This is a good work aiming at predicting outcome following AAA surgery. The number of parameters used is large (49) but probably should anyway be available in any good quality vascular database. 

The Score: 

the calibration of this against other predictive models is shown in ROC curve:

This is quite good scoring system.. the main issue lies in the ability to apply it to practice; plus the cases were missing values exist … and of course how much this is going to add to the decision making … 

It is also not unreasonable to say that the more factors you use, the better prediction you get … but practical life does not allow that … also, there are certain factors (duration of operation, wound class, etc.) that cn only obtained AFTER operating, not before … all make a scoring system like this not usable in decision making, but rather in (maybe) validating the performance of a unit/surgeon against others, after adjusting to risk (using the score). This is an important part of any quality assurance program in fact, and have certainly a role in current AAA practice.