A Statistical Study of the Branching of the Human Internal Iliac Artery

Home , Inferior gluteal artery, Internal iliac artery, Internal pudendal artery, Pudendal arteries, Superior gluteal artery

Kurume Medical Journal, 45, 333-340,1998 Original Article

KOH-ICHI YAMAKI, TSUYOSHI SAGA, YOSHIAKI D0l, KATSUMARO AIDA AND MITSUAKI YOSHIZUKA

Department of Anatomy, Kurume University School of Medicine , Kurume 830-0011 and Department of Anatomy, University of Occupational and Environmental Health, School of Medicine , Kitakyushu 807-0804, Japan

Summary: This study is based on the dissections of 645 pelvic halves of Japanese cadavers . The branching of the internal iliac artery was classified according to Adachi's classification (1928) , and the data was compared with previous reports. Type I was predominant in this , as well as, in previous studies. During the course of the present study, some branching forms were different from the types in Adachi's classification. Therefore, this classification was modified into 5 types and 19 groups. Type I-Group 1 was most frequently observed in the modified Adachi's classification, however, the frequency was less than 50% (46.8%). To clarify the basic branching pattern of the original internal iliac artery and to simplify the classification for medical purposes , a new classification system was designed. The superior gluteal, inferior gluteal and internal pudendal arteries were defined as the major branches of the internal iliac artery, and the umbilical artery was excluded from this group. The branching of the internal iliac artery was classified into 4 groups . Almost 80% of the present specimens were included in Group A of the new classification , namely, the internal iliac artery dividing into two major branches, the superior gluteal artery and the common trunk of the inferior gluteal and internal pudendal arteries. This type of branching seemed to be the basic branching pattern for the original internal iliac artery.

Key words human anatomy, internal iliac artery, classification , distribution pattern, statistical study

classification [1] and compared with previous INTRODUCTION studies. A modification of Adachi's classification was The internal iliac artery supplies the pelvic viscera, developed based on previous findings [13] . the pelvic walls, the perineum and the gluteal region. Furthermore, a new classification was proposed It is well established that the parietal and visceral to clarify the basic branching pattern of the original arteries branch from the internal iliac artery in internal iliac artery from embryological and clinical numerous ways. Therefore, an understanding of the points of view. distribution pattern of this artery is especially important in medical practice. For this reason, there have MATERIALS AND METHODS been many studies on the distribution pattern of this artery [1-12]. The data is based on the examination of 645

In the present study, the mode of branching of the pelvic halves (426•‰sides, 219•Šsides, 327 right internal iliac artery in 645 pelvic halves, which were sides and 318 left sides), which were dissected dissected during the gross anatomy courses at during the gross anatomy laboratories at Kurume Kurume University School of Medicine and Fukuoka University School of Medicine and Fukuoka Dental Dental College, was classified according to Adachi's College from 1982 to 1998. They were all adult

Received for publication September 16, 1998 correspondence to: Koh-ichi YAMAKI, M.D., Department of Anatomy, Kurume University School of Medicine , Kurume 830-0011, Japan. T el: 0942-31-7540 Fax: 0942-33-3233 334 YAMAKI ET AL.

Japanese cadavers. The internal iliac artery and its stem which is the second branch. If the bifurcation of major branches were carefully exposed and the superior gluteal and inferior gluteal arteries examined. The umbilical, the superior gluteal, the occurs within the pelvis, it is type ha. If the division inferior gluteal and the internal pudendal arteries occurs outside the pelvis, it is type hb. were considered the principal branches for classi- Type III: All three major branches (the superior fying the mode of branching of the internal iliac artery, according to Adachi [1]. The data was statistically analyzed with the Student t-test, and statistical significance was accepted for comparisons at p < 0.05.

RESULTS AND DISCUSSION

Distribution of the internal iliac artery by Adachi's classification In 1928, Adachi classified the distribution pattern of the internal iliac artery into 5 types with 8 groups (Fig. 1). In this classification, Adachi proposed that the umbilical artery was a continuation of the main stem of the internal iliac artery, and the superior gluteal, the inferior glteal and the internal pudendal arteries were principal branches of the umbilical artery from an embryological point of view. The five types referred to by Adachi are briefly summarized below. Type I: The superior gluteal artery is the first to arise independently from the main stem, and the inferior gluteal and internal pudendal arteries arise from a common trunk that is the second branch. When the trunk divides within the pelvis, it is type Ia. If the division occurs outside the pelvis, it is type lb. Fig. 1. The branching pattern of the internal iliac Type H: The superior and inferior gluteal arteries artery, as classified by Adachi [1]. arise from a common trunk, and the internal U: umbilical artery S: superior gluteal artery pudendal artery independently arises from a major 1: inferior g uteal artery P: internal pudendal artery

TABLE 1. Frequencies for each type in the Adachi classification from previous authors

* Significantdifferences in comparison with each type in the present study. (p < 0.05)

Kurume Medical Journal Vol. 45, No. 4, 1998 CLASSIFICATION OF INTERNAL ILIAC ARTERY 335 gluteal, inferior gluteal and internal pudendal inferior gluteal artery arises independently from the arteries) arise separately from the internal iliac common trunk. artery, and the internal pudendal artery is the last In the present study, Type I was found in 58.0% branch. of the specimens, Type II in 13.6%, Type III in 22.8% Type IV: The superior gluteal, inferior gluteal, and and Type IV in 5.4% of the specimens. Type V internal pudendal arteries arise from a common occurred in only one case with a frequency of 0.2%. trunk. If the superior gluteal artery arises first from The present data was compared to previous reports in the common trunk and the trunk later divides into the Table 1. In the present study, the frequency of Type inferior gluteal and internal pudendal arteries, it is II was significantly lower than that of Adachi and type Na. If the internal pudendal artery branches off some other reports. However, Type I was the first from the common trunk, which later divides into predominant type in all studies. the superior gluteal and inferior gluteal arteries, it is type lVb. A modification of the Adachi classification Type V: A common trunk gives rise to the superior It was previously indicated that some forms were gluteal and internal pudendal arteries, and then the different from any type in the Adachi classification [1 3] . For example, Type I has the superior gluteal artery arising independently as the first branch from the main stem, and the inferior gluteal and internal pudendal arteries arising as the second branch from a common trunk (Fig. 2a). However, in the present specimens, 54 cases (14% of Type I) had the superior gluteal artery and the common trunk of the inferior gluteal and internal pudendal arteries arising simultaneously from the main stem (Fig. 2b). Adachi [1] stated that if the two arteries sprang from a very short common trunk or the distance between the

Fig. 2. Type I in the Adachi classification. origins of the two arteries was quite short, these two a: The superior gluteal artery arising independently as the arteries were considered to arise independently. first branch from the main stem of the internal iliac However, it must be considered that these two forms artery, and the common trunk of the inferior gluteal and are different. Similarly, Type i could be divided internal pudendal arteries arising as the second branch into several subtypes (Fig. 3). Therefore, some later. subtypes for each type in the Adachi classification b: The superior gluteal artery and the common trunk of the inferior gluteal and internal pudendal arteries arise at were added in the present study, and were classified the same point. by the branching pattern of the internal iliac artery

Fig. 3. Type III in the Adachi classification. a: The origins of the superior gluteal, inferior gluteal and internal pudendal arteries are apparently separate. b: The origins of any 2 or 3 branches are not clearly separated.

Kurume Medical Journal Vol. 45, No. 4, 1998 336 YAMAKI ET AL.

Fig. 4. A modified Adachi classification.

TABLE 2. Frequency (number) of specimens in each group

into 5 types and 19 groups (Fig. 4). Type II consisted of 4 groups. Adachi's Type IIa In this modified classification, Type I consisted was subdivided into Group 1 and Group 3, and Type of 4 groups. Groups 1 and 2 are the same as Adachi's fib was subdivided into Group 2 and Group 4. Type Ia and Ib, respectively. In these cases, the Three groups were added to Type III. Group 1 is origins of the superior gluteal artery and the common the same as Adachi's Type 3, but the origins from the trunk of the inferior gluteal and internal pudendal main stem of the superior gluteal, inferior gluteal and arteries are apparently separated. When the superior internal pudendal arteries are apparently separated. gluteal artery and the common trunk of the inferior When the inferior gluteal and internal pudendal gluteal and internal pudendal arteries simultaneously arteries arise from the main stem at the same point, it originate from the main stem, these cases are is classified as Group 2; when the superior gluteal, classified as Group 3 and Group 4. inferior gluteal and internal pudendal arteries arise

Kurume Medical Journal Vol. 45, No. 4, 1998 CLASSIFICATION OF INTERNAL ILIAC ARTERY 337

TABLE 3. Frequency (number) of specimens in each group

R: right side-327 specimens; L: left side-318 specimens No significant difference was observed between the right and left sides in each group. (p<0.05)

TABLE 4. Frequency (number) of specimens in each group

426 male specimens; 219 female specimens * Significant difference between the male and female groups . (p < 0.05)

Kurume Medical Journal Vol. 45, No. 4, 1998 338 YAMAKI ET AL. from the main stem at the same point, it is classified Table 2. No significant differences were found as Group 3; and when the superior gluteal and between the numbers for the right side and left side inferior gluteal arteries arise from the main stem at in each group (Table 3). However, the females had a the same point, it is classified as Group 4. significantly higher rate for Type I-Group 1, and Type 1V had 6 groups. Group 1 is the same as significantly lower rates for Type I-Group 3 and Adachi's Type Na. When the division of the inferior Type III-Group 4 in comparison to the males (Table gluteal and internal pudenda) arteries occurs outside 4). the pelvis, it is classified as Group 2. Group 3 is the same as Adachi's Type IVb. However, when the Proposal for a new classification division of the superior and inferior gluteal arteries In the present study, the branching patterns of the occurs outside the pelvis, it is classified as Group 4. internal iliac artery in the 645 Japanese cadavers When all three major branches divide from the were investigated and separated into 5 types and 19 common trunk at the same point within the pelvis, it groups according to the modified Adachi's classifi- is classified as Group 5, and when the division cation (Fig. 4). The most frequently observed occurs outside the pelvis, it is classified as Group 6. branching pattern was the Type I-Group 1 in this Type V is a rare form, and is the same as classification. However, the frequency was less than Adachi's Type V. 50%, as described above. The results obtained in the present study were In this classification, Adachi [ 1 ] defined the organized according to this new classification and umbilical artery as a continuation of the main stem of are shown in Table 2. Differences between the right the internal iliac artery. However, in early embryos, and left sides and differences between the sexes are the umbilical artery originates as a ventral branch shown in Tables 3 and 4, respectively. from the dorsal aorta. The common iliac artery arises Although Type I-Group 1 in this classification as a dorsal branch from the dorsal aorta during the was the most frequent in the present study, the development of the lower limb bud. Secondarily, the frequency was less than 50% (46.8%), as shown in umbilical artery unites with the internal iliac artery

Fig. 5. The branching pattern of the internal iliac artery classified without the umbilical artery. The umbilical artery may arise from any part or branch of the internal iliac artery.

Kurume Medical Journal Vol. 45, No. 4, 1998 CLASSIFICATION OF INTERNAL ILIAC ARTERY 339

TABLE 5. Frequency (number) of specimens in each group

No significant difference was observed either between the right and left sides or between the sexes in each group. (p < 0.05)

through a capillary network [14]. according to this classification and is shown in Table To clarify the original branching pattern of the 5. internal iliac artery, the umbilical artery was Almost 80% of the present cases were in Group excluded from the classification of the mode of A. Moreover, there were no significant differences branching of this artery. The superior gluteal, inferior either between male and female groups or between gluteal and internal pudendal arteries were the right and left sides in each group. Group A, in determined to be the principal branches of the which the internal iliac artery divides into two main internal iliac artery, and the mode of branching of branches, the superior gluteal artery and the common this artery was classified into 4 groups (Fig. 5). trunk of the inferior gluteal and internal pudendal Group A: The internal iliac artery divides into two arteries, is the basic branching pattern for the internal branches, the superior gluteal artery and the common iliac artery. trunk of the inferior gluteal and internal pudendal Recently, Lippert and Pabst [15] proposed a arteries. Group A includes Type I-Groups 1-4, Type classification of the branching pattern of the internal Ih-Groups 1 and 2, and Type P1-Groups 1 and 2 of iliac artery from a clinical point of view. They stated our modified Adachi classification. that it was difficult to classify the branching pattern Group B: The internal iliac artery divides into two by the embryological development or practical branches, the internal pudendal artery and the features. The umbilical artery is the main branch common trunk of the superior gluteal and inferior during embryological development, and after birth gluteal arteries. Type fl-Groups 1-4 and Type IV- the umbilical artery is no longer important. In the Groups 3 and 4 of the modified Adachi classification present study, the classification was based on the are included in Group B. branching of the internal iliac artery without Group C: The internal iliac artery simultaneously considering the umbilical artery. This classification divides into three major branches. This group is simple and more useful in a medical practice. includes Type hl-Groups 3 and 4 and Type IV- Groups 5 and 6 of the modified Adachi classification. REFERENCES Group D: The internal iliac artery divides into the common trunk for the superior gluteal and internal 1. Adachi B. Das Arteriensystem der Japaner. Bd. 1. Die Kaiserlich Japanische Universitat zu Kyoto, Kyoto, pudendal arteries and the inferior gluteal artery. This 1928. group includes Type V of the modified Adachi 2. Tsukamoto N. Studies on the arterial system in pelvic classification. cavity of Japanese. Acta Mat Nippon 1929; 2:830-852. With this classification, the umbilical artery may (in Japanese) arise from any part or branch of the internal iliac 3. Miyaji K. Uber die A. hypogastrica. Arbeit Mat Institut artery, e.g., from the main stem of the internal iliac Kanazawa 1935; 20:85-93. (in Japanese) 4. Arai S. The distribution pattern of the hypogastric artery artery, the superior gluteal artery, the inferior gluteal in Japanese. Acta Anat Nippon 1936; 9:81. (in Japanese) artery, the internal pudendal artery or the common 5. Hoshiai H. Anatomical study on the pelvic arteries in trunks of these arteries. Japanese fetus. Acta Mat Nippon 1938; 11:61-72. (in Data obtained in the present study was organized Japanese)

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