Can costochondral separation cause a fever?

It should not.: It could cause inflammation which could cause an increase in temp; however, a temp is not a fever until it is 100.4 F.

It's a stretch: sure, it's inflammation and inflammation can cause a fever, but it's generally a small area. Breaking the ribcage during a bipass operation...well, it's the overall surgery but a mild elevation of temp. happens in that context sometimes. Infection, big trauma, those would be more likely