Surface Anatomy of the Forearm as a Roadmap for Posterior Interosseous Nerve Release: Surgical Relevance and Clinical Correlation

Purpose Surface landmark–based mapping of the posterior interosseous nerve (PIN) to provide a detailed anatomical understanding that can guide effective surgical interventions for PIN compression syndrome on ratio-based measurements. Methods In this study, upper limbs from 15 adult cadavers were dissected. With the forearm in pronation, the lateral epicondyle to radial styloid line (LR line; distance a ) and the lateral epicondyle to the ulnar styloid (LU line; distance b ) were marked as surface reference lines. The PIN was identified between the brachioradialis and extensor carpi radialis longus muscles, and distances from the lateral epicondyle to its entry ( c ) and exit ( d ) points from the supinator were measured, along with the intramuscular travel length ( Tr ). Ratios a/c and b/d were calculated. Results Mean distances were: a 24.54 cm, b 22.82 cm, c 4.26 cm, d 8.54 cm, and Tr 5.83 cm. The mean a/c and b/d ratios were 5.76 and 2.67, respectively. PIN entry and exit points are consistently projected near the LR and LU lines. Conclusion Ratio-based surface mapping is a practical technique for estimating PIN location in forearm peripheral nerve surgeries. However, additional validation in actual patients is needed.