Rotator Cuff Tear 10 points?

My Grandfather got a surgery on his knee in somewhere around June 2010 and after the surgery he got a rotator cuff tear, his arm was fine at the check-up right before the surgery. Also after the surgery there were huge and many (and I cannot emphasis on huge) bruises on his back which were not visible before so they must've dropped him. We concluded that the nurses must have pulled hard on his arm (he weighs near 300 and is 6'0) and dropped him while moving him from a stretcher after his surgery.I believe he did not sign anything regarding that its not the surgeon's fault if anything went wrong. We contacted a lawyer and she said something can be done and his family doctor is also saying that something went wrong. How much do you think will we be able to sue them for? Will this be a big case?