annie
I once broke a rib by hiccuping too hard. The rib cage is expandable to accommodate the breathing(lungs and diaphram). I do not believe it is unusual to have a rib break from a terrible cough. Coughing really bad stresses out the ribs. you are trying to take in air and your body is coughing out air...it is a mini battle between in and out. If you are really concerned you can have blood tests and bone density tests to see if there is more of a problem. happy healing.