Would it be possible to determine a "risk" factor and count that in the mortality ratings, or is this too simple?
The problem might be that the statistician doing the risk adjustment doesn't have 'skin in the game', so his/her assessment of risk is worse than the surgeon's. (Although if that were the case I would expect the statistician to be just as likely to overestimate the risk than underestimate it, yet I never hear about surgeons favouring the difficult cases because they think they can improve on the expected mortality rate in such cases).