Taylor device on Shabbat

My chavrus's son is having a Taylor device to lengthen his left leg. He is trying to find out if there are any halachic considerations he might have to worry about. He was told he has to make the screws tight four times a day. Would that be a problem on shabbos? We asked a Rav who thought it might be a problem of making bleeding. Should he try to get a goy to do it for him. Thank you for your help.