I did not find any class action lawsuits regarding titanium cages for back surgery. I did find articles that describe the procedure as having widely varying results with the variance being attributed to the skills of the surgeon and the overall health of the patient. Smokers have a worldwide failure of 40-60%. Non-smokers have variable results, ranging from "awful" (I guess this is a new medical term) to having improved the patient's condition.
Without evidence that the surgeon knew or should have known his/her skills were not adequate or untreated post-op problems apparent on examination or diagnostic film, I must agree that this is a bad result, not malpractice (or the new term being used in healthcare, "medical mismanagement").