Leicester prop Matt Hampson has had further specialist surgery on his spine following a neck injury.
Hampson has won four England under-21 caps
The 20-year-old was seriously injured during an England under-21 scrummaging session on Tuesday.
Hampson has been transferred to Stoke Mandeville Hospital - renowned for its spinal injury care - and underwent a four-hour operation on Wednesday.
The hospital said in a statement on Thursday that his condition remained "critical but stable."
The surgery at Stoke Mandeville aims to reduce and stabilise the fracture in the neck. Hampson should then return to Northampton Hospital for further care.
The England Under-21s' final Six Nations game against Scotland on Friday will go ahead as planned after the players consulted Hampson's family.
As tribute to the prop the team will each wear the letters 'MH' under their England Under-21 badge.
The senior England squad will donate their shirts from Saturday's Calcutta Cup clash with Scotland to a charity auction to raise money for Hampson.
England captain Martin Corry, a club-mate of Hampson's, said: "The whole of the England squad are greatly saddened by the news of the injury.
"Our thoughts and best wishes go out to Matt and his family at this very difficult time.
"Matt is a very likeable guy. He enjoys his rugby, works hard at it and his talent has already been recognised by the England Under-21 coaches.
"His injury puts everything else in rugby into perspective.
"The England team decided they would each offer their England shirt from this Saturday's game for auction.
"We hope the money raised can in some way help Matt and his family during his recovery."