[Tracy and Pixie]

Pixie has been limping since jan 28th. At first I took her to a vet near my new house as I just moved and they though she just had a muscle problem or possible luxating patella. She did not improve so I took her to my regular vet a week and a half later and x-rays showed that she may have legg-perth. We repeated the x-ray on monday march 8th and it is getting worse.
The specialist that would be doing the surgery for her leg looked at the latest x-ray via email and felt that he didnt see enough deteriation from the last x-ray and suggested we wait longer and do another x-ray in a couple of weeks.
My vet thinks that we should still go ahead and do surgery next week as Pixie's leg is still lame and atrophy has set in along time ago. I agree with my vet but I'm worried that I will be making the wrong decision. Pixie's right leg is half the size of her left and I'm worried that if we put it off longer it will end up taking her longer to recover from surgery since muscle will be almost all gone.
If she is going to need surgery, sooner would be better. The way it looks is that she will need the surgery so why put it off. What should I do?