Amos – who was making his 100thappearance for the region - was taken off in some discomfort in the second half in Dublin.
And Head Coach Bernard Jackman revealed after the game that the 23-year-old wing was now set for an enforced spell on the sidelines.
“Hallam has got a dislocated elbow, it went back in at the time, which is positive, but it looks like four to five weeks,” said Jackman.
“Hopefully him and Tyler Morgan (hamstring) will be back around the same time. It makes our outside backs cover a little bit light.
“It’s a huge blow, he is a big leader for us. We didn’t get enough ball to him while he was on the field but he is one of the players we know can threaten, him and Jordan Williams are a dangerous combination.
“But if it’s four or five weeks that is a positive result for us given that it is a dislocation.”
Jackman will now look at his wing options and admitted young Jared Rosser could force his way into his plans after his try-exploits as Dragons A secured a big win over Connacht Eagles at Ystrad Mynach on Saturday.
“He is one of the players that we developed really well last year,” said Jackman. “He had a good game in his first game back against Cardiff Blues in the Celtic Cup and five tries would lead me to believe he was decent!”
