Anterior interosseous syndrome causes impairment of which movement?

Study for the NBCOT Hand Injuries and Intervention Test. Prepare with flashcards and multiple choice questions, each question offers hints and explanations. Get ready for success!

Anterior interosseous syndrome affects the deep forearm flexors supplied by the anterior interosseous nerve, a branch of the median nerve. It specifically innervates flexor pollicis longus, the lateral half of flexor digitorum profundus (to the index finger), and pronator quadratus. Because the lateral half of FDP that flexes the index finger at the distal interphalangeal joint relies on this nerve, the ability to flex that DIP joint is lost. This is the movement most characteristic of the syndrome and is why pinch tasks that rely on tip-to-tip flexion (the OK sign) are impaired. Wrist extension and thumb opposition involve other muscles and nerves and are typically preserved. So, the impaired movement is flexion of the distal interphalangeal joint of the index finger.