I am sorry to hear about your problem. Leg length discrepancies are a known risk or possible complication of this type of surgery. The issue becomes the amount of the difference in lengths and whether or not there was a surgical error.
This matter should be reviewed by an attorney specializing in medical malpractice and by a competnent orthopedic specialist.
There is a 2 year statute of limitations on these claims so you should act promptly.