Figure 3.

Retroperitoneal approach to the L5-S1 disc. After the circumferential sweep around the undersurface of the transversalis, palpate and follow the internal abdominal wall along with the inside of the pelvis (a). Once touch the iliopsoas, the blunt dissection continues anteriorly from the pelvis while searching for the very palpable common iliac artery pulse (b). Once palpate the pulse on the finger pad, move the finger medially by keeping to feel the pulse on the dorsal side of the finger (c). Direct visualization of the iliopsoas muscle and the common iliac vessels should be established in addition to the tactile feeling. (d) The index finger is touching the promontory by feeling the arterial pulse on the dorsal side of the finger.