What nerve has been compressed? During a surgical procedure in which the lower abdominal wall has been opened, the retractor blades damaged a nerve lying between the iliacus and psoas major muscles. The patient has weakened hip flexion and an inability to extend the knee, as well as analgesia on the anterior thigh and medial leg.
A. Obturator B. Femoral C. Sciatic D. Tibial E. Common fibular
Femoral-the femoral nerve lies between the iliacus and psoas major muscles. so, if a surgeon pulls these muscles apart with a retractor, the femoral nerve can be easily injured. this patients symptoms match with an injury to the femoral nerve. because the quadriceps are denervated, she cannot extend her knee. the femoral nerve also innervates powerful hip flexors like pectineus, rectus femoris, part of iliopsoas, and sartorius. with these muscles denervated, she cant flex her hip well. finally, consider cutaneous innervation-the anterior cutaneous branches of the femoral nerve supply cutaneous sensation to the anterior thigh, and the saphenous nerve (which is a branch of the femoral nerve) supplies cutaneous sensation to the medial leg. this is exactly where she is experiencing analgesia. so, everything here points to a femoral nerve injury.
the obturator nerve innervates the medial compartment of the thigh-an injury to this nerve would cause weakness in adduction and medial rotation. the sciatic nerve is found in the posterior thigh-it does not innervate any muscles directly, but its branches are the common fibular and tibial nerve. if the sciatic was damaged and these two branches were lost, there would be severe motor and sensory deficits throughout the posterior thigh and the leg and foot. the tibial nerve innervates the hamstrings, the posterior compartment of the leg, and the plantar foot. damaging the tibial nerve would impair flexion at the knee and plantarflexion of the foot. the common fibular nerve has branches that innervate the lateral and anterior compartment of the leg and provide sensory innervation to the lower anterior leg and dorsum of the foot. an injury to this nerve would impair dorsiflexion of the foot, causing foot drop, and cause numbness on the dorsal foot.