The 21-year-old was originally recruited by Lee Clark on January transfer deadline day
but was stretchered off 14 minutes into his debut against Derby County
with an ankle injury less than 24 hours later.
However, now back to full fitness, Blues boss Clark has once again swooped for the highly-rated youngster, who will once again wear first-team squad number five.
Accomplished on the ground and excellent in the air, Thorpe was formerly an England U19 captain before moving up to represent the Three Lions at U20 and U21 level.
The Manchester-born academy product, captained United's youth side when they won the 2011 FA Youth Cup and also led them to victory in the U21 Premier League trophy last year against Tottenham Hotspur.
On joining Blues back in January, Thorpe spoke of his excitement at the chance of gaining regular first-team football and will no doubt be looking to embrace this latest opportunity.
You can watch that original BluesTV interview with Thorpe below.