Patent Publication Number: US-6221088-B1

Title: Powered handpiece and surgical blades and methods thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of prior application Ser. No. 09/005,012 filed Jan. 9, 1999, now U.S. Pat. No. 6,010,477 which is a divisional of prior application Ser. No. 08/775,147 filed Dec. 31, 1996 and now abandoned, which is a continuation-in-part of prior application Ser. No. 08/719,130 filed Sep. 24, 1996 and now abandoned, the disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to powered handpieces for driving surgical blades and, more particularly, to electric motor driven, powered handpieces, surgical blade assemblies for use with such handpieces, powered handpiece systems utilizing non-sterile electric motors and methods for supplying powered handpieces for use in surgery. 
     2. Brief Description of the Prior Art 
     Powered handpieces are commonly used in many medical specialities to drive surgical blades for performing various diverse cutting functions including resection, comminution, dissection, debridement, shaving, drilling, pulverizing and shaping of anatomical tissue. In the areas of ENT/Head/Neck surgery, powered or motorized handpieces and systems have been proposed as illustrated by the Stryker Hummer system of Stryker Endoscopy, San Diego, Calif., the Apex System of Linvatec, Incorporated, Largo, Fla., the PS 3500 and EP-1 Surgical Drive System of Dyonics, Inc. of Andover, Mass. and the Wizard microdebrider system of Xomed, Inc., Jacksonville, Fla. Conventional powered handpieces are typically all metal and reusable in design with permanently installed motors. Such handpieces are typically decontaminated and sterilized for reuse by steam autoclave and/or soaking in a disinfectant solution resulting in reduced reliability and/or life of the motors due to the heating and cooling cycles and/or due to moisture seepage. A further disadvantage of conventional powered handpieces is that the motor of a handpiece cannot be replaced prior to surgery with a different speed motor in accordance with the procedure to be performed. 
     Conventional powered handpieces generally use suction to evacuate anatomical tissue cut or excised by the blades. Powered handpieces currently in use generally force the excised anatomical tissue to follow a suction path with major or substantial bends or angles. Accordingly, there is a tendency for the excised tissue to become clogged in the handpieces thusly impairing operation of the handpieces and compromising the surgical procedure. 
     Another drawback of some conventional powered handpieces is that the handpieces can only be operated by a power console specifically designed for the handpieces and not by a power consoles designed for other manufacturer&#39;s handpieces. Such handpieces therefore require a major investment in capital equipment for the associated power console. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a primary object of the present invention to overcome the disadvantages of prior art powered or motorized handpieces for driving surgical blades. 
     Another object of the present invention is to facilitate evacuation of cut or excised anatomical tissue from the cutting tip of a surgical blade and out of a powered handpiece for the blade. 
     A further object of the present invention is to avoid clogging of excised tissue evacuated through a suction channel of a powered handpiece for a surgical blade by reducing areas of turbulence in the suction channel. 
     A still further object of the present invention is to evacuate cut or excised anatomical tissue from a surgical blade through a suction channel extending through a powered handpiece for the blade, the suction channel having a portion extending through a drive shaft for rotatably driving the blade with the channel portion being parallel to a longitudinal axis of a motor in the handpiece. 
     An additional object of the present invention is to increase the reliability and/or life of an electric motor of a reusable powered handpiece by providing a method of supplying a powered handpiece for surgery including removing the electric motor from a body of the handpiece prior to medically acceptable sterilization of the handpiece body to medical standards and reinstalling the electric motor in the sterilized handpiece body prior to reuse of the handpiece. 
     The present invention has as a further object to utilize a non-sterile motor in a reusable powered handpiece by removing the non-sterile motor from a body of the handpiece prior to sterilization of the handpiece body to medical standards and reinstalling the non-sterile motor in the sterilized handpiece body subsequent to sterilization without contaminating the sterilized handpiece body. 
     The present invention has as an additional object to provide a device for installing a non-sterile motor in driving engagement with a drive unit in a sterile handpiece body without contaminating the sterile handpiece body. 
     Additionally, the present invention has as an object to provide a surgical blade assembly for use with a reusable powered handpiece having a non-sterile motor removable from a body of the handpiece prior to medically acceptable sterilization of the handpiece body to medical standards and reinstallable in the handpiece body subsequent to sterilization thereof. 
     Another object of the present invention is to provide a surgical blade assembly for use with a reusable powered handpiece having a suction channel extending through a drive shaft for rotatably driving the blade, the drive shaft being driven by a motor disposed parallel to the drive shaft. 
     Some of the advantages of the present invention are that diverse non-sterile, electric motors are readily interchangeable with the handpiece allowing an optimal motor to be selected in accordance with procedural use, the handpiece is relatively lightweight, compact and ergodynamically functional for use by surgeons in various specialities and, in particular, the areas of ENT/Head/Neck surgery, accurate alignment of the motor assembly with the drive unit is assured during installation of the motor assembly in the handpiece body, the motor assembly can be installed in the handpiece body by operating personnel just prior to the surgical case, the handpiece can be powered off of various conventional power consoles, and various diverse blades are interchangeable with the handpiece for performing various diverse functions. 
     These and other objects, advantages and benefits are realized with the present invention as characterized in a powered handpiece including a reusable handpiece body having a distal end for releasably receiving a surgical blade, a drive unit in the handpiece body including a drive shaft for driving the blade to cut anatomical tissue, a motor assembly for being disposed in the handpiece body for driving the drive unit and an electrical cord assembly for being electrically coupled between the motor and a power console. The handpiece body is capable of being medically sterilized to medical standards, such as by steam autoclave, gas sterilization and/or soaking, prior to each use. The motor assembly is removable from the handpiece body prior to sterilization of the handpiece body and is replaceable in the handpiece body subsequent to sterilization thereof without contaminating the sterile handpiece body. An installation device for inserting the motor assembly in the sterilized handpiece body without contaminating the sterilized handpiece body includes a funnel capable of being sterilized to medical standards and having a flared head and a tubular stem for being disposed over an open proximal end of the handpiece body. The motor assembly is inserted through the funnel into the open proximal end of the handpiece body without impairing the sterility of the handpiece body. In order to insure that the motor assembly is inserted in the handpiece body in driving engagement with the drive unit, an alignment mechanism is provided including a slot or keyway in the proximal end of the handpiece body and a protrusion or key on the motor assembly for being received in the slot; and, when the key of the motor assembly is received in the keyway of the handpiece body, the motor assembly will be in driving engagement with the drive unit. The funnel includes a protrusion or key for being received in the keyway of the handpiece when the funnel is disposed over the handpiece body. A notch is disposed in the funnel in longitudinal alignment with the key of the funnel and, therefore, with the keyway of the handpiece. The key of the motor assembly and the key of the funnel can be received simultaneously in the keyway such that the key of the motor assembly is passed through the notch into the keyway when being inserted through the funnel to insure proper alignment of the motor assembly with the drive unit. Once the motor assembly is properly installed in the handpiece body, the funnel is removed and the electrical cord assembly is coupled between the motor assembly and, therefore, the handpiece body, and a power console. The electrical cord assembly, which is capable of being sterilized to medical standards for reuse, includes a first plug for being electrically coupled with an electrical connector of the motor assembly and a second plug for being electrically coupled with a power console. The first plug carries a locking ring selectively movable into locking engagement with the proximal end of the handpiece body to secure the motor assembly therein. A surgical blade assembly for use with the powered handpiece according to the present invention includes an elongate outer tubular blade having a distal cutting end, a hub mounting a proximal end of the outer blade, an elongate inner tubular blade having a distal cutting end for cooperating with the cutting end of the outer blade to cut anatomical tissue, and a hub mounting a proximal end of the inner blade. The inner blade is concentrically disposed in the outer blade with the inner blade passing through the hub of the outer blade. The hubs of the outer and inner blades are releasably coupled with the distal end of the handpiece body with the inner blade in driving engagement with the drive shaft. The handpiece body includes a substantially straight suction channel for evacuating tissue cut by the blades through the handpiece body for external collection. The suction channel includes a portion extending through the drive shaft parallel to a longitudinal axis of the motor assembly. 
     Other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings, wherein like parts in each of the several figures are identified by the same reference characters. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a powered handpiece according to the present invention. 
     FIG. 2 is an exploded view, partly in section, of the powered handpiece according to the present invention. 
     FIG. 3 is a side sectional view of a collet assembly of the powered handpiece. 
     FIG. 4 is a side sectional view of a transfer hub assembly of the powered handpiece. 
     FIG. 5 is a side view, partly in section, of a front drive shaft of a drive unit disposed in the transfer hub assembly. 
     FIG. 6 is a side view, partly in section, of a rear drive shaft of the drive unit. 
     FIG. 7 is a top view of the rear drive shaft. 
     FIG.  8 . is a broken side view of a distal portion of a motor assembly of the handpiece. 
     FIG. 9 is a broken side view, partly in section, of a proximal portion of the motor assembly. 
     FIG. 10 is a side view of an electrical connector of the motor assembly. 
     FIG. 11 is a proximal end view of the electrical connector. 
     FIG. 12 is a distal end view of the electrical connector. 
     FIG. 13 is a broken side view, partly in section, of an electrical cable assembly of the powered handpiece connected between a body of the handpiece and a power console. 
     FIG. 14 is a broken perspective view of a plug of the electrical cable assembly for mating with the electrical connector. 
     FIG. 15 is a side sectional view of an installation device for installing the motor assembly in the body of the handpiece. 
     FIG. 16 is a rearward end view of the installation device. 
     FIG. 17 is a forward end view of the installation device. 
     FIG. 18 is a fragmentary view, partly in section, of the installation device. 
     FIG. 19 is a broken, exploded perspective view of the installation device. 
     FIG. 20 is a broken side view of a blade assembly for use with the powered handpiece according to the present invention. 
     FIG. 21 is a side sectional view of a hub of an outer blade of the blade assembly. 
     FIG. 22 is a broken side view, partly in section, of an inner blade and hub of the blade assembly. 
     FIG. 23 is an end view of the hub of the inner blade. 
     FIG. 24 is a side sectional view of a seal for the hub of the inner blade. 
     FIG. 25 is a sectional view of an alternative seal for the drive unit of the powered handpiece. 
     FIG. 26 is a side view, partly in section, illustrating a lip seal for the drive unit of the powered handpiece. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A powered surgical handpiece  10  according to the present invention is illustrated in FIGS. 1 and 2 and includes a handpiece body  12  and a motor assembly  14  for being removably installed in handpiece body  12 . The handpiece body  12  includes a collet assembly  16 , a transfer hub assembly  18  and a motor enclosure  20 . Collet assembly  16 , as shown in FIG. 3, is designed to releasably couple a desired surgical blade to the handpiece body and includes an outer collet member  22 , a middle collet member  24  and an inner collet member  26 . Outer collet member  22 , which is preferably made of stainless steel, is hollow and has a cylindrical rearward section  28  mounted to a forward end of transfer hub assembly  18  and a cylindrical forward section  30  extending distally from rearward section  28  in longitudinal or axial alignment therewith to terminate at a peripheral edge. Rearward section  28  has a uniform external diameter, smaller than a uniform external diameter of forward section  30 , except for a distal portion of the rearward section  28  which is flared or of increasing external diameter in the distal direction to merge with the external diameter of the forward section  30 . A plurality of longitudinally extending grooves or recesses  31  are formed in an external surface of the wall forming rearward section  28 , the grooves  31  being of the same length and extending part way through the thickness of the rearward section wall. Grooves  31 , which extend parallel to a longitudinal axis of the outer collet member  22 , are juxtaposed to be laterally aligned with one another with little or no space between lateral or side edges of adjacent grooves  31  as shown in FIG. 1. A plurality of longitudinally extending grooves or recesses  32 , similar to grooves  31 , are formed in an external surface of the wall forming forward section  30  to extend part way through the thickness of the forward section wall. Grooves  32  extend parallel to the longitudinal axis of the outer collet member  22  and are juxtaposed to be laterally aligned with one another. The grooves  32  are laterally juxtaposed with a space between lateral or side edges of adjacent grooves  32  that is greater than the space between the side edges of grooves  31  as shown in FIG.  1 . Grooves  32  are of the same length except for grooves  32 ′, spaced 90° from one another about the longitudinal axis of outer collet member  22 , which-have a length less than the length of the remaining grooves  32 . Set screws  33  are received in holes formed through the thickness of the forward section wall distally of and in longitudinal alignment with grooves  32 ′, respectively, with the set screws  33  disposed proximally of distal ends of the remaining grooves  32 . The grooves  31  and  32  have rounded distal and proximal ends and serve to facilitate grasping of the handpiece body  12 . Outer collet member  22  has a lumen or internal passage extending entirely therethrough with the rearward section  28  defining a rearward passage section of uniform diameter or cross-section, and the forward section  30  defining a forward passage section of uniform diameter or cross-section larger than the diameter or cross-section of the rearward passage section. The rearward section wall is of increased thickness along the distal portion of the rearward section  28  to define an internal shoulder  34  extending transverse to the longitudinal axis of the outer collet member  22  at the junction of the rearward passage section with the forward passage section. The set screws  33  protrude inwardly into the forward passage section. 
     Middle collet member  24 , which is preferably made of stainless steel, is hollow and includes a tubular stem  35  terminating proximally at an outwardly protruding, transverse flange  36  and includes a cylindrical front end  37  extending longitudinally, distally from the stem  35  in longitudinal or axial alignment therewith to terminate distally at a tapered nose  38 . The external diameter of stem  35  is smaller than the external diameter of front end  37  such that an external, transverse shoulder  39  is formed at the junction of front end  37  with stem  35 . The front end  37  and the flange  36  have the same external diameter, which is selected to be closely received in the forward section  30  of the outer collet member  22  while allowing the middle collet member  24  to move longitudinally relative to the outer collet member. Nose  38  defines an annular rim  40 , larger in external diameter than front end  37 , tapering to a transverse planar end wall  41 . A plurality of radially extending grooves or recesses  42  are formed in the truncated conical external surface of nose  38  to facilitate grasping of the middle collet member  24 . A lumen or internal passage extends entirely through the middle collet member  24  and includes a rearward passage segment of uniform diameter or cross-section extending through stem  35  and part way into front end  37 , an intermediate passage segment of increasing diameter or cross-section extending distally from the rearward passage segment and a forward passage segment of uniform diameter or cross-section extending distally from the intermediate passage segment to terminate at an inner face of end wall  41 . The forward, intermediate and rearward passage segments are longitudinally or axially aligned with one another, and the interior surface of the front end  37  is angled along the intermediate passage segment to define an internal sloping shoulder  43  between the forward and rearward passage segments. The end wall  41  has an opening or aperture  44  therein longitudinally or axially aligned with the internal passage of middle collet member  24  and establishing communication with the forward passage segment from externally of the handpiece body  12 . 
     Inner collet member  26  is preferably made of stainless steel and comprises an elongate, hollow cylindrical or tubular member of uniform external diameter defined by a wall of uniform thickness along a distal portion of the cylindrical member and of uniform greater thickness along the remainder of the cylindrical member to form an internal transverse shoulder  45 . A lumen or internal passage is defined entirely through the inner collet member  26  and includes a rearward passage portion of uniform diameter or cross-section and a forward passage portion of uniform diameter or cross-section, larger than the uniform diameter or cross-section of the rearward passage portion, with the shoulder  45  being disposed at the junction of the forward and rearward passage portions. A plurality of semi-spherical holes  46  are formed through the wall of the distal portion of the inner collet member  26  at 120° spaced locations about a longitudinal axis of the inner collet member  26  with the holes  46  communicating with the forward passage portion. A spherical ball bearing  47 , is disposed in each hole  46  such that the ball bearings  47  protrude externally beyond an external surface of the inner collet member  26  and protrude internally beyond an internal surface of the inner collet member to protrude into the forward passage portion while being prevented from passing through the holes  46  into the forward passage portion. The inner collet member  26  has an external diameter or size to be closely received in the rearward passage section of the outer collet member  22  with the external surface of the inner collet member in contact with an internal surface of the outer collet member. 
     Middle collet member  24  is assembled to the outer collet member  22  in concentric or coaxial arrangement with stem  35  disposed in the forward passage section of the outer collet member  22  and flange  36  disposed proximally of set screws  33 . The distance that set screws  33  protrude inwardly into the forward passage section of outer collet member  22  is the same as or slightly less than the height of external shoulder  39 . The inner collet member  26  is concentrically or coaxially disposed in the outer collet member  22  with a proximal end of the inner collet member  26  fixedly secured, such as with adhesive, in rearward section  28  such that a distal end of the inner collet member  26  is disposed slightly distally of the distal peripheral edge of the outer collet member  22 . A helical coil spring  48 , preferably made of stainless steel, is concentrically disposed around the inner collet member  26  and is mounted in compression between internal shoulder  34  and flange  36  to bias the middle collet member  24  longitudinally, distally relative to the outer collet member  22  to an extended position as shown in FIGS. 2 and 3. 
     In the extended position, flange  36  is biased into abutment with set screws  33 , and external shoulder  39  is disposed slightly proximally of the distal peripheral edge of outer collet member  22 . There is a small circumferential gap or space between the external surface of the inner collet member  26  and an internal surface of stem  35  such that the protruding ball bearings  47  are in contact with the internal surface of stem  35  when the middle collet member  24  is in the extended position. Accordingly, the ball bearings  47  cannot move radially outwardly due to confinement by stem  35  and cannot move inwardly through the holes  46 . The middle collet member  24  is movable longitudinally, proximally relative to the outer collet member  22  from the extended position to a retracted position wherein the external shoulder  39  abuts the set screws  33  which serve as a positive stop or abutment limiting proximal movement of the middle collet member  24  in the retracted position. In the retracted position, ball bearings  47  are no longer disposed in or aligned with stem  35  but, rather, are disposed in or aligned with the diametrically larger forward passage segment of front end  37  such that the ball bearings  47  can be moved radially outwardly by a hub of a surgical blade introduced in inner collet member  26  via aperture  44  as explained further below. Middle collet member  24  is movable from the retracted position back to the extended position due to the bias of spring  48  causing ball bearings  47  to again be held in place in the holes  47  of the inner collet member  26 . 
     Transfer hub assembly  18  is best illustrated in FIG.  4  and includes a transfer body  49  mounted to the collet assembly  16  and a drive unit  50  disposed in the transfer body  49  for driving a surgical blade inserted in collet assembly  16 . Transfer body  49  is preferably made of titanium or stainless steel and includes a distal cylindrical extension  51  and a proximal cylindrical extension  52  longitudinally and laterally offset from and not aligned with one another and a midsection  53  extending diagonally or angularly between the distal and proximal cylindrical extensions. A recess extends longitudinally in the distal extension  51  to terminate proximally at an end wall  54  in the midsection  53 . A recess extends longitudinally in the proximal extension  52  to terminate distally at an end wall  55  in midsection  53 , the end wall  55  being disposed distally of and parallel to end wall  54 . The distal and proximal extension recesses are parallel to one another and are in communication with one another in midsection  53 . A tubular neck  56  extends longitudinally, distally from the distal extension  51  in longitudinal or axial alignment therewith and has an external diameter, smaller than the external diameter of the distal extension, to be closely received in the rearward section  28  of the outer collet member  22  with a distal end of neck  56  in abutment with the proximal end of inner collet member  26  and with a proximal peripheral edge of the outer collet member  22  in abutment with an external transverse shoulder at the junction of neck  56  with distal extension  51 . The neck  56  is fixedly secured to the outer collet member  22 , such as adhesively, with the lumen or internal passage of neck  56  longitudinally or axially aligned with the internal passage of inner collet member  26 . A passageway  57  in the mid-section  53  extends longitudinally, proximally from end wall  54  in communication with the recess of distal extension  51 . Passageway  57  includes a forward passageway portion or part longitudinally or axially aligned with the recess of distal extension  51  and a rearward passageway portion or part having a longitudinal axis disposed at a minimal acute angle with a longitudinal axis of the forward passageway portion. According to a preferred embodiment, the longitudinal axis of the rearward passageway portion is disposed at an angle of 15° to the longitudinal axis of the forward passageway portion. The rearward passageway portion of passageway  57  has an outlet along an external surface of midsection  53  to establish communication with the passageway  57  from externally of the handpiece body  12 . The rearward passageway portion of passageway  57  receives a distal end of a suction tube  58 . Suction tube  58 , which is preferably made of stainless steel, has a distal tube segment terminating distally at the distal end received in passageway  57  and a proximal tube segment terminating proximally at an open proximal end for being coupled with a standard suction canister. The distal end of the suction tube is secured in passageway  57 , such as adhesively, with the distal end of the suction tube located at the junction of the forward passageway portion with the rearward passageway portion. The distal segment of tube  58  is longitudinally or axially aligned with the rearward passageway portion of passageway  57 . The proximal segment of tube  58  is disposed parallel with the forward passageway portion of passageway  57  and has a plurality of truncated conical configured barbs  59  adjacent the open proximal end thereof for connection with the suction canister. As shown in FIG. 4, three barbs  59  of increasing diametric size are arranged on tube  58  in order of size with the diametrically smallest barb disposed closest to the open proximal end of the suction tube. The recess of proximal extension  52  has a uniform diameter forward recess section and a uniform diameter rearward recess section, larger in diameter than the forward recess section, longitudinally or axially aligned with one another. An internal, transverse shoulder  60  is disposed in the proximal extension  52  at the junction of the forward and rearward recess sections. The transfer body  49  can have a plurality of external oblong recesses as shown in FIG. 1, the recesses extending part way through the thickness of the wall of the transfer body to facilitate manual grasping or gripping of the transfer body during use. 
     Drive unit  50 , also shown in FIG. 4, includes a front drive shaft  61  disposed in the recess of distal extension  51  and a rear drive shaft  62  disposed in the recess of proximal extension  52 . Front drive shaft  61 , shown in FIG. 5, carries or is formed with a gear  63  and has a first cylindrical portion of uniform external diameter extending distally from gear  63  and a second cylindrical portion of uniform external diameter, smaller than the external diameter of the first cylindrical portion, extending distally from the first cylindrical portion in longitudinal or axial alignment therewith. An external, transverse shoulder  64  is defined on the front drive shaft  61  at the junction of the first and second cylindrical portions. Gear  63  has an external diameter or size greater than the external diameter of the first cylindrical portion and has a plurality of gear teeth  65  parallel with a longitudinal axis of the front drive shaft  61 . A longitudinal bore  66  is formed entirely through the front drive shaft  61  and includes a distal bore section of uniform diameter extending part way through the second cylindrical portion and a proximal bore section of uniform diameter, smaller than the diameter of the distal bore section, extending longitudinally, proximally from the distal bore section through the remainder of the front drive shaft  61 . A proximally angled or sloping internal shoulder  67  is disposed in bore  66  at the junction of the distal and proximal bore sections. A pair of apertures are formed through the wall of the front drive shaft close to a distal end thereof, the apertures being disposed at 180° spaced locations about the longitudinal axis of front drive shaft  61  to receive drive pins  68 , respectively. Pins  68  protrude externally in a radial direction from the front drive shaft  61  and have inner ends flush with an internal surface of the second cylindrical portion of the front drive shaft  61  and rounded outer ends spaced from an external surface of the second cylindrical portion of drive shaft  61 . The front drive shaft  61  including gear  63  is preferably made of stainless steel, and a proximal face of gear  63  is highly polished for smoothness. 
     Rear drive shaft  62 , as illustrated in FIGS. 6 and 7, carries or is formed with a gear  69  and has a first cylindrical section of uniform external diameter extending proximally from gear  69  and a second cylindrical section of uniform external diameter, smaller than the external diameter of the first cylindrical section, extending proximally from the first cylindrical section in longitudinal or axial alignment therewith such that an external transverse shoulder  70  is defined at the junction of the first and second cylindrical sections. Gear  69  is similar to gear  63  and has a plurality of gear teeth  71  for mating with the gear teeth  65  in driving engagement. Rear drive shaft  62  has an open proximal end communicating with a longitudinal bore  72  extending distally from the open proximal end to terminate at a conical end surface in the second cylindrical section of the rear drive shaft. Opposed slots  73  are formed through the wall of the second cylindrical section of rear drive shaft  62  at 180° spaced locations about a longitudinal axis of the rear drive shaft. Slots  73  communicate with bore  72  and have open proximal ends communicating with the open proximal end of the rear drive shaft and arcuate distal edges disposed proximally of the conical end surface of bore  72 . Slots  73  define a pair of opposed prongs  74  on rear drive shaft  62 . Each slot  73  has a distal portion of substantially uniform width and an outwardly flared proximal portion of increasing width. Accordingly, each prong  74  terminates proximally at a triangular configured tip  75 . Slots  73  have a width between parallel side edges of the prongs, and the width of the slots  73  is of a size to receive a drive pin of motor assembly  14  as explained further below. The parallel side edges of the prongs are parallel with the longitudinal axis of the rear drive shaft, and the walls forming the prongs are beveled interiorly along the tips  75 . The rear drive shaft  62  including gear  69  is preferably made of stainless steel. 
     Front drive shaft  61  is disposed in the recess of the distal extension  51  of transfer body  49  with the proximal surface of gear  63  adjacent end wall  54  and with the front drive shaft extending into the neck  56  as shown in FIGS. 2 and 4. The bore  66  of front drive shaft  61  is axially aligned with the forward portion of passageway  57 , which is disposed proximally of bore  66 . A retaining ring  76 , such as a stainless steel Smalley retaining ring of Smalley Steel Ring Co., Wheeling, Ill., is disposed on the second cylindrical portion of the front drive shaft  61  distally of external shoulder  64  and is secured in an internal groove or recess formed in the distal extension  51 . A pair of radial shielded bearings  77  are mounted on the first cylindrical portion of front drive shaft  61 , and a washer spring  78  is disposed around the front drive shaft  61  between retaining ring  76  and a distalmost bearing  77 . A rotary seal  79  is disposed in an annular groove or recess extending proximally a short distance from end wall  54  in communication with the distal extension recess. Seal  79  is a two-part seal including an O-ring  79 A and an annular seal ring  79 B disposed between the O-ring  79 A and the proximal surface of gear  63 . The O-ring and seal ring are made of compressible materials; and, preferably, the O-ring  79 A is made of 5-148 EPR and the seal ring  79 B is made of mineral filled PTFE. The gear  63  is pre-loaded against seal  79  such that the proximal surface of gear  63  is in direct contact with the seal ring  79 B and does not contact the end wall  54 . Accordingly, there is a small gap or space between the proximal of gear  63  and the end wall  54  to eliminate metal to metal contact. 
     The front drive shaft  61  is mounted for rotation within the transfer body  49  with the drive pins  68  disposed in neck  56  for being coupled with a hub of a hollow, tubular or cannulated surgical blade which is to be driven by the drive unit  50 . When a blade is coupled to the front drive shaft  61 , the lumen or hollow interior of the blade and its hub will be longitudinally or axially aligned with the bore  66  which, in turn, is longitudinally aligned with the forward portion of passageway  57  such that bore  66  and passageway  57  together define a continuous, substantially straight suction channel in the handpiece body disposed proximally of the blade for evacuating anatomical tissue cut by the blade from the handpiece body  12 . The suction channel is substantially straight; that is, a substantial portion of the length of the suction channel is linear and coaxial with the blade. Only the rearward passageway portion of passageway  57 , which accounts for a minimal portion of the length of the suction channel in the handpiece body is disposed at a minimal angle with the blade. The suction channel is therefore coaxial or linear with the blade from the blade up to the distal end of the suction tube  58 . Accordingly, evacuation of tissue through the blade and the handpiece body is along a straight path up to the suction tube. Areas of turbulence in the suction channel are minimized such that the potential for evacuated material to become clogged within the handpiece is eliminated or greatly minimized. 
     As shown in FIGS. 2 and 4, rear drive shaft  62  is disposed in the recess of proximal extension  52  with a distal surface of gear  69  spaced slightly from end wall  55  and with teeth  71  in driving engagement with teeth  65 . Prongs  74  are disposed in the rearward recess section of the proximal extension  52 . A pair of radial shielded bearings  77 ′ are mounted on the first cylindrical section of rear drive shaft  62 . A retaining ring  76 ′, similar to retaining ring  76 , is disposed around the second cylindrical section of rear drive shaft  62  proximally of external shoulder  70  and is fixedly secured in an internal groove or recess formed in the proximal extension  52 . A washer spring  78 ′, similar to spring  78 , is disposed around the rear drive shaft between a proximal most bearing  77 ′ and the retaining ring  76 ′. 
     The motor enclosure  20  is preferably made of stainless steel or titanium and includes an elongate tubular member of uniform external diameter having a tubular neck  80  of smaller external diameter extending distally therefrom in longitudinal or axial alignment as shown in FIG.  2 . An internal shoulder  81  and an external shoulder  82  are defined at the junction of neck  80  with the elongate tubular member. Neck  80  is received in the rearward recess section of proximal extension  52  with a distal end of neck  80  in abutment with the internal shoulder  60  of proximal extension  52  and with a proximal end of proximal extension  52  in abutment with the external shoulder  82  of motor enclosure  20 . Neck  80  is secured to the transfer body  49 , such as adhesively, and the prongs  74  of the rear drive shaft  62  are disposed within the neck  80  with tips  75  thereof disposed distally of internal shoulder  81 . The motor enclosure  20  has an open proximal end circumscribed by a smaller diameter, annular proximal rim and has an external thread  83  extending distally from the proximal rim. The motor enclosure  20  is longitudinally or axially aligned with the rear drive shaft  62  allowing motor assembly  14  to be coupled with the rear drive shaft in driving engagement when the motor assembly is installed or inserted into the motor enclosure  20  via the open proximal end thereof. A slot or keyway  85 , shown in FIG. 1, is formed in the proximal end of the motor enclosure  20  for receiving a key or protrusion of motor assembly  14  as explained further below. Keyway  85  has an oblong configuration with a central longitudinal axis parallel to the longitudinal axis of rear drive shaft  62 . Keyway  85  has an open proximal end and an arcuate distal edge. Keyway  85  is aligned with the longitudinal axis of rear drive shaft  62 ; that is, longitudinal central axes of keyway  85  and rear drive shaft  62  are contained in the same plane and such plane contains the longitudinal axis of the motor enclosure  20 . 
     Motor assembly  14 , as shown in FIG. 2, includes an elongate, cylindrical motor housing  86 , a motor  87 , shown in FIG. 9, disposed within the housing  86  and an electrical connector  88  electrically connected with motor  87 . Motor  87  includes a motor shaft  89  extending distally from a front end of motor housing  86  in longitudinal or axial alignment therewith. As shown in FIGS. 2 and 8, a pair of cylindrical drive pins  90  protrude from the motor shaft  89  in a radial direction at 180° spaced locations about a longitudinal axis of the motor shaft  89  for being received in slots  73  in driving engagement with prongs  74 . As shown in FIG. 9, the motor housing  86  has a diametrically enlarged, open rear end with an internal thread for threaded connection to connector  88 . Motor  87  is preferably a three-phase, brushless, DC motor having Hall Effect sensors, such as that of Harowe Servo Controls, Inc. of West Chester, Pa. 
     The electrical connector  88  is illustrated in FIGS. 10-12 and includes a backshell  91  having a cylindrical main body portion and an externally threaded neck of smaller diameter extending distally from the main body portion. The externally threaded neck has an external size to be threadedly received by the internally threaded rear end of the motor housing  86  as shown in FIG.  9 . The main body portion of backshell  91  has an external diameter or size that is the same or substantially the same as the external diameter or size of the rear end of motor housing  86  such that the backshell is diametrically flush with the motor housing. A raised key or protrusion  92  protrudes externally from the main body portion of backshell  91 , the key  92  extending longitudinally, distally from a proximal peripheral edge of backshell  91 . Key  92  has a configuration and size to mate with keyway  85  of motor enclosure  20 ; however, the height of key  92  is less than the height of keyway  85  to allow a key of an installation device to be received in keyway  85  simultaneously with key  92  as explained further below. A longitudinal axis of key  92  is disposed transverse or perpendicular to a common longitudinal axis of drive pins  90  such that the drive pins  90  are aligned with slots  73  when key  92  is aligned with keyway  85 . Accordingly, key  92  and keyway  85  comprise an alignment mechanism for ensuring proper alignment of the motor assembly in the handpiece body. A cylindrical recess  93  is formed in the main body of backshell  91 , the recess  93  extending distally from the proximal peripheral edge of the backshell to terminate at a base wall  94  in the backshell main body. A semi-cylindrical polarizing insert  95  is disposed in recess  93 , the insert  95  extending proximally from base wall  94  to terminate at a planar surface flush with the proximal peripheral edge of the backshell main body portion. Insert  95  has a diameter smaller than the diameter of recess  93 , and the insert  95  is disposed in the recess  93  with its diameter aligned with the diameter of recess  93 . Accordingly, there is a semi-circumferential gap or space between a curved outer surface of insert  95  and a curved inner surface of the wall forming the backshell main body portion. A plurality of contacts  96  are mounted in the backshell  91  and have distal ends protruding longitudinally, distally from a forward surface of the backshell neck. Some of the contacts  96  extend longitudinally through the backshell  91  to terminate at proximal ends forming pins  97 , and the remaining contacts  96  extend longitudinally through the backshell to terminate at proximal ends forming receptacles  98  to provide a male/female connector. As shown in FIG. 12, ten contacts  96  are arranged in the backshell  91  with five of the contacts  96  forming receptacles  98  in polarizing insert  95 , and the remaining five contacts  96  forming pins  97  protruding proximally from base wall  94 . Pins  97  are disposed in recess  93  in symmetrical or mirror image arrangement with receptacles  98 . The distal ends of contacts  96  are designed, such as with slots, to be soldered to wire leads  99  of motor  87  as shown in FIG.  9 . The pins  97  and receptacles  98  are designed to accept a polarized plug of an electrical cord assembly for connection to a power console for supplying electricity to motor  87  as explained further below. According to a preferred embodiment, connector  88  is a custom ERY-2C electrical connector of LEMO USA. 
     The handpiece body  12  is preferably made of durable, medically acceptable materials, such as stainless steel or hard coat anodized aluminum or titanium, for example, capable of being sterilized to medical standards, such as by steam or flash autoclaving, gas sterilization and/or soaking in a disinfectant solution. Accordingly, the handpiece body  12  is designed for repeated use. The motor assembly  14  is removably installed in handpiece body  12  allowing the motor assembly  14  to be removed from the handpiece body  12  prior to sterilization of the handpiece body and to be reinstalled in the sterilized handpiece body  12  prior to use. The motor assembly  14  can be non-sterile such that the motor assembly is not subjected to sterilization procedures that would reduce the reliability and/or life of the motor. According to a sterile transfer method of the present invention, a non-sterile motor assembly  14  is installed in the sterile handpiece body  12  without contaminating the sterile handpiece body as explained below. 
     The motor assembly  14  is installed in the handpiece body  12  with the key  92  of connector  88  disposed in the keyway  85  of motor enclosure  20 . Accordingly, the drive pins  90  will be disposed in the slots  73  in driving engagement with prongs  74 . The front end of motor housing  86  will be in abutment with the internal shoulder  81  of the motor enclosure  20  and the connector backshell  91  will be flush with the proximal rim of the motor enclosure  20 . 
     The motor  87  is powered by a software controlled power console via an electrical cord assembly  111  coupled with connector  88  and the power console as shown in FIG.  13 . Cord assembly  111  comprises a length of shielded electrical cable or cord  113  having a first end carrying a first plug  115  for being coupled with electrical connector  88  and having a second end carrying a second plug P for being coupled to the power console. Cable  113  can be designed in many various ways and can include various types of shielded electric cable, such as that of W. L. Gore &amp; Associates, Inc. of Phoenix, Ariz., having conductors for transmitting electricity from the power console PC to the motor  87 . As shown in FIG. 14, plug  115  is designed as a male/female plug for being coupled with electrical connector  88  and has a cylindrical forward end with a planar end surface  117  for abutting base wall  94  of connector  88 . A polarizing recess  119  corresponding to polarizing insert  95  is formed in the plug  115 . A plurality of receptacles  121  are disposed in the plug  115  corresponding to pins  97  of electrical connector  88 , and a plurality of pins  123  are disposed in the polarizing recess  119  corresponding to receptacles  98  of connector  88 , the receptacles  121  and pins  123  being electrically connected with conductors of cable  113 . Accordingly, the plug  115  can be plugged into the electrical connector  88  with the polarizing insert  95  of the connector received within the polarizing recess  119  of the plug with the pins  97  of the connector disposed within the receptacles  121  of the plug and the pins  123  of the plug disposed within the receptacles  98  of the connector. As shown in FIGS. 13 and 14, a locking or retaining ring  125  is concentrically disposed over the plug  115  and has an internal annular protrusion  127  disposed proximally of an annular abutment  129  of plug  115 . The locking ring carries an internal seal  184  disposed proximally of protrusion  127  to keep out moisture. The locking ring  125 , which is movable longitudinally relative to plug  115 , is rotatable relative to plug  115  and is internally threaded along a distal end thereof for threaded engagement with the thread  83  of motor enclosure  20 . Accordingly, a circumferential or annular gap or space is disposed between plug  1 l 5  and locking ring  125  for accommodating the proximal end of the motor enclosure  20  when the locking ring is threaded thereon. The cord assembly  111  is designed and constructed to be sterilized, such as via steam autoclave, for example, to medical standards for repeated use. 
     FIGS. 15-17 illustrate a reusable motor installation device  100  for use in the sterile transfer method according to the present invention. Motor installation device  100  is in the nature of a funnel  100  including a flared or truncated conical head  102  having a relatively wide inlet end and a relatively narrow outlet end opposite the inlet end and a tubular neck  103  extending longitudinally, centrally from the head  102  in communication with the outlet end. The wall forming head  102  is exteriorly beveled or angled at the junction of the head  102  with the tubular neck  103  to define a planar end surface  104  parallel to a plane containing a terminal circumferential or peripheral edge  105  at the inlet end of head  102 . The tubular neck  103  is concentrically arranged with the head  102  and extends longitudinally therefrom to terminate at an open, free end that is externally threaded or ribbed as shown at  106  in FIG. 15. A circumferential lip  107  is disposed at the junction of head  102  with the neck  103 , i.e. at the outlet end of head  102 , and a notch  108  is formed in the lip  107  such that the lip is circumferentially broken or discontinuous. The lip  107  protrudes inwardly such that the outlet defined by lip  107  at the outlet end of head  102  is diametrically or circumferentially smaller than the lumen of neck  103 . A key or protrusion, such as a dowel pin  109  extends through the wall forming the neck in longitudinal alignment with the notch  108 . The key  109  is spaced longitudinally from the notch  108  and protrudes into the lumen of neck  103 . The distance that key  109  protrudes into the neck  103  is selected to allow keys  92  and  109  to be disposed in the keyway  85  simultaneously when the motor assembly  14  is inserted into the handpiece body  12  through funnel  100  according to the sterile transfer method explained further below. The distance that key  109  is spaced longitudinally from seal  107  is selected such that the key  109  is disposed in the keyway  85  with the annular proximal rim of the motor enclosure  20  in abutment with lip  107  when the funnel is placed over the motor enclosure to install the motor assembly. 
     The neck  103  has a plurality of slots  101  formed therein, the slots  101  being equally spaced about a longitudinal axis of funnel  100 . As shown in FIG. 18, four slots  101  are separated from one another by triangular shaped bridge segments  110  of neck  103 . As shown in FIG. 15, slots  101  are spaced longitudinally from key  109 , the slots  101  being disposed between key  109  and the open free end of neck  103 . As shown in FIG. 19, a deformable O-ring  112  is positioned externally over neck  103  to be received in slots  101 . When the O-ring is received in slots  101  as shown in FIGS. 15,  16  and  17 , the O-ring is deformed to assume a somewhat square configuration with segments  114  of the O-ring protruding into the lumen of neck  103 . Funnel  100  is made of a suitable medically acceptable material, such as titanium or stainless steel, and is capable of being sterilized along with O-ring  112  assembled thereon, such as by flash autoclaving, gas sterilization and/or soaking to medical standards for repeated use. 
     Prior to use, the funnel  100 , electrical cord assembly  111  and the handpiece body  12 , without the motor assembly  14  received in the motor enclosure  20 , are medically sterilized such as via flash autoclaving, gas sterilization and/or soaking. The thusly sterilized components are handled by sterile operating personnel in a sterile operating field prior to surgery. According to the sterile transfer method, the handpiece body  12  is held with the open proximal end of motor enclosure  20  facing upwardly, and the neck  103  of funnel  100  is placed over the open proximal end of the motor enclosure  20 . The funnel  100  is rotated relative to the motor enclosure  20  until the key  109  is aligned with the keyway  85 . The key  109  will then drop into the keyway  85  until the proximal rim of the motor enclosure  20  is in abutment with the lip  107 . The O-ring segments  114  grip the handpiece body  12  and resist removal of the funnel  100  from the handpiece body such that the funnel remains in place on the handpiece body even if the handpiece body is turned upside down. Accordingly, the funnel  100  will be locked in place on the handpiece body  12  with the key  109  protruding part way into the keyway  85 . The non-sterile motor assembly  14 , which is handled separately by operating personnel who can be non-sterile, is inserted, shaft end first, through the inlet end of funnel  100  and is rotated until the key  92  on the electrical connector  88  is aligned with the notch  108  in the lip  107 . Accordingly, the key  92  will be aligned with the keyway  85 , and the motor assembly  14  will pass through the neck of funnel  100  into motor enclosure  20  since the key  92  passes through the notch  108  and enters the keyway  85 . The drive pins  90  will enter the slots  73  in driving engagement with prongs  74 , the triangular shaped tips  75  of the prongs  74  providing a self-centering function to facilitate entry of the drive pins  90  in the slots  73 . The funnel  100  is then manually withdrawn or removed from the handpiece body  12 , overcoming the gripping force of O-ring  112  such that the key  109  is withdrawn from the keyway  85 . The motor assembly  14  is now properly installed within the handpiece body  12  without compromising the sterility of the handpiece body. 
     Once the motor assembly  14  has been properly installed in the handpiece body  12 , the sterile plug  115  is plugged into the electrical connector  88  with a press fit with the locking ring  125  disposed in a proximal longitudinal position relative to plug  115  to allow the polarizing insert  95  to enter the polarizing recess  119  causing pins  97  of the electrical connector to enter the receptacles  121  of the plug and causing the pins  123  of the plug to enter the receptacles  98  of the connector. The locking ring  125  is then rotated in a first rotational direction relative to the plug  115  to threadedly engage the proximal end of the motor enclosure  20 . As the locking ring  125  is threaded over the proximal end of the motor enclosure, the locking ring is moved longitudinally, distally relative to the plug  115  to a distal longitudinal position. The locking ring is rotated and, therefore, is moved longitudinally until the threads of the locking ring and the motor enclosure, respectively, are fully engaged. The proximal end of the motor enclosure  20  is then held between the plug  115  and the locking ring  125 , with the locking ring  125  preventing withdrawal of the plug  115  from the connector  88  and, therefore, preventing withdrawal of the motor assembly  14  from the handpiece body  12 . The plug P is plugged into the power console, which is utilized to supply electric power to motor  87  to rotate motor shaft  89 , operation of the console being controlled by the surgeon such as via a foot switch or pedal for the console or directly from the console. Motor shaft  89  rotates rear drive shaft  62  which in turn rotates front drive shaft  61  via gears  63  and  69 . Front drive shaft  61  in turn rotates a surgical blade drivingly engaged therewith to cut anatomical tissue. The front drive shaft  61  can be rotated via the motor assembly for full rotational movement along 360° continuously in the same direction and/or for oscillatory rotational movement in reverse directions along less than 360°. 
     FIG. 20 illustrates a surgical blade assembly  200  for use with the handpiece  10 . Blade assembly  200  includes an outer blade  202 , a hub  204  mounting a proximal end of the outer blade, an inner blade  206  for being disposed in the outer blade with the inner blade passing through hub  204 , and a hub  208  mounting a proximal end of the inner blade. Outer blade  202  includes an elongate tubular member having an open proximal end and an open distal end or tip  210  carrying a cutting edge  212 . As shown in FIG. 21, hub  204  for outer blade  202  includes a forward hub part  214  and a rearward hub part  216 . Forward hub part  214  includes a distal cylindrical main body portion tapering to a smaller external diameter proximal cylindrical portion. A longitudinal passage  218  extends entirely through the forward hub part  214  and includes a forward passage section of uniform diameter, an intermediate passage section of uniform diameter greater than the diameter of the forward passage section, and a rearward passage section of uniform diameter greater than the diameter of the intermediate passage section. An internal transverse shoulder  220  is defined at the junction of the intermediate and rearward passage sections, and an annular seal  222  is disposed in the passage  218  in abutment with shoulder  220 . An angular extension  224  protrudes angularly, proximally from the forward hub part  214  and has a longitudinal passage extending entirely therethrough in communication with the passage  218 . Extension  224  has an open free end formed with a barb  226  for being coupled with an irrigation supply tube. Rearward hub part  216  includes a distal cylindrical section, a proximal cylindrical section having an external diameter greater than the diameter of the distal cylindrical section and an annular flange  228  disposed between the distal and proximal cylindrical sections. A longitudinal passage  230  of uniform diameter extends entirely through the rearward hub part  216 . A plurality of partial spherical recesses  232  are formed along an outer forward edge or corner of flange  228  at 30° spaced locations about a longitudinal axis of rearward hub part  216 . The rearward hub part  216  is assembled to the forward hub part  214  with the distal cylindrical section of the rearward hub  216  part secured in the rearward passage section of the forward hub part  214  with a distal end of the rearward hub part  216  in abutment with seal  222 . The distal section of the rearward hub part can be secured in the rearward passage section of the forward hub part in many various ways, such as adhesively. With the rearward hub part  216  assembled to the forward hub part, the passages  218  and  230  are longitudinally or axially aligned to form a continuous longitudinal passage through hub  204 . The open proximal end of the outer blade  202  is secured, such as adhesively, in the forward passage section of the forward hub part  214  with the lumen or internal passage of the outer blade  202  longitudinally or axially aligned with the passage through hub  204 . A hole or aperture is formed in the outer blade  202  in alignment with the longitudinal passage of angular extension  224  to establish communication between the passage of the angular extension and the lumen of outer blade  202 . 
     Inner blade  206  is illustrated in FIG.  22  and includes an elongate tubular member having an open proximal end  233  and an open distal end or tip  234  carrying a cutting edge  236  designed to cooperate with cutting edge  212  to cut anatomical tissue. Hub  208  for inner blade  206  includes a cylindrical body having a passage  238  extending longitudinally entirely therethrough. Passage  238  has a forward passage portion and a rearward passage portion larger in diameter than the forward passage portion. An internal transverse shoulder  240  is defined at the junction of the forward and rearward passage portions. As shown in FIGS. 22 and 23, a plurality of oblong slots  242  are formed in a proximal end of hub  208  at 90° spaced locations about a longitudinal axis of hub  208  with the slots  242  extending longitudinally, parallel to the longitudinal axis of hub  208  to define prongs  244 . Each slot  242  has a distal portion of uniform width and a proximal portion of increasing width in the proximal direction. Accordingly, the proximal portions of slots  242  flare out from the distal portions thereof such that the prongs  244  have triangular shaped tips  246 , the prongs  244  being similar to the prongs  74 . The hub  208  and the prongs  244  are designed to be disposed in the handpiece  10  with the drive pins  68  of the front drive shaft  61  disposed in a pair of opposed slots  242  in driving engagement with prongs  244 . An annular or cylindrical seal  248  is disposed within passage  238  at a proximal end of groove  249  along a forward surface thereof. A coil spring  250  is concentrically disposed in passage  238  and is mounted in compression between shoulder  240  and seal  248  with an end of the spring  250  being disposed in the groove  249 . The open proximal end  233  of the inner blade  206  is disposed in the passage  238  to terminate proximally of seal  248  and is secured, such as adhesively, in passage  238  with the inner blade passing concentrically through spring  250 . Preferably, the blades are made of stainless steel and the hubs are made of plastic, such as ABS resin, for disposability or single patient use. 
     The outer blade  202  is assembled with the inner blade  206  as shown in FIG. 20 with the inner blade  206  passing through hub  204  to align the cutting edges  212  and  236  and with hub  208  disposed proximally of hub  204 . The inner blade  206  is of a size to be closely received within outer blade  202  and hub  204  while allowing the inner blade to be rotated relative to the outer blade to move the cutting edge  236  past the cutting edge  212  to cut anatomical tissue. The blade assembly  200  is coupled with the handpiece  10  by moving the middle collet member  24  longitudinally, proximally relative to the outer collet member  22  to the retracted position causing ball bearings  47  to be aligned with the forward passage segment of the middle collet member. The hubs  204  and  208  are introduced through the aperture  44  in the middle collet member  24  and are moved longitudinally to enter the passage of the inner collet member  26  such that the drive pins  68  of the front drive shaft  61  enter the slots  242  of hub  208 , the triangular tips  246  of prongs  244  providing a self-centering function facilitating entry of the drive pins  68  into a pair of opposed slots  242 . Flange  228  enters the passage of the inner collet member  26 , causing the ball bearings  47  to be moved outwardly from holes  46 . With the hubs  204  and  208  fully inserted in the handpiece  10 , a proximal surface of flange  228  will be in abutment with internal shoulder  45 , and the partial spherical recesses  232  will be in alignment with holes  46 . The middle collet member  24  is released, causing the middle collet member to be returned to the extended position due to the bias of spring  48 . Return of the middle collet member to the extended position causes the ball bearings  47  to be moved inwardly into holes  46  and the partial spherical recesses  232  aligned therewith. Accordingly, flange  228  of hub  204  is prevented from moving distally and rotationally by ball bearings  47  and is therefore locked in place within the handpiece  10 . The hub  208  cannot enter the rearward hub  204 ; and, accordingly, the hub  208  is also locked in place within the handpiece  10 . The extension  224  of hub  204  is connected with an irrigation supply tube for supplying irrigation fluid between the outer blade and the inner blade, the seal  222  preventing egress of irrigation fluid proximally therepast. The spring biased seal  248  of hub  208  allows some tolerance between the hub  208  and the front drive shaft  61  to maintain proper alignment therewith. Preferably, the blade assembly is provided in a sterile condition for single patient use and; since the seals  222  and  248  are disposed in the hubs  204  and  208 , respectively, and not in the handpiece, they are not subjected to the rigors of medical resterilization. With the blade assembly  200  coupled with the handpiece  10 , rotation of the front drive shaft  61 , as controlled by the power console, causes the inner blade  206  to be rotated within and relative to the outer blade  202  to move cutting edge  236  past cutting edge  212  to cut anatomical tissue through the open distal ends of the blades. Irrigating fluid is supplied at the cutting tips  210  and  234  via extension  224  and the lumen of outer blade  202 , such fluid passing through the hole or aperture in the outer blade to flow between the inner and outer blades. Anatomical tissue cut by the blades will be aspirated or evacuated through the inner blade member  206  and the handpiece  10  for collection in the suction canister coupled with suction tube  58 . The seal  79  prevents material being evacuated from crossing the seal to gears  63  and  69 . 
     FIG. 25 illustrates at  379  an alternative seal forming a seal with the proximal surface of the gear of the front drive shaft. Seal  379  is disposed in an annular groove or recess of transfer body  49  and includes an annular seal member  379 A having a U-shaped configuration in cross-section with spaced legs  380 A and an annular spring  379 B disposed between legs  380 A. The space between legs  380 A is disposed along an outer periphery of the seal member  379 A to receive spring  379 B, which has an oblong configuration in cross-section. A forward surface of seal member  379 A is in contact with the proximal surface of gear  63  such that there is a small air gap between the proximal surface of the gear and the transfer body  49 . Seal  379  functions similar to seal  79  in that the gear  63  is in contact with the seal member  379 A and does not contact the transfer body  49 , and the seal  379  prevents material evacuated from the handpiece from moving therepast. 
     FIG. 25 illustrates a lip seal  400  for use on the front and rear drive shafts. Lip seal  400  includes an annular seal member or ring, preferably made of compressible, deformable material, disposed around front drive shaft  61  between retaining ring  76  and bearings  77 . Seal  400  has a slightly protruding proximal peripheral edge adjacent the distalmost bearing  77 . Seal  400  can be used in place of the washer spring, or the seal  400  can be used in conjunction with a spring, such as a garter spring, a spring being shown within the seal  400  in dotted lines at  478 . Although the seal  400  is illustrated on the front drive shaft  61 , it should be appreciated that a seal  400  can be disposed on the rear drive shaft between the retaining ring and the proximalmost bearing in the same manner as described for the front drive shaft  61 . 
     The handpiece of the present invention is relatively small and lightweight providing many functional benefits for the ENT surgeon as well as other medical specialities. The handpiece can be used with many various interchangeable blades having different cutting tips in accordance with a procedure to be performed. Tissue cut by the blades is evacuated through the handpiece in a substantially in-line or straight path while maintaining a small profile for the handpiece. Since tissue is evacuated along a straight path through the handpiece up to the suction tube, which itself is at a minimal angle, areas of turbulence in the suction channel are reduced such that clogging of tissue in the handpiece body is eliminated or greatly minimized. The reliability and/or life of the motor assembly is greatly increased since the motor assembly is removed prior to sterilization of the handpiece body for reuse and is reinstalled in the sterilized handpiece body prior to surgery without contaminating the handpiece body. Removability of the motor assembly allows various different motor assemblies with different operating speeds and features to be installed in the handpiece in accordance with optimal procedural use. The handpiece according to the present invention can be powered off of its own power console or the existing power consoles of various manufacturers by orienting the output signals of the power consoles for compatibility with the handpiece or by utilizing a motor assembly and/or cord assembly compatible with the power consoles. 
     Other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings, wherein like parts in each of the several figures are identified by the same reference characters.