I personally would re-phrase the sentence, as your focus is on the result which you are trying to express namely
I analysed different nonoperative management practices and all of them showed worse outcomes than surgery.
Then I would suggest
Nonoperative management practices are unable to disprove the superiority of surgery.
However looking at this I would suspect that the answer cannot be true. Unless you relate the answer and the objective of the originator. (which I can only guess at).
Example
Nonoperative management practices are unable to disprove the superiority of surgery in this case
Nonoperative management practices are unable to disprove the superiority of surgery with regard to the management of blunt force trauma to the spleen
disprove
verb [ T ]
UK /dɪˈspruːv/ US /dɪˈspruːv/
to prove that something is not true: