This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Humerus Fractures, Subject name: Orthopaedics
Tardy ulnar nerve palsy is seen in: 
Select and explain. 
A. Cubitus varus, B. Cubitus valgus, C. Genu varus, D. Genu valgus
B: Cubitus valgus
Answer: B: Cubitus valgus 
Explanation: Ref: Apleys System of orthopaedic and fractures, 9th edition, page 761 to 763.Explanation:Tardy Ulnar Nerve PalsyIt refers to the nerve involvement, gradually over a period of time, not immediately after the primary injury.This is demonstrated in the Cubitus Valgus deformity that complicates fractures of the lateral condyle of the humerus resulting in damage to the lateral half of the distal humeral epiphysis.This causes an increasing valgus of the elbow during growth which gradually stretches the ulnar nerve medially with a late ulnar nerve involvement.