Which set of guidelines are you referencing here and from what source? Just to clarify, in your post title you're saying 'moderate MDM' but in your question you're actually talking about 'moderate risk' which of course is only one of the components needed to meet moderate MDM.
Generally speaking, when specific diagnoses such as a fracture are given as example in guidelines, they're just that - examples to be used as a guide and not a fixed rule for how risk is to be classified. The risk involved in a given condition can vary from patient to patient due to its severity and potential for complications. Each case has to be evaluated on its own merits. As per the AMA's publication on E/M: "Trained clinicians apply common language usage meanings to terms such as high, medium, low, or minimal risk and do not require quantification for these definitions."