A Retrospective Analysis Of Influential Factors Of Lower Instrumented Vertebra In Adolescent Idiopathic Scoliosis With Lenke 5C Curves

Objectives:To explore the influential factors of lower instrumented vertebra in adolescent idiopathic scoliosis with Lenke 5C curves.Methods:27 consecutive AIS patients(Lenke 5C)undergoing posterior selective TL/L fusion with pedicle screw fixation were reviewed.The average year was 15.4±2.3 years.The average follow-up was 43±24 months.Standing anteroposterior,convex side beeding and lateral radiographs were measured and analyzed.Results:The following data were about which selected the touched(TV)as lower instrumented vertebra.The average preoperative Cobb angle was 40.3°±8.5°and corrected to 4.1°±4.2°postoperatively with the correction rate of(90.4±9.5)%,and correction loss was 1.4°±3.5°at the final follow-up.The average preoperative Cobb angle of thoracic curve was 24.9°±6.6°,and the convex side beeding was 8.3°±5.5°with a flexibility of(66.8±19.0)%,and corrected to 8.1°±6.1°postoperatively with a spontaneous correction rate of(65.9±25.1)%.The apical vertebra translation decreased from 41.7±13.0mm peroperatively to 9.7±7.1mm,and corrected to 5.5±5.5mm at the final follow-up.The trunk shift decreased from 12.3±10.4mm preoperatively to 2.5±3.8mm postoperatively,and corrected to 2.8mm±4.4mm at the final follow-up.The tilt of lower instrumented vertebra(LIV)decreased from 20.7°±6.4°preoperatively to 2.8°±2.9°postoperatively,and corrected to 3.7°±3.4°at the final follow-up.Compared to fusion to the stable vertebrae,fusion to the touched vertebrae(TV)saved 1.28±0.46 mobile segments.The tilt of lower instrumented vertebra(LIV)which were more than 25°was 14 cases,and choosing the touched vertebrae as the lower instrumented vertebra was 8 cases which the tilt of lower instrumented vertebra(LIV)were less than 10°at the postoperative time and the final follow-up.There were no decompensation for all patients at the final follow-up.Conclusion:(1)Choosing the touched vertebrae(TV)as the lower instrumented vertebra(LIV)is safe and can achieve a good radiological result.(2)It doesn't need to extend the fusion distal when the tilt of the touched vertebrae(TV)is more than 25°and it is enough to the touched vertebrae(TV).(3)The effect of the touched vertebrae(TV)is better than the common effect of the thoracolumbar / lumbar size,the tilt of the lower instrumented vertebra(LIV),vertebral rotation and apical vertebrae translation for choosing the lower instrumented vertebra(LIV).