Abstract:
An improved design for a powered abrading or cutting instrument for surgery is described. A basic instrument comprising a burr, a driveshaft, a support tube or shaft for the driveshaft, and a bearing between the driveshaft and the support is further provided with an external tube. The external tube provides one or more of drainage, irrigation, and provision of a sheath function. Some embodiments of the improved design can remove debris without requiring suction or other mechanical assistance, and have improved resistance to clogging.

Description:
RELATED APPLICATIONS  
       [0001]    This non-provisional application claims the benefit under Title 35, U.S.C. § 119( e ) of co-pending U.S. provisional application serial Nos. 60/322,815, 60/322,855, 60/322,856, and 60/322,857, filed Sep. 17, 2001. U.S. provisional application Nos. 60/322,815, 60/322,855, 60/322,856, and 60/322,857 are each incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates to improved designs for rotary abraders for use in surgery.  
         BACKGROUND  
         [0003]    The use of powered rotary cutters and abraders is useful in surgery and other medical procedures, particularly when treatment of hard tissues, such as bone, is conducted. Rotary drills and polishers are familiar in dentistry, for example. A current challenge is to provide cutting instruments that can be used in minimally invasive surgery, such as arthroscopy, laparoscopy, and other endoscopic types of procedures. These are collectively called “endoscopy” or “endoscopic” herein, including any minimally invasive procedure conducted through a small puncture, or a narrow natural opening. Typically, a puncture made for insertion of endoscopic instruments is made with an obdurator, a trocar or a cannula. Generally, rotary abraders in current endoscopic use have a diameter in the range of about an inch, or less. Such instruments can also be used in open surgery if desired.  
           [0004]    The key problems in endoscopy are providing instruments that are small enough to pass through a trocar; to provide for debris removal from the site; and to provide good tactile handling properties, to facilitate accurate tissue removal by the surgeon. Some of these problems have been addressed by existing instruments. The design of U.S. Pat. No. 4,842,578, for instance, provides an instrument that can be passed through a trocar, and the instrument provides for debris removal by vacuum assistance, via the interior of its drive shaft. Suction is typically required in this design because the relatively low-speed cutter provided in the prior art produces large particles that can clog a debris-removing means. Other designs include U.S. Pat. Nos. 3,937,222, 3,384,085, and 3,990,453. Some of these older designs do not provide for debris removal systems.  
           [0005]    In our co-pending application U.S. Ser. No. 09/480,500, hereby incorporated by reference, we disclose a rotary abrader/cutter (hereafter, collectively referred to by the term “burr”, used for “abrasion”, which also includes cutting, grinding, shaving, polishing, coring, and similar surgical maneuvers) that is, in preferred embodiments, driven by a liquid jet powered rotor. The burr tends to run at high speed in these instruments, providing rapid tissue removal combined with much smaller debris fragments compared to other endoscopic instruments. While some known designs for supporting the abrader or burr can potentially be used in combination with the liquid jet powered rotor driven instruments, there remains a need for improved designs to more fully take advantage of the improved properties provided by the liquid jet powered rotor drive. An improved design in several embodiments is described in this application.  
         SUMMARY OF THE INVENTION  
         [0006]    Rotary abrading and cutting devices (“devices”, herein) are provided with alternative methods for management of fluids and debris, and for providing lateral support to the rotating shaft and burr. Preferred devices have in common features that provide at least one method of removal of debris that is less likely to plug than most prior art devices. In particularly preferred embodiments, debris can be removed without requiring an external vacuum. Preferred devices provided according to the invention incorporate at least a cutting, polishing or abrading head (a “burr”); a shaft carrying the burr, which shaft may be hollow or solid or a combination; an element, most commonly tubular but in some embodiments optionally solid, supporting the shaft via a distal bearing; means for sheathing the burr so that it does not abrade tissue that is adjacent to the tissue to be abraded; and means for removal of fluid and debris from the site (“evacuation”, but not necessarily requiring a vacuum to be operative).  
           [0007]    In one embodiment, the driveshaft (“shaft”) of a cutting or abrading head is supported by a distal bearing and a tube. A “distal” bearing herein is a bearing supporting the shaft at a location on the shaft that is proximal to the burr and nearer to the burr than to the proximal end of the shaft. In preferred embodiments, the distal bearing(s) is both near the burr and proximal to it. An evacuation pathway and a sheath function are supplied, preferably, by a separate tube external to the support tube (which separate tube external to the support tube is hereinafter referred to as an “external tube”), providing a large space to use for evacuation. The external tube is typically maintained in concentricity to the support tube by standoffs or similar features.  
           [0008]    In a second embodiment, the support tube is flared in the vicinity of the burr, distal of the support bearing, to provide a sheath function. An external tube, similar to that of the first embodiment, is, preferably, provided for evacuation. Optionally, holes are provided in the proximal region of the sheath to efficiently convey debris to the external tube.  
           [0009]    In a third embodiment, the support tube is replaced by a support shaft internal of the shaft carrying the abrading head. A distal bearing is provided on the distal portion of the support shaft between the support shaft and the drive shaft. An external tube, in preferred arrangements, provides a sheath function, and optionally a pathway for debris removal. Alternatively, a pathway can be provided internally of the support shaft for debris removal.  
           [0010]    In each of these embodiments, the outer tube can be provided with ribs or “feet” to provide spacing from the next inward element, which may be the support tube or the shaft carrying the burr.  
           [0011]    Other advantages, novel features, and uses of the invention will become more apparent from the following detailed description of non-limiting embodiments of the invention when considered in conjunction with the accompanying drawings, which are schematic and which are not intended to be drawn to scale. In the figures, each identical, or substantially similar component that is illustrated in various figures is typically represented by a single numeral or notation. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention. In cases where the present specification and a document incorporated by reference include conflicting disclosure, the present specification shall control.  
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0012]    [0012]FIG. 1 is a cross-sectional illustration showing a distal portion of a surgical instrument with a prior art shaft support design;  
         [0013]    [0013]FIG. 2 is a cross-sectional illustration showing a distal portion of a surgical instrument with another prior art shaft support design;  
         [0014]    [0014]FIG. 3 is a cross-sectional illustration showing a first embodiment of the distal portion of a surgical instrument according to the invention;  
         [0015]    [0015]FIG. 4 is a cross-sectional illustration showing a second embodiment of the distal portion of a surgical instrument according to the invention;  
         [0016]    [0016]FIG. 4 a  is a cross-sectional illustration of the distal portion of the outermost external tube of FIG. 4, taken along lines a-a;  
         [0017]    [0017]FIG. 5 is a cross-sectional illustration showing an embodiment of the distal portion of a surgical instrument according to the invention similar to that of FIG. 4, except including evacuation openings in the sheath region of the support tube; and  
         [0018]    [0018]FIG. 6 is a cross-sectional illustration showing a third embodiment of the distal portion of a surgical instrument according to the invention;  
         [0019]    [0019]FIG. 7 is a cross-sectional illustration showing an alternative embodiment of the distal portion of a surgical instrument according to the invention similar to that of FIG. 6. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    A known abrader, for example that of Hall (U.S. Pat. No. 3,384,085), is illustrated schematically in FIG. 1. The figure illustrates the distal (operative) portion of an abrading instrument for use with a drive. The abrading head or “burr”  10 , which may have any of a large variety of shapes and profiles known in the art or similar thereto, is mounted on a shaft  40 , which may be solid, hollow, or a combination, that is in turn driven by a source of rotary motion, for example a liquid jet powered rotor, a turbine, or an electric motor, at the proximal end of the instrument (not illustrated; see the cited references for views of an entire apparatus.)  
         [0021]    The shaft  40  is enclosed by a tubular support  30 , which supports the shaft against lateral deflection by at least one bearing  50  in the distal portion of the device. Simple journal-type bearings made of low-friction materials are generally adequate; other bearing types are useable, including roller bearings and the like, as would be apparent to those skilled in the art. It is preferable to provide sufficient sealing to prevent debris-containing fluid from being drawn from the region of the abrader  10  into the bearing  50 , to minimize friction.  
         [0022]    In the illustrated embodiment, the tubular support  30  also acts as a sheath. The sheath region extends beyond the bearing  50  and the abrading head  10 , and shields the abrader  10  from tissue contact except where the sheath portion of the support tube  30  is cut away to provide a controlled zone of abrasion, cutting, etc.  
         [0023]    Evacuation is not directly supplied in this simple design. In FIG. 2, a separate evacuation lumen  69  is illustrated. Such a drain could be provided in association with the device, or it could be separately inserted into the operating space.  
         [0024]    [0024]FIG. 3 shows a first embodiment of the invention. In this embodiment, the burr  10 , shaft  40  and bearing  50  are similar in configuration to the instrument illustrated in FIG. 1. In the present embodiment, however, the support  30  is altered to terminate proximally of the burr  10 . The tubular support  30  is surrounded by an external tube  20  that acts as a sheath. The external tube  20  extends beyond the outer support, and shields the burr  10  from tissue contact except where the external tube  20  is cut away to provide a controlled zone of abrasion, cutting, etc. The external tube  20  is maintained in a selected position relative to the burr  10  by stand-offs  21 . These may be of any appropriate design, but preferably are longitudinal ribs, or are discrete “feet”, so that most of the annular area  60  bounded by the external tube  20  and the tubular support  30  is open. This allows the space between the sheath and the support to be used either as an outlet for debris, or as an inlet for lavage of the site of operation, or both. If multiple ribs are provided, both operations could be performed simultaneously in space  60 . The feet, ribs or other standoff elements may be provided in any convenient way. For example, and without limitation, they may be molded into a tube, or pressed into or other wise formed in a preformed tube, or supplied by separately formed pieces inserted into a tube, and preferably held in place by adhesion, welding, press fitting, or other conventional methods for retaining a piece in place in a tube. However, the external tube  20  provides substantially no lateral support for the shaft or the burr. Support tube  30  and bearing  50  are the primary supports preventing lateral deflection of the burr  10  and shaft  40 , and any support to support tube  30  provided by external tube  20  via standoffs  21  is incidental, i.e., the degree of deflection of the burr or shaft under side loading is not significantly affected by the presence or absence of external tube  20 .  
         [0025]    Because the debris is typically small in diameter relative to that in the prior art, (because of higher speeds available from the liquid jet powered rotor drive means of preferred instruments), and because the outlet space  60  is relatively large, suction is not typically required for debris removal with this design. In particular, a vacuum source or a suction or aspiration source is not typically needed. A slight positive pressure, for example provided by elevation of a bag of saline solution used for irrigating the site, can be sufficient to provide flow through the outlet space  60 . Significant debris-removal impulse can also be provided by the particular design of the burr  10 , as known to those skilled in the art, even in the absence of a hydrostatic head in the operation site.  
         [0026]    An additional improvement provided by this design is the ability, in some embodiments, to vary the position of the external tube  20  with respect to the burr  10 , by sliding or rotating the sheath with respect to the support tube. A simple bellows or similar means at the proximal end of the sheath (not illustrated) would supply the needed range of motion. Movement of the external tube  20  can be manual, as the proximal region of the sheath, near the driving device, is normally outside of the entry point into the patient; or controls operable from a handle of the device, or other location, can be provided.  
         [0027]    An additional advantage of the design is that the external tube  20  can be made of plastic, allowing direct visual or fluoroscopic observation of the position of the abrader. The tip of the external tube  20  can be made to be radio-opaque or visible (e.g., by dye) if desired.  
         [0028]    [0028]FIG. 4 shows a second embodiment of the invention, as an alternative version of the first embodiment. The burr  10 , which may have any of a large variety of shapes and profiles, is mounted on a shaft  40 , which may be solid, hollow, or a combination, that is in turn driven by a source of rotary motion, for example a turbine, a liquid jet powered rotor, or an electric motor, at the proximal end of the instrument (not illustrated).  
         [0029]    As in FIG. 3, the shaft  40  is enclosed by a tubular support  30 , which supports the shaft against lateral deflection via at least one bearing  50  in the distal portion of the device. It is preferable to provide sufficient sealing to prevent debris-containing fluid from being drawn from the region of the burr  10  into the bearing  50 , to minimize friction.  
         [0030]    The tubular support  30  is expanded at the distal end into a sheath region  15 . The sheath extends beyond the tubular support  30  laterally and distally, and shields the burr  10  from tissue contact except where it is cut away to provide a controlled zone of abrasion, cutting, etc.  
         [0031]    A debris removal channel is formed by an external tube  20 . The external tube  20  is maintained in a selected position relative to the tubular support  30  by longitudinal fins or discrete “feet”  21 , illustrated in FIG. 4 a , which is a perspective view of a cross section of external tube  20 . Returning to FIG. 4, the fins or feet  21  ensure that most of the annular area  60  bounded by the external tube  20  and the tubular support  30  is open. This allows the space between the external tube  20  and the support tube  30  to be used either as an outlet for debris, or an inlet for lavage of the site of operation, or both. If multiple ribs  21  are provided, both operations could be performed simultaneously. The external tube  20  may be moveable, as described in the first embodiment.  
         [0032]    Again, because the debris is typically small in diameter, and the outlet space  60  is relatively large, suction is not typically required for debris removal with this design. In particular, a vacuum source or a suction or aspiration source is not typically needed. A slight positive pressure, for example provided by elevation of a bag of saline solution used for irrigating the site, can be sufficient to provide flow through the outlet space  60 . As previously mentioned, some debris-removal impulse can also be provided by the design of the burr  10  even in the absence of a hydrostatic head in the operation site.  
         [0033]    [0033]FIG. 5 shows a variant of the apparatus of FIG. 4 in which openings  16  are created in the sheath region  15  of the support tube  30  to provide more direct removal of the debris from the region around the burr  10  to the debris removal space  60 . Debris may also pass outside the sheath, as in FIG. 4.  
         [0034]    As in FIGS.  3  or  4 , an additional improvement provided by this design is the ability, in some embodiments, to vary the position of the external tube  20  with respect to the burr  10  by sliding or rotating the outer tube with respect to the support tube. This variation can allow control of the location from which debris-containing fluid is removed, thereby helping to control the visual clarity of the operating field.  
         [0035]    An additional advantage of the design is that the external tube  20  can be made of plastic, for example by extrusion, thereby allowing direct visual or fluoroscopic observation of the position of the abrader. The tip of the external tube  20  can be made to be radio-opaque or visible (e.g., by dye) if desired.  
         [0036]    A third embodiment of the invention is illustrated schematically in FIG. 6. The figure illustrates the distal (operative) portion of an improved abrading instrument. The burr  10 , which may have any of a large variety of shapes and profiles, is mounted on a shaft  40 , which in this embodiment is hollow, that is in turn driven by a source of rotary motion, for example a turbine, liquid jet powered rotor, or an electric motor, (not shown) at the proximal end of the instrument (to the left of the portion of the instrument illustrated in the drawing). Here a portion of the source of rotary motion is shown, namely, a step-down worm gear  80 , which is driven by a primary source (not illustrated), and which, in turn, drives a gear  70  attached to the shaft  40 . As illustrated, the distal portion  93  of the device can be detached from a handpiece body  90  carrying the primary source of rotational energy by a latch or other connector  95 , but the distal end  93 , in other embodiments, could also be permanently affixed to the handpiece body. The exact method of connection of the abrading element and the drive and handpiece is not critical, and any of the many known methods illustrated in the art for connecting abrading devices to handpieces is potentially of use in the invention.  
         [0037]    The shaft  40  is supported internally by a support  30 , which can be hollow or solid. The support  30  is affixed to a handpiece body  90  or other supporting element, so that it provides support to the shaft  40  via bearings  50 , typically at least one in the distal region of the support/shaft interface, or by other means of providing support while minimizing friction. Simple journal-type bearings made of low-friction materials are generally adequate; other bearing types are useable, including roller bearings and the like, as would be apparent to those skilled in the art. It is preferable to provide sufficient sealing to prevent debris-containing fluid from being drawn from the region of the burr  10  into the bearing  50 , to minimize friction.  
         [0038]    The shaft  40  is surrounded by an external tube  20 . As in previous embodiments, the external tube  20  is not a support to prevent deflection of burr  10  or shaft  40 ; that function is provided by support tube  30  and bearing  50 . The external tube  20  extends beyond the support  30  and the shaft  40  to provide a sheath, and shields the burr  10  from tissue contact except where the external tube  20  is cut away to provide a controlled zone of abrasion, cutting, etc. The external tube  20  is maintained in a selected position relative to the burr  10  by stand-offs  21 . These may be of any appropriate design, and are preferably constructed to tolerate at least intermittent contact with the rotating hollow shaft  40 . In the design as illustrated, the stand-offs  21  are preferably configured to minimize fluid flow past the standoffs and into the volume  60  between the external tube  20  and the shaft  40 . Removal of fluid and debris is accomplished through one or more openings  65  in the distal end of the hollow shaft  40 , such that the fluid flows through lumen  67  in the support tube  30  to an exit at  66 .  
         [0039]    Because the debris is typically small in diameter, and the outlet space  67  is relatively large, suction is not typically required for debris removal with either of the above-described embodiments of this design. In particular, a vacuum source or a suction or aspiration source is not typically needed. A slight positive pressure, for example provided by elevation of a bag of saline solution used for irrigating the site, can be sufficient to provide flow through the outlet space  67  or  60 . As previously mentioned, some debris-removal impulse can also be provided by the design of the burr  10  even in the absence of a hydrostatic head in the operation site.  
         [0040]    An additional improvement provided by this design is the ability, in some embodiments, to vary the position of the external tube  20  with respect to the burr  10 , by sliding or rotating the external tube  20  with respect to the shaft  40 . A simple bellows or tight concentric shells (e.g., as in a radio antenna; not illustrated) at the proximal end of the external tube  20  would supply the needed range of motion. Movement of the external tube  20  can be by hand, as the proximal region of the external tube  20  near the handpiece body  90  is normally outside of the entry point into the patient; or mechanical or other controls can be provided.  
         [0041]    An additional advantage of the design is that the external tube  20  can be made of plastic, allowing direct visual or fluoroscopic observation of the position of the abrader. The tip of the external tube  20  can be made to be radio-opaque or visible (e.g., by dye) if desired.  
         [0042]    [0042]FIG. 7 shows a cross section of an embodiment similar to that of FIG. 6. In FIG. 7, the standoffs  21  can be longitudinal ribs or discrete “feet” as previously described, so that most of the annular area  60  bounded by the external tube  20  and the shaft  40  is open. This allows the space between the external tube  20  and the shaft  40  to be used either as an outlet for debris, or an inlet for lavage of the site of operation, or both. Removal of the fluid may be through an opening  61  in the side of the external tube  20 . (And, in contrast to FIG. 6, there would not need to be an opening  65  in the shaft  40 , unless two separate fluid passage routes were desired, for example one for influx and one for efflux.) The opening  61  may be near the proximal end of external tube  20 , as illustrated, or elsewhere on the tube. Otherwise, the embodiment illustrated in FIG. 7 is substantially identical to the embodiment illustrated in FIG. 6. A similar arrangement for debris removal may also be provided in certain arrangements of other embodiments of the invention, for example in certain arrangements of the embodiments as illustrated in FIGS. 3, 4, and  5 .  
         [0043]    While several embodiments of the invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and structures for performing the functions and/or obtaining the results or advantages described herein, and each of such variations or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art would readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that actual parameters, dimensions, materials, and configurations will depend upon specific applications for which the teachings of the present invention are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described. The present invention is directed to each individual feature, system, material and/or method described herein. In addition, any combination of two or more such features, systems, materials and/or methods, provided that such features, systems, materials and/or methods are not mutually inconsistent, is included within the scope of the present invention. In the claims (as well as in the specification above), all transitional phrases or phrases of inclusion, such as “comprising,” “including,” “carrying,” “having,” “containing,” “composed of,” “made of,” “formed of” and the like shall be interpreted to be open-ended, i.e. to mean “including but not limited to.” Only the transitional phrases or phrases of inclusion “consisting of” and “consisting essentially of” are to be interpreted as closed or semi-closed phrases, respectively, as set forth in MPEP section 2111.03.