Patent Publication Number: US-6209886-B1

Title: Resecting tool with independent variable axial extension for tool implements and guide sleeves

Description:
TECHNICAL FIELD 
     This invention relates in general to surgical resecting tools for cutting human bone and in particular to a resecting tool which is capable of a range of independent extension lengths for both the tool implement and its guide sleeve. 
     BACKGROUND ART 
     A surgical resecting tool for cutting human bone uses a detachable motor coupled to the end of a hose to drive a chuck located inside the tool. The chuck engages the shaft of a tool implement which extends from the resecting tool. The distal end of the implement has a tool head which may be configured to perform a variety of procedures. A guide sleeve is used in conjunction with the implement to further support the otherwise cantilevered implement. The guide sleeve also extends from the resecting tool and is concentric with the implement. The motor rotates the chuck to drive the implement at very high rotational speeds within the guide sleeve. 
     In one type of prior art, the chuck was tightened by a threaded nut to frictionally grip the shaft for transmitting torque. In another type of prior art tool, the shaft of the implement has an axial grip feature and a drive feature, such as a flat, that interfaces with and is closely received by a drive key on the chuck inside the resecting tool. These grip and drive features require precise tolerances and axial positioning within the tool when the implement is installed. 
     In some tools, the guide sleeve can be adjusted relative to the resecting implement to vary the axial distance that the guide sleeve extends from the tool. Also, quick-release features are known. Still, improvements to these prior art tools are desired. 
     SUMMARY OF THE INVENTION 
     A resecting tool contains a rotatable chuck inside a base for engaging the drive shaft of a motor. The chuck extends into a tubular casing that has an outer actuator sleeve. The sleeve is limited to rotation relative to the casing and is used to move a pair of locking elements or balls in separate helical slots in the casing. Each ball is seated in a collar that abuts a collet receiver inside the casing. During implement changeover, the collar abuts the collet receiver and acts as a brake to prevent accidental actuation of the chuck and the tool implement. The collet receiver is spring-biased into contact with a first collet which closely receives a tool implement within the resecting tool. The sleeve is used to manipulate the collet to clamp onto and unclamp the tool implement. 
     A collet coupling is located on the front end of the casing and has a collet nut on its forward end. The collet nut houses a second collet with a serpentine cut for engaging and retaining a guide sleeve for supporting the tool implement. Both collets are designed to engage and lock onto tool implements and guide sleeves at variable distances along their axial lengths. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, are attained and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and is therefore not be considered limiting of its scope as the invention may admit to other equally effective embodiments. 
     FIG. 1A is a sectional side view of a rearward portion of a resecting tool with a fully inserted tool implement and guide sleeve, wherein the resecting tool is constructed in accordance with the invention. 
     FIG. 1B is a sectional side view of a forward portion of the tool of FIG.  1 A. 
     FIG. 2A is a sectional side view of the rearward portion of the tool of FIG. 1A with the tool implement and guide sleeve at a minimum insertion distance. 
     FIG. 2B is a sectional side view of the forward portion of the tool of FIG. 1B with each of the tool implement and guide sleeve at a minimum insertion distance. 
     FIG. 3A is an exploded, isometric view of the rearward portion of the tool of FIG. 1A without the tool implement or guide sleeve. 
     FIG. 3B is an exploded, isometric view of the forward portion of the tool of FIG. 1B without the tool implement or guide sleeve. 
     FIG. 4 is a side view of a serpentine collet for the guide sleeve. 
     FIG. 5 is a rear axial view of the collet of FIG.  4 . 
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Referring to FIGS. 1A and 1B, a resecting tool  11  for manipulating a tool implement  13  and guide tube or sleeve  15  is shown. Tool implement  13  has an elongated, thin cylindrical shaft with a tool head  17  on its forward end. Although only one embodiment is shown, tool head  17  may comprise many different forms, depending upon the procedure being performed by the user. Guide sleeve  15  is a thin-walled, cylindrical member which supports the shaft of implement  13  with multiple bearings  19 . Both implement  13  and guide sleeve  15  have smooth exteriors which are closely received within tool  11 . In FIGS. 1A and 1B, implement  13  and guide sleeve  15  are inserted to a maximum depth within tool  11 , as will be described in detail below. 
     As shown in FIGS. 1A and 3A, the rearward end of tool  11  has a cylindrical base  21  with internal threads that attach to a motor  23 . Motor  23  has a concentric drive shaft  25  that engages a chuck or drive coupling  31  located inside base  21 . Coupling  31  has drive members  33  for engaging drive shaft  25 , and a shoulder  34  near its midsection. The forward end of base  21  has a concentric hub  35  with a reduced diameter which defines a shoulder  37  therebetween. 
     Base  21  also contains internal threads  39  and an internal flange  41  located rearward of threads  39  (FIG.  1 A). The rearward end  43  of an elongated, generally tubular casing  45  (FIG. 3A) captures a roller bearing  42  against coupling  31 . Bearing  42  has a lip on its outer race which is engaged by end  43  against flange  41  to prevent the axial movement of bearing  42 . The inner race of bearing  42  rests against an outer surface of coupling  31  and its shoulder  34 . Casing  45  has external threads  47  for engaging threads  39  on base  21 . End  43  and threads  47  are located on an elongated hub  49  which protrudes rearward from casing  45 . Hub  49  has a central flange  51  which defines a recess  53  on its forward side for containing an O-ring  55 . 
     A large diameter actuator sleeve  61  surrounds hubs  35 ,  49  and has an annular boss  63  on its interior surface (FIGS.  1 A and  3 A). The inner surface of boss  63  smoothly engages the outer surface of hub  49 . The forward end of boss  63  abuts flange  51  on hub  49  (FIG.  3 B), and the rearward end of sleeve  61  abuts shoulder  37  (FIG. 3A) to prevent the axial movement of sleeve  61 . Sleeve  61  has an annular notch  65  on its inner rearward end for capturing an O-ring  67  against shoulder  37  and hub  35 . The rearward end of the inner surface of sleeve  61  is smooth and closely receives the outer surface of hub  35  for smooth rotation of sleeve  61  relative to casing  45 . The forward end of the inner surface of sleeve  61  is also smooth and closely receives the outer diameter of casing  45  and flange  51  to capture O-ring  55  in recess  53 . Boss  63  also has a pair of axial grooves  69  which are located 180 degrees apart from each other. Each groove  69  closely receives the upper end of a locking element or actuator ball  71 . 
     Referring to FIGS. 1A and 3B, each ball  71  is movably mounted in its own helical slot  73  in hub  49  of casing  45 . Slots  73  have an axial dimension or width which is slightly greater than the diameter of balls  71 . Each slot  73  has a circumferential length of approximately 120 degrees. A locking circular detent  74  (one shown) is located on each end of each slot  73  for capturing balls  71 . Slots  73  extend completely through hub  49  to expose balls  71  to the interior of casing  45 . The lower end of each ball  71  is seated in a concave recess  75  in a hollow collar  77 . Thus, the radial distance from the bottom of recess  75  to the top of each groove  69  is slightly greater than the diameter of balls  71 . Collar  77  is located within casing  45  and has an outer diameter that is closely received by the inner diameter of hub  49 . Rotating sleeve  61  causes balls  71  to move along helical slots  73 , which in turn moves collar  77  forward or rearward. 
     As shown in FIGS. 1A and 3A, an elongated, cylindrical tool collet receiver  81  is located radially inward of but does not touch casing  45 . Collet receiver  81  is hollow and has an external flange  83  on its rearward end. The forward side of flange  83  engages the rearward end of collar  77 . The rearward side of flange  83  abuts the forward end of a rearward compression spring  85 . The rearward end of spring  85  abuts a spacer  87 , which itself abuts the inner race of bearing  42  and a shoulder  89  on coupling  31 . 
     Spring  85  surrounds the rearward end of an elongated, generally cylindrical tool implement collet  91  which also abuts spacer  87 . Collet  91  is hollow and has internal threads  93  near its rearward end for engaging a set of external threads  95  on coupling  31 . The shaft  97  of coupling  31  is closely received within collet  91 . The forward end of shaft  97  abuts the rearward end of a tubular spacer  99  which is also closely received by the interior of collet  91 . The forward end of spacer  99  acts as a backstop for the maximum insertion depth of tool implement  13  and the rearward end of an inner compression spring  101 . The forward end of spring  101  abuts a shoulder  103  in collet  91  to maintain spacer  99  in position. Spring  101  serves only as a positioner for spacer  99  and essentially does not compress or expand during operation. 
     The front end of collet  91  is split with axial grooves  105  for adjustably engaging the shaft of tool implement  13 . Thus, collet  91  will contract and expand radially to frictionally engage and release, respectively, implement  13 . Collet  91  also has an external taper  107  which transitions into a relatively small diameter neck  109  on the front end of collet  91 . Taper  107  slidingly engages a taper  110  on the inner surface of the front end of collet receiver  81 . The inner race of a forward roller bearing  111  radially supports neck  109  (FIGS.  1 A and  3 B). The outer race of bearing  111  is captured in an axial hole  113  in a collet coupling  115 . From front to back, a seal  117 , curved disc spring  119 , and shim  121  are located between a shoulder  123  in hole  113  and the front side of bearing  111 . The rearward end of collet coupling  115  abuts the forward end of a large compression spring  125 . The rearward end of spring  125  abuts the forward end of collar  77 . Spring  125  is located inside casing  45  and it surrounds a substantial portion of the axial length of collet receiver  81 . Springs  125  and  85  (described above) provide counterbalancing axial forces against collar  77  and flange  83 . Note that in the fully inserted position, guide sleeve  15  abuts a shoulder  127  located inside collet coupling  115  (left edge of FIG.  1 A). When collar  77  moves rearward due to rotation of sleeve  61  and balls  71 , collet receiver  81  moves rearwared, allowing the front end of collet  91  to expand and release implement  13 . 
     Referring now to FIGS. 1B and 3B, collet coupling  115  has a set of external threads  131  on its rearward end for engaging internal threads  133  on the forward end of casing  45 . The front rim of casing  45  abuts the rear surface of an external flange  135  on collet coupling  115 . A radial set screw  137  locks collet coupling  115  to casing  45 . Collet coupling  115  also has external threads  139  on its forward end for engaging the internal threads  141  of a collet nut  143 . The inner surface on the rearward end of collet nut  143  closely receives a hub  145  on collet coupling  115 . Collet nut  143  also contains a pointed, inner annular rib  151  near its front end. Rib  151  is conical in profile and is provided for engaging an external, annular groove  153  in a guide sleeve collet  155  (FIG.  1 B). Rib  151  releasably engages groove  153  so that collet  155  may be readily snapped into and out of collet nut  143  for easy cleaning. 
     As shown in FIGS. 4 and 5, collet  155  has a cylindrical bore  157  and a serpentine cut  158  that allows it to adapt to and closely receive guide sleeves  15  of various sizes. The shape of cut  158  increases the contact area between collet  155  and guide sleeve  15  to provide superior grip therebetween. When collet nut  143  is moved, collet  155  will contract or expand radially to frictionally engage and release, respectively, guide sleeve  15 . The exterior of collet  155  has an axial taper  159  and decreases in diameter from front to back such that it is closely received by the tapered bore  161  at the front end of collet coupling  115 . Like taper  159 , the inner diameter of bore  161  decreases from front to back. Tightening collet nut  143  causes collet  155  to contract radially. 
     Prior to the installation of tool implement  13  and guide sleeve  15 , each collet  91 ,  155  of resecting tool  11  must be set to its disengaged or unlocked position. Guide sleeve collet  155  is prepared to receive guide sleeve  15  by rotating collet nut  143  to move axially toward flange  135  on collet coupling  115 . This motion causes the tapered surfaces  159 ,  161  of collet  155  and collet coupling  115 , respectively, to slightly increase in diameter due to the spring-like properties of the serpentine cut in collet  155 . 
     With collet  155  in this position, guide sleeve  15  may be inserted into the hole on the front end of collet nut  143  to any depth from the minimum depth depicted in FIG. 2B (this is also the maximum axial extension of sleeve  15  out of tool  11 ), to the maximum depth depicted in FIGS. 1A and 1B (the minimum axial extension of sleeve  15 ), depending upon the procedure being performed by the user. Thus, the axial extension of guide sleeve  15  may be varied by approximately one to two inches. At the minimum depth, the rearward end of guide sleeve  15  is substantially radially aligned with the rearward end of collet  155 . This position assures full surface area contact between the inner surface of collet  155  and guide sleeve  15 . At the maximum depth, the rearward end of guide sleeve  15  abuts shoulder  127  in collet coupling  115 . At either depth, the surface area of contact between collet  155  and guide sleeve  15  is the same. 
     When guide sleeve  15  is at the desired depth, collet nut  143  is rotated in the opposite direction (away from flange  135  of collet coupling  115 ) until guide sleeve  15  is tightly clamped inside tool  11 . By moving collet nut  43  to its locked position, the internal taper  161  in collet coupling  115  presses on the external taper  159  on collet  155 , thereby overcoming its spring-like resilience to clamp it down on guide sleeve  15 . The rib  151  inside collet nut  143  stays seated in the groove  153  in collet  155  to retain collet  155  in the proper position inside collet nut  143  and collet coupling  115  at all times. 
     Resecting tool  11  is similarly prepared to receive tool implement  13  by rotating sleeve  61  to its unlocked position (FIG.  2 A). Sleeve  61  is limited to rotational motion and it and casing  45  have external markings (not shown) which permit the user to select the desired position. With sleeve  61  in the unlocked position, balls  71  are lodged in the detents  74  on the rearward end of slots  73 . Since detents  74  are slightly misaligned with the path defined by slots  73 , the user will detect a tactile verification of the visual indication of the markings on sleeve  61  and casing  45 . As balls  71  move to this position, they are forced to move radially by the side walls of grooves  69  in sleeve  61 . Balls  71  also move in an axially rearward direction in their helical slots  73  until they seat in the rearward detents  74 . Thus, the grooves  69  in sleeve  61  also allow for the axial motion of balls  71 , and the slots  73  also allow for their radial motion. Casing  45  is stationary at all times. In this unlocked position, spring  125  is expanded and spring  85  is collapsed. 
     In the unlocked position, collar  77  pushes collet receiver  81  rearward such that its taper  110  disengages taper  107  on collet  91 . This motion allows collet  91  to expand and increase its bore diameter for receiving the shaft of tool implement  13 . Note that collet  91  is locked from axial movement and is only permitted to rotate with coupling  31  relative to tool  11 . However, in the unlocked position, collar  77  acts as a brake against accidental rotation of tool implement  13  since collar  77  abuts flange  83  on collet receiver  81 . This safety precaution during implement installation and/or removal is a significant improvement over prior art resecting tools. 
     Like guide sleeve  15 , tool implement  13  may be inserted to any depth between the minimum depth depicted in FIG. 2A (also its maximum axial extension from tool  11 ), to the maximum depth depicted in FIG. 1A (its minimum axial extension), depending upon the procedure being performed by the user. Thus, the axial extension of tool implement  13  may be varied by approximately one to two inches. At the minimum insertion depth, the rearward end of tool implement  13  is substantially radially aligned with the rearward end of the neck  109 , which provides the primary surface gripping area for securing tool implement  13  from slipping relative to collet  91 . At the maximum insertion depth, the rearward end of tool implement  13  abuts spacer  99 . The shaft of implement  13  is larger in diameter than the bore of spacer  99  and, thus, abuts spacer  99  in the minimum extension position. 
     After the user positions tool implement  13  at a desired axial extension, sleeve  61  is rotated in the reverse direction to the locked position. With this motion, balls  71  are moved out of rearward detents  74  and translated along slots  73  to the forward detents  74 , thereby moving collar  77  forward. This causes spring  125  to collapse and spring  85  to expand to move collet receiver  81  forward. The tapers  107 ,  110  of collet  91  and collet receiver  81 , respectively, interface to squeeze neck  109  around the shaft of tool implement  13  to lock it from axial and rotational movement relative to collet  91 . The relative positionings of tool implement  13  and guide sleeve  15  may be repositioned or removed entirely at any time by following the same steps described above. 
     Tool  11  is now ready for use. With motor  23  attached to base  21 , drive shaft  25  will rotate drive coupling  31 , collet receiver  81 , collet  91  and tool implement  13  to perform resecting procedures. Guide sleeve  15  is stationary and does not rotate. 
     The invention has several advantages. This resecting tool is compatible with many types of tool implements whether or not they have drive shoulders or other drive features. As described above, the tool is ideally suited for implements with a smooth cylindrical surface. Both the tool implement and the drive sleeve may be axially repositioned to any desired position between the minimum and maximum axial extensions. Moreover, the tool implement and drive sleeve are positioned independently so that optimal spacing relationships may be obtained. The braking feature also prevents accidental actuation of the resecting tool to minimize risk of injury to the user. The serpentine collet provides improved grip on the guide sleeve, is easily removed from the collet nut for cleaning, and allows the guide sleeve to have a significant range of axial extension from the tool. 
     While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention. For example, rather than having a rotating sleeve with balls to extend and retract the collet, a sleeve which is manually pushed or pulled to actuate the collet would be feasible.