Morphometry of the anterior interosseous nerve: a cadaveric study

Abstract

Objectives: ​Pathophysiology and etiology of anterior interosseous nerve (AIN) syndrome are still controversial. This anatomical​ ​dissection study aimed to understand the anatomy of AIN. Methods: From a random sample of upper extremities of whole-body human cadavers (n=10), 20 upper extremities were included​ ​in the study. Two of the cadavers were females and 8 were males (age range 34–62 years). Specimens were dissected with​ ​the elbow in extension, wrist in neutral position and forearm in pronation. After superficial dissection, the pronator teres muscle​ ​was released, and the branching pattern of the AIN and the separation of the nerve from the interepicondylar line were​ ​recorded. The branches to the pronator teres, flexor pollicis longus, flexor digitorum profundus and flexor digitorum superficialis​ ​were recorded according to their distance from the interepicondylar line. Results: The AIN branched from the main trunk 5.1 to 47.89 mm (mean 37.58±11.25 mm) distal to the interepicondylar line.​ ​AIN gave off 1–4 branches to the pronator teres. The first branch left the AIN 10.05–83.84 mm proximal and entered the muscle​ ​23.49–43.72 mm distal to the interepicondylar line. AIN gave 1–4 branches to the flexor pollicis longus, flexor digitorum profundus​ ​and flexor digitorum superficialis at varying distances. The origin of the branches of AIN, as well as the innervation by​ ​one or multiple branches for a muscle, was variable. Conclusion: This study provides a detailed map of the anterior interosseous nerve innervating flexor pollicis longus, flexor​ ​digitorum profundus and flexor digitorum superficialis muscles, to serve as a guide for location of AIN block in patients with​ ​upper extremity spasticity and AIN syndrome.