Abstract:
An apparatus and method for harvesting bone using a manual, cylindrical, multi-directional coring device with a guided delivery system that can be inserted through a percutaneous or closed approach to extract precisely measured amounts of bone or bone marrow. A series of guide wires, obturators, dilators and cannulas are used as the exposure and delivery instrumentation for a cutting tool. The cutting tool has a tip with six cutting edges for cutting in all directions.

Description:
This application claims benefit of provisional application Ser. No. 60/082,340 filed Apr. 20, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     A percutaneous, closed, or mini-open bone harvesting method for orthopedic, neurosurgical, ear nose &amp; throat (ENT), oral, maxillo-facial, rheumatology, and bone marrow aspiration procedures. 
     Orthopedic, neurosurgical, spinal, ear-nose-throat, oral-maxillo-facial, and rheumatology procedures require the removal of bone or bone cells to culture or place in other parts of the body to permit fusion or bone formation. The current method for bone harvesting requires an open surgical procedure involving wide exposure of the iliac crests, ulna, radius, or femur. These areas are exposed with an incision over the donor sites, followed by the stripping of muscle to expose the donor site area. The removal of the bone is performed utilizing curettes, drills, or free-hand bone coring devices. 
     These open procedures usually cause very frequent donor site pain and morbidity as they involve significant incisional scarring, vast muscle stripping, damage to surrounding tissues, and over harvesting of the donor site. This has become one of the greatest complaints and problems of patients recovering from surgeries involving bone and bone marrow harvesting procedures. 
     Recently, inventors have begun creating “minimally invasive” methods to harvest bone. U.S. Pat. No. 5,556,399 to Huebner (1995) discloses a “coring drill used to harvest bone from a donor area of the human body.” This stainless steel device is the first device of its nature, and it is used freehand, under power, without guided controls and requires an open incision with wide muscle re-section. 
     In 1997, Spinetech, Inc. (Minneapolis, Minn.) released a patent pending “minimally invasive” cylindrical bone harvester that is used through a mini-open procedure, but without guided control. This device is not applicable to a percutaneous technique because it requires a large incision and muscle stripping to expose the donor site. The cutter is inserted into the donor site bone freehand. More importantly, the cutter tip is a uni-directional threaded two piece unit which must be disassembled to remove bone tissue from the collection tube. This makes the device unsuitable to a closed or percutaneous procedure due to the potential for disassembly inside the patient. Bi-directional cutting action will dislodge the cutter tip from the shaft. 
     Biomedical Enterprises, Inc. (San Antonio, Tex.) created the patent pending Bone &amp; Marrow Collection System (BMCS), which utilizes a manual or motor driven drill bit and a disposable collection tube. This technique provides limited initial drill stabilization, but does not guide or control the direction of the tip after cutting action begins. In addition, it still utilizes an open procedure and vast muscle resection. The BMCS is an auger-drill type that is lacking an adequate delivery system for placing the guidance tube through a percutaneous or closed technique. Also, the BMCS does not prevent the drill cutter from advancing too far into the donor site, thus violating the surrounding bony architecture, tissue, and muscle. The BMCS also does not provide an accurate and easy method to measure the amount of material captured by the drill and collection tube, and is extremely susceptible to frequent clogging during repositioning of the tip. 
     SUMMARY OF THE INVENTION 
     This invention relates to a disposable or reusable bone harvester specifically designed to operate through percutaneous, closed, or mini-open incisions during orthopedic, neurosurgical, ENT, oral-maxillofacial, rheumatology, and bone marrow aspiration procedures. 
     The present invention discloses a manual, cylindrical, multi-directional coring device utilizing a guided delivery system that can be inserted through a percutaneous or closed approach to extract precisely measured amounts of bone or bone marrow. The invention requires only a small incision, less that 2 cm above the donor site, and utilizes a guided delivery system of guide wires, obturators, dilators, and cannulas. The present invention makes a very small incision that gradually splits the muscle and tissue. The result is less blood loss, less tissue damage, and less donor site morbidity. 
     All other techniques including Huebner&#39;s, Spinetech&#39;s, and BME&#39;s require an open or mini-open incision. The first two techniques do not possess a method for guided control of the cutter tip, and the last gives only limited direction prior to the coring procedure. The disadvantages of the above techniques are:
         (A) A large or mini-open incision is required resulting in incisional scarring, greater blood loss, and exposure to airborne contaminants.   (B) Huebner, Spinetech, and BME all have uni-directional cutting tips.   (C) Spinetech&#39;s cutter has two pieces and can disassemble if used in a rocking motion. BME&#39;s collection tube can not fit through cannulas to guide the approach. These devices are not applicable to a closed percutaneous technique.   (D) All require a large open incision resulting in subsequent muscle stripping to expose donor site causing increased tissue damage, blood loss, and post-op pain.   (E) All require wide dissection and over harvesting of donor site due to inability to appropriately measure quantities of bone harvested resulting in greater blood loss, post-operative pain, increased recovery time, and donor site morbidity.   (F) All can potentially cause muscle and tissue destruction and/or bony fracture as a result of misguided or uncontrolled cutter tips.   (G) Coring depths are not controlled by depth stops on any of the existing inventions.       

     Accordingly, it is an object of the present invention to provide a method which permits bone to be harvested in precise quantities via a percutaneous or closed technique utilizing a series of guide wires, obturators, dilators, and cannulas as the exposure and delivery instrumentation for the cutting tool. 
     It is another object of the present invention to provide a multi-directional cutting tip with six cutting edges, which can be used to cut in clockwise, counterclockwise, or both directions, as well as with a downward force for rapid cutting action and morselization of graft material. 
     It is still another object of the present invention to provide multiple cannula sizes and shapes to accommodate different anatomic sites for a more precise fit, control, and tissue protection. 
     A further object of the present invention is to provide distal arms, or “teeth”, on the cannulas for stabilization and lateral control, which permit the cannula to move in an arc on the bony surfaces, facilitating multi-directional coring or sweeping of bone through the same incision. 
     Another object of the present invention is to provide a precise measurement system visible and calibrated along the proximal cylinder shaft to indicate depth of insertion and amount of material collected. 
     It is still another object of the present invention to provide a transparent, or translucent, bio-compatible, plastic cylindrical cutter shaft with a bonded, mechanically fastened, or ultrasonically welded permanently affixed stainless steel cutting tip forming a one-piece coring unit. 
     It is a further object of the present invention to provide a detachable and re-attachable T-Handle and/or Teardrop Handle. 
     It is also an object of the present invention to provide a calibration system on the proximal end of cutter shaft and a depth stop system to prevent the cutter from over harvesting bone, and advancing too far in the body. 
     Further objects of the invention may be provided with multiple sized cutting tips ranging in sizes from 8 mm, 10 mm, 12 mm, and 14 mm. These cutters can be utilized via laparoscopic techniques in addition to percutaneous, closed, and mini-open approaches. 
     These together with other objects of the invention, along with various features of novelty which characterize the invention, are pointed out with particularity in the claims annexed hereto and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated a preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an assembly illustration of the apparatus of the present invention. 
         FIG. 2A  is an illustration of the guide wire portion of the invention. 
         FIG. 2B  is an illustration of the obturator portion of the invention. 
         FIG. 2C  is an illustration of the dilator/toothed cannula portion of the invention. 
         FIG. 2D  is an illustration of the forked cannula portion of the invention. 
         FIG. 2E  is an illustration of the cutter cylinder portion of the invention. 
         FIG. 2F  is an illustration of the handle portion of the invention. 
         FIG. 2G  is an illustration of the offset plunger portion of the invention. 
         FIG. 3  is an assembled illustration of the guide wire, obturator and forked cannula. 
         FIG. 4  is an assembly illustration of the forked cannula, dilator/toothed cannula, cutter cylinder and handle. 
         FIG. 5  is a cross-sectional view of FIG.  4 . 
         FIG. 6A  is a perspective view of the cutter tip of the cutter cylinder. 
         FIG. 6B  is a bottom view of the cutter tip. 
         FIG. 7A  is an illustration showing the first major step of the present invention method for an iliac crest harvest. 
         FIG. 7B  shows the second major step of the method. 
         FIG. 7C  shows the third major step of the method. 
         FIG. 7D  shows the fourth major step of the method. 
         FIG. 7E  shows the fifth major step of the method. 
         FIG. 8  is an illustration showing the first major step of the present invention for other donor sites. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings in detail wherein like elements are indicated by like numerals, there is shown a bone harvesting method and apparatus used therein. As may be most clearly seen from  FIGS. 1 through 6 , the apparatus is comprised of a guidance system and cylindrical coring device for extracting precise amounts of bone  1  or bone marrow  2 . The apparatus system contains an elongated, generally cylindrical guide wire  10 , a generally cylindrical obturator  20  with an internal, hollow channel  21  formed along its elongated central axis and positioned concentrically over the guide wire  10 , a generally cylindrical, hollow dilator/toothed cannula  30  concentrically positioned over the obturator  20 , and a generally cylindrical, hollow forked cannula  40  concentrically positioned over the dilator  30 . The guide wire  10 , obturator  20  and dilator  30  are then removed and replaced with the cutter cylinder  50  with handle  70  attached. 
     The guide wire  10  is elongated and preferably made from stainless steel and has nominal dimensions of 3.2 mm×25 cm. The guide wire  10  has a pointed distal end  11  and a blunt proximal end  12 . The distal end  11  is defined as that end engaging a harvest site  3 . The obturator  20  is also preferably made from stainless steel and has a generally cylindrical shape. The obturator  20  has a dome-shape distal end  22  and a cross-hatched proximal end  23 . The proximal end  23  is cross-hatched to provide a better grip. The distal end  22  is used to split tissue for cannula placement as described below. A generally cylindrical channel  21  is centrally formed within the obturator  20  along its central, elongated axis extending from the distal end  22  to the proximal end  23 . The obturator  20  is placed over the guide wire  10  by positioning the obturator  20  so that its channel  21  is slid over the wire  10 . The dilator/toothed cannula  30  is also preferably made from stainless steel and has a cylindrical channel  31  is formed therein along its central, elongated axis extending from an open distal end  32  to an open proximal end  33 . There may be several dilators  30  having varied lengths, outer diameters and inner diameters. Each distal end  32  is beveled with teeth at its distal tip  34  similar to a hole saw. The forked cannula  40  is hollow and has a distal end  42  and a proximal end  41 . The distal end  42  is longitudinally notched resulting in two protruding arms  43  parallel to the central axis of the cannula  40 . The proximal end  41  terminates in two, parallel, block-like elements  44 . The forked cannula  40  is also preferably made from stainless steel and may have various inner and outer diameters and lengths. The cutter cylinder  50  has a proximal end  54  and distal end  55  with a hollow, transparent, or translucent, cylindrical biocompatible plastic tube  51  between. The distal end  55  has an attached stainless steel cutting tip  60 . The cutting tip  60  may be permanently attached by bonding means of mechanically fastened or ultrasonically welded. The cutter cylinder proximal end  54  has a groove  56  for mating with a T-handle  70 . The cutter cylinder  50  is nominally twenty-two centimeters in length, and comes in nominal eight, ten, twelve and fourteen centimeter diameters. 
     The cutting tip  60  has a proximal end  68  which attached to the cutter cylinder distal end  55 . The distal end  61  of the cutter tip  60  has two, protruding, generally triangular blades  62  with four cutting edges  63  to facilitate bi-directional cutting action. The protruding blade tips  64  are connected to each other. The cutter tip distal end  61  also terminates in two cutting edges  65  positioned between the protruding cutting blades  62  for multi-directional and downward cutting action. See, especially,  FIGS. 6A and 6B . As stated above the cutter cylinder proximal end  54  is joined to a T-handle  70  by means of an interference lock  72  on the T-handle distal end  71 . The interference lock  72  is comprised of a threaded and/or spring loaded section that interfaces and locks the cutter cylinder proximal end  54  to the handle  70 . The invention apparatus also includes an offset plunger  80  with a circular foot  81  on its distal end  82 , said foot  81  being adapted to push harvested bone  1  or bone marrow  2  out of the cutter cylinder tube  51 . 
       FIGS. 3 ,  4  and  5  illustrate the apparatus in the varying configurations required for the invention method.  FIG. 3  illustrates the invention assembly in an exposure mode, which includes the wire guide  10 , obturator  20 , dilator  30 , and forked cannula  40 .  FIG. 4  is an assembly illustration of the handle  70 , cutter cylinder  50 , dilator  30  and forked cannula  40  in a working model.  FIG. 5  is a cross-section view of the assembly of FIG.  4 . Referring also to  FIGS. 7A through 8 , the guide wire  10  is inserted through an incision  4  two centimeters or less until it abuts bone  1 . The guide wire proximal end  12  is gently tapped so that the guide wire distal end  11  enters into bone  1 . An obturator  20  is placed over the guide wire  10  to split muscle  5  over and around the guide wire  10  to create a wider working area until it abuts bone  1 . A dilator  30  is placed over the obturator  20  and guide wire  10  and continues to split muscle  5  as it is moved forward over the donor graft site  3 . A forked cannula  40  is then placed over the dilator  30 , obturator  20  and guide wire  10  until it abuts bone  1 . The guide wire  10  and obturator  20  are removed leaving a clear working channel through the forked cannula  40  and dilator  30 . The forked cannula  40  is gently tapped into final position over the harvest site  3 . The cutter cylinder  50  is attached to the handle  70  and inserted into the cannulas  30 ,  40 . The cannulas  30 ,  40  protect the cutter cylinder  50  and provide guided control for the cutter cylinder  50  and its cutting tip  60 . As may be most clearly seen from  FIGS. 7C and 7D , the combination of handle/cutter cylinder/cutting tip  70 ,  50 ,  60  is manually rotated into bone  1  in either a clockwise, counterclockwise, downward, and/or rocking fashion with both an uni-directional, bi-directional, and/or multi-directional cutting action. Bone  1  and/or bone marrow  2  material is captured in the cutter cylinder tube  51 . The handle  70  is detached from the cutter cylinder tube  51  and the captured material  1 ,  2  is pushed out with the offset plunger  80 . See FIG.  7 E. 
     Referring specifically to  FIGS. 2E ,  4  and  5 , the cutter cylinder  50  is comprised of an elongated biocompatible polycarbonate cylindrical collection shaft  51  with a permanently attached, ultrasonically welded, bonded, or mechanically fastened stainless steel cutting tip  60 . The cutter cylinder  50  may have multiple sizes including outside diameters of eight mm, ten mm, twelve mm, and fourteen mm diameters. The cutter cylinder  50  has two sets of printed, laser-etched, and/or silk-screened calibrations  52 ,  53 . The first set of calibrations  52  are cubic centimeter readings indicating the volume of material captured in the tube  51 . The second set of calibrations  53  are a built in depth measurement in centimeters fully readable with insertion of the cutter cylinder  50  through the dilator  30  and forked cannula  40 . As the cutter cylinder  50  is placed into the cannulas  30 ,  40 , the calibration reading  53 B will meet the proximal end  41  of the forked cannula  40  and will indicate a zero centimeter depth. As the cutter cylinder cutter tip  60  is enters into bone  1  the shaft  51  will move downward into the cannulas  30 ,  40 . The calibration reading  53 A will indicate that the cutter tip  60  has advanced five centimeters. 
     Referring again to  FIGS. 6A and 6B , the cutting tip  60  is a preferably made from stainless steel. The cutting tip  60  is hollow thereby permitting material from the cutting action to pass back into the cutter tip distal end  61 . The radial separation between cutting blades  62  is nominally 135 degrees to allow harvested material to pass into the cutting tip hollow interior  66 . The cutting blades  62  are flat and each formed at a 45 degree angle to the central longitudinal axis of the cutting tip  60 . The cutting edges  65  are also formed generally at a 45 degree angle to the central longitudinal axis of the cutting tip  60 . 
     As may be most clearly seen from  FIGS. 7 through 8 , the method of the present invention utilizing the present invention apparatus is illustrated for an iliac crest harvest and is as follows. First, a small incision  4  of less than two centimeters is made above the harvest site  3  to expose it. The medial wall of iliac crest is identified. A guide wire  10  having a pointed distal end  11  and blunt proximal end  12  is inserted into the incision  4 , distal end  11  first, and is positioned onto the medial superior surface of anterior or posterior iliac spine and is gently tapped into position into cortical bone  1 . An obturator  20  with hollow channel  21  is placed over the guide wire  10  and is guided down into the incision  4 , thus gradually splitting muscle  5  and tissue, until it contacts bone  1 . One or more dilators  30  are placed over the obturator  20  and guide wire  10  increasing the incision  4  according to a percutaneous approach. Up to three dilators  30  may be used where necessary to split tissue for the next major step. Next, a forked cannula  40  is placed over the dilator/s  30 , obturator  20 , and guide wire  10  until it is on the harvest site  3 . The guide wire  10  and obturator  20  are then removed to create a working channel for the cutter cylinder  50 . One or more dilators  30  may also be removed. An impactor cap  45  is placed over the cannula distal end  42  and gently tapped into position over the harvest site  3 . This facilitates guided control of the cutter tip  60 , and shields adjacent structures from subsequent damage. Moreover, the forked cannula  40  has protruding arms  43  enabling it to straddle or grab bone  1 . A cutter cylinder  50  is then joined to a handle  70 . The cutter cylinder  50  is then inserted into the cannula  40 , cutting tip  60  first. Bone  1  is then harvested with a slight downward pressure and uni- or bi-directional rotation. Bone material will enter through the cutting tip interior  66  into the cutter cylinder tube  51 . The depth calibrations  53  on the tube  51  provide measurements to determine insertion depth. In addition to protecting tissue, and guiding the cutter tip  60 , the forked cannula  40  also permits the cutting tip  60  to be maneuvered in an arcing motion to drill or sweep greater surface areas. This permits the cutting tip  60  to harvest bone  1  in multiple directions through the same incision  4  to collect greater quantities of material, without the captured material jamming or impeding the cutting tip  60 . Bone is then retrieved through precise measurements via calibrations on the cutter cylinder shaft  51  which are visible as the cutting tip  60  cores bone  1 . To collect greater amounts of bone, the forked cannula  40  may be rotated in multiple directions to channel more bone from the harvest site  3 . To remove the harvested bone material, the cutter cylinder tube  51  is removed from the handle  70 . The cutter cylinder proximal end  54  is positioned over a basin  57 , implant, or fusion site. Bone material is pushed out of the cutter cylinder tube  51  with the offset plunger  80 . When the appropriate amount of bone has been removed, the invention apparatus is removed from the incision  4  and the surgeon closes. 
     Although the iliac crest is the most popular area harvested, other anatomical sites may be indicated. For these areas, a small incision above the harvest site is made and the guide wire  10  inserted into cortical bone. An obturator  20  and dilator/toothed cannula  30  are placed over the wire guide  10 . The wire guide  10  and obturator  20  are removed and an impactor cap  45  is placed over the cannula  30  and tapped gently into the cortical surface. The methodology of using the cutter cylinder  50  as described above is the same. Basically the only difference between methods is the use or non-use of the forked cannula  40 . 
     It is understood that the above-described embodiment is merely illustrative of the application. Other embodiments may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope of the invention thereof.