Introduction:
Internal iliac artery [IIA] is the smaller terminal branch of the common iliac artery.
It supplies the pelvic organs, pelvic walls and proximal part of the lower limb through its branches. As
described in the textbooks, it usually divides into anterior and posterior divisions. The anterior division
gives superior vesical, inferior vesical, middle rectal, obturator, internal pudendal and inferior gluteal
arteries. In females, the anterior division also gives uterine and vaginal arteries. The posterior division
gives iliolumbar, lateral sacral and superior gluteal arteries.[1] However, IIA fails to divide into anterior
and posterior divisions in a few cases; where all its branches directly come from its trunk. The branches that
are normally given by anterior division might come from posterior division and vice versa. Some of its branches
like obturator artery might come from other arteries like inferior epigastric artery also. A thorough
knowledge of these variations is useful to various medical disciplines for a proper diagnosis and treatment
and to avoid iatrogenic injuries during various procedures. We report some rare variations in the branches
of the internal iliac artery and discuss their clinical implications in this report.
Case Report
During our dissection classes for first year medical students, we noted the
following variation in the branches of right internal iliac artery in an adult male cadaver aged approximately
65 years. The internal iliac artery first gave rise to iliolumbar artery and then divided into anterior and
posterior divisions. The anterior division further divided into anterior and posterior trunks. The anterior
trunk gave origin to superior vesical, inferior vesical, middle rectal and obturator arteries. The posterior
trunk gave rise to two inferior gluteal arteries and an internal pudendal artery. One among the two inferior
gluteal arteries ended by supplying muscles of gluteal region, whereas the other one had a normal course and
distribution of the inferior gluteal artery as described in the textbooks. The posterior division gave rise to
lateral sacral and superior gluteal arteries. The superior gluteal artery pierced the lumbosacral trunk before
leaving the pelvis. After piercing the lumbosacral trunk, it entered the gluteal region through greater
sciatic foramen, above the piriformis muscle. Its course and distribution in gluteal region was normal. The
variations are shown in Figures 1-3.
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Figure 1. Photograph of dissected right hemipelvis
showing the branches of internal iliac artery.
(IIA internal iliac artery; ILA iliolumbar artery; AD anterior division; PD posterior division; AT anterior trunk of anterior division; PT posterior trunk of anterior division; SVA superior vesical artery; IVA inferior vesical artery; MRA middle rectal artery; OA obturator artery; MUL medial umbilical ligament; LSA lateral sacral artery; SGA superior gluteal artery)
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Figure 2. Photograph of dissected right hemipelvis showing the piercing of lumbosacral trunk by the superior gluteal artery.
(IIA internal iliac artery; AD anterior division; PD posterior division; AT anterior trunk of anterior division; PT posterior trunk of anterior division; SVA superior vesical artery; IVA inferior vesical artery; MRA middle rectal artery; MUL medial umbilical ligament; LSA lateral sacral artery; SGA superior gluteal artery; LST lumbosacral trunk)
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Figure 3. Photograph of dissected right hemipelvis showing the piercing of lumbosacral trunk by the superior gluteal artery.
(IIA internal iliac artery; AD anterior division; PD posterior division; AT anterior trunk of anterior division; PT posterior trunk of anterior division; SVA superior vesical artery; IVA inferior vesical artery; MRA middle rectal artery; OA obturator artery; MUL medial umbilical ligament; IGA inferior gluteal artery; IPA internal pudendal artery; LSA lateral sacral artery; SGA superior gluteal artery)
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Discussion
Internal iliac artery is known to show variations in its branching pattern. One of the rare
variations of IIA is its total absence.[2] When it is absent, its territory is taken care by nearby vessels such as lumbar
arteries. First classification of variations of branches of IIA was done by Jastshinski on Polish population.[3] He classified
the vessels into four types. Adachi et al., further classified the branches into five types in Japanese people.[4] Later this
classification was modified by Yamaki.[4] Adachis classification is the most popular among all classifications. In the
current case, the anterior division of the IIA divided into anterior and posterior trunks. None of the above classifications
describe this type of subdivision of anterior trunk of IIA. There are reports on total absence of inferior gluteal artery and
its replacement by other arteries.[5] However, its duplication as reported in the current case is extremely rare. It is a boon
for plastic surgeons to have two inferior gluteal arteries.[6] An inferior gluteal artery flap can be raised without
compromising blood supply to the gluteal region in such cases.
Iliolumbar artery usually arises from the posterior division of IIA as its first branch. However, it may arise directly
from the common iliac or IIA. In the current case, it arose directly from the main trunk of the IIA. This type of direct
origin can be found in 14-71% of cases as reported in the literature.[7-9] Iliolumbar artery is an important landmark in
orthopedic surgery. Knowledge of its variations comes handy in orthopedic procedures.[7,8]
Superior gluteal artery is a constant branch from the posterior division of IIA. It does not show many variations. After
giving iliolumbar and lateral sacral artery, posterior division of IIA continues as superior gluteal artery. It leaves the
pelvis through greater sciatic foramen above the piriformis muscle, along with superior gluteal nerve. Just before leaving the
pelvis, it passes through the gap between the lumbosacral trunk and ventral ramus of first sacral nerve. In the current case,
this artery pierced the lumbosacral trunk before leaving the pelvis. This is an extremely rare variation and to the best of
our knowledge, has not been reported yet. Knowledge of variation of superior gluteal artery is very useful in radiological,
orthopedic and plastic surgery procedures. Transcatheter embolisation for pseudo aneurysms[10,11], and iliosacral screw
placement [12] are the techniques that require a sound knowledge of variations of this artery. Deep inferior epigastric
perforator is of first preference for breast reconstruction surgery. Superior gluteal artery flap is the second option for
this surgery.[13] However, superior gluteal artery flap is used in some other procedures such as sacral sore coverage[14],
and meningomyelocele defect cover.[15] Angioplasty of superior gluteal artery is done in patients with buttock claudication.[16] However, the possibility of lumbosacral trunk being pierced by it has to be kept in mind during this procedure. Gluteal
compartment syndrome [17,18] is noted in some cases of hip dislocation. In the current case, entrapment of the superior
gluteal artery in the lumbosacral trunk might also lead to symptoms similar to that of gluteal compartment syndrome.
Conclusion
Though it is not uncommon for iliolumbar artery to arise directly from main trunk of IIA,
it is very rare to see anterior division of IIA to divide into two trunks, duplication of inferior gluteal artery and piercing
of lumbosacral trunk by superior gluteal artery. Thus the case we are presenting here is unique. It has many clinical
implications too. Duplication of inferior gluteal artery can be a boon to plastic surgeons raising inferior gluteal artery
flaps. Piercing of lumbosacral trunk by superior gluteal artery might make radiological procedures and surgical procedures
difficult. Compression of the superior gluteal artery within the lumbosacral trunk might lead to vascular symptoms in the
gluteal region and thigh. The artery might also compress the lumbosacral trunk and the symptoms may mimic that of sciatica.
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