Whew. Its been a long weekend and I'm no closer to answers. 

We saved Ronin from the side of a highway and found out that day his right back femur was broken. When we took him to surgery, they found SEVEN additional fractures and had to amputate. He recovered well, got his stitches out, and was transitioned smoothly into being a regular puppy (he's six months old, 40 lb rott/pitt mix). 

A week after stitches were removed,he became very suddenly lethargic and began having 'the shakes'. We took him to the vet immediately the next morning, where he presented with a fever of 105.4!! They did blood work and a urinaylsis, and came back with only an elevated white blood cell count, indicating infection, and no other information. After a day there, his fever still hadn't broken, and we were forced to move him to the Emergency Clinic overnight.

When we arrived at the clinic, Ronin was no longer using his back half, but just dragging it on the ground (noticed when going outside to pee). The ER Vet managed to break the ever in the night, took additional x-rays of his back, hip and knee, and again had no additional information. The radiologist also saw nothing in the x-rays. It was now Saturday afternoon. We took him home, with a prescription for Carprofen for pain and inflammation. Luckily he has been slowly improving, and can now stand again, wag his tail, and control his bladder. He is even taking some 'normal' steps. We switched vets, and the new vet did a physical exam and noted that he was very sensitive on his spine in the mid back. We now have additional prescriptions for 2-weeks of anti-biotics and Gabepentin to help with additional pain management and mild sedation. We still have no answers as to what caused the fever and sudden paralysis, or if he will even fully recover in time. 

Any ideas or advice on possible causes or next steps are greatly appreciated, as we have now spent $5,000 in a month on this poor baby and don't know what else to do.