"Dafydd broke down in training last week and a subsequent scan has revealed the extent of the problem with his left shoulder, which will need repair," said Wales team physio Mark Davies. "He has what is known as a 'loose shoulder' and a decision has been taken under the circumstances to effect a repair sooner rather than later."
Speaking on Ringer's call-up, Wales coach Gareth Jenkins said: "Jamie is replacing one of the squad's more senior players and he offers a wealth of experience in the game.
"He is a welcome addition to our squad and we are sure he will relish the opportunity to show what he has to offer in the international environment once again.
"He has been a consistent performer at regional level and now has the chance to put his hand up for selection for Wales."