A patient has foot drop after total hip arthroplasty. Intraoperative stretching of the sciatic nerve most often damages which division, producing selective weakness?

• A Tibial division equally with common peroneal division
• B Common peroneal (fibular) division preferentially, because its fibres are more taut at the hip ✓
• C Tibial division preferentially, because the tibial nerve is closer to the acetabulum
• D Superior gluteal nerve, not the sciatic nerve

Explanation

Although the sciatic nerve travels as one structure in the thigh, its two divisions have different tethering points: the common peroneal (fibular) division wraps around the fibular head and has a relatively fixed course from the sciatic notch to the fibular neck, making it more susceptible to traction injury. In THA, excessive leg lengthening or posterior retraction preferentially stretches the common peroneal fibres, causing foot drop (dorsiflexion and eversion weakness) with preserved plantar flexion (tibial division). This is the most common nerve injury complication in THA.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.