Indications Can access L1 to sacrum slightly more difficult to reach L5-S1 disk space than transperitoneal approach bifurcation of great vessels anterior to L4 vertebral body Indications psoas abscess drainage (without risk of postoperative ileitits) spinal fusion biopsy or resection of vertebral body disc replacement exposure of sympathetic chain (general surgery) Postion Place in semilateral position (45 degrees to horizontal) use sandbags or bean bag to hold patient at angle or place patient supine and tilt table Place left side up aorta is more resistent to injury than vena cava Incision Make incision from posterior half of 12th rib to lateral border of rectus abdominis (midway between umbilicus and pubic symphysis) Approach Approach to spine incise subcutaneous fat expose aponeurosis of external oblique muscle divide external oblique in line with fibers divide internal oblique in line with incision and perpendicular to muscle fibers divide transverus abdominis in line with skin incision bluntly disect plane between retroperitoneal fat and psoas fascia retract peritoneal cavity medially bring ureter with peritoneal cavity follow surface of psoas muscle to vertebral bodies tie off segmental lumbar arteries of aorta in the field of dissection L4/5 disc space mobilize aorta to the contralateral side place needle in disc and take lateral xray to identify level L5/S1 disc space work between the bifurcation of aorta place needle in disc and take lateral xray to identify level Dangers Sympathetic chain lateral aspect of vertebral body Genitofemoral nerve anterior surface of psoas muscle attached to fascia Segmental arteries segmental lumbar arteries and veins aorta Ureter lies between psoas fascia and peritoneum attached more firmly to peritoneum stroke to produce peristalsis to confirm Superior hypogastric plexus injury leads to retrograde ejaculation