A 28-YEAR-OLD WOMAN UNDERGOES EXTENSIVE LAPAROSCOPIC SURGERY IN THE LITHOTOMY POSITION. SHE PRESENTS AFTER TWO DAYS WITH UNRESOLVED RIGHT-SIDED FOOT DROP AND PARAESTHESIA OVER THE CALF AND DORSUM OF THE RIGHT FOOT. DAMAGE TO WHICH NERVE IS THE MOST LIKELY CAUSE

• A. Common peroneal ✓ 
• B. Femoral
• C. Ilio-inguinal
• D. Lateral cutaneous of the thigh
• E. Obturator

The most likely cause of the unresolved right-sided foot drop and paraesthesia over the calf and dorsum of the right foot in this case is damage to the common peroneal nerve. The common peroneal nerve, also known as the common fibular nerve, is a branch of the sciatic nerve that provides motor innervation to the muscles on the anterior and lateral compartments of the leg, as well as sensory innervation to the skin on the dorsal aspect of the foot.

In a surgical setting, compression or damage to the common peroneal nerve can occur due to various reasons, including prolonged compression against hard surfaces, excessive stretching, direct trauma, or positioning during surgery. In this scenario, where the patient underwent extensive laparoscopic surgery in lithotomy position (legs elevated and flexed at hips), there might have been pressure exerted on the common peroneal nerve leading to its injury.

The symptoms described by the patient – foot drop (inability to dorsiflex the foot) and paraesthesia over the calf and dorsum of the right foot – are characteristic of common peroneal nerve injury. Foot drop results from weakness or paralysis of the muscles responsible for dorsiflexion of the foot, which are innervated by this nerve. Additionally, sensory disturbances like paraesthesia can occur due to altered sensation in areas supplied by this nerve.

Therefore, based on the clinical presentation and circumstances described, damage to the common peroneal nerve is most likely responsible for these symptoms in the patient.

In other words, the common peroneal nerve is susceptible to injury during surgical procedures due to its superficial course around the fibular head.

In the lithotomy position, patients are placed on their back with their legs flexed, abducted, and externally rotated at the hips. This position can put pressure on nerves in the lower extremities, including the common peroneal nerve, leading to potential injury during prolonged procedures.