Patent Description:
Medical practitioners have found it useful to use ultrasonic surgical instruments to assist in the performance of certain surgical procedures. An ultrasonic surgical instrument is designed to be applied to a surgical site on a patient. The practitioner positions the ultrasonic surgical instrument at the site on the patient at which the ultrasonic surgical instrument is to perform a medical or surgical procedure. Generally, an ultrasonic surgical instrument includes an ultrasonic handpiece that contains at least one piezoelectric driver. An ultrasonic tip is used in conjunction with the ultrasonic handpiece for removing tissue, specifically fibrous, elastic, tenacious and tough tumor tissue that is difficult to remove with currently available surgical instruments. In at least one type of surgical procedure, surgeons use the ultrasonic surgical instrument to precisely remove tumor tissue.

Known ultrasonic tips typically have a threaded connecting end and a contacting end. The threaded connecting end attaches to the ultrasonic handpiece which provides ultrasonic vibrational motion into the tip and further allows for aspiration through the tip. An ultrasonic tool system typically includes a control console. The control console supplies a drive signal to the ultrasonic handpiece. Upon the application of the drive signal to the driver, the driver cyclically expands and contracts. The expansion/contraction of the driver induces a like movement in the tip and more, particularly, the head of the tip. The energy causes the tip to move, such that the tip is considered to vibrate. The vibrating head of the tip is applied against tissue in order to perform a specific surgical or medical task. For example, some tip heads are applied against hard tissue. One form of hard tissue is bone. When this type of tip head is vibrated, the back and forth vibrations of teeth of the tip, saw, remove, the adjacent hard tissue. Still other tips are designed to ablate and remove soft tissue. Such tips are often designed to induce cavitation in and/or mechanically dissect soft tissue.

For an ultrasonic surgical instrument, sometimes called a handpiece or tool, to efficiently function, a drive signal having the appropriate characteristics should be applied to the tool. If the drive signal does not have the appropriate characteristics, a head of the tip may undergo vibrations of less than optimal amplitude and/or may not vibrate at the maximum amplitude possible. If the handpiece is in either state, the ability of the handpiece to, at a given instant, remove tissue may be appreciably reduced. One way of ensuring an ultrasonic handpiece operates efficiently is to apply a drive signal to the handpiece that is at the resonant frequency of the handpiece. The application of the drive signal at this frequency induces vibrations in the tip that are at a maximum amplitude.

In use, the surgeon or assistant, first installs the tip within a mating end of an acoustic horn of the ultrasonic driver of the ultrasonic handpiece. This is accomplished by screwing the tip into the mating end and applying the proper torque. Once installed, the surgeon may, if desired or necessary for the surgery, place an irrigation sleeve or flue around the tip aft of the contacting end before the operation begins. The irrigation sleeve allows the handpiece to provide irrigation fluid to the surgical site through the ultrasonic handpiece. During the surgical procedure, the surgeon places the contacting end onto or near the tissue or tumor which he or she desires to remove. Once placed, the surgeon then energizes the ultrasonic handpiece and the vacuum aspiration system if desired. The ultrasonic energy transmitted to the contacting end then creates an ultrasonic field relative to the axis of the tip. This field is of such energy that the liquid or tissue surrounding it cavitates and/or breaks down. The tip also resects fibrous tissue. This allows for removal of the material through the interior tube portion of the tip via the vacuum aspiration.

While suitable for some applications, surgeons have found that the fibrous tissue removal rate of currently available ultrasonic tips and devices in not adequate for certain tissues, including some tumors. It has also been found that, with use of standard ultrasonic tips, the fibrous and tough tissue can become tougher, and further impede removal. Overall, the devices that are currently used are inadequate at removing certain fibrous tumors in terms of control of removal and time to remove. Therefore, there is a need in the art to provide a new ultrasonic tip and an ultrasonic surgical instrument having the ultrasonic tip for fibrous tissue removal for use on a patient.

An ultrasonic horn for use with an ultrasonic surgical hand piece including a resonator comprises a contacting annulus having a plurality of angled lands is described in <CIT>. The lands are alternated around the annulus such that adjacent lands have opposite angles. As a result of the adjacent angled lands, a shear stress field is developed in contacted tissue due to the promotion of refracted longitudinal ultrasonic waves propagating in different directions at the interface to the coupled tissue. The shear stress field enhances the fragmentation and removal rate of fibrous, elastic, and tenacious tissue. The horn is hollow permitting suction to be applied to the tissue for controlling tissue contact with the lands.

The present description exemplary provides an ultrasonic tip for a surgical instrument for use on a patient including a head portion adapted to be coupled to a shaft to be applied to a surgical site of a patient, the head portion extending axially along an axial axis to a distal end, the distal end having a cutting edge with a positive rake angle relative to the axial axis for cutting tissue at the surgical site of the patient.

The present description also exemplarily provides a surgical instrument for use on a patient including a shaft extending axially between a proximal end and a distal end. The surgical instrument also includes an ultrasonic tip coupled to the distal end of the shaft to be applied to a surgical site of a patient and having a head portion extending axially along an axial axis to a distal end, the distal end of the ultrasonic tip having a cutting edge with a positive rake angle relative to the axial axis for cutting tissue at the surgical site of the patient.

The present description further exemplarily provides a method of operating a surgical instrument having an ultrasonic tip including the steps of applying a signal to the surgical instrument and ultrasonically exciting an ultrasonic tip of the surgical instrument, moving the ultrasonic tip into contact with tissue at a surgical site of a patient, the ultrasonic tip having a head portion extending axially along an axial axis to a distal end, the distal end of the ultrasonic tip having a cutting edge with a positive rake angle relative to the axial axis, and cutting fibers in the tissue against the positive rake angle of the cutting edge of the head portion of the ultrasonic tip.

A surgical instrument according to the present invention, having a shaft and a positive rake angle cutting edge ultrasonic tip is defined in claim <NUM>. One advantage is that said new ultrasonic tip is provided for fibrous tissue removal for use on patients. Another advantage of the present invention is that the surgical instrument having the ultrasonic tip allows for the removal of fibrous tissue, primarily fibrous and tough tumor tissue, that is otherwise difficult or not possible to remove safely. Yet another advantage of the present invention is that the surgical instrument having the ultrasonic tip enables controlled removal of fibrous tissue with significantly increased resection rates because the tissue is efficiently cut and resected. Still another advantage of the present invention is that, when the surgical instrument having the ultrasonic tip is applied, the fibrous tissue does not become tougher and therefore harder to resect.

A further advantage of the present invention is that the ultrasonic tip has a distal end utilizing positive rake angle cutting edges to achieve efficient resection of fibrous tissue. Yet a further advantage of the present invention is that the ultrasonic tip preferably has a distal end with outer edges of distal end geometry that enable efficient fiber cutting. Still a further advantage of the present invention is that the ultrasonic tip preferably has a distal end with torsional motion of the distal end or a combined longitudinal and torsional motion that enables greater cutting ability. Yet still a further advantage of the present invention is that the ultrasonic tip preferably has a positive rake angle cutting edge at the inner diameter that causes slicing of the tissue when it is pulled into a central lumen, the size of the resected tissue being no greater than an inner diameter of the tip resulting in reduced chance of clogging of the suction path.

Another advantage of the present invention is that the ultrasonic tip preferably has distal end surfaces that may be orientated on different planes to each other and the sides of the distal portion of the tip may not be perpendicular. Yet another advantage of the present invention is that the ultrasonic tip may be coated with a coating to reduce friction between the tip and the tissue and maintain a sharp cutting edge. Still another advantage of the present invention is that the surgical instrument with an ultrasonic tip allows for faster removal of tumor tissue and therefore a corresponding reduction in surgery time.

Other features and advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description.

Referring to <FIG> and <FIG>, one embodiment of a surgical instrument <NUM>, is shown for use in a medical procedure for a patient (not shown). As illustrated, the surgical instrument <NUM> includes a horn or shaft, generally indicated at <NUM>, extending between a proximal end and a distal end, an ultrasonic oscillation mechanism <NUM> at the proximal end, and an ultrasonic tip, and generally indicated at <NUM>, at the distal end for fibrous tissue removal on the patient. The fibrous tissue may include tumor locations on the brain, spinal cord, or other critical anatomy of the patient, including tumor removal in neurosurgery. It should be appreciated that the ultrasonic oscillation mechanism <NUM> produces ultrasonic wave oscillation for the ultrasonic tip <NUM>. It should also be appreciated that an example of such an ultrasonic oscillation mechanism is disclosed in <CIT>. It should further be appreciated that the surgical instrument <NUM> may be operated by a user (not shown) such as a surgeon.

Referring to <FIG>, the shaft <NUM> is a generally hollow cylinder and has a generally circular cross-sectional shape. The shaft <NUM> extends axially along a central axis from the proximal end to the distal end and has a proximal portion <NUM>, a middle portion <NUM>, and a distal portion <NUM>, respectively. The proximal portion <NUM> has a diameter greater than a diameter of the middle portion <NUM> and the middle portion <NUM> has a diameter greater than a diameter of the distal portion <NUM>. In this embodiment, the distal portion <NUM> is tapered toward the ultrasonic tip <NUM>. The shaft <NUM> has a passageway or central lumen <NUM> extending axially therethrough from the proximal end to the ultrasonic tip <NUM>. The proximal portion <NUM> has a connecting portion <NUM> extending axially for connection to the ultrasonic oscillation mechanism <NUM>. It should be appreciated that the ultrasonic oscillation mechanism <NUM> is connected to the connecting portion <NUM> of the proximal portion <NUM> of the shaft <NUM>. It should also be appreciated that the shaft <NUM> has an external geometry profile that results in a vibrational amplitude gain along a length thereof to the ultrasonic tip <NUM>. It should further be appreciated that the shaft <NUM> may be linear or arcuate in shape.

The shaft <NUM> is made of a metal material such as titanium alloy, stainless steel, etc. or a non-metallic material such as a composite, depending on the application. The shaft <NUM> is integral, unitary, and one-piece. In one embodiment, the shaft <NUM> and tip <NUM> may be integral, unitary, and one-piece. In another embodiment, the distal end of the tip <NUM> may be attached to the shaft <NUM> by a suitable mechanism such as threads (not shown). It should be appreciated that metals are known in the art regarding high power ultrasonic components. It should also be appreciated that the diameters of the distal portion <NUM> of the shaft <NUM> and the ultrasonic tip <NUM> have a relatively small diameter, for example less than one centimeter (<NUM>), so as to work in a small opening of the patient. It should further be appreciated that the shaft <NUM> and ultrasonic tip <NUM> may be scaled larger or smaller depending on the application.

The surgical instrument <NUM> also includes a vibration conversion mechanism, generally indicated at <NUM>, in the middle portion <NUM> of the shaft <NUM> for converting the vibration transmitted from the ultrasonic oscillation mechanism <NUM> into a (longitudinal-torsional) composite vibration composed of a longitudinal vibration in the central axial direction of the shaft <NUM> and a torsional vibration having the central axis of the shaft <NUM> as a fulcrum in the vicinity of the distal portion <NUM>. In one embodiment, the vibration conversion mechanism <NUM> includes a plurality of grooves <NUM> formed to be wound around the circumferential surface of the middle portion <NUM> of the shaft <NUM>. It should be appreciated that the vibration conversion mechanism <NUM> can be located at other portions of the shaft <NUM> and have other designs.

Referring to <FIG>, the ultrasonic tip <NUM> includes a connecting or transition portion <NUM> and a head or contacting portion <NUM> extending axially from the transition portion <NUM>. The transition portion <NUM> tapers axially and radially outward. The transition portion <NUM> is hollow and communicates with the passageway <NUM>. The head portion <NUM> extends axially. The head portion <NUM> is generally hollow and circular in cross-sectional shape. The head portion <NUM> is open and communicates with the transition portion <NUM> and the passageway <NUM>. The head portion <NUM> has a constant diameter greater than a diameter of the end of the distal portion <NUM> of the shaft <NUM>.

The ultrasonic tip <NUM> also includes a plurality of teeth <NUM> formed at a distal end of the head portion <NUM>. The teeth <NUM> are formed by cuts or slots <NUM> extending into and through a wall of the head portion <NUM> to space the teeth <NUM> circumferentially about the head portion <NUM> for a function to be described. The depth of the slots <NUM> at an outer surface of head portion <NUM> of the ultrasonic tip <NUM> is greater than that at an inner surface, resulting in a sloped surface that creates a positive rake angle cutting edge at the inner surface.

In this embodiment, the slots <NUM> are created along a purely axial direction to extend axially relative to a tip or axial axis <NUM>. The head portion <NUM> may include any number of teeth <NUM>. One method of forming the distal end geometry is with a rotary cutting disc (not shown). It should be appreciated that the cutting geometry incorporates an axial pattern of slots <NUM> on the distal end of the ultrasonic tip <NUM> such that positive rake angles are created between the outer surface and the side surface defining the slots <NUM>. It should also be appreciated that the ultrasonic tip <NUM> has a distal end geometry that, in combination with an ultrasonic vibrational motion, results in a significant increase in the resection rate of fibrous tissue.

As illustrated in <FIG>, the teeth <NUM> have a distal end <NUM>, a side cutting edge <NUM>, an inner cutting edge <NUM>, and a distal cutting edge <NUM>. The distal ends <NUM> of the teeth <NUM> are generally triangular in shape as opposed to square, resulting in a sharp cutting point at the outer surface and of a single inner cutting edge <NUM>. The distal cutting edge <NUM> has a positive rake angle. In the embodiment illustrated, the teeth <NUM> are arranged so that the cutting edges <NUM>, <NUM>, and <NUM> are all in the same direction and are all in the same axial pattern. In the embodiment illustrated, the surfaces of the distal ends <NUM> are planar or orientated in the same plane. Also, the sides of the distal portion <NUM> are perpendicular. The slots <NUM> are defined on the outer surface by the side cutting edge <NUM> that has a straight axial section and an arcuate section and a relief edge <NUM>. The slots <NUM> are defined on the inner surface by the inner cutting edge <NUM> that has an arcuate section that joins with a straight axial relief edge <NUM>. It should be appreciated that a relief surface is defined between the relief edges <NUM> and <NUM>. It should also be appreciated that, when the distal cutting edge <NUM> receives torsional motion as indicated by the arrow <NUM> in <FIG>, the distal cutting edge <NUM> meets the tumor with an obtuse angle to create a positive rake angle and cutting action will occur.

The ultrasonic tip <NUM> may be coated with a suitable coating, for example, such as Titanium Nitride (TiN) or a diamond like coating (DLC). It should be appreciated that the ultrasonic tip <NUM> achieves the highest resection rate when the distal end <NUM> of the teeth <NUM> of the head portion <NUM> is vibrating in a torsional or a combined longitudinal and torsional motion. It should further be appreciated that the highest resection rate of the surgical instrument <NUM> occurs when the motion of vibration is perpendicular to the positive rake angle cutting edge of the ultrasonic tip <NUM>.

A control console (not shown) is also part of the system. The control console sources drive signals over a cable (not shown) to the surgical instrument <NUM>. The drive signals are applied to drivers (not shown). At any given instant, the same drive signal is applied to each driver. The application of the drive signals causes the drivers to simultaneously and cyclically expand and contract. A stack of drivers is often between <NUM> and <NUM> in length. The distance, the amplitude, of movement over a single expansion/contraction cycle of the drivers may be between <NUM> and <NUM> microns. The shaft <NUM> amplifies this movement. Consequently, the distal end of the shaft <NUM> and, by extension, the head portion <NUM> of the ultrasonic tip <NUM> when moving from the fully contracted position to the fully extended position moves typically a maximum of <NUM> microns and more often <NUM> microns or less for tips <NUM> made of titanium alloy. It should be appreciated that the tip <NUM> may be further designed so that the longitudinal extension/retraction of the tip stem also induces a rotational movement in the head portion <NUM>. It should also be appreciated that, often, when the shaft <NUM> is in a cyclical movement to cause the cyclic movement of the tip <NUM>, the head portion <NUM> is considered to be vibrating.

In operation, the ultrasonic tip <NUM> is ultrasonically excited by the ultrasonic oscillation mechanism <NUM> and the vibration conversion mechanism <NUM>. The vibrational amplitude at the end of the ultrasonic tip <NUM> can be in the range of <NUM> microns peak to peak. There can be suction through the central lumen <NUM> which aids in coupling the tissue to the ultrasonic tip <NUM>. The distal end <NUM> of the teeth <NUM> of the head portion <NUM> of the ultrasonic tip <NUM> is brought into contact with the tissue. Ablation of the tissue occurs in part due to methods common to standard ultrasonic aspirators (cavitation, pressure waves, mechanical impact). This occurs when the tissue is in close proximity to the vibrating surfaces. High intensity ultrasonic fields exist within the slots <NUM> of the vibrating head portion <NUM> of the ultrasonic tip <NUM>. The optimal motion of the distal end <NUM> of the teeth <NUM> is illustrated by arrow A (solid lines) and the motion at the bottom of the teeth <NUM> is illustrated by arrow B (dotted lines) in <FIG>. It should be appreciated that a resection mechanism for the ultrasonic tip <NUM> is of mechanical cutting of the fibers in the tissue against the positive rake angled edges of the teeth <NUM>. It should also be appreciated that the ultrasonically oscillating edges of the teeth <NUM> impact the tissue fibers and impart stresses that result in cutting of the fibers. It should further be appreciated that the edges <NUM>, <NUM>, and <NUM> of the ultrasonic tip <NUM> allow for efficient cutting of fibrous tissue and in combination with the common ultrasonic ablation mechanisms and controlled suction result in controlled resection of the tissue.

With the depth of the slots <NUM> at the outer surface of the ultrasonic tip <NUM> greater than that at the inner surface, resulting in a sloped surface, the vibrating sharp edge at the inner surface causes slicing of the tissue when it is pulled into the central lumen <NUM> of the shaft <NUM>. The size of the resected tissue is no greater than an inner diameter of the ultrasonic tip <NUM>, resulting in reduced chance of clogging of the suction path. Due to the oscillatory ultrasonic vibration, the tissue is not wrapped around the ultrasonic tip <NUM> and controlled resection can occur without unwanted strain on the bulk of the tissue. It should be appreciated that sharp cutting edges <NUM>, <NUM>, and <NUM> of the teeth <NUM> ensure clean cuts and minimize dragging of the bulk tissue.

With the depth of the slots <NUM> at the outer surface of the ultrasonic tip <NUM> greater than that at the inner surface, resulting in a sloped surface, the air flow through the sides of the tip <NUM> is reduced when suction is applied. This allows for reduced suction loss and better coupling of the ultrasonic tip <NUM> with the tissue. The depth of the slots <NUM> at the outer surface of the ultrasonic tip <NUM> greater than that at the inner surface, resulting in a slope surface, also controls the depth the tip <NUM> can intrude into the tissue before slicing of the tissue at the inner edge <NUM> occurs. It should be appreciated that this feature also results in minimizing unwanted strain on the bulk of the tissue.

Referring to <FIG>, another embodiment, according to the present invention, of the surgical instrument <NUM> is shown. Like parts of the surgical instrument <NUM> have like reference numerals increased by one hundred (<NUM>). In this embodiment, the surgical instrument <NUM> includes the shaft <NUM>, extending between a proximal end and a distal end, the ultrasonic oscillation mechanism <NUM> at the proximal end, and the ultrasonic tip <NUM>, at the distal end for fibrous tissue removal on the patient. The shaft <NUM> includes the proximal portion <NUM>, the middle portion <NUM>, and the distal portion <NUM>. The shaft <NUM> also includes the passageway <NUM> extending axially therethrough from the proximal end to the ultrasonic tip <NUM>. It should be appreciated that the surgical instrument <NUM> also includes the vibration conversion mechanism <NUM> in the middle portion <NUM> of the shaft <NUM> for converting the vibration transmitted from the ultrasonic oscillation mechanism <NUM>.

Referring to <FIG>, the ultrasonic tip <NUM> includes the transition portion <NUM> and the head portion <NUM> extending axially from the transition portion <NUM>. The ultrasonic tip <NUM> includes a plurality of teeth <NUM> formed at the distal end of the head portion <NUM>. The teeth <NUM> are formed by cuts or slots <NUM> extending into and through a wall of the head portion <NUM> to space the teeth <NUM> circumferentially about the head portion <NUM>. The depth of the slots <NUM> at an outer surface of the ultrasonic tip <NUM> is greater than that at the inner surface, resulting in a sloped surface that creates a positive rake angle cutting edge at the inner surface. In this embodiment, the slots <NUM> are created at an offset angle (in this case the cutting edge at the outer surface is at an acute angle along the outer surface that is parallel to the tip axis <NUM>). The head portion <NUM> may include any number of teeth <NUM>. It should be appreciated that the cutting geometry incorporates an axial pattern of slots <NUM> on the distal end of the ultrasonic tip <NUM> such that positive rake angles are created between the outer surface and the side surface of the slots <NUM>.

As illustrated in <FIG>, the teeth <NUM> have a distal end <NUM>, a side cutting edge <NUM>, an inner cutting edge <NUM>, and a distal cutting edge <NUM>. The distal ends <NUM> are generally triangular in shape as opposed to square, resulting in a sharp cutting point at the outer diameter and of a single distal cutting inner edge. In this embodiment, the teeth <NUM> are arranged so that the cutting edges <NUM>, <NUM>, and <NUM> vary in direction and are not all in the same axial pattern. In the embodiment illustrated, the surfaces of the distal ends <NUM> are oriented on different planes to each other. In the embodiment illustrated, the sides of the distal portion <NUM> are not perpendicular to ensure efficient cutting and snagging of the underlying tissue. It should also be appreciated that, when the distal cutting edge <NUM> receives torsional motion as indicated by the arrow <NUM> in <FIG>, the distal cutting edge <NUM> meets the tumor with an obtuse angle to create a positive rake angle, cutting action will occur.

The ultrasonic tip <NUM> may be coated with a suitable functional coating, for example, such as Titanium Nitride (TiN) or a diamond like coating (DLC). The optimal motion of the distal end <NUM> of the teeth <NUM> is illustrated by arrow A (solid lines) and the motion at the bottom of the teeth <NUM> is illustrated by arrow B (dotted lines) in <FIG>. It should be appreciated that the ultrasonic tip <NUM> achieves the highest resection rate when the distal portion <NUM> is vibrating in a torsional or a combined longitudinal and torsional motion. It should further be appreciated that the highest resection rate of the surgical instrument <NUM> occurs when a component of the motion of vibration is perpendicular to the positive rake angle cutting edge of the ultrasonic tip <NUM>. It should still further be appreciated that the operation of the surgical instrument <NUM> is similar to the operation of the surgical instrument <NUM>.

In addition, herein disclosed is a method of operating the surgical instrument <NUM>, <NUM> having the ultrasonic tip <NUM>, <NUM>. The method includes the steps of applying a signal to the surgical instrument <NUM>, <NUM> and ultrasonically exciting an ultrasonic tip <NUM>, <NUM> of the surgical instrument <NUM>, <NUM> and moving the ultrasonic tip <NUM>, <NUM> into contact with tissue at a surgical site of a patient. The ultrasonic tip <NUM>, <NUM> has a head portion <NUM>, <NUM> extending axially along an axial axis <NUM>, <NUM> to a distal end, the distal end of the ultrasonic tip <NUM>, <NUM> having a cutting edge <NUM>, <NUM> with a positive rake angle relative to the axis <NUM>, <NUM>. The method also includes cutting fibers in the tissue against the positive rake angle of the cutting edge <NUM>, <NUM> of the head portion <NUM>, <NUM> of the ultrasonic tip <NUM>, <NUM>. It should be appreciated that the method includes other steps.

Accordingly, the surgical instrument <NUM>, <NUM> incorporates an ultrasonic tip <NUM>, <NUM> having teeth <NUM>, <NUM> with positive rake angles. When the slots <NUM>, <NUM> are perpendicular to the direction of vibration of the ultrasonic tip <NUM>, <NUM> higher resection rates can be obtained. When the surfaces of the distal end <NUM>, <NUM> of the teeth <NUM>, <NUM> of the ultrasonic tip <NUM>, <NUM> are orientated on different planes to each other, a reduction in the contact area and pressure against the tissue could be achieved. This could result in a reduction in the frictional heating between the tip surface and the tissue. When the sides of the distal portion <NUM>,<NUM> of the ultrasonic tip <NUM>, <NUM> are not perpendicular, then a reduction in the contact area and pressure against the tissue could be achieved. This could result in a reduction in the frictional heating between the tip surface and the tissue.

The invention has been described in an illustrative manner and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings.

Claim 1:
A surgical instrument (<NUM>) comprising:
a shaft (<NUM>) extending axially between a proximal end and a distal end and defining a central lumen, the central lumen configured for applying suction to tissue; and
an ultrasonic tip (<NUM>) coupled to the distal end of the shaft (<NUM>) and including a head portion (<NUM>) extending axially along an axial axis (<NUM>) to a distal end (<NUM>),
wherein the ultrasonic tip (<NUM>) has a cutting edge with a positive rake angle relative to the axial axis (<NUM>), said cutting edge configured to cut tissue,
wherein the head portion (<NUM>) includes a plurality of teeth (<NUM>) and a plurality of slots (<NUM>) separating the teeth (<NUM>),
wherein the slots (<NUM>) are at an offset angle to the axial axis (<NUM>).