Abstract:
A battery pack for a use with a powered surgical tool. The battery pack may include a housing with an outer wall and opposing first and second ends. The housing may include an elongated shape that extends between the first and second ends. A first member may extend across the first end of the housing and include a first aperture, and a second end member may extend across the second end of the housing and may include a second aperture. A passage may extend through the housing with a first end that aligns with the first aperture and a second end that aligns with the second aperture. The housing may be sized for a plurality of storage locations positioned between the first and second members and around the passage, and each of the storage locations may be configured to store a power cell.

Description:
RELATED APPLICATION 
       [0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 12/559,182 filed on Sep. 14, 2009 and herein incorporated by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Disclosure 
         [0003]    This disclosure is directed to a surgical tool, and more particularly directed toward a surgical tool for removing a portion of an implant. 
         [0004]    2. Description of the Related Art 
         [0005]    There are a variety of different spinal diseases, such as scoliosis, as well as others, which may be cured or mitigated by implantation of certain devices. Such devices can include articles and mechanisms useful for repairing damaged portions of the spine, stabilizing portions of the spine, or changing the position of the spine to a more healthy state. For example, rod and anchor systems are commonly employed when portions of the spine need to be realigned, such as in patients with abnormal curvatures, wherein the rod provides rigid support for urging the spine to a more healthy position. 
         [0006]    Typically, the process of implanting rod and anchor systems can be quite daunting, including the implantation of multiple anchors or bone screws within particular locations of the spine and then attaching each of the anchors to a rod. Depending upon the severity of the spinal disease and the necessary suitable treatment, such surgeries can last hours if not more. Moreover, most of the components used in the surgery are rigid components that must be physically manipulated by a surgeon while in the patient (i.e., in-situ) leading to potential physical harm to the patient as some of the procedures can result in substantial jarring of the patient including for example, shearing off the head portions of set screws for permanent placement. Additionally, such manipulation by a surgeon may also compromise the integrity of the implanted object lessening its capabilities. Given the delicacy of surgical procedures and the anatomical importance of the spine, jarring of the patient during such surgical procedures is inherently dangerous. Additionally, the vast majority of these surgical procedures are completed by handheld manual tools, meaning hours of rigorous work for a surgeon to implant all the screws and properly align the spine with an implanted rod. 
       SUMMARY 
       [0007]    The present application is directed to a battery pack for a use with a surgical tool. The battery pack may include a housing with an outer wall and opposing first and second ends. The housing may include an elongated shape that extends between the first and second ends. A first member may extend across the first end of the housing and include a first aperture, and a second end member may extend across the second end of the housing and may include a second aperture. A passage may extend through the housing with a first end that aligns with the first aperture and a second end that aligns with the second aperture. The housing may be sized for a plurality of storage locations positioned between the first and second members and around the passage, and each of the storage locations may be configured to store a power cell. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  includes a lateral view of a portion of a vertebral column. 
           [0009]      FIG. 2  includes a top plan view of a vertebra. 
           [0010]      FIG. 3  includes a side view of a surgical tool in accordance with an embodiment. 
           [0011]      FIG. 4  includes a cross-sectional illustration of a surgical tool in accordance with an embodiment. 
           [0012]      FIG. 5  includes a perspective view of the bayonet portion of the surgical tool in accordance with an embodiment. 
           [0013]      FIG. 6  includes a perspective view of a portion of the output shaft of the surgical tool in accordance with an embodiment. 
           [0014]      FIG. 7  includes a partial cross-section of a portion of the output shaft of the surgical tool in accordance with an embodiment. 
           [0015]      FIG. 8  includes a perspective view of a portion of the housing and sleeve of the surgical tool in accordance with an embodiment. 
           [0016]      FIG. 9  includes an exploded view of components within a sleeve portion of the surgical tool in accordance with an embodiment. 
           [0017]      FIG. 10  includes a perspective view of components within the sleeve portion of the surgical tool in accordance with an embodiment. 
           [0018]      FIG. 11  includes a cross-sectional view of components within the sleeve portion of the surgical tool in accordance with an embodiment. 
           [0019]      FIG. 12  includes a partial cross-sectional view of components within the sleeve portion of the surgical tool in accordance with an embodiment. 
           [0020]      FIGS. 13 and 14  include clutch plates for use in a portion of the surgical tool in accordance with an embodiment. 
           [0021]      FIG. 15  includes a cross-sectional illustration of a trigger for use with the surgical tool in accordance with an embodiment. 
           [0022]      FIG. 16  includes a perspective view of a battery pack for use with the surgical tool in accordance with an embodiment. 
           [0023]      FIG. 17A  includes a cross-sectional illustration of the battery pack for use with a surgical tool in accordance with an embodiment. 
           [0024]      FIG. 17B  includes a perspective view of another battery pack for use with a surgical tool in accordance with an embodiment. 
           [0025]      FIG. 18  includes a perspective view of a surgical tool according to another embodiment. 
           [0026]      FIG. 19  includes a perspective view of a portion of a surgical tool and certain components within the tool in accordance with an embodiment. 
           [0027]      FIG. 20  includes a perspective view of a portion of a surgical tool including an inner sleeve in accordance with an embodiment. 
           [0028]      FIG. 21  includes a perspective view of a portion of a surgical tool including certain components within the tool in accordance with an embodiment. 
           [0029]      FIG. 22  includes a perspective view of a cap portion and certain components within the cap portion in accordance with an embodiment. 
           [0030]      FIG. 23  includes a perspective view of a portion of the tool including the inner sleeve and cap portion as assembled in accordance within an embodiment. 
           [0031]      FIG. 24  includes a perspective view of an outer sleeve in accordance with an embodiment. 
           [0032]      FIG. 25  includes a perspective view of an outer sleeve in accordance with an embodiment. 
           [0033]      FIG. 26  includes a perspective view of the outer sleeve and associated components for use in the tool in accordance with an embodiment. 
           [0034]      FIG. 27A  and  FIG. 27B  include cross-sectional illustrations of a portion of the tool including the outer sleeve and actuator arm in a disengaged state and in an engaged state according to an embodiment. 
           [0035]      FIG. 28  includes a cross-sectional illustration of a portion of the tool including the trigger according to an embodiment. 
           [0036]      FIG. 29  includes a perspective view illustration of a portion of the tool including the outer sleeve and associated components according to an embodiment. 
           [0037]      FIG. 30  includes a perspective view illustration of the tool including particular release mechanisms according to an embodiment. 
           [0038]      FIG. 31  includes a cross-sectional illustration of a portion of the tool including a release mechanism according to an embodiment. 
           [0039]      FIG. 32  includes a cross-sectional illustration of a portion of the tool including a release mechanism according to an embodiment. 
           [0040]      FIGS. 33 and 34  include illustrations of a procedure using the surgical tool to remove a head portion of a set screw in accordance with an embodiment. 
           [0041]      FIG. 35  includes a side view of a surgical tool with a guide wire extending through the interior in accordance with an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
     Description of Relevant Anatomy 
       [0042]    Referring initially to  FIG. 1 , a portion of a vertebral column, designated  100 , is shown. As depicted, the vertebral column  100  includes a lumbar region  102 , a sacral region  104 , and a coccygeal region  106 . The vertebral column  100  also includes a cervical region and a thoracic region. For clarity and ease of discussion, the cervical region and the thoracic region are not illustrated. 
         [0043]    As illustrated in  FIG. 1 , the lumbar region  102  includes a first lumbar vertebra  108 , a second lumbar vertebra  110 , a third lumbar vertebra  112 , a fourth lumbar vertebra  114 , and a fifth lumbar vertebra  116 . The sacral region  104  includes a sacrum  118 . Further, the coccygeal region  106  includes a coccyx  120 . 
         [0044]    As depicted in  FIG. 1 , a first intervertebral lumbar disc  122  is disposed between the first lumbar vertebra  108  and the second lumbar vertebra  110 . A second intervertebral lumbar disc  124  is disposed between the second lumbar vertebra  110  and the third lumbar vertebra  112 . A third intervertebral lumbar disc  126  is disposed between the third lumbar vertebra  112  and the fourth lumbar vertebra  114 . Further, a fourth intervertebral lumbar disc  128  is disposed between the fourth lumbar vertebra  114  and the fifth lumbar vertebra  116 . Additionally, a fifth intervertebral lumbar disc  130  is disposed between the fifth lumbar vertebra  116  and the sacrum  118 . 
         [0045]    In a particular embodiment, if one of the intervertebral lumbar discs  122 ,  124 ,  126 ,  128 ,  130  is diseased, degenerated, or damaged or if one of the zygapophyseal joints is diseased, degenerated or damaged, that disc or joint can be treated with an implanted device. 
         [0046]    Referring to  FIG. 2 , a top plan view of a vertebra is illustrated. As shown, the vertebral body  204  of the inferior vertebra  202  includes a cortical rim  230  composed of cortical bone. Also, the vertebral body  204  includes cancellous bone  232  within the cortical rim  230 . The cortical rim  230  is often referred to as the apophyseal rim or apophyseal ring. Further, the cancellous bone  232  is generally softer than the cortical bone of the cortical rim  230 . 
         [0047]    As illustrated in  FIG. 2 , the inferior vertebra  202  further includes a first pedicle  214 , a second pedicle  228 , a first lamina, and a second lamina. Further, a vertebral foramen  222  is established within the inferior vertebra  202 . A spinal cord  216  passes through the vertebral foramen  222 . Moreover, a first nerve root  218  and a second nerve root  226  extend from the spinal cord  216 . In particular, the first pedicle  214  and the second pedicle  228  represent regions of the spine in which surgeons often choose to implant anchors, such as bone screws for attaching an anchor and rod system to the spine. Notably, given the proximity to the spinal cord  216  and other significant anatomical portions, the implantation of such screws is a delicate and precise procedure requiring tools significantly different than available to the general public. 
         [0048]    The vertebrae that make up the vertebral column have slightly different appearances as they range from the cervical region to the lumbar region of the vertebral column. However, all of the vertebrae, except the first and second cervical vertebrae, have the same basic structures, e.g., those structures described above in conjunction with  FIG. 2 . The first and second cervical vertebrae are structurally different than the rest of the vertebrae in order to support a skull. 
         [0049]    Referring now to  FIGS. 3-19  embodiments describing a surgical tool, its components and methods of using the surgical tool are provided. Accordingly, referring to  FIG. 3  a side view illustration of a surgical tool is provided in accordance with an embodiment. As illustrated, a surgical tool  300  includes a housing  301  having a proximal end  303  and a distal end  305 . The housing  301  further includes a handle portion  311  coupled to the housing  301  between the proximal end  303  and the distal end  305 . As further illustrate, the surgical tool  300  includes a bayonet portion  309  coupled to the housing  301  adjacent to the distal end  305 , and a sleeve portion  307  coupled to the housing  301  and abutting the bayonet portion  309 . The surgical tool  300  further includes an effector, or in particular embodiments, an output shaft  315 , coupled to the housing  301  adjacent to the distal end  305 . The surgical tool  300  further includes a reaction arm, or in accordance with particular embodiments, a counter-torque sleeve  313 , overlying the output shaft  315  and coupled to the housing  301  adjacent to the distal end  305 . 
         [0050]    Referring to the surgical tool  300  with more particularity,  FIG. 4  provides a cross-sectional illustration of the surgical tool in accordance with one embodiment. The cross-sectional illustration of  FIG. 4  is provided for clarity and to illustrate the interaction of all the components, as such may be referred to throughout the detailed description. 
         [0051]    In reference to the operation of the tool, generally the surgical tool  300  is capable of providing a rotational force to an implant via the output shaft  315 . In particular, a user depresses a trigger  405  coupled to the handle  311  which is coupled to an actuator  440 . The actuator  440  is coupled to a motor  407  and configured to engage the motor  407  such that a motor shaft  411  is rotated upon actuation of the motor  407 . Depending upon the position of a sleeve portion  307  and components within the sleeve portion, which will be described in more detail herein, the motor shaft  411  can be coupled to the output shaft  315  which in turn will cause rotation of the output shaft  315 . According to a particular embodiment, coupling of the motor shaft  411  and output shaft  315  is facilitated by axial movement of the sleeve portion  307  such that components within the sleeve including a spline drive  913  and hex drive output gear  909  are operably coupled and result in coupling of the motor shaft  411  and the output shaft  315 . Moreover, axial movement of the sleeve portion  307  causes respective axial movement of the counter-torque sleeve  313  such that the counter-torque sleeve  313  can be positioned on the implant engaged by the output shaft  315 . 
         [0052]    In further reference to the general operation of the surgical tool  300 , the motor  407  can be a DC electric motor and accordingly can be electrically connected to power sources  409 , including for example batteries. According to one embodiment, the power sources  409  can be disposed in a housing, such as a battery pack, that is adjacent to the proximal end  303  of the housing  301 . 
         [0053]    The surgical tool  300  can further include optical indicator  450  coupled to the housing and configured to provide feedback to the user regarding a state of the tool. Generally, the optical indicator  450  can be electrically coupled to the power sources  409 . In one embodiment, the optical indicator  450  can include a light, such as a light emitting diode (LED). In a more particular embodiment, the optical indicator  450  can indicate whether the sleeve portion  307  and the counter-torque sleeve  313  have traveled a requisite axial distance such that the tool will operate. Accordingly, in such embodiments, the light may further be electrically coupled to a switch or a microprocessor. 
         [0054]    Additionally, the surgical tool  300  can further include an audible indicator coupled to the housing and configured to provide feedback to the user regarding a state of the tool. Accordingly, the audible indicator can provide the same function as the optical indicator as described above. 
         [0055]    In reference to components at the distal end of the surgical tool  300 , according to one embodiment, the output shaft  315  is coupled to the housing  301 . According to a particular embodiment, the output shaft  315  is coupled to the motor shaft  411  which is directly connected to the motor  407  and the motor is directly connected to the housing  301 . Moreover, the counter-torque sleeve  313  overlies the output shaft  315  and is coupled to the housing  301 . In accordance with one particular embodiment, the counter-torque sleeve  313  is directly connected to the bayonet  309  that is a portion of the housing  301 . As such, in accordance with an aspect of the present disclosure, the output shaft  315  and the counter-torque sleeve  313  are coupled to the housing such that upon rotation of the output shaft  315  on an implant the forces transmitted by the output shaft  315  and the counter-torque  313  are balanced by their respective couplings to the housing  301 . 
         [0056]    As the surgical tool  300  is intended for use in surgeries, the tool, and more particularly components contained therein, must be sterilizable. As such, in accordance with one particular embodiment, components of the surgical tool  300 , including for example, the output shaft  315 , the counter-torque sleeve  313 , the bayonet portion  309 , and portions of the housing  301  are made of materials that are autoclavable. As such, the components must be capable of withstanding temperatures in excess of 130° C., as well as pressures in excess of 140 psi. In one embodiment, components illustrated in  FIG. 3  can be made of a metal or metal alloy. Suitable metal or metal alloys can include tungsten, magnesium, aluminum, iron, cobalt, nickel, titanium, steel, chromium, or any combinations thereof. In another embodiment, the components illustrated in  FIG. 3  can include a non-metal, such as carbon, and more particularly carbon fiber. In accordance with another embodiment, the components within the surgical tool  300  can include high temperature polymer materials. In a more particular embodiment, suitable polymer materials can include polyurethane materials, polyolefin materials, polyether materials, silicone materials, or a combination thereof. Further, the polyolefin materials can include polypropylene, polyethylene, halogenated polyolefin, fluoropolyolefin, or a combination thereof. The polyether materials can include polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyaryletherketone (PAEK), or a combination thereof. Other suitable materials can include styrenes (e.g., acrylonitrile butadiene styrene), polycarbonates, and polysulphones. 
         [0057]    Moreover, portions of the housing  301  can be sealed. In accordance with one particular embodiment, the motor  407  is within the sealed portion of the housing  301 . In accordance with another embodiment, seals  413 ,  414 , and  415 , such as o-rings, which are provided to create a sealed portion around the motor  407  such that the surgical tool  300  can be sterilized without damaging the motor  407 . In a more particular embodiment, a single o-ring  413  is provided between the distal end  417  of the motor  407  and the motor shaft  411 , while a double o-ring seal provided by o-rings  414  and  415  are provided proximate to the proximal end  420  of the motor  407 . 
         [0058]    According to one particular embodiment, the torque provided by the output shaft to an implant can be limited, and more particularly selectable. According to one embodiment, the torque output by the tool can be limited by an electrical system wherein the current provided to the motor is controlled and may be selectable by the user. In such an embodiment, a microprocessor can be electrically coupled to the motor and battery to control the current to the motor. According to an alternative embodiment, a mechanical torque limiter can be coupled to the motor shaft to limit the torque. In one such embodiment, the torque limiter can include the use of bearings and a clutch which disengages an input shaft from an output shaft if a certain torque is exceeded. 
         [0059]    Referring now to particular portions of the surgical tool  300 ,  FIG. 5  includes a perspective view of a portion of the surgical tool including the counter-torque sleeve and the bayonet portion in accordance with an embodiment. Generally, the counter-torque sleeve  501  includes a proximal end  506  and a distal end  504 . Moreover, the counter-torque sleeve  501  includes an opening  503  adjacent to the distal end  504  and configured to engage a portion of an implant. The counter-torque sleeve  501  can be coupled, more particularly directly connected to the bayonet portion  509  through the opening  507 . In accordance with a particular embodiment, the counter-torque sleeve  501  is directly connected to the bayonet portion  509  such that the ring portion  505  adjacent to the proximal end  506  of the counter-torque sleeve  501  engages the inner surface of the bayonet portion  509  and fixably attaches the two components. Additionally, a nut  513  having threads along the inner surface can be coupled to the distal end  506  of the counter-torque sleeve  501  and directly connect the counter-torque sleeve  501  with the bayonet portion  509 . Moreover, a lock ring  515  can be inserted within the bayonet portion  509  to facilitate coupling of the bayonet  509  and counter-torque sleeve  501  with the housing of the tool. 
         [0060]    In accordance with one embodiment, the bayonet portion  509  can further include a decoupling structure to release the bayonet portion  509  from the housing of the tool. In one particular embodiment, the bayonet portion  509  includes a release tab  511  directly connected to the bayonet portion  509  and configured to be depressed and facilitate removal of the bayonet portion  509  from the housing. 
         [0061]    As illustrated, the counter-torque sleeve  501  includes the opening  503  adjacent to the distal end  504  and configured to engage an implant. In accordance with one embodiment, the counter-torque sleeve  501  includes a head portion  520  shaped to include channels  521  and  523  that are configured to engage an implant. In a particular embodiment, the channels  521  and  523  are particularly designed to engage an implanted rod. In an alternative embodiment, the counter-torque sleeve  501  can include a pin extending from the head portion  520  configured to engage the implant and lock the position of the counter-torque sleeve  501  relative to the implant. In another particular embodiment, the head portion  520  can include more than one pin, such as two pins, that may be oriented on opposite sides of the head portion  520  and configured to engage the implant. Still, in accordance with another embodiment, the head portion  520  can be a conformable construct. For example, a conformable construction can include an array of pins disposed within the head portion  520 , such that each of the pins are axially movable along the length of the counter-torque sleeve  501  and upon engagement with an implant, some of the pins are moved axially, while others are remain unmoved and couple with the engagement. 
         [0062]    Generally, the counter-torque sleeve  501  can be freely rotatable around the longitudinal axis defined by the length. Rotational freedom facilitates initial engagement of the head portion  520  with an implant. In one embodiment, the counter-torque sleeve  501  is freely rotatable around the longitudinal axis by an angle of at least about 20°. In accordance with another embodiment, the angle of rotation can be greater, such as at least about 30°, at least about 45°, or even at least about 60°. In one particular embodiment, the counter-torque sleeve  501  is freely rotatable around the longitudinal axis by an angle of not greater than about 360°, not greater than about 180°, or even not greater than about 90° to facilitate engagement with the implant. 
         [0063]    Generally, the counter-torque sleeve  501  has a length  529  defined between the proximal end  506  and the distal end  504  of at least about 15 cm. In accordance with another embodiment, the length  529  of the counter-torque sleeve  501  can be greater, such as at least about 18 cm, such as at least about 20 cm, or even at least about 22 cm. Still, however, in accordance with another embodiment, the length  529  of the counter-torque sleeve  501  is generally not greater than about 40 cm, such as not greater than about 30 cm, or even not greater than about 25 cm. In accordance with one particular embodiment, the counter-torque sleeve  501  has a length  529  within a range between about 20 cm and about 25 cm. 
         [0064]    Additionally, the counter-torque sleeve  501  typically has a diameter  525  along its mid-length that is greater than a diameter of the output shaft such that the output shaft can extend through the interior of the counter-torque sleeve  501  and the counter-torque sleeve  501  can slidably engage the output shaft and portions of the implant. As such, in one particular embodiment, the counter-torque sleeve  501  has a diameter  525  of at least about 8 mm. In another embodiment, the diameter  525  is greater, such as at least about 9 mm, or even at least about 10 mm. In accordance with one particular embodiment, the diameter  525  of the counter-torque sleeve  501  is not greater than about 15 mm, such as not greater than about 12 mm. As such, in one more particular embodiment, the diameter  525  of the counter-torque sleeve  501  is within a range between about 10 mm and about 12 mm. 
         [0065]    Still, it should be noted that while the illustrated embodiments describe the arrangement of the output shaft within the counter-torque sleeve  501 , in certain alternative embodiments, the counter-torque sleeve  501  is located within the output shaft. In such embodiments the output shaft is external to the counter-torque sleeve  501 , and the counter-torque sleeve  501  is disposed within the interior of the output shaft, and configured to engage portion of the implant. For example, in one particular embodiment, the implant can include a nut with a screw extending through it, wherein the counter-torque sleeve  501  is configured to engage the head of the screw, while the output shaft has a greater diameter, slideably engages over the counter-torque sleeve  501  and is configured to engage the nut. Accordingly, for such embodiments, the diameter of the counter-torque sleeve  501  can be less than described above. 
         [0066]    In another embodiment, the counter-torque sleeve  501  can include a viewing port  527  along its length  529 . In particular, the viewing port  527  can include an opening or transparent portion whereby the user can view the underlying output shaft contained within the interior of the counter-torque sleeve  501 . More particularly, the viewing port  527  can be aligned with a similar structure (i.e., another viewing port) within the output shaft thereby allowing the user to view contents within the output shaft. In accordance with one particular embodiment, the tool can be used to sever break-off portions of set screws and, accordingly, the viewing port  527  allows the user to confirm separation of the break-off portion as well as identify the number of break-off portions contained within the output shaft. 
         [0067]    Generally, the viewing port extends for a portion of the length of the counter-torque sleeve  501 . In one embodiment, the viewing port extends for a length of at least about 10% of the total length  529  of the counter-torque sleeve. In another embodiment, the viewing port extends for a length of at least about 25%, such as at least about 50%, or at least 75% of the total length  529  of the counter-torque sleeve  501 . In one particular embodiment, the viewing port  527  can extend for substantially the entire length  529  of the counter-torque sleeve  501 . 
         [0068]    Additionally, the viewing port  527 , or alternatively a portion of the counter-torque sleeve  501  can include indicia suitable for counting the number of contents therein. In the particular context of head portions removed from set screws, assuming all of the head portions have an equal length, indicia can be provided along the length of the viewing port  527  or along the length of the counter-torque sleeve  501  that facilitate counting of the head portions contained within. 
         [0069]    As will be described in later embodiments, the counter-torque sleeve  501  is capable of axially translating along the length  529 . In particular, some axial translation of the counter-torque sleeve  501  is required for operation of the tool. The particulars of this configuration and operation will be described in later embodiments. 
         [0070]      FIG. 6  includes a perspective view of portions of the output shaft and inner coupler of the tool in accordance with an embodiment. As illustrated,  FIG. 6  includes an output shaft  601 , an inner coupling portion  611 , and a coupler  613 . As illustrated, the portion of the output shaft  601  adjacent to the proximal end  607  can slidably engage the interior surface of the collar  610  of the inner coupling portion  611 . In particular, the inner coupling portion  611  includes an opening  617  for receiving the coupling device  613 . In particular, the coupling device  613  includes an upper portion  614  having an opening  616  and a biasing member  615  connected thereto. In accordance with a particular embodiment, the opening  616  is configured to engage the end of the motor shaft as will be illustrated in further embodiments. Moreover, a pin  619  is configured to be received within an opening  621  and engage the biasing member  615  of the coupling device  613  thereby operably connecting the coupler  613  and the inner coupling portion  611 . 
         [0071]    In particular reference to the output shaft  601 , the output shaft  601  includes a proximal end  607  and a distal end  603  opposite the proximal end  607 . Moreover, the output shaft  601  includes an opening  605  configured to engage an implant. In accordance with a particular embodiment, the opening  605  is configured to engage a head portion of a set screw, wherein the head portion is intended to be broken off or sheared from the bottom portion of the bone screw. 
         [0072]    Generally, the output shaft  601  has a length  609  that is particularly designed to facilitate surgical procedures, notably a length suitable to minimize tool entrance into the body and avoid contamination of the surgical site while still having a suitable length for providing significant tactile feedback required for performing skilled surgical procedures. As such, in accordance with one embodiment, the output shaft  601  has a length  609  of at least about 10 cm. In one embodiment, the output shaft  601  has a length  609  of at least about 15 cm, such as at least about 18 cm, or even at least about 20 cm. In another embodiment, the length  609  of the output shaft  601  is not greater than about 40 cm. Still, the length  609  of the output shaft  601  may be further limited, such as not greater than about 35 cm, or not greater than about 30 cm. As such, in one particular embodiment, the output shaft  601  has a length  609  within a range between about 20 cm and about 30 cm. The output shaft  601  further includes a viewing port  621  having the same characteristics as the viewing port described in accordance with  FIG. 5 . 
         [0073]    Generally, the output shaft  601  has a diameter  623  measured along the mid-region between the proximal end  607  and the distal end  603  that is less than the diameter of the counter-torque sleeve. In one embodiment, the output shaft  601  has a diameter  623  of at least about 3 mm. In another embodiment, the diameter  623  is greater, such as at least about 4 mm, at least about 5 mm, or even at least about 6 mm. Typically, however, the diameter  623  of the output shaft  601  is limited such that it is not greater than about 12 mm. As such, in one particular embodiment, the output shaft  601  has a diameter  623  within a range between about 6 mm and about 10 mm. 
         [0074]    As previously described, in some embodiments, the output shaft  601  can have a diameter that is greater than the diameter of the counter-torque sleeve, because in such embodiments the counter-torque sleeve is configured to be disposed within the output shaft  601 . As such, in these embodiments, the diameter of the output shaft can be greater, such as greater than about 10 mm, greater than about 20 mm, or even greater than about 30 mm. Generally, in accordance with such embodiments, the diameter of the output shaft is within a range between about 10 mm and about 40 mm, and more particularly within a range between 10 mm and about 30 mm. 
         [0075]    Referring to  FIG. 7 , a partial cross-sectional illustration of the inner coupling portion  611  is illustrated for further clarity in accordance with an embodiment. As illustrated, the coupling device  613  is engaged within a slotted opening of the inner coupling portion  611 . Generally, the pin  619  is configured to engage the biasing member  615  such that the coupler  613  is held within the coupling portion  611  until the user presses and releases the pin  619  from the biasing member. The coupler  613 , and more particularly the opening  701 , is designed to be of a size to prevent captured portions of an implant from falling into the tool during use or into the surgical field when the output shaft  601  is removed from the tool. 
         [0076]      FIG. 8  includes a perspective view of a portion of the surgical tool in accordance with an embodiment.  FIG. 8  illustrates a portion of the housing  809  and more particularly the sleeve portion  307  previously illustrated in  FIG. 3 . The sleeve portion  307  includes an outer sleeve  801 , which further includes flanges  807  configured to engaged the lock ring  515  of the bayonet portion  509  previously illustrated in  FIG. 5 . Moreover,  FIG. 8  further illustrates a distal end of the motor shaft  803  extending from the sleeve portion  307 . In accordance with one embodiment, it is this distal end of the motor shaft  803  which is configured to engage the opening  701  within the coupling device  613  and thus the inner coupling portion  611  previously illustrated in  FIGS. 6 and 7 . 
         [0077]    Referring to  FIG. 9 , an exploded view of particular components within the sleeve portion of the surgical tool is illustrated in accordance with an embodiment. As illustrated, the outer sleeve portion  801  can include an inner sleeve portion  901  configured to slidably engage within the outer sleeve  801 . Additionally, washers  903  and  907  can be disposed on either side of a biasing washer  905  and disposed within the outer sleeve  801 . In particular, the washers  903  and  907  and the biasing washer can be disposed at the distal end of the outer sleeve adjacent the flanges  807  and biased against the lip  902  of the inner sleeve  901 . 
         [0078]    In accordance with a particular embodiment, the surgical tool includes a hex drive gear output  909  selectively coupleable to the motor shaft  911 , which in turn is selectively coupleable to a spline driver  913 . According to a particular embodiment, the hex drive output gear includes an opening  915  configured to receive the distal end  917  of the motor shaft  911 . In accordance with a particular embodiment, the distal end  917  of the motor shaft  911  extends through the opening  915  of the hex drive output gear  909  and is configured to engage the coupling device  613  illustrated in  FIG. 6 . The spline driver  913  includes splines  918 ,  919 ,  920 ,  921 ,  922 , and  923 , ( 918 - 923 ) and in accordance with an embodiment, a portion of the splines  918 - 923  are configured to couple to portions of the motor shaft  911 . In accordance with a particular embodiment, the splines  921 ,  922 , and  923 , are configured to fixably attach to portions  924 ,  925 , and  926  of the motor shaft  911 . According to another embodiment, the splines  918 ,  919 , and  920 , are not fixably coupled to the motor shaft and are flexible portions which can flex radially inside the inner sleeve  901 . Such a configuration facilitates selective coupling and decoupling of the motor shaft  911  from the output shaft by axial movement of the outer sleeve  801  and inner sleeve  901  relative to the remainder of the housing. 
         [0079]    Referring to  FIG. 10 , a perspective view of the spline driver, motor shaft, and hex drive output gear are illustrated in accordance with one embodiment. In particular,  FIG. 10  illustrates the combination of the hex drive output gear  909  coupled with the motor shaft  911  and further coupled with the spline driver  913 . As illustrated, the distal end  1015  of the motor shaft  911  extends through the opening  1001  of the hex drive output gear  909 . In accordance with a particular embodiment, the spline driver  913  includes splines  918  and  919  that include portions  1011  and  1012  extending radially outward from the respective splines  918  and  919 . The portions  1011  and  1012  are configured to engage a channel within the inner sleeve  901 , allowing the splines  918  and  919  to radially expand and clutch portions of the hex drive output gear  909 . The coupling of splines  918  and  919  with portions of the hex drive output gear  909  facilitates coupling the motor shaft  911  with the hex drive output gear  909  and as a result coupling the motor shaft  911  with the output shaft. 
         [0080]      FIGS. 11 and 12  more clearly illustrate the clutching interaction between the spline driver and the hex drive output gear. Referring to  FIG. 11 , a partial cross-sectional illustration of the spline driver  913 , motor shaft  911 , and hex drive output gear  909  within the inner sleeve  901  is illustrated. In particular, as illustrated, the spline drive  913  is contained within the inner sleeve portion  901  such that the splines  918  and  919  are radially compressed. According to one particular embodiment, portions  1011  and  1012  engage the side walls of the inner sleeve portion  901  and radially compress the spline portions  918  and  919  thereby decoupling spline portions  918  and  919  from the lip portion  1101  of the hex drive output gear  909 . 
         [0081]    Referring now to  FIG. 12 , a partial cross-sectional illustration of portions of components including the spline driver  913 , motor shaft  911 , and hex drive output gear  909  are illustrated within the inner sleeve portion. Notably, the inner sleeve portion  901  has been moved forward axially in the direction  1203  with respect to the spline driver  913 , motor shaft  911 , and hex drive output gear  909 . Accordingly, in moving the inner sleeve portion  901  forward axially, the splines  918  and  919 , and more particularly the portions  1011  and  1012  of the splines  918  and  919  engage a channel  1201  within the inner surface of the inner sleeve portion  901 . The engagement of portions  1011  and  1012  within the channel  1201  facilitate outward radial movement of the splines  918  and  919  and coupling of the splines  918  and  919  with the lip portion  1101  of the hex drive output gear  909 . The engagement of the splines  918  and  919  with the hex drive output gear  909  facilitates coupling of the motor shaft  911  with the hex drive output gear  909  which in turn facilitates coupling of the motor shaft  911  with the output shaft of the surgical tool. Accordingly, selective coupling and decoupling of the motor shaft  911  with the output shaft is facilitated by axial movement of the inner sleeve portion  901  from a first position to a second position as illustrated in  FIGS. 11 and 12  respectively. 
         [0082]    Referring briefly again to  FIG. 4 , coupling of the motor shaft  411  to the output shaft  315  can be accomplished by axial movement of the sleeve portion  307  in the direction  430 . In particular, for torque to be applied to the implant, some axial movement of the sleeve portion  307  is completed to couple the motor shaft  411  and the output shaft  315 . Such a mechanism ensures that torque cannot be applied to the implant without sufficient engagement of the counter-torque sleeve  313  with the implant, thus avoiding potential for injury to the patient or the surgeon. According to a particular embodiment, the entire allowable movement of the sleeve portion  307 , the bayonet portion  309 , and the counter-torque sleeve  313  in the axial direction  430  is the axial travel distance  431 . In accordance with a particular embodiment, the axial travel distance  431  is generally at least about 10 millimeters, such as at least about 20 millimeters, such as at least about 25 millimeters. In another embodiment, the axial travel distance  431  is limited such that it is not greater than about 50 millimeters, such as not greater than about 40 millimeters. As such, in one particular embodiment, the axial travel distance  431  is within a range between about 15 millimeters and about 30 millimeters. 
         [0083]    More particularly, there is a distance  432  that is a fraction of the axial travel distance  431  that is sufficient to selectively couple the splines  918  and  919  within the channel  1201  and thereby couple the motor shaft  411  and output shaft  315 . According to one embodiment, the distance  432  is not greater than about 95% of the axial travel distance  431 . In another embodiment, the distance  432  is not greater than about 90% or even not greater than about 80% of the axial travel distance  431 . Still, in another particular embodiment, the distance  432  sufficient to engage the splines  918  and  919  within the channel  1201  is at least about 50% of the total axial travel distance  431 . The differences between the distance  432  and the axial travel distance  431  facilitates partial engagement of the counter-torque sleeve  313  with an implant without requiring the sleeve portion  307  and subsequently the counter-torque sleeve  313  to travel the entire axial travel distance  431  before engagement of the motor shaft  411  with the output shaft  315 . Thus, the counter-torque sleeve  313  may not need to extend the entire axial travel distance  431  before the operator can apply rotational force to the implant via the output shaft  315 . This may be particularly suitable in the context of performing surgeries where space is limited and full contact with an implant may not be possible. 
         [0084]    While embodiments herein have demonstrated a selective coupling between the motor shaft and the output shaft using a clutching mechanism having radial splines, it will be appreciated that other mechanisms are possible. For example, turning to  FIGS. 13 and 14 , alternative clutching mechanisms are illustrated suitable for coupling and decoupling the motor shaft and the output shaft. As illustrated,  FIG. 13  includes a face clutch having an opening  1301  configured to couple with a portion of the motor shaft. Additionally, the face clutch includes a series of teeth  1303  disposed along a surface  1305  configured to engage teeth of a corresponding face clutch illustrated in  FIG. 14 . Accordingly, as illustrated in  FIG. 14 , the face clutch  1400  includes an opening  1401  configured to engage a portion of the motor shaft, as well as teeth  1403  disposed along the surface  1405  configured to engage the teeth  1303  of the corresponding face clutch  1300 . Like the clutching mechanism utilizing the spline driver described previously, the face clutch mechanisms illustrated in  FIGS. 13 and 14  are axially displaced until movement of the sleeve portion is sufficient for the faces to engage, wherein the teeth of each surface engage each other and the motor shaft is coupled with the output shaft. 
         [0085]    While particular embodiments herein have described mechanical means to selectively couple and decouple the motor shaft from the output shaft, it will be appreciated that electronic devices can be used. For example, in one embodiment, an electronic switch can be used to electrically disengage the motor from the battery until the sleeve portion travels a sufficient distance. As such, according to one embodiment before the sleeve portion is moved in an axial direction, the motor is electrically disengaged from the power source. After movement of the sleeve portion a sufficient axial distance, an electronic switch can be engaged or disengaged such that the motor is electrically coupled to the power source thereby allowing the motor shaft to turn the output shaft. Accordingly, in such embodiments using an electronic device for selective coupling and decoupling, the output shaft and motor shaft may be permanently connected. 
         [0086]    Referring to  FIG. 15 , a cross-sectional illustration of a trigger in accordance with one embodiment is provided. As illustrated, a trigger  1500  is provided that includes a moveable trigger portion  1501  biased against a base portion  1507  by a biasing member  1502 . As illustrated, the moveable trigger portion  1501  and base portion  1507  are pivotally connected at a pivot point  1503 , such that the base portion  1507  can be fixably attached to the housing of the handle and the moveable trigger portion  1501  can pivot around the pivot point  1503  upon actuation by a user. In accordance with another embodiment, the trigger  1500  can include a magnetic trigger, including magnetic components, such as a reed switch. 
         [0087]      FIGS. 16 ,  17 A, and  17 B illustrate particular embodiments of the battery pack. Referring to  FIG. 16 , a perspective view of a battery pack is illustrated in accordance with one embodiment. As illustrated, the battery pack  1600  includes a housing  1601  for containing the battery or batteries, and a cap portion  1603  coupled at one end of the housing  1601 . According to a particular embodiment, the battery pack  1600  further includes a clip  1607  to fixably engage the battery pack  1600  within the housing. Moreover, in accordance with another embodiment, the battery pack  1600  includes a passage  1605  extending through the length of the battery pack  1600 . 
         [0088]    Referring to  FIG. 17A , a cross-sectional illustration of a portion of the battery pack is illustrated in accordance with one embodiment. According to one embodiment, the battery pack  1600  has a generally triangular shape having generally three corners, wherein batteries  1701 ,  1702 , and  1703  can be disposed within the three corners of the battery pack  1600 . Moreover, in one embodiment, the passage  1605  extends along the longitudinal axis of the battery pack  1600  and between the batteries  1701 - 1703  such that the batteries  1701 - 1703  are arranged around the passage  1605 . While the embodiment of  FIG. 17A  illustrated a battery pack  1600  having multiple battery cells  1701 - 1703 , in accordance with another embodiment, the battery pack  1600  can include a single battery cell, such that the interior of the battery pack is one single power cell. In particular, with regard to embodiments using one battery, a passage may still be provided through the battery. 
         [0089]    According to one embodiment, the passage  1605  has a diameter  1705  of at least about 1 mm. In another embodiment, the diameter  1705  of the passage  1605  is greater, such as at least about 1.5 mm or at least about 2 mm. In another embodiment, the passage  1605  has a diameter  1705  that is not greater than about 10 mm, such as not greater than about 8 mm, or not greater than about 5 mm. In one particular embodiment, the passage  1605  has a diameter  1705  within a range between 2 mm and about 5 mm. 
         [0090]    In accordance with another embodiment, the passage  1605  has an electrically insulating sheath  1707 . The electrically insulating sheath  1707  can include a dielectric material. According to one embodiment, suitable dielectric materials can include ceramics or polymers. In a more particular embodiment, the electrically insulating sheath  1707  includes a polymer. In accordance with another embodiment, the electrically insulating sheath can be made of a polymer material, including for example, polyurethane materials, polyolefin materials, polyether materials, silicone materials, or a combination thereof. Further, the polyolefin materials can include polypropylene, polyethylene, halogenated polyolefin, fluoropolyolefin, or a combination thereof. The polyether materials can include polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyaryletherketone (PAEK), or a combination thereof. 
         [0091]      FIG. 17B  includes a perspective view of another battery pack in accordance with an embodiment. As illustrated, the battery pack  1750  can include a rear cap  1751  coupled to a housing  1753 , which can be further coupled to a front cap  1761 . The rear cap  1751  can be coupled to the housing  1753  via a snap-fit connection, interference fit connection, or can include fasteners. Likewise, the front cap  1761  can be coupled to the housing  1753  via a snap-fit connection, interference fit connection, or through the use of fasteners. 
         [0092]    The housing  1753  can include an engagement structure  1755  disposed on an upper surface and coupled to the body of the housing  1753 . The engagement structure  1755  can be a user-operable device for releasing the battery pack  1750  from the housing  301  of the tool  300 . According to one design, the engagement structure  1755  can be a cantilevered structure that is connected to the housing  1753  at one end and unsupported at the opposite end, facilitating depression of the unsupported end of the engagement structure  1755  toward the housing for release of the battery pack  1750  from the housing. 
         [0093]    The housing  1753  can include a central opening  1754  extending longitudinally along the length of the housing  1753  for containing the power cells  1757  (i.e., batteries) therein. Additionally, the housing  1753  can include pads  1756  and  1759  corresponding to the each of the power cells  1757  and configured to suitable locate and secure the power cells  1757  within the housing  1753 . 
         [0094]    The battery pack of  FIG. 17B  includes three power cells  1757 . The power cells  1757  may also be in a stacked orientation along the longitudinal axis with a first power cell  1757  aligned with and stacked at an end of a second power cell  1757 . In one embodiment, the battery pack includes a total of nine power cells  1757  with three levels each having three power cells  1757 . These stacked power cells  1757  form a cross-sectional triangular arrangement similar to the arrangement of  FIG. 17B . In one specific embodiment, the power cells are 1.2 V nickel-cadmium cells. 
         [0095]    According to one embodiment, the battery pack  1750  can further include charging members  1763  and  1764 . The charging members  1763  and  1764  can provide a suitable electrical connection between the power cells  1757  and an external power source for charging and/or recharging of the power cells  1757 . The charging members  1763  and  1764  can be positioned within a portion of the housing  1753  and a portion of the front cap  1761 . In particular designs, at least a portion of the charging members  1763  and  1764 , such as an electrical contact portion is accessible from an opening within the front cap  1761 . In such embodiments, the battery pack  1750  can be removed from the tool and engaged with an external power source via the electrical contact portion of the charging members  1763  and  1764  to recharge the power cells  1757 . 
         [0096]    In accordance with one particular embodiment, the tool can be used without the battery pack  1750  and incorporate a direct connection via an electrical cable to a remote power source via electrical contact  1780  illustrated in  FIG. 8 . This design facilitates use of the tool with an alternative power source. For example, if the power cells  1757  are drained or fail, the tool  300  can be directly connected to an external power source for operation of the tool  300 . Operation of the tool from the battery pack  1750  or an external power source provides a failsafe operation mode if one particular power source of the tool is unavailable or fails. 
         [0097]    The battery pack  1750  can further include a failsafe switch  1765  that is electrically coupled to the power cells  1757 . The failsafe switch  1765  is operable between an on state and an off state. In the on state, the failsafe switch  1765  can allow current to flow between the power cells  1757  and the motor  407  within the tool  300 . In the off state, the failsafe switch interrupts current flow between the power cells  1757  and the motor  407  to avoid inadvertent motor  407  operation during an off state condition of the failsafe switch  1765 . 
         [0098]    In certain designs, the failsafe switch  1765  can include a switch that is sensitive to a threshold temperature, such that the failsafe switch  1765  can be a thermal cutoff. For example, the failsafe switch  1765  can be in an on state until the battery pack  1750 , and thus the failsafe switch  1765 , is exposed to a temperature exceeding (i.e., either greater than or less than) a particular threshold temperature, in which case, the failsafe switch  1765  changes conditions to an off state. According to one particular embodiment, the failsafe switch  1765  can operate in an on state (i.e., allowing current flow) until the temperature of the battery pack  1750  is greater than a threshold temperature and then turns to an off state interrupting current flow to the motor  407 , and otherwise electrically decoupling the power cells  1757  from the motor  407 . 
         [0099]    For one certain failsafe switch  1765 , the threshold temperature can be a temperature of at least about 65° C., such as on the order of at least about 68° C., at least about 70° C., at least about 84° C., and particularly within a range between about 68° C. and about 84° C. 
         [0100]    Certain designs of the failsafe switch  1765  can use a thermal fuse, in which after the threshold temperature is exceeded the electrical connection between the power cells  1757  and the motor  407  is permanently disconnected. In such designs, after the failsafe switch  1765  is changed to an off state, the battery pack  1750  will need to be removed from the tool and a new failsafe switch  1765  (i.e., thermal fuse) installed. 
         [0101]    In other designs, the failsafe switch  1765  can be a thermal switch or thermal reset that can be made of a bimetallic material, in which after the threshold temperature is exceeded the electrical connection between the power cells  1757  and the motor is temporarily severed. The electrical connection can be reset after the temperature within the battery pack  1750  falls below the threshold temperature. In such embodiments using a thermal switch as the failsafe switch  1765 , a user operable switch can also be integrated such that reset operation is not conducted without user operation. That is, when the electrical connection is temporarily disconnected between the power cells  1757  and the motor  407  by the failsafe switch, a user must operate a secondary failsafe switch or reset switch to reset the failsafe switch  1765  to an on state and reestablish an electrical connection between the power cells  1757  and the motor  407 . 
         [0102]    According to one embodiment, the failsafe switch  1765  can be operated at a range of voltages from about 9 V to about 11 V at 25° C., and more particularly over a range of voltages between about 9.5 V and about 10.1 V at 25° C. The failsafe switch  1765  can be operated at a current range of about 0-30 A. 
         [0103]    The passage  1605  may align with a larger passage that extends through the remainder of the tool  300 . The passage  1605  may extend completely through the battery pack  1600 , and the second passage may extend completely through the body of the surgical tool  300 . These aligned passages are arranged to receive a guide wire  399  as illustrated in  FIG. 35 . The guide wire  399  can be threaded through the aligned passages and completely through the length of the tool  300 . The tool  300  may then be precisely aligned relative to the patient through the guide wire  399 . The relative sizes of the overall passage and the guide wire  399  provides for the tool  300  to move along the length of the guide wire  399  during the surgical procedure. The battery pack and tool bodies with aligned passages for use with the guide wire  399  may be used with the tool described above in  FIGS. 1-17B , and may also be used in various other surgical tools including the POWEREASE tapper/driver tool from Medtronic Sofamor and Biologics of Memphis, Tenn. 
         [0104]      FIGS. 18-26  include illustrations of a surgical tool according to another embodiment. In particular, certain components illustrated in  FIGS. 18-26  illustrate a change to the coupling mechanism between the output shaft  315  and the motor  1913 . Notably, the clutching mechanism described in accordance with previous embodiments included certain mechanical mechanism, while the following embodiments utilize certain other components, including for example, an electromechanical mechanism to accomplish coupling between the output shaft  315  and the motor  1913 . 
         [0105]      FIG. 18  includes a perspective view illustration of a surgical tool according to one embodiment. Like the tools described previously, the tool includes a housing  301  having a proximal end  303  and distal end  305 . Additionally, the tool includes a handle portion  311  coupled to the housing  301  and extending in a direction substantially perpendicular to a longitudinal axis of the housing  301 . Moreover, unlike previous embodiments, the tool includes an inner sleeve  1801  having particular surface features that facilitate clutching as will be described in more detail in the following figures. 
         [0106]      FIG. 19  includes a perspective view of a portion of the tool in accordance with an embodiment. As illustrated, the tool includes a housing portion  809  proximal to the distal end of the tool and an inner sleeve  1801  coupled to and extending from the housing portion  809 . The inner sleeve  1801  can be formed with the housing portion  809  such that the two components form a single, monolithic piece. Alternatively, the inner sleeve  1801  can be coupled to the housing portion  809  via fasteners, interference fit coupling, snap-fit coupling mechanism, or the like 
         [0107]    As further illustrated in  FIG. 19 , the tool includes a trigger  1901  having a shaft portion  1902  that is configured to be engaged within an opening  1904  of the handle portion  311 , such that the trigger  1901  is coupled to the housing portion  809 . The trigger mechanism can include other components as illustrated, notably a shaft seal  1903  configured to engage and directly contact the shaft portion  1902  within the handle portion  311 . The trigger mechanism further includes a bearing member  1905  configured to engage the shaft portion  1902  within the handle portion  311  and facilitate translation of the shaft portion  1902  within the trigger mechanism during operation of the trigger by a user. A bracket  1907  can be used to secure and couple the bearing member  1905 , shaft seal  1903 , and trigger shaft  1902  together within the handle portion  311 . 
         [0108]    The bracket  1907  can be coupled to a trigger mounting  1910  that facilitates coupling of the bracket  1907 , bearing member  1905 , and shaft seal  1903  to the interior of the handle portion  311 . The bracket  1907  can be biased against the trigger mounting  1910  via biasing members  1908  and  1909  that facilitate biasing the position of the trigger  1901  into a position until the trigger is depressed by a user. Accordingly, biasing members assure that the trigger is maintained at a starting position (i.e., off position) until the mechanism is acted upon by a force, such as by a users finger. 
         [0109]    Notably, the trigger mechanism includes a trigger switch  1911  that is coupled to the trigger mounting  1910 . The trigger switch  1911  can be a high-temperature switching component, capable of withstanding temperatures akin to autoclaving environments. The trigger switch  1911  can be electrically connected to the motor  1913 , such that upon movement of the trigger  1901  from a first position (i.e., starting position) to a second position (i.e., a depressed position), the shaft portion  1902  is translated laterally into the interior of the handle portion  311  and the trigger switch  1911  is actuated. According to one embodiment, actuation of the trigger switch  1911  by the trigger  1901  changes the state of the trigger switch  1911  from an off state to an on state. In more particular instances, at the on state, a closed circuit can be formed between the motor  1913  and the trigger switch  1911  such that current is flowing between the two components, and the motor  1913  is operable. When the motor  1913  is operable, it is capable of rotating the output shaft  315 . According to one embodiment, when the trigger switch  1911  is at an on state, if another condition is met with regard to the clutching assembly, the motor  1913  can be operable. 
         [0110]      FIG. 20  illustrates a perspective view of a portion of a surgical tool in accordance with an embodiment. In particular,  FIG. 20  illustrates the housing portion  809  and inner sleeve  1801  extending axially from the housing portion  809  in a direction of the longitudinal axis  2020 . As illustrated, the inner sleeve  1801  can include a surface feature, such a recess  2001  that extends generally along the longitudinal axis  2020  and the exterior surface of the inner sleeve  1801 . In certain embodiments, the inner sleeve  1801  can include more than one recess, such as a series of recesses that extend axially along the longitudinal axis  2020  of the inner sleeve  1801 . Particular embodiments utilize at least about 2 recesses and not greater than about 5 recesses depending upon the size of the inner sleeve  1801 . 
         [0111]    The recess  2001  can have an asymmetrical shape comprising a first surface  2011  extending axially along a direction of the longitudinal axis  2020 , and comprising a second surface  2009  extending substantially along the same direction as the longitudinal axis  2020 , and further including a tapered surface  2010  extending at an angle with respect to the surface  2009 . The recess  2001 , and particularly the tapered surface  2010 , can define a minor recess area  2021  near the proximal end  2022  of the inner sleeve  1801  within the recess  2001 . The asymmetrical shape of the recess  2001  facilitates suitable engagement of an outer sleeve on the inner sleeve  1801 , and more particularly, engagement of features within the interior of the outer sleeve in the recess  2001  such that upon movement of the outer sleeve with respect to the inner sleeve  1801 , the features within the interior of the outer sleeve engage certain surfaces of the recess  2001  as will be described in more detail herein. 
         [0112]    The inner sleeve  1801  further includes an island  2007  disposed within the recess  2001  and extending from a distal end  2023  in a direction of the longitudinal axis  2020  along the inner sleeve  1801 . As illustrated, the island  2007  extends for a discrete distance along the exterior surface of the inner sleeve  1801  within the recess  2001 . The island  2007  can have a generally rectangular contour, and in particular, includes a tapered surface  2030  that facilitates movement of features within the interior of the outer sleeve about either side of the island  2007  within the recess  2001 . 
         [0113]    As illustrated in  FIG. 20 , the island  2007  that separates two regions of the recess  2001  and therein defines two different grooves within the recess  2001 , notably an inactive groove  2003  and an active groove  2005 . The inactive groove  2003  and active groove  2005  generally extend axially within the recess  2001  along a direction of the longitudinal axis  2020  of the inner sleeve  1801  and are laterally spaced apart from each other. In particular, the inactive groove  2003  is defined as the region between surfaces  2009  and  2010 , and the island  2007 . The inactive groove  2003  facilitates initial coupling between an outer sleeve and the inner sleeve  1801  and engages features on the interior surface of the outer sleeve when the tool is in an inactive state, that is, when the motor  1913  is not operable and incapable of rotating the output shaft  315 . The active groove  2005  is defined as the region between the surface  2011  and the island  2007  and is configured to engage surface features within the interior of the outer sleeve when the tool is in an active state, that is, when the motor  1913  is operable and capable of rotating the output shaft  315 . 
         [0114]    As further illustrated, the recess  2001  includes an opening  2013  extending axially along the direction of the longitudinal axis  2020  from a distal end  2023  of the inner sleeve  1801 . In particular, the opening  2013  is disposed within the active groove  2005  at the distal end  2023  of the inner sleeve  1801 . The opening  2013  facilitates engagement of a portion of an actuator arm therein, such that upon movement of an outer sleeve from a first position to a second position with respect to the inner sleeve  1801 , the portion of the actuator arm within the opening  2013  is engaged by surface features within the interior of the outer sleeve. 
         [0115]    Features of the actuator arm are more clearly illustrated in  FIGS. 21-24 .  FIG. 21  includes a perspective view illustrating a portion of a surgical tool including certain components within the tool in accordance with an embodiment.  FIG. 21  includes an illustration of particular components designed to fit within an interior space  2102  at the distal end of the inner sleeve  1801  according to one embodiment. Some of the components include a seal member  2103 , a cap member  2105  housing the seal member  2108 , and an actuator arm  2106  configured to engage the cap member  2105  within the interior space  2102 . Other components include a motor shaft portion  803  including a base portion  2111 , and a head portion  2112  coupled to the base portion  2111 . The motor shaft portion  803  is configured to be engaged within an opening  2119  of the cap member  2105  and further configured to engage a drive shaft of the motor  1913  through an opening  2123  within the interior space  2102  of the inner sleeve  1801 , such that upon rotation of the drive shaft, the motor shaft portion  803  is rotated. 
         [0116]    The interior space  2102  of the distal end of the inner sleeve  1801  can include fasteners  2101  designed to be threaded into corresponding openings within the interior space  2102  for engagement with and fixation of the motor  1913  within the inner sleeve  1801 . The seal member  2103  can be placed within the interior space  2102  of the inner sleeve  1801  to form a seal between the portion of the inner sleeve housing the motor  1913 , and the portion of the inner sleeve housing the cap member  2105  and other components illustrated in  FIG. 21 . In particular, the seal member  2103  facilitates use of the tool as a surgical tool, capable of being exposed to high temperatures, pressures, and even liquids typically used to sterilize components for use in an operatory. For example, the tool must be able to withstand environments used in autoclaving, a common method of sterilizing surgical tools. Moreover, the seal member  2103  avoids access of bodily fluids typically encountered in surgical procedures from entering the portion of the inner sleeve  1801  housing the motor  1913 . 
         [0117]    The cap member  2105  is configured to be engaged within the interior space  2102  of the inner sleeve  1801  and can be affixed to the inner sleeve  1801  via fasteners  2107  and  2109  that can be engaged within openings  2108  and  2110  within the cap member  2105 , and in turn further engage openings  2120  and  2121  within the inner sleeve  1801 . Notably, the cap member  2105  houses the actuator arm  2106 , and according to the illustrated embodiment, a portion of the actuator arm  2106  extends from the cap member  2105  in a direction substantially perpendicular to the longitudinal axis of the inner sleeve  1801 . The orientation between actuator arm  2106  and cap member  2105  facilitates protrusion of a portion of the actuator arm into the opening  2013  within the active groove  2005  of the inner sleeve  1801 . 
         [0118]    The motor shaft portion  803  includes a base portion  2111  coupled to the head portion  2112  configured to be engaged with the cap member  2105  within the inner sleeve  1801 . In particular, the motor shaft portion  803  is configured to be engaged with the cap member  2105  and a portion of the motor  1913  through the opening  2119  within the cap member  2105 . The base portion  2111  and head portion  2112  can be a single, monolithic member, or alternatively, can be two discrete components that are coupled together. Moreover, as further illustrated and according to one embodiment, the motor shaft portion  803  can be coupled to a drive shaft of the motor  1913  via a fastener  2130 , such as a set screw. 
         [0119]      FIG. 22  includes a perspective view of a cap member and certain components within the cap member in accordance with an embodiment. The cap member  2105  can include a seal  2217  configured to be engaged within the opening  2119  suitable for sealing the connection between the output shaft of the motor  1913  and the motor shaft portion  803 . Additionally, the cap member  2105  includes a ball member  2221  configured to be engaged within an outer surface of the cap member  2105  to facilitate releasable engagement with a collar (See  FIG. 26 ). Notably, the ball member  2221  can be biased into a position by a biasing member  2219  to facilitate releasable engagement between the cap member  2105  and the collar. 
         [0120]    As illustrated, the cap member  2105  can include an opening  2207  disposed at an outer surface and at an orientation that is substantially perpendicular to the longitudinal axis of the inner sleeve  1801 . The actuator arm  2106  is configured to engage and extend through the opening  2207  of the cap member  2105 , and can include a head portion  2202  attached to a shaft portion  2203 . The head portion  2202  can include a fin  2201  (e.g., a protrusion) extending from the head portion  2202  that is configured to be engaged within the opening  2013  of the recess  2001  within the inner sleeve  1801 . The shaft member  2203  is further positioned within the opening  2207  of the cap member  2105  such that the shaft is disposed within the interior of the cap member  2105 . The shaft portion is configured to engage a seal member  2206  that can be contained within the interior of the cap member  2105  such that contaminates do not penetrate the interior of the cap member and also such that the tool is suitable for sterilization. 
         [0121]    A biasing member  2209  can be provided around the end of the shaft portion  2203  of the actuator arm  2106  such that a biasing force is provided to the actuator arm  2106  and the actuator arm  2106  is resiliently biased to a particular orientation as illustrated in  FIG. 22 . Notably, the orientation can include positioning of the fin  2201  in an upright position such that it protrudes into the opening  2013  within the recess  2001  of the inner sleeve  1801 . This arrangement is more clearly illustrated in  FIG. 23 , which provides a perspective view of a portion of the tool including the inner sleeve  1801  and cap member  2105  as assembled in accordance within an embodiment is illustrated. As shown, the cap member  2105  is assembled within the interior space at the distal end of the inner sleeve  1801 , and more particularly, the fin  2201  of the actuator arm  2106  is positioned within the opening  2013  of the recess  2001  at a biased, upright position. 
         [0122]    Referring again to  FIG. 22 , the cap member  2105  can further include a clutching switch  2211  disposed within the interior of the cap member  2105 . In particular, the clutching switch  2211  can be disposed within a location  2250  such that it is disposed against an interior wall of the cap member  2105  and positioned proximate to the end of the shaft portion  2203  of the actuator arm  2106 . The clutching switch  2211  can be a high temperature switching component, capable of withstanding temperatures and pressures akin to autoclaving environments. The clutching switch  2211  can include an actuator  2215  such that upon movement of the actuator from a first position to a second position the clutching switch  2211  changes states, such as from an off state to an on state, or more particularly from an open circuit to a closed circuit. As illustrated and according to one embodiment, the actuator  2215  can be a button that is depressed. Other actuators for changing the state of the clutching switch can be used, such as for example levers, dials, and the like. The clutching switch  2211  can include wires  2213  electrically connecting the switch to the motor  1913 . 
         [0123]    During operation of the tool, the actuator arm  2106 , and more particularly, the fin  2201  can be moved between a first position and a second position. Notably, movement of the fin  2201  can include rotation of the actuator arm  2106  about the axis  2265  in the direction  2260  such that the shaft portion  2203  of the actuator arm  2106  is rotated within the cap member  2105 . Rotation of the shaft portion  2203  can result in a tapered region  2205  of the shaft portion  2203  engaging the actuator  2215  of the clutching switch  2211 . As such, movement of the actuator arm  2106  between the first position and the second position results in a change of state of the clutching switch  2211 . For example, according to one embodiment, the clutching switch  2211  can change from an off state to an on state upon movement of the actuator arm  2106  between the first position and the second position. The on state can include the formation of a closed circuit between the motor  1913  and the clutching switch  2211  such that the motor is in an operable state, that is, the motor  1913  is capable of rotating the output shaft  315 . 
         [0124]    The amount of rotation of the shaft portion  2203  is engineered such that the component cannot be accidentally rotated to a degree to cause inadvertent engagement of the actuator  2215 , putting the tool in an operable state, which may be particularly hazardous in the context of surgical procedures. In particular embodiments, the degree of rotation of the shaft portion  2203  of the actuator arm  2106  suitable to engage the actuator  2215  of the clutching switch  2211  is not greater than about 180 degrees. For example, certain designs utilize a degree of rotation of the shaft portion that is not greater than about 160 degrees to engage the actuator arm. In other embodiments, the degree of rotation can be less, for example, not greater than about 90 degrees, and particularly within a range between about 20 degrees and about 90 degrees, and more particularly between about 20 degrees and about 70 degrees. 
         [0125]    As stated previously, the trigger switch  1911  can function in a same or similar manner, that is, forming a closed circuit between the motor  1913  and trigger switch  1911  and thus facilitating operation of the motor  1913  if another condition is met. In particular, the foregoing describes the previously mentioned condition for operation of the motor. Accordingly, when the actuator arm  2106  is rotated to a position sufficient to engage the actuator  2215  of the clutching switch  2211  a closed circuit can be formed between the clutching switch  2211  and motor  1913 . Additionally, the trigger switch  1911  can be actuated by a user such that a closed circuit is formed between the trigger switch  1911  and the motor  1913 . When the foregoing conditions are met, the motor is in an operable state and capable of rotating the output shaft  315 . In particular embodiments, if one of the two switches (i.e., clutching switch  2211  or trigger switch  1911 ) is not actuated such that a closed circuit is not formed between either of the clutching switch  2211  and motor  1913  or trigger switch  1911  and motor  1913 , the motor  1913  can be inoperable, and may not be capable of rotating the output shaft  315 . The foregoing describes an electromechanical clutching mechanism. Such a design may facilitate a smaller, light-weight tool incorporating less components than designs using primarily mechanical clutching mechanisms. 
         [0126]    Referring now to  FIGS. 24-26 , the outer sleeve and associated components, which have been made reference to previously, are described in more detail.  FIG. 24  includes a perspective view of an outer sleeve in accordance with an embodiment. The outer sleeve  2401  is configured to fit over the inner sleeve  1801  such that inner sleeve  1801  is engaged within an interior space  2406  of the outer sleeve  2401 . As illustrated, the outer sleeve  2401  can have a substantially cylindrical shape and include a rim  2409  extending around the circumference of the outer sleeve  2401  abutting the proximal end of the outer sleeve  2401 . The outer sleeve  2401  can further include a head portion  2403  at a distal end of the outer sleeve  2401 , wherein the head portion  2403  includes openings  2405  radially space apart around the circumference and configured to facilitate coupling of the inner sleeve  1801  and the inner coupling portion  611 . 
         [0127]    The outer sleeve  2401  can further includes rails  2407  extending axially in the direction of the longitudinal axis  2020  within the interior surface of the outer sleeve  2401 . According to one embodiment, the rails  2407  can aid initial engagement of the outer sleeve  2401  with the inner sleeve  1801 , such that the outer sleeve  2401  can slideably engaged the exterior surface of the inner sleeve  1801  by engaging the rails  2407  within the recess  2001 . More particularly, the rails  2407  may be used to engage the inactive groove  2003  of the recess  2001  for initial coupling between the inner sleeve  1801  and the outer sleeve  2401 . In certain embodiments, the outer sleeve  2401  can include a plurality of rails, such as not less than about 3 or even not less than about 4 groups of rails, extending along the interior surface of the outer sleeve  2401  for engagement with complementary recesses within the inner sleeve  1801 . 
         [0128]      FIG. 25  includes another perspective view of the outer sleeve of  FIG. 24  in accordance with an embodiment. Notably,  FIG. 25  illustrates a protrusion  2501  that extends axially along an interior surface of the outer sleeve  2401  in a direction along the longitudinal axis  2020 , and further extends from the interior surface of the outer sleeve  2401  into the interior space  2406  of the outer sleeve  2401 . The protrusion  2501  can be connected to one of the rails  2407 , such that it extends from an end of a rail for a length along the longitudinal axis  2020 . Moreover, in certain embodiments using a plurality of rails, the outer sleeve  2401  can include a plurality of protrusions, wherein each of the protrusions of the plurality of protrusions is attached to a corresponding set of rails. 
         [0129]    In certain instances, the protrusion  2501  can be a single protrusion, or alternatively, there can be more than one protrusion. For example, in one embodiment, the protrusion  2501  can include two protrusions. In particular embodiments, one protrusion can have a length that is greater than a length of the other protrusion, wherein length is measured by the distance extending in a direction of the longitudinal axis of the outer sleeve  2401 . In such instances, the shorter protrusion can be configured to engaged the island  2007  when the protrusions are engaged within the inactive groove  2003  and engaged the surface  2011  when the protrusions are engaged within the active groove  2005 . Moreover, in certain instances using two protrusions of different lengths, one of the protrusion (shorter) can be configured to engage the fin  2201  of the actuator arm  2106  while the other protrusion (longer) can be a torque-bearing protrusion bearing the majority of torque forces against the surface  2011 . 
         [0130]    The rails and protrusion  2501  are particularly integrated such that the protrusions can be more closely spaced together relative to each other in a lateral direction than the rails  2407  are spaced together relative to each other. In fact, certain embodiments utilize protrusions that are abutting one another in a side-by-side orientation. This design facilitates the formation of a corner, otherwise a lateral offset, at the connection between the protrusion  2501  and the rails  2407 . In more particular designs, the protrusion  2501  consists of a short protrusion and a long protrusion and the rails  2407  comprise two rail elements extending longitudinally along the inner surface of the outer sleeve  2401  parallel to each other. One of the protrusions (e.g., the short protrusion) can extend along the same axis of one of the rail elements, while the other protrusion (e.g., long protrusion) is abutting the other protrusion, and thus is laterally offset from the axis of the other rail element to form a corner at the connection between said particular rail element and said (long) protrusion. As such, during actuation of the outer sleeve relative  2401  to the inner sleeve  1801 , once the protrusion(s)  2501  are engaged within the active groove  2005 , the outer sleeve  2401  can be translated toward the distal end  305  of the tool for a distance until the corner engages the island  2007  thus stopping the degree of translational motion and maintaining the outer sleeve  2401  on the inner sleeve  1801 . 
         [0131]    As illustrated in  FIG. 25 , the outer sleeve  2401  further includes an opening  2503  in the head portion  2403  for engagement of the output shaft  315  therein. Moreover, the head portion  2403  includes openings  2507  and  2508  for engagement of fasteners therein for affixing the inner coupling portion  611  to the head portion  2403 . 
         [0132]      FIG. 26  includes a perspective view of the outer sleeve and associated components for use in the tool in accordance with an embodiment. As illustrated, the outer sleeve  2401  can include a collar  2601  configured to be disposed within the interior space  2406  of the outer sleeve  2401 . According to one embodiment, the collar  2601  can have a generally cylindrical shape such that it can be fitted within the head portion  2403  of the outer sleeve  2401 . Notably, the collar  2601  can include a series of projections  2607  extending from the exterior surface of the collar along the direction of the longitudinal axis  2020  of the outer sleeve  2401 . The projections  2607  are configured to be engaged within complementary features within the inner coupling portion  611 . In particular embodiments, the complementary features can be tabs  2621  disposed within the inner surface of the inner coupling portion  611 . 
         [0133]    The collar  2601  can further include teeth  2603  extending from a proximal end of the collar along the direction of the longitudinal axis  2020 . The teeth  2603  can be radially spaced apart along the circumference of the collar  2601 . Additionally, in certain embodiments, the teeth  2603  can have surface features suitable for engaging portions of the inner sleeve  1801 . For example, according to the illustrated embodiment, the teeth  2603  can have complementary surface features, such as depressions  2605  for engaging portions of the inner sleeve, such as the ball member  2221  disposed along the outer surface of the cap member  2105 . The ball member  2221  can be biased into a position such that upon engagement with one of the teeth  2603  of the collar  2601 , the ball member  2221  is urged to rest within the complementary depression until enough force is exerted on the collar  2601  to release the collar  2601  and cap member  2501  from each other. 
         [0134]    The outer sleeve  2401  can further include a biasing member  2609  configured to be disposed within the interior space  2406  of the outer sleeve  2401 . In particular, the biasing member  2609  can contact an interior surface of the outer sleeve  2401  at the distal end within the head portion  2403 . The biasing member  2609  biases the translational motion between the outer sleeve  2401  and inner sleeve  1801  utilized for engagement of the actuator arm  2106  that operates the clutching mechanism. In particular, the biasing member  2106  biases the two components (i.e., the outer sleeve  2401  and inner sleeve  1801 ) into an initial unengaged state (i.e., the clutching switch is disengaged), which the user can overcome via a rotational movement of the outer sleeve  2401  followed by a translational movement of the outer sleeve  2401  toward the distal end  305  of the tool to affect engagement of the actuator arm  2106  and thus the clutching switch  2211 . 
         [0135]    As further illustrated in  FIG. 26 , a locking member  2613  can be coupled to the outer sleeve  2401 . In particular, the locking member  2613  is configured to releasably engage the counter-torque sleeve  313  from a coupling portion  2631 . The locking member  2613  includes a central opening  2619  in the body having a particular shape to engage the proximal end of the counter-torque sleeve  313  therein. The locking member  2613  can be coupled to the exterior surface of the outer sleeve  2401  at the head portion  2403  and contained within the interior of the coupling portion  2631 . In accordance with one embodiment, the locking member  2613  can be coupled with grooves along the interior surface of the coupling portion  2631  and may be a “floating” component, wherein it is not fixably locked into a position, and rather, compressed between the head portion  2403  and interior surface of the coupling portion  2631 . 
         [0136]    According to one embodiment, the locking member  2613  includes a projection  2617  extending from the locking member body and configured to extend from an opening  2623  within the inner coupling member  2611 . The extension of the projection  2617  allows for releasable engagement of the counter-torque sleeve  313 , as the projection  2617  can be depressed to facilitate release of the counter-torque sleeve  313  from the coupling portion  2631 . As will be appreciated, biasing members  2615  bias the position of the projection  2617  such that it extends through the opening  2623  until engaged by a user. 
         [0137]    The coupling portion  2631  can be coupled to the outer sleeve  2401  at the head portion  2403 , such that the coupling portion  2631  extends over substantially the entire surface of the head portion  2403  covering the openings  2405 . The coupling portion  2631  can be fixably attached to the head portion  2403  of the outer sleeve  2401  via fasteners  2610  and  2611 , which may be threaded from the interior of the outer sleeve  2401 . 
         [0138]      FIGS. 27A and 27B  illustrate actuation of the clutching switch  2211 , and more particularly, the actuation of the fin  2201  of the actuator arm  2106  during operation of the outer sleeve  2401 .  FIG. 27A  includes a cross-sectional illustration of a portion of the tool including the outer sleeve and actuator arm in a disengaged state according to an embodiment. As illustrated, the outer sleeve  2401  is overlying the inner sleeve  1801 . The outer sleeve  2401  includes protrusion  2501  extending from the rail  2407  along the inner surface of the outer sleeve  2401 . In an initial and unengaged state of the tool, the rail  2407  is not in the active groove  2005  and the biasing member  2609  is configured to act against an inner surface of the head portion  2403  against the collar  2601  to bias the outer sleeve  2401  in a back and neutral state. In order to move the actuator arm  2106 , a user may move the outer sleeve  2401  by first rotating the outer sleeve  2401  in a direction  2701  until the rail  2407  abuts the first surface  2011  of the recess  2001  and is engaged in the active groove  2005 . Such an action also places the protrusion  2501  within the active groove  2005  of the recess such that it is positioned directly behind the fin  2201  of the actuator arm  2106  as illustrate in  FIG. 27A . 
         [0139]    Referring now to  FIG. 27B , a cross-sectional illustration of a portion of the tool including the outer sleeve and actuator arm in an engaged state is provided according to an embodiment. As illustrated in  FIG. 27B , after sufficiently rotating the outer sleeve  2401  to the position illustrated in  FIG. 27A , the user can translate the outer sleeve  2401  relative the inner sleeve  1801  in the direction  2801  toward the distal end  305  of the tool. The translation of the outer sleeve  2401  facilitates translation of the protrusion  2501  to the position illustrated in  FIG. 27B , wherein the protrusion  2501  is engaged with the fin  2201  and the actuator arm  2201  is rotated to a second position as illustrated. As described herein, rotation of the actuator arm  2201  to the second position facilitates changing the state of the clutching switch  2211  from an off position to an on position, which in turn can turn the motor  407  to an on position allowing the user to operate the tool. As will be appreciated, to disengage the motor, the outer sleeve can be returned to its initial unengaged position by translating the outer sleeve  2401  in the direction opposite the direction  2801  and rotating the outer sleeve  2401  in a direction opposite the direction  2701 . 
         [0140]    According to certain embodiments, the rotational movement suitable for engaging the clutching mechanism can be not greater than about 90 degrees, such as not greater than about 70 degrees, or even for example, not greater than about 60 degrees, 50 degrees, or 30 degrees. Particular embodiments utilize a rotational motion within a range between about 5 degrees and about 90 degrees, such as within a range between about 5 degrees and about 60 degrees, in certain instances between about 5 degrees and about 30 degrees, and more particularly within a range between about 5 degrees and about 25 degrees. 
         [0141]    Moreover, the degree of translational movement suitable for engaging the actuator arm  2201  can be considered the engagement distance and can generally be not greater than about 20% of the total length of the inner sleeve  1801 . In other embodiments, the engagement distance is less, such as not greater than about 15%, such as not greater than about 10%, and even not greater than about 8%. Particular embodiments utilize an engagement distance of at least about 2%, or even at least about 4%. For example, the engagement distance can be within a range between about 3% and about 20%, and more particularly within a range between about 3% and about 10% of the total length of the inner sleeve  1801 . 
         [0142]    The foregoing has made reference to use of actuators and engagement of mechanical components for changing the state of the tool, particularly from a state in which the output shaft may not be rotated to a state wherein the output shaft can be rotated. Still, other embodiments can utilize a different type or different combination of components to achieve such results. For example, embodiments herein can include a tool that utilizes magnetic devices, electronic devices, and a combination thereof for operation of the tool. The magnetic devices described herein can be used in conjunction with any other devices (e.g., switches, actuators, etc.) previously described herein. Alternatively, the magnetic devices described herein can be used without the use of other such devices described in the other embodiments. 
         [0143]      FIG. 28  includes a cross-sectional illustration of a portion of a tool including a trigger according to an embodiment. As illustrated, the tool includes a trigger  3001  coupled to the housing  301  of the tool, and particularly connected at the handle  311  of the housing  301  in a manner as illustrated in  FIGS. 8 and 15 . The trigger  3001  can include a moveable trigger portion  3003  that is pivotably coupled to the housing  301  at a pivot point for rocker-type movement of the trigger by a user. Additionally, the trigger  3001  can include a biasing member  3005  for biasing the moveable trigger portion  3003  in a position as illustrated until the trigger  3001  is forcibly urged by a user to be moved in a direction  3020  as indicated. 
         [0144]    The trigger  3001  can also include a trigger switch  3010  that can include certain components for operation of the tool. According to an embodiment, the trigger switch  3010  can include a magnet  3007  that can be coupled to the moveable trigger portion  3003 . In particular, the magnet  3007  can be embedded within the moveable trigger portion  3003 , such that the magnet  3007  can be moved with the moveable trigger portion  3003 . According to one particular embodiment, the trigger switch  3010  can be a reed switch mechanism. 
         [0145]    The trigger switch  3010  can further include a sensor  3009  coupled to the housing  301 . In particular instances, the sensor  3009  can be directly coupled to an interior portion of the housing  301 , and more particularly, directly connected to and even embedded within an interior wall  3014  of the tool. The sensor can include a magnetically sensitive material, such that it can be magnetically coupled and magnetically decoupled when the magnet  3007  is at a certain distance from the sensor  3009 . The sensor  3009  further includes an electrical connection  3012 , such as a wire, for electrical coupling of the sensor  3009  to a circuit board  3013  that can be contained and sealed within the housing  301 . 
         [0146]    During operation, a user can move the moveable trigger portion  3003  of the trigger  3001  in a direction  3020  as illustrated from a first position, where it may be naturally biased (i.e., a resting position), to a second position such that the trigger  3001  is in a depressed state. In the resting position, the magnet  3007  can be at a sufficient distance that it is magnetically decoupled from the sensor  3009 . As such, the switch  3010  can be in an off state. In moving the moveable trigger portion  3003  to the second position in the direction  3020 , the magnet  3007  can be moved to a position that is at a sufficient distance to magnetically couple the magnetically sensitive material contained within the sensor  3009  and the magnet  3007 . When the moveable trigger portion  3003  is moved sufficiently to magnetically coupled the magnet  3007  and the sensor  3009 , the trigger switch  3010  can be changed from the off state to an on state. As will be appreciated, when the moveable trigger portion  3003  is moved sufficiently, in a direction opposite the direction  3020 , such as when a user releases pressure from the moveable trigger portion  3003 , the magnet  3007  can be magnetically decoupled from the sensor  3009  and the trigger switch  3010  can be changed from an on state to an off state. 
         [0147]    In such conditions wherein the trigger switch  3010  is in an on state, the motor can be in an operable mode, such that the output shaft  315  can be rotated. In particular instances, when the trigger switch  3010  is in an on state, an electrical circuit can be formed between the trigger switch  3010  and the motor  407 . Formation of an electrical circuit between the trigger switch  3010  and the motor  407  can be a condition sufficient for operation of the tool, and particularly the rotation of the output shaft  315 . In particular embodiments, multiple conditions may be needed for operation of the tool. That is, actuation of the trigger  3001  to turn the trigger switch  3010  to an on state may be one of a plurality of conditions that may need to be met before the tool is in an operable state and the output shaft  315  can be rotated. For example, a clutching switch may also be actuated to a proper state (i.e., an on state) in conjunction with the operation of the trigger switch  3010  for operation of the tool as described herein. 
         [0148]      FIG. 29  includes a perspective view illustration of a cross-section of a portion of a tool including the outer sleeve and associated components in accordance with an embodiment. In particular, certain of the foregoing embodiments have described clutching mechanisms for operation of the tool, such as an actuator arm  2106  and clutching switch  2211 . According to other designs, the tool can utilize other mechanisms for operation, and more particularly, clutching of the tool from an off state to and on state using magnetic switching devices. 
         [0149]      FIG. 29  illustrates a portion of the tool including the motor  407  and a motor shaft  411  that extends from the motor  407  as described herein. The design of the tool further includes a motor cover  3105  overlying and surrounding the motor  407 . The motor cover  3105  can include seals, such that the motor  407  is contained within a sealed environment, which may be particularly suitable for sterilization (e.g., autoclaving) of the tool. The motor cover  3105  and the motor  407  can be connected to each other via a threaded connection  3107  as illustrated. Other suitable fastening mechanism may be employed. 
         [0150]    The tool can further include an inner sleeve  1801  coupled to the housing  301  and an outer sleeve  2401  coupled to the housing  301 , wherein the inner sleeve  1801  and the outer sleeve  2401  can include those features as discussed herein according to other embodiments. The inner sleeve  1801  can be coupled, and more particularly, fastened to the motor cover  3105 , via fasteners  3109  arranged at a distal end of the inner sleeve  1801  and motor cover  3105 . 
         [0151]    A motor housing cap  3108  can be disposed at a distal end of the motor  407  proximate to the motor shaft  411  between the motor  407  and the distal end of the motor cover  3105 . The motor housing cap  3108  is contained within the motor cover  3105  and can include an opening  3115  defined between an interior surface of the motor cover  3105  and an external surface of the motor housing cap  3108 . According to particular embodiments, the opening  3115  can be of sufficient size for a sensor  3103  to be seated therein. 
         [0152]    The tool can further include a switch  3120  within the housing  301 . The switch  3120  can include multiple components, including a sensor  3103  and a magnet  3101  that can be contained within the housing  301  of the tool. In certain designs, the sensor  3103  can be disposed in a position, such that it is spaced apart from the magnet  3103 , for example, within the opening  3114  of the motor housing cap  3108 . The magnet  3101  can be contained within a retaining ring  3111  and coupled to a different portion of the housing  301  displaced at a suitable distance from the sensor  3103 . For example, in some designs, the magnet  3101  and the retaining ring  3111  can be coupled to, and more particularly, directly connected to, an inner surface of the outer sleeve  3401  such that the components are configured to be moveable with the movement of the outer sleeve  2401 . In particular instances, the switch  3120  can be a reed switch for controlling the operation of the motor  407 . 
         [0153]    During operation, the outer sleeve  2401  can be moved from a first position to a second position in a direction  3130 , such that it is translated along the inner sleeve  1801  toward the distal end of the tool in manner described in  FIGS. 27A and 27B . In the first position, the magnet  3101  is sufficiently spaced apart from the sensor  3103 , which contains a magnetically sensitive material, such that the sensor  3103  and the magnet  3101  are magnetically decoupled. When the sensor  3103  and the magnet  3101  are magnetically decoupled, the switch  3120  is in an off state. When the outer sleeve  2401  is moved to a second position and translated in a direction  3130 , the magnet  3101  can be moved to a position sufficiently proximate to the sensor  3103  to magnetically couple the magnet  3101  and the magnetically sensitive material of the sensor  3103 . In such conditions, the switch  3120  can be changed from the off state to an on state. In certain instances, when the switch  3120  is in an on state, the motor  407  can be placed in an operable mode, wherein the motor shaft  411  can be rotated. In the on state, the switch  3120  may be electrically connected to the motor  407  or associated electronics (e.g., a circuit board) controlling the motor  407 . 
         [0154]    It will be appreciated that when the switch  3120  is placed in an on state, such a condition may be one of a plurality of conditions that need to be satisfied for operation of the tool. For example, according to certain embodiments, the switch  3120  can be considered a clutching switch, suitable for placing the motor  407  in a ready state, such that in conjunction with the trigger switch  3010  being placed in an on state, the tool can be operated and the output shaft is in a rotateable state (i.e., it can be rotated). 
         [0155]      FIG. 30  includes a perspective view of a tool according to one embodiment. In particular, the tool  3200  includes a particular release mechanism  3201  to facilitate removal of the coupling portion  2631  from the housing  301 , and more particularly from the outer sleeve  2401 . Such removal can facilitate sterilization of the components of the tool and simple assembly and/or disassembly. As further illustrated and described herein, the tool can further be disassembled, by operation of the projection  2617  which actuates the locking member  2613  for releasable engagement of the counter-torque sleeve  313  from the coupling portion  2631 . This may be completed before removal of the coupling portion  2631  from the housing  301 . 
         [0156]      FIGS. 31-32  include cross-sectional illustrations of portions of the tool including the release mechanism. In particular,  FIGS. 31-32  demonstrate the operation of a release mechanism for selective attachment of the coupling portion  2631  with the housing  301  of the tool. 
         [0157]      FIG. 31  includes a cross-sectional illustration of a portion of the tool including the release mechanism in accordance with an embodiment.  FIG. 31  illustrates the coupling portion  2631  attached to the housing  301  of the tool body in a latched position such that the coupling portion  2631  is affixed and locked in position relative to the housing  301 . As illustrated, the release mechanism  3201  can include a button  3203  that can be actuated (e.g., depressed) and moved relative to the housing  301  of the tool to move a portion of a moveable member  3301  contained within the housing  301 , which in turn can facilitate removal of the coupling portion  2631  from the outer sleeve  2401 . In particular, the moveable member  3301  coupled to the button  3203  can include an arm  3305  having a flange  3309  affixed to an end of the arm  3305  for engagement with a protrusion  3307  at a surface the inner sleeve  1801 . The moveable member  3301  can further include an arm  3311  extending from the body of the moveable member  3301  in a direction opposite the arm  3305 . The moveable member  3301  can be pivotable around a pivot point  3303  during operation of the button  3203  that results in actuation of the moveable members  3301  and  3302 . 
         [0158]    As illustrated, the tool can include more than one release mechanism, a first release mechanism  3201  on a first side of the housing  301  and a second release mechanism  3202  on an opposite side of the housing  301 . This design can avoid accidental decoupling of the coupling portion  2631  from the housing  301 , such that both of the release mechanisms  3201  and  3202  must be actuated in order to remove the coupling portion  2631  from the housing. It will be appreciated that description with regard to the operation of the release mechanism  3201  will be the same as the operation of the release mechanism  3202 . 
         [0159]      FIG. 31  illustrates the coupling portion  2631  in a latched position wherein the coupling portion  2631  is fixably attached to the housing by virtue of an engagement between the flange  3309  of the arm  3305  and the protrusion  3307  of the inner sleeve  1801 . The latched position is suitable when the tool is in use such that the components are fixably attached to each other. 
         [0160]    Turning to  FIG. 32 , the coupling portion  2631  is illustrated in a released position. In certain designs, to change the coupling portion from the latched position (illustrated in  FIG. 31 ) to the released position, the outer sleeve  2401  can be changed from the active groove  2005  to the inactive groove  2003 . Such a change can facilitate fuller movement of the outer sleeve  2401  on the inner sleeve  1801 . The changing of position of the outer sleeve  2401  can include rotation of the outer sleeve  2401  in a counter-clockwise direction  3401  as illustrated (as held by a user with the distal end of the tool facing away from the user) and can further include translation of the outer sleeve  2401  toward the distal end of the tool in the direction  3403  as illustrated. 
         [0161]    Upon placement of the outer sleeve  2401  relative to the inner sleeve  1801  as illustrated in  FIG. 32 , the release mechanisms  3201  and  3202  can be actuated to change the positions of the associated moveable members  3301  and  3302 , respectively. In particular, a user can depress the button  3203 , which can contact the arm  3311  of the moveable member  3301 , thus displacing the position of the moveable member as it rotates about the pivot point  3303 . The inside surface of the button  3203  can contact the arm  3311  and move it in a direction  3402  away from the inner surface of the button  3203  and urging the moveable member  3301  to pivot around its pivot point  3303  such that the flange  3309  of the arm  3305  is decoupled from the protrusion  3307 . In this state as illustrated in  FIG. 32 , the coupling portion  2631  is in a released position and can be decoupled from the housing  301  by translating the coupling portion  2631  in the direction  3403  while holding the outer sleeve  2401  in the same position. 
         [0162]    As will be appreciated, when reattaching the coupling portion  2631  to the housing  301 , the outer sleeve  2401  can be moved back to the active groove  2005 , such that the coupling portion  2631  can be engaged on the housing  301 . In particular, reattachment of the coupling portion  2631  can include translating the coupling portion  2631  in a direction opposite the direction  3403  until the inner surface of the button  3203  engages the surface of the arm  3305  (the same applies for the other release mechanism  3202 ) and pivots the moveable member  3301  back to the position illustrated in  FIG. 31 , wherein the flange  3309  is engaged with the protrusion  3307 . 
         [0163]    Referring to  FIGS. 33 and 34 , illustrations are provided that demonstrate the use of the surgical tool for removing a head portion of a set screw. Referring to  FIG. 33 , a screw is illustrated that includes a set screw  2801  and a bone screw  2802 . The set screw  2801  includes a cap  2803  and a head portion  2805  attached to the cap  2803 . The bone screw  2802  includes an opening within a head portion configured to engage a rod  2807  therein and fix the position of the screw  2800  relative to the rod  2807  as is typical with rod and anchor systems. As further illustrated in accordance with one embodiment, the output shaft  2809  is engaged with the head portion  2805  of the set screw  1801  such that it is substantially seated around the head portion  2805 . Additionally, the counter-torque sleeve  2811  is configured to extend over the output shaft  2809 , the set screw  2801  including the head portion  2805  and the cap  2803 , such that the counter-torque sleeve  2811  engages the rod  2807  and the head portion of the bone screw  2802 . Notably, the output shaft  2809  and the counter-torque sleeve  2811  engage different portions of the implant. 
         [0164]    Accordingly, the output shaft  2809  is configured to provide a rotational force to the head portion  2805 , while the counter-torque sleeve  2811  is fixably coupled with the rod  2807  such that it is not free to rotate. The coupling configuration at the implant in conjunction with the output shaft  2809  and the counter-torque sleeve  2811  being coupled at the housing creates a design wherein the rotational forces provided by the output shaft  2809  are balanced by an opposing force of the counter-torque sleeve  2811  at the implant since the two are coupled through the housing. 
         [0165]    Referring to  FIG. 34  after applying a sufficient rotational force, that is a torsional breaking force to the head portion  2805  via the output shaft  2809  the head portion  2805  can be broken or separated from the cap  2803 . Notably during breaking of the head portion  2805  from the cap  2803  the counter-torque sleeve  2811  is fixably engaged with the rod  2807  such that it does not rotate, however rotational forces imparted to the screw by the output shaft  2809  on the head portion  2805  are balanced by the counter-torque sleeve  2811  through the housing. Accordingly, during engagement with the bone screw  2802  and rod  2807 , the counter-torque sleeve  2811  is configured to provide a substantially opposite torsional force to the torsional breaking force applied by the output shaft  2809  and substantially fix the position of the bone screw  2802  and rod  2807  relative to the housing of the tool during separating the head portion  2805  from the cap  2803 . As such, upon breaking of the head portion  2805  from the cap  2803  the transfer of a sudden release of stored energy to the patient is minimized because of the coupling between the output shaft  2809  and the counter-torque sleeve  2811  with the housing. As a result, jarring of the patient is minimized making the procedure safer and also reducing the likelihood of damage to the implant. Moreover, given the mechanical advantage of using a power tool, the effort expended by the surgeon is substantially less, allowing for a more efficient surgery. 
         [0166]    Embodiments provided herein represent a departure from the state of the art. In particular reference to breaking head portions of set screws, the state of the art still includes the use of manual tools often resulting in jarring of the patient and doctor. By contrast, the surgical tool provided herein includes a combination of features making such procedures more efficient and safer. The combination of features include, among other things, use of an output shaft and a counter-torque sleeve coupled to a housing such that the rotational forces generated in the output shaft are balanced in the housing by the counter-torque sleeve. Moreover, other features of the present embodiments include selective coupling and decoupling of the motor shaft with the output shaft, use of a particular axial travel distance, use of electrical power, and certain coupling and clutching mechanisms between the counter-torque sleeve as well as the output shaft thereby facilitating a power tool capable of reducing potential injuries to patients during surgery and making surgeries more efficient and less vigorous on surgeons. 
         [0167]    In accordance with a first aspect of the present disclosure a surgical tool for removing a portion of an implant within a human is provided that includes a housing, a motor contained within the housing and coupled to the housing, and an output shaft having a distal end and a proximal end opposite the distal end, wherein the proximal end is coupled to the motor and the distal end has an opening configured to rotateably engage an implant. According to the first aspect, the surgical tool further includes a counter-torque sleeve extending around the output shaft having a proximal end and a distal end opposite the proximal end, wherein the proximal end is coupled to the housing and the distal end configured to couple to the implant relative to the counter-torque sleeve such that upon a rotational force to the implant, the forces transmitted by the output shaft and the counter-torque sleeve are balanced by the coupling of the output shaft and counter-torque sleeve through the housing. 
         [0168]    According to one embodiment of the first aspect, the housing comprises an outer sleeve and the counter-torque sleeve is coupled to the outer sleeve. In a particular embodiment, the outer sleeve is slideably engageable with an inner sleeve. In another embodiment of the first aspect, the counter-torque sleeve is slideably engageable over the output shaft. In a more particular embodiment, the counter-torque sleeve is moveable between a first axial position and a second axial position, wherein in the first axial position the output shaft is decoupled from the motor. 
         [0169]    In accordance with another embodiment of the first aspect, the implant includes a set screw having a breakable head portion and the output shaft is configured to fit over the head portion. In a particular embodiment, the implant further comprises a rod engaged within a portion of the bone screw and the counter-torque sleeve is configured to engage a portion of the rod. 
         [0170]    According to a second aspect of the present disclosure, a tool for use during surgery includes a housing, a motor disposed within the housing and connected to the housing, and an output shaft having a proximal end and a distal end opposite the proximal end, wherein the proximal end is coupled to the motor and the distal end having an opening to engage an implant within a patient. The tool of the second aspect further includes a counter-torque sleeve having a proximal end and a distal end opposite the proximal end, the counter-torque sleeve coupled to the housing and overlying the output shaft, wherein the distal end includes an opening to engage the implant. 
         [0171]    According to one embodiment of the second aspect, the output shaft has an opening at the distal end configured to engage an implant. In a particular embodiment, the output shaft has an opening at the distal end configured to fit over a head portion of a set screw. In a more particular embodiment, the opening at the distal end of the counter-torque sleeve is configured to engage a portion of a rod extending through the head portion of the bone screw. 
         [0172]    In accordance with another embodiment of the second aspect, the counter-torque sleeve is slideably engageable with the output shaft along a longitudinal axis defined by a length of the counter-torque sleeve over the output shaft. In another alternative embodiment, the distal end of the counter-torque sleeve comprises a conformable head configured to engage an implant. In a more particular alternative embodiment, the conformable head comprises an array of pins, each of the pins in the array moveable between a first axial position and a second axial position to engage an implant. 
         [0173]    In one embodiment of the second aspect, the counter-torque sleeve is rotateable around a longitudinal axis defined by a length of the counter-torque sleeve. In another particular embodiment, the counter-torque sleeve is rotateable by not less than about 20°. In a still more particular embodiment, the counter-torque sleeve is rotateable by not greater than about 90°. 
         [0174]    According to another embodiment, the tool further includes a viewing port within the counter-torque sleeve and the output shaft. In another embodiment, the tool further includes a torque limiter coupled to the output shaft within the housing. As such, in a more particular embodiment, the torque limiter comprises a microprocessor electrically coupled to the motor. 
         [0175]    In accordance with another embodiment of the second aspect, the surgical tool further comprising a battery pack disposed within the housing and having a passage extending through the battery pack. In a more particular embodiment, the battery pack is abutting a proximal end of the housing. In still another particular embodiment, the battery pack comprises multiple power cells. In a still more particular embodiment, the multiple power cells are arranged around the passage. In another embodiment, the battery pack has a longitudinal axis and a substantially triangular cross-sectional contour including three corners, wherein the power cells are disposed within the corners of the battery pack and the passage extends substantially along the longitudinal axis. 
         [0176]    In one certain embodiment of the second aspect, the passage has a generally circular cross-sectional contour including a diameter of at least about 1 mm. In a more particular embodiment, the diameter of the passage is not greater than about 10 mm. In accordance with one embodiment of the second aspect, the tool further includes a sealed compartment within the housing. In a particular embodiment, the sealed compartment includes a portion of the housing containing a battery pack and the motor. 
         [0177]    In a certain embodiment of the second aspect, the output shaft has a length of at least about 10 cm. In one embodiment, the output shaft has a length of not greater than about 40 cm. In another embodiment, the output shaft has a diameter of at least about 3 mm. In still yet another embodiment, the counter-torque sleeve has a diameter that is greater than the diameter of the output shaft. In another particular embodiment, the counter-torque sleeve has a length of at least about 15 cm. As such, in a more particular embodiment, the counter-torque sleeve has a length of not greater than about 40 cm. 
         [0178]    According to a third aspect of the present disclosure a tool for use during surgery includes a housing, a motor disposed within the housing, a battery disposed within the housing and coupled to the motor, and an output shaft having a proximal end and a distal end opposite the proximal end, wherein the proximal end is coupled to the motor. The tool further includes a counter-torque sleeve coupled to the housing having a proximal end and a distal end opposite the proximal end, wherein the counter-torque sleeve is slideably engageable over the output shaft between a first position and a second position, wherein at the first position of the counter-torque sleeve the output shaft is unpowered, and at the second position of the counter-torque sleeve, the output shaft is powered. As such, in one particular embodiment, in the first position of the counter-torque sleeve, the output shaft is decoupled from the motor and thus the output shaft is unpowered. In still another embodiment, at the first position of the counter-torque sleeve, the motor is disengaged from the battery and thus the output shaft is unpowered. 
         [0179]    According to one embodiment of the third aspect, the counter-torque sleeve has an axial travel distance and the distance between the first position and the second position is not less than about 50% of the axial travel distance. In another embodiment, the distance between the first position and the second position is not greater than about 90% of the axial travel distance. 
         [0180]    In accordance with another embodiment, the tool further includes a trigger moveable between a first position and a second position, wherein at the first position the motor is at an off state and at the second position the motor is at an on state. In a particular embodiment, at the first position of the counter-torque sleeve the motor is at an off state independent of the position of the trigger. In another particular embodiment, the trigger further includes a failsafe switch disposed on the trigger and moveable between an on position and an off position. 
         [0181]    In accordance with one embodiment of the third aspect, the tool further includes a trigger coupled to the handle and operable with a first hand of an operator, and a failsafe trigger coupled to the housing, wherein the failsafe trigger is simultaneously operable with the trigger with the first hand of the operator. As such, in another embodiment, the tool further includes a failsafe switch coupled to the housing and moveable between an off position and an on position, wherein the off position is configured to electrically disengage the motor from the battery. In still another embodiment, the tool further includes a failsafe switch coupled to the housing and moveable between an off state and an on state, wherein the off state is configured to disengage the output shaft from the motor. 
         [0182]    In another embodiment of the third aspect, the tool further comprising an audible indicator, optical indicator or both coupled to the housing, wherein the audible indicator or optical indicator has a first state corresponding to the first position of the counter-torque sleeve, and a second state corresponding to the second position of the counter-torque sleeve. 
         [0183]    According to another aspect of the present disclosure, a tool for use during surgery includes a motor contained within a housing and connected to the housing and an output shaft having a proximal end coupled to the motor and a distal end opposite the proximal end configured to engage a head of a set screw. The tool further includes a counter-torque sleeve coupled to the housing at a proximal end and having a distal end opposite the proximal end configured to fixably engage a portion of an implant adjacent to the head of the screw, and wherein the output shaft is rotated around an axis defined by a length of the output shaft until the head of the screw is separated from a body while the counter-torque sleeve is fixed relative to the implant and head of the screw. In one embodiment, the motor is a DC electric motor. 
         [0184]    According to another aspect, a tool for use during surgery includes a motor contained within a housing and connected to the housing, an effector coupled to the motor and configured to provide rotational force to an implant, and a reaction arm coupled to the housing and the implant, the reaction arm configured to react to the rotational force applied to the implant by the effector. In one embodiment, the reaction arm includes a counter-torque sleeve having a proximal end connected to the housing and a distal end configured to engage the implant. In another embodiment, the effector is configured to be coupled to a first portion of an implant and the reaction arm is configured to be coupled to a second portion of the implant, wherein the first portion and the second portion are different portions, and the reaction arm substantially fixes the location of the second portion of the implant relative to the position of the housing. In a particular embodiment, the effector comprises a distal end having an opening configured to engage a set screw, wherein the effector is configured to apply a torsional breaking force to the set screw to separate a head portion of the set screw from a cap portion. In another particular embodiment, the reaction arm is configured to engage a bone screw and rod coupled to the set screw, wherein during engagement with the bone screw and rod, the reaction arm is configured to provide a substantially opposite torsional force to the torsional breaking force applied by the effector and substantially fix the position of the bone screw and rod relative to the housing during separating the head portion from the cap portion. 
         [0185]    In an alternative aspect, a surgical tool for removing a portion of an implant within a human includes a housing, a motor contained within the housing and coupled to the housing, and an output shaft having a distal end and a proximal end opposite the distal end, wherein the proximal end is coupled to the motor and the distal end has an opening configured to rotateably engage an implant. The tool further includes a counter-torque sleeve adjacent to the output shaft having a proximal end and a distal end opposite the proximal end, wherein the proximal end is coupled to the housing and the distal end configured to couple to the implant relative to the counter-torque sleeve such that upon a rotational force to the implant the forces transmitted by the output shaft and the counter-torque sleeve are balanced by the coupling of the output shaft and counter-torque sleeve through the housing. The tool further includes an outer sleeve, wherein the counter-torque sleeve is coupled to the outer sleeve. Notably, the outer sleeve is moveable between a first position and a second position, wherein at the first position the motor is off, and the output shaft is not rotateable. At the second position the motor is on, and the output shaft is rotateable. More particularly, at the first position a switch within the housing is at an off state, and at the second position, a switch within the housing is at an on state. 
         [0186]    The tool can further include an inner sleeve coupled to the housing and configured to slideably engage an interior surface of the outer sleeve. The inner sleeve extends axially from a proximal end of a handle and can include an actuator arm within the interior that is engageable with a portion of the outer sleeve. As such, in certain instances, moving the outer sleeve from a first position to a second position a portion of the outer sleeve moves the actuator arm from a first position to a second position. Accordingly, in certain embodiments, moving the actuator arm from a first position to a second position changes a state of a switch, wherein the switch is disposed within the inner sleeve. In some embodiments, the switch changes from an open position to a closed position upon moving the actuator arm from a first position to a second position, wherein at the closed position a closed circuit is formed between the switch and the motor. According to one embodiment, the actuator arm is rotated about a longitudinal axis of the actuator arm from the first position to the second position. 
         [0187]    According to another embodiment, the inner sleeve comprises a recess and an opening within the recess for engagement of a portion of the actuating arm therein. The opening can extend axially along a longitudinal axis of the inner sleeve from a distal end of the sleeve. In some cases, the recess comprises an active groove and an inactive groove and the opening is disposed in the active groove of the recess. In more particular instances, a fin of the actuation arm is engaged within the opening at a first position. More particularly, the fin of the actuation arm is biased into a position within the opening via a biasing member in contact with the actuation arm. In other embodiments, a cap is engaged within a distal end of the inner sleeve, and wherein the actuator arm is engaged within the cap. 
         [0188]    According to one embodiment of one aspect, the inner sleeve comprises a recess extending axially along an exterior surface of the sleeve. In some cases, the inner sleeve comprises a series of recesses extending axially along the exterior surface of the sleeve. In more particular examples, the recess comprises an active groove and an inactive groove, wherein the active groove and inactive groove are different grooves laterally spaced apart from each other within the recess. In some instances, the outer sleeve comprises a protrusion extending from an interior surface of the outer sleeve for engaging the active groove and the inactive groove. In more particular embodiments of an aspect, at the first position the protrusion is engaged within the inactive groove and at the second position the protrusion is engaged within the active groove. 
         [0189]    According to another embodiment, the active groove and the inactive groove are separated by a island disposed within the recess between the active groove and inactive groove. For example, island extends axially along a longitudinal axis of the inner sleeve from a distal end of the inner sleeve. In some embodiments, at the second position, the protrusion is abutting the island. Moreover, moving between the first position and the second position includes rotating the outer sleeve with respect to the inner sleeve about a longitudinal axis of the inner sleeve, such as rotating by not greater than about 30 degrees or not greater than about 10 degrees. Additionally, in some cases moving between the first position and the second position further includes translating the outer sleeve in an axial direction with respect to the inner sleeve. For example, translating includes moving the outer sleeve toward the proximal end of the housing relative to the inner sleeve for an engagement distance, wherein the engagement distance is not greater than about 20% or not greater than about 10% of the total length of the inner sleeve. 
         [0190]    According to another aspect, a tool for use during surgery includes a housing, a motor disposed within the housing and connected to the housing, and an output shaft having a proximal end and a distal end opposite the proximal end, wherein the proximal end is coupled to the motor and the distal end having an opening to engage an implant within a patient. The tool further includes a counter-torque sleeve having a proximal end and a distal end opposite the proximal end, the counter-torque sleeve coupled to the housing and overlying the output shaft, wherein the distal end includes an opening to engage the implant. According to one embodiment, the tool includes a trigger coupled to a handle, wherein the handle is coupled to the housing, and the trigger is moveable between a first position and a second position, and moving the trigger between the first and second positions changes the state of a trigger switch between a first state and a second state. Moreover, in certain embodiments, at the second state the trigger switch is at a closed position, and wherein at the closed position a closed circuit is formed between the trigger switch and the motor. 
         [0191]    According to another embodiment, of the above aspect, the tool includes a clutching mechanism for coupling the motor and the output shaft, wherein the clutching mechanism is a electromechanical mechanism. In one case, the tool includes an outer sleeve moveable between a first position and a second position, wherein movement between the first position and the second position engages the clutching mechanism. For example, in certain instances, movement of the outer sleeve between the first position and the second position moves a clutching switch between an off state and an on state, wherein at the on state of the clutching switch a closed circuit is formed between the clutching switch and the motor. In another embodiment, the motor is electrically connected to a trigger switch and a clutching switch, and wherein, the motor is operable between an on state and an off state, wherein at the on state the motor is operable and at the off state the motor is inoperable. For example, at the on state of the motor, the trigger switch is at an on state and the clutching switch is at an on state. And further for example, at the off state of the motor, one of either of the trigger switch and the clutching switch are at an off state. 
         [0192]    The above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments, which fall within the true scope of the present invention. Thus, to the maximum extent allowed by law, the scope of the present invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.