Positioning Nerve Injury — FRCA Final MCQ
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Correct answer: B — Common peroneal nerve
The correct answer is B, the common peroneal nerve. It passes superficially around the fibular neck at the lateral aspect of the knee and is therefore vulnerable to compression by leg supports in the Lloyd Davies or lithotomy position. Injury may produce weakness of ankle dorsiflexion and eversion, causing foot drop, with sensory disturbance over the anterolateral leg and dorsum of the foot. Padding should prevent direct pressure over the fibular head. The sciatic nerve is more proximal and is principally endangered by excessive hip flexion or stretch. The tibial nerve runs through the popliteal fossa rather than superficially over the lateral fibular neck. The femoral and obturator nerves are situated proximally in the pelvis and upper thigh and are not compressed at the lateral knee.
Reference: Royal College of Anaesthetists. Nerve damage associated with an operation under general anaesthetic, fifth edition 2017, revised 2019. https://www.rcoa.ac.uk/sites/default/files/documents/2019-11/11-NerveDamageGAweb.pdf