Abstract:
The bone marrow mixing instrument having a handle housing with a trigger mounted thereto. The handle housing contains a ratchet drive feed mechanism with a pawl assembly and a moveable ratchet bar. The other end of the ratchet bar is secured to mixing housing which holds syringes filled with material and defines channels leading from the syringe area to a mixing nozzle removably mounted to the mixing housing. A piston rod and piston are mounted in each syringe containing bone defect material with a piston being advanced within the respective syringe by the feed mechanism to discharge bone defect material from the syringe into the adjacent channels in the mixing housing and into the mixing nozzle.

Description:
RELATED APPLICATIONS  
       [0001]     There are no related applications.  
       FIELD OF THE INVENTION  
       [0002]     The present invention generally relates to a bone marrow mixing instrument for the repair and replacement of the various portions of the human skeletal system. The present invention is specifically directed to provide a bone marrow mixing instrument having two cartridges, one containing bone marrow and one containing a scaffolding material such as demineralized bone material mounted on a pistol type handle with a trigger activated feeding mechanism. The bone marrow and scaffolding material composition is driven by a dual plunger/piston assembly into a mixing housing and exits the mixing housing via a nozzle on to the bone defect site.  
       BACKGROUND OF THE INVENTION  
       [0003]     Bone grafting is widely used to treat fractures and bone defect areas. Autogenous cancerous bone, which is taken from one site in the graftee and implanted in another site in the graftee, is currently the most effective bone graft and provides the scaffolding to support the distribution of the bone healing response and also provides the connective tissue progenitor cells which form new cartilage or bone. However, the harvest of autogenous bone results in significant cost and morbidity, including scars, blood loss, pain, prolonged operative and rehabilitation time and risk of infection. Furthermore, in some clinical settings, the volume of material necessary at the graft site can exceed the volume which can be extracted from the available autograft. Accordingly, alternatives to autografts have been developed in an attempt to reduce the problem of morbidity and cost of bone grafting procedures.  
         [0004]     Several purified or synthetic materials, including ceramics, biopolymers, processed allograft bone and collagen-based matrices have been investigated or developed to serve as substitutes for autografts. The FDA has approved a porous coral derived synthetic hydroxyapatite ceramic for use in contained bone defects. A purified collagen/ceramic composite material is also approved for use in acute long bone fractures. Although these materials avoid the morbidity involved in harvesting autografts from the graftee and eliminate problems associated with a limited amount of available autograft, the clinical effectiveness of the synthetic materials generally is less than autografts.  
         [0005]     Synthetic graft materials have also been used as carriers for bone marrow cells. When such composite materials have been implanted into skeletal defects, the connective tissue progenitor cells differentiated into skeletal tissue. In some instances, composite implants were made by soaking the synthetic graft material in a cell suspension obtained from bone marrow. However, the connective tissue progenitor cells, which have the capacity to differentiate into cartilage, bone and other connective tissue such as fat, muscle, and fibrous tissue are present in the bone marrow in very minute amounts. The numbers of such cells present in 1 ml of bone marrow varies widely from subject to subject ranging from about 100 cells to 20,000 cells depending to large extent on the age of the donor. This represents a mean of about one in 20,000 to one in 40,000 of the nucleated cells in bone marrow.  
         [0006]     Demineralized bone material from allogenic sources has been available for over fifty years and has been demonstrated to facilitate healing of bony defects created by trauma, disease or surgical intervention. Demineralized bone material (DBM) is provided as a dry powder and in various carriers to improve the convenience of handling and wound placement. DBM acts as an osteoconductive scaffold as well as having some osteoinductive properties (ability to induce surrounding patient cells to grow new bone) by virtue of bone morphogenetic proteins (BMP&#39;s) retained in the DBM after the demineralization process.  
         [0007]     Surgeons have previously used autologous bone, bone marrow and patient blood to provide osteoprogenitor cells to facilitate healing of bony defects. These procedures are highly effective to propagate new bone growth and accelerate wound healing. The use of bone chips and bone marrow taken from the patient&#39;s hip (iliac crest) or vertebral intertransverse processes, while providing an effective supply of osteogenic material, creates significant patient morbidity.  
         [0008]     As an alternative, bone marrow can be aspirated from the patient, usually from the iliac crest, vertebral body sternum or long bone condyle. This bone marrow aspirate (BMA) contains blood serum, red blood cells and some specific osteoprogenitor cells known as mesenchymal stem cells (MSC) or pluripotential cells. Orthopaedic surgeons have used bone marrow aspirate to facilitate wound healing in spinal fusion, fracture management or other skeletal defects. BMA alone is a slightly viscous, sticky liquid and is difficult to manage for delivery to an operative surgical location. Some workers have mixed BMA with demineralized bone matrix and gotten superior healing rates.  
         [0009]     The traditional and current technique involves removing BMA through a bone perforation biopsy-type device and collecting the BMA in a sterile syringe. The BMA is then discharged from the syringe into a container in the operating room. The DBM is then added to the BMA and manually mixed. DBM is provided in a sterile, freeze-dried granular form and delivered from a container, usually a glass bottle.  
         [0010]     This manual procedure makes it difficult to control the mix ratio. It may also compromise sterility, as the mixing is being done in the open in the operating room. Once mixed, the formulation may be held for a time ranging from a few minutes to up to an hour and risk drying out and becoming even more difficult to manipulate in the defect area. Finally, the delivery from the mixing container is usually done with a spatula, which results in waste, namely, material being left behind in the container and a loss of the precious bone and marrow cells. Vigorous mixing may also damage the cells in the marrow. The present invention thus overcomes these procedures which are difficult to implement: namely; time constraints, loss of sterility, preservation of cell viability and eliminate waste of material.  
         [0011]     The prior art has attempted to solve the problems which occur in mixing bone marrow with a scaffolding material. Isolated marrow cells from quail, in solution, were implanted or delivered via soaking in blocks of calcium phosphate ceramics, the soaked blocks being deposited in subcutaneous sites in a nude mouse. The osteogenesis is a biphasic phenomena in which donor cells are largely responsible for osteogenesis in the first three to four weeks and in the second phase, eight to twelve weeks post surgery the host cells actions predominate and begin to show the formation of marrow of host origin. “The Origin of Bone Formed in Composite Grafts of Porous Calcium Phosphate Ceramic Loaded with Marrow Cells”, by J. Goshima et al., Clinical Orthopaedics and Related Research, vol. 269, pp. 275-283 (1991) Also of interest in this reference is the discussion of prior art on page 281, col. 1.  
         [0012]     The use of a bone marrow cells in a bone graft is shown in several U.S. patents, namely, U.S. Pat. No. 5,824,084, issued Oct. 20, 1998 and U.S. Pat. No. 6,049,026 issued Apr. 11, 2000. These patents are directed toward a method for preparing a composite bone graft which includes providing a bone marrow aspirate suspension and passing the bone marrow aspirate suspension through a porous, biocompatible, implantable substrate, such as coralline hydroxyapatite, mineralized or demineralized cancerous bone sections, granules of demineralized bone, sintered cortical or cancerous bone and granular ceramics, to provide a composite bone graft having an enriched population of connective tissue progenitor cells. Because the method is preferably performed intraoperatively it reduces the number of occasions the graftee must undergo invasive procedures. The composite graft includes an enriched population of connective tissue progenitor cells and a greater number of connective tissue progenitor cells per unit volume than that found in the original bone marrow aspirate.  
         [0013]     It is also known in the art to use a piston ram carried in a trigger activated gun type device to dispense material carried a cartridge which is loaded into the gun type device. A representative patent showing this type of dispenser is shown in U.S. Pat. No. 4,826,053 issued May 2, 1989.  
       SUMMARY OF THE INVENTION  
       [0014]     The present invention is directed toward a pistol type bone marrow and demineralized bone mixing instrument utilizing a trigger which activates a rachet drive to advance plunger pistons in stacked syringe tubes containing demineralized bone material and bone marrow thus driving the same into a mixing head which discharge the mixed components at a predetermined ratio.  
         [0015]     It is an object of the invention to provide a bone marrow mixing instrument having an ergonomically shaped pistol type handle to assist a physician in inserting mixed bone and bone marrow into a patient&#39;s defect site.  
         [0016]     It is still another object of the invention to provide a bone marrow mixing instrument having a magazine which holds loaded syringe cartridges.  
         [0017]     It is yet another object of the invention, to provide for the mixing of DBM or other scaffolding material with bone marrow of the patient being operated upon at a predetermined ratio conducive to bone healing.  
         [0018]     It is a further object to provide a bone marrow instrument which mixes the bone marrow with a scaffolding material while precluding cell damage to the bone marrow cells.  
         [0019]     It is still another object of the invention to provide a bone marrow mixing instrument having locking member which holds the piston rods and piston heads in a fixed locked position inside syringe tubes used in the instrument.  
         [0020]     It is yet another object of the invention to provide a bone marrow mixing instrument which allows different nozzles having different mixing characteristics to be selectively mounted to the bone mixing instrument.  
         [0021]     These and other objects, advantages, and novel features of the present invention will become apparent when considered with the teachings contained in the detailed disclosure which along with the accompanying drawings constitute a part of this specification and illustrate embodiments of the invention which together with the description serve to explain the principles of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]      FIG. 1  is a perspective view of the inventive bone marrow mixing instrument;  
         [0023]      FIG. 2  is a side elevational view of the bone marrow mixing instrument of  FIG. 1  showing the plungers axes;  
         [0024]      FIG. 3  is an enlarged partial side view of the rachet bar of the mixing instrument;  
         [0025]      FIG. 3A  is an inverted enlarged tooth detail of the rachet bar of  FIG. 3  taken from circle  3 A;  
         [0026]      FIG. 4  is a side elevational view of the bone marrow mixing instrument of  FIG. 1  with various components shown in either cross section or phantom;  
         [0027]      FIG. 5  is a top plan view of the bone marrow mixing instrument of  FIG. 4  showing the line of travel of the piston of the piston heads and piston rods;  
         [0028]      FIG. 5A  is an enlarged isolated front view of the connector member shown in  FIGS. 4 and 5 ;  
         [0029]      FIG. 6  is an enlarged isolated partial sectional view showing sequential movement of the piston head in the syringe barrel of the bone material plunger assembly;  
         [0030]      FIG. 7  is an enlarged isolated partial sectional view showing sequential movement of the piston head in the syringe barrel of the bone marrow mixing plunger assembly;  
         [0031]      FIG. 8  is a side elevational view of the piston rod shown in  FIG. 6 ;  
         [0032]      FIG. 9  is a side elevational view of the piston rod shown in  FIG. 7 ;  
         [0033]      FIG. 10  is an enlarged cross sectional view of a piston head shown in  FIG. 6 ;  
         [0034]      FIG. 11  is an enlarged partial side view in phantom of the mixing housing of the instrument of  FIG. 1 ;  
         [0035]      FIG. 12  is a front elevation view of the mixing magazine of  FIG. 11 ;  
         [0036]      FIG. 13  is a side elevational view of a syringe barrel used in the invention with side walls shown in phantom;  
         [0037]      FIG. 14  is a front view of the left section of the handle housing;  
         [0038]      FIG. 15  is a side inner view of the section of the handle housing shown in  FIG. 14 ;  
         [0039]      FIG. 16  is a side inner view of the section of the handle housing shown in  FIG. 17 ;  
         [0040]      FIG. 17  is a front view of the right section of the handle housing;  
         [0041]      FIG. 18  is a rear cross sectional view of the handle assembly showing the locking mechanism;  
         [0042]      FIG. 19  is an isolated plan view of the locking plate shown in  FIG. 18  with the piston rod shown in phantom;  
         [0043]      FIG. 20  is a front elevational view of the trigger member;  
         [0044]      FIG. 21  is a side view of the trigger member shown in  FIG. 20 ; and  
         [0045]      FIG. 22  is a rear view of the trigger member shown in  FIG. 20 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0046]     The preferred embodiment and best mode of the invention is shown in  FIGS. 1 through 22 . While the invention is described in connection with certain preferred embodiments, it is not intended that the present invention be so limited. On the contrary, it is intended to cover all alternatives, modifications, and equivalent arrangements as may be included within the spirit and scope of the invention as defined by the appended claims.  
         [0047]     The present invention is directed a gun type bone marrow mixing instrument  20  for receiving bone marrow collected from a patient, mixing it with mineralized bone material, demineralized or partially demineralized bone material (DBM) such as DBX® manufactured by the Musculoskeletal Transplant Foundation, ceramics or other biocompatible materials in a predetermined precise ratio of marrow to DBM and delivering it directly to a bone defect site via a closed system. The DBM is in a pre-mixed form in a viscous excipient such as sodium hyaluronate or its derivation (HA). The HA is best formulated at physiological pH (6.5-7.5) and isotonic osmolality (250˜330 in Osmol/kg).  
         [0048]     The delivery of bone marrow aspirate (BMA) into the surgical defect is difficult. The ratio of BMA to DBM is important. If there is too little BMA, the mixture is dry, grainy and has only a limited number of the osteogenic MSC&#39;s. Too much BMA and the mixture may be excessively sticky and of low viscosity, making it difficult to place the mixture in the operative site and problematical to retain it in position. Optimal ratios of BMA to DBM range from 1:1 to 6:1 (v/v) with a preferred ratio being 1:3.  
         [0049]     The bone marrow mixing instrument  20  is constructed with a premolded handle assembly  30  having a rachet drive assembly  40  mounted therein which is advanced by a trigger mechanism  52  so that dual plunger or piston assemblies  60  and  70  as more clearly shown in  FIGS. 6 and 7  are driven into their respective syringe tubes or barrels  62  and  72  to discharge the respective materials contained therein (bone marrow aspirate and scaffolding material) outside of the distal ends  64  and  74  of the respective syringe tubes. The demineralized bone material is preferably preloaded in a sterilized syringe tube in a kit together with a sterilized syringe for the BMA together with the respective plunger or piston assemblies for the syringe tubes which are described in detail below. The handle assembly  30  is formed with two sections  32  and  34  which are molded halves and are preferably heat sealed together or sealed with a suitable adhesive. Each half contains a drive housing section  33  and a handle section  35 . The handle section  35  has a hollow interior with piston rod seats  36  and  38  and defines rachet bar slots  37  and pawl slots  39 . The right handle section  34  is provided with a locking slot  40  through which locking member shaft  106  protrudes. The outer surface of the handle section is marked with colored lock and unlock indicia  41  adjacent the shaft knob  108  as seen in  FIG. 2  which may be in the form of dots or lines to indicate locked and unlocked positions. The handle is preferably constructed of a suitable plastic which can be autoclaved or easily sterilized.  
         [0050]     A toothed rachet bar  42  is mounted in handle slots  37 . The rachet bar  42  is constructed of stainless steel  316  having an angled distal end  43  and a rounded proximal end  44  as shown in  FIG. 3 . One end wall  45  of the bar  42  is planar and the other end wall  46  has a plurality of teeth  47  disposed therein. The teeth are shown in more detail in  FIG. 3A  and have a pitch of 0.204±0.002 inches with a flat tooth surface  49  of 0.030 inches. The distal end  43  has several throughgoing apertures  48  which are adapted to receive pins  49  which are inserted through holes  50  formed in the mixing housing  80 .  
         [0051]     The piston or plunger assemblies  60  and  70  have their respective piston rods  66 , 76  mounted in seats  36  and  38  formed in the handle. The piston rods  66 ,  76  of the piston assemblies each are formed with a central rod  67 ,  77  around which a plurality of spaced circular retainer members  68 ,  78  are placed. The spaced circular retainer members  68 ,  78  which are preferably 0.062±0.002 inches in width extend outward from the respective central rod and are spaced the same distance from each other to receive a locking member  100  as described below. As shown in  FIGS. 8 and 9  each central piston rod terminates in a piston head retainer member  71  which has transverse fins  77  with circular caps on each end or the retainer member is alternatively square. A post  73  extends from the distal cap and terminates in a head member  75  of a greater diameter then the post  73  with a rounded outer surface. The post  73  and head  75  snap fits into a stepped blind bore  80  of a resilient piston head  79 . The piston head  69 ,  79  as shown in  FIGS. 6, 7  and  10  defines a cylindrical stepped end chamber  80  which fits over piston head retainer member  75 , a circular end ring  81  and a cone shaped head  82  which fits into the tapered syringe tube distal end ( 64 ,  74 ). The cone shaped head can be provided with various tips  83  as shown in  FIGS. 4 and 10 . The larger diameter of the cone shaped head  82   a  has a diameter equal to or slightly larger than that of the circular ring  81  and tightly fits into the barrel of the respective syringe and is slidably moved therein The piston head is preferably made of Helvot Pharma FM 257/2 or equivalent manufactured by Precision Polymer Products Inc. and is silicone coated with Nu-Sil MED-360 cs or equivalent.  
         [0052]     The trigger mechanism  52  comprises a trigger body  54  which is mounted by a pin  55  to the handle assembly  30 . The pin  55  extends through bores  55   a . The trigger body  54  defines a spring cavity  55  which holds one end of a bracing spring  56 , the other end being held in a handle so that the trigger body  54  is continuously biased away from the handle. The biasing spring  56  as shown in phantom in  FIG. 4  is preferably 0.010 spring stainless steel. The other end of the trigger body defines a yoke  58  with a closed distal end  59 . The trigger mechanism is mounted to the handle housing by a pin  55 . A pawl  60  is mounted on a pin  61  which is mounted in bore  61   a  cut into the yoke arms and extends across the yoke arms. The pin is preferably made of stainless steel  316  and is structured so that it is chamfered at one end and has a head on the opposite end. One end  62  of the pawl  60  is biased downward by a coil spring  63  which engages the planar upper surface of the pawl with the other end of the coil spring being mounted around a post  65  integrally formed with the handle housing. Since the pawl  60  is bent as can be seen in  FIG. 4 , the other end adjacent the pin seat engages the toothed surface  46  of the rachet bar driving the rachet bar one tooth length rearward as the trigger is pulled. When the pawl  60  is driven backward and upward by action of the trigger body, the rear end of the pawl engages a tooth  47  of the rachet bar to drive the same one tooth length of the rachet bar.  
         [0053]     The small syringe tube  62  preferably contains bone marrow previously collected by the surgeon from the patient while the larger syringe tube  72  contains a demineralized or partially demineralized bone material which has been previously placed in the syringe in a sealed sterile condition. Both syringe tubes  62  and  72  are mounted in chambers  84  and  86  respectively which are formed in the mixing housing as shown in  FIG. 11 . Different syringe tube diameters can be provided to obtain the ratio of mixture desired. The syringe tube holding portion of the mixing housing has a  FIG. 8  cross section.  
         [0054]     A locking member  100  as shown in  FIG. 19  is constructed of stainless steel in the form of a planar base plate  102  with two L shaped cut out recesses  104  with curved ends  105  that allow entry over the plunger or piston rod  67 ,  77  between the circular segmented portions  68 ,  78 . The locking member locks both plunger assemblies in relation to each other and also allows for varying positions of the same. An extension rod or lock shaft  106  extends transversely outward from the plate  102  through handle slot  40  with the end  107  of the shaft being provided with a plurality of angled cuts to aid in securing the end  107  to knob  108 . The lock shaft  106  has an end cap or knob  108  mounted to its distal end over the angled cuts to allow the user to easily move the locking member in a locked and unlocked position which may be indicated on the housing by markings or color indicia as shown in  FIG. 2 . The position of piston assemblies  60  and  70  in the locking member  100  is shown in phantom in  FIGS. 18 and 19 .  
         [0055]     The mixing housing  80  as shown in  FIG. 8  defines a lower chamber  82  as seen in  FIG. 11  which seats and holds the distal end  43  of rachet bar  42  in a fixed position so that the mixing housing  80  is driven backwards toward the handle  30  causing the pistons to be driven forward in the respective syringe barrels  62  and  72  driving the materials contained therein to be forced out of the respective barrels or tubes along the curved mixing passageways or conduits  85  and  87  in the mixing housing to nozzle connector  90 . The nozzle connector member  90  which is shown in  FIGS. 5 and 5 A is secured to the distal end of the mixing housing  80  and defines a central chamber  92  which is axially aligned with nozzle  200 . The nozzle connector member  90  has two opposed flanges  94  which define a space  96  between the bottom of the flanges and the top surface  91  of the connector member. A circular boss  93  surrounds the outlet for the central chamber  92  and extends away from the top surface  91  of the connector to form a seat for nozzle  200 . The mixing housing is preferably constructed of the same plastic material as the handle housing and the trigger mechanism.  
         [0056]     The nozzle  200  which is removably mounted on the nozzle connector member  90  via the locking flange structure  94  formed on the nozzle connector  90 . The nozzle is constructed with a base plate  202  which has two curved ends  204  and linear sides  206  allowing the same to be inserted in the nozzle connector  90  with the bore  208  of the tube of the nozzle being seated over the circular boss  93  of the connector member  90 . The nozzle is rotated so that the base plate curved ends  204  are frictionally held within space  96 . The nozzle tube has exterior fluting  210  to aid in rotating the nozzle to lock the same in the connector  90 . Mounted within the bore of the tube  208  is a helix  212  which is curved at an angle around 30° which reduces the forces acting on the marrow cells as they are mixed and discharged from the nozzle. The nozzle diameter is highly polished and provided clearance for the delivered material. It is important to note that when delivering marrow to the wound site, that cells can be damaged by corners, edges and rough surfaces as well as by force. The present invention allows for a short path for the marrow to travel with no edges and sharp turns. The path surface can be polished or coated with Teflon®, silicone or other low friction material which will lower shear stresses on the cells.  
         [0057]     In operation, the surgeon perforates the patient&#39;s bone (ilea, vertebra, sternum or long bone condyle). The bone marrow is withdrawn, i.e., aspirated from the bone into the syringe tube  62 . This syringe  62  is provided empty and is coated with heparin. This syringe has a luer lock tip  63  which mates with the proximal end of a separate bone marrow aspirate device. The empty, heparin coated syringe is used to withdraw the bone marrow from the patient&#39;s bone. Three to five cubic centimeters of bone marrow aspirate (BMA) may be collected in the second syringe. When it is filled, it will be placed into a receiving chamber  84  in the mixing housing and be adjacent and parallel to the first syringe  72  which, in this example holds the premixed demineralized bone material (DBM) and hyaluronic acid (HA) scaffoling material. This mixture is a flowable paste or putty and is within the property range previously disclosed.  
         [0058]     A piston or plunger assembly is then placed rearward of the two syringe tubes with the piston head inside the tube and the assembly is inserted into the applicator gun. This plunger is sized to a specific pre-set volume and matches the actual BMA volume chosen and collected.  
         [0059]     The operator squeezes the trigger of the applicator device and the rachet drive propels the contents of both syringe tubes simultaneously into and through the mixing tip/nozzle. The bone marrow will intermix with the DBM/HA as they simultaneously pass through the mixing tip/nozzle. The combined materials are then placed in the wound site by the surgeon.  
         [0060]     The plunger assemblies shown in  FIGS. 6 and 7  can be sized to be compatible with the BMA volume collected and the DBM/HA volume in syringe number. This is achieved by the diameter of the plunger on the number 2 syringe (BMA) side. This dual syringe system provides a simple and precise way to collect, mix and deliver in a sterile manner a mixture of DBM and BMA in a range of 1:1 to 1:6, preferably a 1:3 ratio or BMA to DBM to the wound or bone defect site. Thus, the kit can hold these different sized diameter syringe tubes to allow the surgeon to select the ratio desired.  
         [0061]     The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. However, the invention should not be construed as limited to the particular embodiments which have been described above. Instead, the embodiments described here should be regarded as illustrative rather than restrictive. Variations and changes may be made by others without departing from the scope of the present inventions defined by the following claims.