INSTRUMENT FOR COMPENSATING FOR HAND TREMOR DURING THE MANIPULATION OF FINE STRUCTURES

INSTRUMENT POUR COMPENSER LE TREMBLEMENT DE LA MAIN LORS DE LA MANIPULATION DE FINES STRUCTURES

English Abstract

The invention relates to an instrument for the
manipulation of fine structures, said instrument
detecting hand tremor and compensating for this hand
tremor by effecting counter-movements of the working tip.
The main area of application will probably lie in the
field of microsurgery, since the operations performed in
said field can be made difficult by the hand tremor of
the operating surgeon. Here, the tremor is detected by
movement sensors, by repeated analysis of the position of
the handheld part (1) of the instrument, or by deriving
electromyographie signals from the forearm of the
operator. Intentional and unintentional movements are
differentiated from one another on the basis of one or
more criteria, such as movement amplitude, speed,
frequency and direction. To compensate for undesired
movements, signals are sent to an arrangement of
actuators (3) which cause deflections of the movable part
(4) of the instrument, which deflections at the tip of
the instrument compensate for the hand tremor. When the
instrument is used as a needle holder in surgery, the
actuators (3) can also be controlled by push button in
such a way that, by oscillations, they facilitate the
penetration of the suture needle into the area being
worked on.

French Abstract

L'invention concerne un instrument destiné à la manipulation de fines structures, sensible au tremblement de la main et le compensant par des mouvements opposés de la pointe de l'outil. Le principal domaine d'application de l'invention est la microchirurgie, du fait que les activités développées dans ce domaine peuvent être aggravées par le tremblement de la main de l'opérateur. La détection du tremblement de la main s'effectue par des détecteurs de mouvement, par analyse répétée de la position de la partie (1) de l'instrument tenue par la main, ou par dérivation de signaux électromyographiques de l'avant-bras de l'opérateur. Des mouvements, intentionnelle ou non, sont différenciés au moyen d'un ou plusieurs critères tels que l'amplitude, la vitesse, la fréquence et la direction du mouvement. Pour compenser des mouvements indésirables, des signaux sont envoyés à un dispositif d'acteurs (3) provoquant, sur la partie mobile (4) de l'instrument, des déviations compensant, à la pointe de l'outil, le tremblement de la main. Lorsque l'instrument est utilisé comme porte-aiguilles en chirurgie, les acteurs (3) peuvent être également commandés par pression sur un bouton, de manière à faciliter, par oscillation, la pénétration des aiguilles à coudre dans l'objet à traiter.

Claims

Instrument for compensating for hand tremor during the
manipulation of fine structures

Claims

1. Instrument for the manual working of fine
structures, consisting of
(a) a handheld section (1),
(b) a section (4) which le movable in relation to
the handheld section (1),
(c) actuators (3),
and where
(d) the actuators (3) are designed to effect
relative movements between the handheld section (1) and
the movable section (4), which relative movements
compensate at least partially for movements of the
handheld section (1).

2. Instrument according to Claim 1, characterized in
that one or more sensors (2) are arranged on the handheld
section (1), said sensors (2) detecting the movement of
the handheld section (1), sad their output signal being
used to trigger the actuators (3).

3. Instrument according to Claim 1 or 2,
characterized is that one or more sensors are arranged on
the movable section (4), said sensors detecting the
movement of the movable section (4), and their output
signal being used to trigger the actuators (3).

4. Instrument according to one of Claims 1 through
3, characterized in that one or more sensors are arranged
on the handheld section (1) or on the movable section (4)
or between the handheld section (1) and the movable
section (4), said sensors detecting the relative movement
between the handheld section (1) and the movable section
(4), and their output signal being used to trigger the
actuators (3).

5. Instrument according to one of Claims 2 through
4, characterized in that at least one sensor detects the
acceleration.

6. Instrument according to one of Claims 1 through




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5, characterized is that one or more sensors are provided
for repetitive or continuous detection of the position of
the handheld section (1) is one, two or three dimensions.

7. Instrument according to one of Claims 1 through
6, characterized in that one or more sensors are provided
for repetitive or continuous detection of the position of
the movable section (4) in one, two or three dimensions.

8. Instrument according to Claim 6 or 7,
characterized is that the position of the instrument is
detected optically via the ray path of an operating
microscope.

9. Instrument according to one of Claims 1 through
8, characterized in that a control or regulating unit
triggers the actuators on the basis of the data from the
sensors for position detection and/or movement detection.

10. Instrument according to one of Claims 1 through
9, characterized in that a control or regulating unit
triggers the actuators on the basis of a repetitive or
continuous position detection.

11. Instrument according to one of Claims 1 through
10, characterized in that electromyographically detected
potentials are used to trigger the actuators.

12. Instrument according to one of Claims 1 through
11, characterized in that when movements of the handheld
section or movable section occur, the compensation
movements take place in a predetermined or adjustable or
automatically adapting frequency range.

13. Instrument according to one of Claims 1 through
12, characterized is that when movements of the handheld
section or movable section occur, the compensation
movements take place in a predetermined or adjustable or
automatically adapting amplitude range.

14. Instrument according to one of Claims 1 through
13, characterized in that the actuators (3) can be
triggered in such a way that a rigid connection is
obtained between the handheld section (1) and the movable
section (4).

15. Instrument according to one of Claims 1 through
14, characterized in that the actuators (3) can be




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triggered is such a way that they can generate
oscillations of the movable section (4).

Description

3, SEP. 1998 15: 39 F~RRESTER & HOEHhaER T NR. 3536 S. 3!21
Iaetruaeat for compeaeating for hand tremor during the
manipulstioa of fine structures
~escripti_o~
Manual work oa fine structures is made much more


S difficult by the contraction of antagonistic muscles


occurring involuntarily, and in largely rhythmic


succession, and referred to ae tremor. This ie noticeable


particularly in microsurgery when suturing fine nerves
or


vessels, prolongs the duration of the operation and


reduces the quality of the result.


However. is order to be able tv perform filigree


work, use is made, for example, of supports for the


hands, or micromarsipulatore, which convert relatively


rough movemento into fine deflections.


The object of the invention is to make available


a handheld instrument for the manual manipulation of
fine


structures, in which undesired movements, for example


tremor, have no effect, or at least less effect, on
the


manipulation.


The invention is based on the concept of


evaluating the undesired movements of handheld


instruments and of deflecting, by means of actuators,
the


working tip of the instrument (in surgical applications


this would be, for example, a needle holder) in order
to


provide compensation, so that the hand tremor cannot
be


observed at the tip.


Since the physiological tremor takes place ~.n a


range of between about 5 and 15 strokes/second, it
can be


differentiated from slower -voluntary movements, for


example by frequency-selective filtering.


Movement detectxoa
According to the invention, one or more devices
can be provided for detecting movements on the part of
the user, in particular for detact~.ag movements of the
instrument sensed by the user, for example active or
passive measurement transducers, by means of which
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undesired movements oa the part of the user, or movements
of the instrument caused by the user, can be detected.
The output signals from these devices ,are used, if
appropriate after suitable evaluation and processing, to
trigger actuators of the instrument for the purpose of
compensating for the undesired movements.
To detect the movement of the instrum~nt, a
number of possibilities can be selected in principle, and
these can be eombiaed with one another:
1.. Acceleration and angular velocity sensors are
arranged on one or more sections of the instrument,
which sensors supply a mechanical or electrical
signal correlated with the movement of the
instrument.
151 The function of the sensors can be based oa purely
mechanical, electromagnetic, capacitive,
piezoelectric yr piezoresistive principles. The
sensors have to detect the movement with suf~iciant
sensitivity and accuracy. In this connection, it ie
conceivable to use sensors which have their maximum
sensitivity is the frequency range in which the
undesired movements take place and thereby deliver
an output signal correlated with the tremor. The
sensors can be arranged in such a way that they can
detect both translationa7, movements and rotational
movements v~ the instrument.
2. According to the invention, one or more devices can
be provided for repetitive or continuous detection
of the position of certain sections of the
instrument in one, two or three dimensions, in
particular of a handheld-aectioa and/or a section of
the instrument which is movable in relation to the
handheld section. By repetitive or continuous
detection o! the position and orientation of certain
sections of the instrument, their movement can be
followed. The detection can take place in one, two
or three dimensions. This can be done by wireless
means via a transmitter/receiver eyst~m on the
instrument sad at reference points which are located
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at fixed positions in apace or on the area being


worked on.


=t is also possible, particularly for use in


microsurgery, to follow the movement of the section


of the instrument shown in thn operating microscope.


The microscope faiage is delivered to an image-


recording unit which determines the positions, in


the image, of certain features or optical markings


oa the instrument and caleulatee the movement on the


basis of the consecutive position data. To do this,


tracking procedures can also be used.


xf, in addition, the movemmnt of the tissue being


worked on is also detected, this movement likewise


being shown under the operating microscope, the


'r 151. movemment of this eiesue caused, for example, by the


tremor on the part of the pats~at can be included in


the compensation procees.


3. with surface electrodes arranged vn the skin of
the


person operating the instrument, the action


potentials of the underlying muscle can be recorded


(so-called electromyography). If a control system


recogaizea the movement which the corresponding


muscle causes on innervation - for example through


the ability tv adapt - it is possible, by eoa~biniag


the electrode gigaale, to draw conclusions regarding


the deflection the inatrumeat is expected to make.


In this method, the actual use of the iaetrument


'.
would be preceded by a "learning phase" in which the


signal processing unit correlates the electro-


myographic signals with results of other movement-


recording methods, and -thus adapts to individual


features of the operator and to the positioning of


the reference electrodes.


Signal processing
If the movement detection has not already
supplied a signal which corresponds to the ~oaovement
attributed to the tremor and is thus suitable for
directly triggering the actuators, the signal is
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processed.
In general, it will first be necessary to amplify
the sensor eigual. This is followed by as~alyeis which
differentiates between intentional and unintentional
movements on the basis of criteria such as frequency,
amplitude, speed and direetiou. The criteria can be
predefined, adjusted, or adapted automatically. On the
basis of the data, a signal is obtained with which the
actuators are triggered eo that said actuators execute.
at. the working tip of the instrument, relative movements
for compeaBating for the undesired deflections of the
handheld section.
~lctuatoro
'r The actuators can be both purely mechanical
arrangements and also electrical coutrole which are
based. for example, on electromagnetic, capacitive or
piezoelectric principles. Thm actuators execute relative
movements between the handheld section and the movable
section of the instrument. They must be able to execute
the desired moveiaeats with sufficient speed, power and
precision. The actuators can be arranged is such a way
that they can effect both traaslational movements and
rotational movements. For certain requirements, it may be
desirable that the actuators can also temporarily bring
about a rigid connection between the handheld section and
the movable section. The working tip of the instrument
can be mounted in a fixed manner or can be designed to be
exchangeable. Actions, such as the opening and closing of
grippers or forceps, which must necessarily be done from
the handheld section of the instrument, can be triggered
via a flexible power transmission, for example a flexible
push rod, which dose not impede the a~ctuatore, or via
electrically operated adjustment members on the moved
section.
Prdditioaal functions
It u~ay be uae~ul, especially for use in
microsurgery, to trigger the actuators already present is~
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the instrument by means of a push buttoa in such a way
that they cause the working tip of the instrument to
oscillate at frequencies in the soaie or uleraeonie
range, and, for example, when used as a needle holder,
facilitate the penetration of the suture needle into
tissue. ag a result of the rapid micro-movements.
Illustrative e~bodimsat


An illustrative embodiment of the invention is


explained in greater detail below, with reference
to the


attached drawings.


In Fig. 1, reference (1) designates the handheld


section of a medical instrument. Groups of acceleration


meters and angular velocity sensors (2) sit on this


section. A movable section t4) is connected to the


handheld section (1) via a flexible connection (5),
and


on this movable section (~) the working tip is, for


example, a needle holder. The movable section can
be


moved relative to the handheld section (1) by the


arrangement of piezoelectric actuators (3). The actuators


(3) are arranged in such a way that they can bring
about


deflections in all directions transverse to the main
axis


of the instrument.


A coatrol unit fed by a battery is located in the


handheld section (1), said control unit amplifying
the


data supplied by the sensors (2), continuously analyzing


this data and comparing it.


On the basis of adaptable criteria such ae


acceleration, frequency, direction and amplitude of
the


movement, the control unit differentiates between
desired


movements and the hand tremor-of the operator.


To compensate for the hand tremor, the


arrangement of the actuators (3) is triggered in


combination in such a way that these effect relative


movements of the movable part (4) which are adapted
in


direction, speed and amplitude, and the undesired


movements of the hand grip (1) cannot be observed
at the


working tip of the instrument holder (4). For opening
and


closiag needle holders, forceps oz scissors, use ie
made


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of a push rod (7) which flexibly designed in the area of
the flexible connection (5) and which extends through the
inside of the movable section (4). The push rvd is
operated vin a lever (6). A flexible membrane (e) on the
end face of the handheld section (1) is used to seal off
the mechanism.
The function of the instrument is additionally
shown in Fig. 2.
A rapid and unintentional pitching movement of
the handheld section (4), caused by tremor, would lead to
an undesired deflection of the working tip (11) of the
instrument. In order to prevent this, the actuators (3)
are triggered for compensation eo that the movable
section (4) ie moved in the opposite direction, and the
15~ working tip (11) remains at rest.
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Representative Drawing