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lateral circumflex artery.
The gluteal nerve travels with the artery and vein. These structures are closest to the posterior column as they
exit through the superior aspect of the sciatic notch. They are relatively fixed as they pass out of the pelvis above
the piriformis muscle (Fig. 2.7). Surrounding fat and extraperitoneal tissue provide 2 to 10 mm of tissue
interposition between these structures and the posterior acetabular column (4). Terminal branches of these
structures come to lie between the minimus and medius muscles.
Inferior Gluteal and Internal Pudendal Vessels
The inferior gluteal and internal pudendal vessels are the terminal branches of the anterior division of the internal
iliac artery exiting the pelvis inferior to the piriformis to supply the gluteus maximus. They are closest to the
posterior column at the level of the ischial spine. The internal pudendal vessel is closer to the posterior column
as it curves around the ischial spine to re-enter the pelvis through the lesser sciatic notch (Fig. 2.9).
Figure 2.9. The course of the intrapelvic and extrapelvic vessels in relationship to the osseous pelvis.
Posterior branches of the inferior gluteal artery pass along the lower border of the piriformis across the sciatic
nerve. The sciatic nerve receives a branch from this artery and is named the arteria comitans nervi ischiadici.
The inferior gluteal artery continues in a distal direction to provide arterial branches to the short rotator muscle.
In fracture work, these muscular branches may be important to maintain adequate circulation to bone fragments.
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Obturator Artery
The obturator artery branches from the internal iliac artery closely approximated to the lateral wall of the pelvis
on the obturator fascia between the obturator nerve and vein. The proximity of these structures to the inner wall
of the acetabulum places them at risk to injury from penetration through
the acetabulum, such as from screw placement during hip replacement, or fracture fixation. The obturator artery
penetrates the obturator membrane and exits the pelvis through the obturator foramen. After exiting the foramen,
the obturator artery divides into anterior and posterior branches. The anterior branch anastomoses with the
posterior branch and the medial circumflex artery and supplies the obturator externus, pectineus, adductors, and
gracilis muscles. The posterior branch anastomoses with the anterior branch and also branches to the inferior
gluteal supply. An acetabular branch penetrates the acetabular fossa beneath the transverse acetabular
ligament to enter into the ligamentum teres to provide one of the three major sources of blood to the femoral
head.
Surgical Considerations
The common femoral vessels have been the most commonly reported extrapelvic vascular structures injured in
association with THA. The most commonly cited mechanism of injury to the femoral vessels has been aberrant
retractor placement during the surgical approach (Fig. 2.8) (52,53,54,55). This can occur during the anterior
lateral approach when a retractor is placed too far medially over the anterior inferior acetabular margin. Bulk
allograft placement for acetabular reconstruction (56), osteophyte resection, and resection of scar tissue from the
anterior inferior acetabulum have also resulted in femoral artery injury (54,57). During cemented acetabular
component fixation, extrusion of excess cement anteromedially has resulted in pseudoaneurysm formation,
thrombus formation (58), and peripheral femoral arterial embolization (59). Intimal damage from the heat of
polymerization is the likely cause. Prolonged external pressure from cement spicules has resulted in
postoperative vessel erosion and pseudoaneurysm formation (59,60,61,62) and the formation of an
arteriovenous fistula (54). These injuries can be avoided by placing a lap pad in this region during cementing or
by removing anterior extra-acetabular cement before polymerization.
Ischemia can present after THA without intraoperative hemorrhage in patients with severely atherosclerotic
vessels. When significant vessel disease is suspected, traction on the extremity should be minimized during
THA. Dislocation and reduction maneuvers (54,58,63,64,65) and complete restoration of length (63) or correction
of flexion contractures must also be done with care. Intraoperative plethysmographic monitoring should be
considered in high-risk patients (with calcification on x-ray). Vascular consultation should be obtained prior to hip
arthroplasty if the Doppler pressure at the ankle is less than 50 mm Hg (63,64) or if there is clinical evidence of
ischemia preoperatively.
The profundus femoris vessels can also be injured during THA. Retractor placement too far medially over the
anterior inferior quadrant can result in a false aneurysm of the medial circumflex artery (Fig. 2.8) (52). Extruded
cement in this region may also cause injury to the medial circumflex (52). When this vessel is encountered at the
superior border of the quadratus femoris muscle, it seldom causes significant hemorrhage unless injured closer
to its origin. Hohmann retractor placement over the anterior hip capsule and gluteus medius has resulted in
severe arterial hemorrhage from femoral profundus and lateral circumflex artery laceration (54). Osteotome use
during the removal of scar and capsule during revision surgery has also resulted in injury to the lateral circumflex
artery (54).
Laceration of the superior gluteal artery has occurred with a fixation screw in the area of the sciatic notch (66).
Injury has also occurred when a pin retractor was inserted in the direction of the notch (67). The superior gluteal
vessels are as close as 2 mm from bone at this point. To minimize the risk to the superior gluteal vessels during
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transacetabular screw placement, the notch should be gently palpated to avoid instrument protrusion into this
region.
The gluteal vessels pass under the piriformis in the lower part of the greater sciatic foramen. Injury to these
vessels can occur from excessively long transacetabular screws used for acetabular component fixation. These
screws would need to exit the posterior column by at least 5 mm because these structures are located at least
this distance from bone (4).
Intrapelvic Vasculature
External Iliac Artery and Vein
The external iliac artery is the anterior division of the common iliac artery after its bifurcation at the level of the
L5-S1 vertebral disc. It runs obliquely down the medial border of the psoas major muscle and anterior and lateral
to the external iliac vein, with a portion of the muscle interposed between itself and the intrapelvic surface of the
anterior column. The amount of interposed psoas muscle decreases from proximal along the arcuate line to distal
at the iliopubic eminence, as the muscle becomes tendinous opposite the anterior superior quadrant
(4,19,20,21,24,28). The external iliac vein accompanies the artery. Proximally, the vein runs medial and posterior
to the artery. More distal, opposite the anterior superior quadrant, the vein runs medial and inferior to the artery
along the medial border of the psoas with only minimal muscular and fascial interposition between itself and the
pelvic brim (4,21,24,28). It is relatively immobile along the pelvic brim, being interposed between the anterior
column and the parietal peritoneum (19,20,21,27,28).
Obturator Vessels
The obturator nerve, artery, and vein most frequently traverse the lateral wall (quadrilateral surface) of the pelvis
together, covered by parietal peritoneum, with the nerve located most superior and the vein most inferior
(19,20,21,24,26,27,28,68). The obturator internus muscle and fascia lie lateral to these structures, separating
them from the quadrilateral surface opposite the anterior inferior quadrant of the acetabulum. The obturator
nerve, artery, and vein lie in contiguity