Sheridan required a procedure known as bicep tenodesis and also had a "revision operation" to correct previous shoulder surgery, which had not worked.
The drastic-sounding operation has limited Sheridan to just one game for Sale since the Six Nations - and it placed his World Cup ambitions in the balance.
Sheridan did not recover in time to feature in either of England's warm-up internationals against Wales and he had to rely on the faith of the red rose management.
Manager Martin Johnson ultimately felt Sheridan had "enough credit" in the bank to warrant World Cup selection - despite not having proved his fitness.
"They chopped the bicep," said Sheridan, who will make his comeback against Ireland at the Aviva Stadium tomorrow.
"They cut off the bit that was damaged with a pair of scissors and reattached the bicep to another part of the shoulder. The bicep tendon is shorter now - but I am still as flexible as ever!
"I also had to have what was called a revision operation because the anchors had come out from the previous op, which hadn't worked. I played with the problem but there was a weakness there."
Sheridan has also had two operations to his left shoulder since October 29, after suffering a serious dislocation during a Heineken Cup match against Cardiff Blues.
Asked whether he feared this injury would keep him out of the World Cup, Sheridan said: "Yes, definitely. When the initial 45-man squad was announced I certainly wasn't counting my chickens.
"I was just concentrating on trying to recover from a third shoulder operation in 18 months. It was quite a major operation to come back from.
"As enthusiastic as I was about the possibility of being selected for the World Cup squad, I was most keen on just getting back fit and playing rugby."
Chris Ashton, Ben Youngs and Lewis Moody were the only others to have enough credit to be selected for the World Cup without playing.
"I wanted him on the field to play before we named the World Cup squad," said Johnson.
"We tried to push his return to the second Wales game. You are always impatient to get him back quicker but we felt he had enough credit to go (to the World Cup) and to get picked this week."
Sheridan knows he needs to hit the ground running this weekend because England's opening encounter against the heavy scrummagers from Argentina is looming large on September 10.
"I am going to be pretty rusty as far as playing time is concerned so it is important just to get out and play in a physical game" he said.
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