What is the burden of proof for a plaintiff who refuses to undergo surgery that has a 70% chance of success?

In Janiak v. Ippolito, the plaintiff refused to undergo spinal surgery that had a 70% chance of success according to the orthopaedic surgeon. The court concluded that it is for the trial judge to determine if that refusal was reasonable. It further stated that the burden of proof that a plaintiff could reasonably have avoided some of the loss claimed is on the defendant. The onus also includes establishing the extent to which the loss would be avoided or the amount by which the loss would have been reduced. This latter part of the onus on the defendant is certainly an easier task where experts give specific percentages of success or failure in surgery. But this part of the onus must be tempered somewhat where precise quantification is impossible. The Thin Skulled Plaintiff