Twin Baby Hurts Leg in Carseat Carrier

Yesterday, the twin baby boy injured his leg because he's gotten too big for the carseat carrier, the one that snaps into the car base. His legs are too long, so when the twin twin father put the carrier into the base, the twin baby 's leg was turned just the wrong way. He cried only for a second or two, and we checked his legs to make sure they weren't broken.

So I went out and bought carseats today. It is for 22-100 pound children, and we're not supposed to use them until they're one-year-old, so what do we do? Do we wait to use the new carseats until the end of Jan when they are one and risk hurting their legs again?

I decided we need to use the new carseats so I put an ad up on craigslist for the carriers.