Plantar Fasciitis for 3 years, tried ice, rest, stretching and PT. Wear superfeet insoles everyday. Now have pttd. Would a walking cast help

It may help. A walking cast is a non surgical treatment for Plantar Fascitis and it can be used if ice,rest,streching and others are not successful. Havivg acast can cause some weakening of muscles and one may need may need rehab PT to gain the strength back Talk to your Podiatrist if it will work for you.
MRI. If you have not had an MRI, I would recommend one. Many drs. say they don't need one. True, but I would like to know the tendon's integrity-swollen? small tear? large tear? completely torn? You can also look at the plantar fascia at the same time. Normal thickness is around 2 mm; it thickens with plantar fasciitis. Good luck. Dr. Latva.