Peripheral Nerve Injury (Lower Limb)

Peripheral Nerve Injury (Lower Limb) - Basic Anatomy

1. Peripheral Nerve Injury (Lower Limb) Dr Sandip Biswas

2. Femoral Nerve Formed by: Ventral rami of posterior division of L2-4 Root Value: L2-4 Motor Supply: Hip Flexor (iliacus, Sartorius, Pectineus), Knee Extensor(Quadriceps) Sensory Supply: Antero-medial thigh and antero-medial leg and foot (Saphenous Nerve) Course: The nerve descends in the abdomen from Lumbar Plexus through Psoas Major muscle. The nerve further travels downs into the thigh behind the mid-inguinal point. It divides into anterior and posterior branches which supply hip flexor and knee extensor respectively.

3. Injury can happen in – direct trauma, anterior hip dislocation, iatrogenic Problems after injury- Loss of Knee extension Mild loss of hip flexion Motor function test of femoral nerve Quadriceps: Knee Extension Sensory Test: Anteromedial aspect of thigh Anteromedial aspect of leg via Saphenous nerve Note: Meralgia Paresthetica - compression of lateral cutaneous nerve of thigh below ASIS under the inguinal ligament. It causes paraesthesia over lateral aspect of thigh

4. Sciatic Nerve Formed by : Anterior and posterior divisions of lumbosacral plexus Root value- L4-S3 Motor Supply- knee flexors(semitendinosus, semimembranosus, biceps femoris and adductor magnus). Later, it supplies muscles of entire leg and foot after dividing into common peroneal and tibial nerves Course- After exiting from the greater sciatic notch, the nerve descends in the gluteal region below the pyriformis behind the hip joint. It lies over the external rotators of hip and further descends into the thigh under the deep head of biceps femoris. In the posterior thigh, the ‘tibial component’ of sciatic nerve supplies hamstrings. At the apex of the popliteal fossa, it divides into common peroneal and tibial component.

5. Injury can happen in- Posterior dislocation of hip , posterior surgical approaches to hip, direct trauma, injection into the gluteal region Problems after the injury : Loss of knee flexion Loss of all motor activity at ankle and foot ( flail foot ) Motor Function Test of sciatic nerve: Hamstrings: Knee Flexion Test for all ankle and foot muscles Sensory test Test the sensory function of Tibial and Common Peroneal Nerve

6. Common Peroneal Nerve Root Value: Dorsal component of L4-S2 Motor Supply: Anterior comp( Tibialis Anterior, Extensor Hallucis Longus, Extensor digitorum longus, and peroneus tertius), and Lateral Comp ( Peroneus longus and brevis) of leg Sensory Supply: Superficial Peroneal Nerve: dorsum of foot except for 1 st interdigital cleft, medial and lateral borders of foot Deep Peroneal Nerve: 1 st interdigital cleft Course: descends distally along the laterally wall of the popliteal fossa under the belly of Biceps Femoris. Further, it winds around the neck of fibula between the peroneus longus and bone and divides into superficial and deep peroneal nerve. Superficial peroneal nerve supplies lateral compartment while deep peroneal nerve supplies anterior compartment muscles

7. Injury to CPN nerve can happen in – Fibular Neck Fracture , Knee Dislocation Problems after injury to CPN: “ FOOT DROP ” Loss of ankle dorsiflexion(tibialis anterior) and eversion (peroneal longus and brevis) Loss of great and lesser toe extension (EHL and EDL) High stepping Gait Motor function test : Tibialis anterior: dorsiflexion in inversion EHL,EDL: Extension of great toe and other digits Peroneus Longus and brevis: Eversion at subtalar joint Sensory Test Dorsum of 1st web space: deep peroneal nerve Rest of the dorsum: superficial peroneal nerve

8. Tibial Nerve Root Value- Ventral component of L4-S3 Motor Supply: All muscles of the posterior compartment of leg and plantar aspect of foot Sensory Supply- Plantar aspect of foot via medial and lateral plantar nerves Course: It descends distally in the center of popliteal fossa and enters the leg under the arch of soleus. In popliteal fossa, it supplies gastrocnemius, popliteus, plantaris, and soleus. Further, it descends and goes behind the medial malleolus under the flexor retinaculum and it enters the foot. It divides into medial and lateral plantar nerves and supplies the entire four layers of foot muscles along with skin of plantar region.

9. Injury to tibial nerve can happen in- knee dislocation, proximal tibia fractures, compartment syndrome, compressive neuropathy under the flexor retinaculum Problems after the injury : Loss of ankle plantar flexion (gastrosoleus) Weak inversion (tibialis posterior) Loss of plantar flexion of toes Claw toes : occurs after injury to the posterior tibial nerve near ankle leading to palsy of all foot intrinsic muscles High stepping gait Motor Function test : Tendoachilles: ankle plantar flexion while standing on tip toe Tibialis posterior: inversion in plantar flexion Great toe flexor hallucis longus(FHL) and lesser toe Flexor Digitorum Longus (FDL) plantar flexion Sensory Test Sensory over the plantar aspect of foot Note: Tarsal Tunnel Syndrome- Compression of tibial nerve under the flexor retinaculum behind the ankle