If a surgery is not successful, does that mean I have a medical malpractice case?

Not necessarily. Surgeons and doctors cannot guarantee a good result despite the advances in science and medicine in the 21^st century. The practice of medicine can be both an art and a science which requires a doctor to use their judgment at times to determine courses of actions which may all be within the standard of care. An unsuccessful surgery or procedure is considered medical malpractice if a particular action or inaction of the doctor caused your injury and satisfies the above elements.