New York Sep 18 (IANS): The familiar papal blessing hand gesture used by popes through the centuries may have originated due to an injury to St. Peter's (the first pope) ulnar nerve, not the median nerve as commonly thought, new research has found.

The so-called "hand of benediction" gesture is a half-open hand, with the little and ring fingers remaining curled or flexed to the palm.

While recent images of Pope Francis often show him giving a thumbs up or blessing the faithful with a hand that is fully open, many past popes - and those depicted in thousand-year-old frescoes and sculptures, assumed the traditional hand of benediction pose.

"Peter, the first pope, had an ulnar nerve injury and everyone copied him," said researcher Bennett Futterman, anatomy professor at the New York Institute of Technology College of Osteopathic Medicine in the US.

"Imitation is a great form of flattery. Out of respect for St. Peter, the other popes followed with that same pattern," Futterman noted.

Running from the elbow to the pinky side of the hand, the ulnar nerve powers the muscles that allow the fourth (ring) and fifth (little) fingers to stretch away or extend from the palm.

Yet, many anatomy texts cite an injury to the median nerve, which stretches from the shoulder area through the tips of four fingers, as the cause of the hand position in the papal benediction gesture.

That assumption, said Futterman, rests on speculation that early popes were trying to make a fist but could not do so because a median nerve injury prevented the index (middle) and long (pointer) fingers and thumb from curling toward the palm.

But Futterman said papal blessings were likely intended to be given with an open hand, rather than a fist, and dove deeply into cultural, religious, and art history to support his theory.

"A fist has always been a symbol of war - it is never a positive position," Futterman said.

"No holy man would ever bless the faithful, a crowd, or followers, by making a fist," he noted.

For his next study, Futterman seeks to learn more about the disease process behind the ulnar injury.

"There is some evidence beginning to emerge that this may have been a leprosy infection affecting the ulnar nerve," he said.

The study was published in the journal Clinical Anatomy.