Gross Anatomy-Innervation of the Posterior Compartment

Question 1

Describe the Innervation of the Tibial n

Answer 1

• Tibial n. –
o L4-S3
o Larger of two terminal branches of sciatic n.
o Medial sural cutaneous n. –
 Joins with sural communicating branch of common fibular n.
• Forms sural n.
o Supplies skin of lateral and posterior part of inferior 1/3 of leg and lateral foot
o Passes between 2 heads of gastrocnemius m.
o Supplies all muscles in posterior compartment of leg
o Passes posterior to medial malleolus between tt. of FHL and FDL

o Terminates as:
 Medial plantar n.
 Lateral plantar n.

Question 2

Describe and Injury to Tibial n. in Popliteal Fossa

Answer 2

• Uncommon
o Protected deep in popliteal fossa
• Severance of tibial n.:
o Paralyzes flexor mm. in leg
o Paralyzes intrinsic mm. of plantar foot
o Sensation to sole of foot is lost
• Unable to plantarflex foot or flex their toes

Question 3

Describe an Injury to Tibial n. at Ankle and its effects.

Answer 3

• Injured with trauma to or around medial malleolus
• Results in:
o Loss of intrinsic mm. of plantar foot
o Sensation over sole of foot

Question 4

Explain an Injury to Common Fibular n. and what are its effects in general and on gait, eccentric contraction and sensation

Answer 4

• Most commonly injured nerve in lower limb
• Due to superficial position as it winds around fibular neck
• May be severed during fracture of fibular neck or stretched with knee dislocation
• Severance results in:
o Flaccid paralysis of all muscles in anterior and lateral compartments of leg
o Loss of dorsiflexion causes “footdrop”
o Further exacerbated by unopposed inversion of foot
o Makes limb too long
 Toes will not clear the ground
• May employ different gaits to accommodate:
o Steppage gait – extra flexion at hip and knee raise foot to keep toes from hitting ground
o Waddling gait – leans to side opposite long limb, hiking the hip
o Swing-out gait – long limb is swung out laterally (ABD) to allow toes to clear
• Eccentric contraction also lost
o Ability to control foot being lowered to the ground
o Results in distinctive “clop”
• Sensation lost to anterolateral leg and dorsum of foot

Question 5

What are Varicose Veins and how are they formed?

Answer 5

• Affects women more than men
• Can affect great saphenous v. or any of its tributaries
• Normally, valves allow blood to flow toward the year while keeping it from flowing away
• Valves become damaged (incompetent) and no longer function properly
o Blood flows inferiorly and vein becomes dilated (varicose)
o Also become thick and rope-like
• Symptoms:
o Pain
o Swelling
o Restless leg
o Burning, itching skin
o Phlebitis
o Skin ulcers
• Treated using endovenous laser or stripped

Question 6

Describe the condition of** Deep Vein Thrombosis (DVT)**

Answer 6

• Occurs in one or more deep vv. in lower limb
• Thrombus is a clot
• Characterized by swelling, warmth and inflammation/infection
• Caused by venous stagnation
o Due to:
 Incompetent fascia that fails to restrict muscle expansion
 External pressure on veins
 Muscular inactivity
• Large thrombus may break free and travel to lung
o Pulmonary embolism
o Large enough, may block off pulmonary a. and cause death