Abstract:
Methods and apparatus are presented for extracting and collecting bone material from an extraction site of a patient. The method and apparatus further provides a readily accessible, and easily harvested, source of bone material without the drawbacks of current extraction methods.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This is a continuation-in-part of U.S. application Ser. No. 09/631,018, filed Aug. 2, 2000, which is a continuation of U.S. application Ser. No. 09/271,481, filed Mar. 17, 1999, now U.S. Pat. No. 6,110,176, which is a division of U.S. application Ser. No. 08/886,173, filed Jul. 1, 1997, now U.S. Pat. No. 5,913,859. 
     
    
     
       FIELD OF INVENTION  
         [0002]    The present invention relates generally to methods and apparatus for recovering bone material, such as bone marrow, bone, and contiguous tissue, from a patient and subsequent collection and storage.  
         BACKGROUND OF THE INVENTION  
         [0003]    There are a number of diseases in which the bone marrow is defective, such as aplastic anemia, some forms of leukemia, and deficiencies in the bone marrow caused by cancer treatments with drugs and irradiation. The treatment of choice for these diseases is bone marrow transplantation, provided a genetically compatible donor can be found. For instance, bone marrow transplants are significantly reducing the death toll from childhood leukemias.  
           [0004]    Bone marrow, also called myeloid tissue, is a soft, gelatinous tissue that fills the cavity of the bones. Human bone consists of a hard outer cortex and a soft medullary cavity that contains bone marrow. Bone marrow consists of stroma, or supporting tissues which have spaces packed by blood cells. Bone marrow is either red or yellow, depending upon the preponderance of vascular (red) or fatty (yellow) tissue. In humans, the red bone marrow forms all of the blood cells with the exception of the lymphocytes, which are produced in the marrow and reach their mature form in the lymphoid organs. Yellow bone marrow serves primarily as a storehouse for fats, but may be converted to red marrow under certain conditions, such as severe blood loss or fever. At birth, and until about the age of seven, all human marrow is red, as the need for new blood formation is high. Thereafter, fat tissue gradually replaces the red marrow, which in adults is found in the vertebrae, hips, breast bone, ribs, and skull, and at the ends of the long bones of the arms and legs, other cancellous, or spongy bones, and the central cavities of the long bones. In mammals, blood formation in adults takes place predominantly in the marrow. Because the white blood cells produced in the bone marrow are involved in the body&#39;s immune defenses, marrow transplants have been used to treat certain types of immune deficiencies. The sensitivity of marrow to damage by radiation and some anticancer drugs accounts for the tendency of these treatments to impair immunity.  
           [0005]    Bone marrow transplants can be divided into three groups according to the source of the marrow for transplantation. They are called autologous, syngeneic, or allogeneic. Autologous transplantation means that the bone marrow has been received directly from the recipient, and will be an exact genetic match. A syngeneic transplant comes from an identical twin of the recipient and will also be an exact genetic match. However, for allogeneic transplants, the bone marrow is provided by another person, and the possibility of exact genetic matching is very low.  
           [0006]    It is reported that approximately 12,000 bone marrow transplants were performed in 1992, approximately half of which were allogeneic and half autologous. Autologous transplantation has grown significantly during the past several years as improvements in procedures are made. The number of patients receiving allogeneic transplants is also rising due in large part because donor registries have increased the number of readily available donors. Advances in bone marrow transplantation techniques will likely continue to expand the use of the bone marrow transplant procedure.  
           [0007]    Generally, the recipient&#39;s sibling or parent will serve as the best source as the donor because of the high possibility of genetic matching. However, there are many cases where neither the parent nor the sibling will be a compatible genetic match for the recipient. There has been a recent increase in the use of bone marrow from unrelated donors which can provide genetic compatibility between the donor and recipient. This increase has been made possible through the existence of large bone marrow registries, such as the National Marrow Donor Program, and the American Bone Marrow Donor Registry. The drawback to these registries are the insufficient number of donors that genetically match closely enough with potential recipients to be of use.  
           [0008]    The success of the bone marrow transplantation technique depends heavily on genetically cross-matching the donor marrow cells to those of the recipient to prevent rejection. There is a significant tendency for the recipient patient to reject an allografted marrow because parts of the donor marrow will attack their new host. There is an additional hazard because immune system cells in a marrow graft can react against the patient&#39;s tissues, causing serious and sometimes fatal graft versus host disease. The ability to accept a bone marrow transplant (graft) from a donor, is dependent on the recipient sharing all of the donor&#39;s histocompatibility genes. To avoid graft versus host rejection in the past, special immunosuppressive treatment has been given. The use of monoclonal antibodies to selectively remove harmful lymphocytes from the donor marrow has been successful in some cases to prevent graft versus host disease. However, the risk remains that unless the bone marrow source is from the patient himself, an identical twin, sibling, parent, or other genetically compatible donor, that the bone marrow transplantation cannot take place because it will result in graft versus host rejection, and the failure of the treatment, and possibly the death of the recipient.  
           [0009]    Therefore, there is a significant need to collect and store genetically compatible bone marrow for use in cases where bone marrow transplantation is necessary to save the life of an individual. Because of the significant possibility that a donor cannot be found which is a close genetic match to the recipient, there is a need to collect and store an individual&#39;s own bone marrow while that individual is still healthy. If this is done, there will be a complete genetic match, and the dangers of graft versus host rejection will be eliminated which increases the success of the treatment.  
           [0010]    The collection of bone marrow for transplantation purposes is usually accomplished by inserting a needle into a donor&#39;s hip or pelvic bone. Several small incisions are made in the pelvic area, and the needle is inserted through these incisions approximately 25 to 30 times to withdraw the bone marrow from the bones. The extraction process typically lasts at least one hour or more, or until approximately 500 to 1000 milliliters of the donor&#39;s marrow is withdrawn. The donor will fully recover in approximately a few weeks when all the donated marrow has been replaced within the body. However, the extraction process is painful and there is typically soreness around the incisions until healing can occur.  
           [0011]    Typically, the donors also feel fatigued for some time after the procedure. The side effects to having donated bone marrow can vary from donor to donor. Infection from the incision is always a possibility. Additionally, blood loss can also occur, and proper medical attention is required. It is recommended that donors routinely store supplies of their own blood for infusion during and after the extraction procedure in cases of emergencies.  
           [0012]    Bone marrow can be obtained through biopsy or aspiration from the sternum or the calvarium in adults, and in long bones, such as the femur and tibia, in adolescents. Biopsy needles for extraction of solid bone marrow are known.  
           [0013]    Examples of such biopsy needles are U.S. Pat. Nos. 2,991,692; 2,426,535; 2,496,111; 4,272,676; 4,266,555; 4,543,966; 4,487,209; 4,840,184; and 4,922,602, which show the overall structure and orientation of the components. Needles used for aspiration of liquid bone marrow are disclosed in U.S. Pat. No. 4,469,109. Needles designed to both biopsy and aspirate bone marrow are disclosed in U.S. Pat. Nos. 2,496,111; 3,587,560; 5,012,818; and 5,357,974.  
           [0014]    There is a need for bone marrow extraction techniques that avoid the considerable inconvenience, discomfort, and pain due to current bone marrow extraction procedures and aspiration methods. Therefore, there is also a need to provide a method and apparatus to obtain both solid and liquid bone marrow from a donor with minimal intrusion and pain. There is also a need for the bone marrow to be stored for later use and is accomplished with relative ease.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a side elevational view of one embodiment of a bone marrow extraction apparatus constructed in accordance with the teachings of the present invention;  
         [0016]    [0016]FIG. 2 is an enlarged, fragmentary sectional view of the embodiment of FIG. 1;  
         [0017]    [0017]FIG. 3 is an enlarged, fragmentary sectional view of an alternative embodiment of the apparatus constructed in accordance with the teachings of the present invention;  
         [0018]    [0018]FIG. 4 is an enlarged, fragmentary sectional view of an alternative embodiment of the apparatus constructed in accordance with the teachings of the present invention;  
         [0019]    [0019]FIG. 5 is an enlarged, fragmentary sectional view of an alternative embodiment of the apparatus constructed in accordance with the teachings of the present invention;  
         [0020]    [0020]FIG. 6 is an enlarged, fragmentary side elevational view of yet another embodiment of an apparatus constructed in accordance with the present invention;  
         [0021]    [0021]FIG. 7 is a perspective view of shield adapted for use with a bone marrow extraction apparatus; and  
         [0022]    [0022]FIG. 8 is an enlarged side elevational view, in cross-section, of a collar and plug inserted into an entry port formed in a cortical bone layer. 
     
    
     DETAILED DESCRIPTION  
       [0023]    [0023]FIG. 1 illustrates the principles and concepts of a bone marrow extraction apparatus well adapted for use according to the invention. Shown in FIGS. 1 and 2 is an apparatus  10  capable of boring a hole in a jawbone  13  and extracting bone marrow therefrom. The apparatus  10  comprises a housing  17 , structure  20  attached to the housing  17  for extracting bone marrow from an extraction site, and structure  23  for collecting bone marrow extracted from the extraction site. While the embodiment of FIGS. 1 and 2 is illustrated and described herein for extracting marrow from a patient&#39;s jaw, it will be appreciated that the apparatus and methods may be used to extract marrow or other bone material, such as bone and contiguous tissue (including dental pulp) from other collection sites, as described in greater detail below.  
         [0024]    The housing  17  has a cavity  26 . A hollow shaft  29  having a conduit  30  and first and second end portions  32  and  35  is rotatably mounted in the housing  17  with the end portion  35  being disposed in the cavity  26 . The end portion  32  includes a bur  38  having a cutting flute  39  for boring a hole in the jawbone  13 . A beveled gear  41  is attached to the second end portion  35  of the hollow shaft  29 . While, in the current embodiment, the hollow shaft  29  is provided integrally with the beveled gear  41 , it will be appreciated that the hollow shaft  29  may be removably attached to the beveled gear  41  to facilitate bur replacement, as described more fully below with respect to the embodiment of FIG. 5. A drive gear  44  is matingly engaged to the beveled gear  41 . The drive gear  44  is connected by a shaft  47  to an electrical motor, a pneumatic motor, or other suitable equipment (not shown) for driving the drive gear  44 . The shaft  47  may be connected to the motor or other drive source by any feasible mechanical or other connection means. By engaging the shaft  47 , the drive source rotates the shaft  47  so as to cause rotation of bur  38 . As shown in FIG. 3, the shaft  47  may be adapted to be driven by a standard “E” motor.  
         [0025]    The housing  17  may have a first passage  50  in communication with the hollow shaft  29 . The first passage  50  is for passing irrigation fluid to the extraction site. The irrigation fluid passes through the passage  50  and then through the conduit  30  to the extraction site. The irrigation fluid cools the extraction site and adds liquid to the extracted fluids and solids to facilitate removal by suction. A source  51  (FIG. 1) of irrigation fluid may be connected to the housing  17  so that the source  51  is in communication with the first passage  50 . The housing  17  has a second passage  53  in communication with the cavity  26 . The second passage  53  is for passing bone marrow from the cavity  26  to a collection device  56  (FIG. 1). While the embodiment illustrated at FIG. 1 includes the first passage  50  for irrigation, it will be appreciated that the first passage  50  is not required and the apparatus may be used without irrigation, as described in greater detail below with respect to the embodiments of FIGS. 5 and 6.  
         [0026]    A suction tube  57  may be connected to the second passage  53  for extracting solid bone marrow from the medullary cavity of the donor. The rotating bur  38  and the suction tube  57  are preferably detachably connectible to the housing. The housing  17  may be a hand-held power unit. However, while the housing  17  may be formed in a generally cylindrical handle-type configuration as shown in FIG. 1, such apparatus may be of other forms, including a pistol grip-type configuration (not shown).  
         [0027]    Apparatus  10  may include structure for breaking up bone marrow into smaller particles prior to the entry of the particles into the second passage  53 . For example, a spiral cutting blade  59  may be attached to the outer surface of the hollow shaft  29  for breaking up particles while the hollow shaft  29  rotates. Additionally or alternatively, the cavity  26  may be defined by walls having ridges  62 . The ridges  62  break up the bone marrow into smaller particles as the particles pass through the cavity  26  into the second passage  53 .  
         [0028]    As shown in FIG. 4, the housing  17  may have a detachable portion  65 . At least a part of the second passage  53  is defined in the detachable portion  65 . Alternatively, the second passage  53  may be connected to the outside portion of the housing  17  of FIGS. 2 and 4.  
         [0029]    The suction tube  57 , which includes an integral valve  68  (FIG. 1), is attached to a vacuum source  71  (shown schematically in FIG. 1) at one end and a suction tip (not shown) at the other end. The integral valve  68 , which comprises a housing and a pivotal obturator, permits an operator of the apparatus to selectively produce suction through the suction tube  57  with one hand. See U.S. Pat. No. 5,295,830.  
         [0030]    A vacuum source  74  (FIG. 1) withdraws solid and liquid bone marrow from the medullary cavity into the suction tube  57 , which transfers the solid and liquid bone marrow to the collection device  56 .  
         [0031]    The apparatus  10  of FIGS. 1 and 2 could be used immediately before, during, or after a dental procedure or dental surgery. Thus, an adaption of the apparatus  10  described above which does not contain the rotating bur  38  is also in accordance with the present invention. Preferably, the rotating bur  38  incorporates an internal vacuum. More preferably, the configuration would be an entirely disposable unit designed to fit on a standard dental straight hand piece or to fit on a standard “E” motor, either air driven or electric.  
         [0032]    A biopsy needle  85 , shown schematically in FIG. 1, may be used in conjunction with the apparatus  10 . One configuration for utilizing the biopsy needle  85  includes a tube  80  (FIG. 1) in communication with the valve  68  and the suction tube  57 . The biopsy needle  85  may be connected at an end of the tube  80 . The valve  68  may be used to control whether suction is produced through the tube  57  (and therefore the apparatus  10 ), the tube  80 , or, if desired, both the tube  80  and the tube  57  simultaneously. When suction is produced in the tubes  57 ,  80  simultaneously, the biopsy needle  85  may be positioned adjacent the extraction site to provide extra suction and to otherwise assist the apparatus  10  in extracting bone marrow.  
         [0033]    Alternatively, an end  90  of the tube  57  may be removed from the housing  17 . A biopsy needle may be attached to the end  90  of the tube  57 . The biopsy needle may then be positioned adjacent the extraction site to assist in bone marrow extraction. In this configuration, all suction would be provided by the biopsy needle, because the apparatus  10  would not be in communication with the vacuum source  74 .  
         [0034]    A preferred embodiment has a rotating bur  38  that is oversized for vacuum collection. The rotating bur  38  may be made of, for example, carbides, stainless steel, or plastic, and comprises at least one large opening similar to internal irrigating burs used for implants, with a cuff as either an integral part of a disposal hand piece or attachable to the bur  38 , allowing free rotation of the forward portion only. The rotating bur  38  is connected to a vacuum hand piece similar to the housing  17 , such as disclosed in U.S. Pat. No. 3,863,635. The rotating bur  38  may also be contained within the suction tube  57 .  
         [0035]    The liquid bone marrow can be obtained from dental extraction sites using a heavy metal blunt instrument following dental extraction to compress the bone alone and integrated vacuum to collect the bone marrow.  
         [0036]    The apparatus  10  may include a solid bone marrow extraction portion having a first end and a second end. The first end is for collecting bone marrow. The apparatus  10  may also include a liquid bone marrow extraction portion comprising a first end and a second end. The first end is for breaking bone marrow stroma and aspirating the liquid marrow. Some conventional biopsy needles may be used to provide the solid bone marrow extraction portion and the liquid bone marrow extraction portion.  
         [0037]    The apparatus of FIG. 2 may further comprise an elongated stainless steel solid marrow pushing probe to express a solid marrow specimen outside the cavity  26  after the procedure. One example is shown in U.S. Pat. No. 5,012,818.  
         [0038]    The extraction of bone marrow from the jawbone during a dental procedure provides an advantage to the dental procedure alone in that it decreases the percentage of extraction sites experiencing dry sockets. This is due to the perforation of the compressed bone of the tooth socket.  
         [0039]    In an exemplar embodiment, the bone marrow extraction apparatus effects the removal of bone marrow and bone marrow fluid from a donor and mixes the removed bone marrow with a suitable form of solution, such as a mixture of anticoagulant and saline or electrolytic solution. The bone marrow and bone marrow fluid removed from the donor are then transferred either into a cell separator or a suitable collection bag, such as the collection chamber  56 , so as to permit separation of the bone marrow and fluid for subsequent processing and long-term storage. The collected bone marrow may also be used for the subsequent reinjection into the donor in future bone marrow transplantation procedures.  
         [0040]    In the removal of the bone marrow from the donor, a solution consisting of heparin or other anticoagulant compositions, together with a saline solution, can be mixed with the bone marrow and bone marrow fluid before, during, and/or after being transferred into separating or collecting means.  
         [0041]    The collection device  56  may be a bag containing chemicals for preserving bone marrow. The chemicals may be in the bag prior to the withdrawal of bone marrow from the jaw of a patient. In this manner, after bone marrow has been collected, the device  56  can be stored cold directly. Additionally or alternatively, chemicals can be added to the collection device  56  during or after collection of bone marrow to preserve the bone marrow. Suitable means for adding chemicals to a container such as the collection device  56  are well known in the art and may include penetrable membranes at specific locations on the collection device  56 .  
         [0042]    The collection device  56  is preferably collapsible so that air may be removed after collection has occurred. Removal of air increases the useful life of the bone marrow.  
         [0043]    From the foregoing, disclosed is a bone marrow collection apparatus which is easily adapted to conventional dental or medical equipment. A technical advantage of the extraction-removing equipment of the invention is that bone marrow can be more quickly removed than conventional extraction procedures.  
         [0044]    The dental apparatus according to the invention is not limited to that specifically disclosed and may comprise tools other than that described herein. Andre Schroeder et al.,  Oral Implantology , pages 66-71, 118-151, 178-187, 202-217, and 228-243 (George Thieme Verlag, 1988), discloses additional tools that are capable of boring holes in jawbones. Further, U.S. Pat. No. 4,564,374 discloses a device that is capable of extracting both solid and liquid bone marrow. Adaptation of this device may also be used in accordance with the present invention.  
         [0045]    In an exemplar method, a donor is positioned in a dental examination chair. A hole is formed in the donor&#39;s jawbone before, during, or immediately after a conventional dental procedure using the boring portion or bur  38  of the apparatus according to the present invention. The boring portion or bur  38  can also be used to break up the bone marrow after a hole is formed. The area of marrow extraction is sterilized with an antiseptic solution. The entire procedure of obtaining both solid and liquid bone marrow can be accomplished in less than one to two minutes. The large lumen is introduced into the previously made bore hole and pushed into the medullary cavity. The large lumen is pushed further into the marrow cavity with forward pressure in order to obtain solid marrow. The large round bur can simultaneously irrigate and vacuum.  
         [0046]    Liquid bone marrow sample is obtained by applying a negative pressure in the small lumen of the suction tube  57  using a vacuum source (not shown). This results in the breaking of marrow stroma and the release of fluid marrow.  
         [0047]    Referring now to FIG. 5, an alternative embodiment of a bone material extraction device  100  is shown having a removable abrading means  138 . As used herein, the phrase ‘bone material’ includes various hard bone materials (such as cortical bone), soft bone material (such as marrow), and contiguous tissue (such as dental pulp). The extraction device  100  includes a housing  117  through which a drive shaft  147  extends. As in the previous embodiments, an end of the drive shaft  147  is coupled to a motor (not shown) for rotating the shaft  147 . A drive gear  144  is attached to an opposite end of the shaft  147  and is matingly engaged to a bevel gear  141 . The bevel gear  141  includes an extension  142  having a connection end  143  disposed in a cavity  126  of the housing  117 . While not shown in the illustrated embodiment, a reduction gear may be provided to obtain the desired rotational speed.  
         [0048]    In the illustrated embodiment, the removable abrading means  138  is provided in the form of a bur having a bur head  137  attached to a shaft  129 . The bur shaft  129  is removably attached to the connection end  143  of the extension  142  via threaded connection, a clamp, or any other releasable connection means known in the art. The bur head  137  is positioned on a distal end of the bur shaft  129  and includes a cutting flute  139  for boring into bone material. Accordingly, rotation of the drive shaft  147  is transferred via the drive gear  144 , bevel gear  141 , and extension  142  to the bur shaft  129 , thereby to rotate the bur head  137 .  
         [0049]    The releasable connection provided by the removable bur  138  allows various types of burs to be used with the same hand piece housing  117 . For example, a first bur having a large cutting flute may be used for cutting through and/or harvesting cortical bone. When a sufficient bone material extraction site has been created, the first bur may be replaced with a second bur having a larger lumen to more efficiently harvest softer bone material such as marrow. In addition, worn out burs may be more easily replaced.  
         [0050]    In the embodiment of FIG. 5, a conduit  130  extends from the bur head  137  through the bur shaft  129  and extension  142  to a rear face of the bevel gear  141 . A passage  150  extending through the housing  117  is placed in fluid communication with the conduit  130 . A suction tube  157  may be connected to the passage  150  for extracting bone material from the extraction site. As a result, and in contrast to the previous embodiments, bone material is pulled through the conduit  130  formed in the bur shaft  129 . The suction tube  157  is connected to a vacuum source and a collection device for storing the extracted bone material.  
         [0051]    A second passage  153  may be formed in the housing  117  having one end in fluid communication with the cavity  126 . A source of irrigation fluid may be connected to the housing  117  to provide irrigation fluid at the extraction site. The second passage  153  for irrigation is not required, and the device  100  may be used without irrigation in a variety of applications.  
         [0052]    In a further embodiment illustrated in FIG. 6, an extraction apparatus  200  is shown that is suitable for use in relatively shallow bone material extraction sites. The apparatus  200  includes a bur  238  having a flexible shaft  229 . As in the previous embodiment, a conduit extends through the shaft and fluidly communicates with a suction tube, so that loose bone material is pulled through the bur  238 . The shaft  229  may be formed of plastic, solid metal, tightly wound spring, or other bendable material or structure. For certain structures, such as springs, the vacuum source must be sufficient to overcome the vacuum loss created by gaps in the shaft and still transport bone material through the bur  238 . The flexible shaft  229  may be prestressed to bend in a desired direction. The bur  238  with flexible shaft  229  illustrated in FIG. 6 is particularly suited for collecting bone material from areas where the space between cortical layers is relatively narrow, such as from the skull and sternum. The flexible shaft  229  frees the bur head to move in a radial direction, thereby increasing the yield of bone material from a single entry point in the cortical bone layer.  
         [0053]    [0053]FIG. 7 illustrates a shield  300  that may be used with an extraction apparatus  301  to assist in collecting bone material. The shield  300  may be formed of metal, plastic, or other materials. In an exemplar embodiment, the shield  300  is formed of a transparent, flexible material, such as silicone. The shield  300  has a connection end  302  and a receiving end  304 . The receiving end  304  defines an opening  306  sized to receive at least a portion of an extraction apparatus hand piece. A collar  308 , which may be in the form of an annular ring, is attached to the connection end  302  of the shield  300  and is sized for insertion into an entry port  307  formed in a cortical bone layer  309  (FIG. 8). The collar  308  includes releasable connection means, such as exterior threads  310  adapted to mate with complementary threads  311  in the entry port  307 . Alternatively, the collar  308  may include retaining tabs, may be sized for an interference fit in the port  307 , or may incorporate any other known releasable connection means.  
         [0054]    The collar  308  may further be releasably attached to the shield  300  so that the collar  308  may remain in place in the entry port  307  after the extraction process is complete. Accordingly, the collar  308  may be formed of any material used to augment bone or to serve as a resorbable membrane, such as collagen. If the collar  308  is to remain indefinitely or permanently in place, a plug  313  (FIG. 8) formed of a similar material may be inserted into the collar  308  to close off the entry port  307 .  
         [0055]    The shield  300  may include a moveable arm  312  for directing the bur head of an extraction apparatus having a flexible bur shaft, as shown in FIG. 7. The moveable arm  312  includes a grip end  314  positioned near the shield receiving end  304  that may be grasped by the user and rotated about the inside surface of the shield  300 . The arm  312  further has a directing tip  316  positioned proximal to the connection end  302  for engaging the bur shaft or head when the extraction apparatus is inserted into the shield  300 . Accordingly, as the arm  312  is rotated about the shield  300 , the directing tip  316  pushes the bur head toward a desired location and helps hold the bur head in the desired location as the bur shaft rotates.  
         [0056]    A gasket  320  is provided in a neck portion  322  of the shield  300 , as shown in FIG. 7. The gasket  320  defines an inner aperture  324  sized to closely fit a housing exterior of the extraction apparatus, thereby to assist in maintaining a sufficient vacuum level in the vicinity of the bur head.  
         [0057]    In addition to the benefits noted above, the shield  300  stabilizes the positioning of the extraction apparatus during a collection procedure by providing support, via engagement of the housing by the gasket  320 . The shield  300  may also help protect soft tissue when bone material is extracted from a site surrounded by such tissue.  
         [0058]    From the foregoing, it will be appreciated that the extraction apparatus described herein may be used to harvest bone material from a variety of sites. As disclosed above, bone material may be extracted from the jaw, sternum, and skull. In addition, the apparatus may collect bone material from other sites, such as the hip. Furthermore, as noted above, contiguous tissue such as dental pulp is included in the definition of ‘bone material’, as used herein. The methods and apparatus disclosed herein may be used to extract dental pulp from exfoliated teeth, for example.  
         [0059]    While a rotating bur has been described in the above embodiments, it will be appreciated that other bone material abrading means, such as a reciprocating file, may be used without departing from the scope of the present invention. Furthermore, while the illustrated burs are shown as being round, the abrading means, whether a bur, a file, or other device, may be in any shape or form suitable for abrading and extracting bone material.  
         [0060]    The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.