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Claims  |
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We claim:
1. A surgical ultrasonic resonant vibrator dimensioned for mounting in a
handpiece, the resonant vibrator providing a vibratory stroke at an
ultrasonic frequency at one end thereof for effectively fragmenting
various contacted tissues, for example at least 5 mils at about 25 kHz,
the resonant vibrator comprising:
an ultrasonic vibration transducer for providing the ultrasonic vibration
from electrical excitation in the handpiece;
a tool extending along the longitudinal axis of the resonant vibrator to an
end thereof which vibrates with the stroke for effectively fragmenting
various contacted tissues; and
connecting means for connecting and vibrating the tool with the transducer,
the connecting means having mounting means for mounting the resonant
vibrator in the handpiece and a node of the resonant vibrations
intermediate its ends, and an elongated slot extending at least halfway
into the connecting means from the exterior of one side thereof and on the
side of the mounting means remote from the transducer, the slot having a
length along the longitudinal axis of the resonant vibrator sufficient to
provide an aspiration path out of the slot from the longitudinal axis at
the end of the slot remote from the transducer with a radius of curvature
sufficiently large to reduce clogging of the aspiration path with
fragmented tissue and coagulated blood, the tool and connecting means
further comprising aspiration conduit means extending along the
longitudinal axis from the tissue-contacting end of the tool to the slot
for aspirating fragmented tissue and blood along the aspiration conduit
means and path.
2. A surgical ultrasonic resonant vibrator as set forth in claim 1, and
further comprising coupling means having a male threaded portion on the
tool and an internally threaded axial opening extending to the slot in the
connecting means for connecting the tool to the connecting member.
3. A surgical ultrasonic resonant vibrator as set forth in claim 2 wherein
the transducer vibrates with a stroke substantially less than that
required for effectively fragmenting various tissue, and wherein the tool
has a smaller effective diameter than the connecting means, and is formed
of a material having a lower acoustic impedance than the connecting means
for substantially amplifying the vibration at the tissue contacting end of
the tool at the connection between the connecting means and the tool.
4. A surgical ultrasonic resonant vibrator as set forth in claim 1 wherein
the aspiration path comprises a tube connected to the aspiration conduit
means in the slot and extending out of the slot with the radius of
curvature which is sufficiently large to reduce clogging of the tube.
5. A surgical ultrasonic resonant vibrator for mounting in a handpiece, the
resonant vibrator providing a vibratory stroke at an ultrasonic frequency
at one end thereof for effectively fragmenting various contacted tissues,
for example at least 5 mils at about 25 kHz, the resonant vibrator
comprising:
an ultrasonic vibration transducer for providing the ultrasonic vibration
from electrical excitation in the handpiece at a stroke substantially less
than that required for effectively fragmenting various tissues;
a connecting member connected at one end to the ultrasonic vibration
transducer and having mounting means for mounting the resonant vibrator in
the handpiece and a node of the resonant vibrations intermediate its ends;
a tool having a length which is a significant portion of the wavelength of
the ultrasonic vibrations in the tool and an aspiration conduit for
connection to a vacuum source extending from one end of the tool which
contacts the tissue, fragments it with the ultrasonic vibrations, and
aspirates the fragmented tissue and blood through the aspiration conduit;
and
releasable coupling means on the other ends of the connecting member and
the tool for releasably connecting the connecting member and tool together
to transmit the ultrasonic vibration from the transducer to the one tool
end, the tool having a lesser effective diameter than the connecting
member and being formed of a material having a lower acoustic impedance
than the connecting member for substantially amplifying the stroke of the
ultrasonic vibration transmitted to the tool from the transducer through
the connecting member at the coupling means.
6. A surgical ultrasonic resonant vibrator as set forth in claim 5 wherein
the releasable coupling means comprise a male threaded end portion on the
tool and an internally threaded opening into the connecting member on the
longitudinal axis of the resonant vibrator.
7. A surgical ultrasonic resonant vibrator as set forth in claim 6 wherein
the aspiration conduit extends along the longitudinal axis of the resonant
vibrator to the male threaded end portion of the tool and further
comprises a nipple projecting from the male tool end portion, and wherein
the connecting member further comprises a slot extending through the
connecting member transverse to the longitudinal axis of the resonant
vibrator on the side of the mounting means remote from the transducer, the
slot having a length along the longitudinal axis sufficient to allow an
aspiration tube to be connected to the nipple and extend from the slot
with a radius of curvature sufficiently large to reduce clogging of the
aspiration tube with fragmented tissue and blood.
8. A surgical ultrasonic resonant vibrator dimensioned for mounting in a
handpiece, the resonant vibrator providing a vibratory stroke at an
ultrasonic frequency at one end thereof for effectively fragmenting
various contacted tissues, for example at least 5 mils at about 25 kHz,
the resonant vibrator comprising:
an ultrasonic vibration transducer for providing the ultrasonic vibration
from electrical excitation in the handpiece with a stroke of substantially
less than that for effectively fragmenting various tissues;
a connecting member connected at one end to the transducer and having
mounting means for mounting the resonant vibrator in the handpiece and a
node of the resonant vibrations intermediate its ends, a slot extending at
least halfway into the connecting member from one side thereof and on the
side of the mounting means remote from the transducer, the slot having a
length along the longitudinal axis of the resonant vibrator sufficient to
allow an aspiration tube to extend out of the slot from the longitudinal
axis at the end of the slot remote from the transducer with a radius of
curvature sufficiently large to reduce clogging of the aspiration tube
with fragmented tissue and coagulated blood, and an internally threaded
opening through the other end of the connecting member on the longitudinal
axis extending to the slot; and
a tool having a male threaded portion at one end for threaded coupling to
the threaded opening in the connecting member, the tool projecting
therefrom a significant length in relation to the wavelength of the
resonant vibrations along the longitudinal axis with a tapering outside
contour, the tool having a lesser effective diameter and being formed of a
material having a lower acoustic impedance than the connecting member for
substantially increasing the stroke of the ultrasonic vibration
transmitted to the tool from the transducer through the connecting member
at the threaded coupling and, in combination with the tool taper, to a
stroke for effectively fragmenting various tissues contacted therewith,
the tool further having an aspiration conduit extending between the ends
of the tool along the longitudinal axis for connection at the slot to an
aspiration tube in the slot to aspirate the fragmented tissue and blood
through the tool.
9. A surgical ultrasonic resonant vibrator dimensioned for mounting in a
handpiece, the resonant vibrator providing a vibratory stroke at an
ultrasonic frequency at one end thereof for effectively fragmenting
various contacted tissues, for example at least 5 mils at about 25 kHz the
resonant vibrator comprising:
an ultrasonic vibration transducer for providing the ultrasonic vibration
from electrical excitation in the handpiece with a stroke of substantially
less than that for effectively fragmenting various tissues;
a connecting member connected at one end to the transducer and having
mounting means for mounting the resonant vibrator in the handpiece and a
node of the resonant vibrations intermediate its ends, a slot extending at
least halfway into the connecting member from one side thereof and on the
side of the mounting means remote from the transducer, and an opening
through the other end of the connecting member on the longitudinal axis
extending to the slot;
a tool having an end portion projecting into the opening in the connecting
member and projecting from the connecting member a significant length in
relation to the wavelength of the resonant vibrator along the longitudinal
axis thereof, the tool having a lesser effective diameter and being formed
of a material having a lower acoustic impedance than the connecting member
for substantially increasing the stroke of the ultrasonic vibration
transmitted to the tool from the transducer through the connecting body,
the tool further comprising an aspiration conduit extending along the
longitudinal axis from a tissue contacting end of the tool to the end
portion projecting into the connecting member and communicating thereby
with the slot in the connecting member;
releasable coupling means for holding the tool to the connecting member;
and
a casing sealed about the connecting member at the slot and having means
for connecting an aspirator whereby tissue fragmented by the tool can be
aspirated through the aspiration conduit and slot to the aspirator. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
This invention is directed to an apparatus for ultrasonically
disintegrating and aspirating tissue in a surgical operation. More
particularly, this invention relates to an improved and novel surgical
apparatus for disintegrating and aspirating a wide range of body tissues.
Use of ultrasonically vibrated surgical tools to remove various types of
body tissues is well known in the art. Certain of these instruments are
being commonly used in various surgical procedures such as in the removal
of cataracts from the eye as illustrated by U.S. Pat. No. 3,589,363 issued
June 29, 1971 to A. Banko and C. D. Kelman. Other specialized
ultrasonically driven surgical instruments have been patented, though the
extent of actual use and practice is unknown. However, except for the
ultrasonically driven dental prophylaxis unit (which is a widely accepted
and successful instrument for cleaning the teeth professionally) and the
use of ultrasonic instruments to surgically remove cataracts, the use of
ultrasonically vibrated tools in the surgical removal of body tissues is
not a common and accepted procedure at present.
Several patents and patent applications are known which describe the use of
such ultrasonically vibrated tools to remove tissues among which are U.S.
patent application Ser. No. 555,474 filed Mar. 5, 1975 and assigned to the
assignee of the present application, U.S. Pat. No. 3,526,219 issued Sept.
1, 1970 to L. Balamuth, and U.S. Pat. No. 3,565,062 issued Feb. 23, 1971
to A. Kuris. While the aforementioned patents describe various types of
instrumentation for removing tissue, bodily tissues exhibit a wide range
of mechanical characteristics; i.e., compliance, ranging from liquid to a
relatively hard and brittle material such as bone. It is therefore
unrealistic to assume that a single type of instrument can satisfactorily
be used on all of the different types of tissue. We have found that while
the apparatus and method described in the referenced U.S. patent
application is satisfactory for certain low-elasticity neurological
tumorous tissue it is not satisfactory when employed on more elastic
compliant tissue. Similarly it has been found that the instrumentation
utilized in performing the cataract removal in accordance with the
aforementioned U.S. Pat. No. 3,589,363 is quite unsuitable for removing
neurological tumors and similar tissue. In regard to the instrumentation
described in U.S. Pat. No. 3,526,219, it is difficult to ascertain the
effectiveness of such instrumentation due to the broad nature of the
teaching.
SUMMARY OF THE INVENTION
We have invented a novel surgical apparatus for disintegrating and
aspirating tissue. The apparatus comprises in combination a handpiece
having a resonant vibrator, generator means for electrically exciting the
resonant vibrator in the ultrasonic frequency range, and means responsive
to the vibrator for controlling the frequency of the generator means
output. More particularly the resonant vibrator comprises an elongated
hollow tool at its anterior end, a connecting member fixedly attached to
the posterior end of the tool, and an electromechanical transducer
attached to the other end of the connecting member and excited by the
generator means, whereby ultrasonic vibrations are exhibited by the
anterior end of the tool along its longitudinal axis having a peak
amplitude (stroke) of at least 0.005 inches (5 mils). The tool preferably
comprises a cylindrical and a conical section. The electromechanical
transducer is preferably a magnetostrictive stack.
The generator means for electrically exciting the magnetostrictive stack
comprises a generator having an output in the ultrasonic frequency range
and means responsive to the level of stroke and resonant frequency of the
transducer for automatically controlling the output frequency and power of
the generator to substantially coincide with resonant frequency of the
resonant vibrator, and maintain a desired stroke level.
An object of this invention is to provide a novel surgical apparatus
employing an ultrasonically vibrating tool, having aspiration.
Another object of the present invention is to provide an ultrasonically
vibrating tool having aspiration means which are isolated from the
connecting member's mounting fixtures.
Still another object of the present invention is to provide an
ultrasonically vibrating surgical tool wherein coolant fluid is separated
and sealed off from the aspiration and irrigation means.
Yet another object of the present invention is to provide ultrasonic
surgical apparatus for fragmenting, and aspirating highly compliant tissue
containing blood.
It is yet another object of this invention to provide apparatus, having an
ultrasonically vibrating surgical tool, which apparatus is automatically
responsive to the resonant frequency and the desired vibratory stroke of
the tool.
It is therefore also an object of this invention to provide apparatus for
surgically removing tissue.
It is another object of this invention to provide apparatus for surgically
disintegrating and aspirating tissue in an effective manner.
It is still another object of the present invention to provide surgical
apparatus having an ultrasonically vibrating tool with a stroke of at
least 5 mils (0.005 inch).
Yet another object of this invention is to provide ultrasonically vibrating
surgical apparatus having automatic control of frequency and power in
response to output of the vibrating surgical tool.
Still another object of this invention is to provide a high stroke
ultrasonically vibrating surgical handpiece.
Another object of the present invention is to provide a conveniently held
high power ultrasonic surgical tool having aspiration and irrigation.
Other objects and advantages of the present invention will be apparent to
those skilled in the art from the description of the drawings and
preferred embodiment which follows.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 of the drawings is a sectional elevation of one version of the
surgical handpiece according to this invention;
FIG. 2 is a sectional elevation of another version of the surgical
handpiece;
FIG. 3 is an elevation of the resonant vibrator employed in the handpiece;
and
FIG. 4 is a block diagram of the generator and handpiece combination
according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
We have invented an improved apparatus for ultrasonically fragmenting and
aspirating body tissue. The apparatus is embodied in a conveniently held
handpiece 12, a cross-sectional view of which is shown in FIG. 1 of
drawings, enclosing means for exciting a resonant member to vibrate in the
ultrasonic range, including an aspirating tool vibrating at its tip in the
ultrasonic frequency range at a longitudinal amplitude in excess of about
5 mils (0.005 inch).
To achieve such an effect in an instrument which can be conveniently held
by a surgeon, a number of difficult obstacles must be overcome. One major
obstacle is in transmitting excitation to an operating tool tip while at
the same time such tip acts as the aspirating inlet to effect the surgical
removal of the undesired tissue.
We have discovered that in order to surgically remove a broad enough range
of compliant tissue that the surgeon is apt to encounter, an instrument
which vibrates longitudinally in the range of at least 5 mils at about 25
KHz is necessary. At the same time as the tip is ultrasonically vibrating
it is desirable to also apply aspiration to the affected tissue. A number
of prior art issued patents such as previously mentioned do teach the
application of aspiration together with an ultrasonic vibrating tool tip
to remove body tissue. However, it has been found that except in specific
instances where the particular tissue is readily susceptible to ultrasonic
disintegration such as cataracts, it has been difficult to provide an
ultrasonically vibrated tool to effectively remove tissue exhibiting a
wide range of mechanical properties (i.e., compliance) which the surgeon
may encounter in an operation. Thus, if the ultrasonic instrument was not
adaptable to the range of tissue ordinarily encountered during specific
types of operations, the instrument may have to be discarded for
particular operations and is therefore an inconvenience during the
operation. It is clearly recognized that to be acceptable to the surgeon,
an instrument must be sufficiently rapid and selectively effective against
the various types of tissue the surgeon is desirous of removing.
In particular, where highly compliant tissue mixed with blood is aspirated,
there is the increased likelihood of occlusion of the aspiration conduit
due to the coagulation of the blood. It is therefore desirable to provide
as direct an aspiration path as possible. This is to avoid clogging or
occlusion of the aspiration path due to the increasing coagulation of the
blood tissue mixture being aspirated. In addition, vibration apparently
acts to increase the rate of coagulation. It is therefore additionally
desirable the aspiration path or conduit should preferably have minimal
changes of direction of flow and where such changes are required, they
should be as gentle as possible. Further pockets of low flow velocity are
also to be avoided.
Referring to FIG. 1 of the drawings, the surgical instrument 12 is shown in
sectional elevation and comprises a tubular handpiece 14 and an elongated
resonant vibrator 16 inserted therein and projecting out of the front part
of the handpiece. As the instrument is held and manipulated by the surgeon
in one of his hands, the size and weight of the handpiece is limited by
the ability of the hand to delicately grasp and manipulate the instrument.
For this purpose, the outside diameter of the handpiece should not exceed
about 1.5 inches (3.7 cm) in overall diameter and a diameter of about 1
inch (2.5 cm) is preferred.
Referring now to the construction of the resonant vibrator 16, the vibrator
is basically a mechanical vibrating system mounted in the handpiece. The
vibrating system is divided into a transducer; i.e., a magnetostrictive
stack composed of nickel alloy sandwich such as is taught in U.S. Pat. No.
RE 25,033 and is well known in the art. Electrical oscillating current
supplied to the winding of the coil induces mechanical oscillations in the
stack, such oscillations being at the resonant frequency and having a
maximum practical peak-to-peak stroke (amplitude) of about 1 thousandth of
an inch (1 mil) at a frequency of about 25 KHz. As a practical matter due
to limitations imposed by the state of the art, as frequency increases in
the ultrasonic range, the stroke that one is able to obtain in the
transducer is reduced.
However, it is well known in the art that if one desires to take the
available stroke from the transducer and vary the stroke, an ultrasonic
mechanical transformer may be used. The design of such a transformer which
is fixedly attached to the transducer magnetostrictive stroke is taught,
for instance, in the aforementioned U.S. Pat. No. RE 25,033.
Finally, the design of the transformer section must include and yield the
preferred characteristics at the output portion of resonant vibrator. In
this regard the output portion of the vibrator must vibrate ultrasonically
with a desired stroke (peak to peak) of at least 0.005 inch (5 mils) while
simultaneously functioning as an aspirator inlet. The output portion must
also, for surgical requirements, be rather long and slender, while for
aspiration purposes it is preferred to have as large a cross-sectional
flow area as possible to thereby minimize the possibility of occluding the
aspiration conduit.
Prior art hand-held commercial instruments, either providing irrigation or
aspiration through the ultrasonic output end, have generally had strokes
of less than 0.003 inch. Even this level of stroke is difficult to achieve
at 25 KHz in a production instrument. The resonant vibrator output
according to the present invention is (commercially) capable of producing
a stroke in the range of at least 5 mils and preferably from 5 to 16 mils
at about 25,000 cps.
An acceptable ultrasonically vibrated surgical handpiece capable of such an
output; i.e., a stroke of at least 5 mils at 25 KHz, has not been
achieved, whereas we have invented such as described herein.
FIG. 3 of the drawings illustrates a preferred version of the resonant
vibrator 16 having the magnetostrictive stack 18 at one end, a tool 20 at
the forward end, and a connecting member 22 intermediate the tool 20 and
the stack 18. For purposes of description, the tool encompasses that
portion of the vibrator having an aspiration conduit 24 axially located
therethrough. The tool is also coincidentally a substantially unitary
body, designed for replacement as required and attached to the connecting
member by a male threaded insert 26 at its posterior end. The preferred
tool comprises an elongated hollow tube 28 at its anterior end, being
about 0.09 inch at its tip 30 with a uniform outside diameter for about
0.65 inch and then tapering uniformly to an outside diameter of about 0.14
inch over a length of about 2 inches to fillet 32, where it is machined
into a hexagonal neck 34 of about 0.19 inch. The neck 34 is connected to a
circular rim 36 of about 0.3 inch diameter and 0.05 inch thickness. From
the rim 36, the previously described male threaded insert 26 which is
about 1/4 inch long with an O.D. of about 0.21 inch, extends rearwardly
and is chamfered at its end. The threaded insert 26 is necessarily a
relatively large sized thread, being preferably a No. 12 screw thread, in
order to withstand the extreme stresses present. Axially extending from
the rearward end of the insert 26 is a nipple 40 having a necked-in outer
surface for receiving and retaining an aspiration tube 42. The hollow
aspiration conduit 24 extends the whole length of the tool and has a
uniform internal diameter (I.D.) of preferably about 0.06 inch. Preferably
the tool is made of a biologically compatible metal having a low
characteristic acoustic impedance such as titanium or an alloy thereof.
The above-described tool 20, while susceptible to various modifications,
necessarily must have an elongated tubular end having as small an outside
diameter as is practical. Furthermore, since the tool tip 30 is to vibrate
ultrasonically with a stroke in excess of 0.005 inch (5 mils), the tubular
portion of the tool is tapered over most of its length to preferably
reduce the stress to which the metal is subjected. Finally, and
importantly, the tool in terms of its length and its distributed mass is
dynamically a part of the resonant vibrator 16 which can magnify the 0.001
inch (1 mil) stroke input induced in the magnetostrictive stack 18 to in
excess of a 5 mil output at the tool tip.
The connecting member 22 according to the present invention is a unitary
metal structure also dynamically a part of a resonant vibrator which
serves to connect the stack 18 to the tool 20 and, more importantly, to
serve to transmit and modify the stroke as it is dynamically transmitted
from the stack to the tool. Ideally the connecting member should be as
wide as possible in contrast to the tool tip, as such a relative diameter
increases the magnification, M, of the output stroke as much as possible
at the tool tip in conformity with the following equation.
##EQU1##
where K.sub.1 and K.sub.2 are constants dependent on the lengths of the
various elements and their material properties and D.sub.1, D.sub.2, and
D.sub.3 are the effective cross-sectional characters of the connecting
member and tool as shown in FIG. 3 of the drawings. It is therefore
readily apparent that the greater the diameter D.sub.1 is in relation to
diameters D.sub.2 and D.sub.3, the greater is the magnification M that is
obtained. The mode of motion of the resonant vibrator is located in the
vicinity of flange 54, with the diameter D.sub.1 of the connecting member
being on the input side of the mode and the diameters D.sub.2 and D.sub.3
being on the output side. But, as the portion 46 of the connecting member,
which is defined by D.sub.2 as the effective diameter, comprises the
aspiration path communicating with the hollow tool, it is desirable to
maintain the stroke level in this area as small as possible. If such
connections are made, then the ratio of diameter D.sub.1 to diameter
D.sub.2 should be as small as possible. Such a requirement modifies the
above equation where if D.sub.2 is made much larger D.sub.1, M becomes
equal to
##EQU2##
Thus the dynamic constraints appear to dictate a large diameter connecting
member in order to achieve high magnification of output stroke. Since the
handpiece 14 in which the vibrator and its connecting member are mounted
has a practical limit to its size, it being necessary for the surgeon to
conveniently hold it in one hand and manipulate it accurately, it has been
previously found difficult to achieve high magnification in such small
instrumentation.
To achieve such magnification, the connecting member 22 is made of a metal
having a high characteristic acoustic impedance or an alloy such as monel
shaped as shown and described herein. The anterior portion 46 of the
connecting member 22 has a cross-section of about 0.38 inch square and a
length of about 1.2 inches where it flares out to a circular rim 48 with a
diameter of about 0.46 inch. The rim 48 forms the forward edge of an
annular cutout 50 of about 0.435 inch diameter, which cutout 50 acts to
retain for a first O-ring 52. The circular flange 54 serves as the
rearward boundary of the cutout and functions to position the vibrator 16
in the handpiece 14 as will be hereafter described.
The rearward part of the connecting member is a solid circular rod 56 of
about 0.28 inch in diameter and about 2 inches long, the posterior end of
which is soldered, brazed, welded or otherwise fixed to the forward end of
the magnetostrictive stack 18.
The anterior portion 46 of the connecting body has an axially located
internally threaded bore 60 being sized to receive the full length of the
male threaded insert 26 of the tool. The bore can have a shoulder against
which the chamfered end of the threaded insert 26 stops under a
predetermined torquing force. A large rectilinear slot 64 is located in
the connecting member adjacent the end of the borehole and the tool's
nipple extends into the opening formed by the slot. The aspiration tube
42, shown in FIG. 1, is thereby free to mate with the nipple in the
opening thus formed by the slot without the necessity of a sharp radius
being applied at the joint to either the aspiration tube or the conduit.
Referring again to FIGS. 1 and 2, where the resonant vibrator is shown
mounted in the handpiece, the handpiece has a suitable wound coil (not
shown) for exciting the magnetostrictive stack, and attached to a cable
through which electrical power and signal conductors and cooling fluid are
brought to the handpiece. The tubular part of the handpiece comprising a
housing 80 has an opening through which the connecting member and stack
are inserted. The housing 66 is undercut and externally threaded at its
forward end. A second O-ring 68 is mounted on the rod 56 and is positioned
between the housing's forward end and the flange 54 upon assembly of the
handpiece.
The two O-rings 52 and 68 thus effectively seal the anterior portion of the
connecting member forward of the flange from the internal volume of the
handpiece enclosing the stack and containing the various electrical wiring
and coolant supply lines in the handpiece.
A molded retainer 70 is positioned over the connecting member 22 and has an
internally threaded cap 72 which is attached to the housing forward end.
Internally forward of its cap, the retainer 70 is molded with a stepped
internal diameter to fit over the first O-ring 52 in compressive contact
and over the adjacent flange 54 with some minor clearance. The anterior
portion of this stepped internal diameter is hexagonal in cross-section to
enclose the anterior portion 46 of the connecting member, but with some
minor clearance. Exteriorly the retainer 70 is molded with a dorsally
located opening 74 through its wall adjacent the connecting member's slot.
The opening 74 provides access for surgical grade plastic tubing 42 to
connect to the tool nipple 40. The size of the opening and the slot is
adequate so that the radius of curvature is gentle, thereby offering less
resistance to aspirated blood containing tissue and lessening the
possibility of occlusions occurring.
FIGS. 1 and 2 also illustrate two versions of an irrigation manifold 78,
each version having a similar hollow truncated cone surrounding and spaced
from the tool to provide an annular irrigation channel 82 having an
annular nozzle 80 about 1/8 inch posterior to the tip of the tool. The
flow of sterile irrigation fluid through the channel 82 has an effect on
the tool output acting to dampen the vibration somewhat while importantly
at the same time serving to cool the tool over most of its actual length.
The version of the manifold 78 illustrated in FIG. 1 widens posteriorly to
fit over the retainer 70. The retainer in front of the opening 72 has a
slightly larger outside width and depth, while the manifold's posterior
end is molded with an interior lip 84. The manifold can therefore in
assembly be slid over forward part of the retainer and when in proper
assembled condition is held on the retainer by the lip 84.
The manifold 90 illustrated in FIG. 2 has no lip but rather is tightly
fitted over the retainer. The manifold in the second version has a smaller
opening into which an aspiration pipe 94 is inserted into the manifold's
dorsal side and opens interiorly opposite the connecting member slot. The
tool, though otherwise identical to that shown in FIGS. 1 and 2, is shown
without its nipple. Aspirated material therefore flows from the hollow
tool into the space provided by the slot 64 through an opening 70a in the
retainer cap 72a and into the aspiration pipe 94.
An irrigation inlet pipe 88 is inserted fixedly into the cap's forward part
and opened into the annular channel 82. Sterile surgical tubing (not
shown) is connected to the irrigation as desired from a suitable source. A
seal 86, preferably a silastic washer, is fitted over the anterior part of
the connecting member adjacent a front edge of the retainer and serves to
seal the irrigation fluid space from the space surrounding the connecting
body (and serves as part of the aspiration fluid path in the handpiece
shown in FIG. 2).
Supplying the irrigation fluid through the channel 82 provides three
distinct advantages besides supplying irrigation fluid to the operative
site. The irrigation fluid cools the vibrating tool and the material,
blood, fluid and tissue being aspirated through the tool. If there is no
such provision for cooling the high vibratory stroke output in excess of
0.005 inch of the tool would rapidly heat up from such intense vibration
and weaken or damage the tool. Heat would also add to the rate of
coagulation of blood being aspirated through the tool. Reducing the tool
temperature thus reduces the possibility of occlusions. The irrigation
fluid also wets the aspirated tissue, aiding in aspiration thereby.
Further, it protects tissue not in contact with the tip.
The resonant vibrator according to the present invention has been found to
resonate effectively in a rather narrow frequency band. Further, the
actual frequency at which the vibrator effectively operates fluctuates
during the course of an operation. It is not only inconvenient but also
difficult and inefficient for an individual to continue manual tuning of
the frequency during an operation. Accordingly, a novel and improved
generator is described herein as part of this invention. A generator
powers the handpiece by developing in the wound coil an alternating or
oscillating current in a high frequency feedback loop of sufficient power
oscillating at the required frequency to develop an oscillatory magnetic
field exciting the magnetostrictive stack and converting electrical energy
into mechanical energy. If the electrically powered frequency is not
sufficiently coincident with the resonant frequency band of the resonant
vibrator, energy transfer to the vibrator will be inefficient and the
output of the vibrator will be limited to less than the desired stroke by
its inherent characteristics. To achieve effective energy transfer at a
sufficient vibratory level, the frequency and amplitude are regulated in
interlocking control loops as described herein.
More particularly, attention is now directed to FIG. 4 of the drawings
where the ultrasonic generator and handpiece block diagram is shown. The
handpiece 102 comprises schematically an excitation coil 104,
magnetostrictively exciting a resonant vibrator stack 106 as previously
described (see reference 18 in FIG. 3). Once the vibratory frequency is
established in the high frequency loop, the actual vibration in terms of
the stroke of the vibrator is picked up by a secondary winding pickup 108
in the handpiece 102, and converted into a voltage equivalent of the
stroke output by an envelope detector 110. The signal from the detector
110 is applied to an error integrator 112 mounted in the generator. The
integrator 112 also has a reference input from a potentiometer 114 which
is set by the operator to a desired stroke setting. The integrator 112
develops an output signal related to the difference between the stroke
setting input as the reference signal and the voltage signal developed by
the detector as a result of actual stroke of the vibrator. The output
signal from the integrator 112 is the control signal to a variable limiter
116. The limiter 116 is in a high frequency feedback loop with, and picks
up the output of, a transconductance amplifier 120. The output of the
transconductance amplifier is the power input to the handpiece generating
the voltage at the desired frequency for powering the magnetostrictive
stack. The limiter 116 and a low Q active filter 118 are in the high
frequency feedback loop to the transconductance amplifier, while the
limiter 116 acts as a control for the control level feedback loop.
The limiter 116 takes the voltage output signal of the amplifier and
modifies the limiter output level according to the control signal from the
error integrator; i.e., it controls or limits voltage output in response
to the control signal from the integrator. Also placed in the high
frequency feedback loop between the limiter 116 and the amplifier is the
filter 118 which functions as an active band pass filter. Thus, the filter
118 passes through only the fundamental component of the output from the
limiter and, by doing so, prevents the amplifier (i.e., the generator,)
from operating in spurious modes, and generating undesired frequencies.
The filter further acts to modify, if necessary, the signal to a more
nearly sinusoidal type output. Alternatively the high frequency feedback
loop may be varied to connect the limiter input via conductor 124 to the
pickup 108 output and delete conductor 126. This latter variation allows
automatic frequency control under high mechanical loading of the resonant
vibrator.
The output of the generator, i.e., the transconductance amplifier 120, is
applied through a D.C. biasing circuit 122 which is required in exciting a
magnetostrictive transducer. The D.C. biasing circuit 122 thus acts to
establish the required D.C. current in the excitation coil 104 to excite
the stack as is well known in the art. Thus the generator and handpiece
comprise two feedback loops. One feedback loop, the high frequency loop,
comprises the amplifier, the limiter, and the filter, which is
self-oscillating at a frequency determined by its phase shift including
the impedance of the handpiece. The other feedback loop, the stroke level
feedback loop, comprises the pickup, the detector, and the integrator,
which inputs to the limiter to control the voltage level and thereby the
stroke level of the vibrator. The output level of the amplifier is thus
controlled in response to the level of sensed output. This output is fed
back in a stroke level feedback loop through the integrator where it is
compared to a preset desired level, and the difference from such
comparison acts in the high frequency feedback loop to control the
amplifier output to obtain the desired stroke level. A continued high
stroke output at the tool tip is thus obtained. The frequency of the
amplifier is automatically determined by the phase shift of the various
active elements of the frequency feedback loop including the handpiece
coil. As the resonant vibrator exhibits a narrow resonant frequency band,
and can rapidly alter electric phase, it thereby effects the total
impedance by phase shift as seen at the handpiece coil 104. This impedance
directly effects the phase shift of the amplifier and controls frequency
in the high frequency feedback loop.
Having thus fully described our invention and wishing to cover those
variations and modifications which would be apparent to those skilled in
the art but without departing from either the spirit or scope thereof,
* * * * *
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