Explanation:
Correct Option: B. When applying an external fixator to the tibial diaphysis, the half-pins are typically placed along the anteromedial face of the tibia. This specific anatomical surface is chosen because it is largely subcutaneous and completely devoid of major overlying muscular or neurovascular structures. The primary critical structures that absolutely must be avoided, which dictate the strict boundaries of this 'safe zone', are the elements of the anterior compartment located just laterally—specifically the anterior tibial artery and the deep peroneal nerve. Pin insertion that wanders too far laterally across the tibial crest or penetrates too deeply past the lateral cortex risks catastrophic iatrogenic injury to these structures. The saphenous nerve (Option A) is medial but highly superficial and less at risk with proper blunt dissection technique, while the posterior structures (Option C) are protected by the bulk of the bone itself provided that drill and pin penetration depth is appropriately controlled under fluoroscopy. (Ref: Nayagam, Manual of Internal Fixation; Behrens and Searls, J Bone Joint Surg Br, 1986)