U.S. patent number 3,826,263 [Application Number 05/278,684] was granted by the patent office on 1974-07-30 for electrically heated surgical cutting instrument.
This patent grant is currently assigned to Robert F. Shaw. Invention is credited to John M. Cage, Robert F. Shaw, Paul E. Stoft.
United States Patent |
3,826,263 |
Cage , et al. |
July 30, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
ELECTRICALLY HEATED SURGICAL CUTTING INSTRUMENT
Abstract
A surgical cutting instrument includes an electrically heated
cutting edge and an automatic control system for maintaining the
cutting edge at a constant high temperature for sterilizing the
blade, cutting tissue, and cauterizing the incised tissue to reduce
hemorrhage from the cut surfaces of the tissues (hemostasis).
Inventors: |
Cage; John M. (Los Altos,
CA), Shaw; Robert F. (San Francisco, CA), Stoft; Paul
E. (Menlo Park, CA) |
Assignee: |
Shaw; Robert F. (Palo Alto,
CA)
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Family
ID: |
26743628 |
Appl.
No.: |
05/278,684 |
Filed: |
August 7, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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63645 |
Aug 13, 1970 |
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Current U.S.
Class: |
606/31; 219/233;
219/241 |
Current CPC
Class: |
G05D
23/2401 (20130101); A61B 18/082 (20130101); A61B
2018/00107 (20130101); A61B 2018/00005 (20130101); A61B
2018/00666 (20130101); A61B 2090/0813 (20160201) |
Current International
Class: |
A61B
18/08 (20060101); A61B 18/04 (20060101); G05D
23/20 (20060101); G05D 23/24 (20060101); A61B
18/00 (20060101); A61B 18/14 (20060101); A61B
19/00 (20060101); A61b 017/38 (); A61n
003/00 () |
Field of
Search: |
;30/140 ;219/499
;128/33R,303.1,303.13-303.19,404 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pinkham; Richard C.
Assistant Examiner: Apley; Richard J.
Attorney, Agent or Firm: Smith; A. C.
Parent Case Text
This is a divisional application of pending application Ser. No.
63,645, filed Aug. 13, 1970.
Claims
We claim:
1. A surgical instrument for cutting tissue with simultaneous
hemostasis, the instrument comprising:
a blade-shaped support wafer of electrically insulating material
having disposed thereon an electrically heatable element of
electrically conductive material having a resistance which varies
as a function of the temperature thereof, the element including a
plurality of sections which form segments or portions of a
tissue-cutting edge of said support wafer, each of said sections
conducting electrical current along said edge for directly heating
the edge; and
connection means providing electrical connections to each of said
sections for independently supplying electrical power thereto for
maintaining the resistance of each of said sections at a
substantially constant selected value.
2. A surgical instrument as in claim 1 comprising:
means for each of said sections operatively coupled thereto for
sensing the electrical resistance of the corresponding section;
circuit means for each of said sections having an input for
receiving electrical current from a source and being responsive to
the electrical resistance of the corresponding section of said
element for altering the electrical power supplied through said
connection means to the corresponding section from the signal
received at said input to maintain the temperature of the
corresponding section substantially at a preselected value
independent of the temperature of another section of said
element.
3. A surgical instrument as in claim 2 wherein each of said circuit
means comprises a plurality of circuit elements and said
corresponding section connected in a bridge circuit having first
and second pairs of bridge terminals, and including control means
coupling said input to the first pair of bridge terminals, and
bridge-balance sensing means connected to the second pair of bridge
terminals and to said control means for altering the electrical
power applied through the bridge circuit to said corresponding
section for maintaining the resistance thereof substantially at a
preselected value.
Description
BACKGROUND OF THE INVENTION
The control of bleeding during surgery accounts for a major portion
of the total time involved in an operation. The bleeding that
occurs when tissue is incised obscures the surgeon's vision,
reduces his precision and often dictates slow and elaborate
procedures in surgical operations. Each bleeding vessel must be
grasped in pincer-like clamps to stop the flow of blood and the
tissue and vessel within each clamp must then be tied with pieces
of fine thread. These ligated masses of tissue die and decompose
and thus tend to retard healing and promote infection.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a surgical cutting
instrument having a cutting edge which is electrically heated to a
constant high temperature for sterilizing the blade, cutting the
tissue and cauterizing the surfaces of the incision, thereby
allowing surgery to be more rapidly performed. This is accomplished
in accordance with the illustrated embodiment of this invention by
providing an electrically heated element disposed as the cutting
edges of the blade and by providing a control system which
maintains the cutting edge at a high substantially constant
temperature during its use. The hot cutting edge according to the
present invention decreases the amount of tissue that is damaged
and reduces the tendency of the instrument to stick to the heated
tissue in the incision. The material used in the electrically
heated cutting edge has a negative temperature coefficient of
resistance to insure that electrical power applied to the cutting
edge is dissipated primarily in the regions thereof which tend to
be cooled by contact with tissue. The temperature at which the
cutting edge of the blade is maintained depends upon such factors
as the nature of the tissue to be cut, the speed of cutting
desired, the degree of tissue coagulation desired, and the
non-adherence of the blade to the incised tissue and generally is
maintained between 300.degree.-1,000.degree. C. for typical
incisions. The instantaneous temperature of the cutting edge is
monitored by measuring the resistance of the heating element itself
or through the use of thermocouple elements disposed in the blade
near the cutting edge, and the monitoring signal thus derived
controls the power applied to the heating element. The handle of
the cutting instrument is thermally insulated from the blade to
permit comfortable use of the instrument and the handle and blade
with its electrically heated cutting edge are detachable for easy
replacement and interchangeability with blade, scoops and cutting
edges of various shapes and sizes determined by the nature of the
incision to be made and the tissue to be cut.
DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic diagram showing the cutting instrument and
the temperature control system therefor, according to the preferred
embodiment of the present invention, and FIGS. 2 and 3 are
pictorial views of other embodiments of cutting instruments
according to the present invention for use with circuitry as shown
in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1 of the drawing, there is shown the surgical
cutting instrument 9 connected to a temperature-measuring and
power-controlling system 11. The cutting instrument 9 includes a
thin ceramic card 12 in the desired shape of a surgical cutting
blade which is detachable from the handle or holder 10. An
electrically heated element 13 is disposed along the leading edge
of the card 12 to form its cutting edge and is electrically
connected to the control circuit through the cable 14 and the
connectors 16. The element 13 may be a single filament attached to
the edge of the card 12, for example, using conventional ceramic
welding materials or may be a layer of electrically conductive
material vapor-deposited along the edge of the card 12. Also, the
heating element 13 may have sufficient cross-sectional area to be
self-supporting, as shown in FIG. 2, so that the blade 18 is formed
entirely by the element 13 alone. The material used in the element
13 ideally should have a negative temperature coefficient of
resistance so that as selected portions of the element cool when in
contact with tissue, the resistance of such portions will increase
and thereby localize the portions of the element 13 in which
additional power supplied by the control system will be dissipated.
The temperature of the element may thus be maintained substantially
constant over the entire length thereof as portions of the element
13 contact tissue. Suitable materials having negative temperature
coefficients of resistance include silicon carbide, carbon, boron
silicate and such semiconductor materials as silicon and germanium.
Of course, material having a positive coefficient of resistance may
also be used. However, when materials of this type are used, care
should be taken to shape the element 13 so that substantially the
entire length of the element 13 contacts tissue in use. This is
required to prevent the additional power supplied by the control
system 11 from being dissipated in the portions of the element
which do not cool when in contact with tissue and, hence, which
have higher resistance than the cooler portions. For cutting
applications where it is not convenient to shape the element 13 so
that its entire length is in contact with tissue each time it is
used, the element 13 may consist of a plurality of electrically
isolated elements 13 and 13', as shown in FIG. 3, with each of the
elements 13 and 13' connected to a separate temperature measuring
and power-controlling system of the type shown in FIG. 1.
The resistance of the element 13 is included in a bridge circuit 15
which is connected to receive alternating signal appearing on lines
17 and 19. The level of alternating signal appearing on lines 17
and 19 and, hence, the power applied to element 13 is determined by
the conduction angles of the controlled rectifiers 21 and 23 which
are connected in conduction opposition in parallel across the
series resistor 25. Power is supplied to the control system 11
through the primary and secondary windings 26 and 27 of power input
transformer 29. Alternating line signal 28 applied to the
transformer 29 is stepped down typically to about 24 volts for the
safety of the patient and the surgeon and the average current flow
per half cycle of the alternating signal is determined in part by
the series resistor 25 and by the conduction angle of a
silicon-controlled rectifier 21, 23.
The operating temperature of the element 13 may be determined by
adjusting one of the resistors, say resistor 31, in the bridge
circuit 15. Any variation in the operating temperature of element
13 from a set value unbalances the bridge 15 and produces a control
signal 33 across the diagonal terminals 35, 37 of the bridge
circuit 15 which is either in phase or out of phase with the
applied line signal, depending upon whether the operating
temperature of the element is above or below the set value of
operating temperature. A phase-shifting network 39 is connected to
the output terminals of the bridge circuit 15 for applying the
error signal 44 with respect to ground to the input of error
amplifier 41 with a small amount of phase shift relative to the
applied line signal 28. This provides control of the conduction
angle of the controlled rectifiers 21, 23 over a greater portion of
a half cycle of the applied line signal. The output of amplifier 41
is applied to the threshold detectors 43, 45 which respond to the
amplified error signal attaining selected values slightly above and
below zero. The threshold detectors 47 and 49 thus activate the
trigger pulse generators 47 and 49 at the proper times in alternate
half cycles of applied line signal 28 to apply
conduction-initiating pulses to the gate electrodes 51, 53 of the
controlled rectifiers 21, 23. Thus, increased conduction angle of
the controlled rectifiers 21 and 23 increases the power applied to
the element 13 to maintain the element at a preselected operating
temperature as the element tends to cool down in contact with skin
tissue. However, if the operating temperature of the element 13
should exceed the set value due, for example, to thermal overshoot
upon removal of the element 13 from contact with skin tissue, the
phase of the error signal 33 with respect to the applied line
signal reverses. This causes the trigger pulse generators to supply
conduction-initiating pulses to the gate electrodes of the
controlled rectifiers 21, 23 during alternate half cycles when
these rectifiers are back biased. This causes a decrease in the
power delivered to the element 13 with a concomitant drop in its
operating temperature to about the set value of operating
temperature. When this occurs, the proper phase relationship
between error signal and line signal is restored and power is again
supplied to the element 13. Conversion of the control system 11 for
operation with elements 13 having negative or positive temperature
coefficients of resistance merely requires that the trigger pulses
from the generators 47 and 49 be applied through reversing switch
55 to the proper controlled rectifier 21, 23 during the
forward-biasing half cycle of line signal 28.
It should be apparent that other temperature control systems may
also be used to maintain the operating temperature of the element
13 substantially constant at a preselected value. For example, a
thermocouple sensor may be disposed on the card 12 in close
proximity with the element 13 or a thermocouple element may even be
formed on element 13 using another material or dissimilar work
function to form the thermocouple junction. The signal from such
thermocouple may then be used to control the operating temperature
of the element 13 by controlling the power supplied thereto.
* * * * *