What does it mean to send someone or something into a spin?I try to translate the sentence 'a discovery that has sent the medical world into spin'
To understand this figure of speech, think about what happens if you are walking along and are suddenly knocked off balance and made to spin around. What happens? You are most likely confused and out of control. This is what the figure of speech means. It means that something or someone is confused by something and is put out of control.
In the case of the medical world, I imagine that the discovery has surprised people very much. Perhaps it has proven that some idea that medical people had believed strongly is actually false. This would send the medical world into a spin because it would upset their ideas about how things work. This would confuse and upset them.
To see an example of this figure of speech, look at the story in the link below. Police in this story have been sent into a spin because kidnappers have changed their tactics. This has confused the police and left them in a state where they do not feel like they are in control of the situation. This is the meaning of your quote.