To clarify whether or not VBT has been done on adults - yes, it has (at least once to my knowledge) been performed on a 50 year old woman. Her slightly older sister is now scheduled for VBT as well (patient #1 joked that she will no longer be the oldest VBT patient!); the procedure was performed almost a year ago by Drs. Antonacci and his team at the Institute for Spine and Scoliosis in NYC.
With regard to skeletally mature patients (meaning late teens and early 20's), I will separate them from "adult" patients for purposes of this post. The team at the Institute has performed VBT on several skeletally mature young adults, as has Dr. Braun at Dartmouth Hitchcock in NH; and on very select patients Dr. Hoernschmeyer at Missouri Women's and Children's Hospital. In addition, we just learned recently from Dr. Baron Lonner, also in NYC, that he is performing VBT on skeletally mature patients as well.
There is also one surgeon in the UK (Dr. Bernard) who will consider VBT on skeletally mature patients, and he has performed at least a few such surgeries.
I am sure we will hear of more surgeons following suit at some point but that's what we know at this time.
If anyone would like to learn more, we have a very comprehensive body of information regarding VBT on the FB group below, including a list of surgeons in the U.S. and around the world who are performing VBT. There are also over 1,100 members, many of whom have VBT experience that they are willing and happy to share with others, to try to help and support them.
https://www.facebook.com/groups/ScoliosisTethering/