I can highly recommend Prof. DR Greta Dereymaeker in Leuven, Belgium . She is an orthopaedic surgeon who specializes in feet . Did a wonderful job on me last year , which involved some reconstructive surgery after a certain London hospital messed me up 3 years ago. She works in a small private hospital, but I have heard that she also travels abroad, I know she used to operate in USA. You can find lots of references about her on the internet.
Leuven is only 30 min. by train from Brussels and if your friends ever want to travel let me know, I can ask my friend who lives there to find a hotel or B&B.
The phone number for that hospital is 00 32 16 209 312 then ask for orthopaedic department, they speak English .