"What can be done to lessen the risk of a second fracture resulting in an even more devastating injury? "
Dew,
Condolences on your father's fracture and fall. This type of problem, sadly, is par for the last few holes of life as we live longer and longer past 80. My own father just had surgery for aortic aneurysm. While the surgery for both of our fathers was, technically, a success, everything depends on the recovery. Avoidance of complications, and what the event does to alter the attitude toward life itself are all important determinants of the outcome. Unfortunately, very often, this type of event, however "treatable" somehow causes other fragile systems to fail and life force to wither.
I suggest you don't trust what the medical team tells you and ask your father yourself why he fell. If the hip just gave way, and caused the fall, then there is good reason to worry about the other hip failing in the same way. In that case, preventive measures are very important, in my opinion. However, if it was a slip or other understandable accident, then you can relax and not worry that the other hip is what is going to affect his life.
I see many examples of vital nonogenarians who breeze thru hip surgery and end up surprisingly close to their prior level of functioning. It's kind of like replacing the muffler on an old Buick----well worth it if the body is otherwise OK.
Regards,
Urche