
Are you sure you have the right diagnosis - I've never heard of a growth plate fracture to be honest (always learning something new) ** but what I do know is Westies, like many other of the small breeds, tend to have patella luxation which can cause them to limp - you'll often see Jackies doing a couple of paces, and then hop. There is surgery to correct this - so the patella sits in the groove better but it doesn't always work as well with some, as with others. And I'd not rush into surgery - I had one of my Bassets who went down some back steps too fast (my fault) and came up limping. My then vet said patella and booked her in for surgery. I rested her off (can't remember if she had anything like Metacam), took her in for the surgery and was surprised to have a call back saying he'd palpated the area again and felt it didn't warrant him doing surgery after all. She stayed sound ever since.
Your dog is young and I'd, with rest and if needed, pain relief, let him get a bit older before pitching in for surgery to be honest. But I'm no vet, and you have presumably seen the x-rays etc.
** I googled and found this article, amongst others ....
http://www.vetsurgerycentral.com/growth_plate.htmMy current Basset had premature CLOSURE of the growth plates, ulna, both sides, which has left him with a bit more 'turn out' than ideal with his front legs, but at least they are even!! This is known in my main breed.