What could be the problem?

My mother has osteoporosis and fell on June ninetenth of this year. She fell forward into the seat of her walker. This caused a shoulder/chest injury. She is still dealing with alot of pain. She has had xrays, ct scans, ect and they couldnt find anything except for a few spot on her lungs. When lying flat, you can run your hand along the rib cage on top of the right breast area and there is a hard area that protrudes outward. It almost feels to me like a broken rib. I have read about ribs and so forth, but if it is indeed fractured, why not show up on xray or ct? She is in so much pain that I can hardly stand hearing her suffer. She takes hydrocodone and an occational motrin 800 mg to relieve the pain temporarily. She cannot lay on her right side for the pain and it is painful to get in and out of bed. I can imagine a blunt force trauma like falling hard against her walker seat would cause bruising and so forth, but could this indeed be a fractured rib? Any one out here been through this type of injury?