Boy With a Bump on His Elbow

A 10-year-old boy injured his left elbow during football practice. He subsequently had pain with normal range of motion of the elbow. He had minimal tenderness over his olecranon but no joint swelling, bruising, or palpable mass. He denied tingling or numbness of his fingers. His left shoulder and wrist showed no signs of injury. Distal neurovascular status was normal.

Routine anteroposterior (left) and lateral (right) radiographs of the left arm revealed a beaklike projection of the distal humerus. There was no fracture or dislocation.What is your diagnosis?

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