Was this the right thing to do for my dog?

5th of june 2011 Here is our story: It was a normal Sunny day In Florida I was taking my little girl emma (she is 2 on Monday ) Out for a walk with my Dog Cookie ( a st Bernard mix German shephard) ( I got cookie the same day as my daughter was born to celebrate so he is about 7 months when i got him) I went into a shop with Emma and tied Cookie to a lamp-post outside because he alwase sits and waits. So i got Emma a ice-cream and when i Before i got out the door i heard a thump! Must just be a bin nocking over i thought to myself But when i got outside a woman was holding my dog in her arms "I seen a man let him off the leash and the man ran away" the woman said the dog must have got scared and he just bolted out infront of my car im sorry i'll pay the vet bill she said It's fine i'll pay it you go home! I snapped i never meant to i was just upset. The woman walked away. I phoned my husband to tell him to come and get emma because The shop keeper said i will look after her untill your husband comes. Thankyou so much i said and rushed to the vet witch was just around the cornor. My poor almost 3 year old puppy was whimpering and bleeding badley his eye was bloodshot And the vet said he had broken ribs. I think he's going to make it a vet shouted! I was reilived. We just need to take 1 more x-ray to see if everything is in tip-top shape he replied. So he went with my preciouse Dog into the x-ray. He came through. "Im afraid i have some bad news he said softley. We tok the x-ray and everything was fine but i looked at his spine and his legs there was a big crack in theme. Theres nothing we can do If we do surgery the chances are he will die theres only a 50% chance he would make it. The Only kind thing we could do is put him to sleep or since he's a young dog he might make it through the surgery. It was up to me But i decided since i loved my pup so much i would put him though the surgery since he had a 50% chance. So he was whisked off for emergancy surgery. I waited in the waiting room And it was good news he had made it! He had to stay in hospital for 3 days and then i could come back and take him home. So three days later i went To pick him up as soon as he seen me he came rushing over and gave me a massive lick! My pup's Leg was in bandages with cute paw prints on them and he had a special leash that you put over his back wich was the only lead i could use now. He would alwase live with a limp and has a risk of arthiritus when he is older. He still has his bandages on he has to keep them on for 6 months. Now that you have heard my story was this the right thing to do because he will have to live like this for many years to come. He also has to eat special dog food because he can't digest properly and he has to take vitamins in his water and you have to hide pills in his food after the accident. Did i make the right choice by giving him a chance or should i have put him to sleep? Please help me?