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Medical Patent Abstract
A handle for a medical device comprises a frame, a transmission,
a slide, a first rack, a sheath, and a cable assembly. The transmission
is mounted to the frame. The slide is moveably attached to the frame
and coupled with the transmission. The first rack is moveably attached
to the frame and coupled with the transmission. The sheath is secured
to the first rack. The cable assembly is secured to the frame and
extends through the sheath.
Medical Patent Claims
We claim:
1. A handle for a medical device comprising: a frame enclosing
a transmission and a driving second rack, said transmission being
mounted to the frame and said driving second rack moveably attached
to the frame and coupled with the transmission, a moveable first
rack at least partially enclosed within the frame, said moveable
first rack being moveably attached to the frame and coupled with
the transmission; a sheath secured to the moveable first rack; and
a cable assembly secured to the frame and extending through the
sheath; wherein the transmission further comprises a gear assembly
having a first gear operably coupled with a second gear, with the
moveable first rack operably coupled with the first gear and slidably
engaged with the frame, and the driving second rack operably coupled
with the second gear and slidably engaged with the frame; and wherein
the transmission has a predetermined mechanical advantage determined
by a parameter of the first gear relative to a parameter of the
second gear; and wherein the first gear or the second gear is a
double gear.
2. The handle of claim 1, wherein the sheath is elongated and flexible,
the cable assembly is elongated and flexible, and the cable assembly
further comprises a snare attached to a distal end of the cable
assembly.
3. The handle of claim 2, wherein movement of the sheath a predetermined
distance relative to the frame encloses or releases the snare.
4. The handle of claim 1, wherein the predetermined mechanical
advantage is not equal to one.
5. The handle of claim 1, wherein the moveable first rack has a
bore extending through the moveable rack and the cable assembly
extends through the bore.
6. The handle of claim 1, wherein the cable assembly further comprises:
an elongated flexible cable; a rigid tube attached coaxially to
a proximal end of the elongated flexible cable; and a plug attached
to a proximal end of the rigid tube.
7. The handle of claim 1, wherein the cable assembly is capable
of transmitting an electrical cauterizing current, and the sheath
and the frame electrically insulate the cable assembly.
8. The handle of claim 1, further comprising at least one finger
ring mounted to the frame, wherein the at least one finger ring
is integral with the frame.
9. The handle of claim 1, wherein the slide further comprises a
thumb ring, wherein the thumb ring is integral with the driving
second rack.
10. A handle for a medical device comprising: a frame; a transmission
mounted to the frame; a slide moveably attached to the frame and
coupled with the transmission, wherein the slide further comprises
a second rack, and wherein the transmission further comprises a
gear assembly having a first gear operably coupled with a second
gear, with the first rack operably coupled with the first gear and
slidably engaged with the frame, and the second rack operably coupled
with the second gear and slidably engaged with the frame; and wherein
the transmission has a predetermined mechanical advantage determined
by a parameter of the first gear relative to a parameter of the
second gear; the first rack moveably attached to the frame and coupled
with the transmission; a sheath secured to the first rack; and a
cable assembly secured to the frame and extending through the sheath,
and wherein the gear assembly further comprises a third gear operably
coupled between the first rack and the first gear, and the slide
translates in the same direction as the first rack.
11. A handle for a medical device comprising: a frame; a gear assembly
rotatably mounted to the frame having a first gear operably coupled
with a second gear and with a mechanical advantage determined by
a parameter of the first gear relative to a parameter of the second
gear; a first rack operably coupled with the first gear and slidably
engaged with the frame; a slide moveably attached to the frame,
having a second rack operably coupled with the second gear and slidably
engaged with the frame; a sheath secured to the first rack; and
a cable assembly secured to the frame and extending through the
sheath; and wherein the gear assembly further comprises a third
gear operably coupled between the first rack and the first gear,
and the slide translates in a same direction as the first rack.
12. The handle of claim 11, wherein the sheath is elongated and
flexible, the cable assembly is elongated and flexible, and the
cable assembly further comprises a snare attached to a distal end
of the cable assembly.
13. The handle of claim 11, wherein the cable assembly further
comprises: an elongated flexible cable; a rigid tube attached coaxially
to a proximal end of the elongated flexible cable; and a plug attached
to a proximal end of the rigid tube.
14. The handle of claim 11, wherein the cable assembly is capable
of transmitting an electrical cauterizing current, and the sheath
and the frame electrically insulate the cable assembly.
15. The handle of claim 11, further comprising at least one finger
ring integrally mounted to the frame, and wherein the slide further
comprises a thumb ring integral with the slide.
Medical Patent Description
TECHNICAL FIELD
This invention relates to a surgical instrument and more particularly,
to an adjustable handle for a medical device that is introduced
into body cavities and manually operated.
BACKGROUND
Medical devices generally have a need for improved actuation. While
handles with an improved tactile feel have been available, they
usually have a one-to-one activation ratio. In such cases, the actuating
element of the handle moves the same amount as the working or gripping
element of the device. For example, in gastroenterology, a medical
device such as a snare may be used to surgically remove polyps from
the colon. In such a procedure, it may be necessary for the snare
to move from three to eleven centimeters. Moving the actuating element
of the handle this same distance, referred to as the "throw"
of the instrument, can be very uncomfortable for a surgeon. For
those with small hands, handles requiring large throws can be especially
difficult to operate, sometimes requiring two hands.
A snare is an electrically conductive loop of wire or cable that
operates by electrically cutting and coagulating tissue that needs
to be removed from the body. A typical surgical snare comprises
an elongated flexible sheath connected at its proximal end to a
handle. An elongated flexible cable extends through the sheath,
with the proximal end of the cable connected to a movable portion
of the handle so that the cable can be retracted and protracted
by the surgeon relative to the sheath. An operating loop or snare
is connected to the distal end of the cable. A surgeon opens and
closes the loop by actuating the movable portion of the handle to
protract or retract the cable. When the cable is in its protracted
or forward position, the operating loop is outside the sheath and
in its fully extended position for snaring, for example, a polyp.
A polyp is a pre-cancerous tissue growth in the colon and rectum.
As the cable is retracted, the loop is drawn into the sheath and
closed.
A snare is inserted through a working channel of an endoscope fitted
with a fiber optic camera. In addition to removing polyps, a snare
can be used to surgically remove esophageal carcinoma or to perform
nephrostomy. To excise a polyp, a doctor first manipulates an endoscope
in the tract of the patient until the polyp is located. The end
of the snare is extended from an insulating sheath and positioned
around the polyp. The snare is then retracted, resecting the polyp.
High frequency electrical current, such as radio frequency (RF)
current, may be applied to the loop to cauterize the polyp and prevent
bleeding.
Attempts have been made to provide a handle with a mechanical advantage
that moves only a fraction of the distance of the snare travel.
These handles have been complex assemblies with expensive manufacturing
costs. In addition, due to friction between the moving parts and
the complexity of the assemblies, some of these handles suffer from
reduced tactile sensitivity, making it more difficult for the surgeon
to operate. Furthermore, some of these handles use an actuating
member to drive the cable and snare, while keeping the sheath stationary.
Other handles actuate both the sheath and cable in opposite axial
directions. This has the effect of pulling the snare into the sheath
as the handle is actuated, which may not be appropriate depending
on the circumstances. What is needed is a better handle for deploying
a snare during endoscopic procedures.
BRIEF SUMMARY
Accordingly, embodiments of the present invention provide a new
and improved handle for a surgical instrument. In one embodiment,
the throw required to actuate the instrument is reduced or increased,
depending on user need. The handle is cost efficient to manufacture
and may be used as a disposable, one-time-use device. The handle
can be easily adapted to provide increased or reduced throws, and
is easier to use by virtue of the modified throw for operation.
The improved handle operates by actuating a sheath over a fixed
cable.
According to a first aspect of the invention, a handle for a medical
device comprises a frame, a transmission, a slide, a first rack,
a sheath, and a cable assembly. The transmission is mounted to the
frame. The slide is moveably attached to the frame and coupled with
the transmission. The first rack is moveably attached to the frame
and coupled with the transmission. The sheath is secured to the
first rack. The cable assembly is secured to the frame and extends
through the sheath.
According to a second aspect of the invention, a handle for a medical
device comprises a frame, a gear assembly, a slide, a first rack,
a sheath, and a cable assembly. The gear assembly is rotatably mounted
to the frame and has a first gear operably coupled with a second
gear. The gear assembly has a mechanical advantage that is determined
by a parameter of the first gear relative to a parameter of the
second gear. The first rack is operably coupled with the first gear
and slidably engaged with the frame. The slide is moveably attached
to the frame and has a second rack that is operably coupled with
the second gear and slidably engaged with the frame. The sheath
is secured to the first rack and the cable assembly extends through
the sheath and is secured to the frame.
A third aspect of the invention is a method of manufacturing a
handle for a medical device. The method includes the steps of providing
a frame and mounting a gear assembly having a mechanical advantage
to the frame. The method also includes the step of slidably mounting
a slide to the frame, where the slide is operatively coupled with
the gear assembly. The method also includes the steps of securing
a cable assembly to the frame and slidably mounting a moveable rack
to the frame, where the moveable rack is operatively coupled with
the gear assembly. The method also includes the step of attaching
a sheath to the moveable rack, where the cable assembly extends
coaxially through the sheath and where the sheath is retracted and
protracted relative to the frame as the slide is actuated.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the handle showing the sheath in
a partially retracted position;
FIG. 2 is an exploded view of the handle;
FIG. 3 is a top view of the handle shown with the upper frame removed,
illustrating the sheath protracted over the snare;
FIG. 4 is a top view of the handle shown with the upper frame removed,
illustrating the sheath partially retracted from the snare;
FIG. 5 is a perspective view showing the cable assembly, sheath,
and moveable rack;
FIG. 6 is a detail top view of the gear assembly in FIG. 3; and
FIG. 7 is a detail perspective view of the slide, lower frame,
and plug in FIG. 3.
DETAILED DESCRIPTION OF THE DRAWINGS AND THE PRESENTLY PREFERRED
EMBODIMENTS
FIGS. 1 and 2 disclose a handle 10 and a snare 80 for a medical
device. The handle 10 includes a frame 12, a sheath 70, a slide
30, a gear assembly, a moveable rack 50, and a cable assembly 60
with cable 62. A thumb ring 34 is at the proximal end of handle
10. Snare 80 is mounted to the distal end of cable 62.
The frame 12 is made up of an upper frame 14 and a lower frame
15, with lower frame 15 connected to upper frame 14 with a snap
fit or an interference fit, although other means of joining the
two parts may be used. Handle 10 preferably includes finger rings
20 disposed on opposite sides of and integrally formed with frame
12. Bosses or locators 22 are integrally formed with lower frame
15 and mate with corresponding locators (not shown) integrally formed
with upper frame 14 to align and join lower frame 15 with upper
frame 14.
Handle 10 also includes slide 30 that fits and slides within frame
12. As shown in FIG. 2, slide 30 includes thumb ring 34 at the proximal
end and a driving rack 32 at the distal end. Slide 30 also has a
slot 36 formed between thumb ring 34 and driving rack 32. Driving
rack 32 may be integrally formed with slide 30, and preferably is
a bar with teeth on a face for gearing with a pinion or a gear to
transform linear motion to rotary motion. Slide 30 is assembled
such that two locators 22 integrally formed with lower frame 15
are positioned within slot 36. Locators 22 positioned within slot
36 constrain the movement of slide 30, serving to both align the
movement of slide 30 within frame 12 and to restrain the movement
of slide 30 such that it cannot be slidably removed from frame 12.
As shown in FIG. 2, an integral groove 33 is formed along the top
side of the driving rack 32. Not shown, an integral groove is also
formed along the bottom side of driving rack 32. Slide rails 17
are integrally formed on the inside surfaces of upper frame 14 and
lower frame 15. As slide 30 is moved into and out of frame 12, driving
rack 32 slides over rails 17 on integral grooves 33.
As seen in FIGS. 3, 4, and 6, driving rack 32 engages and drives
a transmission preferably consisting of a gear assembly made up
of coupled gears. The gear assembly consists of a double gear 41,
made up of a smaller first gear 42 and a larger second gear 43,
and a third gear 44. Double gear 41 may be integrally formed, with
first gear 42 and second gear 43 concentrically aligned, sharing
an axis of rotation, and rotating at the same angular velocity,
but operating in different planes. Double gear 41 is mounted and
rotates about a first axle 24 integrally formed with frame 12 (see
FIG. 3). Third gear 44 is mounted and rotates about a second axle
25 integrally formed with frame 12. Driving rack 32 directly engages
the first gear 42 of double gear 41, which in turn rotates second
gear 43, which engages and rotates third gear 44. Third gear 44
engages moveable rack 50, causing moveable rack 50 to translate
distally or proximally, which in turn drives a sheath 70 to enclose
or release snare 80. The gear assembly described above preferably
uses a series of coupled spur gears operating in parallel planes.
However, the gears may also operate in intersecting or skew planes,
where bevel, helical, hypoid, or other suitable gears would then
be used to couple slide 30 to moveable rack 50.
As seen in FIG. 5, an integral groove 51 is formed along the top
side of moveable rack 50. A corresponding integral groove 51 is
also formed along the bottom side of moveable rack 50. Grooves 51
constrain moveable rack 50 such that it slides along and is aligned
by corresponding moveable rack rails 18 that are formed on the inside
surfaces of upper frame 14 and lower frame 15. In addition, as seen
in FIG. 5, a bore 54 runs through the length of moveable rack 50.
Bore 54 is preferably a tapered through-hole, with a larger diameter
at the proximal end of moveable rack 50 and a smaller diameter at
the distal end.
Cable assembly 60, illustrated in FIGS. 2 and 5, is immovably attached
to frame 12. Cable assembly 60 runs through bore 54 in moveable
rack 50, and extends distally from frame 12. Bore 54 allows cable
assembly 60 to run through moveable rack 50 into sheath 70. As moveable
rack 50 is actuated, moving sheath 70 with respect to frame 12,
cable assembly 60 remains immovably attached to frame 12. Cable
assembly 60 includes cable 62, which is preferably elongated and
flexible. Cable 62 is also preferably electrically conductive, such
as a solid wire or braided cable of stainless steel, but may have
rigid portions. A preferred cable has a diameter of approximately
0.75 mm, although other cable diameters may be used.
A proximal end of cable 62 is attached to a rigid tube 64. Rigid
tube 64 is preferably formed from stainless steel grade 304 tubing,
approximately 1.1 mm in diameter and 15 cm long, and crimped onto
cable 62. Other methods of connecting rigid tube 64 to cable 62
may be used, such as soldering or brazing. A short length 68 at
the proximal end of rigid tube 64, approximately 4-5 mm, is bent
at a 90.degree. angle and is inserted into an orifice 67 located
in the plug 66, as illustrated in FIG. 7. Rigid tube 64 may be secured
to plug 66 by soldering, brazing, a set screw, a friction fit, or
any other technique suitable for an electrical connection. Plug
66 is positioned in a plug recess 28 integrally formed on the inner
surfaces of frame 12. For clarity, FIGS. 3, 4, and 7 illustrate
plug 66 positioned in plug recess 28 in lower frame 15, with upper
frame 14 shown removed. However, during assembly, it is preferable
to first position plug 66 in a plug recess in upper frame 14 (not
shown), and then attach rigid tube 64 to orifice 67 in plug 66.
As upper frame 14 is placed over lower frame 15, plug 66 is immovably
secured in plug recess 28. Additionally, a friction fit or minimal
clearance fit between the inner surfaces of frame 12 and rigid tube
64 prevents rigid tube 64 from detaching out of orifice 67 in plug
66, providing additional security. Rigid tube 64 extends into bore
54 in moveable rack 50, so that a length of rigid tube 64 remains
within bore 54, regardless of the relative position of moveable
rack 50 with respect to frame 12.
As seen in FIG. 2, the distal end of cable assembly 60 may terminate
in a snare 80. For example, a snare such as the AcuSnare.RTM. from
COOK.RTM., Wilson-Cook Medical Inc., GI Endoscopy, Winston-Salem,
N.C., USA, can be attached to the distal end of cable 62. However,
other types of gripping elements or working elements, such as baskets,
grasping forceps, angled snare loops, or point-type cauterization
devices can be substituted for snare 80. In the embodiment disclosed
herein, an electrical current, such as RF (radio frequency) electrical
current, may be applied to plug 66. The current is conducted along
rigid tube 64 to cable 62 to snare 80, to electrically cauterize
a polyp. If an electrical current is applied, however, the cable
assembly 60 and snare 80 must be electrically insulated by sheath
70 (described below) and frame 12, preventing inadvertent electrocution
to either the patient or user.
As seen in FIG. 5, a proximal end of sheath 70 is secured to moveable
rack 50. Sheath 70 is preferably an elongated flexible tube made
from a length of PTFE (polytetrafluoroethylene) or Teflon.RTM. tubing.
Sheath 70 may also be made from any flexible lubricious material
that does not conduct electricity, such as polyimide tubing. Cable
assembly 60 and sheath 70 are coaxially aligned, such that sheath
70 covers cable assembly 60. Sheath 70 can be secured to bore 54
of moveable rack 50 through a friction fit, such as by crimping
an external metal ring 72 to the outer diameter of sheath 70, and
then press fitting that assembly into bore 54 of moveable rack 50.
For greater attachment strength, a metal ring (not shown) may also
be placed inside the inner diameter of sheath 70 before external
metal ring 72 is crimped onto sheath 70. Sheath 70 is preferably
sized with an outer diameter of approximately 2.3 to 2.4 mm and
an inner diameter of approximately 1.5 to 1.6 mm. Alternatively,
the inner diameter of sheath 70 is sized to enable cable assembly
60 and snare 80 to have substantially free longitudinal movement
along the entire length of sheath 70.
Frame 12, slide 30, the gears in the gear assembly, and moveable
rack 50 may be made from any medically suitable, and preferably
electrically insulating, material. To make handle 10 inexpensive
and disposable, frame 12, slide 30, the gears, and moveable rack
50 may be molded from a suitable plastic such as polycarbonate,
acetal, or ABS (acrylonitrile-butadiene-styrene). Frame 12 may be
injection molded as a clam shell with upper frame 14 and lower frame
15 separately injection molded and joined later by melting, snap
fitting, or applying a medically acceptable adhesive, such as cyanoacrylate.
In addition, a biocompatible silicone type lubricant may be used
to reduce friction on the gears, first axle 24, second axle 25,
slide rails 17, moveable rack rails 18, the inner diameter of sheath
70, or any other moving parts.
Referring now to FIGS. 3, 4, and 6, as slide 30 is pressed into
frame 12 with thumb ring 34 in a distal direction, driving rack
32 drives first gear 42 of double gear 41 clockwise. As second gear
43 is axially connected to first gear 42, second gear 43 is also
rotated clockwise, which in turn rotates third gear 44 counterclockwise.
This counterclockwise rotation of third gear 44 drives moveable
rack 50, causing it to move distally away from frame 12, which is
upward in FIG. 4 and to the left in FIG. 6. As sheath 70 is secured
to moveable rack 50, sheath 70 also moves distally away from frame
12. Because cable assembly 60 is immovably attached to the proximal
end of frame 12, cable assembly 60 does not move relative to frame
12, and sheath 70 is protracted over cable assembly 60 and snare
80, covering snare 80 as shown in FIG. 3. Pulling slide 30 and thumb
ring 34 away from frame 12 reverses this action, causing sheath
70 to be retracted from cable assembly 60 and snare 80, exposing
snare 80, as shown in FIG. 4.
Parameters of first gear 42 and second gear 43, such as the outer
diameters or the radii, may be selected so that a desired mechanical
advantage is achieved, where the displacement or movement of slide
30 relative to frame 12 is a particular ratio to the displacement
or movement of moveable rack 50 and sheath 70. A gear ratio of 1:2
is illustrated in FIGS. 3 and 4. In such a case, a surgeon would
only need to move thumb ring 34 about 5 cm to achieve a 10 cm displacement
of sheath 70 and moveable rack 50 relative to snare 80. However,
the sizes of the gears can be selected so that other mechanical
advantages are achieved, such as 1:4, 2:1, or 4:1, providing for
reduced or increased handle throws as appropriate. In addition,
third gear 44 can be eliminated, with moveable rack 50 directly
engaging second gear 43. In such a case, as slide 30 is pressed
into frame 12, moveable rack 50 and sheath 70 would move in an opposite
direction to slide 30, retracting moveable rack 50 and sheath 70
and exposing cable assembly 60 and snare 80.
As snares or other gripping or working elements are sold in a wide
range of sizes, a sheath may have to be displaced widely varying
distances relative to the snare. Accordingly, the stroke length
of a slide in a handle may be adjusted to accommodate the different
stroke lengths required to fully actuate the various snares or other
working elements. During assembly, the manufacturer can control
the total stroke length that the slide must move relative to the
frame for retracting or protracting the sheath. Before upper frame
14 is connected to lower frame 15, the slide 30 and moveable rack
50 can be placed on slide rails 17 or moveable rack rails 18, respectively,
at different starting positions along the rails. After the gears
and other interconnected components are coupled with driving rack
32 and moveable rack 50, the stroke length is set.
In operating handle 10, a user grasps thumb ring 34 and finger
rings 20 and pushes thumb ring 34 into frame 12. As seen in FIG.
3, in this fully protracted position, sheath 70 is protracted over
cable assembly 60 and snare 80. In one application, a surgeon would
insert the distal end of sheath 70 through the working channel of
an endoscope into a patient's colon until the polyp is located.
Using one hand, the surgeon could then pull thumb ring 34 away from
finger rings 20 (illustrated in FIG. 4) causing sheath 70 to retract
from snare 80, exposing and opening snare 80 so that it can be used
to snare the patient's polyp. After the snare is positioned around
the polyp, the surgeon would then push the thumb ring 34 back into
the frame 12. This causes the sheath to protract over snare 80,
closing snare 80 around the polyp. With the 1:2 gear ratio disclosed
in FIG. 6, a surgeon would only need to move thumb ring 34 about
5 cm to achieve a 10 cm displacement of sheath 70 and moveable rack
50 relative to snare 80.
While the invention has been described with reference to details
of the illustrated embodiment, these details are not intended to
limit the scope of the invention as defined in the appended claims.
For example, in place of a gear assembly, the handle may use another
type of transmission to create a mechanical advantage. A transmission
made up of levers in a linkage system, pulleys, or a hydraulic or
pneumatic actuator may also be used to transfer a mechanical advantage
from the slide to the sheath. For a linkage system, a distal end
of the slide may be attached to one point along a lever, with a
proximal end of the sheath attached to another point along the lever.
A pivot may be placed along the lever so that a desired mechanical
advantage is achieved. If a pulley system is used, the slide may
be connected to a pulley that is slidably attached to the frame.
A flexible pulley cable capable of transmitting both tensile and
compressive forces may wrap around the pulley, connected to the
sheath at one end and secured to the frame at another end. Alternately,
a hydraulic or pneumatic actuator may be used to create the desired
mechanical advantage. It may be desired to use one or more hydraulic
or pneumatic actuators in a push-pull arrangement, with one or more
actuators pushing the sheath relative to the frame, and one or more
actuators pulling the sheath relative to the frame. The mechanical
advantage would be controlled by adjusting the hydraulic or pneumatic
diameters of the actuators.
In addition, the handle can be used for surgical instruments other
than snares. In fact, the handle can be used in connection with
any surgical instrument having first and second coaxial members,
such as retrieval baskets, irrigation systems, and graspers, among
others. All such devices are meant to be included by the following
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