naomi,

while i am NOT the doctor - to the best of my knowledge - once you cause such a damage to the sphincters - once they are ruptured - that is irreparable damage - no going back.

many of us are interested in anal play – but it is based on stretching while retaining the elasticity of sphincters and thus preventing permanent damage. i hope we will get some input from members in medical profession, because this is interesting question.