What muscle is not innervated by the anterior interosseus nerve?

The muscle that is not innervated by the anterior interosseous nerve is the flexor carpi radialis. This muscle is primarily innervated by the median nerve, which arises from the brachial plexus. The flexor carpi radialis is involved in wrist flexion and abduction, and its innervation by the median nerve reflects its role in fine motor tasks such as gripping.

In contrast, the anterior interosseous nerve, a branch of the median nerve, innervates muscles that are key to flexion of the digits and pronation of the forearm. Specifically, it innervates the flexor pollicis longus, which flexes the thumb, pronator quadratus, which helps in pronating the forearm, and part of the flexor digitorum profundus that is responsible for flexing the distal phalanges of the index and middle fingers. The distinction in innervation patterns highlights the tactile and functional specialization of these muscles compared to the flexor carpi radialis.