Limited unilateral instrumentation has been used in the past in the treatment of adolescent idiopathic scoliosis; however, to our knowledge, there are no reported cases with ultra-long follow up regarding this. Our objective is to report on the 43-year follow-up of limited Harrington rod instrumentation for the treatment of a double major adolescent idiopathic scoliosis curve. We describe the patient’s initial presentation, including history, physical exam, radiographic findings and clinical decision-making. Initial coronal cobb angle measurements before surgery were: 14° T1-T5, 42° T5-T12, 44° T12-L4. At 43 years of follow up, there was progression (14°>24°, 42°>70°, 44°>50°) of the patient’s double major scoliosis curve despite unilateral, limited Harrington rod instrumentation from L4-S1. The patient was treated with a T3-pelvis instrumentation and fusion and posterior column osteotomies. To our knowledge, this is the longest follow-up and subsequent revision of a patient undergoing limited, unilateral Harrington rod instrumented fusion for the treatment of a double major adolescent idiopathic scoliosis curve.