Objective:To clarify the characteristics of dynamic change of pelvic incidence (PI) in patients with adult spinal deformity in a longitudinal study, to explore the relationship of PI change and other sagittal parameters, and to investigate the role of PI change in the progression of global sagittal imbalance.Methods:The patients with adult spinal deformity (ASD) who were followed up at our clinic from December 2014 to December 2022 were retrospectively reviewed. All patients were older than 50 years and had a minimum of 2-year follow-up. Full-spine frontal and lateral X-ray films were taken at pre-operation, post-operation, and last follow-up. Radiographic parameters were measured, including Cobb angle, thoracic kyphosis (TK), lumbar lordosis (LL), regional kyphosis (RK), sagittal vertical axis (SVA), T1 pelvic angle (TPA), pelvic incidence (PI), pelvic tilt (PT) and sacral slope (SS). Intraclass correlation coefficient (ICC) was used to evaluate intra- and inter-observers' reliability, of which ICC>0.75 indicated excellent; 0.5< ICC≤0.75 indicated good; ICC≤0.5 indicated poor. Independent t-test, paired t-test and Pearson coefficient correlation were performed for statistical analysis. Results:A total of 30 patients were included in this study with a mean age of 61.93±6.20 years (range 54-72 years). The mean follow-up duration was 37.47±8.57 months (range 25-46 months). ICC test showed an excellent intra- and inter-observer reliability of PI in ASD patients from baseline to last follow-up (inter-observer ICC: 0.917 at baseline and 0.923 at last follow-up; intra-observer ICC: 0.913 at baseline and 0.915 at last follow-up). From first-visit to the last follow-up, PI significantly increased from 44.47°±5.96° to 52.07°±7.42° ( t=13.375, P<0001), PT (22.33°±5.77° vs. 28.07°±8.16°, t=4.268, P=0.001), SVA (40.03±13.34 mm vs. 64.37±27.06 mm, t=5.303, P<0.001), TPA (16.20°±5.02° vs. 27.13°±6.45°, t=13.742, P<0.001) and PI-LL (15.07°±13.92° vs. 29.67°±13.54°, t=10.802, P<0.001) were significantly increased while LL was significantly decreased (29.40°±15.53° vs. 22.40°±16.47°, t=4.814, P<0.001) at last follow-up. Pearson correlation analysis showed that the change of PT ( r=0.659, P=0.008), the change of TPA ( r=0.629, P=0.012), pre-operation PI ( r=0.560, P=0.030), and the last follow-up PI ( r=0.746, P=0.001) were significantly correlated with last follow-up PI. Conclusion:This study suggested that PI could significantly increase during follow-up in ASD patients. The dynamic change of PI may be correlated with the deterioration of sagittal imbalance.

Objective:To investigate the correlation between pelvic compensatory capacity and proximal junctional kyphosis (PJK) in patients with adult spinal deformity undergoing spino-pelvic fixation utilizing second sacral alar iliac (S 2AI). Methods:A cohort of 55 patients diagnosed with adult spinal deformity and treated with spino-pelvic fixation utilizing S 2AI between January 2016 and January 2019 was included. The pelvic tilt to pelvic incidence ratio (PT to PI ratio, PTr) was used to categorize patients into high PTr group (PT/PI>0.4) and low PTr group (PT/PI<0.4). Subsequently, patients were further classified into PJK group and non-PJK group based on the occurrence of PJK during the last follow-up. Radiographic parameters such as Cobb angle, coronal balance distance (CBD), global kyphosis (GK), thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), proximal junctional angle (PJA), T 1 pelvic angle (T 1PA), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), and PI-LL were measured preoperatively, postoperatively, and at final follow-up. The chi-square test was employed to compare the incidence of PJK between the high PTr and low PTr groups at the last follow-up. Additionally, multivariable logistic regression analysis was conducted to identify independent risk factors for PJK. Results:The incidence of PJK was significantly higher in the high PTr group compared to the low PTr group [high PTr group (38%) vs. low PTr group (8%), P<0.05]. Multivariable logistic regression analysis identified pre-operative PTr [ OR=3.274, 95% CI(1.100, 36.973), P=0.035], post-operative PTr [ OR=5.700, 95% CI(1.271, 65.272), P=0.029], and PJA at the last follow-up [ OR=1.274, 95% CI(0.998, 1.624), P=0.009] as independent risk factors for PJK. Conclusion:Patients with higher PTr exhibited poor pelvic compensatory ability, struggled to maintain optimal sagittal balance post-operation, and were at increased risk of developing PJK during follow-up.

Objective:To investigate the effect of Hounsfield Units (HU) at the upper instrumented vertebra (UIV) on postoperative proximal junctional kyphosis (PJK) after pelvic fixation with second sacral alar-iliac (S 2AI) screws in patients with degenerative spinal deformity. Methods:A total of 66 patients with degenerative spinal deformity who underwent pelvic fixation with S 2AI screws from August 2015 to April 2021 were retrospectively reviewed. The cohort included 4 males and 62 females, aged 61.9±7.3 years (range, 43-78 years), with a follow-up period of 18.4±14.3 months (range, 6-60 months). The prevalence of PJK was 26%. Patients were divided into two groups based on the occurrence of PJK during postoperative follow-up: the PJK group (17 cases) and the non-PJK group (49 cases). HU measurements were taken at the UIV, the vertebral body cephalad to the UIV (UIV+1), and the L 3 and L 4 vertebral bodies. The following sagittal radiographic parameters were measured: thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), PI minus LL (PI-LL), and sagittal vertical axis (SVA) at preoperative, postoperative, and final follow-up. General information and HU values of the two groups were compared, and Pearson correlation analysis was performed on HU values, bone mineral density (BMD), and T scores. Logistic regression analysis was used to explore the risk factors for PJK. Results:The HU values of L 3 and L 4 were significantly positively correlated with the BMD and T scores respectively ( r=0.530, P<0.001; r=0.537, P<0.001). Age, gender, follow-up time, fixation levels, bone mineral density (BMD) and T-score were not significantly different between PJK and non-PJK group. The average HU values of UIV and UIV+1 in PJK group was 104.3±32.9, whlie the average HU values of UIV and UIV+1 in non-PJK group was 133.7±29.5. The difference of HU between the two groups was statistically significant ( t=3.441, P=0.001). Logistic regression analysis showed that average HU values of UIV and UIV+1 [ OR=0.960, 95% CI(0.933, 0.987), P=0.004] and changes of lumbar lordosis [ OR=1.049, 95% CI(1.007, 1.092), P=0.023] were independent risk factors for PJK, with an optimal cutoff obtained by ROC that 106 for average HU values of UIV and UIV+1 and 22.5° for changes of LL. Conclusion:The average HU values of UIV and UIV+1 < 106 and changes of lumbar lordosis > 22.5° are independent risk factors for PJK after pelvic fixation with second sacralalar-iliac in patients with degenerative spinal deformity.

Objective: To establish a novel classification system for predicting the risk of intraoperative neurophysiological monitoring (IONM) events in surgically-treated patients with kyphotic deformity. Methods: Patients with kyphotic deformity who underwent surgical correction of cervicothoracic, thoracic, or thoracolumbar kyphosis in our center from July 2005 to December 2020 were recruited. We proposed a classification system to describe the morphology of the spinal cord on T2-weighted sagittal magnetic resonance imaging: type A, circular/symmetric cord with visible cerebrospinal fluid (CSF) between the cord and vertebral body; type B, circular/oval/symmetric cord with no visible CSF between the cord and vertebral body; type C, spinal cord that is fattened/deformed by the vertebral body, with no visible CSF between the cord and vertebral body. Furthermore, based on type C, the spinal cord compression ratio (CR) < 50% was defined as the subtype C-, while the spinal cord CR ≥ 50% was defined as the subtype C+. IONM event was documented, and a comparative analysis was made to evaluate the prevalence of IONM events among patients with diverse spinal cord types. Results: A total of 294 patients were reviewed, including 73 in type A; 153 in type B; 53 in subtype C- and 15 in subtype C+. Lower extremity transcranial motor-evoked potentials and/or somatosensory evoked potentials were lost intraoperatively in 41 cases (13.9%), among which 4 patients with type C showed no return of spinal cord monitoring data. The 14 subtype C+ patients (93.3%) had IONM events. Univariate logistic regression analysis showed that patients with a type C spinal cord (subtype C-: odds ratio [OR], 10.390; 95% confidence interval [CI], 2.215–48.735; p = 0.003; subtype C+, OR, 497.000; 95% CI, 42.126– 5,863.611; p < 0.001) are at significantly higher risk of a positive IONM event during deformity correction compared to those with a type A. In further multiple logistic regression analysis, the spinal cord classification (OR, 5.371; 95% CI, 2.966–9.727; p < 0.001) was confirmed as an independent risk factor for IONM events. Conclusion We presented a new spinal cord classification system based on the relative position of the spinal cord and vertebrae to predict the risk of IONM events in patients with kyphotic deformity. In patients with type C spinal cord, especially those in C+ cases, it is essential to be aware of potential IONM events, and adopt standard operating procedures to facilitate neurological recovery.

Objective: To explore the changes in coronal imbalance (CIB) in Lenke 5C adolescent idiopathic scoliosis (AIS) after posterior selective fusion surgery and determine their implications for surgical decision-making. Methods: One hundred twenty patients were categorized according to the preoperative coronal pattern (type A, coronal balance distance [CBD]<20 mm; type B, CBD≥20 mm and coronal C7 plumbline [C7PL] shifted to the concave side of the curve; type C, CBD≥20 mm and C7PL shifted to the convex side of the curve). CIB group (CIB+) was defined as having a CBD≥20 mm at the 2-year follow-up. Results: Compared to type A patients, the prevalence of postoperative CIB was higher in type C patients both immediately postoperative (22% vs. 38%, p<0.05) and at the final follow-up (5% vs. 29%, p<0.05), whereas type A patients showed a greater improvement in CBD (9 of 12 vs. 6 of 24, p<0.05) at the final follow-up. The majority of patients in all groups had recovered to type A at the final follow-up (96 of 120). The proximal Cobb-1 strategy reduced the incidence of postoperative CIB (1 of 38) at the 2-year follow-up, especially in preoperative type C patients. Multivariate logistic regression analysis revealed that type C and overcorrection of the thoracolumbar curve were risk factors for CIB at the 2-year follow-up (p=0.007 and p=0.026, respectively). Conclusion Patients with type C CIB in AIS exhibited unsatisfactory restoration, with 29% of them exhibiting CIB at the final follow-up. The selective fusion strategy of proximal Cobb-1 may reduce the risk of postoperative CIB especially when the preoperative coronal pattern is type C.

Objective: To establish a novel classification system for predicting the risk of intraoperative neurophysiological monitoring (IONM) events in surgically-treated patients with kyphotic deformity. Methods: Patients with kyphotic deformity who underwent surgical correction of cervicothoracic, thoracic, or thoracolumbar kyphosis in our center from July 2005 to December 2020 were recruited. We proposed a classification system to describe the morphology of the spinal cord on T2-weighted sagittal magnetic resonance imaging: type A, circular/symmetric cord with visible cerebrospinal fluid (CSF) between the cord and vertebral body; type B, circular/oval/symmetric cord with no visible CSF between the cord and vertebral body; type C, spinal cord that is fattened/deformed by the vertebral body, with no visible CSF between the cord and vertebral body. Furthermore, based on type C, the spinal cord compression ratio (CR) < 50% was defined as the subtype C-, while the spinal cord CR ≥ 50% was defined as the subtype C+. IONM event was documented, and a comparative analysis was made to evaluate the prevalence of IONM events among patients with diverse spinal cord types. Results: A total of 294 patients were reviewed, including 73 in type A; 153 in type B; 53 in subtype C- and 15 in subtype C+. Lower extremity transcranial motor-evoked potentials and/or somatosensory evoked potentials were lost intraoperatively in 41 cases (13.9%), among which 4 patients with type C showed no return of spinal cord monitoring data. The 14 subtype C+ patients (93.3%) had IONM events. Univariate logistic regression analysis showed that patients with a type C spinal cord (subtype C-: odds ratio [OR], 10.390; 95% confidence interval [CI], 2.215–48.735; p = 0.003; subtype C+, OR, 497.000; 95% CI, 42.126– 5,863.611; p < 0.001) are at significantly higher risk of a positive IONM event during deformity correction compared to those with a type A. In further multiple logistic regression analysis, the spinal cord classification (OR, 5.371; 95% CI, 2.966–9.727; p < 0.001) was confirmed as an independent risk factor for IONM events. Conclusion We presented a new spinal cord classification system based on the relative position of the spinal cord and vertebrae to predict the risk of IONM events in patients with kyphotic deformity. In patients with type C spinal cord, especially those in C+ cases, it is essential to be aware of potential IONM events, and adopt standard operating procedures to facilitate neurological recovery.

Objective: To explore the changes in coronal imbalance (CIB) in Lenke 5C adolescent idiopathic scoliosis (AIS) after posterior selective fusion surgery and determine their implications for surgical decision-making. Methods: One hundred twenty patients were categorized according to the preoperative coronal pattern (type A, coronal balance distance [CBD]<20 mm; type B, CBD≥20 mm and coronal C7 plumbline [C7PL] shifted to the concave side of the curve; type C, CBD≥20 mm and C7PL shifted to the convex side of the curve). CIB group (CIB+) was defined as having a CBD≥20 mm at the 2-year follow-up. Results: Compared to type A patients, the prevalence of postoperative CIB was higher in type C patients both immediately postoperative (22% vs. 38%, p<0.05) and at the final follow-up (5% vs. 29%, p<0.05), whereas type A patients showed a greater improvement in CBD (9 of 12 vs. 6 of 24, p<0.05) at the final follow-up. The majority of patients in all groups had recovered to type A at the final follow-up (96 of 120). The proximal Cobb-1 strategy reduced the incidence of postoperative CIB (1 of 38) at the 2-year follow-up, especially in preoperative type C patients. Multivariate logistic regression analysis revealed that type C and overcorrection of the thoracolumbar curve were risk factors for CIB at the 2-year follow-up (p=0.007 and p=0.026, respectively). Conclusion Patients with type C CIB in AIS exhibited unsatisfactory restoration, with 29% of them exhibiting CIB at the final follow-up. The selective fusion strategy of proximal Cobb-1 may reduce the risk of postoperative CIB especially when the preoperative coronal pattern is type C.

Objective: To establish a novel classification system for predicting the risk of intraoperative neurophysiological monitoring (IONM) events in surgically-treated patients with kyphotic deformity. Methods: Patients with kyphotic deformity who underwent surgical correction of cervicothoracic, thoracic, or thoracolumbar kyphosis in our center from July 2005 to December 2020 were recruited. We proposed a classification system to describe the morphology of the spinal cord on T2-weighted sagittal magnetic resonance imaging: type A, circular/symmetric cord with visible cerebrospinal fluid (CSF) between the cord and vertebral body; type B, circular/oval/symmetric cord with no visible CSF between the cord and vertebral body; type C, spinal cord that is fattened/deformed by the vertebral body, with no visible CSF between the cord and vertebral body. Furthermore, based on type C, the spinal cord compression ratio (CR) < 50% was defined as the subtype C-, while the spinal cord CR ≥ 50% was defined as the subtype C+. IONM event was documented, and a comparative analysis was made to evaluate the prevalence of IONM events among patients with diverse spinal cord types. Results: A total of 294 patients were reviewed, including 73 in type A; 153 in type B; 53 in subtype C- and 15 in subtype C+. Lower extremity transcranial motor-evoked potentials and/or somatosensory evoked potentials were lost intraoperatively in 41 cases (13.9%), among which 4 patients with type C showed no return of spinal cord monitoring data. The 14 subtype C+ patients (93.3%) had IONM events. Univariate logistic regression analysis showed that patients with a type C spinal cord (subtype C-: odds ratio [OR], 10.390; 95% confidence interval [CI], 2.215–48.735; p = 0.003; subtype C+, OR, 497.000; 95% CI, 42.126– 5,863.611; p < 0.001) are at significantly higher risk of a positive IONM event during deformity correction compared to those with a type A. In further multiple logistic regression analysis, the spinal cord classification (OR, 5.371; 95% CI, 2.966–9.727; p < 0.001) was confirmed as an independent risk factor for IONM events. Conclusion We presented a new spinal cord classification system based on the relative position of the spinal cord and vertebrae to predict the risk of IONM events in patients with kyphotic deformity. In patients with type C spinal cord, especially those in C+ cases, it is essential to be aware of potential IONM events, and adopt standard operating procedures to facilitate neurological recovery.

Objective: To explore the changes in coronal imbalance (CIB) in Lenke 5C adolescent idiopathic scoliosis (AIS) after posterior selective fusion surgery and determine their implications for surgical decision-making. Methods: One hundred twenty patients were categorized according to the preoperative coronal pattern (type A, coronal balance distance [CBD]<20 mm; type B, CBD≥20 mm and coronal C7 plumbline [C7PL] shifted to the concave side of the curve; type C, CBD≥20 mm and C7PL shifted to the convex side of the curve). CIB group (CIB+) was defined as having a CBD≥20 mm at the 2-year follow-up. Results: Compared to type A patients, the prevalence of postoperative CIB was higher in type C patients both immediately postoperative (22% vs. 38%, p<0.05) and at the final follow-up (5% vs. 29%, p<0.05), whereas type A patients showed a greater improvement in CBD (9 of 12 vs. 6 of 24, p<0.05) at the final follow-up. The majority of patients in all groups had recovered to type A at the final follow-up (96 of 120). The proximal Cobb-1 strategy reduced the incidence of postoperative CIB (1 of 38) at the 2-year follow-up, especially in preoperative type C patients. Multivariate logistic regression analysis revealed that type C and overcorrection of the thoracolumbar curve were risk factors for CIB at the 2-year follow-up (p=0.007 and p=0.026, respectively). Conclusion Patients with type C CIB in AIS exhibited unsatisfactory restoration, with 29% of them exhibiting CIB at the final follow-up. The selective fusion strategy of proximal Cobb-1 may reduce the risk of postoperative CIB especially when the preoperative coronal pattern is type C.

Objective: To establish a novel classification system for predicting the risk of intraoperative neurophysiological monitoring (IONM) events in surgically-treated patients with kyphotic deformity. Methods: Patients with kyphotic deformity who underwent surgical correction of cervicothoracic, thoracic, or thoracolumbar kyphosis in our center from July 2005 to December 2020 were recruited. We proposed a classification system to describe the morphology of the spinal cord on T2-weighted sagittal magnetic resonance imaging: type A, circular/symmetric cord with visible cerebrospinal fluid (CSF) between the cord and vertebral body; type B, circular/oval/symmetric cord with no visible CSF between the cord and vertebral body; type C, spinal cord that is fattened/deformed by the vertebral body, with no visible CSF between the cord and vertebral body. Furthermore, based on type C, the spinal cord compression ratio (CR) < 50% was defined as the subtype C-, while the spinal cord CR ≥ 50% was defined as the subtype C+. IONM event was documented, and a comparative analysis was made to evaluate the prevalence of IONM events among patients with diverse spinal cord types. Results: A total of 294 patients were reviewed, including 73 in type A; 153 in type B; 53 in subtype C- and 15 in subtype C+. Lower extremity transcranial motor-evoked potentials and/or somatosensory evoked potentials were lost intraoperatively in 41 cases (13.9%), among which 4 patients with type C showed no return of spinal cord monitoring data. The 14 subtype C+ patients (93.3%) had IONM events. Univariate logistic regression analysis showed that patients with a type C spinal cord (subtype C-: odds ratio [OR], 10.390; 95% confidence interval [CI], 2.215–48.735; p = 0.003; subtype C+, OR, 497.000; 95% CI, 42.126– 5,863.611; p < 0.001) are at significantly higher risk of a positive IONM event during deformity correction compared to those with a type A. In further multiple logistic regression analysis, the spinal cord classification (OR, 5.371; 95% CI, 2.966–9.727; p < 0.001) was confirmed as an independent risk factor for IONM events. Conclusion We presented a new spinal cord classification system based on the relative position of the spinal cord and vertebrae to predict the risk of IONM events in patients with kyphotic deformity. In patients with type C spinal cord, especially those in C+ cases, it is essential to be aware of potential IONM events, and adopt standard operating procedures to facilitate neurological recovery.