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.