MOB TCD Anatomy of Nerve Injuries Lower Limb Professor Emeritus Moira O’Brien FRCPI, FFSEM, FFSEM (UK), FTCD Trinity College Dublin.
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MOB TCD Anatomy of Nerve Injuries Lower Limb Professor Emeritus Moira O’Brien FRCPI, FFSEM, FFSEM (UK), FTCD Trinity College Dublin MOB TCD Anatomy of Nerve Injuries • • • • • Dermatomes Entrapment of Nerves Pierce Muscle Pierce Fascia Repetitive Movements MOB TCD Anatomy of Nerve Injuries • • • • • • Must know the course of nerve Dermatomes Entrapment of nerves Pierce muscle Pierce fascia Repetitive movements MOB TCD Dermatomes and Myotomes Nerves supply • Skin • Muscles (group) • Tendons • Bones • Joints • Blood vessels MOB TCD Extrinsic Factors • External forces • Fibro-osseous tunnels, tether the nerve • Oedema • Callus formation as a result of a fracture • External compression due to specific movements • Mechanical compression • Compartment syndromes • The nerve is tender at the site of compression MOB TCD Extrinsic Factors • Fibrous bands • • • • Accessory muscles Spurs Narrow notches Anatomical variations of the nerve itself MOB TCD Lumbosacral Plexus Entrapment Syndromes in Lower Limb • Affects branches of lumbar or sacral plexuses • Pierces muscle • Pierces fascia • Increase in compartment pressure • Compressed by external pressure MOB TCD MOB TCD Skin of Anterior Abdominal Wall • Lower five intercostal nerves • Subcostal nerve T12 • 10th intercostal nerves at the level of the umbilicus • Iliohypogastric nerve L1 • Ilioinguinal nerve L1 MOB TCD Cutaneous Nerves of Thigh • • • • Subcostal nerve T12 Iliohypogastric nerve L1 Ilioinguinal nerve L1 Femoral branch of the genitofemoral nerve L1,2 • Lateral cutaneous nerve of the thigh L2,3 • Femoral nerve L2,3,4 • Obturator nerve L2,3,4 MOB TCD Cutaneous Nerves MOB TCD Iliohypogastric Nerve L1 • Branch of lumbar plexus • Lateral border of psoas • Anterior to quadratus lumborum • Neurovascular plane between internal oblique and transversus • Lateral cutaneous supplies upper part of buttock MOB TCD Iliohypogastric Nerve • Pierces internal oblique above anterior superior iliac spine • Pierces aponeurosis of external oblique an inch above superficial ring • Supplies skin over lower part of rectus sheath • Can be trapped piercing aponeurosis MOB TCD Ilioinguinal Nerve • • • • • Ilioinguinal nerve L1 branch of lumber plexus Lateral border of psoas Anterior to quadratus lumborum Neurovascular plane between internal oblique and transversus MOB TCD Ilioinguinal Nerve • Pierces internal oblique 4 cm medial to • Anterior superior iliac spine • Enters inguinal canal • Leaves through superficial ring • Supplies the skin of the medial part of the thigh • Adjoining portion of the scrotum and labia MOB TCD Ilioinguinal Nerve • May be trapped post surgery, due to adhesions • Poor tone in abdominal muscles • Pain increased by increased tension in the anterior abdominal wall • Hyperextension of hip • Tenderness 4 cm from anterior superior iliac spine MOB TCD Ilioinguinal Nerve Entrapment • Pain increased • Increased tension in the anterior abdominal wall • Hyperextension of hip • Tenderness 4 cm medial to anterior superior iliac spine MOB TCD Cutaneous Nerves • Iliohypogastric in 5.6% • Ilioinguinal 90.7% • Union of branches of ilioinguinal and genital branch of the genitofemoral nerve 13% • Genitofemoral passing through superficial inguinal ring 35.2% • Piercing inguinal ligament 5.6% • Femoral branch 13% Akita et al., 1999 MOB TCD Genitofemoral Nerve • Lumbar plexus L1,2 • Anterior aspect of the psoas • Genital branch enters the deep inguinal ring • Femoral branch lies on the lateral side of femoral artery in the femoral sheath MOB TCD Femoral Branch Genitofemoral • Enters thigh on lateral aspect of femoral artery in femoral sheath • Pierces anterior wall of the sheath • Supplies skin a hands breath below the inguinal ligament MOB TCD Genitofemoral Nerve • Union with ilioinguinal nerve on anterior aspect of spermatic cord • Supplies ventral aspect of scrotum and adductor region • Cutaneous branch on the dorsal-caudal aspect • May also supply dorsal scrotum Akita et al., 1999 MOB TCD Genitofemoral Nerve Lateral Cutaneous Nerve of Thigh L2,3 • • • • • • Lumbar plexus in psoas Lateral aspect of psoas Pierces inguinal ligament Lies in fibrous tunnel Divides into two Pierces deep fascia MOB TCD MOB TCD Lateral Cutaneous Nerve of Thigh • A centimeter medial to anterior superior iliac spine • Crosses the lateral angle of femoral triangle • Divides into two • Pierces deep fascia • Anterolateral aspect of the thigh • Anterior portion of gluteal region LCN MOB TCD Lateral Cutaneous Nerve of Thigh • Entrapment in the fascial tunnel • Injured in the thigh by asymmetric bars in gymnastics • Causes meralgia paraesthetica • Post laparoscopic surgery MOB TCD Femoral Nerve L2,3,4 • • • • • • • • • Largest branch of the lumbar plexus Lateral aspect of psoas Passes under the inguinal ligament Outside femoral sheath 2 cm below Divides into terminal branches Muscular Articular Cutaneous MOB TCD Femoral Nerve Muscular branches • Rectus femoris • Vastus medialis, • Vastus lateralis • Vastus intermedius • Sartorius, pectineus Cutaneous • Medial cutaneous nerves of thigh • Intermediate cutaneous nerves of thigh • Saphenous Articular branches to hip and knee joints MOB TCD Femoral Nerve • Dancers may stretch the nerve by prolonged hyperextension of the hip • Compress the nerve under the inguinal ligament • Nerve may also be compressed due to a haematoma following a partial tear of the iliacus O’Brien, 1997 MOB TCD Femoral Nerve Femoral nerve Saphenous MOB TCD Obturator Nerve L2,3,4 • Lumbar plexus in psoas • Medial aspect of psoas • Side wall of pelvis under peritoneum • Leaves through obturator foramen • Divides into anterior and posterior divisions MOB TCD Obturator Nerve • Supplies the parietal peritoneum on side wall of the pelvis • Is related to the ovary • Pathology in the ovary or endometriosis may result in referred pain to the hip, knee or medial side of the high MOB TCD Anterior Division Obturator • Anterior division of the obturator leaves pelvis • Anterior to obturator externus • Descends in front of adductor brevis • Behind pectineus and adductor longus Obturator nerve MOB TCD Anterior Division Obturator • • • • Adductor longus Adductor brevis Gracilis It gives an articular twig to the hip joint • Skin on the medial side of the thigh MOB TCD Obturator Nerve MOB TCD Posterior Division Obturator • It may be entrapped as it leaves the pelvis • Pierces and supplies the obturator externus • Causing spasm of the adductor muscles MOB TCD Posterior Division Obturator • Supplies adductor portion of adductor magnus, above hiatus • Articular twig to knee joint and cruciate ligaments • Causing spasm of the adductor muscles • It may be entrapped as it leaves the pelvis or between fascial planes MOB TCD Obturator Nerve Obturator nerve Fascial planes MOB TCD Howship Rhomberg Sign • Pressure on obturator nerve • Pain on inner aspect of thigh relieved by flexion of hip • Increased by extension, adduction and medial rotation MOB TCD Obturator Nerve MOB TCD Psoas Muscle MOB TCD Sacral Plexus MOB TCD Pudendal Nerve MOB TCD Pudendal Nerve • Compression of pudendal nerve in cyclists due to saddle • History of change of saddle • Compressing dorsal nerve of penis Sciatic Nerve Posterior Cutaneous Nerve Thigh MOB TCD MOB TCD Sciatic Nerve L4,5, S1,2,3 • Is the largest nerve in diameter in the body • It passes out of the pelvis below piriformis and descends between the greater trochanter of the femur and the ischial tuberosity • Passes deep to gluteus maximus • More distally it lies on adductor magnus MOB TCD Sciatic Nerve • Is crossed by the long head of biceps femoris • Divides in middle of thigh • Tibial and common peroneal nerves • Common peroneal may pierce piriformis if divides in pelvis • Supplies hamstrings • Adductor magnus below hiatus MOB TCD Sciatic Nerve • Occasionally it divides in the pelvis • Then the common peroneal portion may pierce the piriformis muscle to enter the thigh • Recurrent injury to the hamstring muscles produces inflammation and possible scarring which could interfere with the normal mobility of the sciatic nerve and produce clinical signs of adverse neural tension MOB TCD Tibial Nerve • The larger terminal branch of the sciatic nerve • Crosses popliteal fossa • Passes deep to soleus • In posterior compartment between flexor digitorum longus flexor hallucis longus • Passes deep to flexor retinaculum • Gives off medial calcaneal nerve which pierces retinaculum • Divides into medial and lateral plantar nerves MOB TCD Tibial Nerve • The tibial nerve supplies all the muscles of the posterior compartment of calf • In popliteal fossa gives off • Superomedial, middle and inferomedial genicular branches • Nerve to medial and lateral heads of gastronemii • Plantaris • Popliteus • Soleus • Sural nerve MOB TCD Obturator Nerve L2,3,4 • • • • Medial side of psoas Side wall of pelvis Obturator canal Divides anterior posterior division MOB TCD Sural Nerve • Sural nerve is joined by sural communicating from commom peroneal • Pierces deep fascia • Supplies posterior and lateral portion of calf • Lateral border of foot • Entrapment occurs most frequently in runners with a history of ankle sprain MOB TCD Sural Nerve MOB TCD Flexor Retinaculum • Deep fascia from medial malleolus to medial margin of calcaneus Anterior to posterior • Tibialis posterior • Flexor digitorum longus • Posterior tibial artery • Tibial nerve • Both give off medial calcaneal artery and nerve • Then both divide into medial and lateral plantar branches • Flexor hallucis longus MOB TCD Tibial Nerve • Gives off the medial calcaneal nerve under cover of the retinaculum • It then pierces the flexor retinaculum to supply the posterior and medial aspect of the heel MOB TCD Medial and Lateral Plantar Nerves • Tibial divides into the medial and lateral plantar nerves • They enter two tunnels separated by a fascial septum • Stretching from the calcaneus to the deep fascia of the abductor hallucis MOB TCD Medial Plantar Nerve • Passes under the abductor hallucis • Then runs on the plantar surface of the flexor digitorum longus • Dividing into its digital branches • Sensory to the plantar aspect of the medial three and a half toes MOB TCD Medial Plantar Nerve • • • • Motor to the abductor hallucis Flexor hallucis brevis Flexor digitorum brevis First or unipennate lumbrical MOB TCD Medial Plantar Nerve • Crosses the sole of the foot deep to the • • • • abductor hallucis, flexor digitorum brevis and the abductor digiti minimi To the base of 5th metatarsal Superficial to flexor hallucis longus, flexor digitorum longus and flexor accessorius Lateral plantar nerve supplies the lateral one-and-a-half toes Supplies all the other intrinsic muscles of the foot MOB TCD Tarsal Tunnel Syndrome • The tibial nerve may be compressed in the proximal portion of the tunnel before it divides • More distally, either the medial or lateral plantar nerves may be involved • Hyper dorsiflexion, external rotation and eversion can produce symptoms of tarsal tunnel syndrome MOB TCD Tarsal Tunnel Syndrome • Pain worse if foot is pronated • Tender over flexor retinaculum • Pain in heel, if medial calcaneal is involved • Pain in sole of foot if plantar nerves involved MOB TCD Tarsal Tunnel Syndrome • Orthotics may help if marked pronated foot • Anti-inflammatories • Splint at night MOB TCD Tarsal Tunnel Syndrome MOB TCD Morton’s Metatarsalgia • Depressed transverse arch in runners and ballet dancers with mobile first ray • Neuroma on digital nerve to the second cleft or third cleft Morton’s Foot morton neuroma.jpg MOB TCD Medial Plantar • Pronated foot • Depressed transverse arch at heads of metatarsals • Pain worse with tight shoes on • Relieved by removing shoes Common Peroneal Nerve L4,5, S1,2,3 • If sciatic nerve divides inside the pelvis • Common peroneal nerve pierces the piriformis • May be entrapped • In popliteal fossa • The common peroneal nerve lies between the tendon of biceps femoris and the lateral head of gastrocnemius MOB TCD MOB TCD Common Peroneal • • • • • • • • • In popliteal fossa gives off Lateral cutaneous of calf Sural communicating Superior lateral, inferior lateral genicular nerves Leaves fossa at lateral angle Crosses neck of fibula deep to peroneus longus Gives off recurrent genicular, deep and superficial peroneal Vulnerable to injury as it winds around neck of fibula Foot drop, plantar flexed, inverted MOB TCD Compartments in Calf • Nerves can be compressed in compartments • Anterior compartment deep peroneal nerve • Lateral compartment superficial peroneal • Posterior compartment tibial nerve MOB TCD Deep Peroneal Nerve • Branch of the common peroneal at the neck of the fibula • Pierces the lateral intermuscular septum to enter the anterior compartment • Supplies all muscles in anterior compartment tibialis anterior, extensor hallucis longus, extensor digitorum longus, peroneus tertius and extensor digitorum brevis MOB TCD Deep Peroneal Nerve • Skin of cleft between first and second toes • The nerve may be compressed due to anterior compartment syndrome • Muscle most at risk is tibialis anterior • Entrapment occurs most frequently in runners. It also occurs in soccer players, dancers and skiers • It occurs most often under the inferior extensor retinaculum. Repetitive ankle sprains, tight fitting shoes or trauma may also cause entrapment MOB TCD Superficial Peroneal Nerve • Runs in the lateral compartment of the calf • Between the peroneus longus and brevis supplying both these muscles • Pierces the deep fascia 10–12 cm above the lateral malleolus supplies most of the dorsum MOB TCD Nerve Supply of Dorsum • Divides 6 cm above the lateral malleolus into branches, which supply the dorsum of the foot • The first cleft is supplied by the deep peroneal • The lateral border is supplied by the sural nerve • Medial border to ball of big toe saphenous • Rest superficial peroneal MOB TCD Superficial Peroneal Nerve • Entrapment occurs where the superficial peroneal pierces the deep fascia • Particularly if there is herniation of the muscle due to fascial defects • Chronic ankle strains also stretch the nerve MOB TCD Ankle Injuries • Grade III ankle injuries have a high incidence of traction injuries to both the peroneal and posterior tibial nerves Taunton & Fricker, 1996 “BMJ Publishing Group Limited (“BMJ Group”) 2012. 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