LUMBOSACRAL PLEXUS
Lumbosacral Plexus Components: Components: Lumbar plexus: L1--L4. Lumbosacral trunk: L4—L5. Sacral plexus: S1—S4.
Lumbar Plexus Formed in psoas major: Formed in psoas major: From ventral rami of L1..L4. Branches emerge from both lateral and medial sides of psoas major: Connect to sympathetic trunk.
Lumbar Plexus L1: L1: Variably connected to T12 (subcostal) and L2. Two branches emerge from lateral side of psoas major: Iliohypogastric (GSA): to side of buttock and pubis. Ilioinguinal (GSA): to anterior thigh, scrotum, labia majora.
Lumbar Plexus Genitofemoral nerve: Genitofemoral nerve: Emerges on anterior surface of psoas major. Genital branch: Enters inguinal canal. Supplies scrotum and labia majora (GSA). Supplies cremaster muscle (GSE). Femoral branch: Enters femoral sheath. Supplies skin over femoral triangle.
Lumbar Plexus Femoral nerve: Femoral nerve:L2—L4. Largest branch of lumbar plexus. Emerges from lateral side of psoas major.
Lumbar Plexus Femoral nerve: Femoral nerve: Enters thigh behind inguinal ligament. Supplies: In iliac fossa: Iliacus (GSE); pectineus (GSE); femoral artery (GVE).
Lumbar Plexus Femoral nerve: Femoral nerve:Supplies:Distally: Sartorius; quadriceps femoris; anterior thigh (GSA). Terminates as: Saphenous nerve (GSA) to medial thigh and foot.
Lumbar Plexus Obturator nerve: Obturator nerve:L2..L4. Emerges from medial side of psoas major. Descends along lateral wall of pelvis.
Lumbar Plexus Obturator nerve: Obturator nerve: Enters thigh through obturator foramen: In obturator groove it divides into: Anterior branch (anterior to adductor brevis). Posterior branch (posterior to adductor brevis).
Lumbar Plexus Obturator nerve: Obturator nerve:Supplies: Medial thigh muscles (GSE). Skin on medial thigh (GSA).
Sacral Plexus Superior gluteal nerve: Superior gluteal nerve:L4..S1. Passes through greater sciatic notch above piriformis. Supplies lateral gluteal compartment.
Sacral Plexus Inferior gluteal nerve: Inferior gluteal nerve:L5..S2. Passes through greater sciatic notch below piriformis. Supplies posterior gluteal compartment.
Sacral Plexus Posterior femoral cutaneous: Posterior femoral cutaneous: Runs with gluteal nerves deep to gluteus maximus. Then runs with sciatic nerve and gluteal artery.
Sacral Plexus Posterior femoral cutaneous: Posterior femoral cutaneous:Supplies: Skin on buttock (GSA) via inferior cluneal nerve. Skin of external genitalia (GSA) via perineal branches. Skin on back of thigh.
Sacral Plexus Nerves to lateral thigh compartment: Nerves to lateral thigh compartment: To inferior gemellus (GSE): L4..S1. To quadratus femoris (GSE): L4..S1. To piriformis (GSE): S1..S2.
Sacral Plexus Sciatic nerve: Sciatic nerve: Fusion of: Common peroneal (fibular). Tibial. Largest physical nerve in the body.
Sacral Plexus Sciatic nerve: Sciatic nerve: Exits pelvis through greater sciatic foramen: Inferior to piriformis (usually). Descends between gluteus maximus. Between greater trochanter and ischial tuberosity. Lies on: Ischium, gemelli, obturator internus, quadratus femoris.
Nerve Injuries Peripheral: Peripheral: All motor function and sensation supplied by nerve distal to injury is lost. Total muscle function is lost. Sensation over more than one dermatome is lost.
Nerve Injuries Nerve root: Nerve root: Usually affected by disc herniation immediately cranial (superior) to it. Sensory impairment over one dermatome. Muscle weakening. May only affect one root or the other.