I am all about education so here is a link for anyone who is interested in the growth plate closure ages at the elbow. Remember these are biological ages so they have a +/- of about 2 years on them.
Please also remember that we are concerned with growth plate micro trauma when throwing not so much with muscle strains. Those usually heal up fine with rest. Joint damage can be permanent.
http://emedicine.medscape.com/article/97101-diagnosis