Anaes SAQs · Applied anatomy

Lumbosacral plexus anatomy

Primary — lumbar plexus L1-L4 within psoas (iliohypogastric/ilioinguinal L1, genitofemoral L1-2, lateral femoral cutaneous L2-3, femoral L2-4, obturator L2-4); sacral plexus L4-S4 on piriformis (sciatic L4-S3 the largest nerve, superior/inferior gluteal, pudendal S2-4, posterior femoral cutaneous); sciatic divides in popliteal fossa into tibial (plantar foot) and common peroneal (dorsum of foot); blocks (femoral/fascia iliaca anterior thigh, obturator adductors, PENG hip, sciatic/popliteal leg and foot, pudendal perineum); foot drop = common peroneal/L5; meralgia paraesthetica = LFCN.