Objective:To investigate the effect of anterior and posterior selective fusion strategy on evolution of coronal pattern in patients with Lenke 5C adolescent idiopathic scoliosis (AIS) and whether upper end vertebra (UEV)-1 strategy in anterior surgery would have an effect on postoperative coronal balance.Methods:A total of 108 Lenke 5C AIS patients with at least 2 years follow-up who underwent anterior or posterior selective thoracolumbar fusion surgery from January 2005 to December 2020 were enrolled, with 51 patients in the anterior group and 57 patients in the posterior group. The patients were categorized into three groups (type A, C 7PL-CSVL<20 mm; type B, C 7PL-CSVL ≥20 mm with C 7PL toward the concave side of the main curve; and type C, C 7PL-CSVL≥20 mm with C 7PL toward the convex side of the main curve) to investigate the evolution of coronal balance of each preoperative coronal pattern at the anterior and posterior groups. Parameters such as thoracolumbar Cobb angle, rate of coronal imbalance, and SRS-22 score were recorded at preoperative, 1 week postoperatively, and final follow-up in both groups. Results:The differences of basic date between the two groups were not statistically significant except for the fusion level (5.2±0.7 vs. 5.6±0.9, t=2.497, P=0.014). In the anterior group, a total of 27 patients with preoperative type A, 23 patients with preoperative type A maintained type A at the 1 week postoperatively, and 2 of them were converted to type C at the final follow-up. Four patients with preoperative type A converted to type C at the 1 week postoperatively, and all of them returned to type A at the final follow-up. A total of 23 patients with preoperative type C, four patients with preoperative type C maintained type C at the 1 week postoperatively, and one of them maintained type C at the final follow-up. Nineteen patients with preoperative type C converted to type A at the 1 week postoperatively, and all of them maintained type A at the final follow-up. In the posterior group, a total of 26 patients with preoperative type A, 22 patients with preoperative type A maintained type A at the 1 week postoperatively, and only 2 of these patients converted to type C at the final follow-up. Four of the preoperative type A patients converted to type C at the 1 week postoperatively, and all of them returned to type A at the final follow-up. A total of 29 patients with preoperative type C, thirteen patients with preoperative type C maintained type C at the 1 week postoperatively, and 7 of them maintained type C at the last follow-up. Sixteen patients with preoperative type C converted to type A at the 1 week postoperatively, of whom two converted to type C at the final follow-up. For patients with preoperative type C the rate of coronal imbalance was significantly lower in the anterior group than in the posterior group both in the immediate postoperative period (17% vs. 45%, P<0.05) and at the final follow-up (4% vs. 31%, P=0.038). The rate of coronal imbalance at final follow-up was significantly lower in the UEV-1 group than in the UEV group in the posterior approach (3% vs. 38%, P<0.05), and there was no difference between the two groups in the anterior approach. There were no significant differences in radiographic parameters and SRS-22 scores between the two groups, except for the thoracic Cobb angle at the final follow-up, which was greater in the anterior group than in the posterior group at the final follow-up (19.5±7.3 vs.16.4±5.6, t=2.427, P=0.017). Multivariate logistic regression analysis revealed that anterior surgery and Risser were risk factors for postoperative CIB of preoperative type C ( OR=21.138, P=0.030 and OR=0.406, P=0.048 respectively). Conclusion:For patients with preoperative type A, both anterior and posterior procedures lead to a satisfactory reconstruction of coronal balance. In patients with preoperative type C, anterior surgery acquire a better reconstruction of coronal balance. The strategy of proximal UEV-1 was similar to the strategy of UEV in terms of restoring coronary balance in anterior approach and it was unable to lower the rate of postoperative coronal imbalance. In contrast, UEV-1 strategy in posterior surgery was effective in reducing the rate of postoperative coronal imbalance.

Objective:To evaluate the relationship between postoperative changes in femoral head coverage (FHC) after S 2-Alar-Iliac (S 2AI) screw fixation and the development of sagittal imbalance during follow-up in patients with adult spinal deformity (ASD), providing insights for clinical assessment and treatment strategies. Methods:A consecutive cohort of 98 ASD patients who underwent S2AI fixation between September 2019 and September 2021 was retrospectively analyzed. Patients were divided into two groups based on changes in femoral head coverage (ΔFHC): the FHC-C group (upper quartile ΔFHC, 25 cases) and the FHC-NC group (lower quartile ΔFHC, 24 cases). Additionally, patients were classified into proximal junctional kyphosis (PJK) and non-PJK groups based on their clinical outcomes at the last follow-up. Standing full-spine anteroposterior and lateral X-rays were taken preoperatively, postoperatively, and at the two-year follow-up to measure and document the following spinal parameters: Cobb angle, proximal lumbar lordosis (PLL), distal lumbar lordosis (DLL), lumbar lordosis (LL), lordosis distribution index (LDI), sagittal vertical axis (SVA), coronal balance distance (CBD), thoracic kyphosis (TK), T 1 pelvic angle (T 1PA), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), PI-LL, and proximal junctional angle (PJA). Parameters related to hip joint coverage included: femoral head coverage (FHC), lateral center-edge angle (LCE angle), acetabular index (AI), Sharp angle, and extrusion index (EI). Comparisons of radiographic indicators between the two groups were performed at preoperative, postoperative, and final follow-up assessments. The visual analogue scale (VAS) was used to evaluate the hip pain and back pain. Results:At final follow-up, the incidence of PJK was significantly higher in the FHC-NC group [37.5% (9/24)] compared to the FHC-C group [16.0% (4/25)] (χ 2=3.952, P=0.042). Moreover, the increase in sagittal vertical axis (ΔSVA) was significantly greater in the FHC-NC group (35.9±44.7 mm vs. 14.6±31.8 mm, t=2.216, P=0.031). Patients with PJK had significantly higher preoperative T 1PA (36.8°±10.8° vs. 31.9°±18.4°, t=2.150, P=0.034) and lower immediate postoperative ΔFHC (1.7%±1.5% vs. 3.3%±2.5%, t=2.987, P=0.004), as well as lower changes in lateral center-edge angle during follow-up (0.3°±3.0° vs. 1.1°±8.9°, t=2.334, P=0.022). Pearson correlation analysis revealed significant negative correlations between postoperative ΔFHC and both ΔSVA ( r=-0.374, P=0.008) and proximal junctional angle changes (ΔPJA, r=-0.429, P=0.006). Additionally, increases in VAS leg pain scores correlated negatively with immediate postoperative FHC ( r=-0.314, P=0.025) and ΔFHC ( r=-0.298, P=0.031). Logistic regression indicated that immediate postoperative ΔFHC was a protective factor against PJK [ OR=0.722, 95% CI (0.541, 0.963), P=0.009), with a ROC-determined optimal ΔFHC cut-off of 3.90% (AUC=0.723, Youden index=0.847). Conclusions:Postoperative evaluation of femoral head coverage is clinically important for ASD patients undergoing S2AI screw fixation. A pre-to-post ΔFHC below 3.90% may indicate reduced hip compensation capacity, increasing risks for hip pain, sagittal imbalance progression, and PJK postoperatively.

Objective:To investigate the effect of anterior and posterior selective fusion strategy on evolution of coronal pattern in patients with Lenke 5C adolescent idiopathic scoliosis (AIS) and whether upper end vertebra (UEV)-1 strategy in anterior surgery would have an effect on postoperative coronal balance.Methods:A total of 108 Lenke 5C AIS patients with at least 2 years follow-up who underwent anterior or posterior selective thoracolumbar fusion surgery from January 2005 to December 2020 were enrolled, with 51 patients in the anterior group and 57 patients in the posterior group. The patients were categorized into three groups (type A, C 7PL-CSVL<20 mm; type B, C 7PL-CSVL ≥20 mm with C 7PL toward the concave side of the main curve; and type C, C 7PL-CSVL≥20 mm with C 7PL toward the convex side of the main curve) to investigate the evolution of coronal balance of each preoperative coronal pattern at the anterior and posterior groups. Parameters such as thoracolumbar Cobb angle, rate of coronal imbalance, and SRS-22 score were recorded at preoperative, 1 week postoperatively, and final follow-up in both groups. Results:The differences of basic date between the two groups were not statistically significant except for the fusion level (5.2±0.7 vs. 5.6±0.9, t=2.497, P=0.014). In the anterior group, a total of 27 patients with preoperative type A, 23 patients with preoperative type A maintained type A at the 1 week postoperatively, and 2 of them were converted to type C at the final follow-up. Four patients with preoperative type A converted to type C at the 1 week postoperatively, and all of them returned to type A at the final follow-up. A total of 23 patients with preoperative type C, four patients with preoperative type C maintained type C at the 1 week postoperatively, and one of them maintained type C at the final follow-up. Nineteen patients with preoperative type C converted to type A at the 1 week postoperatively, and all of them maintained type A at the final follow-up. In the posterior group, a total of 26 patients with preoperative type A, 22 patients with preoperative type A maintained type A at the 1 week postoperatively, and only 2 of these patients converted to type C at the final follow-up. Four of the preoperative type A patients converted to type C at the 1 week postoperatively, and all of them returned to type A at the final follow-up. A total of 29 patients with preoperative type C, thirteen patients with preoperative type C maintained type C at the 1 week postoperatively, and 7 of them maintained type C at the last follow-up. Sixteen patients with preoperative type C converted to type A at the 1 week postoperatively, of whom two converted to type C at the final follow-up. For patients with preoperative type C the rate of coronal imbalance was significantly lower in the anterior group than in the posterior group both in the immediate postoperative period (17% vs. 45%, P<0.05) and at the final follow-up (4% vs. 31%, P=0.038). The rate of coronal imbalance at final follow-up was significantly lower in the UEV-1 group than in the UEV group in the posterior approach (3% vs. 38%, P<0.05), and there was no difference between the two groups in the anterior approach. There were no significant differences in radiographic parameters and SRS-22 scores between the two groups, except for the thoracic Cobb angle at the final follow-up, which was greater in the anterior group than in the posterior group at the final follow-up (19.5±7.3 vs.16.4±5.6, t=2.427, P=0.017). Multivariate logistic regression analysis revealed that anterior surgery and Risser were risk factors for postoperative CIB of preoperative type C ( OR=21.138, P=0.030 and OR=0.406, P=0.048 respectively). Conclusion:For patients with preoperative type A, both anterior and posterior procedures lead to a satisfactory reconstruction of coronal balance. In patients with preoperative type C, anterior surgery acquire a better reconstruction of coronal balance. The strategy of proximal UEV-1 was similar to the strategy of UEV in terms of restoring coronary balance in anterior approach and it was unable to lower the rate of postoperative coronal imbalance. In contrast, UEV-1 strategy in posterior surgery was effective in reducing the rate of postoperative coronal imbalance.

Objective:To evaluate the relationship between postoperative changes in femoral head coverage (FHC) after S 2-Alar-Iliac (S 2AI) screw fixation and the development of sagittal imbalance during follow-up in patients with adult spinal deformity (ASD), providing insights for clinical assessment and treatment strategies. Methods:A consecutive cohort of 98 ASD patients who underwent S2AI fixation between September 2019 and September 2021 was retrospectively analyzed. Patients were divided into two groups based on changes in femoral head coverage (ΔFHC): the FHC-C group (upper quartile ΔFHC, 25 cases) and the FHC-NC group (lower quartile ΔFHC, 24 cases). Additionally, patients were classified into proximal junctional kyphosis (PJK) and non-PJK groups based on their clinical outcomes at the last follow-up. Standing full-spine anteroposterior and lateral X-rays were taken preoperatively, postoperatively, and at the two-year follow-up to measure and document the following spinal parameters: Cobb angle, proximal lumbar lordosis (PLL), distal lumbar lordosis (DLL), lumbar lordosis (LL), lordosis distribution index (LDI), sagittal vertical axis (SVA), coronal balance distance (CBD), thoracic kyphosis (TK), T 1 pelvic angle (T 1PA), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), PI-LL, and proximal junctional angle (PJA). Parameters related to hip joint coverage included: femoral head coverage (FHC), lateral center-edge angle (LCE angle), acetabular index (AI), Sharp angle, and extrusion index (EI). Comparisons of radiographic indicators between the two groups were performed at preoperative, postoperative, and final follow-up assessments. The visual analogue scale (VAS) was used to evaluate the hip pain and back pain. Results:At final follow-up, the incidence of PJK was significantly higher in the FHC-NC group [37.5% (9/24)] compared to the FHC-C group [16.0% (4/25)] (χ 2=3.952, P=0.042). Moreover, the increase in sagittal vertical axis (ΔSVA) was significantly greater in the FHC-NC group (35.9±44.7 mm vs. 14.6±31.8 mm, t=2.216, P=0.031). Patients with PJK had significantly higher preoperative T 1PA (36.8°±10.8° vs. 31.9°±18.4°, t=2.150, P=0.034) and lower immediate postoperative ΔFHC (1.7%±1.5% vs. 3.3%±2.5%, t=2.987, P=0.004), as well as lower changes in lateral center-edge angle during follow-up (0.3°±3.0° vs. 1.1°±8.9°, t=2.334, P=0.022). Pearson correlation analysis revealed significant negative correlations between postoperative ΔFHC and both ΔSVA ( r=-0.374, P=0.008) and proximal junctional angle changes (ΔPJA, r=-0.429, P=0.006). Additionally, increases in VAS leg pain scores correlated negatively with immediate postoperative FHC ( r=-0.314, P=0.025) and ΔFHC ( r=-0.298, P=0.031). Logistic regression indicated that immediate postoperative ΔFHC was a protective factor against PJK [ OR=0.722, 95% CI (0.541, 0.963), P=0.009), with a ROC-determined optimal ΔFHC cut-off of 3.90% (AUC=0.723, Youden index=0.847). Conclusions:Postoperative evaluation of femoral head coverage is clinically important for ASD patients undergoing S2AI screw fixation. A pre-to-post ΔFHC below 3.90% may indicate reduced hip compensation capacity, increasing risks for hip pain, sagittal imbalance progression, and PJK postoperatively.

Objective:To evaluate the prevalence and distribution of ossification of ligamentum flavum (OLF) at the segments adjacent to the apex in patients with degenerative kyphosis.Methods:All of 74 patients with degenerative kyphosis from January 2018 to December 2021 were retrospective reviewed. All patients were taken anteroposterior and lateral radiographs, CT scan and magnetic resonance imaging (MRI) of the entire spine. Global kyphosis, the morphology of kyphosis and the occurrence of OLF at three segments adjacent to the kyphosis apex were recorded.Results:Of the 74 patients, 54 patients (73%) developed OLF in three segments adjacent to the kyphotic apex. The mean age of the 54 patients was 61.4±6.8 years, and the mean global kyphosis was 49.5°±21.2°. Among other 20 patients without OLF, the mean age was 56.1±7.5 years, and the mean kyphosis angle was 52.1°±19.1°. There was a statistically significant difference in ages ( t=2.92, P=0.005), but no statistically significant difference was observed regarding global kyphosis ( t=0.48, P=0.634). In these 74 patients, 9 patients had angular kyphosis, of which 8 (89%) developed OLF; of the 65 patients without angular kyphosis, 46 patients (71%) developed OLF. There was no significant difference between them (χ 2=1.32, P=0.251). Among the 54 patients diagnosed with OLF, 5 patients (9%) suffered ossification of the posterior longitudinal ligament (OPLL) and 20 patients (37%) suffered dural ossification; 43 patients (80%) developed OLF at proximal segments of apex, 6 patient (11%) developed OLF at distal segments of apex, and 5 patients (9%) developed OLF both at proximal and distal segments of apex. Thirty-two patients (59%) developed OLF at the first segment adjacent to the kyphotic apex, 27 patients (50%) developed OLF at the second segment, and 15 patients (28%) developed OLF at the third segment. Conclusion:Among patients with degenerative kyphosis, about 73% may development OLF within three segments adjacent to the kyphotic apex, and it mostly occurred within two segments adjacent to the apex proximally.

Objective:To investigate the clinical outcome and complications associated with utilizing sagittal plane stable vertebra-1 (SSV-1) as the distal instrumented vertebra (LIV) in posterior fusion of thoracic kyphosis with Scheuermann's Disease kyphosis (STK).Methods:A longitudinal study on patients with STK who underwent posterior correction and fusion surgery from January 2018 to June 2021 were conducted. All participants had a follow-up duration over two years. Patients were divided into two groups according to the segment of LIV: the SSV group, where LIV was located in SSV; and the SSV-1 group, where LIV was located in the vertebral body above SSV. The radiographic parameters, including global kyphosis (GK), lumbar lordosis (LL), and sagittal plane (SVA), LIV offset distance (LIV translation), pelvic incidence (PI), pelvic tilt (PT) and sacral slope (SS), were compared between the two groups. The SRS-22 scale was used to evaluate health-related quality of life at pre-operation and last follow-up, and the incidence of postoperative distal junctional kyphosis (DJK) was also recorded. Analytical techniques, such as Analysis of Variance and Mann-Whitney tests, were employed to compare inter-group differences.Results:A total of 57 patients were included in the study, 36 in the SSV group and 21 in the SSV-1 group. The average age for patients were 16.1±2.3 years (range 13-20 years), and the average follow-up time was 32.8±6.8 months (range 24-53 months). There were no statistically significant differences between the two groups in terms of gender, age, follow-up time, surgical time, intraoperative bleeding volume, and fusion level. Before surgery, the LIV deviation distance in the SSV group was significantly lower than that in the SSV-1 group (-7.9±11.0 mm vs. 31.5±11.5 mm, t=7.64, P<0.001). In the SSV group, the preoperative GK was 79.3°±10.5°, and the last follow-up GK was 44.4°±8.5°, which was significantly improved compared to preoperative value ( t=28.28, P<0.001); in the SSV-1 group, the preoperative GK was 81.1°±10.6°, and the value at 1-week post-operative was 44.9°±7.8°, which was significantly improved compared to pre-operative value ( t=22.23, P<0.001). At the last follow-up, it was 45.1°±8.7°, with a correction rate of 44.3%±8.5%. No significant difference was observed between the two groups in terms of GK, LL, SVA, PI, PT and SS at pre-operative, 1-week post-operative and last follow-up ( P>0.05). All patients had no intraoperative complications of nerve injury. During the follow-up period, one patient (1/21, 4.8%) developed DJK without complications such as proximal kyphosis, pseudarthrosis, or failed internal fixation. At the last follow-up, the functional score of SRS-22 in SSV-1 group improved from preoperative (3.5±0.54) to postoperative (4.1±0.62), with an average improvement rate of 19.2%±3.2%, and the difference was statistically significant ( t=3.74, P=0.001). These results indicating that the surgical treatment was effective in relieving the symptoms of the patients. Conclusion:Selecting SSV-1 as LIV in corrective surgeries for STK appears to produce commendable clinical results with minimal implant-associated complications over a two-year observation period.

Objective:To propose a novel classification system based on the morphology and relative position of spinal cord in the spinal canal at sagittal T2-MRI, and to investigate the incidence and risk factors of the intraoperative neuromonitoring event (IONME) across these classifications.Methods:From January 2016 to December 2021, a consecutive cohort of 85 patients who underwent surgical correction of congenital kyphosis with pedicle screw/rod constructs were retrospectively reviewed, including 43 males and 42 females, aged 14.6±6.1 years old. According to the morphology and relative location of spinal cord at the apex of the curve on the sagittal-T2 MRI, patients were divided into three groups. Type A (5 cases) is characterized by the spinal cord centrally positioned within the spinal canal, surrounded by discernible cerebrospinal fluid (CSF). Type B (33 cases) depicts the spinal cord abutting the spinal canal's anterior wall, maintaining its intrinsic morphology. In Type C (47 patients), the spinal cord is contorted by the apical vertebral body, devoid of interposing CSF. The global kyphosis (GK) and sagittal deformity ratio (SDAR) of patients were measured before surgery. The incidence of IONME were recorded. All patients included in the study were further divided into the IONME group and the non-IONME group. Potential risk factors were identified using univariate testing. Binary Logistic Regression was used to analyze the independent risk factors for IONM.Results:All of 85 patients were reviewed: 5 (5.9%) Type A; 33 (38.8%) Type B; and 47 (55.3%) Type C spinal cords. Intraoperatively, 27 (31.8%) instances presented with lost trans-cranial motor-evoked potentials (MEPs) and/or somatosensory evoked potentials (SSEPs). Of these, 2 (7.4%) were Type B, and 25 (92.6%) were Type C, reflecting a statistically significant variance in IONME occurrences across types (χ 2=27.15, P<0.001). Notable differences were observed between IONME and non-IONME groups concerning GK, SDAR, and apex location ( t=5.41, P<0.001; t=3.65, P<0.001; χ 2=7.71, P=0.005). Univariate analysis showed that potential risk factors of IONME included Type C spinal cord ( OR=20.46, P<0.001), higher GK ( OR=1.07, P<0.001), SDAR ( OR=1.15, P=0.002) and apical vertebrae located at middle thoracic( OR=4.30, P=0.008). Independent predictors identified on binary Logistics regression modeling included higher GK ( OR=1.05, P=0.015), Type C spinal cord ( OR=6.22, P=0.042) and apex located at middle thoracic ( OR=6.43, P=0.021). Specifically, within Type C, 79% of cases where the apical vertebra was mid-thoracic experienced IONME, contrasting the 42% incidence observed in those with a lower thoracic apex positioning, signifying a notably elevated IONME likelihood for the mid-thoracic region (χ 2=5.16, P=0.023). Conclusion:Risk factors of IONME included Type C spinal cord, higher GK and apex located at middle thoracic during correction of congenital kyphosis. Preoperative MRI spinal cord typing showed great predictive value for IONME.

Objective:To investigate the feasibility and effects of modified sequential correction technique combined 3-columns osteotomy for severe kyphoscoliosis.Methods:A retrospective analysis was performed on 18 patients (7 males and 11 females) with severe kyphosis who received modified sequential correction technique combined 3-columns osteotomy in our hospital from June 2019 to April 2020. Preoperative, postoperative and final follow-up clinical and imaging outcomes were evaluated.Results:In this cohort, the average fixed segment was 11.2±3.8. The average operative duration was 401.9±68.9 min and the average intraoperative blood loss was 2 418.8±736.9 ml. The Cobb angle was improved significantly from 65.0°±16.4° pre-operatively to 41.6°±14.1° post-operatively. At final follow-up, it was 41.4°±14.3°, which was not significantly different from that after operation. Global kyphosis (GK) was 65.5°±20.8° pre-operatively and 28.1°±13.8° post-operatively with correction rate of 57.8%±17.8%. However, GK was 29.3°±14 .2° at postoperative 1 year , which was not significantly different from that after operation. There was no significant difference in C 7PL-CSVL ( F=0.449 , P=0.642) or SVA ( F=3.519, P=0.058) among the three time points. There was no alter of SEP and MEP observed during operation. Four patients had temporary lower limb numbness after operation, while the symptoms disappeared at 6 months after operation. There was no instrumental failure during the follow-up. Conclusion:Patients with severe kyphoscoliosis can obtain satisfied local correction by undergoing modified sequential correction technique combined 3-columns osteotomy without significant loss of correction at 1 year after operation. It can effectively avoid instability and dislocation of the osteotomy site and massive bleeding during the operation. As a simplified surgical procedure, it can reduce the difficulty of rod loading without prolonged operation duration. Further, this technique can ensure lower incidence of neurological complications and rod failure.

Objective:To investigate the clinical outcomes and complication of posterior surgery for Scheuermann kyphosis fusing to different distal fusion levels.Methods:From January 2012 to December 2017, a consecutive cohort of 34 patients who were treated with posterior spinal instrumented correction and satisfied the inclusion criteria were retrospectively reviewed, including 29 males and 5 females, aged 17.1±4.3 years (range, 12-30 years). All of the patients had a minimum follow-up of 2 years. According to the distal fusion level, patients were divided into 2 groups. Group sagittal stable vertebra (SSV) (22 cases) included patients whose lowest instrumented vertebra (LIV) was SSV; Group SSV-1 (12 cases) included patients who had a LIV one level above the SSV. Radiographic parameters including global kyphosis (GK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS) were measured in the standing radiographs before and after operation and at the latest follow up. Intraoperative and postoperative complications were recorded. The Scoliosis Research Society-22 questionnaire (SRS-22) were conducted at pre-operation and the final follow up to evaluate the clinical outcomes. The sagittal radiographic parameters and the incidence of distal junctional kyphosis (DJK) were compared between the two groups.Results:There were no significant differences in terms of age, sex, radiographic measurements and scores of SRS-22 between two groups preoperatively ( P>0.05). The correction rates of GK in the SSV group and the SSV-1 group were 42.8%±7.6% and 43.2%±8.4% ( t=0.151, P=0.881) respectively. While the correction rates loss were 1.2%±5.2% and 3.9%±7.2% ( t=0.767, P=0.449) at the latest follow up. No significant difference was observed in terms of other radiographic parameters ( P>0.05). During the postoperative follow up period, 3 patients (16.7%) in SSV group and 2 patients (13.6%) in SSV-1 group developed DJK. The incidence of DJK did not show any significant difference between two groups ( χ2=0.057, P=0.812). At the final follow-up, the function scores of SRS-22 in SSV-1 group (4.1±0.6) was significantly higher than SSV group (3.7±0.5) ( t=2.300, P=0.028) and there was no significant difference in the rest of the domain ( P>0.05). Conclusion:Compared with stopping at SSV, fusion to SSV-1 could achieve comparable curve correction with the preservation of more lumbar motility. Moreover, it would not increase the risk of DJK. As a result, we recommend selecting SSV-1 as the ideal LIV for SK patients.

Objective:To establish age- and gender-based normative values of sagittal spinal-pelvic alignment in Chinese adult population, and to investigate influence of age, gender and ethnicity on sagittal spinal-pelvic alignment in Chinese normal adults.Methods:A total of 786 asymptomatic Chinese adult volunteers aged between 20 and 89 years were prospectively recruited from different spine centers. The inclusion criteria were: 1) age between 20 to 89 years old; and 2) Oswestry disability index (ODI) scored lower than 20. The exclusion criteria were: 1) previous history of spinal, pelvic or lower limb pathologies that could affect the spine; 2) presence of recent and/or regular back pain; 3) previous surgeries on spine, pelvic and/or lower limb; and 4) pregnancy. Demographic characteristics of these subjects including age, gender, body weight and height were recorded. During the enrollment of volunteers, 16 groups were defined based on the age (20 s, 30 s, 40 s, 50 s, 60 s, 70 s and 80 s) and gender. Whole body biplanar standing EOS X-ray radiographs were acquired to evaluate the sagittal alignment. Spinal-pelvic parameters including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), thoracic kyphosis (T 5-T 12, TK), lumbar lordosis (L 1-S 1, LL), lower lumbar lordosis (L 4-S 1, LLL), global tilt (GT), T1 pelvic angle (TPA) and sagittal vertical axis (SVA) were measured. Values of PI-LL and lordosis distribution index (LLL/LL, LDI) were calculated. Radiographic measurements of 100 subjects were randomly selected to determine the intra- and inter-observer reliabilities using inter- and intra-class correlation coefficients (ICC). The spinal-pelvic parameters were compared among volunteers between different age and gender groups. The comparison was also made among various ethnic population. Results:The mean value was 23.7±7.1 kg/m 2 for BMI and 6.9%±2.5% (range, 0-18%) for ODI score. Each sagittal spinal-pelvic parameter was presented with mean value and standard deviationbased on age and gender. The ICCs of radiographic measurements ranged from 0.89 to 0.95, suggesting good to excellent intra- and inter-observer reliabilities. Significant differences were observed between males and females in multiple sagittal parameters (all P values <0.05). Compared to the male subjects, significantly higher values of PI (41.4° for male vs. 45.0° for female, P<0.001), PT (10.7° for male vs. 13.9° for female, P<0.001), PI-LL (-0.5° for male vs. 1.8° for female, P<0.001), and GT (10.9° for male vs. 13.5° for female, P<0.001) were documented in female subjects. Males had significantly higher values of LLL (28.6° for male vs. 26.6° for female, P<0.001) and LDI (0.68 for male vs. 0.63 for female, P<0.001). PI-LL, SVA, GT and TPA increased with aging from Group 40 s to Group 80 s, while LL, LLL and LDI decreased gradually, and TK decreased slowly with aging. Comparison of sagittal spinal-pelvic parameters between different ethnic subjects showed that Chinese adult population presented lower PI, SS, TK and LL as compared with American population; lower PI, SS and LL as compared with Japanese population. But the variation trend with aging tended to be consistent among different ethnic populations. Conclusion:Age- and gender-based normative values of sagittal spinal-pelvic alignment were established in asymptomatic Chinese adult population. Sagittal spinal-pelvic alignment varies with age and gender, and presented different compensation mechanism among different ethnic populations. Therefore, to achieve balanced sagittal alignment, age, gender and ethnicity should be take intoconsideration when planning spine correction surgery.