Keywords
radial artery - diameter - vessel thickness - angle of bifurcation - Ethiopia
Introduction
The radial artery is derived from the bifurcation of the brachial artery at the apex
of the cubital fossa. This vessel courses over the lateral aspect of the forearm deep
to the brachioradialis muscle until its midpoint, and then becomes subcutaneous near
the distal forearm. In the distal forearm, the radial artery is located immediately
lateral to the tendon of the flexor carpi radialis and directly anterior to the pronator
quadratus muscle. To get into the hand region, it passes from the wrist joint laterally
through the anatomical snuffbox between the heads of the first dorsal interosseous
muscle. In the forearm and hand area, it gives numerous smaller generations to supply
nearby structures. Along its course, it is accompanied by a similarly named vein,
the radial vein.[1]
The radial artery is smaller than the ulnar artery and is more a continuation of the
brachial artery. Instead of arising as a branch of the brachial artery, it may arise
from the axillary artery or more proximally than usual from the medial side of the
brachial artery and then cross over the brachial artery to enter the forearm. However,
in the routine clinical practice, variations of the radial artery are one of the main
reasons for technical failure.[2] According to one study,[3] variations are most common in the upper limbs, and happen with a frequency of 20%.
This can be observed in most dissection rooms. Radial artery also shows a constant
pattern with only a few variations being described in part of the literature.[4] Unusual arterial variations are frequently noticed, and experience with those variations
may be of much help in the clinical practice, particularly with the expanding use
of upper limb arteries in surgical procedures, such as radial forearm flap, coronary
artery grafting, and in preoperative angiographic studies.[3]
The technique of using the radial artery as a coronary artery bypass graft was introduced
by Carpentier.[5] Two years after the initial series was published in 1973, another paper published
by Carpentier claimed that there was a high risk associated with the procedure, which
led to the abandonment of the use of the technique worldwide. The papers published
in 1992 and 1993 by the French surgeon Christophe Acar[6] reported that after 104 patients underwent a coronary angiography, made 100% revealing
of the radial artery. This resulted in a consensus regarding the need for the renewal
of this technique, since several authors[7] agree that there is no reduction in strength and flow to the forearm due to the
alternative blood supply from anastomoses.
The transradial approach is commonly used for cannulation, coronary angiography, and
bypass graft because it is preferred by clinicians due to its technical ease and less
likelihood of complications.[8] In addition, according to a research conducted by Onorati et al,[9] radial artery graft is not affected by age. According to Sajja et al,[10]
[11] there still is no uniformity regarding the harvest technique.
Transradial catheterization or angioplasty was introduced in the past 10 years as
a treatment for heart attack. The methods are widely accepted due to an alternative
blood supply from the ulnar artery to minimize the frequency of local complications.
The concept is that a tube (catheter) with a tiny balloon at the end is inserted through
the radial artery in the upper limb and directed into the artery that is blocked.
Once it reaches the location of the blockage, the balloon is inflated, flattening
the fatty deposit and opening the artery. Angioplasty uses a special safety device
that catches particles that sometimes dislodge from the side of the artery.[12]
When compared with the transfemoral approach for cardiac catheterization, the transradial
approach has merits because: the dual blood supply limits the potential for limb threatening
ischemia; it is advantageous for patients with severe occlusive aortoiliac disease
and for patients with difficulty in lying down (such as those with back pain and obesity);
the vessels are easily compressible; it has less chance of local nerve injury; the
radial approach allows earlier patient ambulation and will likely cost less; it is
associated with less frequent vascular complication; and, to date, randomized trials
suggest that patients prefer the radial approach.[13]
While harvesting the radial artery for coronary artery bypass graft, the diameter,
the variation and the length of the artery should be taken into consideration. The
small caliber (internal diameter) of the radial artery and the variety of equipment
available for radial artery access, such as needle, wire, and sheath, and the basic
knowledge about the morphology, the variation, the diameter, and the thickness of
the wall of the radial artery are very important for clinical practitioners, especially
for vascular and plastic surgeons, to perform with precision a percutaneous coronary
intervention (PCI) using catheterization. However, evidence on these variables and
parameters are lacking in Ethiopia. Therefore, the present study was conducted to
determine the internal and external diameters, the vessel thickness, and the angle
of bifurcation of the ulnar and radial arteries among adult Ethiopian cadavers.
Materials and Methods
This was a descriptive study involving the dissection of 78 upper limbs (39 right,
39 left) of the cadavers of 18 adult females and 21 adult males in the age range between
25 and 77 years old whose radial arteries and its branches were exposed. The present
study was undertaken in the anatomy laboratories of three different Medical Colleges
in Ethiopia: the College of Medicine and Health Sciences of the Hawassa University,
the College of Medicine and Health Sciences of the Addis Ababa University, and the
College of Health Sciences and Medicine of the Jimma University.
The measurements of the radial artery were taken at its origin from the brachial artery,
at the cubital fossa, and at the wrist joint. All measurements were repeated three
times, and the average was calculated. Prior to the measurement, the upper limb was
carefully dissected to expose the muscles in the area, especially the brachioradialis,
where the initial measurements of the external diameter, of the internal diameter
and of the wall thickness were taken. The dissection continued down over the anterior
aspect of the forearm to expose the distal part of the radial artery where the second
set of measurements of the external diameter, of the internal diameter, and of the
wall thickness was taken.
The level of bifurcation of the brachial artery was also determined regarding the
head of radius. The angle of origin of the radial and ulnar arteries from the brachial
artery was measured at the cubital fossa. An imaginary line drawn along the brachial
artery was used as a reference point to measure the angles. The angle of the radial
artery was measured first, followed by the angle of the ulnar artery ([Fig. 1]).
Fig. 1 A diagram showing the measurement of the angle of bifurcation of the brachial artery
into the radial and ulnar arteries. A - brachial artery; B - median nerve; C - medial
epicondyle; D – protractor; E - radial artery; F - angle of bifurcation.
The procedures used in the measurements were in line with the approved protocols of
the anatomy laboratories of the aforementioned universities. A digital vernier caliper
(Model AD-5765A-150, A&D company,limited, Tokyo, Japan) was used to measure the internal
diameter, the external diameter, and the wall thickness of the arteries. A protractor
was used to measure the angle of bifurcation of the brachial artery into the radial
and ulnar arteries. The vernier caliper is a precise instrument that can be used to
measure with extreme accuracy the internal diameter, the external diameter, and the
wall thickness.[14] The example shown in [Fig. 2] is a digital caliper; the diameters were interpreted from its scale.
Fig. 2 A diagram showing the digital vernier caliper while measuring the external diameter
at the wrist joint.
The data were collected over a period of two consecutive years, as there was a shortage
of cadavers in Ethiopian Medical Schools. All cadavers were considered for the present
study, but those that had anomalies and/or variations were excluded. The data were
entered and analyzed using the Statistical Package for the Social Sciences (SPSS,
SPSS Inc., Chicago, IL, US) software, version 16.0. The means ± standard deviations
(SDs) of the different measurements were computed. We used the paired samples t-test to compare the differences in arterial diameter, in thickness, and in the angle
of bifurcation between the right and left limbs. The independent samples t-test was used to compare the aforementioned parameters between females and males.
A p-value ≤ 0.05 was considered statistically significant.
Results
A total of 39 adult cadavers was studied, of which 21 (53.8%) were male and 18 (46.2%)
were female. The number of limbs studied was 78 (39 right and 39 left limbs). The
age of the cadavers ranged from 25 to 77 years, with a mean ± SD age of 58.05 ± 15.264
years old.
Radial Artery Diameter
The mean ± SD of the external diameter of the right radial artery at the cubital fossa
was 4.40 ± 1.26 mm, while the mean ± SD of the external diameter of the left radial
artery at the cubital fossa was 4.44 ± 1.51 mm. However, this difference was not statistically
significant (t-test [t] [degree of freedom (df) = 38] = -0.33; p = 0.75).
The mean ± SD of the external diameter of the right radial artery at the wrist joint
was 3.24 ± 0.79 mm, while the mean ± SD of the external diameter of the left radial
artery at the wrist was 3.06 ± 0.85 mm. Here again, this difference was not statistically
significant (t [df = 38] = -1.57; p = 0.13).
The mean ± SD of the internal diameter of the right radial artery at the cubital fossa
was 3.79 ± 1.44 mm, while the mean ± SD of the internal diameter of the left radial
artery at the cubital fossa was 3.79 ± 1.78 mm. However, this difference was not statistically
significant (t [df = 38] = -0.06; p = 0.96).
The mean ± SD of the internal diameter of the right radial artery at the wrist joint
was 2.79 ± 1.10 mm, while the mean ± SD of the internal diameter of the left radial
artery at the wrist joint was 2.66 ± 0.94 mm. This difference was not statistically
significant (t [df = 38] = -1.20; p = 0.24). See [Tables 1] and [2].
Table 1
The mean ± standard deviation of the external diameter, internal diameter and wall
thickness of the radial artery taken at the cubital fossa and at the wrist joint of
the right and left sides of the whole sample
|
Radial artery
|
Side
|
Mean ± SD
|
|
External diameter (mm)
|
Internal diameter (mm)
|
Thickness (mm)
|
|
Cubital fossa
|
|
Right
|
4.40 ± 1.26
|
3.79 ± 1.44
|
0.37 ± 0.22
|
|
Left
|
4.44 ± 1.51
|
3.79 ± 1.78
|
0.34 ± 0.23
|
|
Wrist joint
|
|
Right
|
3.24 ± 0.79
|
2.79 ± 1.10
|
0.25 ± 0.22
|
|
Left
|
3.06 ± 0.85
|
2.66 ± 0.94
|
0.28 ± 0.24
|
Abbreviations: SD, Standard deviation; mm, millimeters.
Table 2
T-test for equality of means at 95% confidence interval of the difference in the external
diameter, the internal diameter and the wall thickness between the right and left
limbs
|
Pair
|
Mean difference
|
Standard deviation
|
t-test
|
df
|
p-value
|
|
External diameter of the radial artery at the cubital fossa in mm (right and left)
|
−0.04
|
0.74
|
−0.33
|
38
|
0.75
|
|
Internal diameter of the radial artery at the cubital fossa in mm (right and left)
|
−0.01
|
0.71
|
−0.06
|
38
|
0.96
|
|
Thickness of the radial artery at the cubital fossa in mm (right and left)
|
0.03
|
0.19
|
0.96
|
38
|
0.34
|
|
External diameter of the radial artery at the wrist joint in mm (right and left)
|
0.17
|
0.69
|
1.57
|
38
|
0.12
|
|
Internal diameter of the radial artery at the wrist joint in mm (right and left)
|
0.13
|
0.68
|
1.19
|
38
|
0.24
|
|
Thickness of the radial artery at the wrist joint in mm (right and left
|
−0.03
|
0.23
|
−0.79
|
38
|
0.43
|
Abbreviations: df, degree of freedom; mm, millimeters.
When comparing the diameters between males and females, the mean ± SD of the external
diameter of the right radial artery at the cubital fossa in males was 4.45 ± 1.35,
while in females itwas 4.36 ± 1.18. However, this difference was not statistically
significant (t [df = 37] = 0.22; p = 0.31). Similarly, the mean ± SD of the external diameter of the left radial artery
at the cubital fossa in males was 4.41 ± 1.5 mm, while in females it was 4.49 ± 1.51
mm. Similarly, this difference was not statistically significant (t [df = 37] = -0.16;
p = 0.69).
The mean ± SD of the internal diameter of the right radial artery at the cubital fossa
in males was 3.66 ± 1.65 mm, and, in females, it was 3.93 ± 1.16 mm. This difference
was statistically significant (t [df = 35.73] = -0.59; p = 0.015). Similarly, the mean ± SD of the internal diameter of the left radial artery
at the cubital fossa in males was 3.48 (2.08), while in females it was 4.17 ± 1.29
mm. This difference was statistically significant (t [df = 33.94] = -1.25; p < 0.004).
The mean ± SD of the external diameter of the right radial artery at the wrist joint
in males was 3.36 ± 0.85 mm, and, in females, it was 3.10 ± 0.73, a difference that
was not statistically significance (t [df = 37] = 1.00; p = 0.71). Similarly, the mean ± SD of the external diameter of the left radial artery at the
wrist joint in males was 3.10 ± 0.78 mm, while in females it was 3.01 ± 0.95 mm. This
difference was also not statistically significant (t [df = 37] = 0.35; p = 0.63).
The mean ± SD of the internal diameter of the right radial artery at the wrist joint
in males was 2.83 ± 1.27 mm, while in females it was 2.74 ± 0.65 mm. This difference
was not statistically significant (t [df = 37] = 0.25; p = 0.09). Similarly, the mean ± SD of the internal diameter of the left radial artery
at the wrist joint in males was 2.56 ± 1.06 mm, while in females it was 2.77 ± 0.80
mm. Here again, this difference was not statistically significant (t [df = 37] = -0.68;
p = 0.12). See [Table 3].
Table 3
The mean ± standard deviation of the external diameter, the internal diameter, and
thickness of the radial artery taken at the cubital fossa and at the wrist joint of
male and female cadavers
|
Radial artery
|
Sex
|
Side
|
n
|
Mean ± SD
|
|
External diameter (mm)
|
Internal diameter (mm)
|
Wall thickness (mm)
|
|
Cubital
|
Male
|
Right
|
21
|
4.45 ± 1.35
|
3.66 ± 1.65
|
0.37 ± 0.22
|
|
Female
|
Right
|
18
|
4.36 ± 1.18
|
3.93 ± 1.16
|
0.36 ± 0.21
|
|
Male
|
Left
|
21
|
4.41 ± 1.5
|
3.48 ± 2.08
|
0.29 ± 0.91
|
|
Female
|
Left
|
18
|
4.49 ± 1.51
|
4.17 ± 1.29
|
0.37 ± 0.27
|
|
Wrist joint
|
Male
|
Right
|
21
|
3.36 ± 0.85
|
2.83 ± 1.27
|
0.26 ± 0.21
|
|
Female
|
Right
|
18
|
3.10 ± 0.73
|
2.74 ± 0.65
|
0.25 ± 0.23
|
|
Male
|
Left
|
21
|
3.10 ± 0.78
|
2.56 ± 1.06
|
0.22 ± 0.19
|
|
Female
|
Left
|
18
|
3.01 ± 0.95
|
2.77 ± 0.80
|
0.35 ± 0.28
|
Abbreviations: n, number of cadavers; SD, standard deviation; mm, millimeters.
Radial Artery Thickness
The mean ± SD of the wall thickness of the right radial artery at the cubital fossa
was 0.37 ± 0.22 mm, while the mean ± SD of the wall thickness of the left radial artery
at the cubital fossa was 0.34 ± 0.23 mm. However, the difference in wall thickness
between the right and the left radial arteries was not statistically significant (t
[df = 38] = 0.96; p = 0.34). Similarly, the mean ± SD of the wall thickness of the right radial artery
at the wrist joint was 0.25 ± 0.22 mm, while the mean (SD) of the wall thickness of
the left radial artery at the wrist joint was 0.28 ± 0.24. This difference, however,
was not statistically significant (t [df = 38] = -0.79; p = 0.43). See [Tables 1] and [2].
Comparing males and females, the mean ± SD of the wall thickness of the right radial
artery at the cubital fossa in males was 0.37 ± 0.22 mm, while in females it was 0.36 ± 0.21
mm. This difference was not statistically significant (t [df = 37] = 0.09; p = 0.93) Similarly, the mean ± SD of the wall thickness of the left radial artery
at the cubital fossa for males was 0.29 ± 0.91 mm, while for females it was 0.37 ± 0.27
mm. However, this difference was not statistically significant (t [d f= 37] = -1.07;
p = 0.14). See [Table 3].
The mean ± SD of the wall thickness of the right radial artery at the wrist joint
in males was 0.26 (0.21) mm, and, in females, it was 0.25 (0.23) mm. This difference,
however, was not statistically significant (t [df = 37] = 0.23; p = 0.61). Likewise, the mean ± SD of the wall thickness of the left radial artery
at the wrist joint in males was 0.22 ± 0.19 mm, while in females it was 0.35 ± 0.28
mm. This difference was statistically significant (t [df = 37] = -1.69; p = 0.03). See [Table 3].
Radial Artery Bifurcation Angle
The origin of the right radial artery from the brachial artery at the apex of the
cubital fossa had angles ranging from 21 to 81°, while the origin angle of the left
radial artery ranged from 20 to 85°. The mean ± SD of the angle of bifurcation of
the right radial artery was 39.94° (11.19°). while of the angle of bifurcation of
the left radial artery was 40.25° (11.80°). This difference, however, was not statistically
significant (t [df = 38] = -0.453; p = 0.65). See [Table 4].
Table 4
Angle of the brachial artery at its bifurcation into the radial and ulnar arteries
at the apex of the cubital fossa
|
Side
|
n
|
Range
|
Minimum
|
Maximum
|
Mean
|
SD
|
|
Right angle
|
39
|
60°
|
21°
|
81°
|
39.94°
|
11.20°
|
|
Left angle
|
39
|
65°
|
20°
|
85°
|
40.25°
|
11.80°
|
Abbreviations: n, number of cadavers; SD, standard deviation.
The mean ± SD of the angle of origin of the right radial artery in males was 41.95°
(13.96°), and, in females, it was 37.61° (6.32°). However, this difference was not
statistically significant (t [df = 37] = 1.22; p = 0.31). Similarly, the mean ± SD of the angle of origin of the left radial artery
in males was 42.75° (14.74°), while in females it was 37.33° (6.25°). This difference
was not statistically significant (t [df = 37] = 1.45; p = 0.10). See [Table 5].
Table 5
Angle of bifurcation of the brachial artery into the radial and ulnar arteries at
the apex of the cubital fossa by sex
|
Sex
|
n
|
Side
|
Mean
|
SD
|
|
Male
|
21
|
Right
|
41.95°
|
13.96°
|
|
Female
|
18
|
Right
|
37.61°
|
6.32°
|
|
Male
|
21
|
Left
|
42.75°
|
14.74°
|
|
Female
|
18
|
Left
|
37.33°
|
6.25°
|
Abbreviations: n, number of cadavers; SD, standard deviation.
Discussion
To our knowledge, no previous study has been conducted in Ethiopia regarding the morphology
of the radial artery, particularly diametric studies, because the field of PCI was
introduced very recently in the country. Moreover, we have found that there are less
cadaveric studies directly related to the diametric study of the radial artery. Therefore,
the present cadaveric study is our first step forward to expand our studies on patients
using Doppler ultrasound.
During the early embryonic development and the growth of the upper limb, the variation
of vessels is based on the growth or the regression of the bud plexus. As a result,
any faults in the development process of the bud plexus lead to many variations in
the arterial origins, as well as in the arterial courses. The incidence of vascular
upper limb variations ranges between 9 and 18.5%.[15] The variability of radial artery in origin and course is very common, which may
affect the diagnosis and management procedures, such as surgical interventions. Therefore,
it is valuable for clinicians to know the diameter, the thickness, the angle of origin,
and the variations of the radial artery, because several surgical and invasive interventions
are performed in the cubital and wrist regions. This knowledge may lead to a reduction
in medical mistakes. Therefore, learning the anatomical vascular variations is of
paramount medical significance.
In the present study, the angle of bifurcation of the brachial artery into the radial
and ulnar arteries at the apex of the cubital fossa of the right limb ranges from
21 to 81°, and in the left limb it ranges from 20 to 85°. According to a study on
the cubital fossa by Al-Sowayigh et al,[16] the radial artery usually arises at the level of the neck of radius in 21.7% of
the individuals. However, it may arise either before or after the level of the neck
of radius in 11.7% or in 6%[16] of the individuals respectively. It usually arises after the intercondylar line
in 92%[17] of the individuals, but it may arise before the intercondylar line in 10% of the
individuals.[16] Therefore, the radial artery arises from the brachial or from the axillary artery
before the antecubital fossa, which is referred to as a high origin. According to
another study,[18] the angle of the radial artery regarding the brachial artery ranges between 80 and
300°. This angle was found to be wider in males and on the right side.[18]
In the present cadaveric study, the means of the right and left external diameters
of the radial artery at the cubital fossa were 4.40 mm and 4.44 mm respectively, while
the means of the right and left external diameters of the radial artery at the wrist
joint (1–2 cm proximal to the styloid process of the anterior surface of the radius)
were 3.24 mm and 3.06 mm respectively. This finding shows that the radial artery decreases
in size as it moves from the proximal to the distal part. Our finding is in line with
the findings by Nasr[17] and Waseem et al.[18]
Which showed a mean diameter of 3.1mm and 3.6, respectively, at the wrist joints?
According to the aforementioned article, the external diameter of the radial artery
at the cubital fossa matches with the external diameter of 10-French (Fr) sheaths,
which have an external diameter of 4.0 mm, and an internal diameter of 3.4 mm. However,
this finding is not in line with the finding of a study conducted among patients using
ultrasound Doppler, which showed that the use of guiding catheters ≥ 7 Fr in the radial
artery is feasible in selected patients.[19]
In the present study, the mean of the right internal diameter of the radial artery
at the cubital fossa in males was 3.66 mm, while in females it was 3.93 mm, and the
difference was statistically significant. Similarly, the mean of the left internal
diameter of the radial artery at the cubital fossa in males was 3.48 mm, ande, in
females, it was 4.17 mm, again a statistically significant difference. Since currently
more focus is being given to the distal part of the radial artery for coronary intervention,
we have also measured the diameter of the radial artery at the wrist joint. The results
showed that the mean of the internal diameter of the right radial artery at the wrist
joint (2.79 mm) was not significantly different from the mean of the internal diameter
of the left radial artery (2.66 mm) at the wrist joint. The present study is in line
with the study conducted by Prakash et al[20] in India among a sample of 50 radial arteries of 25 cadavers (20 males and 5 females),
in which the mean ± SD luminal diameter at its termination 2 cm proximal to the styloid
process, just above the wrist joint, was reported to be 2.14 ± 0.28 mm. Our results
are also in line with a Doppler ultrasonographic study of 117 subjects[21] that reported the mean ± SD diameters of the right and left radial arteries to be
2.35 ± 0.49 mm, and 2.29 ± 0.48 mm respectively. Moreover, Pal et al[21] reported a mean ± SD diameter of 2.325 ± 0.4 mm for the radial arteries.
Moreover, in the present study, the mean ± SD of the wall thickness of the right radial
artery at the wrist joint was 0.25 ± 0.22 mm, while the mean ± SD of the wall thickness
of the left radial artery at the wrist joint was 0.28 ± 0.24 mm. This result is a
bit higher than what was reported by a previous study that reported a wall thickness
of 0.15 ± 0.10 mm and of 0.16 ± 0.13 mm for the right and left limbs respectively.[18] In the interpretation of our results, it must be noted that as it was a cadaveric
study, we could not measure confounding factors such as weight, body surface area,
body mass index, arm circumference, and risk factors of cardiovascular diseases. Therefore,
the comparison of the mean diameters, thicknesses and angles of the bifurcations were
unadjusted for the aforementioned confounders. This might have introduced some biases
in our results.
Conclusion
Given the many advantages of the transradial approach for coronary catheterization
and intervention, knowledge of the morphology of the radial arteries in a given population
is of paramount importance for informed decision making. The primary reason is fear
of complications and procedural failure related to the smaller size of the radial
arteries in comparison with that of femoral arteries, the most important parameter
being the internal diameter. From the study of a total of 78 dissected radial artery
specimens (both right- and left-sided; 21 male and 18 female cadavers) and comparing
the present study with previous works, it can be concluded that the diameter of the
radial artery of the Ehiopian population is comparable with that of other populations,
and that its size is adequate for the commonly used 10 Fr radial catheters. Therefore,
the radial artery can be safely considered as a route for transradial coronary interventions
in Ethiopian patients. However, this sample was taken from cadaveric specimens, and
we could not consider confounding factors and the prevalence of anomalies such as
tortuosity, richness in collateral branches, and the length of the radial artery.
Therefore, we recommend further studies, preferably on live subjects. We also recommend
the study of factors possibly associated with variations in the morphology of the
radial arteries.
