These are the biceps, triceps and supinator reflex. The m. supinator and m. brachialis function is a prerequisite for this surgery. Its upper third gives insertion to the supinator muscle. The biceps brachii during the elbow flexing phase is a stronger forearm supinator. The deep branch then becomes the posterior interosseous nerve upon exiting the supinator muscle. An ectepicondylar foramen is formed from the supinator process and ectiepicondyle. The supracoracoideus is the second largest and is the primary elevator and supinator. Supinator&colon; originates on the lateral epicondyle of the humerus and inserts on the radius. The abductor pollicis longus lies immediately below the supinator and is sometimes united with it. A supinator turns the palm of the hand up; a pronator turns the palm down. Supination strength decreases by 64% if supinator is disabled by, for example, injury. Encircling the radius, supinator brings the hand into the supinated position. Supinator always acts together with biceps, except when the elbow joint is extended.