After approving by the institution review board (IRB) of the hospital, participants or, where participants are children, a parent or guardian, who signed the Informed Consent Form were taken into this retrospective study. From Jan 2008 to Jul 2012, consecutive population of 36 adolescents and 36 younger adults with single or double thoracic scoliosis were retrospective reviewed and matched by magnitude and pattern of the curve. Major curve ranged from 45–75 degrees. All patients met the criteria of STF (T/L cobb angle ratio > 1.2) stated by Lenke. All patients were treated with posterior-only pedicle screw technique by the same group of surgeons.
In the YAdIS Group, the average age was 29.1 ± 2.5 years. 5 cases were male and 31 cases were female, with an average follow-up of 32.7 ± 5.3 months (24–36 months) .According to the SRS classification system, 25 cases were single thoracic scoliosis and 11 cases were double thoracic scoliosis. The indication of surgery for these patients were curve progression and cosmetic problem. Meanwhile, some of them suffered from back pain. Most of these patients chose to delay surgery because they were worried about the effect on children’s spinal growth, patients’ studies, daily activities and psychological states.. Unfortunately, these untreated spinal deformities still progressed as patients aging.
Patients included in Group AIS were from 10 to 18 years old with average age of 13.8 ± 2.8 years. Based on Lenke classification system, 28 patients were typed Lenke 1(21 of 1A,5 of 1B,2 of 1C) and 8 patients were typed Lenke 2(5 of 2A, 2 of 2B, 1 of 2C).
For the AIS Group, all patients were placed in a prone position after general anesthesia. After a posterior midline incision was made, subperiosteal paraspinal muscle was dissected to expose the posterior bone structure. Pedicle screws were inserted into the fusion segments bilaterally with free hand technique. Fusion strategy was performed in accordance with the principle of Lenke classification. All the structural major and minor curves were fused while non-structural compensatory curves were not included. For 10 patients with fixed deformity, multiple Ponte osteotomies  were used to attain correction via a posterior approach. Curve correction was achieved using the direct vertebral derotation maneuver, followed by slight convex compression and concave distraction. Decortication of the posterior elements was performed after the correction, and poster-lateral fusion was done with allograft, autograft, followed by wound closure gradually and drainage retained.
For the YAdIS group, the same procedure was done. As patients in our research didn’t have radicular symptoms of lower extremity, nerve root and spinal canal decompression were not performed. Multi-segmental Ponte osteotomies  were done in 20 patients because of stiffer curve in younger adults.
Somatosensory-evoked potentials and MEP were routinely assessed for intraoperative monitoring of spinal cord function. Self-transfusion was used. All patients in the study were operated by the same group of surgeons. The average OR time, fusion levels, intraoperative blood loss, blood transfusion, hospital days were recorded.
Radiographic And Clinical Evaluation
All patients had pre- and post-operative standing AP and lateral radiographs. Coronal curves, T5–T12 and L1-sacrum sagittal Cobb were measured. We defined the proximal junctional angle as the caudal endplate of the upper instrumented vertebrae (UIV) to the cephalad endplate of the vertebrae two super-adjacent levels above the UIV. Coronal balance (i.e., coronal vertical alignment, CVA) was measured as the distance between C7 plumb line and the mid-sacral line (imbalance: >2 cm). Overall radiographic sagittal balance (i.e., sagittal vertical alignment, SVA) was measured as the distance between C7 plumb line and the posterior–superior aspect of S1. A positive value indicated that the C7 plumb line fell in front of the posterior superior aspect of S1, whereas a negative value indicated that this line fell in back of this point. Preoperative fulcrum lateral bending X-ray films were used to evaluate the flexibility of the curve.
Outcome analysis was performed using the Scoliosis Research Society-22. SRS questionnaires were available for 100% of patients. Radiographic measurements were performed by independent surgeons for twice. Whole spine MRI scan were used to check any inter spinal cord abnormity and to evaluate degeneration of thoracic or lumbar intervertebral disc, stenosis of central spinal canal, lateral recess or foramen.
All data were analyzed by SPSS version 21.0 statistical analysis software (SPSS Inc., Chicago, USA). Continuous variables were presented as mean standard deviation, and ordinal variables as median (interquartile range). Paired t-test was used to compare all the variables between the two groups. Fisher’s exact test was used to test for significance of categorical variables. All statistical assessments were 2-sided and evaluated at the 0.05 level of significance.