In 1990 movie "Darkman", after the protagonist is seriously injured, he is put on some rotating machine, as the other patients of the hospital.
What are these machines? Are these things really used to treat burned people?
It is a rotating bed.
It is definitely not an SF prop, it is used in hospitals for patients with limited mobility to reduce the risk of creating pressure ulcers (warning, pretty graphic), aka bed sores. In normal case, healthy human keeps moving around in bed, hence the body pressure on the skin (especially on bony parts) is not prolonged, but in the cases when a patient has no mobility (and in the "Darkman", the titular character was in an induced coma), the whole body needs to be rotated to keep changing the pressure points.
The same bed as you can see in the background has been used by the main character of the biographical movie "Born on the 4th of July"
When the person can be safely moved, this job is usually done by nurses, who change the patient's position every few hours. In the case of the Darkman, who suffered from an extensive burn, it would be a bad idea, since the movement could cause further damage to the burned skin; in the case of "Born on the...", the patient had a complicated bone fracture and was at risk of losing his leg.