The 19-year-old speedster had been in fine form for his club this season, making 15 appearances, and notching two tries against Zebre in October.
Capped by Wales last Autumn, the teenager was due to be included in his country's Under-20 squad for the Junior World Championships in New Zealand this summer only to be pulled out to feature in the May 30 trial match preceding the naming of the 31-man senior team to take on South Africa.
However after suffering heavy blows to his shoulder against the Ospreys and Treviso in the RaboDirect PRO12 run in, he has now undergone surgery, leaving him looking ahead to the new season rather than a summer of rugby.
"It's a big disappointment and is frustrating because my shoulder feels fine but the scan showed I've torn quite a lot of my labrum," Hallam told the South Wales Argus.
"If I have the op now then I should be back for the Dragons around the start of the season.
"I'm disappointed but now my ultimate aim is to have a good season with the Dragons and force my way into the World Cup squad."
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