BaseballmomCEP,
My belief is more information is better, especially as information on the question you posed continues to develop and evolve.
Here is a link to a recent survey/study done through some University of North Carolina folks/researchers, on the issue:
http://college.unc.edu/2011/10...ith-your-arm-intact/Through the surveys and responses, the one pitch reported to show an elevated risk of injury was/is: the slider.
"“Kids who threw the slider were at three times the risk of getting injured,” Register-Mihalik says. They reported more pain more often than other pitchers. One reason could be the mechanics necessary to throw a good slider. It requires a more violent arm motion; it’s like a combination of a curve and a fastball. “And that means it’s a more risky pitch than a curveball, especially for kids at a young age when their muscles and bones are not fully developed,” Register-Mihalik says. Yet her surveys revealed that not many Little Leaguers throw sliders. And kids who don’t throw curveballs or sliders still get hurt. Some even develop tendinitis."
In addition to the slider, the other two major risk factors for injury were identified:
"high pitch counts and pitching too often."
Since the study is based on surveys, it might create more questions and also be subject to criticism by the "nay-sayers."
Since it does address quite specifically the question you asked, I thought it might be helpful for you.