An occasionally present accessory long head of the flexor pollicis longus muscle is called 'Ganzer's muscle'.

Frequently, the flexor pollicis longus muscle arises from the lower part of the coronoid process by a rounded bundle of muscular fibers.

The A1 pulley will then be cut with the needle longitudinally and parallel to the fibers of the tendon of the flexor pollicis longus muscle.

The upper third of the body of the bone attaches to the supinator, the flexor digitorum superficialis, and the flexor pollicis longus muscles.

This 'Pinch-Test' exposes the weakness of the Flexor pollicis longus muscle and the flexor digitorum profundus I leading to weakness of the flexion of the distal phalanges of the thumb and index finger.

The volar surface (facies volaris; anterior surface) is concave in its upper three-fourths, and gives origin to the flexor pollicis longus muscle; it is broad and flat in its lower fourth, and affords insertion to the Pronator quadratus.

It is accompanied by the palmar interosseous branch of the median nerve, and overlapped by the contiguous margins of the flexor digitorum profundus and flexor pollicis longus muscles, giving off in this situation muscular branches, and the nutrient arteries of the radius and ulna.

As might be expected, the symptoms involve weakness in the muscle innervated by the AIN including the flexor digitorum profundus muscle to the index (and sometimes the middle) finger, the flexor pollicis longus muscle to the thumb and the pronator quadratus of the distal forearm.