Abstract:
A bone grafting and/or shaping instrument includes a handle portion, a collection chamber and a blade. Features on the blade cooperate with features on the collection chamber to secure the blade to the collection chamber. A flexible joint between the collection chamber and the handle portion allows the user to orient the cutting edge of the blade in any desired position relative to the handle portion.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to the field of surgery. The invention has particular utility in connection with the removal and collection of bone from the surface of one or more donor sites, and the preparation and placement of the autogenous bone material at a second location in the patient, e.g. for use in grafting bone to osseous deficiencies, such as periodontal and dentoalveolar defects, bone deficiencies around dental implants, and numerous orthopedic applications that require grafting, and will be described in connection with such utility, although other utilities are contemplated.  
         BACKGROUND OF THE INVENTION  
         [0002]    Many reconstructive procedures used in medicine and dentistry involve the manipulation and healing of bones. Such procedures may involve changes in the position, orientation, shape and size of skeletal structures. A problem that is commonly encountered during such procedures is a lack of bone graft material. Bone graft material may be used in several applications, such as to fill between sections of bone that have been repositioned, to change surface geometry, or to add bone to an area that is deficient, such as in conjunction with periodontal surgery or dental implants in the patients&#39; jaws.  
           [0003]    The need to harvest small bone grafts from intraoral sites has been common in periodontal surgery to restore bone defects around teeth. In the case of dental implant surgery, bone grafts may be needed to augment atrophic alveolar ridges of the maxilla and/or mandible and the sinus floor to increase the dimension of these bone sites to accommodate and totally cover the endosseous portion of implant fixtures. Bone grafts also are used in conjunction with guided tissue regeneration; a technique that uses a membrane to isolate hard tissue from soft tissue sites and potentiates hard tissue healing.  
           [0004]    It is often difficult to harvest adequate amounts of autogenous bone from intraoral sites. Therefore, clinicians often rely on non-autogenous sources of graft material, such as bone from cadaver sources (homologous or allogenic grafts), animal sources (heterogenous or xenogeneic grafts), or synthetic bone substitutes. However, healing of non-autogenous material grafts is not as extensive or predictable as healing of autogenous bone; plus there is the additional cost of such non-autogenous graft materials, which can be significant.  
           [0005]    Clinicians use several techniques to remove bone for grafting for intraoral procedures. In one such technique rotary instruments, such as side cutting burrs or trephines, are used to remove a piece or section of cortical bone from a local intraoral site in the maxilla or mandible. The cortical bone is often morsalized into a particulate form, either manually with a rongeur like instrument or in a bone mill. The particulate bone is then combined with blood to form an osseous coagulum, which is then positioned and packed into the osseous defect around the teeth or implant. See Robinson, R. E. “Osseous Coagulum for Bone Induction”, J. Periodontology 40:503(1969). Suction devices with filters have been fabricated and manufactured to collect the bone dust from rotary instruments. See Hutchinson, R A “Utilization of an Osseous Coagulum Collection Filter”, J. Periodontology 44:668(1973). See also Goldman, et al., “Periodontal Therapy”, pp 994-1005, C. V. Mosby Co., (1980); and Haggarty, et al., “Autogenous Bone Grafts: A Revolution in the Treatment of Vertical Bone Defects”, J. Periodontology 42:626(1971). While such techniques are widely used by clinicians, the techniques have limitations, since sites to harvest sections of intraoral bone are limited in number and extent because of limited intraoral access, proximity to tooth roots, nerve structures and sinus cavities, and thin plates of bone.  
           [0006]    Other techniques for harvesting bone include using chisels or osteotomes to remove and manually collect shavings from the surface. These instruments must be very sharp and the process is often awkward and time consuming. Other manual instruments such as bone files and rasps also remove bone. However, the efficiency of cutting and the ability to use the removed bone is greatly limited. Another technique is to collect bone dust generated by twist drills or taps used to prepare the sites for implant placement. However, much of the bone material may be lost while the site is being irrigated to cool the cutting instrument. When larger amounts of bone are needed for major reconstructive procedures, other sites such as the hip (anterior or posterior ilium), tibia, ribs, or the calvarium often are used. However, using such other sites necessitates a second surgical site, which may require postoperative hospitalization, and thus is less amenable, e.g. in the case of an out-patient dental procedure.  
           [0007]    Various surgical devices have been proposed and/or are in use to harvest bone marrow samples for biopsy or devices such as rongeurs or bone cutters or punches to remove sections or convex edges of bone. Surgical devices also are in use in arthroscopy and endoscopy for cutting or drilling bone or tissue and removing the tissue fragments. Ultrasonic devices to cut bone also are in use; however, such devices require the removal of the irrigant and debris liberated by the apparatus. Each of these methods and/or devices, however, suffers from one or more deficiencies as applied to the collection of bone for grafting.  
           [0008]    Yet other patented devices have been proposed; each of these, however, suffers from one or more deficiencies:  
           [0009]    U.S. Pat. Nos. 5,403,317 and 5,269,785 to Bonutti show a method and apparatus for the percutaneous cutting and removal of tissue fragments from human. The Bonutti device removes the tissue fragments by suction where it can be collected and then placed elsewhere in the patient from where originally obtained. Bonutti employs a flexible drill, and suction to remove the debris to an externally placed collection reservoir, where it is compressed before being replaced into the patient.  
           [0010]    U.S. Pat. No. 2,526,662 to Hipps discloses a bone meal extractor apparatus for mechanically removing bone meal from a donor bone site through a small percutaneous site using a drill. The drill shavings, which comprise primarily sub-surface bone, are then evacuated into an open cut that the drill passes through, for collection.  
           [0011]    U.S. Pat. No. 4,798,213 to Doppelt teaches a device for obtaining a bone biopsy for diagnosis of various bone diseases. The Doppelt device is intended to remove a core of bone using a tubular drill, while maintaining the architecture of the tissue. The sample is obtained from the marrow space and not intended from re-implantation.  
           [0012]    U.S. Pat. No. 5,133,359 to Kedem shows a hard tissue biopsy instrument in which samples are taken using a rotatably driven hollow needle.  
           [0013]    U.S. Pat. No. 4,366,822 to Altshuler discloses a method and apparatus for bone marrow cell separation and analysis. The Altshuler apparatus collects bone marrow cells in a filtration chamber on a filter interposed between a needle directed into the bone marrow site and an aspirator or vacuum source, i.e. using negative pressure to withdrawal marrow cells through a needle.  
           [0014]    U.S. Pat. No. 5,052,411 to Schoolman teaches, a vacuum barrier attachment for shielding the operator of a medical tool from harmful aerosols and blood, etc. created by drilling, sawing types of actions, etc. The Schoolman device requires vacuum and is not intended for harvesting tissue for re-implantation.  
           [0015]    U.S. Pat. No. 4,722,338 to Wright et al. discloses a device instrument for removing bone that uses a shearing action similar to a rongeur to cut bone, with means for collecting fragments of bone as they are removed. The Wright et al. device reportedly is used mainly for the removal of projections or edges of bone using a shearing mechanism without the intent of harvesting the bone for grafting.  
           [0016]    U.S. Pat. No. 4,994,024 to Falk teaches an arthroscopy hook-clippers device that allows the unobstructed removal of tissue or bone with removal of the fragments by suction. The Falk device is intended for arthroscopy applications and with the removal of projections of tissue or bone and not specifically for the harvest of tissue for grafting.  
           [0017]    Yet other prior art devices are disclosed in U.S. Pat. No. 4,466,429 to Loscher et al. and U.S. Pat. No. 4,844,064 to Thimsen et al.  
           [0018]    The foregoing discussion of the prior art derives from my earlier PCT Application No. WO 97/11646, which describes a hand-held surgical instrument for the cutting, removal, and storage of bone surface shavings for use as autogenous bone grafts. The instrument is comprised of a blade mounted in a handle for holding and supporting said blade. The blade has a cutting structure adjacent its distal end. In a preferred form, the handle cooperates to provide a storage space adjacent the distal end of the blade for receiving harvested bone from the cutting structure. The instrument is held at an acute angle to the bone, and with minimal downward pressure, is drawn across the bone surface to cut and collect a thin shaving of bone. The blade is preferably retractable to allow the clinician access to harvested material. A plunger preferably is incorporated into the handle to serve both as a locking mechanism to secure the blade and as a means to advance and consolidate the bone in the distal aspect of the instrument.  
           [0019]    The present invention provides enhanced functionality and reduced cost over the surgical instrument described in my aforesaid PCT Application No. WO 97/11646.  
         SUMMARY OF THE INVENTION  
         [0020]    The invention is directed to a hand-held surgical instrument for the cutting, removal, and storage of bone surface shavings for use as autogenous bone grafts. The instrument is comprised of a blade and storage compartment coupled to a handle. The blade may be made from a section of metal that is oriented relative to a longitudinal axis of the handle to allow the operator to more easily cut or scrape and accumulate bone. The blade preferably is slid into place over a collection chamber and secured to prevent accidental removal. The collection chamber includes storage space adjacent the cutting edge of the blade for receiving harvested bone from the blade. The collection chamber may be coupled to a handle portion at a joint. The joint allows the user to orient the blade relative to the handle in order to access hard to reach locations. A pry bar may be employed to assist in removal of the blade from the collection chamber. The pry bar may be stored within the handle portion.  
           [0021]    In use, the blade and collection chamber is held at an acute angle to the bone and the user applies a minimal downward pressure as the tool is drawn across the bone surface. Thin shavings of bone are cut by the cutting edge and collected in the collection chamber. The clinician can view the amount of harvested material through an opening, preferably a slot, provided in the blade.  
           [0022]    In a preferred embodiment, the blade is removable and replaceable, while the handle is reusable.  
           [0023]    In another preferred embodiment of the invention, the handle has an area of reduced mechanical strength or a flexible joint displaced from the cutting edge, the area of reduced mechanical strength allowing the cutting edge to be angularly positioned relative to a longitudinal axis of the blade.  
           [0024]    The above and other objects, features, and advantages of the present invention will be apparent in the following detailed description thereof when read in conjunction with the appended drawings wherein the same reference numerals denote the same or similar parts, and wherein: 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]    [0025]FIG. 1 is a perspective view of an exemplary bone-harvesting instrument consistent with the present invention;  
         [0026]    [0026]FIG. 2 is an exploded view of the bone-harvesting instrument of FIG. 1;  
         [0027]    [0027]FIG. 3 is a profile view of the bone-harvesting instrument of FIG. 1;  
         [0028]    [0028]FIG. 4 is a perspective view of a portion of a second embodiment blade consistent with the present invention;  
         [0029]    [0029]FIG. 5 is a an exploded view of a portion of the bone-harvesting instrument of FIG. 1;  
         [0030]    [0030]FIG. 6 is a view similar to FIG. 1 of an alternative embodiment of bone-harvesting instrument consistent with the present invention; and  
         [0031]    [0031]FIG. 7 is a view similar to FIG. 6, and illustrating loading of a blade into the handle of the instrument.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0032]    [0032]FIG. 1 shows a bone-harvesting instrument  100 . The instrument  100  may have a handle portion  102 , a collection chamber  104  and a blade  106 . The handle portion  102  may have a first end  102 A and a second end  102 B. The handle portion  102  may have a removable end cap  150  in close proximity to the first end  102 A for storage of a blade removal tool  200  (see FIG. 3). In one embodiment, the collection chamber  104  may be coupled to the handle portion  102  through a flexible joint  108 . In a preferred embodiment of the invention, the flexible joint is an area of reduced mechanical strength. The area of reduced mechanical strength allows the cutting edge of the blade to be angularly and/or rotationally positioned to a desired angle and/or position relative to a longitudinal axis of the blade  106 . In another embodiment, the flexible joint may be a ball and socket joint.  
         [0033]    The area of reduced mechanical strength may be an area where the thickness is less than the thickness of a surrounding area. Alternatively, the area of reduced mechanical strength may be an area where the material has a lower yield strength than the surrounding area. The area of reduced mechanical strength allows the collection chamber  104  to flex relative to the handle portion  102 .  
         [0034]    [0034]FIG. 2 shows an exploded view of the instrument  100  with the blade  106  spaced from the collection chamber  104 . The collection chamber  104  preferably is a five-sided enclosure with a bottom  132 , sidewalls  134  and an end wall  136 . The interior volume of the collection chamber  104  may be used to hold accumulated bone shavings. The collection chamber  104  preferably is formed of stainless steel. Alternatively, collection chamber  104  may be molded from a polymeric material, preferably a medical grade plastic. The depth of the collection chamber  104  at the end opposite the end wall  136  preferably is less than the depth near the end wall  136 . This allows the instrument to be used to access hard-to-reach locations.  
         [0035]    A top surface  140  of the sidewall  134  defines a generally planar surface for supporting at least the cutting end of the blade  106 . Extending from the top surface  140  may be a pair of opposing upstanding retainer members  142  and a pair of opposing stabilizing members  144 . The retainer members  142  help secure the blade  106  to the collection chamber  104  during use and the stabilizing members  144  prevent the blade  106  from rotating. Each retainer member  142  includes a first cam surface  142 A, a second cam surface  142 B, and a ledge portion  142 C (see FIG. 5). The ledge portion  142 C helps maintain the blade  106  in contact with the top surface  140  and the cam surfaces  142 A and  142 B help resist linear movement of the blade  106 . The ledge preferably is spaced from the top surface  140  approximately the thickness of the blade  106 .  
         [0036]    In an alternative embodiment, a single pair of cam surfaces located on one side of the collection chamber are used to resist the linear movement of the blade  106 .  
         [0037]    In an alternative embodiment, a single stabilizing member, for example a post upwardly extending from the end wall  136 , cooperates with an opening in the blade  106  to prevent rotation of the blade  106 .  
         [0038]    The blade  106  may be stamped or machined from metal, preferably stainless steel, or other suitable materials with similar hardness. The blade  106  has a first end  110 , a second end  112 , a middle section  124  and at least one outwardly extending lobe  116 , preferably a pair of outwardly extending lobes. The first end  110  includes an aperture  116  adjacent at least a portion of a cutting edge  114 . Thus, the cutting edge  114  is drawn along a surface, generated shavings pass through the aperture  116  and are accumulated in the collection chamber  104 . An opening  118  extends along a longitudinal axis of the blade  106 . The opening  118  allows the user to visually check the amount of accumulated material and also provides a spring force to allow lobe/s  116  on the blade  106  to move inward to allow the blade  106  to pass the upstanding retainer members  142  on the collection chamber  104 .  
         [0039]    The second end  112  includes a stop mechanism  120  that prevents the blade  106  from traveling past its intended “use” position (see FIG. 3) and a protrusion  122  that can be used to help extract the blade  106  from the collection chamber  104 .  
         [0040]    To couple the blade  106  to the collection chamber  104 , the user first aligns the lobe/s  116  in the space between the upstanding retainer members  142  and the stabilizing member/s  144 . The user then applies a force (F) to the end surface of the blade  106  and directs the force along the longitudinal axis of the blade  106  towards the end wall  136 . The longitudinal force causes the lobe/s  116  on the blade  106  to contact the cam surface/s  142 A on the retainer member  142  of the collection chamber  104 . The cam surface/s  142 A applies a compressive force (F o ) to the lobe/s  116  urging the lobe/s towards the centerline of the blade  106 . The user continues to apply a longitudinal force to the blade  106  until the stop mechanism  120  on the blade  106  contacts the end wall  136  of the collection chamber  104 . The blade is now in the “use” position. In the “use” position, the lobe/s  116  preferably are partially returned to their original “relaxed” position so as to maintain a retaining force on cam surface  142 B.  
         [0041]    A tool  200 , as shown in FIG. 3, may be inserted between the protrusion  122  and the end wall  136  to decouple the blade  106  from the collection chamber  104 . The tool  200  includes one, and preferably two prongs coupled to a handle. The prongs are spaced a distance greater than the width of the stop mechanism  120 , but narrower than the width of the protrusion  122 . Alternatively, a pry bar may be inserted through an opening  124  (as shown in FIG. 4) in an end  112 ′ of a blade to extract the blade  106  from the collection chamber  104 .  
         [0042]    In an alternative embodiment, a blade may be inserted from the end opposite the end wall  136  and urged towards the end wall  136 . The collection chamber may include a stop mechanism that contacts a portion of the cutting end of the blade.  
         [0043]    Referring to FIGS. 6 and 7, there is illustrated an alternative embodiment of bone-harvesting instrument in accordance with the present invention. In this embodiment, two cantilevered springs  21  provide opposing forces that cause retention cams  9  to bear on pin follower  10  forcing blade tabs  13  forward against forward travel stops  19  and thereby securely retain blade  2  in its forward most position (loaded). In this position, blade  2  is also constrained laterally by side guides  22  and vertically by the blade tabs  13  being under the hold-down tabs  14 .  
         [0044]    Referring in particular to FIG. 7, blade loading is achieved by holding the blade  2  between a finger and thumb at the spring  21  end of blade  2 . Then it is placed between the side guides  22  while being angled and pulled backward causing blade catches  16  to contact back travel stops  15 . In this position, insertion opening  7  is aligned with pin follower  10  and blade  2  can be lowered. Next, blade ends  23  are pushed forward with a finger or thumb causing forces to be applied to insertion cams  8  contacting pin follower  10 . As more force is applied, the springs bend outwardly allowing blade  2  to move forward and eventually snap into loaded position as retention cams  9  bear on pin follower  10 .  
         [0045]    Blade removal is achieved using a prying instrument. Prying instrument  3  bears against handle pry surface  11  while it is pushed backward causing force to be applied to blade pry surface  24 .  
         [0046]    In the embodiment shown in FIGS. 6 and 7, instruments may be customized at the factory by bending reduced section  25  about the X-axis and/or Y-axis. A secure rotational grip, multiple facets, enables the surgeon to control the third degree of rotational freedom by simply gripping the handle at the desired Z-axis angle.  
         [0047]    In use cutting edge  114  (FIG. 2) or cutting edge  17  (FIG. 6) is placed in contact with the donor bone surface and pulled backward causing graft material to be cut and flow through aperture  16  (FIG. 2) or aperture  18  (FIG. 6) into collection chamber  104  (FIG. 2) or  20  (FIG. 6).  
         [0048]    Harvesting progress may be monitored by looking at view slot  118  (FIG. 2) or in the case of the FIG. 6 embodiment, distal view slot  4 , side view slots and/or proximal view slot  6  and observing graft material in or close to the slot. These slots  5  are sufficiently narrow so as to prevent material from falling through them.  
         [0049]    After the material is harvested, the blade may be removed, and interior volume of the collection chamber may be used as a mixing area. The mixing area may be used to mix shavings of scraped bone and blood with other materials such as xenogeneic bone, allogenic bone, alloplastic material (hydroxyapatite), platelet rich plasma, and/or recombinant growth factors (BMP) to make a composition that can be later applied to an area of a patient needing a bone graft. Acurette, or other standard instrument, may be used to move the graft material from the collection chamber to a desired recipient site.  
         [0050]    The bone-harvesting instrument of the present invention has many advantages. These include:  
         [0051]    (1) Low cost. Only three parts are used to provide all functions:  
         [0052]    (a) cutting edge;  
         [0053]    (b) aperture;  
         [0054]    (c) collection chamber;  
         [0055]    (d) view slots;  
         [0056]    (e) graft delivery nose;  
         [0057]    (f) customized head angles; and  
         [0058]    (g) secure retention mechanism: guides, springs, cams, follower, stops, tabs, pry surfaces, etc.  
         [0059]    (2) Highly secure blade retention. The angle on the face of insertion cams  8  is made shallow compared with the angle of the face on the retention cams  9 . This provides relatively easy insertion and very positive retention. The prying feature allows the surgeon to easily overcome the high retention force. Additionally, handle pry surface  11  is sloped to accommodate a range of standard instrument sizes that can be used as the pry instrument  3 . Thinner instruments may be positioned further down on the slope.  
         [0060]    (3) Durable retention mechanism. Dual springs apply opposing forces to the pin follower. Thus, very little force is applied to the handle material and handle wear is minimized. The pin follower can easily be made of a material that is harder than the blade (typically Rockwell 60C v. 55C) causing the blade to be the primary wearing part. Wear on the blades cams is not significant because blades may be replaced after a few uses (typically 1 to 4) to obtain new edges.  
         [0061]    (4) Easy blade loading. The design enables the surgeon to easily establish alignment of the small blade with the handle and to then snap it into place.  
         [0062]    (5) View slots. Slots in the blade are used in place of a plastic window. Therefore, components are autoclaveable and reuseable.  
         [0063]    (6) Angled head. Instruments can be readily customized at the users site by means of a flexible joint, e.g. ball and socket, or at the factory by bending reduced section  25  about the X-axis and/or the Y-axis. During surgery, the surgeon selects a handle with appropriate angles to facilitate access to the particular surgical site. Making all the handles the same, except for bends, enables them to use a common blade. Economies of scale result from producing more of the same parts. Inventory costs are also reduced.  
         [0064]    It should be understood that, while the present invention has been described in detail herein, the invention can be embodied otherwise without departing from the principles thereof, and such other embodiments are meant to come within the scope of the present invention as defined in the following claims.