Bilateral Perthes Disease

My Son is now 21 yrs of age and has been battling with perthes since the age of 5yrs. He has bilateral perthes. the left leg was the first and this was treated with non weight bearing, callipers and restricted activity and is now near normal, at the age of 8 it appeared in his right hip which he had a surgery ( varus osteotomy) with further surgery to remove plate and pins. He still struggled with pain and had hinged abduction and leg discrepancy. He was then given a valgus osteotomy as a salvage operation and further surgery to remove plate and pins at the age of 14. He struggled on through school still in pain. He has now grown to 6 ft and this has produced more problems as his thigh muscles do not work probably due to the position of the femur that the valgus placed it in. The ball of the femur is mushroom shaped and the main pain is directed through the knee which gives way unpredictably causing him to fall. He has been told by a specialist that he is too young for a hip replacement and to grin and bear with pain management for as long as he can. He has been able to do office work part time, but even this is painful do to the sitting position.His left leg does give him trouble from time to time. Nobody actually follows perthes up into adulthood as once you reach 18yrs you are discharged from the children's hospital and left to the care of your GP. There should be a call back system for check ups even if it was to help doctors to understand the disease. I don't know if surgery benefitted my son or if treatment with callipers was better, all I know was I could not bear to put him back in them for another 3 years and did what I thought was right at the time. Has anybody around this age experiencing similar problems ?