Just want to ask about magnetic rod lengthenings and on average how many are you supposed to have per year. My daughter is 7 and had her operation last July, since then she has had a lengthening in January and is having another next month, which means twice a year. I know they only do a few mm but at this rate she will not grow much during the year! How do the doctors know when to lengthen these rods?? Any advice/comments appreciated! Also she had her op at BCH under Mr Marks and they have now transferred me to Manchester (because its closer for me)for future lengthenings, even though manchester have not yet done any magnetic rod ops.