We had an Pediatric Orthopedic Surgeon on my son's 11u team this year and he has been interviewed locally and published some papers on sports related injuries.
I asked him about the debate on curve balls at a young age. I asked him to shoot straight and not give me the "company line". He sighted the study by Dr. Andrews and said that they followed several little league pitchers for an entire season and charted all of their competitive pitches. A competitive pitch was defined as anything with a batter in the box. BP, real game, etc.
He said the findings did not show the type of pitch made a difference. In fact, different mechanics did not seem to make a difference. The study sighted the number of pitches as the single greatest determining factor in injuries to young pitchers. After 650 competitive pitches the number of arm injuries sky rocketed. Another factor that had more significance than type of pitch was arm strength. Those pitchers with stronger arms who threw harder than the average pitcher saw more injuries.
He went on to admit that there was a "company line" that Doctors follow because that is the safe road and no one wants to be labeled a crack pot or rebel in the medical field for stating the opposite of everyone else. He said as more studies are done and more information shows that pitch selection has less of an affect than pitch counts more doctors will change their tune.
The final straw for me was when he said if his son had a decent curve ball he would let him throw it in moderation.
Just passing it on...
For what it is worth, my son does not throw anything but fastballs and change ups.