You need to talk to his physicians not affiliated with the rehab facility, and see what they say. You should get all the records from the hospital, doctors, and rehab facilities. An expert would need to review them to get another opinion. Talk to a local med mal and or elder abuse lawyer.
The only way to figure out what happened is to get all the records and have them reviewed by a medical expert which can be expensive. Unfortunately, this general scenario plays out frequently. Once an elderly person has a procedure their health takes a downhill spiral that may or may not be the result of any malpractice.
My mother is 83 and in an assisted living facility. I know intimately how frail she is and I certainly can envision how your father might have dislocated his hip in bed and how it can be nonsurgically corrected esp. since it happened twice. But I am not a physician and doubt that you are and, so, I'd get competent medical advice on how the latest dislocation occurred, what its effects have been, and how to correct it.
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