After the Hellraiser series left theaters, never to return.. Inferno would come out some years later, straight to video. However, it's hard to say what inspired this movie, as it feels nothing like a Hellraiser film. Instead, it's kind of a psychological horror murder mystery, and in fact, could easily work without Pinhead or any reference to Hellraiser at all. Probably because that's how it was (blog post) originally written... they just slapped Pinhead in there and viola! 5th film! Oh dear...
Source: Hellraiser Inferno Movie Review - Decker Shado