Abstract:
An apparatus, system, and method are disclosed for positional fixation of a fastener, including but not limited to the extraction of an orthopedic screw. According to one embodiment, an instrument is provided which accepts a collet designed to conform to a proximal end of a variety of types and sizes of fasteners. The collet is installed through a chuck body, which is seated in a distal end of a handle. A closing mechanism within the handle causes the collet to tightly grip and lock onto the proximal end of the fastener. A compressible distal end of the collet may have longitudinal slits that define jaws for improving gripping flexibility.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/053,581, filed May 15, 2008, which is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    This invention relates to positional fixation and more particularly relates to orthopedic fixation devices. 
       BACKGROUND 
       [0003]    The setting and immobilization of bone fractures with simple splints and slings has been practiced since ancient times. Modem biomedical engineering has yielded increasingly advanced orthopedic fixation technology, including various internal and external devices, such as pins, braces, plates, and screws. Many of these devices are temporary, and require removal after surgery or at any of various times throughout the healing process. Some devices such as internal screws are often left in place indefinitely, due to the cost, potential complications, and difficulty of removing them. 
         [0004]    Typically, orthopedic hardware is removed at some time following surgery for various reasons. For example, a fastener embedded in bone can act as a stress riser, which may increase the risk of an undesired fracture in the bone proximate the fastener location. Additionally, over time, the position of a fastener can shift away from the initial embedded position, which may result in an infection or other negative side effect. At the very least, an un-removed fastener may simply cause discomfort, such as by conducting cold temperatures, or creating pain and irritation in the tissue surrounding the fastener. Although less likely, tan un-removed fastener may result in the potential inconvenience associated with metal detector false alarms. 
         [0005]    In addition to potentially negative consequences caused by leaving hardware fixed in a patient&#39;s bone, some negative effects may be caused during the installation of the hardware. For example, a fastener may become damaged during the process of insertion, such as stripping the head or breaking the head off entirely. Such damage to the head can make further insertion and/or extraction of the fastener highly problematic. 
         [0006]    The nature of bone itself also presents some challenges. As the bone heals, it tends to encase the fastener more tightly, which can increase the torque required to loosen the fastener from the bone. The bone may also encroach upon the head of the fastener making it difficult to access. Another problem arises from the hollow nature of bones. When removing a screw, once the threaded portion has been unscrewed from the distal cortex of the bone, there may be insufficient resistance offered by the screw head to keep the driver engaged. Moreover, even if the screw can be extracted to the point where the proximal end of the threaded portion comes into contact with the proximal cortex of the bone, the bone may have grown tightly around the shank, which can impede further progress. Accordingly, there may be insufficient resistance to keep the driver engaged in the head for the threads to bite. 
         [0007]    Other challenges analogous to those discussed above may also exist in non-medical positional fixation applications, such as applications involving materials such as wood, metal, and plastic, or any applications where a reliable and minimally invasive apparatus, system, or method for insertion and/or removal of a fastener is desired. 
       SUMMARY 
       [0008]    From the foregoing discussion, it should be apparent that a need exists for an apparatus, system, and method for the insertion and extraction of orthopedic fasteners which are problematically positioned or otherwise compromised. Beneficially, such an apparatus, system, and method would also be useful in non-medical applications. 
         [0009]    The present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available positional fixation instruments. Accordingly, the present invention has been developed to provide an apparatus, system, and method for positional fixation fastener operation, particularly extraction, which overcome at least one, many, or all of the above-discussed shortcomings in the art. 
         [0010]    Generally, an apparatus is provided that tightens around a fastener, locks the fastener into position, and unlocks and releases the fastener when the operation is complete. The apparatus can include a collet with a proximal end and a distal end. In some embodiments, the distal end can be compressible or expandable to conform to a proximal end of a fastener. The proximal end of the collet is received by a chuck body. The apparatus can also include a handle configured to receive, such as in a seated arrangement, a proximal end of the chuck body. The apparatus may include a closing mechanism coupled to the handle. The closing mechanism can be operable to cause the collet to be tightened against the handle, which, in some embodiments, causes a compressible distal end of the collet to conform to the proximal end of the fastener. 
         [0011]    In one embodiment, the closing mechanism may include a shaft longitudinally disposed within the handle for drawing the collet into the aperture of the chuck body so as to compress the collet around the proximal end of the fastener. A threaded connection between the shaft and a knob at a proximal end of the handle allows the collet to be tightened when the knob is turned in one direction, typically clockwise, and loosened when the knob is turned in an opposite direction. 
         [0012]    In certain implementations, the closing mechanism includes a lever connected to a distal end of the handle at a first pivot joint, a locking member including a distal end connected to the lever at a second pivot joint proximal to the first pivot joint, and a shaft longitudinally disposed within the handle. The shaft can be coupled to the proximal end of the collet at a distal end portion of the shaft and coupled to a proximal end of the locking member at a third pivot joint proximal to the second pivot joint. 
         [0013]    In a further implementation, the closing mechanism may also include a lever-operated linkage. The linkage may be comprised of a lever connected to a distal end of the handle by a first pivot joint, a locking member having a distal end connected to the lever by a second pivot joint proximal to the first pivot joint, and a proximal end connected through a channel in the side of the handle to the shaft by a third pivot joint. When the lever is depressed toward the handle, a proximal moment of force along the shaft draws the collet into the chuck body in a manner similar to the tightening of the above-described knob. Thus, the closing mechanism may comprise either the lever or the knob or both. When both are present, the knob permits an adjustment of the position of the third pivot joint to optimize the degree of force required to close the lever consistent with the strength of the operator and the structural integrity of the mechanism. 
         [0014]    In the fully closed position, the lever causes the second pivot joint to descend deeper into the channel than a line between the first pivot joint and the third pivot joint, thus diverting a small amount of the compression force between the chuck body and the collet to create a downward moment of force locking the lever against the handle. To unlock the mechanism, the lever is lifted away from the handle, relaxing the proximal force along the shaft and loosening the collet by extending it out of the chuck body. 
         [0015]    An ergonomic advantage may be obtained by allowing the lever to recess into the channel in the closed position, thereby permitting a more comfortable grip while using the instrument, as well as having the proximal end of the lever extend beyond the proximal end of the handle to facilitate lifting the lever out of the closed position. 
         [0016]    According to one implementation, the collet and even the chuck body may be disposable. For example, biological contamination may prevent reuse of these components, even if treated, such as in an autoclave. Moreover, in some implementations, the apparatus may further include a centrally aligned longitudinal bore through all of the apparatus components to admit a wire for purposes of alignment with a cannulated fastener. 
         [0017]    The apparatus, in one embodiment, is configured with a plurality of longitudinal slits in the compressible distal end of the collet, thereby forming a plurality of jaws. In some implementations, the jaws are able to flex outward to capture larger fasteners and flex inward under the compression force against the chuck body, thereby enabling a tighter grip on the proximal end of the fastener. 
         [0018]    The apparatus is further configured, in one embodiment, with a cutting edge on the distal end of the collet. The cutting edge is able to remove material from around the proximal end of the fastener within a medium composed of the material, such as bone growth that has encroached upon it. 
         [0019]    A system of the present invention is presented to operate compatibility with the wide variety of fasteners that exist or may be developed in the future. In particular, the system, in one embodiment, includes a plurality of interchangeable collets, each snugly conforming to the maximum perimeter of proximal end of a corresponding type or size of fastener. A special collet may even be provided to fit the shank of a broken fastener. In one specific implementation, a system for installing and removing fasteners from bone tissue includes a plurality of fasteners each comprising a proximal end portion having a different size. The system also includes a plurality of interchangeable collets each comprising a proximal end portion and a distal end portion. The distal end portion can be conformable to a perimeter of the proximal end portions of the plurality of fasteners. The system also includes a chuck body configured to receive the proximal end portion of each of the plurality of interchangeable collets and a handle configured to receive a proximal end of the chuck body. Additionally, the system includes a closing mechanism coupled to the handle. The closing mechanism includes a first tightening portion operable to partially conform the distal end portion of a respective collet to the perimeter of the proximal end portion of a respective fastener and a second tightening portion operable to further conform the distal end portion of the respective collet to the perimeter of the proximal end portion of the respective fastener. 
         [0020]    In certain implementations, the first tightening portion comprises a rotatable knob and the second tightening portion comprises a pivotable lever. Rotation of the knob can cause the chuck body to apply a first force to the distal end portion of the respective collet and pivoting the lever can cause the chuck body to apply a second force to the distal end portion of the respective collet where the second force is greater than the first force 
         [0021]    A method of the present invention is also presented for positional fixation. In one embodiment, the method substantially includes the actions necessary to carry out the functions of the apparatus and system described herein. In one particular embodiment, a method for securing a fastener includes removably positioning a chuck body within a handle, removably positioning a proximal end of a collet within the chuck body, and removably positioning a fastener within a compressible distal end of the collet. The method also includes adjusting a tightening portion of a closing mechanism coupled to the handle and collet to urge the distal end of the collet against the chuck body and partially compress the distal end of the collet against the fastener. Further, the method includes adjusting a locking portion of the closing mechanism to further urge the distal end of the collet against the chuck body and further compress the distal end of the collet against the fastener. 
         [0022]    In some implementations of the method, the tightening portion includes a knob coupled to the collet via a shaft. Adjusting the tightening portion can then include rotating the knob to urge the collet and shaft in a proximal direction. In other implementations, the locking portion includes a lever coupled to the collet via a shaft. Adjusting the locking portion can then include pivoting the lever toward the handle to urge the collet and shaft in a proximal direction. 
         [0023]    In one embodiment, a method includes accessing a material amenable to positional fixation, installing the collet, fitting the fastener into the collet, tightening and locking the fastener into place, extracting the fastener by means of the handle, and then unlocking, loosening, and separating the fastener from the instrument. The method also may include inserting the fastener, particularly if the head is damaged, or if the torque required to fully insert a fastener, such as a screw, might strip the head if a conventional screwdriver were used. In a further embodiment, the method includes discarding the collet if it is not reusable, such as due to biological contamination. 
         [0024]    Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present invention should be or are in any single embodiment of the invention. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, discussion of the features and advantages, and similar language, throughout this specification may, but do not necessarily, refer to the same embodiment. 
         [0025]    Furthermore, the features, advantages, and characteristics of the apparatus, system, and method described herein may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the invention may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the invention. 
         [0026]    These features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0027]    In order that the advantages of the invention will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only certain illustrative embodiments and are not therefore to be considered to be limiting of its scope, further embodiments of the invention will be described and explained with additional specificity and detail through the use of the specification, claims, and accompanying drawings, in which: 
           [0028]      FIG. 1  is a perspective view illustrating one embodiment of a positional fixation instrument in accordance with the present invention; 
           [0029]      FIG. 2  is a side view further illustrating the instrument of  FIG. 1  holding a fastener; 
           [0030]      FIG. 3  is an exploded side view of the instrument and fastener of  FIG. 2 ; 
           [0031]      FIG. 4  is a front view of the instrument of  FIG. 1 ; 
           [0032]      FIG. 5  is a rear view of the instrument of  FIG. 1 ; 
           [0033]      FIG. 6  is a cross-sectional side view of the instrument of  FIG. 1  taken along the line  6 - 6  of  FIG. 4  and showing a closing mechanism in an open position; 
           [0034]      FIG. 7  is a cross-sectional side view of the closing mechanism of  FIG. 6  in a closed position; 
           [0035]      FIG. 8  is a detailed perspective view of a chuck body according to one embodiment; 
           [0036]      FIGS. 9A-9C  are a detailed perspective view of a plurality of collets according to several embodiments; 
           [0037]      FIGS. 10A and 10B  are a detailed cross-sectional side view taken along the line  10 A- 10 A of  FIG. 10B  and a front view, respectively, of a collet according to a first embodiment; 
           [0038]      FIGS. 11A and 11B  are a detailed cross-sectional side view taken along the line  11 A- 11 A of  FIG. 11B  and a front view, respectively, of a collet according to a second embodiment; 
           [0039]      FIGS. 12A and 12B  are a detailed cross-sectional side view taken along the line  12 A- 12 A of  FIG. 12B  and a front view, respectively, of a collet according to a third embodiment; 
           [0040]      FIGS. 13A and 13B  are a side view and front view, respectively, of a collet according to a fourth embodiment; 
           [0041]      FIGS. 14A and 14B  are a side view and front view, respectively, of a collet according to a fifth embodiment; 
           [0042]      FIGS. 15A and 15B  are a detailed cross-sectional side view taken along the line  15 A- 15 A of  FIG. 15B  and a front view, respectively, of a collet according to a sixth embodiment; and 
           [0043]      FIG. 16  is a flow diagram illustrating one embodiment of a method for employing the instrument in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION  
       [0044]    Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. Furthermore, the described features, structures, or characteristics of the invention may be combined in any suitable manner in one or more embodiments. Additionally, one skilled in the relevant art will recognize that the invention may be practiced without one or more of the specific details described herein, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention. 
         [0045]    The schematic flow chart diagrams included herein are generally set forth as logical flow chart diagrams. As such, the depicted order and labeled steps are indicative of one embodiment of the presented method. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the illustrated method. Additionally, the format and symbols employed are provided to explain the logical steps of the method and are understood not to limit the scope of the method. Although various arrow types and line types may be employed in the flow chart diagrams, they are understood not to limit the scope of the corresponding method. Indeed, some arrows or other connectors may be used to indicate only the logical flow of the method. For instance, an arrow may indicate a waiting or monitoring period of unspecified duration between enumerated steps of the depicted method. Additionally, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown. 
         [0046]    Referring to  FIG. 1 , one embodiment of a positional fixation instrument  100  in accordance with the present invention is shown having an interchangeable collet  102  or chuck tip. The collet  102  is received by a chuck body  104  which is seated in a handle  106  and held in place by a set screw  108 . The collet  102  may be tightened by adjusting a tightening portion and further tightened or locked in place by adjusting a locking portion. The tightening portion includes a knob  110  and is adjusted by turning the knob  110  in one direction, typically clockwise, to draw the collet  102  into the chuck body  104 . The collet  102  may be opened and loosened by turning the knob  110  in an opposite direction, which extends the collet  102  out of the chuck body  104 . The locking portion includes a lever  112  and locking member  114 . The collet  102  maybe further tightened and locked by depressing lever  112 , causing a locking member  114  to descend into a channel  116  along the side of the handle  106 , and may be unlocked by lifting the lever  112 . 
         [0047]      FIG. 2  is a side view further illustrating the instrument  100  holding a fastener  202 . The lever  112  is in a fully closed and locked position, causing the collet  102  to close around and tightly grip the fastener  202 . Note that in this configuration the lever  112  fits within the channel  116 , thus providing an ergonomic handhold for operation of the instrument  100  in positioning the fastener  202 . 
         [0048]      FIG. 3  is an exploded side view of the instrument  100  and the fastener  202 . In one embodiment, the fastener  202  is a screw, having a threaded portion  302  connected via a shank  304  to a proximal end  306 . Alternative embodiments of the fastener  202  may include a bolt, a pin, a rivet, a nail, a staple, an anchor, or some other fastener. The proximal end  306  as illustrated is a uniform sized head. Further embodiments of the proximal end  306  may include a non-uniform sized head or a headless fitting. In one embodiment, the threaded portion  302  may have a distal self-tapping or self-drilling end  308  to facilitate insertion of the fastener  202  by turning it in one direction, typically clockwise, and a proximal end  310  opposite the distal self-tapping end. 
         [0049]    The collet  102  has a compressible distal end  312  which is designed to fit over and snugly conform in shape to the proximal end  306  of the fastener  202 . In some embodiments, the collet  102  is configured to fit the proximal end  306  of a respectively sized and specific type of fastener. However, in other embodiments, the range of compression of the collet  102  allows the collet to fit several differently sized and/or types of fasteners. For example, in one specific implementation, the collet  102  is configured to fit over and snugly conform in shape to proximal ends  306  of fasteners  202  sized between about 6 mm and about 4.3 mm. Of course, in other implementations, the collet  102  can be sized to conform to proximal ends  306  of fasteners  202  within any of various size ranges. In some instances, larger proximal ends  306  may initially cause the compressible distal end  312  of the collet  102  to expand as the collet is placed about the proximal end to accommodate the larger size of the proximal end. However, tightening of the collet to the hand tool will cause the “expanded” compressible distal end to at least slightly compress to ensure a tight fit around the proximal end. A collet  1022  configured to expand as the collet is tightened to the hand tool is described below in relation to  FIGS. 15A and 15B . In another embodiment, a specialized collet  102  may also be provided to fit a specifically sized shank  304  or differently sized shanks of the fastener  202  in the event that the proximal end  306  has broken off of the fastener. 
         [0050]    The collet  102  is installed by inserting its threaded proximal end  314  through the chuck body  104  into a shaft  316  and screwing it firmly in place. The chuck body  104  is seated in the handle  106  and held in place by tightening the set screw  108  into a set screw hole  318  (set screw  108  not shown in  FIG. 3 ). In the illustrated exploded view, part of the shaft  316  is visible through the set screw hole  318 . As the shaft  316  is retracted into the handle by means of the knob  110  and/or the lever  112 , the collet  102  is in turn drawn into the chuck body  104 , thereby compressing the compressible distal end  312  and tightening its grip around the corresponding proximal end  306  of the fastener  202 . 
         [0051]      FIG. 4  is a front view of the instrument  100 , with the chuck body removed to better reveal its internal structure. As shown with the lever  112  in the closed position, the handle  106  is roughly cylindrical in shape, with the lever mount  402  on top. In alternative embodiments, the handle can have any of various shapes, such as ovular, triangular, elliptical, and hexagonal. The chuck seat  404  is countersunk into the handle  106  to receive the chuck body  104  as it encircles the shaft  316 . A threaded hole  406  is provided in the shaft  316  to accept the threaded proximal end  314  of the collet  102 . A central bore  408  runs the length of the instrument  100  to allow passage of a guide wire (not shown) as used in conjunction with a cannulated fastener. Accordingly, the collet  102 , chuck body  104 , handle  106 , shaft  316 , and knob  110  include central bores that collectively define the bore  408 . 
         [0052]      FIG. 5  is a rear view of the instrument  100 , providing a clear illustration of the channel  116  in line with the lever  112 . It can be seen that the knob  110  is hollow, being connected to the shaft  316 , thereby retracting or extending the collet  102  via the threaded hole  406  in the shaft  316  when the knob  110  is respectively turned in one direction or another. The central bore  408  is also visible in this view, since it passes all the way through the shaft  316  and emerges into the hollow knob  110 . 
         [0053]    As shown in  FIG. 6 , the knob  110  of instrument  100  is coupled to the shaft  316  via an extended portion  602 . In the illustrated embodiment, the knob  110 , shaft  316 , and extended portion  602  form a one-piece monolithic construction with each other. The handle  106  includes a central bore  140  having a first proximal portion  142  coaxial with a second distal portion  144 . The first proximal portion  142  is sized to matingly receive the shaft  316  and the second distal portion  144  is sized to matingly receive the extended portion  602  of the knob  110 . The shaft  316  and extended portion  602  are rotatable within the first proximal and second distal portions  142 ,  144 , respectively. Preferably, the first proximal portion  142  retains the shaft is substantially coaxial alignment with the first proximal portion and the second distal portion  144  retains the extended portion is substantially coaxial alignment with the second distal portion. The lever  112  is connected to the handle  106  via a first pivot joint  604 . A second pivot joint  606  connects the lever  112  to a distal end of the locking member  114 . A proximal end of the locking member  114  is in turn connected to the extended portion  602  of the knob  110  via a third pivot joint  608 . The chuck seat  404  and central bore  408  are also shown in this view. 
         [0054]    The proximal end of the locking member  114  is secured to the third pivot joint  608  via a shackle member  620  coupled to the shaft  316 . The shackle member  620  is configured to ensure that the third pivot joint  608  moves axially when the shaft  316  moves axially, and that the shaft  316  is rotatable relative to the third pivot joint. The shackle member  620  includes two space-apart tabs  622  extending vertically away from the shaft  316  and a sleeve portion  624  wrapped about at least half of the periphery of the shaft. The proximal end of the locking member  114  is positioned between the tabs  622  and secured to the tabs by extending the pivot joint  608  through apertures in the tabs and locking member. When secured to the proximal end of the locking member  114 , the shackle member  620  is configured to retain the third pivot joint  608  in a vertically fixed location (as shown in  FIG. 6 ) relative to the shaft  316 , but allow the shaft to rotate relative to the shackle member. The shackle member  620  is prevented from moving axially or horizontally (as shown in  FIG. 6 ) relative to the shaft  316  through use of a stop  626  secured to and fixed relative to the shaft and extended portion  602 . More specifically, the shackle member  620  is effectively sandwiched between the stop  626  and the extended portion  602  of the knob  110 . The stop  626  prevents movement of the shackle member  620  in a first axial direction relative to the shaft  316  and the extended portion  602  prevents movement in a second axial direction opposite the first relative to the shaft. The stop  626  transfers collet disengaging thrust loading from the lever  114  to the shaft  316  when releasing a fastener from the collet and the extended portion  602  transfers collet engaging thrust loading from the lever  114  to the shaft  316  when securing a fastener in the collet. In one specific embodiment, the stop  626  is an external snap ring engaged within a recess  628  formed in the outer surface of the shaft  316 . 
         [0055]    Referring to  FIG. 7 , as the lever  112  is depressed, the second pivot joint  606  is brought directly into line with the first pivot joint  604  and the third pivot joint  608  to drive the shaft  316  and knob  110  in a proximal direction, i.e., distal-to-proximal direction, as indicated by directional arrow  610 . Movement of the shaft  316  and knob  110  in the proximal direction after the collet has been tightened against the chuck body  104  using the knob results in the application of a maximal compression force between the compressible distal end  312  of the collet  102  and the chuck body  104  as described above. When the lever  112  is in the fully closed position as shown, the second pivot joint  606  is substantially aligned with, but slightly below a line between, the first pivot joint  604  and third pivot joint  608 , thus diverting a small amount of the maximal compression force into a downward moment of force which holds the lever  112  down and locks the closing mechanism  600  in the fully closed position. Note that the lever  112  extends proximally beyond the handle  106 , providing convenient access for lifting it to unlock the closing mechanism  600 . 
         [0056]    As shown in  FIG. 8 , a central bore  806  runs a length of the chuck body  104  from a distal end  810  to a proximal end  812 . The chuck body  104  includes a collet engaging portion  802  extending from the distal end  810  to a location intermediate the distal end and proximal end  812 . The central bore  806  along the collet engaging portion  802  is inwardly tapered in a distal end to proximal end direction. The taper of the central bore  806  approximately corresponds with a distal-to-proximal taper of the outer surface of the compressible distal end of a collet in an uncompressed state (see, e.g., distal end  312  of collet  102 C of  FIG. 9C ). When initially assembled, the corresponding tapered surfaces of the central bore  806  and distal end  312  of the collet engage each other such that the distal end  812  of the collet  102 C matingly seats within the central bore. As the lever  112  is closed, the compressible distal end  312  of the collet slides along the central bore  806  of the collet engaging portion  802  in the distal-to-proximal direction relative to the central bore such that the wall of the central bore exerts an inwardly directed force against the compressible distal end of the collet. The inwardly directed force causes the compressible distal end  312  of the collet  102 C to gradually deform and radially compress against the proximal end  306  of the fastener  202 . The tapered nature of the engaging surfaces distributes the inwardly directed force evenly across the distal end  312  of the collet  102 C to facilitate ease in compressing the distal end against the fastener. The tapered surface of the central bore  806  is also configured to engage and facilitate compression of a distal end of a collet having a curved or arcuate shaped outer surface (see, e.g., distal end  312  of collet  102  of  FIG. 3  and distal end  312  of collet  102 B of  FIG. 9B ). 
         [0057]    The chuck body  104  also includes a key or spline  820  extending inwardly from the inner surface of the central bore  806  in a direction parallel to the axis of the chuck body. The key  820  can extend between the distal end  810  to a location intermediate the distal end  810  and the proximal end  812 . The key  820  is configured to engage a keyway or slot  822  formed in the collet and extending in a direction parallel to the axis of the collet (see, e.g., collet  102 C of  FIG. 9C ). In other words, as the collet is inserted into the chuck body  104 , the key  820  is positioned and retained within the keyway  822 . Engagement between the key  820  and keyway  822  reduces, restricts, or prevents rotation of the collet relative to the chuck body  104 . Additionally, the key  820  and keyway  822  are axially aligned when the collet is properly seated in the chuck body. The axial alignment between the key and keyway allows for relative movement between the collet and chuck body in the axial or lengthwise direction. Although in the illustrated embodiments, the key  820  is formed in the central bore  806  of the chuck body  104  and the keyway is formed in the collet  102 C, in other embodiments, the key can be formed in the collet and the keyway can be formed in the central bore. 
         [0058]    In alternative embodiments, configurations other than a key-keyway or spline configuration can be used to reduce, restrict, or prevent relative rotation between the chuck body and collet. For example, in certain implementations, a portion of the central bore  806  can have an out-of-round cross-sectional shape and the outer surface of the collet can have an out-of-round shape at least approximately matching the out-of-round cross-sectional shape of the central bore. When the collet is inserted into the central bore  806 , the out-of-round portion of the collet can be positioned within and matingly engage the out-of-round portion of the central bore  806 . Because the portions of the central bore  806  and collet are out-of-round, engagement between them at least restricts rotation of the collet relative to the chuck body  104 . In specific implementations, the out-of-round shape can be any of various shapes, such as hexagonal, triangular, rectangular, and ovular. 
         [0059]    Also shown is  FIG. 8  is a set screw depression  804  formed in an outer surface of the chuck body  104 . The depression  804  is configured to engage the set screw  108  thereby holding the chuck body  104  firmly in place within the chuck seat  404  (see  FIG. 6 ). 
         [0060]      FIGS. 9A-9C  are detailed perspective views of a plurality of collets  102 A- 102 C. Collets  102 B,  102 C include longitudinal slits  902  cut in the compressible distal end  312  thereby forming jaws  904 . The jaws  904  are able to flex inward under the compression force from the chuck body  104 , thereby enabling a tight grip on the proximal end  306  of the fastener  202 . The slits  902  are narrow enough not to compromise the snug conformity or tight fit between the collets  102 B,  102 C and the proximal end  306  of the fastener  202 . 
         [0061]    As shown in  FIG. 9C , the jaw  904  of collet  102 C may have a cutting edge  906  configured to remove material from around the proximal end  306  of the fastener  202 . For example, the material may be bone which has grown around the edges of the proximal end  306  and must be cut away in order to expose enough of the fastener  202  to achieve a tight grip necessary for extracting the fastener. The collet  102 C can be rotated while applying a force to the collet directed toward the material to be removed. As the collet  102 C is rotated, the cutting edge  906  cuts through the material. 
         [0062]      FIGS. 10A and 10B  show a detailed side cutaway view and front view, respectively, of a collet  1002 . The collet  1002  is a radial engagement (RE) type collet with longitudinal slits  902  and short clearance cutters each having a cutting edge  906 .  FIGS. 11A and 11B  show a detailed side cutaway view and front view, respectively, of a collet  1006 . The collet  1006  is an RE type collet with a clearance cutting body  1008 , a cutting edge  906 , and longitudinal slits  902 .  FIGS. 12A and 12B  show a detailed side cutaway view and front view, respectively, of a collet  1010 . The collet  1010  is an RE type collet with a tor engage screw shank boring body  1012 , a cutting edge  906 , and longitudinal slits  902 .  FIGS. 13A and 13B  show a side view and front view, respectively, of a collet  1014 . The collet  1014  is a hex drive solid collet without a compressible distal end.  FIGS. 14A and 14B  show a side view and front view, respectively, of a collet  1018 . The collet  1018  is an “easy-out” type extractor solid collet without a compressible distal end. The distal ends of the collets  1014 ,  1018  are not compressible, but include recesses for receiving a standard sized fastener head. 
         [0063]    Solid collets, such as collets  1014 ,  1018  are usable to insert a fastener having a standard head into bone tissue and to extract the fastener if the head has not broken away from the shank. As discussed above, if the head has indeed broken away from the shank or extracting the fastener by gripping the shank is more desirable, a collet having a compressible distal end may be more desirable. 
         [0064]      FIGS. 15A and 15B  show a detailed side cutaway view and front view, respectively, of a collet  1022 . The collet  1022  is an expandable tip collet for gripping hollow fasteners and non-fasteners from the inside of the fasteners and non-fasteners, respectively. For example, the tip of the collet  1022  can be inserted into the hollow interior of an embedded fastener. As the threaded proximal end of the collet  1022  is rotated and moved proximally via the hand tool  100  as discussed above, an interior member secured to the threaded proximal end correspondingly rotates and moves relative to an exterior member, which is prevented from proximal movement via the chuck body  104 . The distal tip of the interior member is beveled such that as it moves proximally relative to the exterior member, it causes the exterior member to expand outwardly until it tightly grips an interior surface of the hollow fastener. The embedded fastener can then be removed by pulling or rotating the hand tool  100 . 
         [0065]    Like the hand tool  100 , the collets described herein can each have a central bore running the length of the collets to allow for passage of a guide wire as used in conjunction with a cannulated fastener (see, e.g., collets  1002 - 1022  of  FIGS. 10A-15B ). In this manner, a guide wire can extend through the bore  408  in the hand tool  100 , the collet, and the fastener. 
         [0066]    The components of the instruments  100  can be made from any of various materials. For example, in some embodiments, each of the components is made from a metal or metal alloy, such as steel, stainless steel, and/or aluminum. Also, one or more components can be made from a high-strength plastic or polymer. 
         [0067]      FIG. 16  is a flow diagram illustrating one embodiment of a method  1600  for employing a fastener extraction and insertion instrument, such as instrument  100 , in accordance with the present invention. The method  1600  starts  1602  by accessing  1604  material requiring positional fixation or in which a fastener is positionally fixed. The method  1600  proceeds by providing  1606  an instrument (e.g., instrument  100 ) and installing  1608  a collet (e.g., collet  102 ) in the instrument. A proximal end of a fastener (e.g., proximal end  306  of fastener  202 ) is then fitted  1610  into a snugly conforming compressible distal end (e.g., end  312 ) of the collet. The proximal end of the fastener is partially tightened  1612  within the collet by adjusting a tightening portion of a closing mechanism, e.g., turning a knob (e.g., knob  110 ) in a tightening direction. Adjusting the tightening portion urges the distal end of the collet against a chuck body of the instrument and partially compresses the distal end of the collet against the fastener. The proximal end of the fastener is fully tightened and locked  1614  in place by adjusting a locking portion, e.g., depressing a lever (e.g., lever  112 ). Adjusting the locking portion further urges the distal end of the collet against the chuck body and further compresses the distal end of the collet against the fastener. 
         [0068]    If the fastener is already embedded in the material, then it is extracted  1618  by operating a handle (e.g.,  106 ) of the instrument, such as pulling the handle away from the material. If the fastener  202  is not embedded or only partially embedded in the material, then the fastener is inserted  1620  inserted into the material to completely embed the fastener in the material by operating the handle, such as pushing the handle toward the material. When the extraction  1618  or insertion  1620  of the fastener is complete, then the fastener is at least partially loosened or unlocked  1622  from the instrument by lifting the lever and, if necessary, further loosened by loosening  1624  the collet by turning the knob in a loosening direction opposite the tightening direction. Unlocking  1622  the fastener and further loosening  1624  the collet allows the fastener to be separated  1626  from the collet. The collet is then removed  1628  from the instrument. If the collet can be resused as determined at  1630 , then the method ends  1634 . However, if the collet cannot be reused, such as due to contamination, as determined at  1630 , then the collet may be discarded  1632  prior to the end  1634  of the method  1600 . 
         [0069]    The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.