Abstract:
A surgical bur is disclosed having cutting and trailing edges and associated flutes and lands. Each flute includes a cutting edge. Each of the trailing edges relatives in a selected dimension to a preceding cutting edge.

Description:
FIELD 
       [0001]    The disclosure relates to a surgical systems for bone cutting or shaping, and more particularly to surgical burs. 
       BACKGROUND 
       [0002]    This section provides background information related to the present disclosure which is not necessarily prior art. 
         [0003]    Surgical burs need sharp and durable cutting edges in order to efficiently dissect, cut, and/or shape bone during a surgical procedure. Human anatomy tends to locate sensitive soft tissue structures, such as nerves and blood vessels, near bones for protection. These structures can include the dura mater. Dura mater, or dura, refers to the outermost layer of protective soft tissue surrounding the brain and spinal column of a patient. During cranial and spinal procedures, the distal end of a bur can come in contact with dura mater. The term “distal” means away from a medical practitioner holding a surgical tool with a rotating bur. The term “proximal” means towards the medical practitioner and away from the patient. 
         [0004]    It is desirable for the surgical burs to provide stability while drilling in an axial direction and to be able to efficiently cut while being moved in a radial direction. The axial direction may be, for example, a direction parallel to, along, and/or in line with a longitudinal axis of the surgical bur. The radial direction may be, for example, a direction away from and not parallel to the longitudinal axis of the surgical bur. The radial direction may be a direction away from and/or perpendicular to the longitudinal axis. 
       SUMMARY 
       [0005]    This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
         [0006]    A surgical bur is disclosed, the bur may include flutes and lands. Each of the flutes includes a cutting edge, rake surfaces, and a clearance surface. Each of the lands is disposed between a pair of the flutes. Each of the flutes may have multiple rake surfaces with respective rake angles. Each of the lands is disposed between a pair of the flutes. 
         [0007]    A surgical bur may further include a trailing edge that follows the cutting edge. In operation, the surgical bur may rotate so that a cutting edge is configured to cut bone as the surgical bur rotates in a selected direction. The trailing edge may follow the cutting edge as the surgical bur rotates. The trailing edge may also engage bone, but not cut the bone. 
         [0008]    Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0009]    The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
           [0010]      FIG. 1  is a perspective environmental view of a surgical dissection cutter assembly incorporating a surgical bur and in use on a patient in accordance with an embodiment of the present disclosure. 
           [0011]      FIG. 2  is a perspective view of the surgical dissection cutter assembly of  FIG. 1 . 
           [0012]      FIG. 3  is a detail front perspective view of a surgical bur. 
           [0013]      FIG. 4  is a front detail view of the surgical bur of  FIG. 3 . 
           [0014]      FIG. 5  is a side view of the surgical bur of  FIG. 3 . 
           [0015]      FIG. 6  is a detail front perspective view of a surgical bur. 
           [0016]      FIG. 7  is a front detail view of the surgical bur of  FIG. 6 . 
           [0017]      FIG. 8  is a side view of the surgical bur of  FIG. 6 . 
           [0018]      FIG. 9A  is a detail environmental view of the surgical bur of  FIG. 3  in use in a first position. 
           [0019]      FIG. 9B  is a detail environmental view of the surgical bur of  FIG. 3  in use in a second position. 
       
    
    
       [0020]    Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION 
       [0021]    The following description includes disclosure of rotatable surgical burs (also referred to below as the surgical burs). Cutting edges and trailing edges, as disclosed below. The surgical burs may include one or more of a plurality of external geometries, such as a ball, a cylindrical, an oval, or other generally known shape, such as the Midas Rex® surgical burs sold by Medtronic, Inc. having a place of business in Minneapolis, Minn.. Surgical burs, including those disclosed herein, may be driven by high speed drills, such as the Midas Rex® Legend EHS Stylus High-Speed Surgical Drill which may be appropriate for a wide range of surgeries, including spine, neurology, and ear-nose-throat (ENT) procedures. The drills may drive the burs at appropriate and selectable speeds, such as about 200 to 75,000 rotations per minute (rpm), including about 7,000 to 70,000 rpms. 
         [0022]    Example embodiments will now be described more fully with reference to the accompanying drawings. The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. For example, although a human patient is illustrated as a subject, it is under stood that a subject may be any appropriate subject. Further, the subject may include inanimate and non-living subjects. Non-living subjects may include solid working materials such as a objects formed of wood, ceramics, metal, etc. Certain tissues, such as bone tissue, may be rigid and may be shaped with a cutting tool. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
         [0023]      FIG. 1  shows a surgical dissection cutter assembly  10  incorporating a dissection tool  20  in use on a patient  30  at a surgical access site  32 . The patient  30  is illustrated as undergoing a neurological operation. Access to a brain or other neurological structures of the patient  30  often requires delicate dissection of bone (e.g. a skull) and other tissues.  FIG. 1  is provided for example purposes only; the surgical burs disclosed herein may be used in different tools and/or cutter assemblies and may be used for other procedures and/or operations. The dissection cutter assembly  10  includes a dissection tool driver  40 , which is being utilized to dissect a portion of bone and adjacent tissue of the patient  30  in the surgical access site  32 . The tool driver may include the Midas Rex® Legend EHS Stylus High-Speed Surgical Drill, as noted above, or other appropriate driver. 
         [0024]      FIG. 2  is a perspective view of the surgical dissection cutter assembly  10 . The dissection tool driver  40  includes a motor housing  42  connected to a connector  44 , the connector may include a hose or cable assembly. The connector  44  supplies external power and control for a motor included within the motor housing  42 . The dissection tool driver  40  further includes an attachment housing  46  that connects to the dissection tool  20 . A dissection tool distal end includes a surgical bur  64 . A dissection tool proximal end may include a driver connection  54 . The driver connection  54  may engage a connection within the attachment housing  46  to receive rotary power from the motor within the motor housing  42 . 
         [0025]    Although the following described dissection tools, for example surgical burs, are disclosed and illustrated in the drawings as having a particular number of flutes, rake surfaces per flute, rake angles per flute, clearance surfaces per flute, lands, axial relief surfaces, clearance surfaces, etc., the surgical burs may have other quantities of each of these items. 
         [0026]      FIG. 3  shows a side and perspective view of the dissection tool  20 . The dissection tool  20  may be used as part of the dissection assembly  10  of  FIG. 1 . The dissection tool  20  includes a shaft  62  and the surgical bur  64 . The surgical bur  64  has a design that may generally be referred to as a “match head”, “neuro”, or “matchstick” design and includes a body  66 . The body  66  has two convex lands  68  and two flutes  70 . Each of the flutes  70  is located between the lands  68  and has a corresponding chip space  72 . The lands  68  are convex-shaped and/or rounded and may be in respective  180 ° locations about a longitudinal axis  78  of the dissection tool  20 , the shaft  62 , and/or the surgical bur  64 . The surgical bur  64  is rotated about the longitudinal axis  78 . The flutes  70  may also be in respective 180° locations about the longitudinal axis  78 . Each of the flutes  70  has one or more rake surfaces on or at a cutting edge  76 . A clearance surface  73 , which may be a flat or concave surface, may also correspond to the cutting edge  76 . The clearance surfaces  73  are formed relative to the flutes  70 , and may be on both proximal and distal portions of the flutes  70 , near respective bur proximal end  64   a  and bur distal end  64   b.    
         [0027]    With additional reference to  FIGS. 4 and 5 , the surgical bur  64  further includes the cutting edge  76 . The cutting edge  76  is spaced a distance  82  from a center or central axis  78  of the bur  64 . Generally, the cutting edge  76  axially extends from and is spaced the distance  82  from the center axis  78 . Further, the cutting edge  76  is generally set on an edge of the flute  70 . The cutting edge  76  is a leading edge while cutting the bur  64  rotates in the direction of arrow  80  around the central point or axis  78 . The cutting edge  76  offset the distance  82  generally places the cutting edge  76  at a maximum distance from the center point  78  of the bur  64 . That is the cutting edge  76  is generally at a most exterior point or distance from the center  78  as the cutting edge  76  is cutting into a material, as discussed further herein. A rig surface  84  extends from the cutting edge towards a distal tip  86  at the bur distal end  64   b,  through which the central axis  78  may extend. The distal tip  86  may be a terminal distal tip of the dissection tool  20 . 
         [0028]    A trailing edge  90  of the bur  64  can be formed at an edge of the curved land  68  and generally adjacent to the flute  70  of the bur  64 . The trailing edge  90  is generally an edge of the curved land  68  that follows the cutting edge  76  as the bur  64  rotates in the direction of arrow  80 . The trailing edge  90  may be at a distance  94  from the center axis  78 . The distance  82  of the cutting edge  76  from the central axis  78  and the distance  94  of the trailing edge  90  from the central axis  78  may be substantially the same or identical. With continuing reference to  FIG. 4 , the leading edge  76  and the trailing edge  90  may generally lie on a circle  96  having a radius that is substantially equivalent to or defined by the distances  82  and  94  from the center  78 . Thus, the cutting edge  76  may not extend beyond the circle  96  or the trailing edge  90 . Both the cutting edge  76  and the trailing edge  90  may extend only to the circle  96 . Moreover, the cutting edge and the trailing edge may be include more than one of each, as discussed herein. A third distance  95  of a surface forming the convex land  68  may be less than either of the first distance  82  or the second distance  94 . Further, the clearance area  73  of the flutes, as discussed herein, may have a fourth distance  73   a  from the center  78  that is less than the first, second or third distance. 
         [0029]    As further illustrated in  FIG. 4 , two flutes may be included with the surgical bur  64 . A second flute  70   a  may include a second leading or cutting edge  76   a  and a second trailing edge  90   a.  Thus, the bur  64  may include two flutes  70 ,  70   a  with equivalent two cutting edges  76 ,  76   a  and two trailing edges  90 ,  90   a.  The second cutting edge  76   a  and second trailing edge  90   a  may also be formed on the circle  96  centered on the central axis  78  of the bur  64 . 
         [0030]    The bur  64  may include any selected geometry for forming a dissection of a selected structure. For example, the flute may define an arc  97  that is about 5 degrees (°) to about 35°. The curved land  68  may also define an arc  99 , which may also be the arcuate distance from the trailing edge  90 ,  90   a  to a cutting edge  76 ,  76   a  that is about 175° to about 145°. The arcs  97 ,  99 , however, may be formed with the bur  64  to be any selected arcuate angle. The distances  82 ,  94  of the cutting edges  76 ,  76   a  and the trailing edge  90 ,  90   a , however, may all generally be equivalent. 
         [0031]    Turning reference to  FIGS. 6-8 , a surgical bur  164  is illustrated. The surgical bur  164  can be used as the dissection tool  20  in the assembly  10  in the manner similar to the surgical bur  64 , as discussed above. The surgical bur  164  can also include various features and portions similar to the surgical bur  64 , as discussed above. Accordingly, this portion will not be described in substantial detail and have similar reference numerals as those noted above increased by  100 . 
         [0032]    The surgical bur  164  may include a central axis  178  that extends through a shaft  162  of the surgical bur  164 . The surgical bur  164  includes a body  166 . The surgical bur  164  can include a flute  170  with a cutting edge  176 . Further, a trailing edge  190  can be formed on the body  166  and follow the cutting edge  176  as the surgical bur  164  rotates in a direction of arrow  180 . Further, a chip collection area  172  can be defined in the flute  170 . A convex land  168  is formed between the cutting edge  176  and the trailing edge  190 . 
         [0033]    The surgical bur  164  may differ from the surgical bur  64  in that the surgical bur  164  includes three cutting edges  176 ,  176   a  and  176   b.  Accordingly, the surgical bur  164  can also include three flutes  170 ,  170   a  and  170   b.  Further, the surgical bur can include three trailing edges  190 ,  190   a  and  190   b.    
         [0034]    Similar to the surgical bur  64 , the surgical bur  164  can define or have a circle  196  that defines an outer perimeter or edge of the surgical bur  164 . Accordingly, the cutting edge  176  may be formed at a distance  182  from the central axis  178 . The trailing edge  190  can be formed at a distance  194  from the central axis  178 . The distance  182  may be substantially equal or equivalent to the distance  194 . Therefore, the cutting edge  176  and the trailing edge  190  can both be positioned on the circle  196 . Additionally, the surgical bur may include a distal tip  186  that is generally on the axis  178  and other features that are similar to the surgical bur  164 . Also, the convex land  168  may have a surface that is a third distance  195  from the center axis  178  that is less than either of the first distance  182  or the second distance  194 . 
         [0035]    The surgical bur  164 , therefore, includes three flutes  170 ,  170   a ,  170   b  while the surgical bur  64  includes two flutes. On the bur  164 , the arcuate distance of the flutes  170 ,  170   a,    170   b  and the arcuate distance from a trailing edge to the next cutting edge  176 ,  176   a,    176   b  may be selected to be any appropriate distance. The arcuate distances between the various portions may be smaller than on the bur  64  given that there are a greater number of flutes on the bur  164 . 
         [0036]    It is further understood that a surgical bur, according to the various embodiments, can include any appropriate number of flutes. Regardless, the cutting edge and trailing edge may both be generally on a circle that defines an outer extent of the surgical bur. Therefore, the distance from the central axis to the cutting edge and trailing edge may generally be substantially equivalent or identical, as discussed above. Further, it is understood that the surgical bur may be formed in any appropriate shape such as including a ball shape, a cylindrical shape, or other appropriate shape. The surgical bur, according to various embodiments, can therefore be used to form a dissection or resection of an appropriate portion of a subject, such as the patient  30  as illustrated in  FIG. 1  and discussed further herein. 
         [0037]    Turning reference to  FIGS. 9A and 9B , the surgical bur  64  is illustrated relative to a bone structure or mass  210 . The surgical bur  64  includes the cutting edge  76  and the cutting edge  76   a,  as discussed above. The surgical bur  64  can move or bore axially generally along the axis  78  of the dissection tool  20 . Accordingly, as illustrated in  FIGS. 9A and 9B , the surgical bur  64  can move along the axis  78  and generally directly out of the plane of the page. An additional movement of the surgical bur  64  can be to cut radially or generally away from the central axis  78 , such as in the direction of arrow  212 . As the surgical bur is moved in the direction of arrow  212  into the bone mass  210 , a channel or trough  214  may be formed. In forming the channel  214 , the cutting edge  76  can form one or more bone chips  218  from the bone mass  210 . The bone chips  218  can be moved into the flute  70  of the surgical bur  64 . In moving into the flute  70  of the surgical bur  64 , the bone chip  218  can be moved out of the cutting path of the surgical bur  64 , which generally in the direction of arrow  212 . 
         [0038]    The surgical bur  64 , in cutting the bone  210 , is rotating in the direction of arrow  80 , as discussed above. Further, the bur  64  is moved in the direction of arrow  212  to form the channel  214  in the bone  210 . Therefore, the cutting edge  76 , moving in the direction of arrow  80 , cuts the bone chip  218  and then continues to rotate in the direction of arrow  80  and generally away from a front wall or cutting area  220  of the channel  214 . The cutting edge  76  in forming the bone chip  218 , therefore, moves the bone chip  218  towards the already formed portion of the channel  214 . 
         [0039]    As illustrated in  FIG. 9B , the cutting edge  76 , after forming the bone chip  218 , is passing into or through the formed portion of the channel  214  and the trailing edge  90  trailing as the cutting edge  76  is engaging the front or forming wall  220  of the channel  214 . As discussed above, the trailing edge  90  can include the distance  94  from the central axis  78  that is substantially equivalent or equal to the distance  82  of the cutting edge  76  from the central axis  78 . Therefore, the trailing edge  90  can engage the wall  220  at substantially the same distance from the central axis  78  as the cutting edge  76  and the forthcoming second cutting edge  76   a.  This an guide and or stabilize the bur  64 , as discussed further herein, during cutting with the cutting edge  76   a.    
         [0040]    The cutting edge  76   a  includes a distance  82   a  which is substantially identical to the distance  82  from the central axis  78 . Therefore, the cutting edge  76   a,  prior to cutting the wall  220 , is generally at substantially the same position as the trailing edge  90 . Because the radius or distance from the central axis  78  to the wall  220  is substantially identical for the trailing edge  90  and the second cutting edge  76   a,  there is no jump or jerking of the bur  64  prior to the second cutting edge  76   a  initiating a cut and formation of the bone chip  218 . Therefore, the trailing edge  90  can form or act as a stabilizing edge or surface relative to the wall  220  of the channel  214  prior to the second cutting edge  76   a  cutting the wall  220 . Similarly, the second trailing edge  90   a  can act as a stabilizing surface or edge relative to the cutting edge  76  prior to the cutting edge  76  cutting the forward wall  220  of the channel  214 . 
         [0041]    The bur  64  can rotate by the motor generally at a selected rotational rate, such as about 700 to about 75,000 rpm. As an example, the bur  64  may rotate at about 7,000 rpm. Therefore, the engaging of the cutting edges  76  and  76   a  on the forward wall  220  and the stabilizing by the trailing edges services  90 ,  90   a,  can substantially stabilize the bur  64  as the bur  64  forms the channel  214 . 
         [0042]    Returning reference to  FIG. 9A , the bur  64  is stabilized during radial cutting, for example when the cutting edge  76  forms the bone chip  218  to cut or dissect the bone  210 . The bur  64  may experience reduced vibrational and forces and chatter during radial cutting. In one example, the bur  64  can experience a reduction of vibration by at least about 40%, including a reduction of about 20-40%, including about 42%. Vibration forces may be measured with an accelerator and reported in g-forces using units such as meters/second 2 . 
         [0043]    During operation, the stabilization may occur by the bur  64  rotating within the channel, the cutting edge  76  moves away from the front wall  220  of the channel  214 . As the cutting edge  76  moves away from the front wall  220 , the trailing edge  90  can engage the wall  220  prior to the next cutting edge  76   a.  Due to the rotational speed of the bur  64 , the elapsed time between the cutting edge leaving the wall  220  and the trailing edge  90  engaging the wall may be very short, such as on the order of micro-seconds. 
         [0044]    The trailing edge  90 , however, engages the wall  220  prior to the second cutting edge  76   a  beginning the cut of the front wall and formation of the bone chip  218 . Therefore, as the cutting edge  76   a  begins to cut the front wall  220  of the channel  214 , the bur  64  may be substantially stabilized relative to the front wall  220 . This is at least because the trailing edge  90  is the same or substantially the same distance from the center  78  as the cutting edge  76   a.    
         [0045]    Further, the trailing edge  90  can continue to ride along the wall  220  to stabilize the bur  64  as the bur  64  rotates in the direction of arrow  80  and the cutting edge  76   a  cuts and forms bone chips along the wall  220 . Therefore, the trailing edge may act as a guide that stabilizes the bur  64 . The trailing edge  90  stabilizes the bur  64  as following cutting edge, for example the cutting edge  76   a , follows the trailing edge  90  as illustrated in  FIG. 9B . This assists in stability of the bur  64  during cutting the channel  214 . 
         [0046]    The contact of the trailing edge  90  with the front wall substantially simultaneously with the cutting edge  76   a  or immediately prior to may reduce chatter or vibration of the bur  64  while cutting or dissecting. This can reduce user fatigue during use of the assembly  10  including the bur  64 . This can also increase precision of the dissection when using the bur  64  due to reduced vibration and chatter. Thus, a user may be able to cut longer without a break to decrease time needed for a procedure and to increase precision of a cut. Accordingly, the bur  64  may also decrease a chance of a mic-cut. It is further understood, as discussed above, that the trailing edge and cutting edge may be any appropriate combination of edges and need not specifically be the ones referred to by reference number above. 
         [0047]    In cutting the channel  214 , various surgical procedures may occur. For example, a bur hole may be formed in a scalp, as illustrated in  FIG. 1 . The bur hole may be used to allow access to the brain dura and brain tissue for various procedures, such as placement of a deep-brain simulation probe, a resection of a tumor, and the like. Further, other procedures may include forming a hole in other cranial tissues, forming a depression or removal of tissue and other bone matter, including long bones and vertebrae, and other appropriate procedures. Regardless of the specific procedure, however, the bur  64  may cut the channel  214  and the bone  210  without substantial vibration due to the positioning of the trailing edge  90  at substantially the same radial position relative to the central axis  78  as the cutting edge  76   a.    
         [0048]    Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. Moreover, the design and structure of a surgical bur may be altered from the specific examples provide above, but include a trailing edge that has a distance from a center equal to or substantially equal to a following, such as an immediately following cutting edge. This may allow a substantially smooth and jitter or jump free dissection of tissue, including boney tissue. 
         [0049]    The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. 
         [0050]    The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.