This study respectively evaluated 12 young children with progressive curves who underwent subcutaneous rod instrumentation (SCRI) without fusion and were followed until definitive surgery. The mean curve Cobb angle was 58 degrees at the time of SCRI. The mean apical vertebral rotation at the time of presentation was 20 degrees. Curves were observed to have progressed to an average of 59 degrees before definitive surgery and were corrected to 34 degrees with instrumentation. The average apical vertebral rotation was found to be 34 degrees before the definitive treatment. This value was significantly larger than the pre-SCRI value (P = 0.002). The average number of lengthening operations per patient was 4.6, and the number of all operations per patient was 7. Six patients developed complications. The average time spent in hospital was 101 days. The findings demonstrate that the curves were essentially unchanged in the frontal plane during the period of lengthening. The sagittal curves remained mostly within normal limits, but there was an alarming increase in rotation.