That's a real bugger, @Julez1958 - I had trigger finger on my regular fingers (mainly both ring fingers), but the base of both my thumbs become incredibly painful and weak (sometimes I'd drop things!) I was wearing thumb splints too, 24/7 when it was at its worst ....
Have you actually been confirmed with Carpal Tunnel? It often requires surgery. I thought it was too, but it wasn't. My GP got me to do a couple of 'extreme flexing of the wrist' exercises (holding it in that position for quite a while) and if the 'tingling' didn't happen .... it is unlikely to be carpal tunnel. I found the Medicinal Cannabis Oil helped with mine, reducing the pain level to almost zero.
My hands DO look just like this tho - with the excessive shrinkage of muscle at the base of the thumb ....

Before talking 'surgery' ..... Maybe talk to your Onc about having a break from the AI (Well done on making it to 12 months!! I only made it to 6 weeks!!) I ended up changing from Letrozole to Exemestane, which helped & since then, I went on to Anastrozole, it has diminished greatly.
take care xx