Paraphrasing liberally from the study, looks like it wasn't used as a medicinal herb in the past, but recreationally.

I'm assuming that's because opiates and alcohol use were widespread, and those are stronger analgesics and anesthetics than cannabis. For anxiety, tobacco was the preferred drug.

That does put a question on the whole modern medical cannabis industry. But of course, cannabis today is much stronger, so who knows? I don't think I could survive an amputation on modern cannabis alone, however. Or even ignore lancing a blister.