The Role of Spinal Cord Compression in Predicting Intraoperative Neurophysiological Monitoring Events in Patients With Kyphotic Deformity: A Magnetic Resonance Imaging-Based Study.

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.

Sagittal Imbalance in Degenerative Kyphosis: Prevalence and Implication on Postoperative Mechanical Failure.

BACKGROUND AND OBJECTIVES: To explore the patterns of sagittal imbalance in patients with lumbar or thoracolumbar degenerative kyphosis (DK) and determine its implication for the risk of mechanical complication (MC) after corrective surgery. METHODS: A total of 137 patients with DK who underwent corrective surgery were reviewed. The patients were divided into L group (with a kyphotic apex at L2 and below) and TL group (with kyphotic apex at L1 and above). Then, sacral slope (SS) (defined as S1 if SS > 0 in TL, or SS > 10 in L group) and sagittal vertical axis ≥ 5 cm (defined as +) were used as modifier sagittal balance. The Scoliosis Research Society (SRS)-22 questionnaire scores were analyzed, and the risk of mechanical failure was compared across groups. RESULTS: The distribution of subgroups was 38 (27.7%) in TLS1(-) group, 36 (26.3%) in TLS1(+) group, 16 (11.7%) in TLS0(-) group, and 5 (3.6%) in TLS0(+) group. For L group, the figure was 5 (3.6%) in LS1(-), 22 (16.1%) in LS1(+), 7 (5.2%) in LS0(-), and 8 (5.8%) in LS0(+). Patients in L group had significantly higher regional kyphosis, lower lumbar lordosis, and higher sagittal vertical axis, indicating a higher risk of global decompensation. The SRS function scores and pain scores were also lower in the L group compared with the TL group. At a minimum of 2 years of follow-up, χ2 test showed that the incidence of TLS0 (+), LS0 (-), and LS0 (+) had significantly higher rates of MC (>40%). In both TL and L groups, patients with MC were found to have significantly lower bone mineral density than those without. CONCLUSION: The findings decipher the distinct patterns of sagittal imbalance in severe DK patients with kyphotic apex at thoracolumbar or lumbar spine. Patients with kyphotic apex apex at L2 or below, low SS, and global imbalance showed the highest risk of postoperative mechanical failure.

Preoperative supine pelvic incidence predicts standing pelvic incidence following S2AI fixation in patients with adult spinal deformity: a prospective study.

STUDY DESIGN: A prospective study. OBJECTIVE: The aim of this study was to investigate the PI change in different postures and before and after S2­alar­iliac (S2AI) screw fixation, and to investigate whether pre-op supine PI could predict post-op standing PI. Previous studies have reported PI may change with various positions. Some authors postulated that the unexpected PI change in ASD patients could be due to sacroiliac joint laxity, S2-alar-iliac (S2AI) screw placement, or aggressive sagittal cantilever technique. However, there was a lack of investigation on how to predict post-op standing PI when making surgical strategy. METHODS: A prospective case series of ASD patients undergoing surgical correction with S2AI screw placement was conducted. Full-spine X-ray films were obtained at pre-op standing, pre-op supine, pre-op prone, as well as post-op standing postures. Pelvic parameters were measured. Spearman correlation analysis was used to determine relationships between each parameter. RESULTS: A total of 83 patients (22 males, 61females) with a mean age of 58.4 ± 9.5 years were included in this study. Pre-op standing PI was significantly lower than post-op standing PI (p = 0.004). Pre-op prone PI was significantly lower than post-op standing PI (p = 0.001). By contrast, no significant difference was observed between pre-op supine and post-op standing PI (p = 0.359) with a mean absolute difference of 2.2° ± 1.9°. Correlation analysis showed supine PI was significantly correlated with post-op standing PI (r = 0.951, p < 0.001). CONCLUSION: This study revealed the PI changed after S2AI screw fixation. The pre-op supine PI can predict post-op standing PI precisely, which facilitates to provide correction surgery strategy with a good reference for ideal sagittal alignment postoperatively.

Gut Microbiota Alterations in Adolescent Idiopathic Scoliosis Are Associated with Aberrant Bone Homeostasis.

OBJECTIVE: Low bone mineral density is the major prognostic factor for adolescent idiopathic scoliosis (AIS), but the underlying mechanisms remain unclear. Accumulating evidence suggests that gut microbiota (GM) have the potential to affect bone development, and the GM signatures are altered in AIS patients. However, the effect of GM alterations on aberrant bone homeostasis in AIS remains unclear. This study aims to investigate the GM profile in AIS patients with different bone mineral density (BMD) and explore the association between GM, osteopenia, and aberrant bone turnover. METHODS: A total of 126 patients with AIS who received surgical treatment were retrospectively included in this study. We analyzed the composition of the GM by 16S rRNA sequencing and BMD by dual X-ray absorptiometry. Based on the BMD of the femur neck, the patients were divided into the osteopenia group (OPN) if the Z score < -1, and the normal (NOR) group if the Z score ≥ -1 SD compared to the healthy control. For the 16S rRNA sequencing, the raw reads were filtered to remove low-quality reads, and operational taxonomic units were identified with the Uparse program. Weighted UniFrac distance matrix for the beta-diversity metrics and principal coordinate analysis (PCoA) was performed, and the statistical comparisons were made with permutational multivariate analysis of variance (PERMANOVA) and analysis of similarity (ANONISM). Linear discriminant analysis effect size (LEfSe) was used to identify the enriched species in two groups. The "Random forest" was applied to determine the optimal biomarker for OPN according to the mean decrease in Gini value. The metabolic function was predicted by the Tax4Fun analysis. The Pearson correlation coefficient was used to evaluate the associations between GM species, bone turnover markers, and BMD. RESULTS: The serum ß-CTX was increased in the OPN group (n = 67) compared to the NOR group (n = 59). Patients in OPN groups showed significantly decreased α diversity indicated by the Shannon index. Principal coordinate analysis (PCoA) analysis showed significant clustering of GM between OPN and NOR groups. At genus level, the Escherichia-Shigella and Faecalibacterium were significantly enriched in the OPN group compared to that in the NOR group (p < 0.05), whereas the abundance of Prevotella was significantly decreased (p = 0.0012). The relative abundance of Megamonas and Prevotella was positively correlated with the femur BMD. The abundance of Escherichia-Shigella was negatively correlated with femur BMD and positively correlated with serum ß-CTX levels. Functional analysis revealed significant differences in starch and sucrose metabolism, pyruvate and cysteine, and methionine metabolism between NOR and OPN groups. CONCLUSION: The alterations of GM in AIS patients are correlated with osteopenia. The association between enriched species, BMD, and bone turnover markers provides novel diagnostic and therapeutic targets for the clinical management of AIS.

Assessment of malalignment at early stage in adolescent idiopathic scoliosis: a longitudinal cohort study.

INTRODUCTION: Our objective was to assess abnormalities of the odontoid-hip axis (OD-HA) angle in a mild scoliotic population to determine whether screening for malalignment would help predict the distinction between progressive and stable adolescent idiopathic scoliosis (AIS) at early stage. MATERIALS AND METHODS: All patients (non-scoliotic and AIS) underwent a biplanar X-ray between 2013 and 2020. In AIS, inclusion criteria were Cobb angle between 10° and 25°; Risser sign lower than 3; age higher than 10 years; and no previous treatment. A 3D spine reconstruction was performed, and the OD-HA was computed automatically. A reference corridor for OD-HA values in non-scoliotic subjects was calculated as the range [5th-95th percentiles]. A severity index, helping to distinguish stable and progressive AIS, was calculated and weighted according to the OD-HA value. RESULTS: Eighty-three non-scoliotic and 205 AIS were included. The mean coronal and sagittal OD-HA angles in the non-scoliotic group were 0.2° and -2.5°, whereas in AIS values were 0.3° and -0.8°, respectively. For coronal and sagittal OD-HA, 27.5% and 26.8% of AIS were outside the reference corridor compared with 10.8% in non-scoliotic (OR = 3.1 and 3). Adding to the severity index a weighting factor based on coronal OD-HA, for thoracic scoliosis, improved the positive predictive value by 9% and the specificity by 13%. CONCLUSION: Analysis of OD-HA suggests that AIS patients are almost three times more likely to have malalignment compared with a non-scoliotic population. Furthermore, analysis of coronal OD-HA is promising to help the clinician distinguish between stable and progressive thoracic scoliosis.

Potential impairment of spinal cord around the apical vertebral level in hyperkyphotic patients: findings from diffusion tensor imaging.

PURPOSE: To evaluate the neuronal metrics/microstructure of the spinal cord around apical region in patients with hyperkyphosis using diffusion tensor imaging (DTI). METHODS: Thirty-seven patients with hyperkyphosis aged 45.5 ± 19.6 years old who underwent 3.0 T magnetic resonance imaging (MRI) examination with DTI sequence were prospectively enrolled from July 2022 to July 2023. Patients were divided into three groups according to spinal cord/ cerebrospinal fluid (CSF) architecture on sagittal-T2 MRI of the thoracic apex (the axial spinal cord classification): Group A-circular cord with visible CSF, Group B-circular cord without visible CSF at apical dorsal, and Group C-spinal cord deformed without intervening CSF. The fractional anisotropy (FA) values acquired from DTI were compared among different groups. Correlations between DTI parameters and global kyphosis (GK)/sagittal deformity angular ratio (sagittal DAR) were evaluated using Pearson correlation coefficients. RESULTS: In all patients, FA values were significantly lower at apical level as compared with those at one level above or below the apex (0.548 ± 0.070 vs. 0.627 ± 0.056 versus 0.624 ± 0.039, P < 0.001). At the apical level, FA values were significantly lower in Group C than those in Group B (0.501 ± 0.052 vs. 0.598 ± 0.061, P < 0.001) and Group A (0.501 ± 0.052 vs. 0.597 ± 0.019, P < 0.001). Moreover, FA values were significantly lower in symptomatic group than those in non-symptomatic group (0.498 ± 0.049 v. 0.578 ± 0.065, P < 0.001). Pearson correlation analysis showed that GK (r2 = 0.3945, P < 0.001) and sagittal DAR (r2 = 0.3079, P < 0.001) were significantly correlation with FA values at apical level. CONCLUSION: In patients with hyperkyphosis, the FA of spinal cord at apical level was associated with the neuronal metrics/microstructure of the spinal cord. Furthermore, the DTI parameter of FA at apical level was associated with GK and sagittal DAR.

Development of ethnicity-adjusted global alignment and proportion score to predict the risk of mechanical complications following corrective surgery for adult spinal deformity.

BACKGROUND CONTEXT: Surgery for degenerative scoliosis (DS) is a complex procedure with high complication and revision rates. Based on the concept that pelvic incidence (PI) is a constant parameter, the global alignment and proportional (GAP) score was developed from sagittal alignment data collected in the Caucasian populations to predict mechanical complications. However, the PI varies among different ethnic groups, and the GAP score may not apply to Chinese populations. Thus, this study aims to assess the predictability of the GAP score for mechanical complications in the Chinese populations and develop an ethnicity-adjusted GAP score. PURPOSE: To test the predictability of the original GAP score in the Chinese population and develop a Chinese ethnicity-tailored GAP scoring system. STUDY DESIGN/SETTINGS: Retrospective cohort study. PATIENT SAMPLE: A total of 560 asymptomatic healthy volunteers were enrolled to develop Chinese ethnicity-tailored GAP (C-GAP) score and a total of 114 DS patients were enrolled to test the predictability of original GAP score and C-GAP score. OUTCOME MEASURES: Demographic information, sagittal spinopelvic parameters of healthy volunteers and DS patients were collected. Mechanical complications were recorded at a minimum of 2-year follow-up after corrective surgery for DS patients. METHODS: A total of 560 asymptomatic healthy volunteers with a mean age of 61.9±14.1 years were enrolled to develop ethnicity-adjusted GAP score. Besides, 114 surgically trated DS patients (M/F=10/104) with a mean age of 60.7±7.1 years were retrospectively reviewed. Demographic data and radiological parameters of both groups, including PI, lumbar lordosis (LL), sacral slope (SS), the sagittal vertical axis (SVA), and global tilt (GT) were collected. Ideal LL, SS, and GT were obtained by calculating their correlation with PI of healthy volunteers using linear regression analysis. Relative pelvic version (RPV), relative lumbar lordosis (RLL), lordosis distribution index (LDI), and relative spinopelvic alignment (RSA) were obtained using the ideal parameters, and the Chinese population adjusted GAP score (C-GAP) was developed based on these values. The predictability of original and C-GAP for mechanical failure was evaluated using clinical and radiological data of DS patients by evaluating the area under the curve (AUC) using receiver operating characteristic curve. This study was supported the National Natural Science Foundation of China (NSFC) (No. 82272545), ($ 8,000-10,000) and the Jiangsu Provincial Key Medical Center, and the China Postdoctoral Science Foundation (2021M701677), Level B ($ 5,000-7,000). RESULTS: Ideal SS=0.53×PI+9 (p=.002), ideal LL=0.48×PI+22 (p=.023) and ideal GT=0.46 × PI-9 (p=.011). were obtained by correlation analysis using sagittal parameters from those healthy volunteers, and RPV, RLL, RSA, and LDI were calculated accordingly. Then, the ethnicity-adjusted C-GAP score was developed by summing up the numeric value of calculated RPV, RLL, RSA, and LDI. The AUC was classified as ''no or low discriminatory power'' for the original GAP score in predicting mechanical complications (AUC=0.592, p=.078). Similarly, the original GAP score did not correlate with mechanical complications in DS patients. According to the C-GAP score, the sagittal parameters were proportional in 25 (21.9%) cases, moderately disproportional in 68 (59.6%), and severely disproportional in 21% (18.5%) cases. The incidence of mechanical complications was statistically different among proportioned and moderately disproportional and severely disproportional portions of the C-GAP score (p=.03). The predictability of the C-GAP score is high with an AUC=0.773 (p<.001). In addition, there is a linear correlation between mechanical complication rate and C-GAP score (χ=0.102, p=.02). CONCLUSION: The Ethnicity-adjusted C-GAP score system developed in the current study provided a more accurate and reliable for predicting the risk of mechanical complications after corrective surgery for adult spinal deformity.

Cosmetic evaluation in type II congenital scoliosis with long-spanned curve: a case-matched comparison with adolescent idiopathic scoliosis.

Background: There is an acknowledged discrepancy between radiographic and cosmetic parameters for patients with adolescent idiopathic scoliosis (AIS). However, no study has specifically evaluated cosmesis in patients with congenital scoliosis (CS). Therefore, the purpose of this study was to identify the cosmetic differences between patients with CS and case-matched patients with AIS and to investigate the correlation between radiological measurements and clinical cosmetic assessment indices. Methods: A total of 37 adolescents with CS and 37 sex-, age-, and curve magnitude-matched patients with AIS were included. Cobb angle, shoulder height difference (SHD), coronal balance (CB), T1 tilt, first rib angle (FRA), clavicle angle (CA), clavicle-rib cage intersection (CRCI), and apical vertebra translation (AVT) were measured in the full X-ray of the spine. Shoulder area index 1 (SAI1), shoulder area index 2 (SAI2), shoulder angle (SA), axilla angle (AA), thoracolumbar area index (TLAI), and right and left waist angle difference (RLWAD) were measured on the clinical images from a posterior view. Hump index (HI) was measured in the forward bending photography. All patients completed the Scoliosis Research Society-22 (SRS-22) questionnaire. Results: No significant difference was noted in the radiographic parameters between the AIS and CS groups (P>0.05). However, patients with CS exhibited significantly lower SAI1 (0.91 vs. 0.98; P=0.002) and SAI2 (0.85 vs. 0.95; P=0.001) than did the patients with AIS. The SRS-22 scores for self-image and mental health in patients with CS were significantly lower than those in patients with AIS (P<0.05). The correlation coefficients with statistical significance between radiographic and cosmetic measurements in patients with CS and those with AIS ranged from -0.493 to 0.534 and from -0.653 to 0.717, respectively. None of the correlation coefficients exceeded 0.8, indicating that the current radiological indices only exhibited a limited level of consistency with patients' cosmesis. Conclusions: As compared with age-, gender-, and curve pattern-matched patients with AIS, patients with CS exhibited worse cosmesis and had clinically significantly lower SRS-22 scores despite having relatively small clinical differences. Although the radiographic parameters may not always align with clinical presentation, this discrepancy could be observed in both patients with CS and those with AIS.

Selecting the Vertebra above Sagittal Stable Vertebra as the Distal Fusion Level in Scheuermann's Kyphosis: A Prospective Study with a Minimum of 2-Year Follow-Up.

OBJECTIVE: The proper selection of the lower instrumented vertebra (LIV) remains controversial in the surgical treatment of Scheuermann's disease and there is a paucity of studies investigating the clinical outcomes of fusion surgery when selecting the vertebra one level proximal to the sagittal stable vertebra (SSV-1) as LIV. The purpose of this study is to investigate whether SSV-1 could be a valid LIV for Scheuermann kyphosis (SK) patients with different curve patterns. METHODS: This was a prospective study on consecutive SK patients treated with posterior surgery between January 2018 and September 2020, in which the distal fusion level ended at SSV-1. The LIV was selected at SSV-1 only in patients with Risser >2 and with LIV translation less than 40 mm. All of the patients had a minimum of 2-year follow-up. Patients were further grouped based on the sagittal curve pattern as thoracic kyphosis (TK, n = 23) and thoracolumbar kyphosis (TLK, n = 13). Radiographic parameters including global kyphosis (GK), lumbar lordosis (LL), sagittal vertical axis (SVA), LIV translation, pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS) were measured preoperatively, postoperatively, and at the latest follow-up. The intraoperative and postoperative complications were recorded. The Scoliosis Research Society (SRS)-22 scores were performed to evaluate clinical outcomes. RESULTS: A total of 36 patients were recruited in this study, with 23 in the TK group and 13 in the TLK group. In TK group, the GK was significantly decreased from 80.8° ± 10.1° to 45.4° ± 7.7° after surgery, and was maintained at 45.3° ± 8.6° at the final follow-up. While in the TLK group, GK was significantly decreased from 70.7° ± 9.2° to 39.1° ± 5.4° after surgery (p < 0.001) and to 39.3° ± 4.5° at the final follow-up. Meanwhile, despite presenting with different sagittal alignment, significant improvement was observed in LL, SVA, and LIV translation for both TK and TLK groups (p < 0.05). Self-reported scores of pain and self-image in TK group and scores of self-image and function in TLK group showed significant improvement at the final follow-up (all p < 0.05). Distal junctional kyphosis (DJK) was observed in two patients (8.7%) in TK group, and one patient (7.7%) in TLK group. No revision surgery was performed. CONCLUSION: Selecting SSV-1 as LIV can achieve satisfactory radiographic and clinical outcomes for SK patients with different curve patterns without increasing the risk of DJK. This selection strategy could be a favorable option for SK patients with Risser sign >2 and LIV translation less than 40 mm.

The role of paraspinal muscle degeneration in coronal imbalance in patients with degenerative scoliosis.

Background: Coronal imbalance in degenerative scoliosis is common and is highly correlated with health-related quality of life. Paraspinal muscle is critical to spine stability, but little is known about its contribution to coronal imbalance in degenerative scoliosis. This study aims to investigate the relationship between paraspinal muscle (PSM) degeneration and coronal imbalance in patients with degenerative scoliosis (DS). Methods: This is a retrospective cohort study. A total of 117 patients with DS were retrospectively reviewed. Parameters of PSM (bilateral cross-sectional area, CSA; fat infiltration rate, FI%) at the apical disc and adjacent levels were quantitatively evaluated using MRI. Standing whole-spine radiograph was used to evaluate the coronal (Cobb angle, CA; coronal balance distance, CBD) and sagittal (thoracic kyphosis, TK; lumbar lordosis, LL; sagittal vertical axis, SVA) parameters. Patients were divided into 3 groups: coronal balanced (Type A), coronal imbalanced shifting to concavity (Type B), and coronal imbalanced shifting to convexity (Type C). Results: Based on our criteria, 56 patients were assigned to Type A, 34 patients to Type B, and 27 patients to Type C. There was no significant difference on the sagittal profiles and CSA between the groups. However, Type A showed significantly lower FI% than Type B and Type C on both concavity and convexity (Concave side: Type A vs. Type B vs. Type C, 30.8±8.1 vs. 45.1±7.7 vs. 38.7±12.5, P=0.001; Convex side: Type A vs. Type B vs. Type C, 32.6±10.9 vs. 46.3±7.3 vs. 40.7±11.8, P=0.004). Specifically, Cobb angle was negatively correlated with CSA, mainly at convexity (R=-0.415, P=0.008). Similarly, the increase of CBD significantly correlated with FI% at concavity (R=0.491, P=0.001) and convexity (R=0.354, P=0.025). Conclusions: DS patients with coronal imbalance demonstrated a worse PSM degeneration when compared with those without coronal imbalance. Besides, PSM degeneration strongly correlated with coronal imbalance, which implies that PSM degeneration may contribute to the coronal imbalance in patients with DS.

Surgical Treatment for Severe Cervical Hyperlordosis and Thoracolumar Kyphoscoliosis with Emery-Dreifuss Muscular Dystrophy: A Case Report and Literature Review.

BACKGROUND: Emery-Dreifuss muscular dystrophy (EDMD) is an uncommon, gradually progressive X-linked myopathy, and it could result in rigid spinal deformity. Only a few case reports have described surgical treatment of cervical hyperlordosis and thoracolumbar kyphoscoliosis secondary to EDMD. We report a rare case of EDMD to present the surgical strategies of severe cervical hyperlordosis and thoracolumbar kyphoscoliosis. CASE PRESENTATION: The patient was a 22-year-old man with EDMD who had severe cervical hyperlordosis and thoracolumbar kyphoscoliosis. A posterior spinal fusion from T9-S2 was performed to correct the thoracolumbar kyphoscoliosis at the age of 21 years. Six months later, with an anterior C7-T1 closing wedge bone-disc-bone osteotomy and a posterior-anterior-posterior cervicothoracic fusion from C4-T4, the cervical deformity was corrected, thus achieving a horizontal gaze. During 1.5-year follow-up, no loss of correction was observed. CONCLUSION: Cervical posterior-anterior-posterior closing-wedge osteotomy combined with long fusion at thoracolumbar spine can be a reliable surgical technique to correct severe spine deformity in EDMD. This two-stage revision surgical strategy can help restore a horizontal gaze on the basis of a balanced trunk. Cervical deformity in such patients should be corrected in the first stage considering its role as a "driver" of the global spine deformity.

Spine slenderness is not an early sign of progression in adolescent idiopathic scoliosis.

Adolescent idiopathic scoliosis (AIS) is a three-dimensional deformity of the spine. Spine slenderness, which represents its potential instability to buckling under compressive loads, was shown to be higher in AIS patients than non-scoliotic subjects, but it is not clear at what stage of the progression this difference appeared, nor if slenderness could be used as an early sign of progression. In this study, we hypothesized that slenderness could be an early sign of progression. One-hundred thirty-eight patients and 93 non-scoliotic subjects were included. They underwent standing biplanar radiography and 3D reconstruction of the spine, which allowed computing vertebra and disc slenderness ratio. Then, patients were followed until progression of the deformity or skeletal maturity (stable patients). Vertebral slenderness ratio in AIS patients varied between 2.9 [2.7; 3.0] (T9) and 3.4 [3.2; 3.6] (T1), while disc slenderness ranged from 0.6 [0.6; 0.7] at T6-T7 to 1.2 [1.1; 1.3] at L4-L5. Slenderness ratio increased with age, while disc slenderness tended to decrease with age and Cobb angle. Slenderness was similar between progressive and stable patients, and also between patients and non-scoliotic subjects. In conclusion, spinal slenderness does not appear to be an early sign of progression. Further studies should analyse the development of slenderness during growth, and how it could be affected by non-operative treatment.

Dynamic change of pelvic incidence after long fusion to pelvis with S2-alar-iliac screw: a 2-year follow-up study.

INTRODUCTION: Pelvic incidence (PI) is a key morphological parameter that reflects the relation between the sacrum and iliac wings. It is well accepted that PI remains constant after reaching maturity. However, recent studies indicated that PI might be altered after lumbosacral fusion. Additionally, it remains uncertain on the long-term influence of long fusion to pelvis with S2-alar-iliac screw on PI in patients with adult spinal deformity (ASD). STUDY DESIGN: A retrospective study. OBJECTIVE: To investigate whether and how PI would change during the follow-up in ASD patients who underwent S2AI fixation and to identify factors associated with the change in PI. METHODS: We retrospectively reviewed all ASD patients who underwent spinal surgery using S2AI screws between November 2014 and January 2017 at our institution. Patients with minimum follow-up of two years were included. The following sagittal radiographic parameters were measured: PI, Lumbar lordosis (LL), pelvic tilt (PT), PI-LL, sagittal vertical axis (SVA) at pre-op, post-op and 2-year follow-up. According to the changes in PI at immediate post-operation, patients were classified into two groups; Group A: Changes of PI less than or equal 5° and Group B: Changes of PI greater than 5°. RESULTS: A total of 82 ASD patients (Group A: 32, Group B: 50; mean age of 53.5 ± 12.6 years) with a mean follow-up period of 30.2 ± 9.2 months were included in this study. At immediate post-operation, Group A showed no significant change in PI (45.7° ± 11.4° to 45.3° ± 11.2°, p = 0.749); while Group B had a significant decrease in PI (51.6° ± 14.5° to 40.9° ± 14.0°, p < 0.001). At the last follow-up, 48% patients (24/50) in Group B had a significant increase in PI (32.8° ± 6.4° to 45.8° ± 11.2°, p < 0.001). Intergroup analysis showed that ΔPI, post-op PI, post-op PT and age were significantly different between both groups. In addition, pre-op PI, post-op PI, post-op PT, post-op PI-LL were significantly correlated with ΔPI at last follow-up. Also, logistic regression analysis showed that post-op PI was the associated risk factor (OR = 0.865, p = 0.024) for PI-LL mismatch. CONCLUSION: Our study showed that PI decreased in more than half of ASD patients immediately after spinal surgery using S2AI screws. Approximately 48% of them were able to recover during the 2-year follow-up. Lower pre-op PI, post-op PI and PT were found to be strongly associated with the return of PI. Thus, these current findings indicated that patients with a high PI at pre-operation should not be over-corrected to avoid PI-LL mismatch postoperatively.

The Establishment of a Mouse Model for Degenerative Kyphoscoliosis Based on Senescence-Accelerated Mouse Prone 8.

Objective: Degenerative kyphoscoliosis (DKS) is a complex spinal deformity associated with degeneration of bones, muscles, discs, and facet joints. The aim of this study was to establish an animal model of degenerative scoliosis that recapitulates key pathological features of DKS and to validate the degenerative changes in senescence-accelerated mouse prone 8 (SAMP8) mice. Methods: Thirty male mice were divided into 2 groups: 10 bipedal C57BL/6J mice were used as the control group, and 20 bipedal SAMP8 mice were used as the experimental group. Mice were bipedalized under general anesthesia. The incidence of scoliosis and bone quality was determined using radiographs and in vivo micro-CT images 4, 8, and 12 weeks after surgery, respectively. Histomorphological studies of muscle samples were performed after sacrifice at 12 weeks after surgery. Results: On the 12th week, the incidence rates of kyphosis in C57BL/6J and SAMP8 groups were 50% and 100%, respectively. Overall, the incidence and angle of kyphosis were significantly higher in the bipedal SAMP8 group compared to the C57BL/6J group (44.7°± 6.2° vs. 84.3°± 10.3°, P<0.001). Based on 3D reconstruction of the entire spine, degeneration of the intervertebral disc was observed in bipedal SAMP8 mice, including the reduction of disc height and the formation of vertebral osteophytes. The bone volume ratio (BV/TV) was significantly suppressed in the bipedal SAMP8 group compared with the bipedal C57BL/6J group. In addition, HE staining and Mason staining of the paraspinal muscle tissue showed chronic inflammation and fibrosis in the muscles of the bipedal SAMP8 group. Conclusions: The SAMP8 mouse model can be taken as a clinically relevant model of DKS, and accelerated aging of the musculoskeletal system promotes the development of kyphosis.

Which interventions may improve bracing compliance in adolescent idiopathic scoliosis? A systematic review and meta-analysis.

This review aimed to systematically review and meta-analyze the effects of interventions in improving bracing compliance among adolescent idiopathic scoliosis (AIS) patients. Eight databases were searched from their inception to April 2022. The eligibility criteria included controlled studies that used any type of intervention to enhance bracing compliance in braced AIS patients. Two researchers independently screened articles and extracted data based on the PICO (participant, intervention, comparator, and outcome) framework. Quality appraisal of included studies was performed using GRADE (overall assessment), and the risk of bias was assessed with Cochrane RoB Tool 2 for randomized controlled trials (RCT) and ROBINS-I for non-RCT studies. The primary outcome was bracing compliance and secondary outcomes included Cobb Angle and measurements for quality of life. Six eligible studies involving 523 participants were included. All studies were evaluated as low or very low quality with a high risk of bias. Four types of interventions were identified, including sensor monitoring (n = 2, RCTs), auto-adjusted brace (n = 1, RCT), more intensive or collaborated medical care (n = 2), and psychosocial intervention (n = 1). A meta-analysis of 215 patients from the three RCTs suggested that the compliance-enhancing intervention group had 2.92 more bracing hours per day than the usual care control (95%CI [1.12, 4.72], P = 0.001). In subgroup analysis, sensor monitoring significantly improved bracing wearing quantity compared to usual care (3.47 hours/day, 95%CI [1.48, 5.47], P = 0.001), while other aforementioned interventions did not show a significant superiority. Compliance-enhancing interventions may be favorable in preventing curve progression and promoting quality of life, but the improvements cannot be clarified according to limited evidence. In conclusion, although the results of this study suggested that sensor monitoring may be the most promising approach, limited high-quality evidence precludes reliable conclusions. Future well-designed RCTs are required to confirm the actual benefit of compliance-improving interventions in clinical practice.

The Utilization of Dual Second Sacral Alar-Iliac Screws for Spinopelvic Fixation in Patients with Severe Kyphoscoliosis.

OBJECTIVES: As a new pelvic fixation technique, the dual S2AI screws fixation technique could provide highly stable distal strength, and have wide clinical prospect in the correction of severe kyphoscoliosis. However, the ideal trajectory parameters, indications and clinical outcomes of this technique have not been reported so far. This study aimed to determine the anatomical parameters of dual S2AI screws in the normal Chinese adult population, investigating the indications of this technique and evaluating the feasibility and clinical outcomes. METHODS: Fifteen males and 15 females with normal pelvis underwent a pelvic CT scan to determine ideal dual S2AI screws trajectories. Sagittal angle (SA), transverse angle (TA), maximal length (ML), sacral length, and skin distance were measured. Subsequently, we retrospectively reviewed the data of 16 patients (seven males and nine females) who underwent dual S2AI screw fixation and 23 patients who underwent single S2AI screw fixation between January 2014 and December 2019. Preoperative, postoperative, and latest follow-up measurements of Cobb angle, coronal balance (CB), spinal pelvic obliquity (SPO), and regional kyphosis (RK) were obtained. The mean follow-up time was 16.7 ± 7.1 months (range: 12-30 months). Independent t-test was used to determine the difference in the analysis of the trajectories. The paired sample non-parametric Wilcoxon test was performed to assess the changes in radiographic parameters between different time points and different groups. RESULTS: For both male and females, the proximal S2AI screws had significantly higher TA and ML, but a lower SA than distal screws. Females showed significantly more caudal (SA: 25.03° ± 2.32° vs. 29.82° ± 2.47°, t = 7.742, P < 0.001) trajectories of distal screw. Additionally, ML in the females were significantly shorter than that in males (106.81 mm ± 6.79 mm vs. 101.63 mm ± 6.55 mm, t = 3.007, P = 0.003, 124.41 mm ± 7.57 mm vs. 116.23 mm ± 7.03 mm, t = 4.337, P < 0.001). Eight had unilateral and eight had bilateral dual S2AI screw placement. Respectively, both the single S2AI and dual S2AI groups showed significant postoperative improvement of Cobb angle, RK angle and SPO angle. In patients with dual S2AI screws fixation, two patients found that screws loosening occurred in one of dual screws at 1-year follow-up, and in patients with single S2AI screws fixation, six patients found screw loosing as well as two patients found screw breakage at 1-year follow-up. None of all patients had any prominent loss of correction. CONCLUSION: The ideal trajectory of dual S2AI screw could be well established. The dual S2AI screw fixation technique is feasible in patients with severe kyphoscoliosis, and provides satisfactory correction of deformity with few postoperative complications.

Global Alignment and Proportion (GAP) score in asymptomatic individuals: is it universal?

BACKGROUND: The global alignment and proportion (GAP) score was established based on American and European subjects, which might limit its applicability to the Chinese population due to ethnicity-related difference of sagittal alignment. PURPOSE: To analyze the applicability of GAP score in the Chinese population and to investigate the age- and gender-associated differences of spinopelvic and GAP score parameters. STUDY DESIGN: A prospective cross-sectional radiographic study. PATIENTS SAMPLE: Of 692 asymptomatic Chinese volunteers aged between 20 and 79 prospectively recruited between January 2017 and June 2019, 490 subjects were eventually included in this study. OUTCOME MEASURES: The pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), L1-S1 lordosis, L4-S1 lordosis, sagittal vertical axis (SVA), T1 pelvic angle (TPA) and global tilt (GT) were measured on lateral X-rays. The GAP scores and its parameters including relative pelvic version (RPV), relative lumbar lordosis (RLL), lordosis distribution index (LDI) and relative spinopelvic alignment (RSA) were calculated for each subject. METHODS: Subjects were divided into four groups: Group 1M: male subjects <60 years old; Group 1F: female subjects <60 years old; Group 2M: male subjects ≥60 years old and Group 2F: female subjects ≥60 years old. The GAP scores and categories were determined and compared between groups. The results of sagittal alignment were compared with the previous studies evaluating the normative sagittal alignment in other populations. Univariate linear regression analysis was carried out between pelvic incidence (PI) and sacral slope (SS), lumbar lordosis (LL) and global tilt (GT) in each group. RESULTS: The distributions of GAP categories and the updated Roussouly classification were statistically different from other populations. Significantly different distribution of GAP categories was observed between Group 1M and Group 2M, Group 1F and Group 2F, and Group 1M and Group 1F. Radiographic measurements and GAP parameters were significantly different between Group 1M and Group 2M, and Group 1F and Group 2F. Gender-related difference of parameters was more prominent between Group 1M and Group 1F. Linear relationship of PI with SS, LL and GT were different from the regression models of "ideal" sagittal alignment in GAP score. CONCLUSIONS: The GAP score might be inappropriate in Chinese population due to ethnicity-related alignment difference. Worse feasibility of GAP score was observed in female and old subjects.

An analysis on the determinants of head to pelvic balance in a Chinese adult population.

Background: Balanced global spinopelvic balance is important in the maintenance of the physiological alignment of all body segments above the pelvis with minimum energy expenditure. The key determinants affecting the 3D index-odontoid-hip axis (OD-HA) angle, and in particular its alterations, have not been clearly defined. The aim of this study is to identify the determinants of the 3D OD-HA angle in maintaining global spinopelvic balance in a large Chinese adult cohort of different gender and age groups. Methods: A total of 516 asymptomatic adults were enrolled in this study. Biplanar radiographies were performed to reconstruct the subject's inter-acetabular axis and C2 odontoid process. The 3D angle formed by the vertical and the line between odontoid and mid-interacetabular axis (OD-HA angle) was computed and projected in the subject's sagittal and coronal planes. Thoracic kyphosis (TK), lumbar lordosis (LL), T1 pelvic angle (TPA) and sagittal vertical axis (SVA) were measured. Results: The mean values of sagittal and coronal OD-HA were -0.2°±2.5° and 0.2°±1.1°, respectively. Both sagittal and coronal OD-HA had significant correlation with age (r=0.265 and r=-0.143, P<0.01, respectively), sagittal OD-HA showed increment from 20s to 80s (-1.3° to 0.8° for female, -0.3° to 1.5° for male) and a significant difference between male and female from 20 to 69 years old. Further analysis showed that sex, weight, TK, PT, SVA, TPA and ODI were determinants of OD-HA. Conclusions: 3D OD-HA angle showed physiological stability with little variability from young to elderly adults, with SD of 2.45° and 1.06° in sagittal and coronal planes, respectively. OD-HA angle confirms the hypothesis that the head tends to remain above the pelvis in a small cone of stability. This study provides an analysis of the determinants of OD-HA and the reference range of the head-pelvis balance in each decade and gender based on a large-scale asymptomatic population.

Bioinformatics Analysis and Experimental Verification Identify Downregulation of COL27A1 in Poor Segmental Congenital Scoliosis.

BACKGROUND: Congenital scoliosis (CS) represents the congenital defect disease, and poor segmental congenital scoliosis (PSCS) represents one of its types. Delayed intervention can result in disability and paralysis. In this study, we would identify the core biomarkers for PSCS progression through bioinformatics analysis combined with experimental verification. METHODS: This work obtained the GSE11854 expression dataset associated with somite formation in the GEO database, which covers data of 13 samples. Thereafter, we utilized the edgeR of the R package to obtain DEGs in this dataset. Then, GO annotation, KEGG analyses, and DO annotation of DEGs were performed by "clusterProfiler" of the R package. This study performed LASSO regression for screening the optimal predicting factors for somite formation. Through RNA sequencing based on peripheral blood samples from healthy donors and PSCS cases, we obtained the RNA expression patterns and screen out DEGs using the R package DESeq2. The present work analyzed COL27A1 expression in PSCS patients by the RT-PCR assay. RESULTS: A total of 443 genes from the GSE11854 dataset were identified as DEGs, which were involved in BP associated with DNA replication, CC associated with chromosomal region, and MF associated with ATPase activity. These DEGs were primarily enriched in the TGF-ß signaling pathway and spinal deformity. Further, LASSO regression suggested that 9 DEGs acted as the signature markers for somite formation. We discovered altogether 162 DEGs in PSCS patients, which were involved in BP associated with cardiac myofibril assembly and MF associated with structural constituent of muscle. However, these 162 DEGs were not significantly correlated with any pathways. Finally, COL27A1 was identified as the only intersected gene between the best predictors for somite formation and PSCS-related DEGs, which was significantly downregulated in PSCS patients. CONCLUSION: This work sheds novel lights on DEGs related to the PSCS pathogenic mechanism, and COL27A1 is the possible therapeutic target for PSCS. Findings in this work may contribute to developing therapeutic strategies for PSCS.

Selection of the optimal distal fusion level for Scheuermann kyphosis with different curve patterns: when can we stop above the sagittal stable vertebra?

PURPOSE: To investigate the optimal lowest instrumented vertebra (LIV) in the treatment of Scheuermann kyphosis (SK) with different curve patterns. METHODS: Fifty-two SK patients who underwent posterior surgery between January 2010 and December 2017 with a minimum follow-up of 2 years were retrospectively reviewed. Patients were divided into two groups based on the curve pattern: the Scheuermann thoracic kyphosis (STK group) or Scheuermann thoracolumbar kyphosis (STLK group). Based on the relationship between the sagittal stable vertebra (SSV) and LIV, both groups were further divided into the SSV group and SSV-1 group. Radiographic parameters, distal junctional kyphosis (DJK) incidence and SRS-22 questionnaire scores were evaluated. RESULTS: In STK and STLK groups, there were no significant differences in most pre- and postoperative radiographic assessments between SSV and SSV-1 subgroups. DJK incidence showed no significant differences between groups during follow-up (P > 0.05). LIV-PSVL was significantly more negative in the SSV-1 group than that in the SSV group (P < 0.001). Within the SSV-1 group, patients with DJK showed a more negative LIV-PSVL (P = 0.039). Moderate correlation was observed between preoperative LIV-PSVL and DJK with a Spearman coefficient of - 0.474 (P = 0.035). Receiver operative characteristic curve analysis showed that the threshold value of preoperative LIV-PSVL to predict DJK was - 37.35 mm (area under the curve 0.882). CONCLUSION: Shorter fusion stopping at SSV-1 achieved comparable clinical outcomes and did not increase the risk of DJK for both STK and STLK patients. For patients whose preoperative LIV-PSVL < - 37.35 mm, extending fusion to SSV is an acceptable solution to prevent DJK.