Spontaneous dual shoulder break/fracture

[jelebo00]

My 76 yr old mother woke up with terrible shoulder pain this morning and couldn't move or get out of bed easily. Was so painful she was almost passing out and throwing up. We took her to orthopedist and turns out she has a bad break in her right shoulder and a fracture in her left. She didn't endure any trauma or have an accident or anything. She did have a fall about two months ago, on her side, but didn't have pain then or any indications of a shoulder injury until this morning. What could this be caused by? Her bone density scans were fine recently, she has slight osteoporosis and was advised to take calcium. Anyone heard of this happening?