The effect of instrumentation patterns on the sagittal reconstruction following selective posterior correction for thoracic adolescent idiopathic scoliosis

Objective To explore the effect of various instrumentation patterns on the sagittal re-construction with selective posterior fusion for thoracic adolescent idiopathic scoliosis (A1S). Methods Fifty-one AIS patients of Lenke 1A, IB, 1C and 2B who underwent selective posterior thoracic fusion in at least 24 months follow-up were evaluated. The patients were divided into three groups: Group A (all-hook system), Group B (hybrid system with upper thoracic hooks and lower pedicle screws), and Group C (all-screw sys-tem). The radiological parameters before and after surgery included thoracic and lumbar curve Cobb angle, thoracic kyphosis(TK), lumbar lordosis (LL), thoracolumbar junction kyphosis (T10-I2, TJK), distal junctional kyphosis (DJK), and sagittal vertical axis (SVA). Results Over 60% coronal correction of the primary curve and a satisfactory spontaneous correction of the secondary curve were achieved in three groups. There was no change of LL in three groups and SVA maintained in normal range before surgery and during follow-up peri-ods in all groups. However, in Group A, at the last phase of this research, DJK had a mean value of 3.6° of kyphosis compared with preoperative angle of -2.3° (P=0.037), which showed a lordosis loss of 5.9° in Group A. TK averaged 23.0° at the last phase compared with preoperative angle of 13.5° (P=0.072). TJK averaged 6.4° at the last phase compared with preoperative angle of -2.8° (P=0.070), and there was a lordosis loss of 9.2°. There were no obvious changes of TK, TJK and DJK in Group B and Group C during the whole follow-up. Conclusion Satisfactory correction on coronal plane, sagittal balance and lumbar lordosis could be maintained with selective thoracic all-hook instrumentation for thoracic AIS patients during follow-up. How-ever, the patients with all-hook system may develop thoracic kyphosis and sagittal junctional decompensation because of the instability of instrumentation. Key words: Scoliosis;  Adolescent;  Spinal fusion;  Internal fixators