Like in the car example, repair or cure may not be enough, and the patient ought to insist on restoring his health. Following my treatment your health will deteriorate by ten units. The patient may accept this offer, or look for another physician with a better one. After treatment is over, the patient might measure his health and if it does not match the agreement, he may sue his physician. With such a health measure at hand, relying on ethics may not be unnecessary.
Medicine defines health as non-disease, and cure, as disease elimination.
Yet health is more than that, it involves also performance. When specifying his agreement with the physician, the patient ought to demand a cure with the best health outcome. This health definition is akin to the patient's perception of health. He cares less about the disease itself, or its cure, he just wants to feel healthy again. Many legal and ethical difficulties result from ignoring how treatment affects health.