Patent Publication Number: US-9414845-B2

Title: Micro-saw blade for bone-cutting surgical saws

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 12/136,956 filed on Jun. 11, 2008. The entire disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to a bone-cutting surgical system, and more particularly, to a micro-saw blade suitable for use with a surgical cutting saw. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Bone-cutting surgical saws, such as sagittal or oscillating type surgical saws, cut most effectively at very high speeds, such as for example, 10000-40000 cycles per minute. These high speeds introduce high levels of vibration and can cause blade wander during a cut. Accordingly, blade cuts typically have a thickness considerably greater than the width of the actual blade. For example, a cutting blade having a 0.015 inch thickness may be unable to cut a groove having a width of less than 0.030 inch. In addition, because the saws operate at such high speeds, the excessive vibration can quickly fatigue a surgeon&#39;s hand or wrist. As fatigue sets in, maintaining the same preciseness and accuracy may become more difficult. 
     A contributing problem is the way the blade attaches to the saw. Conventional systems use pins located close to the centerline of the blade attachment portion, resulting in a short moment arm for driving the blade. Accordingly, during irregular cutting, such as a while making a curved cut or a cut not along the path of the normal oscillating path of the saw blade, the blade can become dislodged, possibly causing some blade loosening. This can result in cuts having a width considerably larger than the blade width. 
     The devices disclosed herein overcome one or more of short-comings in the prior art. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     In one exemplary aspect, the present disclosure is directed to a surgical cutting blade for cutting bone material when the blade is coupled to a hand-held surgical saw having protrusions extending therefrom that interface with the cutting blade. The cutting blade includes a distal end comprising a plurality of cutting teeth and a shank portion adjacent the distal end. It also includes a proximal end adjacent the shank portion. The proximal end is shaped to attach to the surgical saw and includes an upper substantially planar surface and a lower substantially planar surface and a side edge extending between the upper and lower planar surfaces. The side edge at least in part defines an outer perimeter extending about the proximal end. The outer perimeter includes a plurality of indentations forming openings configured to receive and interface with the protrusions of the surgical saw in a manner that the protrusions cooperatively impart motion to drive the blade. 
     In another exemplary aspect, the present disclosure is directed to a surgical cutting blade for cutting bone material when the blade is coupled to a hand-held surgical saw having protrusions extending therefrom that interface with the cutting blade. The cutting blade includes a distal end comprising a plurality of cutting teeth and a shank portion adjacent the distal end. The blade also includes a proximal end adjacent the shank portion. The proximal end is shaped to attach to the surgical saw and includes an upper substantially planar surface and a lower substantially planar surface. The proximal end also includes a perimeter edge and a centrally disposed slot formed therein. The slot defining an inner edge. The proximal end also includes a plurality of openings configured to receive and interface with the protrusions of the surgical saw in a manner that the protrusions cooperatively impart motion to drive the blade. The openings are disposed closer to the perimeter edge than the inner edge. 
     In another exemplary aspect, the present disclosure is directed to a cutting blade set for cutting bone material when the blade is coupled to a hand-held surgical saw having protrusions extending therefrom that selectively interface with each blade of the cutting blade set. The cutting blade set includes a plurality of cutting blades. Each blade of the plurality of cutting blades includes a distal end comprising a plurality of cutting teeth, the distal end of each cutting blade of the plurality of cutting blades having a different thickness, and includes a shank portion adjacent the distal end. Each blade also includes a proximal end adjacent the shank portion. The proximal end is sized and shaped to interface with the surgical saw. The proximal end of each cutting blade of the plurality of cutting blades has substantially the same thickness. 
     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 
       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. 
         FIG. 1  is an illustration of an exemplary oscillating bone-cutting surgical system. 
         FIG. 2  is an illustration of an exemplary collet assembly from the surgical system of  FIG. 1 . 
         FIG. 3  is an illustration of a cross-section of the exemplary collet assembly of  FIG. 2 . 
         FIG. 4  is an illustration of an exemplary driving shaft of the collet assembly of  FIG. 2 . 
         FIG. 5  is an illustration of an exemplary sleeve of the collet assembly of  FIG. 2 . 
         FIGS. 6 and 7  are illustrations of an exemplary micro-saw blade of the bone cutting surgical system of  FIG. 1 . 
         FIG. 8  is an illustration of the driving shaft of  FIG. 3  with a micro-saw blade. 
         FIG. 9  is an illustration of the sleeve of  FIG. 4  with an in-place micro-saw blade. 
         FIGS. 10-12  are illustrations of additional exemplary micro-saw blades usable with the bone-cutting surgical system. 
         FIG. 13  is an illustration of an exemplary blade set having a plurality of micro-saw blades. 
         FIGS. 14 and 15  are illustrations of components of an alternative collet assembly. 
         FIG. 16  is an illustration of an exemplary sagittal bone-cutting surgical system. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     Generally, the present disclosure relates to a bone cutting surgical system including a hand-held, high-speed, bone-cutting surgical saw, such as a sagittal or oscillating saw, and a cutting micro-saw blade. The saw includes a collet assembly with protruding pins or nubs that mesh with or extend into openings on the cutting blade, thereby securing the blade in place in the collet assembly. In order to minimize the moment forces on the interior of the blade when the blade is rotating, the protrusions on the collet assembly and the openings on the saw blade are placed toward the exterior perimeter of the collet assembly and the exterior perimeter of the saw blade. In one embodiment, the openings are notches formed along the exterior edge of the saw blade. By moving moment forces toward the exterior of the saw blade, blade vibration may be reduced. Reducing vibration increases cutting accuracy, which can reduce patient trauma and speed recovery time, as well as reduce surgeon fatigue. In some embodiments, the micro-saw blades include a dampening overmold that interfaces with the collet assembly. This too may reduce blade vibration. In addition, the overmold may assist with blade identification. 
     Turning now to  FIG. 1 , the present disclosure is directed to a bone-cutting surgical system  100  including a surgical saw  102  and a selectively removable micro-saw blade  104 . The surgical saw  102  includes a hand-piece  106 , a cord  108 , and a connector  110  configured to removably couple with a power source. The connector  110  is merely exemplary, and it should be apparent to one skilled in the art that any suitable connector may be used, and in some embodiments, the cord  108  itself may be coupled to the power source without the use of a connector. Additional contemplated embodiments include a power source as a part of the hand-piece  106 , such as a battery powered hand-piece. 
     The hand-piece  106  includes a motor assembly  112 , a grip  114 , and a collet assembly  116 . In some embodiments, the motor assembly  112  is housed within the grip  114 , while in other embodiments, it is disposed adjacent to the grip  114 . It is contemplated that any suitable system for controlling the surgical saw  102  may be used. For example, some embodiments include a trigger system disposed on the hand-piece  106  to provide hand-control of the cutting speed, or alternatively, a foot pedal associated with the hand-piece  106  through the power source to provide the controlling inputs. Other control systems also are contemplated. 
       FIGS. 2-5  show a portion of the exemplary collet assembly  116 . The collet assembly  116  secures the saw blade  104  to the surgical saw  104  and transfers a driving force from the motor to the blade. In this embodiment, it includes a driving shaft  118  and a sleeve  120  defining a longitudinal collet axis  122 . The sleeve  120  receives and extends about the driving shaft  118  and is axially movable along the collet axis  122  relative to the driving shaft  118 , enabling selective coupling with the blade  104 . 
     The driving shaft  118  is shown in greater detail in  FIGS. 3 and 4 . Here, the driving shaft includes a head  124  forming a distal end of the driving shaft and a shank  126  extending proximally from the head  124 . These together define a shaft axis  127  ( FIG. 4 ) extending longitudinally through the shaft. 
     Referring to  FIGS. 3 and 4 , the head  124  includes a distally facing outer surface  128 , a proximally facing blade contacting surface  130  adjacent the shank  126 , and an outer perimeter  132  extending therebetween. The blade contacting surface  130  includes an inner edge  134 , which in this embodiment is defined where the shank  126  and the blade contacting surface  130  meet. It also includes an outer edge  136 , which in this embodiment is defined where the outer perimeter  132  and the blade contacting surface  130  meet. These inner and outer edges  134 ,  136  define a reference mid-line  138  half-way between them on the blade contacting surface  130 . 
     In this embodiment, the blade contacting surface  130  includes a receiving opening formed therein as a receiving recess  140  for receiving one or more protrusions to be discussed below relative to the sleeve  120 . Here, the receiving recess  140  is formed as a single groove concentric about the shaft axis  127  and disposed closer to the outer perimeter  132  than to the shank  126 . Accordingly, as shown in  FIG. 4 , the receiving recess  140  is offset from the mid-line  138  defined by the inner and outer edges  134 ,  136  of the blade contacting surface  130 . In the example shown, the outermost edge of the receiving recess  140  (edge closest to the outer perimeter  132 ) is located toward the outer edge  136  at least half of the distance between the mid-line  138  and the outer edge  136 . Said another way, the outermost edge of the receiving recess  140  is located toward the outer edge  136  at least three quarters or 75% of the distance from the inner edge  134  to the outer edge  136 . In some embodiments, the outermost edge of the receiving recess is closer to 80% of the distance between the inner edge  134  and the outer edge  136 . In the embodiment shown, the inner most edge of the receiving recess  140  (edge closest to the shank  126 ) is likewise located more than half the distance toward the outermost edge  136  so that the entire receiving recess  140  is disposed outwardly from the midline  138 , or more than half of the distance of the inner edge  134  to the outer edge  136 . 
     Furthermore, in the example of  FIG. 4 , the outermost edge of the receiving recess  140  is disposed toward the outer edge  136  more than 80% of the distance from the shaft axis  127  to the outer edge  136 , and in some embodiments, more than 90% of the distance from the shaft axis  127  to the outer edge  136 . 
     The shank  126  includes a distal end  142  either connected to or integral with the head  124  and a proximal end  144 . At the distal end  142 , the shank includes a blade receiving radial groove or recess  146  ( FIG. 3 ). The groove  146  is formed such that the blade contacting surface  130  of the head  124  forms one side of the groove  146  while the opposing side is formed by a shoulder portion  148  ( FIG. 3 ) of the shank  126 . In the embodiment shown, the groove  146  is formed with a circular diameter sized to mate with and receive a portion of the saw blade  104 . However, in other embodiments, the groove  146  is non-circular, and may be formed, for example, of a series of flat surfaces or may be formed of, for example, two grooves formed into opposing sides of the shank  126 . An axially elongated slot  150  extends through the shank  126 . This can receive a pin (not shown) connecting the shank  126  to the sleeve  120  while still permitting limited axial sliding between the sleeve  120  and shank  126 . In this embodiment, the proximal end  144  includes a motor coupling feature  147  shown as a pin-receiving through passage that connects either directly or cooperatively to the motor to provide the cutting oscillation required. 
       FIGS. 3 and 5  show the sleeve  120  in greater detail. The sleeve  120 , like the driving shaft  118 , includes a head  152  and a shank  154 , but is formed with a central bore  156  sized to receive the shank  126  of the driving shaft  118  as shown best in  FIG. 3 . The sleeve  120  defines a sleeve axis  158  shown in  FIG. 5 . The head  152  includes a substantially planar distally facing blade contacting surface  160 , a proximally facing surface  162 , and an outer perimeter  164 . In this embodiment, the sleeve outer perimeter  164  is sized to have substantially the same diameter as the driving shaft outer perimeter  132 . Further, as shown in  FIG. 3 , the distally facing blade contacting surface  160  of the sleeve  120  faces the proximally facing blade contacting surface  130  of the driving shaft  118 . 
     The distally facing blade contacting surface  160  includes an inner edge  166 , which in this embodiment is defined where the central bore  156  and the distally facing blade contacting surface  160  meet. It also includes an outer edge  168 , which in this embodiment is defined where the outer perimeter  164  and the distally facing blade contacting surface  160  meet. These inner and outer edges  166 ,  168  define a reference midline  170  extending half-way between them on the distally facing blade contacting surface  160 . 
     Referring now to  FIG. 5 , the distally facing blade contacting surface  160  of the sleeve  120  includes a plurality of protrusions  172  formed thereon. These are symmetrically disposed about the sleeve axis  158  and are configured to interface with the saw blade  104 , as is further discussed below. Here, the sleeve  120  includes eight protrusions extending therefrom, spaced apart about the sleeve axis  158 . It is contemplated that more or fewer protrusions may be present. The protrusions  172  may be integrally formed with sleeve  120  or, for manufacturing convenience, may be separate components fit, such as with an interference fit, into receiving ports  171  (shown in  FIG. 3 ) formed in the distally facing blade contacting surface  160 . For clarity, the protrusions  172  are not shown in  FIG. 3 , but are shown in  FIG. 5 . In this embodiment, these protrusions  172  are formed of cylindrical pins extending from the substantially planar distally facing blade contacting surface  160 . In other examples however, the protrusions  172  have a square, rectangular, triangular or diamond-shaped cross-section. Protrusions of other shapes are also contemplated. 
     The protrusions  172  are disposed offset from the mid-line  170  on the distally facing blade contacting surface  160 . In the example shown, the protrusions  172  are disposed so that the outermost portion of the protrusions (portion of protrusion closest to the perimeter  164 ) is located toward the outer edge  1688  at least half of the distance between the midline  138  and the outer edge  168 . Said another way, the outermost portions of the protrusions  172  are located toward the outer edge  168  at least three quarters or 75% of the distance from the inner edge  166  to the outer edge  168 . In some embodiments, the outermost portions of the protrusions  172  are closer to 80% of the distance between the mid-line  170  and the outer edge  168 . 
     In the embodiment shown, the inner most portions of the protrusions  172  (portions closest to the inner edge  166 ) are likewise located toward the outermost edge  136  so that the entire protrusion  172  is disposed outwardly from the midline  170 , or more than half of the distance of the inner edge  166  to the outer edge  168 . 
     Furthermore, in the example of  FIG. 5 , the outermost portions of the protrusions are disposed toward the outer edge  168  more than 80% of the distance from the sleeve axis  158  to the outer edge  168 , and in some embodiments, more than 90% of the distance from the sleeve axis to the outer edge  168 . 
     The sleeve shank  154  extends from the proximally facing surface  162  ( FIG. 3 ) of the head  152  and includes a transverse through hole  174  in each side sized to receive a pin (not shown) connecting the sleeve  120  and driving shaft  118 . When assembled with the driving shaft  118 , the hole  174  aligns with the slot  150  in the driving shaft  118  for slidable, pinned attachment. 
     Referring now to  FIG. 3 , as can be seen, the distally facing blade contacting surface  160  of the sleeve  120  and the blade contacting surface  130  of the driving shaft  118  face each other. The pieces may axially move apart to receive the blade  104 , and then come together to clamp the blade  104  between the blade contacting surfaces. When assembled, the shaft axis  127  ( FIG. 4 ) of the driving shaft  118  and the sleeve axis  158  ( FIG. 5 ) of the sleeve are co-axially aligned with the longitudinal collet axis  122  ( FIG. 3 ). These form a centerline about which the saw blade  104  can oscillate. The protrusions  172  (not shown for clarity in  FIG. 3 ) extending from the distally facing blade contacting surface  160  fit within the receiving recess  140  formed in the head of the driving shaft  118  to both secure and align the saw blade  104 , as discussed below. 
     Here, the receiving recess  140  is shown as a single groove formed radially about the shaft axis  127 , and extending into the proximally facing blade contacting surface  130 . In some embodiments, the collet assembly  116  includes no receiving recess, but the protrusions extend to and abut directly against the substantially planar proximally facing blade contacting surface  130 . 
       FIGS. 6 and 7  show the exemplary micro-saw blade  104  usable with the surgical saw  102  in  FIG. 1  and securable with the collet assembly  116  in  FIGS. 2-5 . The micro-saw blade  104  includes a proximal end  180  that that facilitates interconnection with the collet assembly  116  and a distal end  182  having a cutting edge including a plurality of cutting teeth  184  formed thereon. 
     In this example, the proximal end  180  is defined by a relatively bulbous head  186  that includes a slot  188  extending inwardly along a longitudinal axis  190  form the proximal end of the saw blade  104 . The slot  188  is formed with a funnel-like opening  192  defined by substantially straight edges  194  facing toward the longitudinal axis  190 . The straight edges may help guide the saw blade  104  into place on the collet assembly, and form an angle between 70 and 160 degrees, but more particularly, within a range of about 90 to 120 degrees. The slot  188  also includes a slot edge  196  shaped to interface with the blade receiving groove  146  on the driving shaft  118  ( FIG. 3 ). Because the blade receiving groove  146  is cylindrically shaped, the slot edge  196  is formed as a semi-circle, about a center point  198  defined by the bulbous head  186 , with substantially parallel sides extending proximally from the slot edge toward the funnel-like opening  192 . The slot edge  196  at least in part defines an inner edge of the bulbous head  186 . A partially circular outer perimeter  200 , which in this embodiment is concentric with the slot edge  196 , defines an outer edge of the bulbous head  188 . In some embodiments, the outer perimeter  200  has a diameter substantially the same as, or slightly smaller than, the diameter of the driving shaft head  124  and the sleeve head  152 . For reference, a concentric midline  202  splits the distance between the outer perimeter  200  and the slot edge  196  in  FIG. 7 . 
     Openings  204  formed in the outer perimeter  200  and extending through the blade  104  permit the saw blade  104  to be secured to the surgical saw collet assembly  116 . In the embodiment shown, the openings  204  are symmetrically disposed about the center point  198 . Here, at least two openings  204  lie directly on opposing sides of the center point and on transverse sides of the longitudinal axis  190 . A centrally disposed opening  206  lies along the longitudinal axis  190 . The central opening  206  is spaced the same distance from the center point  198  as the perimeter openings  204 . In the example shown the openings  204 ,  206  are offset from each other by 45 degrees and are sized to match the protrusions  172  on the distally facing surface of the sleeve  120 . However, other offset angles are contemplated that match the desired collet assembly. 
     The openings  204 ,  206  are disposed offset from the mid-line  202  defined by the outer perimeter  200  and the slot edge  196  of the bulbous head  186 . In the example shown, the openings  204 ,  206  are formed so that innermost edge portions (edge portions closest to the centerpoint  198 ) are disposed closer to the outer perimeter  200  than to the slot edge  196 . Accordingly, the innermost edge of the opening is spaced from the slot edge  196  more than half of the distance between the outer perimeter  200  and the slot edge  196 . In some embodiments, the innermost edge portions of the openings  204 ,  206  are spaced toward the perimeter edge to be more than about 70% of the distance between the outer perimeter  200  and the slot edge. 
     Furthermore, as measured from the centerpoint  198 , the innermost edge portions of the openings may be located toward the outer perimeter  200  more than 80% of the distance between the perimeter  200  and the centerpoint  198 , and in other embodiments, more than 90% of the distance between the perimeter  200  and the centerpoint  198 . 
     Each opening  204 ,  206  is shaped to be slot-like, having a semi-circular inner end  208  and substantially parallel sides  210 , albeit for a relatively short distance, extending from the semi-circular end  208  toward the outer perimeter  200 . Chamfered or rounded edges  212  smooth the transition from the opening  204  to the outer perimeter  200 . This reduces the chance of snagging or perforating surgical gloves on the proximal end  180  of the saw blade  104 . This is particularly useful because the outer perimeter  200  may be closely aligned with, or slightly smaller than the outer perimeters of the heads of the driving shaft and sleeve. It is noted that the transition from the outer perimeter  200  to the straight edges  194  of the slot opening  192  are also chamfered or rounded. 
     In the example shown, the bulbous head  186  includes five openings  204 ,  206 . However, in other embodiments, more or less openings may be provided. When the funnel-like opening  192  has an angle smaller than that shown, additional openings may be included, while maintaining the 45 degree spacing shown. 
     The saw blade  104  includes a shank  214  interposed between the proximal end  180  and the distal end  182 . The distal end  182  of the saw blade  104  includes the plurality of teeth  184  formed at angles of 60 degrees, however, other angles, both larger and smaller are contemplated. The cutting teeth angle may be at least partially dependent on the surgical application. In the embodiment shown, tips of the teeth are formed so that together, the teeth define a circular path, indicated by the reference line  216 . 
       FIGS. 8 and 9  respectively show the blade  104  with reference to the driving shaft  118  and the sleeve  104 , respectively. Although the blade  104  is shown separately with respect to each of the shaft and sleeve, when the driving shaft  118  and the sleeve  104  are joined together to form the collet assembly  116 , it is contemplated that a single blade will be used at a time, although other arrangements are possible. First, with reference to  FIG. 8 , the bulbous head  186  of the blade  104  fits partially within the blade receiving groove  146 . In order to provide a secure fit, the slot  188  ( FIG. 7 ) is formed with a diameter that easily receives the inner portion of the receiving groove  146 , but also has a clearance close enough to provide some stabilizing support to the blade  104 . The bulbous head  186  of the saw blade  104  is substantially the same size or slightly smaller than as the outer perimeter of the head of the driving shaft. It should be noted that when the blade  104  is properly received in the receiving groove  146 , the center point  198  of the blade  104  is aligned with the shaft axis  127 , such that the outer perimeter  200  of the blade  104  and the outer perimeter  132  of the shaft head  124  are concentric. During assembly, the blade  104  is first introduced into the receiving groove  146  adjacent the blade contacting surface  130  of the shaft head  124  so that the bulbous head  186  lies flush with the blade contacting surface  130 , as indicated by the arrow. The sleeve  120  is then axially slid along the shaft  118  so that the protrusions  172  (not shown in  FIG. 8 ) engage the openings  104 ,  106  in the blade  104 . 
       FIG. 9  shows the protrusions  172  of the sleeve  120  interfacing with the openings  204 ,  206  on the bulbous head  186  of the micro-saw blade  104 , without the driving shaft  118 . In some embodiments, when assembled with the driving shaft  118 , the protrusions  172  extend through the openings  204 ,  206  and extend at least partially into the receiving recess  140  on the driving shaft  116  ( FIG. 3 ). In other embodiments, the protrusions  172  have a length substantially the same as the thickness of the bulbous blade head  186  such that the protrusions just abut against or lie substantially flush with the proximally facing blade contacting surface  130  of the driving shaft  118  ( FIG. 4 ). 
     In the example shown, the saw blade  104  has only five openings and receives five protrusions  172 . In other embodiments, the saw blade  104  has more or fewer openings that receive the protrusions. In one example, the blade  104  includes seven openings and receives seven protrusions. Because the protrusions are spaced 45 degrees apart, the blade  104  can be removed and secured onto the sleeve in eight different positions. In some embodiments, for example, the sleeve includes only four protrusions or six protrusions, and the openings on the blade  104  are chosen to correspond with the protrusions. 
     It should be noted that when the blade  104  is properly disposed on the sleeve  120 , the center point  198  of the blade  104  aligns with the sleeve axis  158 , such that the outer perimeter  200  of the blade  104  and the outer perimeter  164  of the head of the sleeve  120  are concentric. 
     Because the sleeve protrusions  172  are disposed closer to the outer edge  168  than the inner edge  166 , and likewise, because the blade openings  204  are disposed closer to the perimeter  200  than the slot edge  196 , the protrusions  172  provide a longer moment arm than conventional systems, thereby providing higher torque with the same forces. This in turn increases the torque at the distal end  182  of the saw blade  104 , permitting an equivalent torque while reducing the motor force, or alternatively, using the same motor force to provide increased cutting force. In addition, by increasing the distance of the moment arm from the blade centerpoint to the protrusions, there is less moment placed on the interior portions of the blade when it is oscillating. This may reduce vibration that might otherwise occur, in turn potentially reducing the amount of play and increasing accuracy achievable with the cutting blade  104 . By providing openings  204 ,  206  on the blade  104  relatively far from the centerpoint of the shaft, the moment force at the distal end  182  of the blade  104  may be maximized. 
       FIG. 10  shows an alternative embodiment of a micro-saw blade, referenced by the reference numeral  300 . Many of the features of the micro-saw blade  300  are similar to those of the micro-saw blade  104  discussed previously. Accordingly, only the differences are addressed in detail here. Here, the saw blade  300  is formed of a first material such as a single stamped material that provides the distal cutting end  302 , and also formed of a second material different than the first material that forms at least a part of the proximal end  304 . In this example, in addition to forming the distal end  302 , the first material forms a part of a bulbous head section  306 . The second material is overmolded about the first material to also form a part of the bulbous head section  306 . In some examples the second material at the bulbous head section  306  is formed of a material more compliant than the blade material. In some examples, the overmold is a polymer material molded over a cutting blade portion formed of a surgical steel. Some examples of materials for the overmold include, for example, biocompatible low density polyethylene or polypropylene. Other examples are formed of elastomers, including blends to achieve a desired strength or durability. However, any biocompatible material may be used. 
     As shown in  FIG. 10 , the overmold material is formed to have substantially the same profile as the cutting blade so that the protrusions on the collet assembly will securely attach the cutting blade  300  in the same manner as the cutting blade  104 . Furthermore, during use, the overmold material provides some dampening and cushioning to the saw blade  300 . This dampening may reduce vibration experienced by the surgeon, providing some relief to hand and arm fatigue, and also decreasing blade wobble, increasing accuracy of the cut. The overmold also provides additional protection to the surgeons fingers and surgical gloves, as the overmold may provide additional protection from sharp or rigid edges that may be located about the proximal end  304  of the saw blade  300 . 
     In the embodiment shown, the saw blade  300  may be secured to the sleeve  120  discussed above by five protrusions  172  out of eight since the most proximal portion of the bulbous head  306  forms the tapering opening. However, in an alternative embodiment, shown in  FIG. 11 , a saw blade referenced herein as  350  includes an overmold  352  forming a part of the bulbous head  354  that extends further around a slot opening  356 , thereby at least partially enclosing an inner end  358  of the slot  360  in the saw blade  350 . The slot  360  in the center of bulbous head  354  still receives the shank of the driving shaft  118 . As shown in  FIG. 11 , while a blade portion  362  of the saw blade  350  appears to have a size substantially as discussed above, the overmold  352  itself extends about further, partially enclosing the slot  360 . This overmold  352  deforms when the saw blade  350  is attached or detached from the collet assembly  116  to permit the shank  126  of the driving shaft  118  to enter the slot  360 . In another embodiment, the overmold  352  completely encloses the slot  360  to hold the blade  350  in place by extending a full 360 degrees around the shank  126  of the driving shaft  118 . 
     The overmolded portion in  FIG. 11 , like the overmolded portion in  FIG. 10 , contains openings  362  that match the raised protrusions in the collet assembly. With this over molded plastic arrangement, the blade  350  receives seven or in some embodiments, eight of the protrusions  172 . The collet assembly holds the blade  350  in place, yet the pliable and deformable overmold permits easy blade removable. Further, the increased contact provided by the additional material helps further frictionally secure the blade in place and may provide surgeons with more control for precise cuts. 
       FIG. 12  shows an additional embodiment of an exemplary saw blade, referenced herein by the numeral  370 . Here, the saw blade  370 , like the saw blade  300  discussed above, includes a distal cutting end  372 , a proximal end  374 , and a bulbous head section  376 . For reference,  FIG. 12  identifies a shank  378  and an outer perimeter  380  of the bulbous head  376 . The second material is overmolded about the first material to also form a part of the bulbous head  376 . Here, the second material is formed on the blade  370  to cover primarily just the bulbous head section  376 . Because of this, the second material does not extend down the shank  378  toward the distal end  372 , but has a radius  382  that substantially matches the radius  384  of the outer perimeter  380  of the bulbous head  376 . Accordingly, when placed in the collet assembly  116 , the second material is substantially contained between the two blade contacting surfaces, with only the shank extending outwardly from the collet assembly  116 . 
     The overmold in  FIGS. 10-12  may be formed of a material softer than the sleeve  120  and driving shaft  118  materials. Accordingly, the overmold may reduce friction wear on the sleeve  120  and driving shaft  118  by yielding before the harder materials wear. Because the sleeve  120  and driving shaft  118  of the collet assembly  116  may be more expensive to manufacture than the saw blades, preserving the collet assembly may be beneficial to customers and may prolong the useful life of the associated surgical saw. 
     In one embodiment, the overmold is colored to provide information to a surgeon regarding, for example, a blade size, tooth type, or blade thickness. For example, a saw blade having a thickness of 0.010 inch includes a blue overmold and a blade having a thickness of 0.15 includes a red overmold. Accordingly, in some instances, a surgeon may select a desired blade from a blade set of a plurality of blades, with each blade having a colored overmold corresponding to a specific thickness, size, or tooth type. 
       FIG. 13  shows a side view of an exemplary blade set  400  usable with the collet assembly  116  disclosed herein. Each blade of the blade set  400  includes a proximal end  402  formed of a bulbous head, a shank  404 , and distal cutting end  406 . In this embodiment, however, the proximal end  402  of each blade of the blade set  400  has the same thickness, but the thicknesses of the shanks  404  and cutting edges  406  varies. Because the proximal end  402  has the same thickness, the head of each of the blades of the set fits within the receiving groove  146  on the shank  126  of the driving shaft  118  with the same amount of clearance or play for consistency and repeatability. Yet the blade shank  404  and distal cutting edge  406  vary so that a surgeon may select a blade with the desired thickness for the particular surgical application. For example, some blade sets may include blades that vary in thickness between 0.007 and 0.027 inch. The thickness of the proximal end  402  may be a result of an overmold as described above with respect to  FIGS. 10 and 11 , or alternatively, may be laminated or integrally formed of a single monolithic material. In this blade set  400 , colored overmolding may identify the thickness of each cutting blade to permit a surgeon to distinguish one blade from another. 
       FIGS. 13 and 14  show components of an alternative collet assembly, with  FIG. 14  showing an alternative sleeve  500  disposed about a shank  502  of a driving shaft, and with  FIG. 15  showing a driving shaft head  550  separate from the shank  502 . Protrusions  504  on the sleeve  500  and head  550  are spaced toward the respective perimeter edges  506 ,  552 , in the manner discussed above. Accordingly, the description above regarding protrusion placement and placement of the receiving groove is equally applicable to the embodiment in  FIGS. 13 and 14 . 
     The sleeve in  FIG. 14  includes a distally facing blade contacting surface  508  having both protrusions  504  and recessed receiving openings  510  spaced toward the perimeter edge  506  in the manner discussed above. In this embodiment, the protrusions  504  are rectangular or square rather than the cylindrical pins discussed above. It is contemplated that the driving shaft head  550  and the sleeve  500  would be used to secure a saw blade having corresponding shaped openings. In some embodiments, the protrusions or receiving openings are on the driving shaft, while in other embodiments, the sleeve includes some protrusions and the driving shaft includes other protrusions. 
     In  FIG. 15 , the head  550  is removable from the shank of the driving shaft, but may be attached using a fastener, such as a screw. The head  550  includes a proximally facing blade contacting surface  554  that includes protrusions  504  for engaging corresponding openings in a matching saw blade. In this embodiment, as described above, the protrusions  504  are spaced toward the outer perimeter edge. 
       FIG. 16  shows a sagittal saw  600  for driving the saw blade  104 . In this embodiment, the collet assembly  602  is arranged to secure the blade  104  in an axial direction relative to a saw handle  604 . Accordingly, instead of having proximally and distally facing blade contacting surfaces, the collet assembly includes side-by-side blade contacting surfaces. However, like the oscillating saw  102  disclosed in  FIGS. 1-6 , the sagittal saw  600  includes protrusions disposed adjacent an exterior edge of the collet fixture, and the blade  104  is sized so that the outer perimeter of the head of the saw blade substantially corresponds to the edge of the collet assembly. 
     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.