Abstract:
A rasping cannula uses a variety of cutting surfaces to augment fat and tissue extraction in cosmetic surgical procedures. In one aspect, a cannula may have a number of holes with curved cutting edges. In another aspect, the tip of a cannula may be curved. In this manner, lateral movement of the cannula excises tissue such as fat for faster, more effective removal.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. App. No. 61/536,174 filed on Sep. 19, 2011, the entire content of which is hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    Cannulas are surgical instruments, generally formed as tubes, used for delivery or removal of fluid and the like from a body. In cosmetic surgery, a cannula can be used to harvest fat or other tissue, and/or to insert bulk fillers. A cannula with holes for fat harvesting has been proposed, as described for example in U.S. Pat. No. 5,817,050, the entire content of which is hereby incorporated by reference. 
         [0003]    Harvesting cannulas of the prior art focus on vacuum forces. There remains a need for improved harvesting cannulas. 
       SUMMARY 
       [0004]    A rasping cannula uses a variety of cutting surfaces to augment fat and tissue extraction in cosmetic surgical procedures. In one aspect, a cannula may have a number of holes with curved cutting edges. In another aspect, the tip of a cannula may be curved. In this manner, lateral movement of the cannula excises tissue such as fat for faster, more effective removal. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0005]    The invention and the following detailed description of certain embodiments thereof may be understood by reference to the following figures: 
           [0006]      FIG. 1  shows a rasping cannula. 
           [0007]      FIG. 2  shows a rasping cannula. 
           [0008]      FIG. 3  shows a side view of a curved edge for a slit of a cannula. 
           [0009]      FIG. 4  shows a side view of a curved tip cutting edge for an insertion tip of a cannula. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    All documents mentioned herein are hereby incorporated in their entirety by reference. References to items in the singular should be understood to include items in the plural, and vice versa, unless explicitly stated otherwise or clear from the text. Grammatical conjunctions are intended to express any and all disjunctive and conjunctive combinations of conjoined clauses, sentences, words, and the like, unless otherwise stated or clear from the context. Thus the term “or” should generally be understood to mean “and/or” and so forth. 
         [0011]    Disclosed herein are cannulas for use in cosmetic surgical procedures such as liposuction or other fat harvesting. However it will be understood that the invention disclosed herein is not so limited, and the inventive concept may be adapted to other tissue harvesting and/or extraction procedures. 
         [0012]      FIG. 1  shows a rasping cannula. The cannula  100  may include a body  102 , a proximal end  104 , and a distal end  106  with an insertion tip  108 . 
         [0013]    The proximal end  104  may include any suitable structure for manipulating the cannula  100  or coupling the cannula  100  to a trocar or other instrument. The proximal end  104  may also be coupled by a tube or the like to a vacuum source  110  in fluid communication with an interior of the body  102  for applying vacuum through the body  102  to harvest fat or other tissue through the cannula  100 . 
         [0014]    The distal end  106  may include an insertion tip  108 , which may include an opening and a cutting edge to cut fat or other tissue as the body  102  is inserted into a surgical site. 
         [0015]    The cannula  100  may also include a protective sheath  112  configured to slide along the body  102  or otherwise positionable to cover various cutting edges of the cannula  100  in order to controllably expose cutting edges of one or more slits and/or the insertion tip  108 . In this manner, the rasping action of the cannula  100  may be selectively deployed at a time and in a location along the body  102  where cutting of fat or other tissue is desired by a user. 
         [0016]      FIG. 2  shows a body  202  of a cannula  200  having an axis  204 . By way of example, the body  202  may have an outside diameter of 5.0 mm, 3.5 mm or any other suitable dimensions, and a length of 35 cm or any other length suitable for harvesting fat from a particular site. The body  202  may include an open interior  208  for passage of fat, fluids, other tissue and the like through the body  202  to and from a surgical site. Consistent with conventional surgical implements, the cannula  200  may have a substantially cylindrical body  202 , although other cross-sectional shapes may also or instead be used for the body  202 , and the cannula  200  may more generally include any elongated body or the like. 
         [0017]    A plurality of slits  206  may be provided so that tissue such as fat can be vacuum-extracted along the length of the body  202 . Each slit  206  may provide a passage from an exterior of the body  202  to the open interior  208 , along with a cutting edge that extends on a perimeter thereof that is elevated outside the body  202  (e.g., away from the open interior  208  and toward the exterior) in order to present a cutting surface that can be used to cut tissue with a corresponding movement of the body  202 . In general, a variety of arrangements, shapes, and sizes of slits may be provided, consistent with use in a forward cutting motion of the cannula  200  (i.e., toward the insertion tip), a backward cutting motion (i.e., toward the proximal end), and/or a rotational cutting motion (i.e. rotationally about the axis  204 ). The cutting edges of the slits  206  may thus be generally oriented to cut tissue in a single direction of motion of the body  202 , or in multiple directions. 
         [0018]    In one aspect, the cutting edge of each one of the plurality of slits  206  may be oriented to cut tissue in one direction of movement along the axis  204  of the body  202 , such as a movement along the axis  204  from the proximal end toward the insertion tip (forward motion) or a movement from the insertion tip toward the proximal end (backward motion) or a bidirectionally upon movement in either direction along the axis (e.g. back and forth, or away from and toward the insertion tip). In another aspect, the cutting edge of each one of the plurality of slits  206  may be oriented to cut tissue upon rotation of the body  202  about the axis  204 , which may similarly be (rotationally) one directional or two directional. 
         [0019]    A variety of sizes may be used. For example, each slit  206  may be about 1.5 mm along a short (or ‘minor’) axis and about 2.5 mm along a long (or ‘major’) axis, or any similar dimensions for which the major axis is substantially greater than the minor axis. Any number of slits may be provided. 
         [0020]    A variety of arrangements may also be used. In one aspect, the slits  206  may wrap substantially completely around a circumference of the body  202 . In another aspect, the slits  206  may wrap around about two hundred forty degrees of the body  202 , or some other amount that provides a non-harvesting surface so that the cannula  200  can be used as a one-side or directional harvesting device. Similarly, the slits  206  may be oriented with a major axis oriented or angled about forty five degrees off the axis  204  of the body. Some slits may have a major axis oriented or angled about ninety degrees off the major axis of some other ones of the slits, as generally illustrated in  FIG. 2 , which provides multiple cutting angles and edges as the body  202  moves axially within a surgical site. This arrangement advantageously provides two opposing cutting forces as slits  206  pass over tissue and cut alternately from a left side and a right side. 
         [0021]    The shapes of the slits  206  may also vary. For example, while generally oval slits are illustrated, the slits  206  may be circles, polygons, or other shapes, the emphasis being on the direction and arrangement of cutting surfaces presented to tissue as the body moves  202  within tissue rather than the shape of the passage formed into the interior  208  of the body  202 . Thus it will be more generally understood that while a specific arrangement of slits is illustrated, different numbers, shapes, and orientations of slits, holes, or the like with cutting edges may also or instead be used with satisfactory results. 
         [0022]      FIG. 3  shows a side view of a curved edge for a slit of a cannula. In general a slit  300  provides an opening  302  between an exterior  304  and an interior  306  of a body  308  of the cannula. 
         [0023]    A cutting edge  310  for the slit  300  may be a curved cutting edge forming a sharp, protruding ridge above the surface of the body  308  (the surface of the body illustrated where it spans the slit  300  by a dashed line  312 ) so that the cutting edge stands up somewhat off the otherwise cylindrical exterior surface of the body  308 . This configuration is conveniently machinable to a sharp edge in stainless steel or other biocompatible surgical materials; however it will be understood that any other shape of cutting edge that extends above the surface of the body  308  may also or instead be used. Similarly, the cutting edge  310  may lie in the plane of the surface, which generally provides a less aggressive cutting action that may be advantages in certain applications. 
         [0024]    In general, tissue excised from a surgical site by the cutting edge  310  may be further urged toward the interior  306  of the body  308  by the beveled interior surfaces of the slit  300  which, in conjunction with reverse pressure from a vacuum source, can effectively withdraw harvested fat from the site and out of the cannula. 
         [0025]      FIG. 4  shows a side view of a curved tip cutting edge for an insertion tip of a cannula. The body  402  of the cannula may have a generally cylindrical exterior with a circular cross section or have some other general cross section along its length. As shown in  FIG. 4 , the cutting edge  404  of an insertion tip  406  may be on the end of the insertion tip  406  (referred to herein as a “tip cutting edge”) and may form a curved cutting edge that extends beyond the surface of the body  404 —that is, radially outside a cross section for the body  404 , as illustrated by a dashed line  408 —to engage surrounding tissue as generally discussed above. 
         [0026]    The insertion tip  406  may include an opening  410  coupled to an open interior of the body  402  through which fat or other tissue can be withdrawn. The cutting edge  404  may be on a perimeter of the opening  410 , and may extend entirely around the perimeter or a portion thereof. 
         [0027]    As with the cutting edges of the slits discussed above, different positions and angles for the cutting edge  404  may be employed according to a desired aggressiveness for the cutting action. For example, the cutting edge may actually be recessed such that the leading edge of the cutting edge is aligned with the interior surface of the body  102 . Or the leading edge may be machined or otherwise formed into a location between the interior and exterior surface of the body  102 . More generally, any configuration providing an edge suitable for cutting tissue may be used for the cutting edge as contemplated herein. 
         [0028]    While particular embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes and modifications in form and details may be made therein without departing from the spirit and scope of this disclosure and are intended to form a part of the invention as defined by the following claims, which are to be interpreted in the broadest sense allowable by law.