Is there a case that holds it is not necessary for an expert to rule out all possible causes of injury before being allowed to testify a defendant’s negligence is the cause of injury?

Answer: Smith v. Hines, 2011 OK 51:

15 The neurologist noted that prior to the surgery there was nothing wrong with the movement or nerves in the patient's thigh but after the surgery there was femoral nerve damage.13 He stated that it is "more probable than not" that the injury developed during the surgical procedure and except for the complication of the surgery she would not have developed a left femoral neuropathy.14 Nevertheless, he also noted that he would require additional information before the cause can be determined with certainty.15

16 In Robinson v. Oklahoma Nephrology Associates, Inc., 2007 OK 2, 11, 154 P.3d 1250, we explained that:
. . . Our case law requiring a medical malpractice plaintiff to produce evidence that injuries were caused by a particular physician's negligence has never required the production of experts who will utter a particular magic phrase, but focused instead on the particulars of each case. While the plaintiff must present evidence to remove the cause of her injuries from the realm of guesswork, she need not establish causation to a specifically high level of probability merely to withstand a demurrer to the evidence. . . Absolute certainty is not required.16

(Citations omitted.) (emphasis supplied.)