1. The Abductor pollicis longus muscle is innervated by the posterior interosseous nerve, which is a continuation of the deep branch of the radial nerve after it passes through the supinator muscle

2. Abductor pollicis longus muscle (Musculus Abductor pollicis longus) Abductor pollicis longus is a muscle found in the posterior compartment of the forearm.It is one of the five deep extensors in the forearm, along with the supinator, extensor pollicis brevis, extensor pollicis longus and extensor indicis.