Keywords
skin - skin surgery - suture training model - suture technique
Introduction
An animal model involves the use of one or more animals to reproduce a disease or
a portion thereof, and when medical or surgical treatment is applied, the evolution
is similar to that of a human. These models have facilitated advances in health research.
Dermatology is a medical-surgical area that requires a solid theoretical foundation,
as well as a considerable amount of adequate, quality practical training.[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
A common practice for medical residents involved in the surgical field is to train
for procedures with animal parts. This allows them to become familiar with the instruments
and surgical material, and also provides them with the necessary experience and ability
to perform on a patient.[9]
[10]
[11]
[12] Currently, many surgical residents still lack adequate training prior to handling
patients.[13]
[14]
Some medical schools use the undergraduate period to conduct introductory courses
on suturing techniques. The effectiveness of this pretraining and of the reinforcement
during surgical rotation courses is uncertain. Studies have reported several forms
of surgical training that include the use of animal anatomical parts or virtual reality
simulators, both with advantages and disadvantages.[2]
[3]
[4]
[5]
[6]
The purpose of the present study was to use a live animal model in a dermatologic
surgical procedures workshop for residents to evaluate its effectiveness. The focus
was primarily on surgical skill and technique.
Material and Methods
A two-day course was designed, entitled “Skills in Dermatologic Surgery”, consisting
of a theoretical and practical program. It was applied to 13 dermatology residents.
The theoretical section included: histology and physiology of the skin, anatomy (with
a focus on the importance of tension lines), the appropriate use of instruments, suture
materials, and procedures/techniques (fusiform incisions, forward flaps, subdermal
suture, and repair of “dog ear” defects). The surgical practice was performed after
the theoretical session at the Microsurgery Training and Research Laboratory of the
Human Anatomy Department of Facultad de Medicina de la Universidad Autonoma de Nuevo
Leon.
The surgical model used included adult Wistar rats of both genders, with a weight
between 200 and 300 g, which had been previously used for other research purposes
or protocols, and were programmed for euthanization. Rats exposed to radioactive or
infectious agents were excluded. Prior to being placed under general anesthesia, all
rats received an intramuscular (IM) dose of 0.15 mg/100 g of diazepam as a muscle
relaxant. The general anesthetic, ketamine, was administered IM at a dose of 7.5 mg/100
g. The combination of a tranquilizer such as diazepam promotes muscle relaxation by
counteracting the hypertonia produced by ketamine as well as producing amnesia. The
evaluation of signs and tests was performed to ensure an adequate anesthetic plane
before starting any procedure. A trichotomy of the ventral region was performed and
the rat was fixed on a base and placed on the operating table of the laboratory.
The surgical instruments used in the course included straight dissecting forceps,
blunt and sharp scissors, needle holders of different sizes, #3 scalpel handle with
a #11 blade, and a cordless monopolar electrocauter. Sterile latex gloves were provided
as well as consumables, such as gauze and swabs. Nylon sutures were used, varying
in sizes between 5/0, 6/0, and 7/0, depending on the exercise, on the region being
worked, and on the techniques used for suturing.
Each of the procedures was subjectively graded by the instructors as bad, good, or
excellent based on technique, speed and result, on the first and second days of the
practice. Time was measured in each of the procedures of the first day and compared
with that of the second day.
The suture skills were graded by three external judges, all surgeons with knowledge
of dermatologic surgery. The allocation of specimens and the surgical team among the
residents was random.
Statistical Analysis
Mean and standard deviation (SD) were calculated for quantitative variables. The Kolmogorov-Smirnov
test was used to check whether the time variable development of the surgical techniques
followed a normal distribution. For significant differences in the surgical time between
each day, the student t-test was applied for dependent samples. The scores obtained by the students in both
times were compared using the Wilcoxon test. All analyses were performed using SPSS
17.0 for Windows (SPSS Inc, Chicago, IL, USA). The significance level of the test
used was p = 0.05 for two-tailed tests and a β1-power = 80%.
Results
A theoretical section was presented at the beginning of the course, and the surgical
practice was performed subsequently. The practice maneuvers began with how to handle
surgical instruments and with suture technique exercises on inert material. The animal
practice was performed on adult Wistar rats.
Dermatology residents (n = 13) of both genders, with a mean age of 26 years (range 23–29), were included.
None had completed a surgical program, but all had performed minor surgical procedures
in the dermatology service.
The exercises consisted of several types of wound closure. Fusiform incisions were
made and closed with separate stitches. The technique consisted of inserting the needle
perpendicular to the skin, crossing the full thickness of the dermis and continuing
on the opposite side of the wound, checking the symmetry, width, and depth of the
stitches,. The edges of the wound remained slightly everted, so that natural traction
of the scar could occur ([Fig. 1]).
Fig. 1 Fusiform incision to join edges with separate stitches.
Similar incisions were done to practice continuous suture, a technique in which a
series of simple suture points were placed in succession and uniform stress was distributed
along the suture line. For the subdermal continuous suture technique, the stitches
were placed successively through the subcutaneous tissue on opposite sides of the
wound, and the knots were tied at the ends of the wound ([Fig. 2]). The reproduction of flaps progress techniques was also possible, with similar
results.
Fig. 2 Subdermal continuous suture stitches are placed through the subcutaneous tissue (arrow).
All 13 residents demonstrated knowledge of the use of surgical instruments and suture
material. The statistical analysis was classified by results at the beginning and
at the end of the course. The evaluation of medical residents was better on the second
day, primarily in senior students. However, all participants demonstrated a statistically
significant improvement both in skills and in procedure performance ([Table 1]).
Table 1
Results of the time taken to complete the exercise test for each surgical technique
during the first and second day of the course
|
n
|
First day
|
Second day
|
t
|
p
|
|
Exercise 1
Instrument use
|
13
|
13.08 ± 1.61
|
9.08 ± 1.32
|
10.198
|
< 0.01
|
|
Exercise 2
Fusiform incision
|
13
|
18.62 ± 2.22
|
15 ± 1.91
|
5.514
|
< 0.01
|
|
Exercise 3
Flap progress
|
13
|
23.31 ± 2.32
|
19.38 ± 2.66
|
6.081
|
< 0.01
|
|
Exercise 4
Subdermal suture
|
13
|
24.00 ± 2.12
|
19.38 ± 3.59
|
4.924
|
< 0.01
|
|
Exercise 5
Dog ears defects
|
13
|
5.92 ± 0.76
|
4.38 ± 0.96
|
5.734
|
< 0.01
|
Abbreviations: t, time; p, statistical significance set a p < 0.05; , mean plus/minus standard deviation.
Discussion
Practical training is essential in any surgical specialty. Surgical simulators are
an established part of training and have been used as part of the objective assessment
of surgical skills for residents and doctors in many institutions.[15]
[16]
Artificial skin models that simulate several diseases have been used. However, they
are expensive or difficult to obtain in third world countries, such as Mexico. Pigskin
has also been used, as it is easy to obtain, inexpensive, and its texture and consistency
are similar to those of human skin. The ideal and most used model is pig leg. However,
because of its cylindrical morphology, it is not suitable for more complex procedures.
Pig heads, however, have demonstrated better results for training exercises involving
grafts, flaps and even dermal fillers, according to Chen et al.[9]
These models have been widely used in basic sutures workshops or can even be modified
for deep cysts models to train medical personnel in these pathologies.[6]
[7]
[8]
[9]
[11]
[12] Porcine models are a suitable option. However, the anatomical parts available are
not always the best for complex procedures because they are inert tissues lacking
the characteristics and the response of live tissue, such as temperature, elasticity,
firmness, texture, and vascularity.
With the technological advances in biomedical sciences, virtual reality devices will
make animals and artificial models obsolete.[5]
[10]
[11]
[13]
[15] However, it will take time and experience for them to be considered the standard
methods for surgical training. Their cost is also an important issue because many
institutions and third-world countries cannot afford to buy and maintain these simulators.
Some institutes have surgery training programs using live pigs, providing an invaluable
tool in teaching cutaneous surgery. These are also used for procedures in other systems,
such as the gastrointestinal (porcine gastric ulcer with active bleeding), to train
residents in superior digestive surgical endoscopies. They are also used in other
modalities, such as dermal application of carbon dioxide (CO2) and other chemical treatments for aesthetic purposes. However, the hypovascularity
of pigskin makes it drier and represents an important difference to human skin.[9]
[17]
[18]
[19]
[20]
Rats and mice have been the most popular model for research, especially in the study
of skin, such as wound repair models, due to its similarities to human tissue and
its proven economical maintaince.[21] The use of rats from previous studies also helps in reducing the cost. Although
some differences exist between mouse skin and human skin, the use of mouse skin for
cutaneous surgery training workshops have been statistically proven to bring benefits
to the surgical training.[8]
A murine model provided an important tool for training 13 dermatology residents. They
demonstrated a greater identification with the surgical material, as well as an improvement
in the most frequently used surgical suturing techniques.
After the workshop, the residents reported that the exercise helped them to gain experience
and confidence in their surgical ability, as well as to perform procedures they did
not wish to perform for the first time on patients.
Conclusions
The model presented in our work uses a live animal, reproducing a similar situation
to that of a surgical procedure on a patient. The practitioner focuses not only on
the design of an incision or on the repair of a defect, but also has de advantage
of the feeling and of the consistency of the skin and of the deep tissues, while practicing
bleeding control and the use of electrocauterization. This is an economic and easily
obtainable model that provides real characteristics and should be considered for conducting
training workshops of surgical skills in dermatology.
