Yep, most things are multifactorial...surgical care processes certainly are

From the JAMA article "Adherence to Surgical Care Improvement Project Measures and the Association With Postoperative Infections":

Our results are consistent with previous findings regarding public report of process-of-care quality data. Based on our findings, the individual item performance rates reported publicly do not fulfill their stated purpose of pointing consumers toward high-quality hospitals. However, when taken in aggregate, improved performance on our global all-or-none composite measure is associated with improved outcomes at the discharge level. Therefore, while the individual items may not imply quality differences, the overall ability to demonstrate adherence to multiple SCIP processes of care may. Improved methods for identification of quality of care are necessary to be able to define improvements in patient outcomes, and to justify the massive investment of time and money in tracking these processes of care.

Click here to access the JAMA article.