Protective sheath and method for ultrasonic probes

In general a protective sheath for an ultrasonic fragmenting device includes a handpiece to be held and manipulated by a surgeon. The handpiece has a housing, an ultrasonic motor mounted therewithin, and an ultrasonic horn connected to the ultrasonic motor. An elongate ultrasonic probe is attached to the ultrasonic horn. The elongate ultrasonic probe has an outer surface about and along its length and has one or more vibratory nodes spaced along the length of the ultrasonic probe as a function of the resonant wavelength. The ultrasonic fragmenting device includes the protective sheath with a hollow sleeve with a proximal end and a distal end and which surrounds the elongate ultrasonic probe and extends therealong. The hollow sleeve has an inner surface formed, shaped, and sized to prevent contact with the outer surface of the elongate ultrasonic probe so that there is generally a clearance between the inner surface and the outer surface. The hollow sleeve has a connection on the proximal end to connect the hollow sleeve to the housing and a termination on the distal end located at or near the most distal vibratory node of the elongate ultrasonic probe. The termination has an inside diameter that is generally and substantially the same as the outside diameter of the elongate ultrasonic probe thereabout, and thus forms generally a barrier to the passage of material into the clearance.

CROSS-REFERENCE TO RELATED APPLICATION
 Not Applicable.
 STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
 Not Applicable.
 REFERENCE TO A MICROFICHE APPENDIX
 Not Applicable.
 BACKGROUND OF THE INVENTION
 This invention relates generally to surgical instruments, and, more
 particularly, to a surgical device for ultrasonic fragmentation or
 emulsification of soft tissues of a patient.
 Liposuction is a surgical procedure for altering the human form,
 specifically by removal of localized deposits of fat tissues that are
 unresponsive to diet or exercise. The procedure is also known as suction
 lipectomy, lipolysis, and more recently as body contour surgery, body
 sculpting surgery, or suction-assisted liposuction. It is most often
 performed by plastic surgeons, although dermatologists, gynecologists, and
 other surgical specialties also perform such procedures.
 A liposuction procedure is typically accomplished by inserting a small
 cannula through an incision in the skin, applying a suction source to the
 end of the cannula that remains outside of the body, and forcing the
 working end of the cannula forward and backward in the layer of fatty
 tissue. The fatty tissue is torn, crushed, or avulsed, and is then
 aspirated through small openings along the sides of the cannula near the
 tip and then through a central lumen in the cannula to a tissue canister
 placed in-line with the cannula and the suction source. The procedure may
 involve multiple incisions and many passes of the cannula in each incision
 to achieve the desired cosmetic effect for the patient. No ultrasonic
 energy is used in this procedure.
 A liposuction cannula is typically a small metal tube with a blunt, closed
 end at the tip of the cannula. The blunt, closed end at the tip of the
 cannula is intended to minimize damage to tissues as the device is thrust
 forward. Small openings along the sides of the cannula near the tip create
 passages between the tissue and the central lumen of the cannula, which is
 in fluid communication with a suction source, so that tissue and fluids
 can be aspirated from the patient's body. In general, the suction causes
 the adipose tissue to be sucked into the small openings along the sides of
 the cannula, and the blunt dissection as provided by the surgeon's
 manipulation of the cannula, then tears the tissue. The fragments and
 released fluids are then aspirated through the openings along the sides of
 the cannula and then through the central lumen of the cannula.
 The liposuction procedure can be traumatic for the patient. The liposuction
 cannula does not discriminate between adipose tissue and other tissues
 such as nerves, blood vessels, or lymph tissues. The mechanical disruption
 of those tissues by the liposuction cannula may result in, among other
 things, bleeding, bruising, temporary numbness, or swelling. Further, the
 final cosmetic result achieved for the patient is a function of the skill
 of the surgeon, the patient, and the type of surgical instrumentation used
 in the surgery. Liposuction cannulae used in the liposuction procedure may
 remove more adipose tissue from one area than another area in the patient,
 resulting in skin contour irregularities and a final cosmetic result for
 the patient that is not smooth or uniform or desired.
 Therefore, there is a need to improve the design of liposuction cannulae to
 help the surgeon to better discriminate between adipose tissue and other
 tissues such as nerves, blood vessels, and lymph tissues, so that the
 adipose tissues can be fragmented and removed while the remaining tissues
 are damaged as little as possible or not at all. Further, there is a need
 to improve the design of current liposuction cannulae such that adipose
 tissue is removed in a uniform and predictable manner such that an
 improved cosmetic result is achieved for the patient.
 Recently, several instruments have combined ultrasonic vibrations and the
 liposuction cannula to improve upon the tissue discrimination capability
 of the liposuction cannula and to provide an instrument, which removes
 adipose tissue more uniformly than current liposuction cannulae. This
 procedure is commonly referred to as ultrasound-assisted lipoplasty. In a
 typical ultrasound-assisted lipoplasty procedure, an ultrasonically
 vibrating cannula is inserted through an incision in the patient's skin
 and passed forward and backward through the adipose tissue layer. The
 ultrasonically vibrating cannula preferentially fragments or emulsifies
 the adipose tissues, which are then typically aspirated through a central
 lumen in the ultrasonically vibrating cannula. Consequently, the other
 tissues such as nerves, vessels, and lymph tissues remain generally
 undisturbed.
 Initial experiences with the ultrasound-assisted lipoplasty procedure have
 been mixed. A comparison of the suction-assisted liposuction and
 ultrasound-assisted lipoplasty approaches with currently available
 surgical instruments for both procedures was recently given in
 Ultrasound-Assisted Lipoplasty Resource Guide, published in PlasticSugery
 News, a publication of The American Society of Plastic and Reconstructive
 Surgeons, 1997. In the article the author cites the disadvantages of the
 current ultrasound-assisted lipoplasty procedure compared to the
 suction-assisted liposuction procedure as: 1) burns of the skin are
 possible, 2) longer incisions are needed, 3) seromas are more common, 4)
 longer operating times, and 5) greater expense. Thus, current
 ultrasound-assisted lipoplasty surgical systems for fragmentation and
 aspiration of adipose tissues are more costly and slower than the
 suction-assisted liposuction procedure and have the potential to damage
 tissues beyond that of suction-assisted liposuction, including burns of
 the skin and seroma formation. There is, therefore, a need to increase
 patient safety, to increase the speed of the ultrasound-assisted
 lipoplasty procedure, and to minimize the potential for burns or seroma
 formation.
 An ultrasonic probe for soft tissue fragmentation may be hollow, in which
 case the instrument may be referred to as an ultrasonic cannula or it may
 be solid. The distal end of an ultrasonic probe experiences small rapid
 excursions along an axis that passes through the proximal end and the
 distal end of the ultrasonic probe. A maximum excursion of 350 .mu.m
 peak-to-peak at 23 kHz has been obtained in a commercially available
 ultrasonic aspirator for ultrasonic surgery, e.g., the CUSA of Valleylab
 Inc., Boulder, Colo.
 An ultrasonic handpiece typically has a handle with an ultrasonic motor, an
 ultrasonic horn, and an ultrasonic probe. At locations along the
 ultrasonic probe referred to as `vibratory nodes` the elastic stress and
 strain will have maximum values and there will be no motion of the
 ultrasonic probe relative to the handle of the ultrasonic handpiece. At
 locations along the ultrasonic probe referred to as `vibratory loops` the
 elastic stress and strain will have minimum values and there will be
 maximum motion of the ultrasonic probe relative to the handle of the
 ultrasonic handpiece. The `vibratory nodes` become hot as the ultrasonic
 probe vibrates at the resonant ultrasonic frequency because the metallic
 material of the ultrasonic probe is being continually worked as it is
 stretched and released many thousand times per second. In an
 ultrasound-assisted lipoplasty procedure tissue surrounds and contacts the
 ultrasonic probe along its length. Thus, tissue contact with a vibratory
 node after the probe has been in operation can cause a tissue burn. A
 tissue burn may also occur for any tissue that contacts a vibratory loop
 because of the frictional heat generated between the tissue and the
 rapidly moving ultrasonic probe at the vibratory loop. Further, the heat
 generated by the ultrasonic motor in the ultrasonic handpiece may be
 conducted from the ultrasonic motor through the ultrasonic horn to the
 ultrasonic probe, further increasing the temperature of the ultrasonic
 probe. The combination of these three sources of heat can and will cause
 tissue burns, most particularly at or near the vibratory loops.
 Many patents disclose improvements and solutions for ultrasound-assisted
 lipoplasty instruments for removal of adipose tissue from the human body.
 U.S. Pat. No. 4,886,491 to Parisi has a method of removing fatty tissue
 from a patient using an ultrasonic probe and its energy application to
 melt at least some of the fatty tissue. U.S. Pat. No. 5,244,458 to Takasu
 has an ultrasonic handpiece with a hollow cannula with a plurality of
 suction openings in that cannula. U.S. Pat. No. 5,236,414 also to Takasu
 has an ultrasonic handpiece with a tip having a tubular body and a suction
 passage. U.S. Pat. No. 5,419,761 to Narayanan has an ultrasonic handpiece
 with a rigid tube with an axially extending lumen. U.S. Pat. No. 5,514,086
 to Parisi has an ultrasonic handpiece with a probe and a tip on the probe.
 The tip has an acoustic impedance substantially greater than that of the
 probe. U.S. Pat. No. 5,527,273 to Manna has an ultrasonic lipectomy probe
 with an enlarged head on the distal end and a longitudinally extending
 channel in the probe. U.S. Pat. No. 5,123,903 to Quaid has an ultrasonic
 handpiece and horn, the ultrasonic horn protected by a sheath which forms
 an annular passage operarable to conduct fatty tissue aspirate from the
 distal end of the ultrasonic horn. The inner diameter of the sheath in
 this patent is sufficiently larger than the outer diameter of the
 ultrasonic horn so that the annular passage is functional for the passage
 of aspirated tissue and fluids, thus significantly increasing the overall
 diameter of the sheath. Further, the sheath terminates at the tip of the
 ultrasonic probe, which is a vibratory loop, thus shielding the tip of the
 ultrasonic probe and creating a dragging sensation for the surgeon. The
 end of the sheath is open and permits the flow of material into the
 annular passage. U.S. Pat. No. 4,808,154 to Freeman has cylindrical sleeve
 with at least one longitudinal rib member operable to conduct a lens
 flushing solution to the distal end of the ultrasonic probe. U.S. Pat. No.
 3,805,787 to Banko has an ultrasonic handpiece and probe with a shield of
 metallic material, the shield and probe, like many of the subsequent
 patent efforts, are such as to be operable for the delivery of irrigation
 fluid to the distal end of the probe or for the removal of aspirate from
 the distal end of the probe. U.S. Pat. No. 5,421,829 to Olichney has an
 ultrasonic handpiece with a flue that surrounds a tool to direct irrigant
 and coolant flow thereabout.
 The last four patents cited above disclose sleeves which protectively
 surround the ultrasonic probe, each sleeve operable for either the
 delivery an irrigation fluid to the distal end of the ultrasonic probe or
 for the removal of tissue aspirate from the distal end of the ultrasonic
 probe in the space created between the sleeve and the ultrasonic probe.
 These designs have three fundamental problems. First, when irrigation
 fluid or tissue aspirate is present in the space between the sleeve and
 the ultrasonic probe it significantly increases the power required by the
 ultrasonic motor to maintain a selected level of vibration amplitude due
 to the frictional contact between the ultrasonic probe and the irrigation
 fluid or tissue aspirate at the vibratory loops along the ultrasonic
 probe. This increased power requirement is expensive and cumbersome while
 causing the handle to quickly warm and become too hot to hold in a bare
 hand. Second, these sleeve designs terminate approximately at the distal
 end of the ultrasonic probe, which is a vibratory loop, and therefore have
 an outside diameter of the sleeve is larger than the outside diameter of
 the ultrasonic probe. This shielding of the ultrasonic probe makes passage
 of the ultrasonic probe and sleeve through the tissue difficult, creating
 a dragging sensation for the surgeon and generating trauma to the patient.
 Third, to achieve reasonable performance from either an irrigation system
 or an aspiration system that utilizes the space between the sleeve and the
 ultrasonic probe there must be sufficient clearance between the two so
 that resistance to flow is not too large. This increases the overall
 diameter of the sleeve so that a significantly larger incision is required
 in the patient.
 While some of the patented devices have disclosed and claimed improvements
 and solutions to ultrasound-assisted lipoplasty instruments, none address
 or appreciate the needs or address the problems discussed above.
 Specifically none address the need for a sleeve to protect the patient
 from burns while minimizing the power required by the ultrasonic motor and
 while minimizing the diameter of the sleeve to minimize the drag in the
 tissue and the size of the incision in the patient.
 OBJECTS OF THE INVENTION
 It is, among other desirable attributes, a general object of the present
 invention to provide a less traumatic ultrasonic handpiece for
 fragmentation or emulsification of soft tissues in a patient.
 It is a further object of the present invention to provide an improved
 ultrasonic handpiece for fragmentation or emulsification of soft tissues
 in a patient, which maximizes the protection of the patient from potential
 burns.
 It is still a further object of the present invention to provide an
 improved ultrasonic handpiece for fragmentation or emulsification of soft
 tissues in the patient that maximizes the protection of the patient from
 burns while minimizing the forces required to pass the ultrasonic probe
 through the tissues.
 It is yet still a further object of the present invention to provide an
 improved ultrasonic handpiece for fragmentation or emulsification of soft
 tissues in the patient that maximizes the protection of the patient from
 burns while minimizing size of the incision required to enter the patient.
 SUMMARY OF THE INVENTION
 Ultrasonic probes for fragmenting tissues of a patient are generally round
 in cross-section and typically have outside diameters between 1 and 5
 millimeters. If a protective sheath is used to surround an ultrasonic
 probe it must have an inside diameter generally greater than the outside
 diameter of the ultrasonic probe to prevent contact therebetween. In this
 disclosure the clearances between the protective sheath and the ultrasonic
 probe are the minimum values that would generally prevent contact between
 the protective sheath and the ultrasonic probe, and would therefore create
 a clearance between the protective sheath and the ultrasonic probe that
 would generally be ineffective for use as a passage for irrigation or
 aspiration. For example, differences between the inside diameter of the
 protective sheath and the outside diameter of the ultrasonic probe from
 0.01 to 0.50 millimeters are preferred.
 In general an ultrasonic fragmenting device with a protective sheath
 includes a handpiece to be held and manipulated by a surgeon. The
 handpiece is comprised of a housing, an ultrasonic motor mounted
 therewithin, and an ultrasonic horn connected to the ultrasonic motor. The
 preferred material for the ultrasonic motor is a piezoelectric ceramic
 such as PZT. An elongate ultrasonic probe is attached to the ultrasonic
 horn. The preferred material for the ultrasonic probe is titanium or a
 titanium alloy. Other metallic materials may be used such as stainless
 steel or aluminum. The elongate ultrasonic probe has an outer surface
 about and along its length and has vibratory nodes spaced along its length
 as a function of the resonant wavelength. The ultrasonic fragmenting
 device includes a protective sheath that has a hollow sleeve with a
 proximal end and a distal end that surrounds the elongate ultrasonic probe
 and extends therealong. The preferred material for the hollow sleeve is
 thin-walled stainless steel tubing. Polymeric or plastic materials may
 also be used. The hollow sleeve has an inner surface formed, shaped, and
 sized to prevent contact with the outer surface of the elongate ultrasonic
 probe. The hollow sleeve has a connection on the proximal end to connect
 the hollow sleeve to the housing and a termination on the distal end at or
 near the most distal vibratory node of the elongate ultrasonic probe. In
 the preferred embodiment the termination has a reduced inside diameter
 that is generally and substantially the same as the outside diameter of
 the elongate ultrasonic probe thereabout, and thus forms generally a
 barrier to the passage of material into a minimal clearance existent
 between the hollow sleeve and the elongate ultrasonic probe.
 In an alternative embodiment the ultrasonic probe may have a flange that
 circumscribes the elongate ultrasonic probe at or near its most distal
 vibratory node. The outside diameter of the flange is generally and
 substantially the same as the inside diameter of the hollow sleeve
 thereabout, and thus forms a barrier to the passage of material into a
 minimal clearance existent between the hollow sleeve and the elongate
 ultrasonic probe.
 In yet another embodiment the clearance between the inner surface of the
 hollow sleeve and the outer surface of the elongate ultrasonic probe may
 be sufficiently small so as to effectively form a barrier to the passage
 of material therewithin.
 Also claimed is a method of fragmenting or emulsifying a medium with
 axially applied ultrasonic vibrations, the method including the steps of:
 surrounding an elongate ultrasonic probe with a hollow sleeve, the hollow
 sleeve having an inner surface formed, shaped, and sized to prevent
 contact with the outer surface of the elongate ultrasonic probe and;
 terminating the hollow sleeve at or near the most distal vibratory node of
 the elongate ultrasonic probe, the termination such that the inside
 diameter of the hollow sleeve is generally and substantially the same as
 the outside diameter of the elongate ultrasonic probe thereabout for
 forming generally a barrier to the passage of material into a space
 created between the hollow sleeve and the elongate ultrasonic probe;
 vibrating an elongate ultrasonic probe along its length;
 engaging the medium with a distal end of the elongate ultrasonic probe, and
 fragmenting or emulsifying the medium with the distal end of the elongate
 ultrasonic probe.

DETAILED DESCRIPTION OF THE INVENTION
 A protective sheath 10 for an ultrasonic fragmenting device 11 is shown in
 FIG. 1. In general the ultrasonic fragmenting device 11 includes a
 handpiece 12 to be held and manipulated by a surgeon, the handpiece 12
 with a housing 13 and an ultrasonic motor 14 mounted therewithin. The
 preferred material for the ultrasonic motor is a piezoelectric ceramic
 such as PZT. The preferred method of mounting the ultrasonic motor 14
 within the housing 13 is to suspend the ultrasonic motor 14 on O-rings 28.
 An ultrasonic horn 15 is connected to the ultrasonic motor 14. The
 preferred materials for the ultrasonic horn are aluminum alloy 7075 or
 titanium alloy Ti6Al4V. An elongate ultrasonic probe 16 is attached to the
 ultrasonic horn 15, the elongate ultrasonic probe 16 has an outer surface
 17 about and along its length and vibratory nodes 18 spaced along its
 length as a function of the resonant wavelength. The preferred material
 for the elongate ultrasonic probe is titanium alloy Ti6Al4V. Other metals
 such as aluminum and stainless steel may also be used. Vibratory nodes 18
 are depicted in FIG. 1 by lines circumscribing the elongate ultrasonic
 probe 16.
 The protective sheath 10 has a hollow sleeve 19 with a proximal end 20 and
 a distal end 21 that surrounds the elongate ultrasonic probe 16 and
 extends therealong. The preferred material for the hollow sleeve is
 thin-walled stainless steel tubing. Plastic or polymeric materials may
 also be used. The hollow sleeve 19 has an inner surface 22 formed, shaped,
 and sized to prevent contact with an outer surface 17 of the elongate
 ultrasonic probe 16 so that there is generally a clearance 26
 therebetween. The hollow sleeve 19 has a connection 23 on the proximal end
 20 to connect to the housing 13. The preferred connection 23 is a snap-fit
 or a twist-lock between the hollow sleeve 19 and the housing 13. The
 connection 23 may also be accomplished using a glue joint or a molding
 process. The hollow sleeve 19 has a termination 24 on the distal end 21 at
 or near the most distal vibratory node 25 of the elongate ultrasonic probe
 16. In the preferred embodiment the termination 24 has a reduced inside
 diameter that is generally and substantially the same as the outside
 diameter of the elongate ultrasonic probe 16 thereabout, forming generally
 a barrier to the passage of material into the clearance 26. The preferred
 methods of creating the reduced inside diameter at the termination 24 are
 tapering or swaging a metallic or polymeric tube.
 The S-curves 27 shown in FIG. 1 indicate a break-in-length and are used to
 scale the figure so that it fits on the page. They are not part of the
 invention.
 An alternative embodiment of a protective sheath 10 for an ultrasonic
 fragmenting device 11 is shown in FIG. 2. In general the ultrasonic
 fragmenting device 11 includes a handpiece 12 to be held and manipulated
 by a surgeon, the handpiece 12 with a housing 13 and an ultrasonic motor
 14 mounted therewithin. The preferred material for the ultrasonic motor is
 a piezoelectric ceramic such as PZT. The preferred method of mounting the
 ultrasonic motor 14 within the housing 13 is to suspend the ultrasonic
 motor 14 on O-rings 28. An ultrasonic horn 15 is connected to the
 ultrasonic motor 14. The preferred materials for the ultrasonic horn are
 aluminum alloy 7075 or titanium alloy Ti6Al4V. An elongate ultrasonic
 probe 16 is attached to the ultrasonic horn 15, the elongate ultrasonic
 probe 16 has an outer surface 17 about and along its length and vibratory
 nodes 18 spaced along its length as a function of the resonant wavelength.
 The preferred material for the elongate ultrasonic probe is titanium alloy
 Ti6Al4V. Other metals such as aluminum and stainless steel may also be
 used. Vibratory nodes 18 are depicted in FIG. 1 by lines circumscribing
 the elongate ultrasonic probe 16.
 The protective sheath 10 has a hollow sleeve 19 with a proximal end 20 and
 a distal end 21 that surrounds the elongate ultrasonic probe 16 and
 extends therealong. The preferred material for the hollow sleeve is
 thin-walled stainless steel tubing. Plastic or polymeric materials may
 also be used. The hollow sleeve 19 has an inner surface 22 formed, shaped,
 and sized to prevent contact with an outer surface 17 of the elongate
 ultrasonic probe 16 so that there is generally a clearance 26
 therebetween. The hollow sleeve 19 has a connection 23 on the proximal end
 20 to connect to the housing 13. The preferred connection 23 is a snap-fit
 or a twist-lock between the hollow sleeve 19 and the housing 13. The
 connection 23 may also be accomplished using a glue joint or a molding
 process. The hollow sleeve 19 has a termination 24 on the distal end 21 at
 or near the most distal vibratory node 25 of the elongate ultrasonic probe
 16. In the alternative embodiment the elongate ultrasonic probe 16 has a
 flange 29 that circumscribes the elongate ultrasonic probe 16 at or near
 the most distal vibratory node 25. The outside diameter of the flange 29
 is generally and substantially the same as the inside diameter of the
 hollow sleeve 19 thereabout, thus forming generally a barrier to the
 passage of material into the clearance 26.
 The S-curves 27 in FIG. 2 indicate a break-in-length and are used to scale
 the figure so that it fits on the page. They are not part of the
 invention.