There was an article in Rabbiting On some time ago about a poor bunny who jumped into his cage clipping his leg on the way in and breaking it. Even before this, Caroline and I had talked about how we don't really like the plastic cages as bases for house bunnies because of this jumping up and through to get in, which apart from anything else bunnies will struggle with when they get older. Often they will even try to use the wire door like a ladder to climb up, which makes me feel uneasy at the thought of what could happen to toes if they slip.
I myself have a 150cm cage that I use to contain baby bunnies when I foster them for the Rescue. As they get older and I start letting them out for playtime more and more I am faced with this same problem. Here is one simple solution - bendy sticks!
Available from most pet shops and easy to hook over the entrance, they cover up the wire and provide proper purchase for little fluffy feets. And based on the speed bunnies have been flying in and out of their cage this week, I'm pretty sure this configuration has met with little fluffy approval.