Codeigniter - 将静态页面与基本数据库CMS混合使用

Firstly, apologies if someone manages to find a similar question, I've tried looking but it's a pretty specific question.

Basically.... I have a website I've built in Codeigniter with static pages; Homepage, About Us, Contact Us, etc

The client has since asked if they can now add/manage some of their own pages. I'm too far in to think about using the likes of Wordpress or any other pre-built CMS out there hence wondering what the potential solutions are using Codeigniter.

The site has an admin section so I'm fine for building a mini CMS to create database rows for new pages along with some sort of wysiwig for the content.

My main obstacle is how do I get the pages to display. If I could nest the new pages code within a separate controller such as www.example.com/info/database_driven_slug then I know I could use the uri_segment facility to grab the page and display the content, however I need all the pages to be on the same level; eg. www.example.com/db_driven_slug.

Again, I'm assuming I can make use of the uri_segments but I have 3 questions:

1. Where do I put the code that grabs the uri_segment and checks if it exists in the database?
2. How do I stop this interfering with the already built static pages?
3. Am I being really dumb and have to use some sort of routing for this?

Thanks in advance