Being absolutely brutally honest, I would suspect that tendonitis might be more of a problem for sax players than it is for pianists. I play piano as well and i've certainly had more pause for thought over possible hand/tendon injury on sax than i ever did on piano. Bear in mind the rather "fixed" position of the hands for sax. Good technique will help, but in playing sax you are doing something with your hands that in a way is unnatural. If you have had real problems with injury it might be worth talking to a (medical) specialist on this one.