When I was pregnant with our first daughter, Charlotte, I did a lot of research on baby products. I wanted to make sure what we were investing our money in was the safest for our child. I had initially registered for a Baby Bjorn carrier. After reading many reviews, however, I learned that that style of carrier may not be the best for a baby's hip development. I don't know what stuck with me, but after that I didn't feel like that was the best option for us. I ended up purchasing a Ergo carrier for Charlotte and that investment has proven to be invaluable for us given that we have embarked on a journey with hip dysplasia.
The International Hip Dysplasia Institute suggests that carriers that allow the baby to sit in the carrier rather than dangle promote a healthier position that does not cause excessive force on the hip joint.
There are lots of different styles of carriers that promote this better positioning. The ones I can think of off the top of my head would include any Mei Tai style carriers, Beco carriers, Ergo carriers and the Moby GO.
I feel content knowing that when Annabelle is NOT in her Spica, if I have her in our carrier, her hips are well supported and safe. The Ergo has also come in quite handy because I've been able to wear Annabelle while she is in her Spica. I wore her almost the entire evening after we came home from the hospital, and I use it anytime we're out shopping, since we have to take her out of her carseat, and she doesn't fit in the cart. :)
*** please note that I am not endorsed by any company to make claims, and I am not specifically promoting a specific type of carrier.