Thursday, October 25, 2012

Internal Iliac artery: Posterior Division: Superior Gluteal Artery

The external iliac artery in the pelvis is usually pretty straightforward -- more or less just a straight shot through pelvis, with a little inferior epigastric branch and deep circumflex iliac branch usually coming off.

The internal iliac artery ("hypogastric artery"), however, is a different matter. There is extensive variation of its numerous branches, which usually initially branch into two divisions anterior and  posterior before branching out into numerous vessels to supply the pelvic muscles and organs. Because of the extensive variation, identification of these vessels is usually easier from looking at what they supply rather than from where they originate.

The posterior division of the internal iliac artery typically has three branches:

1. The iliolumbar artery
2. The lateral sacral arteries
3 The superior gluteal artery

Patient with pelvic trauma, fracture, and active pelvic hemorrhage on CT was referred for embolization.  Multiple sites of hemorrhage in the left internal iliac artery anterior division branches noted, as well as possibly in the the right lateral sacral artery.  Incidental note is made of a bifurcated origin of the left femoral artery.

1. The iliolumbar artery usually arises most proximally, and can arise from the proximal iliac artery before the bifurcation into the anterior and posterior divisions. It courses superiorly, overlying the region of the sacroiliac joint.

2. The lateral sacral arteries are small and variable, and named for their position overlying the lateral sacrum. There are usually two, but they can be up to four in number. The anastomose with the median sacral artery and lateral sacral vessels.

3. The superior gluteal artery (SGA) is the largest artery of the posterior division, and courses posteriorly through the greater sciatic foramen, above the piriformis muscle. Its large size supplies the gluteal musculature (and piriformis). It is the most commonly injured pelvic artery in a pelvic fracture, with shearing against the bony portion of the greater sciatic foramen.  (The next most common are the internal pudendal artery and the obturator artery). The SGA forms multiple collaterals with other pelvic arteries, including the inferior gluteal artery, medial circumflex, and lateral femoral circumflex.

A more selective arteriogram nicely shows the superior gluteal artery passing underneath the greater sciatic notch and then branching out to supply the gluteal musculature.

The proximal left superior gluteal artery is coil embolized in preparation for treatment of hemorrhage. This prevents nontarget gelfoam particles traveling into the gluteal musculature during embolization of the internal iliac anterior division branches. Collateral supply will continue to supply the gluteal musculature.

Completion angiography of the right common iliac artery. Coil in the left superior gluteal artery as before.  The right superior gluteal artery is shown nicely.

There are also multiple reports of injury to the superior gluteal artery during iliac bone graft procedures. Although an uncommon event, endovascular control of bleeding in this injury can be life-saving.

In about 20% of patients, the obturator artery arises off the SGA.

1. "Vascular and Interventional Radiology: The Requisites" Kaufman JA and Lee MJ. 1st ed (2004)
2. "Vascular and Interventional Radiology Principles and Practice" Bakal CW, ed. (2002)
3. "Diagnostic Angiography" Kadir S. (1986)
4. "Vascular and Interventional Radiology" Valji, ed. 2nd ed (2006)
5. Lim EVA,  Lavadia WT, Roberts JM. "Superior Gluteal Artery Injury During Iliac Bone Grafting for Spinal Fusion: A Case Report and Literature Review" Spine, Volume 21(20), (October 1996) pp 2376-2378
6.  "Skandalakis' Surgical Anatomy" (2004)