully separated from other liquids, tissue and the like for injection or other deployment from a syringe. 
     In one aspect, a hand-turned centrifuge is attached directly to a plunger of a syringe through an attachment point that permits the syringe to orient radially from a flywheel during centrifugation. A lock or similar mechanism may be provided to firmly secure the plunger to the barrel of the syringe in order to prevent accidental separation and resulting loss of extracted biomaterials contained in the barrel of the syringe. 
       FIG. 1  shows a syringe centrifuge. In general, the centrifuge  100  may include a base plate  102 , a gearbox  104 , a driveshaft  106 , a clutch  107 , a flywheel  108 , and a crankshaft  112 , all as described in greater detail below. One or more syringes  110  may be attached to the flywheel  108  during use as depicted in  FIG. 1 . 
     The base plate  102  may be formed of stainless steel. The base plate may, for example be an 18 cm by 10 cm rectangle that is 1 cm thick. The base plate  102  may be secured to a working surface  120  such as a table by an attachment mechanism  122 , which may include a clamp or the like to secure the centrifuge  100  during use, taking into account the rotary motion of the centrifuge  100  and any syringes  110  (and contents thereof) attached to the centrifuge  100 . The attachment mechanism  122  may be adjustable to accommodate working surfaces of different shapes and thickness, and may include a quick-release or the like for easy removal of the centrifuge  100 , and/or a lock or other mechanism to avoid accidental release. The attachment mechanism  122  may also or instead include suction cups  308 , hook-and-loop fasteners, adhesives, nuts, bolts, screws and any other components for temporary, semi-permanent, or permanent mounting of the centrifuge  100  on the working surface  120 . 
     The gearbox  104  may be attached to the base plate  102  using any suitable techniques. In general, the gearbox  104  may be any combination of gears and other mechanical couplings to transfer rotation of the crankshaft  112  to the driveshaft  106 . This may, for example, include a right-angle gearbox with a 1:5 gearing ratio (from crankshaft  112  to driveshaft  106 ) such as the Groschopp Model RA3000 commercially available from Groschopp Integrated Motion Solutions. More generally, any gearing ratio and crank-to-drive angle consistent with operation of a manually-powered centrifuge as described herein may be suitably employed as the gearbox  104 . 
     It will be appreciated that, while a hand crank provides a convenient, low-cost source of power to rotate a centrifuge, other techniques may also be employed. This may include direct sources of manual power input, such as a foot pump or pedal  138 , lever, or the like through which a user can provide energy that is converted into rotation by the centrifuge  100 . This may also or instead include mechanical energy storage systems such as a wind-up spring, compressed air, or the like to store manually-provided energy for use during a centrifuging operation. In another aspect, the centrifuge may be electrically powered using any of a variety of techniques. This may include a switch or the like to turn the centrifuge on, along with one or more switches, dials, or the like to control a speed of the centrifuge. Thus in one aspect the gearbox  104  and crankshaft  112  may be replaced with an electrically powered motor. This approach advantageously provides hands-free operation of the centrifuge  100  and may with suitable instrumentation permit more consistent, controllable drive speeds. On the other hand, manual operation advantageously removes any requirement for external power, and the expense of packaging electronics and related components for sterilization. 
     In one aspect, the gearbox  104  may establish a maximum rotational speed for the device  100 , such as a target number of revolutions per minute (“rpm”) or the like. In another aspect, the gearbox  104  may permit a variable top speed, which may include two or more user-selectable speeds, or a continuously variable top speed. A wide variety of gears and gear systems are known in the art, including spur gears, helical gears, double helical gears, bevel gears, hypoid gears, crown gears, worm gears, non-circular gears, rack and pinion systems, epicyclic gears, sun and planet gears, harmonic drives, and cage gears, any of which may be employed in various combinations to provide the desired gearing ratios within the gearbox and/or to provide a desired output speed or power. 
     In one aspect, a continuously variable transmission or the like may be employed to permit rotation of the flywheel  108  at a constant angular velocity regardless of input at the hand crank. Suitable transmissions may employee chains, pulleys, belts and so forth, such as a variable-diameter pulley drive, a toroidal or roller-based transmission, an infinitely variable transmission, a ratcheting transmission, a hydrostatic transmission, a variable toothed wheel transmission, a cone transmission, a radial roller transmission, or a traction-drive transmission. An override clutch or other mechanism may be similarly employed to limit angular velocity of the flywheel  108  independently from a speed at which the hand crank  112  is rotated. 
     Other gears, clutches, bearings and the like may also be employed to change the direction, speed, orientation or the like of rotational energy provided from the hand crank  112 , as will be readily appreciated by one of ordinary skill in the art, and all such variations are intended to fall within the scope of this disclosure. Similarly, a brake or the like may be provided to stop or slow rotation of the centrifuge during or after use. 
     The driveshaft  106  generally serves to drive the centrifuge  100 . The driveshaft  106  may be coupled to the crankshaft  112  through the gearbox  104 . The driveshaft  106  may, for example, include a 40 cm length of 15 mm stainless steel or other material. The driveshaft  106  may have a bottom end that reduces to about 11 mm or any other suitable diameter to fit into the gearbox  104 , where the driveshaft  106  may be keyed to rotationally engage a corresponding opening in the gearbox  104 . The driveshaft  106  may be secured to the gearbox  104  with a drive shaft fastener  134  such as a clevis fastener, cotter pin, circle cotter, split pin, or any other suitable fastener. The driveshaft  106  may also or instead use a friction fit to engage the gearbox  104 . The driveshaft  106  may be removably coupled to the gearbox  104  to permit cleaning, storage, and the like. A lip may also be provided to stop the driveshaft  106  at a predetermined depth into the gearbox  104  during insertion. A bearing or the like may also be provided to relieve friction between the lip and the top of the gearbox  104 . The crankshaft  112  may be keyed to the gearbox and secured to the gearbox with a crankshaft fastener  136  such as at least one of a clevis fastener and a cotter ring. 
     The clutch  107  may be attached to a top end of the driveshaft  106 . The clutch  107  may be keyed to the driveshaft  106  and secured using cotter rings or the like. Washers, pressure clips, and the like may be used to more securely fasten the clutch  107  to the driveshaft  106 , or the clutch  107  may be permanently attached to the driveshaft  106  using a welded joint or the like. In this latter arrangement, the clutch  107  may be preferably sealed in a manner that permits sterilization of the clutch/driveshaft arrangement. The clutch  107  may serve a variety of functions in the centrifuge  100 . For example, the clutch may provide free-wheeling rotation of the flywheel  108  in one direction so that the driveshaft  106  applies rotational force to the flywheel  108  when turning faster than the flywheel  108 , and the flywheel  108  can spin freely when the driveshaft  106  is turning more slowly. Thus the crankshaft  112  can decouple from the flywheel  108  after a desired rate of rotation is achieved. One suitable clutch is the Sprag Clutch, Model FN400 (15mm), commercially available from the GMN Bearing Company. The clutch  107  may also or instead include a power take-off  132  that decouples the driveshaft  106  from the flywheel  108  after a certainly rotational speed has been achieved. This advantageously produces a consistent top speed for the centrifuge  100  to relieve an operator from determining or estimating an appropriate rotational velocity for centrifugation. The power take-off  132  may be used in the clutch  107  addition to or instead of the free-wheeling mechanism described above, or various functions of the clutch  107  may be instead realized within the gearbox  104  as generally discussed above. 
     The crankshaft  112  may be formed of stainless steel or other suitable material and extend horizontally or in any other useful orientation from the gearbox  104 . The crankshaft  112  may, for example, be fashioned from a 25 cm length of 15 mm diameter stainless steel. The crankshaft  112  may be reduced to, e.g., 14 mm and keyed on one end (an “insertion end”) for insertion into and engagement with the gearbox  104  in any manner similar to the driveshaft  106  as discussed above. The crankshaft  112  may be removable to permit cleaning, sterilization, storage, transportation, and so forth. An opposing end or “handle” end may have a handle  113  permanently attached (e.g., with a welded joint, epoxy, or the like), or removably attached to permit further disassembly. The handle may include a bearing or the like to permit for convenient orientation and gripping while the crankshaft  112  is turned. 
     The centrifuge  100  may include a display  130  that provides visual feedback to a user concerning operation of the centrifuge  100 . This may, for example, include an indication of the current rpm of the centrifuge  100  and/or whether the centrifuge  100  is rotating at an appropriate speed for centrifugation. In one aspect, the display  130  may be an LCD, LED or other electronic display that provides a numerical indication of rpm, or other useful information, such as whether the speed is correct (which may be a simple LED indicator or the like), a dynamic bar or the like that moves according to a current speed, or an indication of whether to increase or decrease cranking speed. In one aspect, the electronic display may be powered by conversion of energy from the crankshaft  112  for the centrifuge  100 . In another aspect, the display  130  may operate mechanically or electro-mechanically using any suitable techniques to provide centrifuge status information to a user. 
     The flywheel  108  is coupled to the clutch  107  and/or driveshaft  106  to transfer rotational power from the driveshaft  106  to the flywheel  108 . The flywheel is described in greater detail below. 
       FIG. 2  shows a top view of a flywheel  200  for a syringe centrifuge. The flywheel  200  may include a clutch  202  as generally described above that secures the flywheel to a driveshaft, which may be any of the driveshafts described above. A number of attachment points  204  may be distributed near the perimeter of the flywheel  200  for coupling to syringes (not shown). The flywheel  200  may have any dimensions suitable for centrifuging syringes as generally contemplated herein. The flywheel  200  may, for example, be formed of stainless steel with a thickness of about 1 cm and a diameter of about 12 cm, or any other suitable dimensions. For eight attachment points  204 , the attachment points  204  may be evenly spaced at about 0, 45, 90, 135, 180, 270, and 315 degrees about a center of the flywheel  200 . In one embodiment, the flywheel  200  may be shaped and sized to hold up to eight 60 cc syringes and spin at about 300-400 revolutions per minute under power of the driveshaft. 
     More generally, the flywheel  200  may be fabricated from a variety of materials, and may provide a variety of mechanisms for hingeably connecting one or more syringes thereto. In one aspect, the flywheel  200  may have sufficient mass to maintain balanced rotation substantially independent of the mass of one or more syringes attached thereto. Where the mass of the flywheel  200  is lower, syringes may be preferably attached at radially opposed locations in order to balance rotation of the flywheel  200 . In addition, one or more removable and replaceable weights may be provided on the flywheel  200  to balance rotation after one or more syringes have been attached. Similarly, one or more movable/slidable weights may be mounted to the flywheel  200  to permit adjustable balancing as syringes are added to and removed from the flywheel  200 . These weights may, for example, slide from a center of the flywheel  200  toward a perimeter of the flywheel  200  to counterbalance syringes as appropriate. These movable weights may slide between two or more fixed positions (that may be located with tactile feedback, alignment guides, or the like) or may be continuously adjustable to permit user-customizable adjustments according to syringe size, observed balance, and so forth. 
     In one aspect, the flywheel  200  includes holes or the like to accommodate hooks or other attachment points for syringes. The attachment point(s) may permit rotation of the attached syringe radially outward from the flywheel using, e.g., a suitably oriented hook/loop in a hole, a hinge, a universal coupling (e.g., a ball in a socket) or any other suitable mechanical coupling or combination of couplings. By permitting syringes to swing freely and radially from the flywheel  200 , each syringe is able to rotate during centrifugation into alignment, or substantially close to alignment, with the outward force of centrifugation. As rotational velocity decreases, the syringes can then return to an orientation that preserves a separation of centrifuged substances by operation of gravity. 
       FIG. 3  is a perspective drawing of a syringe centrifuge. The centrifuge  300  may, for example be any of the centrifuges described above. As depicted in  FIG. 3 , the flywheel  302  of the centrifuge  300  may have a number of hooks  304  or similar attachment points for syringes. Each hook  304  may have a syringe retainer  306  such as a number of fingers or a circular hole to receive and hold a flanged end of a syringe plunger. Each hook  304  may include a locking mechanism that securely engages and retains the plunger until actively released. A variety of spring-actuating and other locking mechanisms suitable are known in the art that may be suitably adapted to securely retaining a syringe plunger as contemplated herein. The hooks  304  may be coupled to the flywheel  302  in a manner that permits rotation away from an axis of the driveshaft during centrifugation as described above. The shape and size of each syringe retainer  306  is not important except that the syringe retainer  306  should be capable of retaining a syringe under the forces of centrifugation expected during use. In one aspect, there is disclosed herein a syringe centrifuge that secures syringes by a plunger end (e.g., from the hooks  304 ) in a manner that permits rotation to a horizontal orientation during centrifugation. 
       FIG. 4  shows a method for using a syringe centrifuge. The method  400  may begin with extracting fat and other liquid/tissue from a donor site as shown in step  402 . The fat may, for example, be autologous fat from a patient who is receiving an augmentation procedure. The fat may be extracted using any suitable surgical syringe or like device. This may for example include a relatively small syringe (e.g., 5 cc volume) or a relatively large syringe (e.g., 60 cc volume), or any size in between (or larger or smaller) depending upon the nature of the donor site, the nature and volume of the augmentation, and any other considerations. 
     As shown in step  404 , the method  400  may include attaching one or more syringes to a centrifuge such as the centrifuge described above. This may include, for example, using a hook or the like on the syringe, or a clip, clamp, or other attachment on the centrifuge flywheel. While a flywheel with holes to secure to syringes is depicted, it will be readily appreciated that a variety of useful attachment techniques may be employed. In general, any form of attachment that either (a) permits a syringe to rotate into a substantially horizontal and radially extending orientation by centrifugation, such as a freely rotating or pivoting attachment or the like, or (b) secures a syringe in a substantially horizontal and radially extending orientation, may be suitable employed to attach syringes as described herein. In one aspect, balanced centrifugation may be achieved by using one or more pairs of substantially equally filled and equally sized syringes on opposing sides of the flywheel, or by providing an equivalent counterweight for a single syringe. 
     The method may include rotating the centrifuge, as shown in step  406 . This may, for example, include turning a crank on the hand-cranked device described above, or providing mechanical force through any other suitable manual, mechanical, and/or electronic means. For example, the centrifuge may include an electrical motor and timer to provide timed centrifugation with a single press of a button. The centrifuge may be rotated for a fixed time (e.g., two minutes), or a time that varies according to syringe volume, tissue types, or any other factor(s). The centrifuge may include an electro-mechanical system to perform any number of potentially useful related functions such as providing mechanical advantage for higher speed rotation, providing for relatively continuous increases and decreases in speed, preventing rotation beyond a predetermined speed, or otherwise improving centrifugation to achieve desired separation. In general, centrifugation continues until a desired separation of fat from other liquids/materials is achieved. 
     The method may include removing a syringe from the centrifuge as shown in step  408 . After centrifugation with, e.g., the needle end of the syringe away from the flywheel and the plunger end near the flywheel, fat that is less dense than water or other liquids may move by centrifugation toward the plunger end of the syringe. Once a syringe is removed from the centrifuge, the plunger may be pushed to evacuate non-fat materials from the needle end of the syringe, leaving a syringe with injectible fat for any surgical or other use. In other embodiments, the syringe orientation may be reversed so that fat is urged by centrifugation toward the needle end of the syringe. This may pose additional challenges for a surgeon, such as using the separated fat before it begins to mix with other materials and monitoring an injection to ensure that only fat is injected into a surgical site. Nonetheless, this technique may be employed without departing from the scope of this disclosure. 
     The method may include injecting the fat into a site such as a surgical site as shown in step  410 . This may, for example, include a breast enlargement site or any other site suitable for augmentation with fat. 
     It will be appreciated that the steps described above may be re-ordered, modified, omitted, or supplemented all without departing from the scope of this disclosure. For example, a needle end of a syringe may be sterilized before injection of separated fat, or the needle used to extract fat may be replaced altogether with a different needle for injection. It will also be appreciated that while separation of fat for surgical augmentation is emphasized in this description, the principles of this disclosure may be suitable adapted to any environment where materials might be extracted, separated based upon density, and re-injected with a syringe. All such variations are intended to fall within this description. 
       FIG. 5  shows a syringe for use with the centrifuge described herein. In general, the syringe  500  may include a barrel  502  having a lumen  504 , an opening  506 , a needle attachment  508 , and a lock  510 , along with a plunger  512  having a seal  514 , a stem  516 , and a thumb rest  518 . 
     In general, the syringe  500  may serve to extract material into the lumen  504  by operation of the plunger  512  out of the lumen  504  (to the left as depicted), attach to a centrifuge as described in greater detail below, and then evacuate the lumen  504  by depression of the plunger  512  back into the barrel  502 . The syringe  500  may have a generally cylindrical shape (i.e., with a circular axial cross section) as typical of syringes known in the art, however this shape is not required. The syringe  500 , including the barrel  502  and/or plunger  512  as well as various parts thereof may have a different cross-sectional shape such as oval, rectangular, or any other polygonal or other shape. 
     The barrel  502  may be formed of any material, such as a biocompatible, clear plastic to permit viewing of biomaterial inside the lumen  504 . The barrel  502  may be gradated with printed or raised marking and text indicating volume within the barrel  502 . When deployed as a kit or otherwise sold or distributed for use, the barrel  502  may be sterilized and packaged in a sterile container or the like. The barrel  502  may be delivered with the plunger  512  already inserted therein, or plungers and barrels may be delivered separately for use/re-use according to judgment or preference of a medical professional using the device. 
     The lumen  504  may be of any suitable volume for a particular application. Volumes from 5 cubic centimeters to 60 cubic centimeters and beyond may be usefully employed in cosmetic surgical procedures as contemplated herein. As noted above, material within the lumen  504  may be viewed through a transparent wall of the barrel  502 . The opening  506 , generally permits insertion/removal of the plunger  512  into the lumen  506 . The opening  506  may include an interior rib, flange, or the like that resists passage of the seal  514  into and out of the barrel  502  so that, e.g., the plunger  512  tends to remain within the barrel  502  during use. 
     The barrel  502  may include a fluid port  530  on an opposing end of the barrel from the opening  506 . The fluid port  530  may be for passage of fluid (such as fat) into and out of the lumen, and may generally permit fluid engagement of the lumen  504  to a surgical site, such as where fat is to be removed or injected. The fluid port  530  may include a needle attachment  508  that is threaded or otherwise fitted for attaching, removing, and/or replacing a needle on the end of the barrel  502 . The choice of a needle gauge, length, and so forth may depend upon a particular surgical procedure in which the syringe  500  is to be used. 
     The lock  510  may be any suitable locking mechanism for retaining the plunger  512  in a fixed position relative to the barrel  502 . This may include a dowel, pin, or the like that inserts into a mating hole in the plunger  512 . The dowel may removably pass through a wall of the barrel  502 , or may be mounted in the wall in a manner that seals the contents of the lumen  504  within the barrel  502  while permitting inward and outward motion of the pin, such as to secure and release the plunger  512 . In other embodiments, the lock  510  may include a U or fork shape that surrounds or otherwise restrains the seal  510  of the plunger  512 . In another aspect, the lock  510  may be internal to the plunger  512 , with arms or the like that expand to secure against the interior side(s) of the barrel  502 , such as by depressing a button or the like on the thumb rest  518 . Still more generally, it will be understood that a wide variety of locking mechanisms are known in the mechanical arts, and may be suitably adapted to secure the plunger  512  in relation to the barrel  502 . By securing the barrel  502  and plunger  512  in this or any similar manner, the syringe  500  may be secured by its end to a centrifuge and centrifuged without the barrel  502  releasing from the plunger  512  due to the forces of the centrifugation. 
     While a lock  510  is one suitable mechanism for securing the plunger to the barrel during centrifugation, it will be appreciated that other techniques may also, or instead be employed. For example, the opening  506  of the barrel may be fabricated to have a substantially smaller inner diameter than an outer diameter of the seal  514 , thus physically preventing separation of the barrel and plunger. While this approach may prevent fabrication, distribution, and clinical use as separate parts, it advantageously mitigates undesired separation of a barrel and plunger due to improper use of a locking mechanism such as the lock  510 . Similarly, a tether or the like may secure the seal to the interior of the lumen  504  nearest to the needle attachment point  508 . Thus it will be appreciated that a variety of techniques may be used instead of, or in addition to, the lock  510  to retain the plunger securely in the barrel  502  during centrifugation. 
     The barrel  502  may also include finger rests, flanges, or the like near the opening  506  to provide a point to manually apply pressure contrary to the thumb rest  518  when evacuating material from the lumen  504  during a procedure. In one aspect, barrel may be attached directly to a centrifuge, such as with a hinged or other rotating attachment including in, or attached to the finger rests, or otherwise positioned near the opening  506  end of the barrel  502 . 
     The plunger  512  may be formed of any suitable material, such as a rigid plastic or the like. The stem  516  should be sufficiently rigid to deliver force to evacuate the lumen  504  or to extract the plunger  512  from the barrel  502  during ordinary use. 
     The seal  514  may include any suitable seal for slidably engaging an interior wall of the barrel  502  and keeping material within the lumen  504 . This may include, for example, a soft rubber with a number of ribs, fins or the like that contact an interior wall of the barrel  502  (while permitting movement of the plunger  512  within the barrel  502 ). The seal  514  may also include a rigid portion that is retained within the barrel  502  by a rigid rib, flange, tab or the like on the interior wall of the barrel  502  near the opening  506  end thereof. The seal  514  may also include one or more holes, ridges, tabs, protrusions, or the like where the lock  510  can engage the seal  514  to prevent axial movement of the plunger  512 . 
     The thumb rest  518  may be a disk or the like suitably positioned, shaped and sized for an application of thumb force to the plunger  512  to evacuate material from the lumen  504  of the barrel  502 . In one aspect, the thumb rest  518  may include one or more holes  520  or other openings fabricated directly into the thumb rest  518  so that the plunger  512  can be hingeably secured to a centrifuge, e.g., on a hook or the like. These holes may be molded into the plunger  512  during fabrication, or pre-drilled into the thumb rest  518  (or similar plunger end) after the plunger  512  is fabricated using a casting or molding process. The thumb rest  518  may include any number of such holes. As depicted, these holes may be substantially parallel to a central axis of the syringe  500 . It will be understood that the hole(s) may also or instead be placed at any suitable angle for use as described herein. In another aspect, a tab, post or the like may extend from a top of the thumb rest  518 , with a hole drilled (or otherwise fabricated) in an orientation perpendicular to the central axis of the syringe  500 . 
     In another aspect, the plunger  512  may include an aspirator or the like for extracting material through the plunger  512  or seal  514  from the opening  506  end of the barrel  504 . In this manner, more complex substances that separate into multiple layers may be selectively extracted from the lumen  504  at the top or bottom (when the center axis is oriented vertically), thus permitting any desired layer of centrifuged material to be retained within the syringe  500 . 
     It will be understood that the centrifuge described herein may also be adapted for use with other syringes. For example, a conventional plunger with a planar thumb rest may be employed, and a corresponding fork or other attachment point may be provided on the centrifuge. The attachment point may be hinged or otherwise secured to the flywheel of the centrifuge to permit rotational or universal movement so that the syringe can swing outward during a centrifugation process (thus orienting the axis of the syringe to the centrifugal loading applied by the centrifuge). In another aspect, the flywheel may be adapted to connect to a syringe with a thumb loop or the like in a manner that securely attaches the syringe to the flywheel while permitting rotation of the syringe during centrifugation. 
     Other ergonomic features for a syringe are known and may be incorporated into the syringe  500  described above. For example, a large, padded thumb pad may be employed on the thumb rest  518 . A non-slip finger grip or the like may be used around the opening of the barrel for more secure manipulation of the syringe during use. An oval barrel may be used to prevent spinning of the barrel in a surgeon&#39;s fingers during use. All such variations are intended to fall within the scope of this disclosure. 
     In another aspect, disclosed herein are kits for use in the centrifugation procedures described above including for example various combinations of needles, plungers, syringe barrels, and centrifuge attachment hardware for attaching any of the foregoing to a flywheel or similar centrifuge mechanism. In particular, useful kits may include various disposable elements such as one or more barrels, plungers, needles, and the like adapted for use with a centrifuge described above. A kit may also include directions for use, disposal, and so forth. 
       FIG. 6  shows a syringe holder. As depicted, the syringe holder  600  may include an end support  602  near a first end  604  of the plunger  606  away from the flywheel (e.g., pointed out during centrifugation) and/or plunger support  608  toward a second end  610  of the plunger  606  that extends out from the barrel  620  of the syringe. 
     The plunger support  608  may include a plunger clasp  612  having fingers or the like that removably and replaceably engage the plunger  610 . The plunger clasp  612  may for example, include a hook-and-loop fastener such as Velcro that wraps around the plunger  610 . Other embodiments include metal or plastic fingers that springably engage the plunger  610  in a secure but removable fashion, or a band with a snap or other fastener to circumferentially secure the plunger  610  to the syringe holder  600  at a point along the length of the plunger  610  where it is outside the barrel  620  of the syringe. While the plunger clasp  612  is depicted as a clamp or band for securing the plunger  610 , it will be understood that other securing mechanisms may similarly be employed. For example, the plunger  610  may include a through-hole somewhere along its length positioned to engage a tab or other protrusion from the syringe holder  610 . The plunger  610  may also or instead include a tab or protrusion (e.g., from a flat surface, but within the cross-sectional interior of the barrel so that it does not interfere with movement of the plunger  610  into the barrel during normal use) and the syringe holder  610  may include a hole that fits over the tab, or optionally a series of holes so that the plunger  610  can be secured at a number of positions along its length, or so that it can be secured in a number of different positions relative to the barrel  620 . 
     The syringe holder  600  may also include a flywheel attachment  630 , which may be a loop, hook, snap, flange (where the flywheel has a suitable corresponding receptacle), or any other attachment mechanism to removably and replaceably secure the syringe holder  600  to a flywheel, or to a hinged fixture of a flywheel, in a manner that permits the barrel  620  to rotate radially outward during centrifugation. The end support  602  may include a forked or open end that fits around the barrel  620  of the syringe and engages the flanges  640  on the open end of the barrel  620 . The flanges  640  may be convention finger grips of a surgical syringe or flanges specifically adapted to securely rest within the end support  602 . The end support  602  may instead include a hole that completely encircles the barrel  620 . 
     In general, the barrel  620  may contain biomaterial such as extracted fat and other tissue. The mass of this biomaterial will tend to move the barrel  620  away from the flywheel at the end support  602 . The additional plunger support  608  may serve to retain the barrel  620  and plunger  610  in the syringe holder  600 , and to retain the entire syringe in alignment with the syringe holder  600  throughout a centrifugation process. Thus the end support  602  and plunger support  608  may cooperate to secure the entire syringe assembly in a manner that prevents or inhibits relative movement between the two components during handling, such as while the syringe is being centrifuged. 
     The syringe holder  600  may be shaped and sized for different sized syringes. For example, the syringe holder  600  may be sized to securely hold a 5 cc syringe barrel, a 60 cc syringe barrel, or a barrel of some other size. 
       FIG. 7  shows a syringe holder. The syringe holder  700  may in general be any of the syringe holders described above. In the embodiment of  FIG. 7 , a plunger support  702  includes a pair of fingers  704  that grip a planar support structure  706  of a plunger  708 . In this configuration, the plunger  708  may be conveniently rotated about an end support  710  into and out of the syringe holder  700  during use. The end support  710  may form a closed circle into which the barrel  712  may be inserted. In the embodiment of  FIG. 7 , an arm  714  extends from the end support  710  to the plunger support  704 , and further to a flywheel attachment  716 , which may be any of the attachments described above. It will be appreciated that the plunger support  702  secures a plunger at any point along its length. In the embodiment of  FIG. 7 , the plunger support  702  is positioned to secure the plunger at an end of its fully retracted length. 
       FIG. 8  illustrates the movement of a number of syringes on a syringe centrifuge during centrifugation. The syringe centrifuge  800  may, for example, be any of the centrifuges described above. The syringes generally move from a more vertical orientation  802  when the centrifuge is still to a more horizontal orientation  804  under the force of centrifugation, as indicated by an arrow  806 . In this manner force is applied to the contents of the syringe barrel so that denser materials move toward the bottom of the barrel or away from the center of the centrifuge. In the applications described herein, this process may be used for example to separate fat from other fluids and material that might be collected from a surgical site with the syringe and/or other surgical tools. In an embodiment, the syringes may be rotated at about 300 to 400 revolutions per minute during centrifugation. 
     The syringe centrifuge  800  may contain gears or other mechanical couplings as described above to deliver, e.g., 300-600 revolutions per minute at a hand-crank rate of about two cranks (or rotations) per second. With this gearing ratio, the syringe centrifuge may deliver up to eight 60 cc syringes of decanted fat over 2-3 minutes resulting in G forces of 20-60 G. This is in comparison to 1000-1300 G placed on adipocytes during conventional machine centrifugation using 10 cc syringes. Thus, in one embodiment as described herein, about 480 cc of decanted fat can be processed in 2-3 minutes. 
       FIG. 9  shows a cross section of a cap for a syringe. In surgical processes as contemplated herein, a syringe may be capped and uncapped several times. Where the syringe contains a material such as a fat, the material may tend to lubricate friction fits or the like that retain a cap for the syringe, particularly where the material extrudes out of the barrel and onto exterior regions of the syringe tip. This may result in poor capping strength that is unsuitable for centrifugation of other handling. In order to address the shortcomings of existing syringe caps in containing such fatty materials, a threaded cap may be employed. 
     In general, a cap  900  may have an open end  902  that fits about a tip  904  of a syringe, and a closed end  906  opposing the open end  902  that retains material within the syringe when the cap  900  is secured to the tip  904 . The cap  900  may be fabricated of stainless steel, aluminum or any other material that is biocompatible and/or sterilizable, and that is sufficiently hard to cut a plastic material of the tip  904  as described below. In one aspect, the cap  900  may be autoclavable for reuse. In another aspect, the cap  900  may be disposable. 
     The cap  900  may include a thread  908  disposed on an interior  912  of the cap  900  having a crest  910  that is pointed or otherwise brought to a sharp edge sufficient to cut into a tip  906  of a syringe  908 . Thus, the cap  900  can be screwed over the tip  906  and tightened to create grooves in the tip  906  to overcome any lubrication effects of material within the syringe  908 . In an embodiment, the cap  900  may be fabricated from a material such as a transparent plastic, and the thread  908  may be formed of a helical stainless steel element inserted into the cap  900  in a fabrication process. 
     The interior  912  of the cap  900  may be tapered along the threaded region (from where the thread begins to where it ends) so that a first diameter  914  toward the open end  902  is greater than a second diameter  916  toward the closed end  906  in order to improve error tolerance (in dimensions of the tip  906 ) and fit as the cap  900  is screwed on to the tip  906 . 
     The cap  900  may include one or more tabs  920  that provide finger grips for tightening the cap  900  on to the tip  904 . The tabs  920  may, for example, include two opposing tabs, which may be positioned, shaped, and sized for operation with a thumb and index finger. 
     By tightening the cap  900  with a sharp-crested steel thread about a tip of a syringe, the cap can score or otherwise cut in to the plastic tip to create a secure mechanical fit regardless of materials such as fat that might be disposed about the tip as a result of handling. 
       FIG. 10  shows a sterilization barrier for a centrifuge. A barrier  1000 , which may be formed of a sheet of material such as cloth, other fabric, or a flexible film. The barrier may be shaped to fit about a gearbox  1002  of a hand-cranked centrifuge. This may be a loose fit that drapes over the gearbox to accommodate various sizes of gearboxes and permit easy placement and removal of the barrier  1000 . In general, the barrier  1000  may be a sterilizable material to permit re-use, or a disposable material that is provided for use in a sterile package. The barrier  1000  may be sized to extend beyond the gearbox  1002  a sufficient distance along a working surface  1003  to form a sterile barrier between the gearbox  1002  and the surrounding environment, or the barrier  1000  may extend below the gearbox  1002  to envelope the gearbox  1002  in the barrier  1000 . Zippers, snaps or the like may be provided to secure the barrier  1000  about the gearbox  1002  in any desired fashion. 
     The barrier  1000  may include a first opening  1004  for a crankshaft  1006 , which may be any of the crankshafts described above. The first opening  1004  may be reinforced to prevent wear on the barrier  1000  by rotation of the crankshaft  1006 . The first opening  1004  may also or instead include a seal such as a gasket or the like, and/or the first opening  1004  may include a bearing. Thus in one aspect the first opening  1004  includes a gasket that fits securely to the crankshaft  1006 , held by a bearing that permits the gasket to rotate freely with the crankshaft  1006 . The first opening  1004  may also include a zipper, or a flap that can open and close about the crankshaft  1006  when the barrier  1000  is being placed or removed. 
     The barrier  1000  may include a second opening  1008  for a driveshaft  1010 , which may be any of the driveshafts described above. The second opening  1008  may be reinforced to prevent wear on the barrier  1000  by rotation of the driveshaft  1010 . The second opening  1008  may also or instead include a seal such as a gasket or the like, and/or the second opening  1008  may include a bearing. Thus in one aspect the second opening  1008  includes a gasket that fits securely to the driveshaft  1010 , held by a bearing that permits the gasket to rotate freely with the driveshaft  1010 . The second opening  1008  may also include a zipper, or a flap that can open and close about the driveshaft  1010  when the barrier  1000  is being placed or removed. 
     In operation, the gearbox  1002  may be placed on the working surface  1003  without the driveshaft  1010  or crankshaft  1006  inserted therein. The barrier  1000  may be sterilized, and then placed over the gearbox  1002  to enclose the gearbox  1002  in a sterile field. The driveshaft  1010  and crankshaft  1006 , which may also be sterilized, may then be inserted into the corresponding openings  1008 ,  1004  in the barrier  1000  and engaged to the gearbox  1002  as described in greater detail above. In this manner, the centrifuge may be used in environments requiring sterilization, without separately requiring that the gearbox  1002  be sterilized. This approach can advantageously reduce or eliminate the sterilization regime required for the gearbox  1002 , which may have complex mechanical parts and lubrication that are unsuitable for steam sterilization and the like. 
     While the invention has been disclosed in connection with the preferred embodiments shown and described in detail, various modifications and improvements thereon will become readily apparent to those skilled in the art. Accordingly, the spirit and scope of the present invention is not to be limited by the foregoing examples, but is to be understood in the broadest sense allowable by law.