Final answer:
The internal iliac artery is the most commonly injured arterial vessel in APC pelvic fractures due to its location in the pelvis and the distribution of its branches.
Step-by-step explanation:
The most commonly injured arterial vessel with an APC (anteroposterior compression) pelvic fracture is the internal iliac artery. The internal iliac artery is a branch of the common iliac arteries that provides blood to important pelvic structures including the walls of the pelvis, urinary bladder, the external genitalia, and the medial portion of the femoral region. In females, this also includes the uterus and vagina. Due to its location and the distribution of its branches within the pelvis, the internal iliac artery is particularly susceptible to injury when an APC pelvic fracture occurs.
When a pelvic fracture happens, the bones may disrupt the artery's structural integrity, leading to potential life-threatening bleeding. The nearby external iliac artery, although larger, is less commonly affected by pelvic fractures as it traverses a different path to supply blood to the lower limbs.