Can you name that Sci-Fi film?

Ok, here’s my latest film identification request.
I remember watching a Sci-Fi / Action/ Escape film, if I’m not mistaken with Arnold Schwarzenegger.. but not sure.).
In this film the protagonists were imprisoned in a crude, dictatorial jail. A rough Futuristic scenario. inmate friends
I just remember a scene in particular when one of the new-found inmate friends befriended by the small group, takes off his human hand (!) and slowly unfolds his natural one, unfolding an ET-like looking limb.Three long fingers (i think).
The main issue of g the film was to escape from this prison, if I’m not mistaken.
Any ideas?
Oh, by the way.. I do hope this question can continues for other users to post for unremembered sci-fi films as well.
Cheers, all..