very sorry to hear mate
most people will know my car got run over not long ago and the driver didnt stop then.., he was in a veryy bad way, had to go under the knife twice to have his pelvis bolted back together, then bolted back onto his spine, also his back legs wer both broke...and was in the vets for a weeks...
hes now home, but stuck in a cage, and got to let him out for a walk around the house 3 times a day to get the feeling back in his legs, as when we found him it reminds me off when you said your cat was dragging his back legs.....
but im so sorry for you mate i realy am!