The carrying angle of the elbow is formed by the relationship between the long axis of the humerus and the forearm in full extension and supination. An exaggerated carrying angle (cubitus valgus) after a childhood lateral condyle fracture most dangerously injures which nerve?

• A Median nerve
• B Radial nerve
• C Anterior interosseous nerve
• D Ulnar nerve (tardy ulnar nerve palsy) ✓

Explanation

Cubitus valgus (increased carrying angle, normally 5–15 degrees in males, 10–25 degrees in females) due to malunited or ununited lateral condyle fractures causes progressive stretching of the ulnar nerve as it passes through the cubital tunnel behind the medial epicondyle. This produces tardy ulnar nerve palsy — a slowly progressive ulnar neuropathy developing years after the original injury. Features include weakness of intrinsic hand muscles (interossei, hypothenar, medial two lumbricals) and sensory loss over the medial one-and-a-half fingers. Cubitus varus (supracondylar fracture malunion) does not stretch the ulnar nerve.

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

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Written and medically reviewed by the StethoPrep medical team.