I spent about an hour with the orthopedist's PA, and got my questions answered.  Surgical treatment for my osteoarthritis (specifically basilar, or thumb CMC joint) would be CMC interpositional arthroplasty.  The one-hour outpatient surgery involves removing the trapezium bone (see arrow in x-rays below), then replacing it using my flexor tendon as a graft.  Post-op my hand would be immobilized for 10-12 days in a surgical dressing, I'd spend another 3 weeks in a cast, and then I'd move up to a removable splint. At 6-weeks post-op I'd begin 4-6 weeks of physical therapy 2 or 3 times/week.  At the end of 3 months I could expect 75% healing, at 6 months 90%, and at the end of year I would reach my baseline. These x-rays of  my thumb, taken a year ago, show where the bone is rubbing against bone; that, of course, is what's causing all the pain.  

She gave me the cortisone shot (less painful than the one the doctor gave me 6 months ago) and we'll see how long this one lasts.  I don't have to decide on the surgery right now, and I'm thinking maybe I'd wait until next Fall after my birthday.  Certainly don't want to be in a cast in Arizona over the summer, and (since my deductible starts all over again in a couple of weeks) maybe Medicare would pick up more of the cost than my private insurance?

And just in case anyone is wondering about my sewing machine...

as a matter of fact it does sew much better once it's actually threaded!  So the binding is now made, and I'm working at getting it attached.  Then all that will be left to do is the hand-stitching!