Our Ripley had this surgery years ago - I don't remember exactly when, but it was at least 8-10 years ago. She is a Pom mix, and has really shallow hip sockets. She tangled with a wheeled chair in our kitchen and dislocated her hip, and the vet was not able to get it to stay in again. She was probably around 3-5 when she had the surgery and weighed around 7lbs. She walked on 3 legs for a few weeks, but gradually she started using the 4th leg and within a couple of months you would never know she had had a problem (once all the hair on her hip grew back in

) She is now 13-14 yrs old and never seems to have a probem with it - no limping or pain indications. She has slowed down and seems a bit stiffer over all due to her age, but nothing particular to her hip surgery.
We honestly expected to have to do her other hip at some point because the sockets are so shallow the vet felt that the other one would come out at some point too, but so far we haven't had to. I would definitely do it again, if her overall health allowed for the risk (at her age now).
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Kim - Mom to Ripley, Izzy and Max
Always in my heart - Sweet Little Riley