At which anatomical location does the ulnar nerve pass through the medial epicondyle of the humerus?

Explanation

## Ulnar Nerve Course at the Elbow ### Anatomical Passage The ulnar nerve passes **posterior to the medial epicondyle of the humerus**, running through the **groove between the olecranon process and the medial epicondyle**. This bony groove is the classic "funny bone" location — direct pressure here produces the characteristic tingling sensation along the medial forearm and ring/little fingers. **Key Point:** The nerve lies directly in this groove (the epicondylar/ulnar groove), where it is subcutaneous and vulnerable to direct trauma. This is the landmark used clinically to palpate and identify the ulnar nerve at the elbow. ### Cubital Tunnel — Distal to the Groove The **cubital tunnel** is formed *distal* to the epicondylar groove, as the nerve passes between the **two heads of flexor carpi ulnaris (FCU)**: - **Humeral head** of FCU (arising from the medial epicondyle) - **Ulnar head** of FCU (arising from the olecranon) - The roof is formed by the **arcuate ligament (Osborne's ligament)** connecting these two heads The cubital tunnel is the most common site of ulnar nerve *entrapment* (cubital tunnel syndrome), but the nerve first passes through the epicondylar groove before entering this tunnel. ### Why the Other Options Are Wrong - **Option A (cubital tunnel between FCU heads):** This is the site of cubital tunnel syndrome and is *distal* to the medial epicondyle groove; the nerve passes through the groove *before* entering between the FCU heads. - **Option B (carpal tunnel with median nerve):** The ulnar nerve travels through Guyon's canal at the wrist, entirely separate from the carpal tunnel. - **Option D (pronator teres):** The median nerve passes between the two heads of pronator teres, not the ulnar nerve. ### Clinical Significance **High-Yield:** The ulnar nerve in the epicondylar groove is vulnerable to: - Direct trauma ("funny bone" injury) - Cubitus valgus deformity (tardy ulnar nerve palsy) - Prolonged pressure (leaning on elbow) **Clinical Pearl:** Compression at the groove produces weakness of intrinsic hand muscles (interossei, hypothenar muscles, medial two lumbricals) and sensory loss over the medial 1½ fingers and hypothenar eminence. (Reference: Gray's Anatomy, 41st ed.; Last's Anatomy, 12th ed.)