The intention of the present MRI report, part 3, is to collect further information on the identification of inappropriate care. In addition, relations between MRI of the lower extremities and subsequent (surgical) interventions should be evaluated.

We conducted a systematic literature search for methods to identify inappropriate use of advanced imaging. Recommendations on the appropriateness of MRI of lower extremities were extracted from the guidelines of the American College of Radiology (ACR), AIM Speciality Health, and the "Orientierungshilfe Radiologie". Relations between MRI utilisation and subsequent interventions were modelled using OECD data. Other health care systems and their refunding policies were assessed through a literature review and expert interviews.

We detected only isolated differences between the guideline recommendations. Of particular importance, however, are the differences regarding the MRI as an initial diagnostic procedure, which was most frequently recommended in the "Orientierungshilfe Radiologie".

In total, we were able to identify eight methodological approaches to detect inappropriate care. All methods have certain strengths and weaknesses. The analysis of the relations of MRI to subsequent interventions showed that, within the OECD, more knee replacements were conducted in countries with higher MRI utilisation rates. We were able to identify a series of refunding policies that could exert an influence on MRI utilisation. These indclude, for example, educational measures, decision-making aids or access control. Finland, a country with comparable quality of care and lower MRI utilisation than Austria, steers MRI use with prescription control, use of guidelines and training in the use of appropriate diagnostic examinations.

Due to the advantages and disadvantages of the methods for the determination of appropriateness of health care interventions, a combination of these methods, depending on the respective question, is to be strived for. We have shown a combination of different methods used on data aggregated at the OECD level to draw conclusions about MRI and subsequent hip and knee interventions.