ZMQ B42 20 MM ado .n

12 Pages·2013·1.22 MB·English

US005403191A
United States Patent [191 [11] Patent Number: 5,403,191
Tuason [45] Date of Patent 0 Apr. 4, 1995
0
[54] LAPAROSCOPIC SURGERY SIMULATOR Assistant Examiner-Jeffrey A. Smith
AND METHOD OF USE
[57] ABSTRACT
[76] Inventor: Leo B. Tuason, 130 Boring Pl.,
An apparatus used in simulating the human body cavity
Martinsville, Ind. 46151
whereby an individual user can practice endoscopic
[21] Appl. No.: 142,104 surgical procedures by duplicating the operative steps
[22] Filed performed on actual true to life condition for the pur
Oct. 28, 1993
' pose of learning the art and constantly improving the
skill of eye-hand coordination and manual dexterity.
Related US. Application Data
The simulator is provided with open sides to gain access
[63] Continuation of Ser. No. 760,684, Oct. 21, 1991, aban into the cavity for placement of objects simulating
doned. human organs which are then mounted and anchored
[[[ 555 unvlo. .mULFS .“ ado B42Z MQ /222 66 877 inside the cavity for practice simulation in instrument
6.f “" amw wh mmm" /
MM2 0 ,3 / manipulation. Surgical instruments are inserted into the
.n
cavity through the pre-established apertures on the
transparent plastic panel and the instruments are manip
[56] References Cited ulated while performing the practice procedure without
U.S. PATENT DOCUMENTS the bene?t of direct binocular vision on the obj ect-simu
434/262 lations; instead the trainee imitates and directs the activ
3,775,865 12/1973 Rowan
ities inside the cavity under vision using the endoscopic
4,321,047 3/1982 Landis 4 3 Mu 2
4,789,340 12/1988 Zikria video-monitor system or by similar indirect viewing
4,907,973 3/1990 Hon method provided by the re?ecting mirrors of the two
5,055,051 10/1991 Duncan 434/267 X mirror concept, thus mimicking a real life operative
434/267 X condition.
55,,016419,,128770 190//11999912 JMecraKteho wn
434/267 X
Primary Examiner-—Cary E. O’Connor 4 Claims, 5 Drawing Sheets
um
I,
‘it
Z

US. Patent Apr. 4, 1995 Sheet 2 of 5 5,403,191
f/GT-4 f/@ 5
,/ F/G. 4a ,/ 7:76. 50.
US. Patent Apr. 4, 1995 Sheet 3 of 5 5,403,191
m
H
a.
QWRVN
“in.; \\d Aa’‘;
I?
7r%,.
__\\w/\\,,4\\/ \ 1 w 6.
‘s H“
2
‘Ki/w
5,, /
Z 5 7
\
was
E
7
4
S. I mo
(o
$6
E2V,,..
.
Z
/
US. Patent Apr. 4, 1995 Sheet 4 of 5 5,403,191
QB
W
/// /// /// / /
L 26

’ 5,403,191
1 2
roscope inserted into the abdominal cavity through a %
LAPAROSCOPIC SURGERY SIIVIULATOR AND inch incision and a few more additional similar incisions
METHOD OF USE for the delicate slender instruments like dissectors, tis
sue grasping forceps, suture-ligatures and laser probe,
CROSS REFERENCE TO RELATED 5 manipulates these tools outside the body cavity to re
APPLICATION move the diseased gall bladder by watching a video
This is a continuation of application Ser. No. screen monitor. Surgeon’s hands are no longer in direct
07/760,684, ?led Oct. 21, 1991, entitled Laparoscopic contact with body tissues when performing these ma
Surgery Simulator, which is now abandoned. neuvers in the new laparoscopic surgery and all intri
cate movements executed intracorporeally and extra
FIELD OF INVENTION corporeally are assisted by the indirect viewing pro
The present invention relates to a device for teaching, vided by the Endoscope Video-TV. Monitor system.
training and improving the eye-hand coordination of The new initiate in this high-tech endoscopic surgical
the surgeon or trainee in the new surgical high-tech procedures is met with dif?culties in the visual orienta
VIDEO ASSISTED ENDOSCOPIC SURGERY by 15 tion and eye-hand coordination. To acquire operative
the use of an apparatus wherein the operative tech skill required to gain competence in this video assisted
niques like suturing tissues, cutting off organs and tying surgical procedures and maintain the pro?ciency of the
knots are simulated to resemble real-life conditions. The surgeon, he must continuously as often as possible per
simulator also incorporates visual simulation as well as form these intricate maneuvers on live patients and must
surgical maneuvers mimicking the instrumentation that 20 practice on inanimate objects using an apparatus like the
one would pursue in endoscopic surgery in real life present invention.
operating condition. The earlier model made and widely used training
device were built in Germany and one such device is
BACKGROUND OF THE INVENTION
called Semm Pelvi-Trainer. This simulator has a trans
Endoscopy is de?ned as a direct visualization of body 25 parent panel on top with several openings where instru
cavities by the use of an instrument called an ENDO
ments and viewing scope are inserted and manipulated.
SCOPE (a small slender telescope with a built-in light
It is provided with a method of holding organs which
source for illumination and a video camera at the back are suspended from the top panel using bead chains and
end of the endoscope connected to a TV monitor).
clips. The exercise procedures are performed on living
When the body cavity of the abdomen is entered during
tissues like placenta or even muscle. Though these de
the operation, it is called LAPAROSCOPY, on the
vices have prominent features, they also have signi?
chest it’s THORACOSCOPY and the lower abdomen
cant drawbacks. This particular model was primarily
or pelvic region it’s PELVISCOPY.
constructed for training Gynecologists so that simula
The early beginning of Endoscopic Surgery took
tion of endoscopic operative techniques are geared and
placed in Europe and pioneered by Gynecologists
limited to the pelvic organs, thus it is appropriately
where they performed tubal ligations, removal of ovar
named ‘Pelvi-Trainer’.
ian tumors or cysts, lysis of adhesions and as a diagnos
Although this simulator functions satisfactorily in
tic procedure. Some of these surgeons were brave
enough to remove the appendixes through % inch ab most cases, it tends to suffer from several problems
which limits its usefulness. One such drawback is that, it
dominal incisions.
encourages the use of Pelviscope (Endoscope I, please
It was the successful and safe removal of the appendix
that led the aggressive and innovative general surgeons refer to Key Words). Endoscopes are expensive and are
to explore the vast potential of the new surgical tech not readily available to many surgeons much less to the
nology. Thus, the removal of the gall bladder or initiates.
Laparoscopic Cholecystectomy was ?rst performed in 45 Yet another drawback of the Pelvi-Trainer is that,
Europe in 1987 and only attracted minor curiosity. when the surgeon uses the Pelviscope, he actually
General surgeons were slow in accepting this new carries out the simulated instrumentation and practice
video assisted surgery but the procedure crossed the procedures under direct monocular vision. This type of
Atlantic in the early 1988 and thereafter several US. visualization as applied in endoscopic surgery has been
Surgical Centers began using this new operative tech replaced by Endoscope-Video-Monitor System which
nology with unerring success. The Laparoscopic Cho operates under indirect binocular vision, a system that is
lecystectomy has now become a standard Operative being used in actual live endoscopic operations and in
procedure in removing a diseased gall bladder. some other training devices.
The laparoscopic approach to the gall bladder and Still another drawback of this simulator is that, it has
other organs has distinct advantages over the standard 55 only one plastic panel with multiple openings that are
open technique in that, for many procedures visualiza positioned primarily for practice procedure on the pel
tion is very much improved as the endoscope can be vic cavity. It has no provision for practice simulation in
placed directly over the surgical ?eld several times the other body cavities like the chest, upper abdomen
magni?ed. Other advantages include reduced hospital and the region of the kidneys.
ization, health care costs, a more rapid and less painful Additional drawback of the Pelvi-Trainer is that, in
convalescence with faster return to employment and the practice of simulation, the trainee can only use
?nally an improved cosmetic postoperative incisional human tissue like placenta or animal parts. These mate
wound scars results. rials are not readily available and their procurement
The introduction of state-of-the art instruments and might be difficult.
equipment has made possible the diversi?ed laparo 65 Another simulator that is recently brought out to the
scopic surgical procedures now being used in many public is the Mckeown surgical training apparatus. This
hospitals throughout the United States and some is an apparatus that has all its sides of black plexiglass
countries around the world. The surgeon with his lapa making the inside cavity pitch-dark. This device appar
5,403,191
3 4
ently functions substantially identical in some aspects to simulations which are made of foam rubber mounted
the Semm Pelvi-Trainer One drawback that is very and anchored on pads and platforms of the same mate
evident is that, the trainee has to use the apparatus with rial in a unique modular arrangement. This is an impor
the aid of a scope (Endoscope I) which provides a mag tant feature not provided by the other simulators and
ni?ed direct monocular vision similar to the Semm one that appeals to the individual user because it’s easier
Pelvi-Trainer. to change wornout object-simulations during practice
Yet another drawback of this apparatus is that, it has procedure.
provision only for practice simulation on materials like Fifth, the present invention is constructed with all
animal parts or even human tissue which are suspended lateral sides completely open allowing easy access to
from the top plexiglass panel by chain beads and clips, a the inside cavity for placement and removal of object
method exactly similar to the Semm Pelvi-Trainer. simulations used in the exercise procedure and the open
The top lid plexiglass of the McKeown apparatus has sides permits easy cleaning after the simulation experi
multiple puncture positions that are appropriately used ence. Some of the simulators are partially enclosed and
for simulation practice exercise on limited organ loca provided by side panel with access window which may
tion, i.e., the placement and location of the apertures on require more time to clean the inside cavity after using
the top lid is not suitable for practice simulation of objects like, human placenta or animal tissue.
endoscopic surgery on the chest or in the region of the
OBJECTS AND SUMMARY OF THE
kidneys and this is also a drawback of the device.
INVENTION
Still another drawback of this training apparatus is
that, the trainee must always use an endoscope to per Key Words and De?nition.
form practice simulation. The endoscope is an expen Endoscopy and Laparoscopy . . . interchangeable
sive item and are not readily available to most trainees, words which means visualization of organ objects
therefore the use of such apparatus is limited to hospital and surgical maneuvers inside the body cavity with
setting where the endoscope might be accessible to the the use of an endoscope (a slender telescope).
trainee. 25 Old Generation Endoscope (Endoscope I) . . . an
Another drawback of this device is that, the mount endoscope that is plain having integral parts of
ing of the organ object being practiced on is by clamps viewing lenses and ?beroptic illumination thus,
on bead chains suspended from the top plexiglass panel providing the individual user a magni?ed direct
which makes the object a moving target and would monocular viewing capability, akin to looking
need a steady hands to perform simulated delicate sew through a standard telescope.
ing technique and a near perfect result might be difficult New Generation Endoscope (Endoscope II) . . . an
to achieve. endoscope of the present and the future, has an
It is clear and evident that the present invention has integral system of viewing lenses, ?beroptic illumi
proven to have advantages over the other simulators nation and a video camera attached to the rear end
and the versatility of its function is a welcome asset in 35 of the endoscope, connected to a light source and
achieving improved skill on eye-hand coordination. ?nally to a high resolution T.V. monitor, thus pro
The fact that the present invention has shown distinct viding the individual user a magnified indirect bin
features that none of the other simulators possess makes ocular viewing capability (the surgeon using both
it more desirable for the surgeon to practice simulation eyes to view the activities inside the body cavity
techniques on this recent cutting edge simulator. First, through the T.V. monitor).
one advantage of the present invention over the others Minimally Invasive Video Assisted Endoscopic Sur
is the use of the Two Mirror Concept, a system of indi gery . . . the surgeon uses the New Endoscope II in
rect binocular way of viewing objects and simulation of the practice of the high-tech endoscopic proce
activities inside the cavity of the simulator. This is the dures making % inch skin incisions (instead of 6 to 8
same viewing method used in real life operative condi 45 inches in the standard procedure) and performs
tions with the aid of the Endoscopic-Video-Monitor minimal transgression on body tissues.
System.
Intracorporeal . . . inside body cavity.
Second, the individual user can perform practice Extracorporeal . . . outside body cavity.
procedure in simulating visual and instrument manipu
Simulator and Apparatus . . . are interchangeable
lation on the present invention under indirect binocular terms which have the same meaning.
vision applying either system. If for some reason the Trocar . . . instrument used to puncture the body
Endoscopic-Video-Monitor System is not available, the wall, thus providing an aperture for the instrument
trainee can still practice simulation that mimics true to or endoscope to gain access into the body cavity.
life operating situations using the Two Mirror Concept Hook-Loop Fastener Set . . . this is generic and VEL
System, a feat unmatched by the other simulators. 55 CRO is an example. The set consists of paired fas
Third, with the interchangeable clear and transparent tener tapes mounted on a solid material placed
plastic panels that have strategically positioned aper inside the cavity of the simulator, whereby during
tures, the surgeon can simulate practice surgical proce the practice procedure, the trainee inserts a tissue
dures mimicking real life operating conditions on the holding instrument through the trocar port aper
different body cavities like the chest, upper abdomen, ture and use the instrument to peel and shift one of
pelvic and the region of the kidneys by using the spe the ‘hook’ tape and attach the same to the adjacent
ci?c panel for each individual operative technique on corresponding mate ‘loop’ tape and the process is
the chosen cavity. These practice maneuvers when done repeatedly. The trainee manipulates the in
translated into the actual live operation, the individual strument from outside the cavity while viewing the
user will recall where to place the punctures on the 65 inside activities through the clear-transparent plas
body wall. tic panel under indirect binocular vision aided by
Fourth, additional advantage of the present invention the Two Mirror Concept. This practice exercise
over the other simulators is the use of life size object enhances eye-hand coordination.
5,403,191
5 6
Plastic . . . this is generic and PLEXIGLAS, a poly~ can reinforce his skill on simulated visual and instru
mer, is an example. The plastic panel is a clear and ment manipulation.
transparent material simulating the body wall of Finally, the simulator of the present invention pos
the living, provided with multiple pre-established sesses indispensable conceptual characteristics that re
apertures or. trocar ports which are covered by semble real life operating conditions. When the simula
resilient pressure sensitive circular rubber plates tor is properly used, it can provide a means to learn
(rubber foam material) with small opening at the surgical techniques and allows a surgeon familiar with
center through which the instruments are inserted, the human anatomy and skilled in conventional surgery
thus providing a simulated resiliency of a living to attain a certain amount of dexterity necessary to
body wall as the trocar penetrate it to gain entry safely perform endoscopic surgery in a true to life con
into the cavity. dition.
Endoscope-Video-Monitor System . . . an indirect
BRIEF DESCRIPTION OF DRAWINGS
binocular viewing system incorporating the Endo
scope II with its ?ner attributes as applied in a real The various aspects of the present invention will—be
life situation whereby the surgeon uses both eyes to fully understood when the following portions of the
view the activities inside the body cavity through a specifications are read in conjunction with the accom
TV. monitor. panying drawings. Furthermore, it is understood that
Two Mirror Concept . . . the use of a pair of reflecting the description of the construction of the apparatus is
mirrors strategically positioned atop the simulator based on the initial prototype whose frame is of wood
when adjusted accordingly will provide a simu 20 material and that these simulators could be made out of
lated indirect binocular way of viewing object plastic material or one of its polymers like PLEXI
simulations and maneuvers inside the cavity of the GLAS for market.
simulator. FIG. 1 is a side elevation view of the simulator show
The preferred embodiment of the present invention ing one end of a rectangular shaped hollow box with
would provides a simulator that is rectangular shaped 25 two mirrors on top, a florecent lamp and plastic panel in
hollow box simulating the human cavity where objects dash lines;
and activities are viewed through a clear and transpar FIG. 2 is a side elevation view of FIG. 1 showing
ent plastic panel under indirect binocular vision aided another side of the box, the two mirrors with their
by the Two Mirror Concept, thus it affords an individ re?ecting surfaces facing each other and an open lid or
ual user a means to improve his skill in eye-hand coordi hatch illustrated as dash lines;
nation and manual dexterity. FIG. 3 is a plan top view of the simulator showing the
Another object of the present invention is to provide two mirrors and object-simulation mounted on a foam
an apparatus that is multipurpose in its function, i.e., an rubber pad illustrated as dash lines observed through
individual user is able to do practice procedures simu the clear and transparent PLEXIGLAS panel also in
lating real life condition using either the Endoscope 35 dash lines;
Video-Monitor System or the Two Mirror Concept, FIG. 4 is a top and FIG. 4a is a side elevation view of
both of which are indirect binocular viewing systems. the PLEXIGLAS panel showing multiple openings on
When the surgeon decides to use the Two Mirror Con the circular pressure sensitive rubber plates;
cept in a practice simulation, he mimics the real life FIG. 5 is a top and FIG. 5a is a side elevation view of
condition and carries out instrument manipulation 40 the PLEXIGLAS panel similar to FIGS. 4 and 40 ex
under indirect binocular vision whereby one mirror cept that it shows multiple openings at different location
focuses on the object-simulations inside the cavity of the and number speci?c for individual operative practice
simulator and re?ects on the other mirror through the procedure;
clear-transparent plastic panel, producing a reversed FIG. 6 is a perspective view of an alternative embodi
mirror image. The surgeon watches the second mirror 45 ment of the simulator comprising components already
thereby seeing the organ-simulation in its normal ana mentioned in FIGS. 1 and 2 except the lid or hatch is
tomical position. closed and illustrating the modular orientation of the
Yet another object of the present invention is to pro object-simulations and the two mirrors showing the
vide an interchangeable clear and transparent plastic re?ecting image projection in dash lines;
panels with multiple pre-established strategically posi FIG. 7 is similar to FIG. 6 except that the trocars and
tioned apertures or trocar ports on each panel speci?c instruments are illustrated in their functional positions
for an individual surgical procedure on whatever simu entering the cavity through the pre-established aper
lated body cavity is chosen—like the chest, abdomen or tures on the plastic panel;
pelvic region. FIG. 8 is a perspective view similar to FIG. 6 of the
Still another object of the present invention is to 55 simulator except that the top hatch frame is open illus
provide a method of positioning object-simulations by trated as dash lines and this allows the placement and
modular arrangement. These object-simulations can be changing of the PLEXIGLAS panel;
in the shape of human organs made of foam rubber FIG. 9 is a cross section of the simulator as taken
which are mounted on pads of similar material and substantially along lines 30 to 30 of FIG. 10 showing an
anchored to a foam rubber platform the size of which is 60 instrument inside a trocar in its functional position being
large enough to occupy the entire base of the simulator, inserted through the circular rubber plate of the
hence an individual user has a means of quick and easy PLEXIGLAS panel and also shows simulated move
change of worn-out object-simulation with new ones ments of the instrument in dash lines and arrows;
during the practice simulation of real life operating FIG. 10 is a perspective view of an alternative em
condition. 65 bodiment of the simulator similar to FIG. 7 except that
Another embodiment of the present invention pro the Hook-Loop Fastener Practice Set has replaced the
vides a simulator that incorporates the Hook-Loop large foam rubber platform and showing instrument
Fastener Practice Set, a method by which the surgeon movements in dash lines and arrow;
5,403,191
7 8
FIG. 11 is a side elevation plan of FIG. 12; vention herein involved, it is intended that all matter
FIG. 12 is a perspective view of an alternative em contained in the above description or shown in the
bodiment of the simulator showing the Hook-Loop accompanying drawings shall be interpreted in an illus
Fastener Practice Set illustrating the relationship be trative and not in a limiting sense.
tween the hook and the loop tapes mounted on a solid It is apparent that many more surgical procedures
material and also shows a fastener tape at the bottom of could be learned by using the apparatus and practice
the Set which mates with a tape glued to the base of the Sets on simulation and the previous description is in no
simulator. way a limit to the utilization of the simulator of the
present invention.
DESCRIPTION OF THE PREFERRED
10
EMBODIMENT DETAILED DESCRIPTION OF THE
INVENTION
The apparatus of the present invention is a hollow
box having a cavity that simulates that of the human The description of the present invention simulator 1 is
body wherein the practice exercise on simulated surgi based on the initial prototype which is constructed of
cal procedures are performed. The rectangular box wood material for all its frame and that these simulators
with inside cavity is well demonstrated in FIGS. 6, 7, could be manufactured out of plastic material or one of
and 8 and here the practice procedures are accom its polymer PLEXIGLAS to market.
plished simulating those surgical techniques that trainee Referring ?rst to FIGS. 1 and 2 of the drawings, they
would pursue in real life operative condition. show two views of the simulator 1, a rectangular shaped
The simulator of the present invention has open sides 20 box having 6 sides; 2 and 3 are the end sides, 4 and 5 are
providing easy access into the cavity for setting up the lateral sides, 7 is the bottom side and batch 6 is the
object simulations of foam rubber material in the shape top side. This is an enclosed hollow box with a cavity 15
of human organs, mounted and anchored on pads and inside simulating that of human body cavity.
platforms of the same material, in which the trainee Hatch 6 is provided on the top of simulator I and is
practices simulation of surgical techniques like suturing, attached to side 4 frame by two hinges 8 and the free
knot tying, and instrument manipulation, thus enhanc end of hatch 6 has latch 9. Hatch 6 in FIGS. 1 and 2 is
ing his skill in eye-hand coordination. in closed position. When hatch 6 is opened as in FIG. 8,
A clear and transparent PLEXIGLAS panel occu it allows the individual user to change the clear and
pies the top side of the simulator which correspond to transparent plastic panel 17 shown also in FIG. 8. In the
the body wall in real life condition. Multiple pre-estab functional position of plastic panel 17, it is slipped into
lished apertures or trocar ports are in this plastic panel the grooves 23 provided at the top end frames of sides
which is covered by resilient pressure sensitive circular 2, 3, 4, and 5 illustrated best in FIG. 9. In this particular
foam rubber plates and at the center of the plates are embodiment, when the hatch 6 is closed and the plastic
small openings through which instruments are inserted panel 17 is in its functional position, shown in FIGS. 6,
during practice simulation. The interchangeable feature 7 and 10 with latch 9 in place, the cavity 15 is created,
of the plastic panel makes it versatile in its function whereby most of ‘the practice simulation takes place.
whereby a surgeon can simulate practice procedures At the top end frame of side 2 in FIGS. 1, 6, 7 and 8
mimicking real life operating conditions on the different is attached ?uorescent lamp 16 which can provide
body cavities like the chest, upper abdomen, pelvis and added illumination inside the cavity 15.
the region of the kidneys by using the speci?c panel for The clear-transparent plastic panel 17 as shown in
each individual operative technique on the chosen cav FIG. 3 is in its functional position in a top view eleva
ity. tion and in this layout, the simulated object mounted on
Having set the initial phase of simulation, the remain foam rubber pad 18 inside the cavity 15 can be seen by
der of the steps to make the apparatus functional is the the trainee through the plastic panel 17 under indirect
placement of the adjustable paired mirrors located on 45 binocular vision applying the Two Mirror Concept as
top of the simulator, each attached to the far end of the shown in FIG. 6 while both eyes 32 of the trainee are
top side with their re?ecting surfaces facing each other perceived as integral part of the indirect binocular
whereby said mirrors acting in unison affords the sur viewing process.
geon an indirect binocular way of viewing the activities In FIGS. 4 is a top and 4a is a side elevation view of
in the cavity through the transparent PLEXIGLAS plastic panel 17. FIGS. 5 and 5a are similarly illustrated
panel. In a hospital setting where the Endoscope with the exception that each plastic panel has multiple
Video-Monitor System is available for practice exer pre-established apertures 22 shown best in FIG. 9, has
cise, the surgeon can use this indirect binocular visual the apertures 22 at different locations and numbers spe
system on the simulator of the present invention in lieu ci?c for individual practice procedures. -
of the Two Mirror Concept. 55 The plastic panel 17 is provided with multiple aper
The simulator of the present invention can improve tures 22 shown in FIG. 9. The apertures 22 are covered
the surgeon’s skill on eye-hand coordination and devel with a resilient pressure sensitive circular foam rubber
ops his manual dexterity by performing practice simula plates 19 and at the center of these plates 19 are small
tion on the Hook-Loop Fastener Tape Set, whereby the openings 20 through which the trocar 24 and instru
individual user manipulates the instruments from out 60 ments 31 are inserted during practice procedure. An
side the cavity while viewing the inside activities other smaller circular pressure sensitive plate 21 covers
through the transparent and clear PLEXIGLAS panel the aperture 22 and attached to the under surface of
under indirect binocular vision of the Two Mirror Con plate 19, thus reinforcing the holding strength of plate
cept, hence this practice simulation is performed in an 19 against the in and out movement of the trocars 24.
environment resembling true to life operative condi 65 The plastic panel 17 of simulator 1 simulates the
tions. human body wall. The resiliency provided by the plates
Since certain changes may be made in the above 19 and 21 in FIG. 9 observed when the trocar 24 pene
apparatus without departing from the scope of the in trates the plates 19 and 21 to gain entry into the cavity