Is It Necessary To Remove Interlocking Nail After The Fracture Has Healed?

my brother had met with an accident 3years back and suffered from fracture of both the bones below the knee joint. an intermedulary interlocking nail was implanted. now the fracture has healed. is it necessary to remove the interlocking nail??what are the pros and cons of removing it and leaving it as it is??please let me know in details