WO1992015255A1

WO1992015255A1 - Method and apparatus for material removal

Info

Publication number: WO1992015255A1
Application number: PCT/US1992/001614
Authority: WO
Inventors: Arthur H. Hamlin; John A. Snapp
Original assignee: Bowen & Co., Inc.
Priority date: 1991-03-06
Filing date: 1992-03-05
Publication date: 1992-09-17
Also published as: CA2105320A1

Abstract

Various methods and apparatus are disclosed which relate to material cutting of the type which typically ranges from abrading hard materials to slicing soft materials. Cutting in the foregoing manner is accomplished by an angled cutting edge (46) which is operable not only to cut material, but to direct the cut material into an aperture (40), from which the material can be removed upon the application of negative pressure. The disclosed method and apparatus have particular unity in surgical cutting applications.

Description

METHOD AND APPARATUS FOR MATERIAL REMOVAL

BACKGROUND OF THE INVENTION: 1- Field of the Invention

The invention relates generally to method and apparatus for effecting the removal of material such as organic materials from a work surface. More particularly, the invention relates to method and apparatus for removing such material with a rotatably driven cutting apparatus and the removal of the cut material by way of negative pressure applied in the vicinity of the work site in which the cutting apparatus is operable.

2. Description of the Related Art

Cutting apparatus and methods which effect material removal from a work surface and evacuation of the cut material from the vicinity of cutter operation have particular applicability in such diverse fields as carpentry, metal working, and a variety of surgical procedures. In the latter instance, such apparatus and methods have particular applicability in the field of endoscopic, and particularly arthroscopic, surgical procedures. Such surgical procedures are generally referred to as "closed" procedures, as the surgical site is accessed by forming only one or several comparatively small incisions in the body of the patient through which various specialized instruments can be inserted. These "closed" procedures are to be contrasted with conventional, "open" procedures, in which one or more comparatively large incisions are formed in the patient's body to provide maximum exposure of the surgical site to the environment. Endoscopic instruments and methods (hereinafter referred to collectively as "instrumentation") have enjoyed considerable success since the advent of this surgical

SUBSTITUTE SHEET technology, as surgeons, patients and insurance providers alike have become increasingly receptive to the benefits such as their comparatively lesser degree of invasiveness and remarkably shortened recuperation periods that are afforded by these procedures. Furthermore, operations which heretofore have required open surgical procedures, during which a general anaesthetic was generally used to sedate the patient, can now be performed in a closed, endoscopic-type procedure, in which a local anaesthetic agent can oftentimes be employed. As a result of the foregoing advantages, not only can patient recuperation be expedited, but the risks attendant with general as opposed to local anesthetics can be altogether avoided in many instances. For all of the foregoing reasons, endoscopic instrumentation has exhibited nearly unprecedented growth since its inception.

A principal limitation in all endoscopic surgical procedures involves not only access to the surgical site to be treated, but also the removal of material that is successfully cut or otherwise removed from the surgical site. As used throughout this disclosure, the terms "cut", "cutting" and variations thereof are to be regarded as encompassing any method of material removal, including slicing, abrading and shaving, unless the context clearly suggests otherwise. While instrumentation for facilitating access to remote surgical sites such as various joints in the human body is the subject of our copending application, U.S. Serial No. 611,278 filed on November 9, 1990, the current state of the art of surgical instrumentation does not adequately address the difficulties experienced by surgeons in removing fine shavings and other debris that can arise from the various cutting processes that are used to reduce the dimensions of, in particular, hard materials such as bone and calcified cartilaginous

SUBSTITUTE SHEET materials. A problem exists in the removal of such fine, particulate remnants of such materials as they are susceptible to avoiding surgeon detection and/or withdrawal by the suction apparatus typically associated with such cutters. Instead, this material tends to be radially displaced outwardly and away from the rotatable cutting apparatus, thereby avoiding to an appreciable extent the beneficial effects of the suction apparatus and/or irrigating fluids such as saline solution circulated through the surgical site. These difficulties can become even more pronounced when gaseous rather than liquid irrigation media are utilized, as gaseous media, while improving visualization of the surgical site, is generally not as effective as liquid media in flushing debris from the surgical site. The foregoing difficulties that have been experienced in removing such fine, particulate material from remote portions such as skeletal joints of the body of a patient have resulted in a hinderance to expedient and complete patient recoveries.

Accordingly, it is an object of the subject invention to provide method and apparatus for removing material from a work surface and effectively collecting the removed material for withdrawal from the work site. Another object of the subject invention is to provide various cutter head configurations that can be adapted to existing cutter apparatus to improve the efficiency with which material can be separated and withdrawn from a work surface such as an internal body structure of a patient.

A further object of the subject invention is to provide cutter methods which tend to collect rather than radially discharge debris from material that is cut.

Yet a further object of the subject invention is to provide surgical instrumentation which expedites

SUBSTITUTE SHEET surgical procedures and enhances the time and extent of patient recovery.

BRIEF DESCRIPTION OF THE DRAWINGS: These and other objects and advantages will become apparent from a reading of the following description in conjunction with the accompanying drawings, in which:

Fig. 1 is a schematic sectional side view of surgical instrumentation with which the cutting apparatus and methods of the subject invention are applicable;

Fig. 2 is an exploded view of one aspect of a cutter head constructed in accordance with the principles of the subject invention; Fig. 3 is a frontal view of the cutter member head depicted in Fig. 2;

Figs. 4-6 are simplified schematic sectional side views of the cutter member head illustrating various cutting edge arrangements; Fig. 7 is a perspective view of the sheath portion of the apparatus depicted in Fig. 2;

Fig. 8 is a sectional side view of the apparatus illustrated in Fig. 2 in combination with the distal end of a surgical instrument of the type depicted in Fig. 1; Fig. 9 is an exploded view of an alternative aspect of a cutter head constructed in accordance with the principles of the subject invention;

Fig. 10 is a frontal view of the cutter member head depicted in Fig. 9; Fig. 11 is a side view of the cutter head depicted in Fig. 9; and

Fig. 12 is a view along the line 12-12 of Fig. 10.

SUMMARY OF THE INVENTION: The invention relates generally to method and apparatus for effecting the removal of material of

_SUB_STITUTE SHEET various levels of density and hardness. The disclosed method and apparatus have particular utility in closed surgical applications, where difficulties are oftentimes encountered in removing material that is cut by cutting apparatus. Various angled blade configurations are provided to effect differing characters of cutting such as abrading and slicing. While the preferred embodiments are particularly useful for rotatably driven cutters, the principles of the disclosed invention are equally applicable for reciprocably-driven cutting equipment as well as for disposable and reusable cutting equipment.

In the apparatus of the invention, a cutter head for use with a driveable material removal instrument such as surgical shaver is provided, in which the cutter head is provided with cutting means including a cutter member having at least one cutting element formed along an exterior surface thereof. An aperture extends from the cutting element and to receive material that is cut or otherwise removed by the cutting element. The cutting element is configured so as to direct the removed material into the aperture as it is removed by the cutting element. A passage in fluid communication with the aperture provides for the removal from the aperture of cut material for transport therefrom upon the application of negative pressure to the passage. Preferably, the cutting means is coupled to a source of rotational drive input thereto; however, other forms of drive input, such as reciprocable drive input, can be provided in lieu thereof. The cutter member can be provided with a plurality of cutting elements that are symmetrically or asymmetrically spaced about the cutter member. The cutting elements can be in the form of slots which are defined by first and second edges, at least one of which is provided with a sharpened surface.

sυ _IBST1TUTE SHEET The sharpened surface of the cutting element can be formed along the lateral exterior surface of the cutter member or along a tab extending from a cutter member distal end. The sharpened surface of the respective edge mounting arrangements is provided with an angular orientation which preferably falls within the range of from about 5^* to about 70^* with respect to a tangent line extending from an outer surface of the edge.

The method of the invention provides for the removal of material from a work surface, in which a cutting member having at least one cutting edge is advanced against the work surface so as to engage and remove material therefrom. The material thus removed is directed by the cutting edge into an aperture formed in the cutting member and extending from the cutting edge. Negative pressure is applied to draw the removed material through the aperture and into a passage extending through the cutting member and positioned in fluid communication with the aperture, thereby providing an evacuation path for the withdrawal of material removed from the work surface. The foregoing method is particularly useful for removing material such as bone, calcifications such as bunions, and other materials from the bodies of various organisms. In a preferred aspect of the method, the cutter member is a rotatably driven cutting member; however, the use of non-rotatably driven cutting members is embraced by the foregoing method. The cutting member can be straight or angularly oriented with respect to a supply of driving input thereto. The cutting edge can be formed by a variety of metal working processes, such as electron discharge machining (EDM) and rotary cutting.

SUBSTITUTE SHEET DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:

With reference to the drawings, wherein like reference characters represent corresponding parts throughout the various views, and with particular reference to Figs. 1 and 2, a rotatably drivable cutter head 10 in accordance with the subject invention is disclosed for use in conjunction with cutting apparatus such as surgical shavers, depicted generally by reference character 12. Such surgical apparatus are particularly advantageous for performing various closed surgical procedures in remote locations such as skeletal joints such as the indicated knee cap 14. While the instrument 12 illustrated in Fig. 1 is of the general variety having a curved distal end configuration for traversing curvalinear paths such as that indicated by reference character 16, it is to be appreciated and understood that the subject invention described hereinbelow is applicable for use with both curved as well as straight distal end cutting equipment. Such equipment is generally provided with an elongated shaft

18 through which rotational driving input supplied from a motor 20 can be transmitted to the cutter head 10.

Negative pressure is typically applied through one or more apertures formed in the shaft 18 for facilitating removal of material that is cut by operation of the rotatably-driven cutter head 10.

With reference to Fig. 2, the cutter head 10 of the subject invention is generally comprised of two components: a cutter member 24 and a sheath 26 which at least partially surrounds the cutter member. The cutter member 24 and sheath 26 are each provided with generally cylindrical cross-sectional configurations, albeit of different diameters. The cutter member, in turn, is comprised of a head portion 28 which extends from a shank 30. Preferably, the head and shank portions of the cutter member 24 are formed as an integral member.

_SUBSTITUTE SHEET A shoulder 32 is preferably provided to inhibit rearward displacement of the cutter head 24 in the manner described below. The position of the shoulder 32 can be at the junction between the head 28 and shank 30, as shown, or can be along any other portion of the cutter member 28. A proximal end of the shank 30 is provided with means such as gear teeth 33 for receiving rotational driving input that is transmitted thereto by appropriate power transmitting means such as the shaft 18 (Fig. 1) and/or drive components contained therein. The preferred power transmitting arrangement is that which is the subject matter of our copending patent application, Serial No. 611,278 that was filed on November 9, 1990. However, other suitable arrangements for transmitting rotational driving input to a cutter head, such as that which can be provided by belts, transmissions, biasing means or other means, is encompassed by the subject invention, in which case an appropriately-configured engagement arrangement would be substituted for the arrangement of gear teeth 33 provided at the proximal end of the shank 30.

The cutter member head 28 is provided with a generally smooth, uniform exterior surface which tapers inwardly toward a generally flat distal end 36 of reduced diameter, as shown in Figs. 2 and 3. A plurality of slots 38 extend generally radially inwardly from the surface 39 of the cutter member head 28 so as to define apertures 40 which extend from the cutter member head surface 39 to a tubular lumen 42 which extends the length of the cutter member 24. The slots 38, which can be formed by rotary cutting, electron discharge machining, or any other suitable process, are defined by a compound edge surface 44 that is comprised of a first edge 46 that is arranged generally parallel to the longitudinal axis L of the cutter head 24 and a second edge 48 which extends in a generally curvalinear

SUBSTITUTE SHEET fashion from the respective distal and proximal ends of the first edge 46. As used throughout this description, the term "proximal" refers to a direction or direction of travel from the free end of the cutter member head toward a source of drive input thereto, and "distal" refers.to a direction or direction of travel toward the free end of the cutter member head.

With continuing reference to Figs. 2 and 3, the cooperation of the respective first and second slot edges 46, 48 provides the cutter head 24 with a generally semi-helically fluted configuration. It is to be appreciated, however, that the overall configuration of the cutter head will vary in accordance with both the number and configuration of slots 38 provided therein. In the illustrated embodiment, the first edge 46 is provided with a sharpened edge surface for removing material against which it is rotatably driven. While the second edge 48 can optionally be provided with a sharpened surface as well, it is to be appreciated that rotation in the clockwise direction indicated by the arrow is likely not to provide for an appreciable degree of positive (i.e., cutting) engagement of that edge with material to be cut by the cutter head. Preferably, at least the first cutting edge 46 is formed from surgical grade stainless steel. The walls 50 and 52, which extend radially inwardly from the respective slot edges 46 and 48, are preferably arranged such that at least one of the walls is tapered inwardly along their respective extensions toward the cutter head lumen 42 so as to provide a work surface which, together with the sharpened angled cutting edge provided along slot edge 46, facilitates removal of material such as mammalian bone and tissue as the material is rotatably cut by the cutting edge 46. Figs. 4-6 illustrate in an exemplary fashion various of the cutting angle configurations that are obtainable in accordance with practice of the subject invention. The cutting angle, designated by the characters "α" in the various illustrations, is defined herein as the angle which extends between the cutting edge 46 and a tangent drawn to the cutting edge. It will be appreciated that, as a approaches zero, the edge 46 exhibits a more slender, razor-edged profile which is optimal for cutting relatively soft materials such as body tissues. As the angle α increases toward 90^*, the edge 46 exhibits a more square, block-like profile which is best suited for abrading relatively hard materials such as bone. In the preferred embodiment of the invention, the included angle a for the slotted cutting member of the subject invention can range between 0^* and 90^*, but is preferably in the range of from about 5° to about 70^* in accordance with the nature of the material to be cut and user preference. With reference to Fig. 4, the first (cutting) edge 46 is provided with a very narrow included angle α so as to effect a material slicing rather than abrading-type of material cutting. Slots of this type can be formed by, for example, use of a saw blade-type cutter or wire EDM that is applied along an acute angle with respect to a tangent of the cutter head so as to provide a cutting edge 46 that defines an included angle α that is comparatively small to that of the cutting edges depicted in the arrangements of Figs. 5 and 6. Such cutting edges are well suited for the slicing of relatively soft materials such as body tissue and cartilage. With reference to Fig. 5, the angle α is on the order of approximately 90^*, which can be advantageous for abrading relatively dense, hard material such as bone. Such cutting edges provide for a generally smooth, continuous level of abrasion that can be relatively easily controlled by the user. The arrangement depicted in Fig. 6 provides for a more aggressive extent of abrasion from that depicted

SUBSTITUTE SHEET in Fig. 5, as the edge 46 is formed with an angle α of about 45^*. This arrangement provides an intermediate level of abrading which is suitable for use with hard surfaces such as wood, bone and calcified areas of the body such as bone spurs in the foot. As the body material is cut and directed into the slot apertures 40 in the foregoing manner, the cut material is also drawn by negative pressure applied to the cutter head lumen 42 so as to draw the cut material from the aperture 40 into the lumen 42 for removal therethrough by appropriate negative pressure-generating means as indicated by reference number 22 (Fig. 1) from the body of the patient.

Operability of the cutter member in the foregoing manner affords a considerable advance in the art of material cutting, and particularly abrading-type processes, as hard material such as bone can be removed and the debris resulting therefrom can be collected in the slots as the debris is produced. Material abrading and debris collection proceeds in the cutter heads of the subject invention without the necessity of a reactionary force produced by surfaces such as tubular structures surrounding the cutter apparatus against which the debris is typically forced in prior art apparatus. As a result of the configuration and operational advantages of the foregoing cutter instrumentation, material can be removed to provide for much greater tolerances between elements such as skeletal bones that are displaceable relative to one another than has heretofore been capable.

Figs. 7 and 8 illustrate details of the configuration of the sheath 26 which at least partially surrounds the cutter member 24 described above. As is indicated in the drawings, the sheath 26 is provided with a generally cylindrical cross-sectional configuration along its proximal segment 54 and an open-

SUBSTITUTE SHEET sided, semi-cylindrical configuration along its distal segment 56. A proximal portion of the sheath distal segment extending outwardly from the longitudinal midline L so as to define a window 58 for receiving the cutter head 28. The wall 60 defining the window 58 is provided with a generally concave configuration along its lower, lateral surface so as to increase the exposure of the cutter member which is rotatably driven therein. The distal end 62 of the sheath is configured complimentary to the distal end 36 of the cutter member so as to receive the cutter member therein and inhibit distal movement of the cutter member in a longitudinal direction.

The nature of cooperation between the cutter member head 28 and sheath 26 is best illustrated in Fig. 8, which illustrates further in schematic form the arrangement for providing rotational driving input to the cutter member 24. As is shown in the drawing, the proximal end of the sheath 26 is coupled in a conventional manner to a curved interconnector 64 which serves generally to couple the cutter head 10 to the instrument shaft 18. Further details of the curved interconnector and the manner in which cutter head rotational driving input is transmitted therethrough are described in our copending U.S. patent application Serial No. 611,278, the disclosure of which is incorporated herein by reference. As is shown in the drawing, the proximal end of the cutter shank 30 which is provided with means such as gear teeth 33 for receiving rotational driving input thereto extends into the distal end of the interconnector 64 so as to engage complimentary-configured means such as gear teeth 66 formed along a distal end of the drive shaft 68 received within the shaft 18 and protruding distally therebeyond. The interior surface of the interconnector 64 defines a ledge 70 adjacent the interconnector distal end against

SUBSTITUTE SHEET which the cutter head shoulder 32 is positioned when the entirety of the cutter head 10 is mounted to a cutting instrument such as the surgical shaver device 12 depicted in Fig. 1. Figs. 9-12 illustrate an alternative aspect of the invention, in which the cutter head 10 is comprised of a cutter member 24 that is adapted to be received within a cutter sheath 26 so as to be at least partially surrounded thereby. The cutter member 24 is comprised of a cutter head 28 from which extends at a proximal end thereof a shank 30 having appropriate means such as gear teeth 33 for receiving rotational driving input in the manner described above. A shoulder 32 is provided along the exterior surface 39 of the cutter member to inhibit proximal displacement of the cutter head by cooperating with means such as interconnector ledge 70 (Fig. 8) . The cutter member and sheath 24 and 26 are provided with generally cylindrical cross-sectional configurations and are dimensioned such that the outer diameter "d" (Fig. 10) of the head 28 of the cutter member 24 is of a lesser value than is the inner diameter "D" of the sheath 26. The head of the cutter member 24 is inhibited from longitudinal displacement in a distal direction by an inwardly-extending flange 74 (Fig. 11) formed at the distal end of the sheath 26.

A cutting edge 46 is formed along the free end 76 of a tab 78 which extends radially outwardly from a portion of the periphery 80 of the cutter member head distal end 36. The tab 78 can be configured so as to preferably extend at an angle of from about 5^* to about 70^* from the plane defined by the cutter head member distal end 36, thereby positioning the cutting edge at the distal-most end of the instrument. An aperture 40 is preferably formed in the cutter head member distal end 36 at a position adjacent the tab cutting edge 46. Preferably, the tab 78 is formed from a section of the

SUBSTITUTE SHEET distal end 36 that is displaced outwardly therefrom, as can be accomplished by forming a distal end cutout in the form of a tab 78 and distally displacing the tab therefrom so that the tab remains attached to the distal end along the periphery thereof. The tab cutting edge 46 is formed in any of a variety of conventional manners, such as by grinding or otherwise removing material from the tab free end 76. Preferably, the tab as initially formed from the distal end is oversized with respect to its final dimensions, to permit for formation of the cutting edge in a manner which reduces the tab length of on the order of up to about 50% or more, thereby providing an aperture/tab relationship which facilitates both the tab displacement of material into the aperture as well as the ability of the aperture to receive material of various dimensions that is cut by the tab edge 46. The cutting edge can be provided with a variety of contours in accordance with the nature of the procedure to be performed and user preference. The cutting edge is characterized by the angle α that is illustrated in Fig. 12. With reference to the drawing, the cutting angle α is characterized as the angle which extends from the plane of the distal end 36 to the cutting edge surface 92. Preferably, this angle extends in the range of from about 5^* to about 70^*. As can be appreciated from the foregoing description and drawing illustration, as the angle α is decreased, the rake or angle of the cutting edge is diminished, resulting in a cutting edge that is better adapted for material slicing rather than abrading. Correspondingly, as the angle is increased, the edge becomes more broad in profile, rendering it better suited to abrading types of material cutting.

The foregoing detailed description is illustrious of various embodiments of cutter head arrangements of the subject invention. It is to be appreciated from the

E foregoing detailed description and accompanying_^drawings that variations and changes that can be made to the invention as set forth hereinabove are expressly intended to be encompassed by this description and the accompanying claims.

_SUBSTITUTE SHEET

Claims

WHAT IS CLAIMED IS:

1. A cutter head for use with a power driven material removal instrument, comprising: cutting means including a cutter member having at least one cutting element formed along an exterior surface of the cutter member; aperture means extending from said cutting element for receiving material cut by said cutting element; and passage means in fluid communication with said aperture means for receiving cut material from the aperture means for transport therefrom upon application of negative pressure to said passage means, said cutting element being positioned relative to said aperture means extending therefrom to direct material as it is cut into said aperture means.

2. The cutter head according to claim 1, further comprising means for coupling said cutting means to a source of rotational drive input.

3. The cutter head according to claim 2, wherein said coupling means and said cutting means are formed as an integral member.

4. The cutter head according to claim 2, further comprising means for inhibiting longitudinal displacement of said cutting means in at least a single direction.

5. The cutter head according to claim 4, wherein said displacement inhibiting means comprises a sheath which at least partially surrounds at least a portion of said cutting means.

SUBSTITUTE SHEET

6. The cutter head according to claim 1, wherein said cutting element comprises a slot including first and second edges formed along said exterior surface of the cutting member, at least one of said edges being provided with a sharpened surface.

7. The cutter head according to claim 6, wherein said edges are arranged in a non-parallel configuration.

8. The cutter head according to claim 6, wherein said slot is provided with a generally semi-helically fluted configuration.

9. The cutter head according to claim 6, wherein at least one of said edges is arranged substantially parallel to a longitudinal axis of the cutting means.

10. The cutter head according to claim 6, wherein said edges are positioned parallel to one another.

11. The cutter head according to claim 10, wherein said edges are positioned along a distal end of the cutter member.

12. The cutter head according to claim 11, wherein said sharpened edge is provided along a tab which extends outwardly from said cutting member distal end.

13. The cutter head according to claim 12, wherein said tab extends from said cutting member distal end at an angle of from about 5^* to about 70^* with respect to the plane along which said cutting member distal end is positioned.

14. The cutter head according to claim 13, wherein the plane of said cutting member distal end is oriented

_SUBSTITUTE SHEET generally transversely with respect to the longitudinal axis of the cutting member.

15. The cutter head according to claim 13, wherein said cutting member distal end is oriented at an angle of from about 5^* to about 70^* with respect to the longitudinal axis of the cutting member.

16. The cutter head according to claim 6, wherein a plurality of slots are provided along said cutting member exterior surface.

17. The cutter head according to claim 15, wherein said slots total at least three in number and are arranged such that two of said slots are substantially evenly spaced from the third slot.

18. The cutter head according to claim 16, wherein said plurality of slots are asymmetrically arranged along said cutting member exterior surface.

19. The cutter head according to claim 16, wherein said aperture means extends from at least two of said plurality of slots.

20. The cutter head according to claim 6, wherein at least one of said slot edges is formed by electron discharge machining of the cutting means.

21. The cutter head according to claim 6, wherein at least one of said slot edges is formed by rotary cutting of the cutting means.

22. The cutter head according to claim 1, wherein at least said cutter head cutting means is configured as a disposable member for use with a single patient.

23. The cutter head according to claim 1, wherein at least said cutter head cutting means is formed from a stainless steel metal alloy.

24. A method for removing material from a work surface, comprising the steps of: advancing a cutting member having at least one cutting edge against the work surface so as to engage and remove material from the work surface; directing the removed material with said cutting edge into an aperture formed in said cutting member and extending from said cutting edge as it is removed from the work surface; applying negative pressure through said aperture to draw the material removed from the work surface away from said aperture and into a passage formed in said cutting member and positioned in fluid communication with said aperture to thereby provide an evacuation path for the withdrawal of material removed from the work surface.

25. The method according to claim 24, wherein the work surface comprises an exterior surface of an organism.

26. The method according to claim 24, wherein the work surface comprises a body structure underlying an exterior surface of an organism.

27. The method according to claim 24, wherein said cutting member is a rotatably driven cutting member.

28. The method according to claim 27, wherein said cutting member is angularly oriented with respect to a supply of rotational driving input thereto.

SUBSTITUTE SHEET

29. The method according to claim 28, wherein said angular orientation of said cutting member is in the range of from about 90^* to about 180^* relative to a longitudinal axis of the supply of rotational driving input.

30. The method according to claim 27, wherein a plurality of cutting edges are provided along said cutting member.

31. The method according to claim 30, wherein said plurality of cutting edges are asymmetrically positioned on said cutting member relative to a plane extending through a longitudinal axis of the cutting member.

32. The method according to claim 30, wherein said cutting member is provided with at least three cutting edges and said negative pressure is applied to draw material removed by said cutting edges through apertures extending from at least two of said cutting edges.

33. The method according to claim 30, wherein at least two of said cutting edges are formed in said cutting member so as to extend along respective lines that are generally parallel to a longitudinal axis of said cutting member.

34. The method according to claim 27, wherein said cutting edge extends at an angle of from about 5^* to about 70^* with respect to a distal end of the cutting member.

35. The method according to claim 34, wherein said cutting member distal end extends at an angle of from about 5^* to about 70^* with respect to a plane

SUBSTITUTE SHEET perpendicularly bisecting the longitudinal axis of the cutting member.

36. The method according to claim 24, wherein at least said cutting edge is formed from a stainless steel alloy.

37. The method according to claim 24, wherein said cutting edge is formed by an electron discharge machining process applied to said cutting member.

38. The method according to claim 24, wherein said cutting edge is formed by advancing a rotatable cutting tool against said cutting member.

39. The method according to claim 24, wherein said passage is oriented along an axis generally parallel to a longitudinal axis of said cutting member.

40. The method according to claim 24, wherein said cutting member is configured as a single use, disposable instrument for use with a single patient only.

SUBSTITU TZ SHEE^"