The state Medical Examining Board imposed fines ranging from $2,000 to $7,000 on three doctors Tuesday, including $5,000 against a Greenwich neurosurgeon who operated on the wrong disc on a patient’s spine in 2011. Dr. Mark Camel, who is affiliated with Greenwich Hospital, discovered his error during spinal surgery on Oct. 27, 2011 and then operated on the correct disc. State investigators found that Camel admitted that he had written down the wrong spinal location during a pre-operative visit and neither he nor the patient noticed the error when signing consent forms, records indicated. When Camel was reviewing an MRI and preparing to close the patient, he noticed his mistake. Camel immediately reported his error and has put in place protocols to be sure such an error never happens again, records show. It was the second time in two months that the board had taken up “wrong site” incidents at Greenwich Hospital.