What is this? There's actually a genre of "prison women" films... ?? Well if the genre has been propelled by the Japanese it's not surprising, and somewhat disturbing.
The film that really got the ball rolling was the Roger Corman production, THE BIG DOLL HOUSE (1971) directed by Jack (SPIDER BABY, SWITCHBLADE SISTERS) Hill. Others are THE BIG BIRD CAGE, WOMEN IN CAGES, CAGED HEAT, CHAINED HEAT (Pam Grier co-stars in a lot of these) and a slew of European WIP flicks from the awful direction of Jess Franco. The Shaw Brothers produced one of the best with THE BAMBOO HOUSE OF DOLLS in 1974. That movie had a little bit of everything--naked women, lesbianism, evil Japanese wardens, torture, blood, violence, car chase/prison break, martial arts action and a search for hidden gold.