Patent Publication Number: US-2023147047-A1

Title: Attachment for a Powered Surgical Tool

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/736,906, filed on Jan. 8, 2020, which is a continuation of U.S. patent application Ser. No. 15/471,004, filed on Mar. 28, 2017; now U.S. Pat. No. 10,537,339, which issued on Jan. 21, 2020, which is a continuation of International Patent Application No. PCT/US2015/053096, filed Sep. 30, 2015, which claims priority to U.S. Provisional Patent Application No. 62/058,169, filed on Oct. 1, 2014, the contents of each of which are hereby incorporated by reference as if set forth in their entireties. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a powered surgical tool that includes a cutting accessory with an elongated shaft that is either rotated or reciprocated. More particularly, this invention relates to a powered surgical tool with a means to cool the accessory shaft. 
     BACKGROUND OF THE INVENTION 
     In modern surgery, one of the most important instruments available to medical personnel is the powered surgical tool. Typically, this tool comprises a handpiece in which a motor is housed. Secured to the handpiece is an accessory. The accessory is designed for application to a surgical site on a patient to accomplish a specific medical task. Some powered surgical tools are provided with drills or burs for cutting bores into hard tissue or for selectively removing the hard tissue. Still other powered surgical tools are provided with saw blades as cutting accessories. These tools are used for separating large sections of hard and/or soft tissue. The ability to use powered surgical tools on a patient has lessened the physical strain of physicians and other medical personnel when performing procedures on a patient. Moreover, most surgical procedures can be performed more quickly, and more accurately, with powered surgical tools than with the manual equivalents that preceded them. 
     The Applicant&#39;s Assignee&#39;s U.S. Pat. No. 5,888,200, (PCT Pub. No. WO 98/005261,) entitled, MULTI-PURPOSE SURGICAL TOOL SYSTEM, incorporated herein by reference, discloses a surgical tool system designed for a number of different applications. This tool system includes a handpiece in which a motor is housed. A first coupling assembly, also part of the handpiece, for selectively couples the shaft of an accessory to the motor shaft. This handpiece also includes a second coupling assembly. The second coupling assembly selectively secures an attachment to the front end of the handpiece. The second attachment includes an elongated nose as the distalmost portion of the attachment. Often internal to the attachment are bearings. The bearings provide a low friction interface between the moving shaft of the cutting accessory and the attachment nose which is static. 
     The nose of this type of surgical tool system thus performs two functions. First, some of these shafts tend to be small in size, 5 mm or less in diameter. Owing to the material from which these shafts are made and their size, the shafts are, when exposed to side loading, prone to undesirable bending. This bending occurs as a result of the distal end of the shaft, when pressed against tissue to perform a procedure, is subjected to appreciable side loading. Encapsulating an accessory shaft in a nose prevents this bending. 
     Secondly, the nose encapsulates the moving shaft. This prevents the shaft from contacting and entraining tissue that is not to be subject to which the cutting accessory is applied. This is especially important when the system is applied to tissue located more than a centimeter from the outer skin of the patient. If the location to which the cutting accessory applied is further below skin level and the rotating shaft is unexposed a practitioner might have to form an incision in the patient that is wider than the diameter of the shaft. This wide incision would be necessary to reduce the likelihood that the moving shaft could inadvertently contact tissue that should not be exposed to the moving shaft. 
     Present nose assemblies prevent undesirable side bending of accessory shafts and prevent the undesirable exposure of these shafts. However, a disadvantage of some nose assemblies is that, when the accessory is actuated a significant amount of friction induced heat is developed at the locations where the moving shaft abuts the components of the nose. This heat is conducted to exposed surfaces of the nose and to other portions of the accessory, including the exposed tip. When these surfaces of the tool system contact the tissue, the heat is transferred to the tissue. This heat has the potential of damaging healthy tissue that should otherwise not be affected by the procedure. This is especially true with nose assemblies that are relatively small in diameter, less than 1 cm. Owing to the size of these noses, it has proven difficult to fit a bearing assembly able to reduce the quantity of friction induced heat that is generated. Instead, inside this type of nose, the rotating shaft often abuts the inner wall of the nose that defined the bore in which the shaft is disposed. 
     This undesirable heating is especially prone to occur if the nose is what is referred to as a bent nose. As implied by its name a bent nose is a nose that is formed with a bend. Often this bend is within 3 cm of the distal end of the shaft. A surgeon may want to use a surgical tool with a bent nose for a number of reasons. These reasons all root from the fact that, since the nose is bent, the exposed end of the cutting accessory, the end applied to the tissue, is spaced away from the main body nose. One advantage of the cutting accessory being so spaced from the many body of the nose is that when looking down the nose, it is easier to view this end of the accessory as well as the tissue against which the cutting accessory is applied. Further, there are times when owing to the nature of the procedure being performed the surgeon would rather position the cutting accessory laterally against the tissue than longitudinally. Having the cutting accessory extend sidewise away from the main body of the nose facilitates this type of positioning of the cutting accessory. 
     A tool system with bent nose, by its very nature is formed with a bore that has a bend in the vicinity of the bend in the nose. The cutting accessory used with this type of tool system has a shaft that must be flexible enough to bend in the bent section of the nose bore. Thus, as a consequence of the nature of the components forming this type of system is that as the shaft rotates in the nose, the section of the shaft in the bent section of the nose would have a tendency to rub against the inner wall of the nose that defines the nose. This movement of the shaft against the static surface can be a significant source of friction induced heating of the nose. 
     A number of solutions have been proposed to either eliminate or reduce this undesirable heating. As mentioned above, one solution is to fit low friction bearings in the nose to eliminate the friction induced heating. Again, when the nose itself is relatively small in diameter this solution is often commercially impracticable. Another solution is to provide a cutting accessory used with this type of nose with a shaft that is of varying diameter. Specifically, the shaft is designed so the section of the shaft that is seated in the bent section of the bore has a diameter less than the diameters of the sections of the shaft that are seated in the straight section of the bore. When this type of shaft rotates, the narrow diameter section of the shaft has minimal if any contact with the surrounding bore-defining inner wall of the nose. This reduces the frictional heating of the nose in the vicinity of the bend. However, a disadvantage of this design is that the narrow diameter section of the shaft is structurally weaker than the rest of the shaft. When the tool is actuated, owing to this section of the shaft be repeatedly bent, this section of the shaft is subjected to appreciable mechanical stress. The combination of this section of the shaft being structurally weak and being subjected to appreciable bending increases the likelihood that, in the course of a procedure, this section of the shaft will be stressed to the point where the section breaks. Should this event occur, the procedure must be interrupted to both collect the separated parts of the cutting accessory and attached a new cutting accessory to the shaft. 
     A proposed solution to reduce the undesirable heating of the nose of surgical tool system as well as the accessory disposed in the nose is to flow fluid through or around the nose. This fluid is typically sterile water or saline. A known surgical tool system of this design has a nose into which plural longitudinally extending grooves are formed. A sleeve is disposed over the nose. During a procedure in which this assembly is used, the cooling fluid is flowed through these grooves. The sleeve prevents the fluid from flowing away from the nose until the fluid reaches the distal end of the nose. The fluid functions as a heat sink that extracts the heat from the nose and cutting accessory. The fluid flows the heat away from the tool system. This arrangement reduces the temperatures of the nose and cutting accessory from rising to the level at which when these components contact tissue, the tissue is subjected to potentially damage causing heating. 
     A disadvantage of the above assembly is that for the assembly to transfer a sufficient quantity of heat away from the nose and cutting accessory, a relatively large volume of irrigating fluid needs to be flowed through the nose. This fluid is discharged from the nose adjacent the site at which the cutting accessory needs to be applied. The presence of this fluid can interfere with the performance of the cutting accessory and obstruct the practitioner&#39;s view of the site at which the procedure is being performed. To prevent these undesirable consequences it may be necessary to almost continually apply suction to the site at which the procedure is being performed in order to draw this fluid away from the site. Having to perform this added step contributes to the complexity and/or time required to perform the procedure. 
     Another solution suggested to compensate for the friction induced heating of the nose of surgical tool system is place a wick of fluid retaining material over the wick. Prior to the use of the tool, a fluid, typically saline or sterile water, is coated over the wick. This fluid serves as a heat sink that absorbs the heat generated by the use of the tool. A disadvantage of this practice is that the fluid can absorb only so much heat before the fluid evaporates and is dispersed into the ambient environment as a gas, typically water vapor. Once the fluid has so evaporated, the wick has little thermal capacity to absorb the friction induced heat. If the surgeon wants to hold continue to maintain the nose below at a temperature below a below a certain level, the procedure needs to be interrupted in order to recoat the wick in a heat absorbing liquid. 
     SUMMARY OF THE INVENTION 
     This invention is directed to a new and useful surgical tool system. The surgical tool system of this invention is designed to extract the heat generated at the nose of a surgical handpiece so as to prevent the excessive heating of the nose and the cutting accessory disposed in the handpiece. The surgical tool system of this invention extracts this heat away from the handpiece without requiring the discharge of relatively large quantities of fluid at the site to which the system is applied. 
     It is a further object of this invention to provide an efficient means of producing a surgical handpiece with a nose of this invention. 
     The surgical tool system of this invention includes a surgical handpiece with an elongated nose. The handpiece of this invention is designed to actuate a cutting accessory. The cutting accessory has an elongated shaft. The shaft extends through a bore formed in the nose. In many versions of the invention the accessory shaft is rotated or reciprocated. 
     The handpiece nose is formed with an enclosed groove. The groove extends in a helical pattern such that, as the groove extends proximal to distally, the groove curves circumferentially around the nose. The groove thus curves circumferentially around the bore formed in the nose. A proximal end of the handpiece has a fitting into which irrigating solution is introduced into the groove. Adjacent the distal end of the nose, the groove is open. In some versions, the groove curves back to an outlet fitting. 
     In some versions of the invention, the nose includes a body and a shell disposed over the body. A groove is formed in the body. The shell is disposed over the body and the groove. The shell covers the groove so as to further define the enclosed channel. 
     In some versions of the invention, the outer shell is formed from a flexible material that is secured over the inner shell. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is pointed out with particularity in the claims. The above and further features and benefits of this invention are understood from the following Detailed Description taken in conjunction with the following drawings in which: 
         FIG.  1    is a perspective view of a surgical tool constructed in accordance with this invention; 
         FIG.  2    is an exploded view depicting how the front end attachment and the cutting accessory are separate from the handpiece; 
         FIG.  3    is an exploded view of the front end attachment and cutting accessory; 
         FIG.  4    is a cross sectional view of the front end attachment and cutting accessory; 
         FIGS.  5 ,  6  and  7    are enlarged cross sectional views of sections of the front end attachment and cutting accessory; 
         FIG.  8    is a perspective view of the where the nose emerges from the head piece of the front end attachment; 
         FIG.  9    is a perspective view of distal end of the nose and the cutting accessory that emerges from the nose; 
         FIG.  10    is view of the nose and accessory of  FIG.  1   , the extent to which the outer sleeve is disposed over the distal end of the nose is seen; 
         FIG.  11    is a perspective view of an alternative nose, with the shell removed, of this invention; 
         FIG.  12    is a side plan view of the nose of  FIG.  11   ; 
         FIG.  13    is top plan view of the alternative nose of  FIG.  11   ; 
         FIG.  14    is an exploded view of an alternative nose and the fittings that are attached to the nose of this invention; and 
         FIGS.  15 A,  15 B and  15     c  are, respectively, top, side and bottom plan views of the nose of  FIG.  14   . 
     
    
    
     DETAILED DESCRIPTION 
     The basic components of a powered surgical tool  30 , sometimes herein called a tool  30  or a tool system  30  or a system  30 , are seen in  FIGS.  1  and  2   . Tool  30  includes a handpiece  32 . Handpiece  32  has a body  34 , alternatively referenced to herein as a housing  34 . Disposed inside the handpiece body  34  is a motor  36 , represented by a phantom cylinder. Motor  36  may be any motor used to drive a motor shaft  38 , alternatively referenced herein as a handpiece shaft  38  or a handpiece drive spindle  38 , represented by a smaller phantom cylinder. Motor  36  is typically an electrical, pneumatically or hydraulically driven motor. A cable  40  is shown extending proximally from the handpiece body  34 . (“Proximal” is understood to mean towards the practitioner holding the handpiece, away from the site to which the handpiece is applied. “Distal” is understood to mean away from the practitioner, towards the site to which the handpiece is applied.) Cable  40  is the conduit over which electrical power, gas or a liquid is supplied to the motor  36  to drive the motor. It is also within the scope of this invention that motor  36  be battery powered. 
     A front end attachment  44  is removably attached to and extends distally forward from the handpiece body  34 . An attachment drive shaft  56  is rotatably disposed in the front end attachment  44 . When system  30  of this invention is assembled, shaft  56  engages the motor shaft  38  to be rotated by the motor shaft. A cutting accessory  120  is rotatably disposed in the front end attachment  44 . Cutting accessory  120 , as seen in  FIG.  3   , has an elongated shaft  122 . Attachment drive shaft  56  and cutting accessory shaft  122  are formed with complementary features that facilitate the removable attachment of the two shafts. The accessory shaft  122  extends through and forward of the distal end of the front end attachment  44 . In many versions of the invention the shaft  122  is formed so that the section of the shaft that extends through an attachment nose bore  92  has a constant diameter. Shaft  122  is understood to be flexible. This flexibility of the shaft  122  allows the shaft to bend as the shaft rotates in the bent section of nose bore  92 . 
     A tissue working member  124  is attached to the distal end of the accessory shaft  122  so as to be located forward of the attachment  44 . Tissue working member  124  is the component of the tool  30  that, when applied to tissue performs the desired surgical procedure. Tissue working member  124  is often a bur head or a drill bit. 
     From  FIGS.  3  and  4    it can be seen that the front end attachment  44  includes an attachment cap  46  that forms the main housing of the attachment. Cap  46  has a proximal section  48  that is generally of constant diameter. Integral with and extending forward from the proximal section  48  cap  44  has a distal section  50 . Extending distally from the proximal section  48 , the diameter of the distal section  50  decreases. Internal to the cap  46  is a cap bore  52 . Cap  46  is formed so that bore  52  has sections with different diameters. Generally, extending proximally to distally the diameter of the different sections of bore  52  decrease. 
     Not illustrated and not part of the present invention are features that facilitate the removable coupling of the front end attachment  44  to the handpiece body  34 . One such set of features include providing the handpiece body  34  and attachment cap  46  with complementary threaded surfaces. In still other versions of the invention, one of the body  34  or cap  46  is provided with a snap ring or spring loaded leg; the other one of the cap  46  or body  34  is formed with a void space to receive this spring element. Also not shown and not illustrated are geometric features integral with the handpiece shaft and attachment shaft that facilitate the releasable coupling of these components. The incorporated by reference U.S. Pat. No. 5,888,200 discloses one such assembly. A variation on this tool system is disclosed in U.S. Pat. No. 6,562,055, (PCT Pub. No. WO 01/060261,) entitled CUTTING ATTACHMENT FOR A SURGICAL HANDPIECE DESIGNED TO BE SELECTIVELY COUPLED TO THE HANDPIECE also incorporated herein by reference, discloses another assembly for holding an attachment shaft to the handpiece shaft. These incorporated by reference documents also disclose how a front end attachment can be held to a handpiece  32 . 
     The attachment drive shaft  56  is rotatably disposed inside cap  46 . In the illustrated version of the invention, the distal end of the drive shaft  56  extends proximally rearwardly out of the cap  46 . The drive shaft  56  is shown to have indentations  58  on the outer surface of the shaft. The indentations receive locking features integral with the handpiece drive spindle  38 . The seating of the handpiece locking features into the drive shaft indentations  58  hold the drive shaft to the handpiece drive spindle  38  so these two components rotate in unison. The exact means by which the attachment drive shaft  56  is held to the handpiece drive spindle is not part of the present invention. The incorporated by reference documents including the now incorporated by reference U.S. Pat. No. 8,597,316 PCT Pub. No. WO 2010/028001 disclose means by which these two components are releasably held together. 
     A sleeve  60  and a bearing assembly  78  cooperate to rotatably hold the attachment drive shaft  56  in cap  46 . Sleeve  60  is formed from two sections  62  that a pressed together. The sleeve  60  is shaped to have a foot  64 . Foot  64  forms the proximal end of the sleeve. Foot  64  is circular in shape and is the widest diameter portion of the sleeve  60 . A sleeve stem  66  extends forward from foot  64 . Sleeve stem  66  is cylindrical in shape and has a diameter less than that of the foot  64 . The sleeve stem  66  is shaped to tightly fit in the most distal section of the cap bore  52 . The components forming the attachment  44  are further formed so that sleeve stem  66  extends forward of cap  46 . Forward of stem  66 , sleeve  60  has a distal end tip  68 . Extending distally forward from the stem  66 , the outer diameter of the tip decreases. 
     A sleeve bore  70  identified in  FIG.  5   , extends proximally from the distal end the sleeve  60 . Within the foot  64  there is a cylindrical sleeve void  72 . An annular step  71  extends inwardly from and circumferentially around the inner wall of the sleeve  60  that defines the proximal end of bore  70 . Step  71  separates bore  70  from void  72 . Not identified but seen in  FIGS.  4  and  5    are the opening in the proximal end of the sleeve  60  that opens into void  72 . Also not identified is the opening defined by step  71  that is the opening between bore  70  and void  72 . 
     Bearing assembly  78  rotatably holds the attachment drive shaft  56  to sleeve  60 . The bearing assembly  78  is disposed in sleeve void  72 . Drive shaft  56  extends through the bearing assembly  78 . The drive shaft  56  extends into the proximal end of sleeve bore  70 . 
     An attachment nose  82 , also part of the front end attachment  44 , is seated in and extends forward from cap  46 . Nose  82  is a single piece component formed from stainless steel, plastic, aluminum or a ceramic. The nose  82  has three main sections  84 ,  86  and  90  each of which is general circular in cross sectional shape. A first section is the proximal section  84 . Nose proximal section  84  is the widest diameter portion of the nose  82 . The nose proximal section  84  is the portion of the nose  82  that is seated in sleeve bore  70 . The nose proximal section  84  also extends a short distance forward of sleeve  60 . A nose middle section  86  is located forward of proximal section  84 . The middle section  86  has a diameter less than that of the proximal section  84 . Not identified is the tapered transition section between nose sections  84  and  86 . Nose middle section  86  is the longest of the three main nose sections. The illustrated attachment  44  is formed so that, proximal to the distal end of the middle section  86 , the middle section is formed with bend  88 . Distal to bend  88 , is the nozzle distal section  90 . Nose  82  is formed so that diameter of the distal section  90  decreases as the distal section extends forward from the middle section  86 . 
     When the attachment  44  is assembled, the nose middle and distal sections  86  and  90 , respectively, extend forward of sleeve  60 . The maximum diameter of these sections of the nose  82  including the below discussed shell disposed over the nose is 10 mm and, in many versions of the invention, 5 mm or less. 
     Attachment nose  82  is further formed so that a bore  92 , identified in  FIGS.  6  and  7   , extends proximally through the nose from the distal end of distal section  90 . Bore  92  is centered on the distal-to-proximal longitudinal axis through the nose  82 . In versions of the invention in which nose  82  is formed with bend  88 , bore  92  has a bend. Bore  92  is dimensioned to receive cutting accessory  120  so the accessory shaft  122  can rotate in the bore. At the proximal end of the nose  82 , within proximal section  84 , bore  92  opens into a counterbore  94 , seen in  FIG.  5   . Counterbore  94  is wider in diameter than bore  92 . Counterbore  94  is dimensioned to receive the attachment drive shaft  56  so the drive shaft  56  can rotate in the nose  82 . 
     Nose  82  is also formed to have a nose groove  96  that extends proximally to distally along the outer surface of the nose. More specifically, the groove  96  extends in a helical pattern around the nose. The proximal end of the groove  96  is adjacent the proximal end of nose middle section  86 . When the groove reaches the nose distal section  90 , the groove extends linearly. Groove  96  terminates approximately 5 to 10 mm proximal from the distal end of the nose  82 . 
     A shell  102  is disposed over nose  82 . In some versions of the invention, shell  102  is a section of heat shrink tubing. The shell  102  is disposed over nose  82  to extend over groove  96 . In many versions of the invention the shell does not extend over the whole of groove  96 . More specifically, the shell does not extend over the portion of the nose in which the distal end of groove  96  is formed. In the illustrated version of the invention, the proximal end of the shell is located distally forward of the portion of nose middle section  86  in which the proximal most turns of groove  96  are formed. Shell  102  also does not extend over the portion of groove  96  formed in the nose distal section  90 . Thus, as seen in  FIG.  10   , the distal end of groove  96  is open to the environment. 
     Attachment  44  also includes an irrigation fitting  106 . Fitting  106  includes a head  108 . Head  108  is generally in the form of a tube that is open at the proximal end. Head  108  is dimensioned to receive a tube  105  ( FIG.  1   ) in the open proximal end. A tube  112  extends from the distal end of fitting head  108 . The tube  112  is in fluid communication with the bore that extends through the head (bore head not identified). Tube  112  has a main section  114  that extends from head  108 . Tube main section  114  is generally coaxial with head  108 . At the distal end of the main section a leg  116  angles away from the main section. A foot  118  which extends forward from leg  116  is the most distal portion of the tube  112 . Foot  118  is helical in shape. More particularly foot  118  is designed to seat in the in groove  96  formed in nose  82 . 
     In some versions of the invention, fitting foot  118  is secured in nose groove  96  by a friction compressive fit. Once the fitting is so secured, shell  102  is secured over nose  82 . In some versions of the invention the securing of the shell  102  over the nose  82  and fitting foot  118  secures the fitting  106  to the nose. The components of this invention are designed so that the open distal end of fitting tube  112  opens into a portion of the nose groove  96  that is covered by shell  102 . 
     Cutting accessory  120  has shaft  122  able to rotate in attachment nose bore  92 . In the described version of the invention, bore  92  is angled. Accordingly, in this version of the invention, shaft  122  is sufficiently flexible so as to be able to rotate in the bent portion of bore  92 . The proximal end of the accessory shaft  122  is formed with features designed to facilitate the removably coupling of the shaft to the attachment drive shaft  56 . In the illustrated version of the invention, the proximal end of the accessory shaft is dimensioned to simply press fit in a bore that extends proximally from the distal end of drive shaft  56 . The specific features integrally with these two shafts  56  and  122  are beyond the scope of the present invention. 
     Surgical tool  30  of this invention is prepared for use by coupling front end attachment  44  to the handpiece  32 . The cutting accessory  120  is coupled to the attachment. Cable  40  is connected to the device that provides power to motor  36 . A tube  105  that is connected to a source of irrigating fluid is attached to fitting head  108 . Once these connections are made, tool  30  is ready for use. Owing to the small diameter of the nose  82 , front end attachment  44  of this invention can be used to direct the cutting accessory  120  through a portal or opening in the patient that is relatively small in size to the site internal to the patient at which the accessory is to be applied. In some versions of the invention, the distal section of the nose may have a maximum diameter of 3 mm. In these versions of the invention the bore  92  internal to the nose, including the bent section of the bore that extends through bend  88 , may have a diameter of 1.5 mm or less and in some versions of the invention 1.0 mm or less. A bore  92  with a diameter of 1.5 mm is able to receive the shaft  122  of a cutting accessory that has a diameter of 1.0 mm or less. A bore  92  with a diameter of 1.0 mm is able to receive a cutting accessory with a shaft  122  having a diameter of 0.5 mm or less. The tissue working member of this type of cutting accessory may have a diameter of 0.7 mm or less. These versions of the invention may be inserted in portals, openings in the patient, that are no wider than the diameter need to facilitate the insertion of nose in the patient. 
     Tool  30  is used like a conventional tool. When there is a need to use the cutting accessory  120 , motor  36  is actuated. The rotational moment output by the motor  36  is transferred from the handpiece shaft  38 , the attachment shaft  56  and the accessory shaft  122  to the tissue working member  124 . The tissue working member is applied against tissue to perform the desired surgical procedure. 
     The nose of this invention does not include any low friction bearings in the bore  92  between the inner surface of the bore and the accessory shaft  122  that minimize the generation of friction induced heating that occurs when the shaft rubs against the inner surface of the nose that defines bore  92 . The rotation of the cutting accessory shaft  122  in nose  82  causes the friction of the movement of the shaft to generate heat in the nose and shaft. This heat is especially prone to occur in the bent section of the nose. This is because in this section of the nose, the bent section of the shaft continually rubs against the bent section of the inner surface of the nose that defines the bend in the bore  92 . To prevent this heat from inducing an unacceptable temperature rise in nose  82  or cutting accessory  120 , irrigating fluid is flowed from tube  105  and fitting  106  into the enclosed channel defined by nose groove  96  and the portion of shell  102  disposed over the nose  82 . This fluid functions as a heat sink that draws away the friction-generated heat from the nose  82  and cutting accessory  120 . Groove  96  has an unwound length that, at a minimum, is 1.05 times greater than the length of the narrow diameter portion of the nose and tube  112  that extends forward from the cap  46  or any sleeve integral with the cap. This is the portion of the nose understood to have a diameter of 10 mm or less and often 5 mm or less. In still more preferred versions of the invention, the unwound length of the groove is 1.25 times or greater than this length. This means that over the length of the small diameter portion of the nose  82 , there is a relatively large surface area between the surface of the nose and the fluid that functions as a heat sink. Consequently, a significant amount of the thermal energy, the heat, generated by rotation of the cutting accessory  120  is drawn away from both the nose  82  and the cutting accessory. This reduces the extent to which the temperature of these components rise to the level at which they may transfer heat to the tissue that results in the thermally induced damage of the tissue. 
     A further feature of this version of the invention is that the quantity of irrigating fluid that is flowed through the nose and discharged adjacent the site to which the tissue working member is applied is held to a minimum. More specifically invention, where there is a single channel through the nose discharges less fluid than an assembly wherein there are plural channels each channel having the same cross sectional area as the channel in a nose with a single channel. 
     Likewise this invention allows the system  30  to include a cutting accessory  120  with a shaft  122  that, is not formed so that the section of the shaft seated in the bent section of the bore  92  has, in comparison to other sections of the shaft  122  a reduced diameter. This reduces the likelihood that, the continued bending of this section of the shaft  122  will stress the shaft to the point that shaft fractures and is rendered unusable. 
       FIGS.  11 ,  12  and  13    depict the structure of an alternative nose, nose  142 , that may be incorporated into this invention. Nose  142  has a proximal section  144 , a middle section  146  and a distal section  150  similar to the sections  84 ,  86  and  90 , respectively of nose  82 . Nose  142  is further formed to have a bend  148  analogous to bend  88  of nose  82 . A bore  152 , the open end of which, extends longitudinally axially through the nose  142 . Bore  152  is analogous to bore  92  of nose  82 . 
     A groove  154  is formed in nose  142 . A difference between groove  154  and groove  96  of nose  82  is that groove  154  has a variable pitch. Here “pitch” is understood to be to be the length of groove along the nose for each 360° turn of the groove. More particularly groove  154  has a relatively large pitch where the nose is straight. Thus, groove  154  has a relatively large pitch along the proximal portion of the middle section  146  where, groove  154  has a relatively large pitch. Around bend  148 , the pitch is relatively small. While not seen it is understood that nose  142  is covered with an outer shell similar to the shell  102 . The portion of the shell disposed over the groove  154  covers the groove so as to form the enclosed fluid channel in the nose. 
     When a tool system with nose  142  is actuated, the greatest rubbing of the accessory shaft  122  against the nose occurs within the portion of the nose forming bend  148 . This means that the bent section of nose  142  is the location where some of the greatest frictionally heating of the nose and accessory shaft occurs. In this version of the invention, owing to the relatively small pitch of groove  154  this is the section of the tube wherein, in terms of surface area, there is the largest interface between the nose and irrigating fluid. This results in relatively large drawing away of the heat generated in this section of the nose. 
     As discussed above, proximal to this location the groove has a relatively large pitch. A benefit of this design is related to fact that when the groove of this invention is present, the absence of nose forming material inherently reduces the mechanical strength of the nose. This is in comparison to a nose that does not have the groove. However, in this design at the location where large quantity of heat is not generated, since the groove is of large pitch, the amount of material absent from the nose to form the groove is less than what would be absent if the groove had a small pitch. This means that the section of nose  142  with the large pitch groove has greater mechanical strength than what would be present if this section of the groove is formed with a pitch identical or similar to the groove pitch where bend  148  is present. Thus, this version of the invention provides the heat sinking properties of the irrigation fluid without significantly sacrificing the structural strength of the nose where the benefits of the fluid are less needed. 
     Still a further feature of the above version of the invention is that can require less time to machine a nose have a groove with a large pitch section than a nose with that has small pitch groove. 
       FIGS.  14  and  15 A through  15 C  illustrate an alternative version of the invention. Nose  162  has a proximal section  164 , a middle section  166  and a distal section  170  similar to the sections  84 ,  86  and  90 , respectively of nose  82 . Nose  142  is further formed to have a bend  168  analogous to bend  88  of nose  82 . A bore  172 , the open end of which, extends longitudinally axially through the nose  162 . Bore  172  is analogous to bore  92  of nose  82 . 
     A groove  174  is formed in nose  142 . The groove  174  is formed in the nose middle section  166 . A difference between groove  154  and groove  96  of nose  82  is that groove  154  does not have an open end at the nose distal section  170 . Instead, immediately distal to bend  168 , the groove loops back around the nose  162 . The groove  174  extends back along the nose proximal section  164 . The groove  174  thus has two ends adjacent the nose proximal section  164 . 
     The previously described fitting  106  is fitted to nose  162  to be open into one end, end  173  of groove  174 . A second fitting, fitting  180 , is fitted to the second end, end  175  of groove  174 . Not seen is the shell analogues to shell  102  that is seated over the nose  162 . 
     During use of this version of the invention, fluid is introduced into the groove through fitting  106  as in the prior described versions of the invention. The fluid that flows through groove  174  is not discharged. Instead the fluid flows through out through fitting  180  An advantage of this version of the invention is that it provides the cooling advantage of the fluid without requiring the discharge of fluid at the site to which the tool is applied. 
     The above is directed to specific versions of the invention. Other versions of the invention may have features different from what has been described. 
     For example, in some versions of this invention, the small diameter nose of this invention may be built directly into the handpiece  32 . Thus, in these versions of the invention there is no removable front end attachment. In these versions of the invention, the cutting accessory shaft is directly coupled to a rotating output shaft that is actuated by the motor. In these versions of the invention the handpiece has a coupling assembly that releasably holds the accessory shaft to the handpiece output shaft. 
     Similarly, there is no requirement that in all versions of the invention, the nose be bent. Likewise, in some versions of the invention, the nose may have plural bends. In versions of the invention with wherein the nose has plural bends the enclosed channel through which the irrigation fluid flows may have plural spaced apart section wherein the channel has a relatively small helical pitch. 
     In some versions of the invention, fitting  106  is welded, braised or glued to the nose  82 . 
     Likewise, the front end attachment is not limited to tools that include a motor driven cutting accessory. The front end attachment of the tool of this invention may be a device that is vibrated using transducers. Alternatively, the cutting accessory of this invention may be a device that applies thermal energy or photonic energy (light) to the site to which the accessory is applied. The front end attachment of this invention will be useful to prevent any heat that is being generated from radiating outwardly from a location other than at the distal end tip of the accessory. 
     Further, the nose of this invention may be structured out of components different from what has been described above. Thus there is no requirement that the enclosed channel through which the irrigating fluid flow always be defined by a nose formed with a groove and a shell heat shrinked over the tube. In one alternative version of the invention, the nose may consist of an inner shell over which a rigid outer shell is secured. The channel may be defined by a groove in the outer surface of the inner shell. Alternatively, or in combination with this first groove the channel may be defined by a groove formed in the surface of the inner shell disposed over the outer shell. In still other versions of the invention the nose may be a monolithic component in which the groove is formed. For example, the nose by formed by molding metal, plastic or ceramic. Internal to the mold used to define the nose there is a first mandrel and a second mandrel. The second mandrel is helically shaped and surrounds the first mandrel. The first mandrel defines the bore in which the accessory shaft is disposed. The second mandrel defines the enclosed channel. As a result of the molding process and the removal of the mandrels, the nose includes the bore for the accessory and the enclosed channel through which irrigation fluid is flowed. 
     Accordingly, it is an object of the appended claims to cover all such modifications and variations that come within the true spirit and scope of the invention.