My understanding is that it's not necessarily hip problems, but spine problems. Here's an article that addresses it. Carriers like the Ergo put the baby in more of a sitting position, which distributes the baby's weight more evenly rather than concentrating all the weight on the spine.
Personally, I asked my pedi about Bjorns and she recommended against them for the reasons I mentioned above.
As anything, it's totally up to your discretion.