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Lumbosacral Plexus
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The lumbosacral plexus can be divided into two anatomical parts: the upper lumbar plexus and the lower lumbosacral plexus.
Lumbar Plexus
The lumbar plexus is located within the psoas muscle. It contains the canterior rami of the T12 to L4 nerve roots. Only the femoral nerve can be reliably tested by EMG. The lateral femoral cutaneous nerve can be tested but it is unreliable.
Nerve | Origin | Sensory Innervation | Motor Innervation |
---|---|---|---|
Femoral Nerve | L2, L3, L4 anterior rami, posterior divisions | Skin of medial lower leg through saphenous nerve | Quadriceps Femoris, Sartorius, Pectineus, Iliacus, |
Genitofemoral Nerve | L1, L2 | Skin of femoral triangle, lower scrotum/labia | Cremasteric muscle in men |
Iliohypogastric Nerve | T12, L1 | Skin of lower abdomen | Transversus Abdominis, Internal Obliques |
Ilioinguinal Nerve | L1 | Skin to inguinal region, small area of medial thigh, upper scrotum/labia. | Transversus Abdominis, Internal Oblique |
Lateral Femoral Cutaneous Nerve | Posterior divisions of L2 and L3 spinal nerves | Anterolateral thigh | |
Lumbosacral Trunk | L4, L5 (mainly L5) | Skin of L5 | Ankle dorsiflexors, ankle everters, ankle inverters |
Obturator Nerve | L2, L3, L4 anterior rami | Skin of medial thigh | Adductor Magnus (anterior half), Adductor Longus, Adductor Brevis, Gracilis, Obturator Externus |
Sacral Plexus
The sacral plexus is derived from the anterior rami of spinal nerves L4-S4.
Nerve | Segment | Motor Supply | Action | Sensory Supply |
---|---|---|---|---|
Superior gluteal | L4-S1 | Gluteus medius, gluteus minimus, tensor fasciae latae | hip abduction | buttock pain |
Inferior gluteal | L5-S2 | Gluteus maximus | hip external rotation and power extension | N/A |
Sciatic trunk/nerve | L5โS3 | Tibial portion: Posterior compartment of the thigh and leg Common peroneal division: short head of biceps femoris, and anterior, and lateral compartments of the leg, and extensor digitorum brevis. and leg through common peroneal and tibial nerves |
Tibial portion: Sole of the foot (medial and lateral plantar nerves) Common peroneal division: Anterolateral surface of the leg (sural nerve), first webspace of foot (deep peroneal nerve), and dorsal aspect of the foot (superficial peroneal nerve) | |
Posterior femoral cutaneous nerve | - | - | Posterior surface of the thigh, leg, and perineum (perineal branches and inferior cluneal nerves) | |
Pudendal nerve | S2-4 | Muscles of the perineum | Penis, clitoris, most of the perineum | |
Nerve to piriformis | ||||
Nerve to obturator internus and superior gemellus |
Other Branches
Nerve | Segment | Motor Supply | Action | Sensory Supply |
---|---|---|---|---|
Tibial | L4-S3 | Hamstrings (except short head of biceps femoris, posterior part of adductor magnus), triceps surae, tibialis posterior, popliteus, flexor digitorum longus, flexor hallucis longus, intrinsic muscles of foot | Knee flexion(primary), foot plantar flexion, toe flexion | skin of posterior leg and sole of foot |
Common fibular | L4-S2 | short head of biceps femoris, fibularis longus and brevis, tibialis anterior, extensor hallucis | knee flexion (short head of biceps femoris), foot dorsiflexion and eversion, toe extension | skin of anterior and lateral leg and dorsum of foot |
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