Keywords
SCIP flap - cadaveric study - perforators - superficial circumflex iliac artery -
anatomic variations
Introduction
Reconstruction of large composite soft tissue defects is currently done by free tissue
transfers. The superficial circumflex iliac artery perforator flap (SCIP flap) is
an evolution of the conventional free groin flap.[1] The groin flap is based on the superficial circumflex iliac artery (SCIA). It was
first described by McGregor and Jackson in 1972. The groin flap became popular due
to the concealment of the donor site scar and availability of a large cutaneous flap.
But recently, to overcome the shortcomings of the groin flap (such as arterial anatomical
variation, a short pedicle, and the bulkiness of the flap), new flaps are being studied
and their use is being researched. The development of perforator flaps (PFs) has enabled
the use of thinner flaps and progress in imaging provides a reliable identification
of vessels that supply the flaps. The PFs based on the SCIA have been described for
local or distant coverage of wounds.
With the recent development of PFs such as SCIP flaps, the major pedicle vessels of
fasciocutaneous flaps could be left in place at the donor site. Instead, the flap
can be harvested based on the branches of the major pedicle, thus minimizing donor
site morbidity and preserving reliable blood supply to the flap.[2]
The use of SCIP flap has gradually increased in the reconstruction of small to medium
sized defects in the extremities. Mostly, the SCIP flap is perfused only by the superficial
branch of SCIA. But the deep branch of SCIA is included in the flap when a large flap
is required for coverage or when one of the following anatomical structures perfused
by the deep branch is elevated with the skin paddle: the sartorius muscle, the iliac
bone, and the lateral femoral cutaneous nerve.[3]
The SCIA arises from the femoral artery. It is the smallest superficial branch of
the femoral artery and originates very close to the superficial inferior epigastric
artery (SIEA). The average length of SCIA is 2 cm (range: 1.5–3 cm) and the average
diameter is 1.5 mm (range: 0.8–2 mm).[4]
The SCIA arises about 3 cm below the inguinal ligament from the femoral artery and
runs laterally. It may have a superficial and/or deep branch. The superficial branch,
when present, runs superolaterally over the sartorius fascia, giving few perforators,
while the deep branch runs beneath the sartorius fascia, penetrating at its lateral
border to give perforators in the anterolateral groin. It penetrates the deep fascia
at the lateral border of the sartorius muscle and then enters the suprafascial layer.
This cadaveric study aimed to determine the diameter, location, and reliability of
perforators arising from the SCIA and to describe the existence and the anatomical
location of its branches. We aim to explore the anatomical variations, if any, of
the SCIA perforators in a South Indian population to assess if these findings could
improve the accuracy of surface markings for the SCIP flap in individuals with similar
anthropometric characteristics.
Materials and Methods
This was an observational study which was conducted after obtaining institutional
committee clearance [IEC Ref No: RC/2020/84]. Data were collected between October
2020 and December 2021. Cadavers satisfying the inclusion criteria were used for the
study. Twenty cadavers dissected bilaterally were analyzed. Twenty cadavers with no
scars in the groin region were included in the study.
The following parameters were studied:
-
Number of perforators identified from SCIA.
-
Origin of SCIA.
-
Diameter of perforators.
-
Medial and lateral perforator details.
-
Distance of each perforator from anterior superior iliac spine (ASIS).
-
Distance of each perforator from pubic tubercle (PT).
-
Distance of each perforator from femoral artery.
-
Distance between ASIS and PT, inter-ASIS and inter-PT distance.
-
Relationship of perforator to mid-clavicular line (MCL).
-
Course of lateral perforator—direct cutaneous or intramuscular.
Procedure Details
Twenty cadavers were dissected and the SCIP flap was raised bilaterally. The ASIS,
the PT, and the MCL were used as skin surface landmarks ([Fig. 1]). The SCIA typically originates 2.5 cm below the midpoint of the inguinal ligament
and then runs parallel to it. Dissection was done from lateral to medial direction
and proceeded from the inferolateral part of the groin until the perforators were
identified ([Fig. 2]). Superomedial incision was committed, and careful dissection was done to identify
perforators from other vessels like SIEA or superficial external pudendal artery and
to locate the veins ([Figs. 3] and [4]). The anatomic dimensions of the perforators were noted and the parameters mentioned
above were recorded using a digital Vernier calliper with a precision of 0.01 mm.
Fig. 1 Markings of the bony landmarks. A, surface marking of SCIA origin; ASIS, anterosuperior
iliac spine; PT, pubic tubercle.
Fig. 2 Raising the SCIP flap from lateral to medial direction. SCIP, superficial circumflex
iliac artery perforator.
Fig. 3 Image showing the (A) SCIA originating from the superficial femoral artery, (B) the
medial perforator of the SCIA, (C) the lateral perforator of the SCIA, (D) the superficial
circumflex iliac vein from the greater saphenous vein, (E) superficial femoral artery,
and (F) the femoral vein. SCIA, superficial circumflex iliac artery.
Fig. 4 Bilateral SCIP flaps raised in the cadaver. SCIP, superficial circumflex iliac artery
perforator.
The data were entered in Microsoft Excel and statistically analyzed using the SPSS
software version 20.0. Descriptive statistics was used to analyze the result. For
categorical variables, frequencies and percentages were applied. For the continuous
variables, mean and standard deviations were calculated. As the study did not involve
living participants, waiver of consent was obtained from the ethical committee.
Results
Out of the 40 cadavers dissected, one perforator was noted in 12/40 cases and both
perforators were present in 28/40 cases. Among these, medial perforators were present
in 36/40 cases and lateral perforators in 32/40 cases ([Fig. 5]).
Fig. 5 Number of medial and lateral perforators.
The presence or absence of the perforators varied. The medial and lateral perforators
were both present in most cases (28/40). In some, only the medial perforators were
noted (8/40), whereas in others only the lateral perforator was present (4/40; [Figs. 6] and [7]).
Fig. 6 (A) Example of the anatomic variations: presence of both the perforators (marked by
the red and blue dots) on the right side; presence of only the lateral perforator
on the left side. (B) Dissected cadaver showing the SCIA and the lateral perforator and absent medial
perforator. SCIA, superficial circumflex iliac artery.
Fig. 7 Example of an anatomic variation. (A) Left side of a cadaveric dissection showing the presence of only the medial perforator
(blue pin). (B) Cadaveric dissection showing only the medial perforator (blue dot), SCIA, and absence
of the lateral perforator. SCIA, superficial circumflex iliac artery.
The origin of the SCIA noted in our study was from either the superficial femoral
artery (SFA) or the profunda femoris. The majority of the SCIA originated from the
SFA (n = 38, 95%). Only in one cadaver the origin of the SCIA was from the profunda femoris
(n = 2, 5%).
The mean diameter of the SCIA was observed to be 0.99 ± 0.51 mm and the mean pedicle
length of the SCIA was 2.97 ± 1.46 cm ([Table 1]).
Table 1
Dimensions of SCIA and the perforators
|
SCIA
|
Medial perforator
|
Lateral perforator
|
|
Size (in mm)
|
0.99 ± 0.51
|
0.63 ± 0.42
|
0.55 ± 0.36
|
|
Length (in cm)
|
2.97 ± 1.46
|
3.03 ± 1.54
|
4.31 ± 1.84
|
Abbreviation: SCIA, superficial circumflex iliac artery.
The mean diameter of the medial perforator was 0.63 mm and of the lateral perforator
was 0.55 mm, with a standard deviation of 0.42 and 0.36 mm, respectively. The mean
length of the medial perforator is 3.03 cm and of the lateral perforator is 4.31 cm,
with a standard deviation of 1.54 and 1.84 cm, respectively ([Table 1]).
The diameter of the perforators were compared when only one of the perforators was
absent or when both the perforators were present. The average diameter of the medial
perforator when the lateral perforator was absent was 0.55 mm and its average diameter
was 0.64 mm when both the perforators were present. The average diameter of the lateral
perforator when the medial perforator was absent was 0.41 mm and its average diameter
was 0.57 mm when both the perforators were present.
The distance of the medial and lateral perforators from bony landmarks was noted and
analyzed. The mean distance from each bony landmark was recorded. The medial perforator
was 5.63 cm lateral and 1.66 cm superior to the PT and 5.37 cm medial and 5.99 cm
inferior to the ASIS. The lateral perforator was at a mean distance of 7.97 cm lateral
and 1.95 cm superior to the PT, and 2.86 cm medial and 4.11 cm inferior to the ASIS
([Table 2]).
Table 2
Distance of perforators from bony landmarks
|
Distance (cm),
mean ± SD
|
Medial perforator
|
Lateral perforator
|
|
Lateral to PT
|
5.63 ± 1.56
|
7.97 ± 1.95
|
|
Superior to PT
|
1.66 ± 1.34
|
2.73 ± 1.46
|
|
Medial to ASIS
|
5.37 ± 1.53
|
2.86 ± 1.69
|
|
Inferior to ASIS
|
5.99 ± 2.08
|
4.11 ± 1.67
|
Abbreviations: ASIS, anterior superior iliac spine; PT, pubic tubercle; SD, standard
deviation.
There are two types of travel of the medial perforator within the flap—direct anchorage
after it arises from the SCIA and the other travels for some distance before entering
the flap. In our study, we noted that 55.5% (n = 20/36) of the medial perforators showed axial pattern travel and 44.46% (n = 16/36) showed direct cutaneous pattern of travel.
Among the 40 dissections done, lateral perforator was found in 32 cases. The lateral
perforator was found to be giving muscular branches to the sartorius in n = 27 (84%) cases. No muscular branches were noted in n = 5 (16%) cases.
The relationship of the medial and lateral perforators in relation to the MCL was
observed and noted. It was seen that 22 out of the 36 medial perforators (61.11%)
were present on the MCL, 11 (30.56%) were medial only, and 3 (8.33%) were lateral
to the MCL ([Fig. 8]).
Fig. 8 Number of medial perforators (M.P) and lateral perforators (L.P) located medial to,
lateral to, or on the mid-clavicular line (MCL).
In total, 11 out of the 32 (34.38%) lateral perforators were on the MCL, 3/32 (9.38%)
were medial, and 18/32 (56.25%) were lateral to the MCL.
Excluding the perforators that were lying on the MCL, the mean distance of the medial
perforator was 3.21 ± 1.35 cm medial to MCL and that of the lateral perforators was
2.26 ± 1.87 cm lateral to it ([Fig. 9]).
Fig. 9 Distance of the medial perforator (M.P) and lateral perforator (L.P) from the mid-clavicular
line (MCL).
The mean distance between the PT and the ASIS is 13.41 cm (standard deviation: 1.24 cm).
The mean inter-ASIS distance and inter-PT distance are 25.64 and 8.11 cm, respectively
(standard deviation: 2.56 and 1.38 cm).
Discussion
Koshima et al observed that a large groin flap can be raised based on a single, dominant
perforator from the deep branch of SCIA.[5] This study aimed to observe the anatomical landmarks of the medial and lateral perforators
of the SCIA system in the groin area in the Indian population. Given the lack of data
on the SCIA perforators in the Indian population, our study sought to: (1) determine
the existence and anatomical variations of perforators arising from the SCIA and its
accompanying veins, and (2) describe these perforators in relation to the ASIS and
PT.
Notably, data on the location and branching patterns of SCIA perforators in the Indian
population have been previously unavailable. Therefore, this study helps fill a knowledge
gap in the existing literature. Among the 40 dissections conducted in our study, either
medial or lateral perforators were consistently present. The medial perforator was
present in 36 out of 40 cases, while the lateral perforator was present in 32 out
of 40. In 28 dissections, both medial and lateral perforators were identified, whereas
only the medial perforator was present in 8 cases and only the lateral perforator
in 4 cases.
Sinna et al[4] noted in their study that a dominant perforator was always present through the sartorius
muscle. In contrast in our study, the lateral perforator did not pass through the
sartorius muscle in any of the cases. But we noted that the lateral perforator gave
muscular branches in 84% of the cases (27/32). We noted that the mean diameter of
the SCIA was 0.99 cm ± 0.51 mm. The mean length of the SCIA before it branches into
the medial and the lateral perforators was found to be 2.97 ± 1.46 cm. In a study
by Kosba et al,[6] the mean diameter of SCIA was noted to be 1.5 ± 0.7 mm and the mean length of the
pedicle that could be dissected was 3.2 ± 0.8 cm. In another cadaveric study by Sinna
et al,[4] the mean diameter of the SCIA was found to be 1.92 ± 0.6 mm and the mean pedicle
length of the SCIA was 4.8 ± 1.3 cm. The mean diameter of the medial and lateral perforators
in our study was observed to be 0.63 and 0.54 mm, respectively. In a cadaveric study
by Yoshimatsu et al,[3] the diameter of the medial perforator of the SCIA ranged from 0.5 to 1.2 mm with
a mean diameter of 0.9 mm. The diameter of the lateral perforator of the SCIA ranged
from 0.6 to 2.0 mm with a mean diameter of 1.0 mm. In a cadaveric study done by Gandolfi
et al,[7] the mean diameter of the medial perforator was found to be 2.0 ± 0.78 mm and of
the lateral perforator was 2.1 ± 0.62 mm. The calibers of the perforators in the above
study are larger than the calibers noted in our study. One of the reasons for the
difference in calibers is the variation of the body habitus in the population studied.
The other reason is the use of embalming via femoral canulation done to preserve the
cadavers used in our study. In a study done by Gentileschi et al,[8] they observed that the diameter of the medial perforator ranged from 1 to 2 mm,
with a mean of 1.55 ± 0.25 mm. The diameter of the lateral perforator ranged from
0.7 to 1.8 mm, with a mean of 1.33 ± 0.26 mm. The perforators in this study are of
larger caliber compared to the perforator diameters in our study. This is because
our study is a cadaver-based one, whereas the study by Gentileschi et al is a surgical
and radio-anatomical one.[8] In our study, the mean length of the medial and lateral perforator was found to
be 3.03 and 4.31 cm, respectively. In a cadaveric study done by Gandolfi et al,[7] the mean length of the medial and lateral perforator was found to be 1.8 ± 0.6 mm
and 1.43 ± 0.33 mm, respectively. In our study, the origin of the SCIA was found to
be from SFA or from the profunda femoris. In a study by Suh et al,[9] it was found that the SCIA originated from the femoral artery (84.8%). The SCIA
may also arise from the SFA (7.4%), the deep femoral artery (6.7%), and the lateral
circumflex femoral artery (1.1%). This is in contrast to our findings, in which majority
of the SCIA systems originated from the SFA. We noted that the venae comitantes were
present with the SCIA in all the dissections. Most of them were collapsed and hence
the exact measurements of these veins could not be noted. We noted that there were
one to two separate veins along the inferomedial border of the SCIP flap (close to
the PT). These veins drained into the greater saphenous vein or into the femoral vein.
In some of the cadavers, these veins were sizeable with their diameter ranging between
0.94 and 2.75 mm. A study by Sinna et al showed that the venae comitantes was always
smaller (with a mean diameter of 0.73 mm).[4]
The findings in our study are in accordance with the results of previous studies and
add new information about the position and the course of the SCIA and its perforator.
This understanding of the course, diameter, length, and location of the SCIA and its
perforators helps in raising the SCIP flap, which is useful for covering a variety
of soft tissue defects in the body. Finding the exact location of the medial and the
lateral perforators with respect to permanent bony landmarks (PT and ASIS) and having
an idea about their average pedicle length are very useful for preoperative planning
of the SCIP flap.
The clinical applications of the study include enhanced preoperative planning, more
precise flap designing, and reduced operative time. Identifying exact perforator locations
also ensures better flap viability and minimizes surgical complications. This study
contributes to the anatomical knowledge base, aiding in the education and training
of surgeons in flap surgery techniques.
Limitations
-
One limitation of our study is that the analysis was limited to absolute measurements
of the SCIA perforators in relation to fixed bony landmarks, such as the ASIS and
PT. While this approach provided reliable data, the clinical use of the findings may
be increased by expressing perforator locations as ratios or percentages relative
to imaginary anatomical lines, such as the MCL or arcs drawn from standardized reference
points. The study did not incorporate advanced imaging techniques, such as computed
tomography angiography, which could provide a more detailed understanding of the three-dimensional
anatomy and relationships of perforators to imaginary anatomical lines or arcs. Such
methodologies could account for variations in body habitus and improve preoperative
localization in diverse populations.[10] Future studies incorporating imaging modalities, such as computed tomography angiography,
may enable the identification of consistent geometric relationships between perforators
and imaginary lines, which would aid surgical planning.[11]
-
The study was conducted on 20 cadavers, resulting in a sample size of 40 dissections.
While this is sufficient for preliminary observations, the small sample size limits
the generalizability of the findings to the broader South Indian population. Also,
the cadavers used in this study may not uniformly represent the entire South Indian
population. Variations in factors such as age, sex, and body habitus may affect vascular
anatomy but were not analyzed due to the limited demographic information available.
-
The study was performed on embalmed cadavers, where vessel diameters and pedicle lengths
may differ from in vivo conditions due to the effects of embalming and the absence
of blood flow. Also, embalmed veins often collapse or shrink due to absence of blood
flow. As a result, the veins were not consistently visible or measurable in all our
cases. Therefore, the diameter of the veins could not be reliably assessed in this
study. We recommend that future studies utilize fresh cadavers preserved using soft
embalming techniques to maintain vascular integrity, such as Thiel embalming. These
methods are known to better preserve soft tissue and vascular structures, providing
more accurate and reliable anatomical assessments.
Future Directions
To address these limitations, we recommend larger, multicentric studies involving
live imaging techniques and a more diverse sample population. Such studies could explore
geometric relationships between perforators and imaginary anatomical lines, improving
the clinical utility and applicability of findings in flap design.
Conclusion
In conclusion, understanding the location of medial and lateral perforators relative
to permanent bony landmarks (PT and ASIS), along with their average pedicle length,
enhances precision in preoperative planning for raising the SCIP flap. These anatomical
details support the effective utilization of the SCIP flap for reconstructing a variety
of soft tissue defects.
