After being admitted for a hip operation, medical staff opened up the woman's healthy hip on the operating table.
They then quickly realised that they were meant to treat the other hip.
They were able to patch up their mistake and complete th
e operation.
But the woman, who we cannot name for legal reasons, has been left with scars from the blunder.
Representatives from the University Hospital in Coventry have met with the family and apologised for the mistake, which they said was down to 'human error'.
The family involved did not wish to make any comments to the Advertiser.
Medical Director for University Hospitals Coventry and Warwickshire NHS Trust, Richard Kennedy, said: "We apologise wholeheartedly (to the patient) because regrettably a human error resulted in the wrong hip being opened for surgery.
"No damage was caused to the function of the hip and during the same operation the correct hip was operated on successfully.
"However, (the patient) has been left with an unnecessary scar.
"We have comprehensive checking processes in place in our hospitals but in light of this serious error we have reviewed the processes and reinforced to staff the importance of following them in order to prevent this happening again.
"Once again we apologise to (the patient) and her family for the distress this has caused."
