Clinical study of selection of the upper instrumented vertebra at one level caudal to upper end vertebra in patients with Lenke 5C adolescent idiopathic scoliosis

Abstract

Objective: To investigate whether the upper instrumented vertebra (UIV) can be selected at one level caudal to upper end vertebra (UEV) in Lenke type 5C adolescent idiopathic scoliosis (AIS) patients. Methods: Total of 28 Lenke 5C AIS patients who underwent selective posterior fusion in Drum Tower Hospital of Nanjing University Medical School from September 2013 to September 2015 were included. There were 4 males and 24 females, with an age of (15.0±2.0) years, the Risser sign was graded 2-5. The following imaging parameters were measured on standing full spine X-ray before, immediately after the surgery and at the last follow-up: thoracolumbar/lumbar (TL/L) Cobb angle, coronal balance, UIV translation, lower instrumented vertebra (LIV) translation, UIV tilt, LIV tilt, and thoracic apical vertebral translation (T-AVT), lumbar apical vertebral translation (L-AVT). The patients were divided into two groups: decompensation group (n=6) and non-decompensation group (n=22). Radiographic parameters and Scoliosis Research Society (SRS)-22 scores were compared between the two groups. Results: Six cases (21.4%) had proximal decompensation at the last follow-up. There were no significant differences in Risser grade(3.8±1.0 vs 3.6±1.6), baseline thoracic Cobb angle(25.8°±2.2° vs 26.3°±6.4°) and TL/L Cobb angle(43.7°±3.4° vs 45.2°±6.5°) between the two groups (all P>0.05). However, the baseline lumbar/thoracic apical vertebra translation (L-T AVT ratio) was significantly higher in patients with proximal decompensation (6.3±1.3 vs 4.0±2.0, P=0.048). Conclusion: Selecting UIV at one level caudal to UEV, would not increase the incidence of proximal decompensation in Lenke 5C AIS patients with Risser higher than grade 2, the smaller baseline L-T AVT ratio, and with thoracic compensatory curve over 15°, and can obtain satisfactory clinical results.