Should the upper end vertebra be selected as the upper instrumented vertebra in patients with Lenke type 5C adolescent idiopathic scoliosis?

Study DesignRetrospective studyPurposeThe upper end vertebra (UEV) is often selected as the upper instrumented vertebra (UIV) in patients with adolescent idiopathic scoliosis (AIS) with Lenke type 5C curves; however, the effect of adjusting UIV selection one level toward the cranial side (UEV+1) is unknown. Therefore, this study aimed to assess the effect of UIV extension on scoliosis correction and global alignment in patients with the UIV as the UEV and UEV+1.MethodsData of 52 patients with AIS with Lenke type 5C curves who underwent selective thoracolumbar/lumbar (TL/L) fusion with a minimum follow-up period of 2 years were retrospectively analyzed. The patients were divided according to the UIV in relation to the UEV: the UEV and UEV+1 groups. Radiographic parameters and clinical outcomes were compared between the two groups.ResultsAmong the 52 patients, 24 and 28 were included in the UEV and UEV+1 group. Baseline data showed no intergroup differences except for the UIV level. While the UEV+1 group showed a significantly greater TL/L curve correction (72.9% vs. 62.8%, p<0.05) and a lower UIV tilt, it showed a significantly greater absolute value of radiographic shoulder height (RSH) (-7.9 vs. -0.9mm, p<0.05) and coronal balance (-11.0mm vs -4.8mm, p<0.05) at 2 years postoperatively. The rate of post-operative shoulder imbalance (RSH≥2cm) was significantly higher in the UEV+1 than in the UEV group. 23 No intergroup differences were observed in the sagittal alignment and patient outcomes between the two groups.ConclusionWhen the UIV was selected as the UEV+1, correction of the TL/L curve improved; however, it increased the risk of shoulder and coronal imbalance. There is no clinical benefit observed in terms of extending the UIV to the UEV+1; therefore, the UIV should be selected as the UEV to maintain harmonious global alignment.