Why are surgical access, surgical urgency and procedure not included in the risk adjustment?

The aim is to adjust for patient factors which reflect frailty of the patient and which cannot be influenced by the provider, so that apart from random variation, any remaining differences in outcomes between providers should reflect differences in quality of care. Providers have influence, to some extent, over the type of surgical procedure, the surgical urgency, and whether laparoscopic techniques are used, and these factors should not, therefore, be adjusted for.