My father is having frozen back & I really have no idea bout this. Can someone enlighten me and how does my father got this? He's 59 and a driver

Back. Do you mean chronically stiff spine or arthritis with rigid spinal column? If usual measures like warm packs, liniment, nsaids like ibuprofen,physical therapy,muscle relaxants don't help, have him consult an orthopedic surgeon or rheumatologist for evaluation and treatment.