During ORIF of a lateral condyle fracture of the humerus in a child, which structure must be carefully protected to prevent a cubitus valgus deformity and tardy ulnar nerve palsy?

• A Anterior interosseous nerve
• B Radial nerve in the radial groove
• C Medial epicondyle apophysis
• D Lateral epicondyle apophysis and its growth plate (cartilaginous physis) ✓

Explanation

Lateral condyle fractures in children involve the Milch classification based on whether the fracture line enters the joint or not. The lateral epicondyle apophysis is the key structure — avascular necrosis, growth arrest, or malunion leads to lateral physis damage causing cubitus valgus deformity over years, which subsequently stretches the ulnar nerve producing tardy ulnar nerve palsy. Adequate anatomic reduction (open if displaced >2 mm) and proper fixation prevent this. The anterior interosseous nerve is at risk in Monteggia fractures, not lateral condyle fractures.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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