ORIGINAL ARTICLE EXPERIMENTAL/SPECIAL TOPICS

Determination of Lower Limb Microvasculature by IntrafemoralArterial Injection Using Computed Tomography-AssistedAngiography

Jingying Nie • Laijin Lu • Xu Gong •

Junjie Nie • Qi Li • Ming Sun

Received: 10 February 2012 / Accepted: 9 July 2012 / Published online: 5 September 2012

� Springer Science+Business Media, LLC and International Society of Aesthetic Plastic Surgery 2012

Abstract

Background Computed tomography-assisted angiography

(CTA) for lower limb vasculature can identify perforators only

as small as 1 mm in diameter. The technique does not clearly

show the microvascularity in subdermal layers of the skin. This

study investigated a novel method of CTA using intrafemoral

injection of contrast medium instead of intravenous injection

to display the vascular anatomy of small perforators with a

diameter less than 1 mm in the lower extremities of rabbits.

Methods Posterior thigh perforator surgery was per-

formed for 15 New Zealand rabbits weighing 2.5 to 3.5 kg.

Five rabbits underwent anatomic dissection to determine

the vascular anatomy of the posterior thigh perforator and

its location relative to adjacent structures. Of the remaining

10 rabbits, 5 were subjected to CTA scanning after injec-

tion of iodine contrast through a microcatheter inserted into

the femoral artery, and 5 were subjected to CTA scanning

through venous injection of contrast media. The latter

group was designated as the control group (10 extremities).

Images were viewed using a dedicated workstation. Post-

operative outcomes and complications were monitored for

7 days after the procedure.

Results All the CTA images of intraartery administration

clearly showed that the posterior thigh perforators

originated from the popliteal artery. Injection of contrast

agent through the femoral artery improved resolution of the

CTA, enabling visualization of perforator arteries with

diameters in the range of 0.3 to 0.4 mm. The images of the

control group indicated the course of the perforator in the

muscle of only six legs. The images of the remaining four

legs did not display the perforator. The CTA-treated ani-

mals recovered without any complications. The anatomic

dissection matched the CTA mapping.

Conclusions Computed tomography-assisted angiogra-

phy using intraarterial injection of contrast media enables

visualization of vessels smaller than 1 mm in diameter.

The described animal model also showed the presence of

vascular branches in the subdermis. This imaging tech-

nique may help in the preoperative design of perforator

flaps for use in clinical practice.

Level of Evidence III This journal requires that authors

assign a level of evidence to each article. For a full

description of these Evidence-Based Medicine ratings,

please refer to the Table of Contents or the online

Instructions to Authors www.springer.com/00266.

Keywords Computed tomography angiography �Femoral artery injection � Perforator flaps

For humans, perforator flap surgery is widely used by

surgeons to provide an adequate blood supply to recon-

structed tissues. The procedure has been used with success

to reduce donor-site morbidity and functional loss.

Despite advances in the use of perforator flaps, surgical

reconstruction still is associated with occasional cases of

incomplete revascularization due to poor preoperative

design. These events result in severe necrosis and life-

threatening immune responses, which can affect the

J. Nie � L. Lu (&) � X. Gong

Department of Hand Surgery, First Affiliated Hospital of Jilin

University, Changchun 130021, China

e-mail: Lljl122@126.com

J. Nie

Department of Plastic Surgery, The People’s Hospital, Jilin,

China

J. Nie � Q. Li � M. Sun

The People’s Hospital, Jilin, China

123

Aesth Plast Surg (2012) 36:1376–1381

DOI 10.1007/s00266-012-9965-3

patient’s quality of life or even necessitate emergency

amputation. Surgeons, therefore, face a critical challenge in

determining how to carry out a detailed preoperative

evaluation of individual perforator vessels so as to optimize

flap survival.

Findings have shown three-dimensional (3D) computed

tomography-assisted angiography (CTA) techniques to be

highly sensitive and specific methods for preoperative

evaluation of perforators in patients undergoing plastic

surgery [1–6]. However, this standard procedure cannot

clearly display vessels smaller than 1 mm in diameter [1, 7].

The New Zealand rabbit (Oryctolagus cuniculus) is an

established model for studying human vascular anatomy

[8] The vessel diameters are markedly larger in rabbits than

in mice, allowing the femoral artery to be cannulated more

easily. In addition, the posterior thigh perforator (PTP) in

mice is described as having a small diameter [9–11].

Therefore, we chose the rabbit to investigate whether an

improved method of CTA could be identified that enabled

small vessels to be visualized.

Materials and Methods

Animals and Study Design

For this study, 15 rabbits (6 males and 9 females) weighing

2.5 to 3.5 kg were obtained from the Experimental Animal

Center of Jilin University. The animals were randomly

divided into three groups of five rabbits each: the traditional

dissection (sacrificial) group, the intrafemoral contrast

media injection (experimental) group, and the intravenously

injected contrast media (control) group.

The animals were fasted and denied water for 12 h before the

CTA procedures. On the morning of surgery, the rabbits were

anesthetized using intravenous (IV) diazepam (1 mg/kg), with

supplementary doses administered as needed. The operative

fields were shaved using an electric shaver.

After surgery, the rabbits were housed in separate cages

under standard environmental conditions and fed standard

pellet diets and tap water ad libitum. No prophylactic

antibiotics were administered. The animals were evaluated

daily for 7 days postoperatively by visual observation, and

white blood cell (WBC) count, behavior, hematoma,

wound healing, inflammation, and suture loss were recor-

ded. All surgical procedures were performed under aseptic

conditions. Sutures were removed on day 7.

Anatomic Dissection: Traditional Dissection Group

Anatomic dissection was performed under loupe magnifi-

cation for five rabbits killed with an overdose of inhaled

ether to confirm the accuracy of PTP vasculature using

CTA. Bilateral posterior thigh dissections were undertaken

to determine the vascular origin of the PTP and its rela-

tionship with the posterior thigh skin.

A 2.5-cm incision was made below the groin, after

which the femoral artery and its continuation as the pop-

liteal artery were exposed and isolated. The caudal femoral

artery was identified as the largest branch of the popliteal

artery and observed to supply the biceps femoris muscle

via two branches: one going to the muscles and the other

going to the popliteal fat pad. The branch to the biceps

femoris muscle supplied the posterior thigh skin via its

profunda femoris musculocutaneous perforator (PTP). The

branch to the fat pad penetrated the fat pad, with one or two

perforators supplying the popliteal fossa (Fig. 1).

Intrafemoral Artery Contrast Medium: Experimental

Group

Three-dimensional CTA was performed to visualize the

morphology of PTP in five rabbits by injection of contrast

medium directly into the intrafemoral artery. After anes-

thetization, a 2.5-cm incision was made below the groin,

after which the femoral artery was isolated and cannulated

using a 22-gauge IV catheter. A Progreat microcatheter

(Terumo Corp., Tokyo, Japan) filled with heparin saline

(10 U/mL) was introduced into the common iliac artery

through the IV catheter (Fig. 2). Iopromide iodinated

contrast material (Iopromide Injection 370; Bayer Schering

Pharma, Guangzhou, China) was injected directly into the

femoral artery through the microcatheter using a Nemoto

Precision Pump (A-60; Kyorindo Co. Ltd., Tokyo, Japan).

A split injection of two doses at different rates was

administered consecutively. The first dose was 5 mL at

1.2 mL/s, and the second dose was 4 mL at 0.6 mL/s.

A 16-channel multidetector computed tomography (CT)

scanner (16 Somatom Sensation; Siemens, Munich, Ger-

many) was used for craniocaudal scanning. The imaging

parameters were as follows: 120 kVp, 180 mA, 0.42-s

Fig. 1 Anatomy dissection showing the musculacutaneous perforator

(green arrow) and the perforators originating from the popliteal fat

pad (yellow arrow)

Aesth Plast Surg (2012) 36:1376–1381 1377

123

gantry rotation time, 0.72-mm beam width, 0.7 beam pitch,

16 9 0.75 collimation, 512 9 512 matrix, 0.75-mm

reconstruction interval, thickness at 0.5-mm intervals, and

4-s scan delay time.

Automated reconstruction images were obtained by a

CT technologist and processed at a dedicated workstation

(Wizard 4.2; Siemens). All images were recreated using

maximum-intensity projection (MIP) or the volume-ren-

dering technique (VRT).

Intravenous Contrast Media: Control Group

In the control group (n = 5, 10 legs), contrast media was

administered IV at a rate of 1.2 mL/s into the ear vein via a

22-gauge needle using the Nemoto Precision Pump, as

described earlier. A single arterial-phase protocol was

used. The imaging parameters were as follows: 18-s scan

delay time and other parameters the same as described

earlier. However, the volume of the contrast media was

administrated similar to the methods used for the

experimental group, but the PTP was not displayed. The

volume of the contrast media was increased to 14 mL.

Adjustment of the contrast media volume to 14 mL max-

imized the arterial filling capacity of the PTP.

Postoperative Assessments

Visual Observation

The animals were monitored daily for behavior, hematoma,

inflammation, wound dehiscence, skin swelling, and suture

loss. Recovery of function was determined by improve-

ment of scores using the Tarlov scale [12], which is a

commonly used method for assessing animal hind legs

function. This method divided hind leg function into five

grades: grade 1 (no voluntary movement), grade 2 (mini-

mal voluntary hind limb movements but inability to stand),

grade 3 (ability to stand but not walk), grade 4 (ability to

walk with spasticity or incoordination of the hind limbs),

and grade 5 (ability to walk normally).

WBC Analysis

The venous blood of the marginal ear vein was collected to

observe the WBC count (COULTER LH 750 Hematology

Analyzer; Beckman Coulter, Inc., Miami, FL, USA) before

the cannulation procedure and then 1, 3, 5, and 7 days

postoperatively.

Results

Experimental Group

The 3D studies with contrast media injected directly into

the intrafemoral artery showed that the PTP, which origi-

nated from the caudal femoral artery also supplied the skin

of the posterior thigh (Fig. 3a, b). However, the

Fig. 2 Schematic representation of the femoral artery cannulation.

(1) Common iliac artery. (2) Iliac artery. (3) Inguinal ligament. (4)

Deep femoral artery. (5) Microcatheter. (6) Nemoto Precision Pump.

(7) Femoral artery. (8) Popliteal artery

Fig. 3 Three-dimensional computed tomography-assisted angiogra-

phy (CTA). a Maximum intensity projections and b multiplanar

reconstruction of the thigh in the experimental group showing the

musculocutaneous perforator (red arrow) originating from the biceps

femoris muscle and the vascular branches in the subdermis

1378 Aesth Plast Surg (2012) 36:1376–1381

123

adipocutaneous perforator was not clearly displayed. The

iliac crest vessels originating from the deep iliac circumflex

artery were shown to supply the iliac crest bone (Fig. 4).

The CTA images also clearly displayed an unbroken

connecting network of vessels and their microvascular

branches (Fig. 5). The femoral artery, a continuation of the

external iliac artery, was found to be the origin of branches

of smaller vessels in the thigh. Proximally, the artery

branched into the deep femoral artery and to subvessels of

the muscle tissues. The popliteal artery, a continuation of

the femoral artery, was shown to continue distally along

the posterior tibial artery. The caudal femoral artery was

identified as the largest branch of the popliteal artery, and

the PTP was the terminal branch of the caudal femoral

artery, as described earlier. The cutaneous perforators of

the posterior thigh and the cutaneous arteries of the waist

were shown to anastomose directly with one another.

Control Group

When the contrast dose was 9 mL in the control group,

matching the dose given to the experimental group, the

PTP was not displayed on the screen. When the dose was

significantly increased to 19 mL, the origin of the PTP and

the course in the muscle were vaguely displayed in six legs

(60% imaging), the site of deep fascia piercing not shown

(Fig. 6). The vessels to the iliac crest were not displayed.

The connecting network of vessels in the lower extremity

also were not displayed.

In comparison, the anatomic dissection also showed that

the origin of the popliteal artery and its course were

identical to those observed by the 3D CTA. The caudal

femoral artery, which was the distal branch of the popliteal

artery, proved to be the origin of two terminal branches.

The one branch arose from the biceps femoris muscle and

Fig. 4 Three-dimensional computed tomography-assisted angiogra-

phy (CTA) showing a maximum-intensity projection. The microves-

sel (white arrow) originating from the deep iliac circumflex artery

(black arrow) and emerging into the iliac crest (IC) is shown

Fig. 5 Volume-rendering reconstruction from three-dimensional

computed tomography-assisted angiography (CTA). The femoral

artery, branches, and posterior thigh perforator (arrow) originating

from the caudal femoral artery are shown. The rich vascular

communication between the subvessels and between the deep and

superficial vessels is apparent. (1) Branch to the biceps femoris

muscle. (2) Sural artery. (3) Saphenous artery. (4) Cutaneous artery of

the waist. (5) Femoral artery. (6) Caudal femoral artery. (7) Posterior

thigh perforator and direct anastomoses with 4

Fig. 6 Three-dimensional computed tomography-assisted angiogra-

phy (CTA). Maximum-intensity projections (above) and multiplanar

reconstruction of the thigh (below) in the control group show the

musculocutaneous perforator (yellow arrow) in one leg. The muscu-

locutaneous perforator in the other leg was not displayed

Aesth Plast Surg (2012) 36:1376–1381 1379

123

supplied the PTS. The arterial diameter of this branch was

0.3 to 0.4 mm, and the vein diameter was 0.4 to 0.5 mm.

The other branch arose from the popliteal fat pad and

supplied the popliteal fossa. The arterial diameter of this

second branch was 0.2 to 0.3 mm, and its vein diameter

was 0.3 to 0.4 mm.

Postoperative Findings

The healing process was similar for all 10 animals sub-

jected to surgery (Table 1) There were no cases of

thrombosis or necrosis in the manipulated lower extremity.

The WBC count was 10.4 ± 1.0 9 109/L before the sur-

gery procedure. The inflammatory reaction in the experi-

mental group was slight after the surgery procedure,

became obvious at 3 to 5 days, and returned to normal in

7 days. The WBC count was 11.8 ± 1.3 9 109/L on day 1,

12.5 ± 1.0 9 109/L on day 3, 12.0 ± 1.1 9 109/L on day

5, 10.8 ± 0.8 9 109/L on day 7.

Discussion

Although perforator flaps are widely used in plastic and

reconstructive surgery, the anatomy of the perforators often

is poorly understood. Several workers [13–15] have con-

ducted gross anatomic studies and have systematically

described the origin of cutaneous blood vessels and their

networks on a 2D plane.

The application of 3D and 4D CTA techniques provides

a new approach for anatomic studies of perforator flaps

[16–21]. These techniques not only display the quantity,

location, diameter, and area of vascular supply for a par-

ticular perforator vessel but also enable evaluation of the

connections between the vasculature and the surrounding

tissues such as adjacent bone, muscles, nerves, and

neighboring perforators on the 3D plane.

Findings have shown that the perfusion at the distal end

of the skin flap is dependent on interperforator flow from

linking vessels and indirect subdermal plexi [18, 21]. This

explains how a single fine perforator blood vessel can

provide a sufficient blood supply to the large surface area

of a perforator flap.

Computed tomography-assisted angiography using tis-

sue samples provides enough information about perforator

flap vasculature. Data obtained from cadaver studies are

affected by various factors including the time of death, the

particle size of the injected materials, the concentrations of

the prepared gel, the injection environment, the injection

method, and the blood supply area. Hence, blood vessel

diameters obtained from cadavers are inconsistent with

observations from live patients [18, 20].

Preoperative evaluations of both the location and the

quantification of the target perforator vessels are necessary

to improve graft survival and reduce the risk of compli-

cations after perforator flap surgery in clinical practice

[1–6]. Conventional CTA is a more accurate procedure

than Doppler ultrasound due to the variable and diverse

characteristics of the perforators. However, conventional

CTA using IV injection of the contrast medium can iden-

tify perforators no smaller than 1 mm in diameter.

In our study, we compared conventional CTA using IV

injection of contrast media and CTA using injection of

contrast media directly through the femoral artery using a

microcatheter. This direct microinvasive procedure signif-

icantly improved the resolution of the image, enabling

observation of perforators 0.3 to 0.4 mm in diameter.

However, this microvasculature cannot be shown clearly or

definitely by conventional CTA with IV injection of nor-

mally accepted doses of contrast media. Despite a signifi-

cantly increased dose (19 mL) of contrast media, only 60%

of the PTP was vaguely displayed.

On the other hand, the injection of the contrast agent

through the femoral artery required only a small volume

(8–10 mL) of medium. The nephrotoxic effects of iodin-

ated contrast agent are well acknowledged, and an increase

in dose may further reduce the renal function in patients

with impaired renal function (e.g., diabetes patients and

renal failure patients) [22–24]. Reduction of the contrast

agent volume would minimize damage to renal function.

Table 1 Postoperative observation of the animals subjected to surgery (n = 10)

Day Behaviora Hematoma WBC count (9109/L) Wound dehiscence Skin swelling Suture loss

1 Grade 4 No 11.8 ± 1.3 No Obvious swelling No

2 Grade 4 No No data No Mild swelling No

3 Grade 5 No 12.5 ± 1.0 No Slight swelling No

4 Grade 5 No No data No No swelling No

5 Grade 5 No 12.0 ± 1.1 No No swelling No

6 Grade 5 No No data No No swelling No

7 10.8 ± 0.8

a Tarlov scale score

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The improved high-resolution imaging of our CTA-

based method clearly displayed the vascular structure of

the lower limb and the anatomy found with previous

descriptions of the vascular anatomic structures, adding

validity to the accuracy of our method [9–11, 25]. In

addition, no postoperative complications were observed in

the experimental animals. The inflammatory reaction was

minimal. No significant differences in WBC counts

between pre- and postoperative reports were observed.

The location of the rabbit femoral artery is equivalent to

that in humans in that the perforators of the lower extremity

originate from the femoral artery in both cases. Although

rabbits have looser and thinner skin than humans and lack

subcutaneous adipose tissue [26], the findings suggest that

the new approach may represent a novel small animal

experimental system that can support the use of this CTA

technique in human clinical practice.

In light of continuing advances in contrast agents and

microsurgical techniques, a new method of CTA will

increasingly be required to identify the microvascular

anatomy of thin perforator flaps. The new technique also

may help to assess the extent of vascular injury and skin

contusion in trauma patients and to identify new perforator

flap techniques that will achieve the ideals of structural,

functional, and aesthetic surgical reconstruction.

Acknowledgment The animals in this study were approved by

institutional review board and the Animal Care and Use Committee of

the First Affiliated Hospital of Jilin University (SCXK-[Ji]

2008-0004).

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