Lower limbs can play a major compensating role for sagittal malalignment; however, little is known about the different types of compensation. This study aimed to identify different patterns of lower limb compensation and to determine which parameters may affect the recruitment of knee flexion versus hip extension. This study included adult spinal deformity (ASD) patients with full-body X-rays in erect position from a multicentric prospective database. All parameters were measured at baseline: demographics, clinical scores and radiographic parameters: pelvic parameters, pelvic incidence-lumbar lordosis (PI-LL) mismatch, T1 pelvic angle (TPA), sacro-femoral angle (SFA), knee flexion angle (KA), ankle dorsi-flexion angle (AA), pelvic shift (PSh), hip and knee osteoarthritis (OA) grade. A K-means cluster analysis was conducted to identify patterns of lower limb compensation based on SFA and KA. The optimal number of clusters was determined using the silhouette score. The different parameters were then compared across clusters. 871 ASD patients were included, of whom 66.9

Study design. Multicentric prospective study. Objective. This study aimed to analyze lumbarized transitional vertebra (LTV) impact on spinal alignment, according to Castellvi grade, particularly regarding lumbar lordosis (LL) magnitude and distribution. Summary of Background Data. Few data is available regarding sagittal alignment in patients with LTV. Methods. Only healthy volunteers aged above 18 years with full-body biplanar radiograph were included. In case of LTV, the sixth lumbar vertebra was named “L0”, between T12 and L1. Pelvic and acetabular parameters, thoracic, cervical and global alignment were analyzed. LL was assessed through maximum, proximal and distal according to thoracolumbar inflection point and apex location as well as with fixed vertebrae: L1-S1, L1-L4 and L4-S1. Castellvi I and II were considered low-grade and Castellvi III and IV as high-grade LTV. Comparisons between the three groups (No, low-grade and high-grade) were performed, before and after matching on pelvic incidence (PI). Results. This study included 713 subjects (50.6% F, mean age: 37.5±16.2). 10.1% (n=72) presented transitional vertebra, of which 22 with lumbarization, 13 low-grade and 9 high-grade. PI was greater in LTV subjects. LLmax increased from -59.7±11.0° in No-LSTV subjects to -67.5±19.4° in high-grade LTV, mainly through proximal arc measured both through L1-L4 and LLprox. Lumbar apex was more cranial in LTV subjects: 5.9% in L3 in No-lumbarization cohort versus 53.9% and 44.4% respectively in low-grade and high-grade. A decreased lordosis in the transitional segment was partially compensated for by a steeper increase of LL above L5 in both LTV groups. After matching, LTV subjects presented lesser maximum lordosis than No-LTV subjects, driven by lesser distal lordosis, more anterior global alignment with greater T1PA and greater pelvic retroversion. Conclusions. Lumbarization individuals present decreased distal lordosis and a more cranial lumbar apex resulting in a more anteriorly tilted global sagittal alignment. Pelvic and spinal alignment parameters normative values are provided for LTV subjects.

BACKGROUND CONTEXT Despite advances in surgical techniques and the development of novel sagittal alignment targets, temporal trends of surgically achieved alignment goals have not been examined. PURPOSE Evaluate the evolution of achieved alignment following ASD surgeries. STUDY DESIGN/SETTING Retrospective multicenter registry of ASD surgeries (2008–2025). PATIENT SAMPLE A total of 1,166 ASD patients. OUTCOME MEASURES Sagittal alignment at 6 weeks and 2 years, SRS22 Satisfaction, and 2-year revision rates. METHODS Patients from two large multicenter ASD registries were reviewed and included if met the following criteria: preoperative SRS-Schwab type N or L treated with posterior fusion from thoracic (T1-12) to ilium. Patients were stratified into 3 surgical epochs: Epoch 1 (2008–2013), Epoch 2 (2014–2019), and Epoch 3 (2020–2025). Demographics and alignments were compared using ANOVA/Kruskal–Wallis with post hoc corrections. Alignment variance assessed via Levene testing (p<0.05). RESULTS A total of 1,166 patients were included (mean age 68.1 ± 8.4 and 67% females), with 182 in Epoch 1 (FU rate 82%), 472 in Epoch 2 (FU rate 67%) and 512 in Epoch 3 (FU rate 30%). Patient age increased across epochs (Epoch 1: 66±11 years; Epoch 3: 69±8 years, p<0.001) as well as lower proportion of females in Epoch 3 (61% vs 75%, p<0.001). Despite this, Epoch 3 demonstrated lower comorbidity burden (p<0.001), lower baseline ODI (p=0.003), and higher baseline SRS-22 total scores (p<0.001). Baseline spinopelvic parameters were largely comparable across epochs (no significant differences in PT, PI–LL, regional lordosis, or pelvic angles), though C7–S1 SVA decreased progressively across epochs (110.8 to 92.0 p=0.004).At 6 weeks, comparison of the mean demonstrated progressively larger L4–S1 lordosis (p<0.001), lower L1–S1 lordosis (p = 0.007), lower L1 pelvic angle (p=0.004), lower L1 pelvic angle offset from ideal (p=0.001), and greater T4–L1 pelvic angle (p<0.001). Concurrently, variance decreased over time for PI–LL mismatch (p=0.012), C7–S1 SVA (p=0.002), and L1 pelvic angle (p=0.02). In terms of correction, later epochs showed less change in PT (p=0.029), PI-LL mismatch (p=0.039), SVA (p=0.016), and T4L1PA (p<0.001) as well as greater change in L4-S1 (p=0.007). Additionally, the percentage of lumbar lordosis attributable to the distal segment (100 × L4–S1/LL) and the lordosis change attributable to the distal segment (100 × Δ[L4–S1]/Δ[LL]) increased across epochs. Severe radiographic PJK at 6 weeks progressively decreased across the epochs (10.5% vs 3.9%, p = 0.001). Satisfaction rates (SRS22r satisfaction median = 4.5; satisfaction ≥ 3.5 Epoch 1: 83%; Epoch 2: 80%; Epoch 3: 81%) and revision rates (Epoch 1: 20%; Epoch 2: 19%, Epoch 3: 14%) at 2 years did not significantly differ across epochs.Subgroup analysis showed similar evolution of sagittal alignment in upper thoracic and lower thoracic constructs, with the latter showing more focus on segmental lumbar lordosis in later epochs. CONCLUSIONS ASD alignment strategies have evolved, emphasizing distal LL restoration and reducing variability. While radiographic improvements are evident, satisfaction and revision rates have not significantly improved, highlighting a gap between radiographic and clinical outcomes. FDA Device/Drug Status This abstract does not discuss or include any applicable devices or drugs.

BACKGROUND CONTEXT Posterior spinal fusion for adolescent idiopathic scoliosis (AIS) aims to achieve coronal correction while restoring physiologic sagittal alignment. All-pedicle screw constructs provide strong coronal correction but may fail to restore thoracic kyphosis. Hybrid instrumentation using bands and hooks can improve sagittal alignment but may compromise coronal correction. Screw-and-band instrumentation (SBI) has emerged as a hybrid strategy to combine these advantages, though its effect on three-dimensional spinal alignment remains unclear. PURPOSE To compare regional sagittal alignment and thoracic kyphosis durability between hybrid instrumentation (HI) and screw-and-band constructs in AIS. STUDY DESIGN/SETTING Retrospective, single-center matched comparative study. PATIENT SAMPLE A total of 128 AIS patients (108 females, 20 males; mean age 14.7±1.6 years). OUTCOME MEASURES Coronal and sagittal spinopelvic alignment parameters over time. METHODS From a cohort of 300 pediatric patients undergoing posterior spinal fusion with HI or SBI, 128 were matched by sex and preoperative thoracic kyphosis (±5°). Standardized standing radiographs were analyzed preoperatively, immediately postoperatively, and at 2-year follow-up. Outcomes included number of fused levels, Cobb angles, global and regional thoracic kyphosis (TK), lumbar lordosis, and thoracolumbar junctional (TLJ) angle. Between-group comparisons were performed using independent t-tests, Mann-Whitney U tests, or chi-square tests. Longitudinal changes were assessed using repeated-measures ANOVA. RESULTS Preoperatively, the SBI group had significantly larger proximal, main, and distal Cobb angles than the HI group (+3.8°, +11.1°, and +4.5°, respectively; all p<0.05), while sagittal alignment was similar. At 2 years, both groups achieved significant coronal correction with comparable final alignment. Both demonstrated significant sagittal remodeling, with increased global TK and lumbar lordosis (SBI: +13.9° and +5.9°, p<0.001; HI: +16.4° and +3.2°, p<0.001), without significant intergroup differences. However, regional differences were observed: HI produced greater proximal TK (T1–T5) (+6.4°, p<0.001) and a more lordotic TLJ (+11°, p<0.001), while mid-thoracic kyphosis remained similar. Proximal junctional kyphosis rates were comparable (9% vs 5%, p=0.396). Loss of main Cobb correction was minimal and similar between groups (+1.5°, p=0.315). Although HI achieved greater immediate postoperative TK correction (+7.5°, p<0.001), differences were not sustained at 2 years (p=0.382). SBI involved more fused levels (median 11 vs 9, p<0.001), while HI demonstrated greater loss of fused TK over time (+6°, p<0.001). CONCLUSIONS Both HI and SBI constructs achieve comparable coronal correction and global sagittal alignment at 2 years but result in distinct regional sagittal morphologies. HI produces greater proximal TK and a more lordotic TLJ but is associated with greater loss of fused TK over time. SBI achieves similar final alignment with fewer fused levels and better maintenance of thoracic kyphosis. These findings highlight the influence of instrumentation strategy on postoperative spinal morphology and sagittal durability in AIS. FDA Device/Drug Status This abstract does not discuss or include any applicable devices or drugs.

Study Design. Retrospective study of a multicentric prospective database. Objective. This study aimed at describing the relative contribution of vertebral bodies versus discs to lumbar lordosis, and its variation with age and pelvic incidence. Summary of Background Data. While studies sought to determine the physiological magnitude and distribution of lumbar lordosis, data regarding its anatomical composition is lacking. Methods. This study included healthy volunteers with full-body stereoradiographs in free-standing position, without lumbosacral transitional vertebra or age under 18. The following parameters were analyzed: age, sex, pelvic incidence (PI), lumbar lordosis (LL). Posterior heights and sagittal Cobb angles between upper and lower endplate for each lumbar disc and each vertebral body were measured from L1 to S1. Ratios of contribution to LL were calculated for each disc and vertebral body. The cohort was divided into four age groups and four PI groups. Results. 645 subjects were included, mean age was 37.6±16.3, 51% of females. There was a significant decrease in total lumbar disc lordosis with age (−48.9±9.7° to −42.9±10.2°), occurring in lower LL. Vertebral bodies were significantly more kyphotic in Seniors than Youngs (−8.9±8.4° vs. −5.0±9.4°, P=0.03), driven by a significant increase in kyphosis of L1 and L2 bodies. Vertebral body contribution to LL significantly increased between groups as PI increased, from a median of 8.0% to 20.5% (P<0.001). This decrease in disc contribution in favor of vertebral bodies mainly took place in lower LL. Conclusion. This study highlights the importance of vertebral contribution to lumbar lordosis, ranging from 8 to 21% among PI groups. Lumbar lordosis decreased with aging through decreased disc lordosis in the lower lumbar spine and increased body kyphosis in the upper lumbar spine. These results may help surgeons in the assessment of sagittal alignment and the selection of operative technique to achieve surgical correction.

Study Design. Retrospective study of a multicentric prospective database. Objective. This study aimed to determine, in a cohort of healthy volunteers, the impact of sacralized lumbosacral transitional vertebra (LSTV) on spinal alignment according to its grade, particularly regarding lumbar lordosis magnitude and distribution, and the implications for spinopelvic parameters measurement. Summary of Background Data. There is little data regarding spinopelvic alignment assessment in LSTV patients. Methods. This study included healthy volunteers with full-body stereoradiographs in free-standing position aged over 18. Castellvi grade, pelvic parameters (measured on S1 and L5), L1-S1 lumbar lordosis (LL), and segmental lordosis for each disc and vertebral body, thoracic kyphosis, cervical lordosis, lower limb, and global alignment parameters were assessed. Castellvi I and II were considered as low-grade and Castellvi III and IV as high-grade LSTV. Alignment parameters between no-LSTV, low-grade, and high-grade LSTV were compared. Propensity score matching was used to match PI in No-LSTV and low-grades. Spinopelvic parameters measured on S1 in the no-LSTV group and on L5 in the high-grades were compared. Results. Seven hundred thirteen subjects were included, of whom 23 low-grades and 27 high-grades. The mean pelvic incidence was 51.0 +/- 11.0 degrees, and the mean age was 37.5 +/- 16.2 years. LL distribution was different between groups, with an apex and inflexion point significantly higher in high grade (P<0.001). Kyphosis in the LSTV segment was compensated for by a steeper increase of LL above L5 in the high-grades. Low-grades and PI-matched no-LSTV presented similar alignment parameters. There were minor differences in parameters measured on S1 in no-LSTV and no L5 in high-grades. Conclusions. Subjects with low-grade LSTV present similar alignment as PI-matched no-LSTV subjects and S1 should be taken as reference to measure spinopelvic parameters. High-grade LSTV subjects have kyphotic L5-S1 segment with more cranial lumbar apex and thoracolumbar inflexion point. In these subjects, spinopelvic parameters should be measured on L5.

Understanding the normal anatomy of thoracic kyphosis (TK) in healthy subjects is essential for evaluating sagittal malalignment and planning the surgery accordingly. The aim of this study was to identify the proportion of thoracic kyphosis originating from disc versus vertebral body shape and to describe its variation according to age and thoracic kyphosis magnitude. This study was a retrospective review of a prospective multicenter database of healthy volunteers aged 18 years or older. Vertebral body and disc sagittal Cobb angles were measured at each level and summed within each of the 3 TK regions (Upper, Middle and Lower TK). Relative contributions of discs and vertebral bodies to Upper, Middle, Lower, and total TK were assessed in the whole cohort, and according to age and TK groups, after stratification. Finally, a multivariate analysis including age and TK magnitude was conducted. Among these 645 subjects, the mean age was 37.6 ± 16.3 years with 51

Study design. Multicentric retrospective study of prospectively collected data. Objective. On the basis of normative data from a cohort of asymptomatic volunteers, this study sought to determine the rate of abnormal values of proximal junctional angles (PJA) in adult spinal deformity (ASD) surgery patients, and compare it with PJK rate. Summary of Background Data. Proximal junctional kyphosis (PJK) definition does not take the vertebral level into account. Patients and Methods. This study included 721 healthy volunteers and 824 ASD surgery patients with two-year postoperative follow-up. Normative values for each disc and vertebral body between T1 and T12 were analyzed, then normative values for PJA at each thoracic level were defined in the volunteer cohort as the mean +/- 2SD. PJA abnormal values at the upper instrumented vertebra (UIV) were compared with Glattes' and Lovecchio's definitions for PJK in the ASD population at two years. Results. Mean age was 37.7 +/- 16.3 in the volunteer cohort, with 50.5% of females. Mean thoracic kyphosis (TK) was -50.9 +/- 10.8 degrees. Corridors of normality included PJA greater than 20 degrees between T3 and T12. Mean age was 60.5 +/- 14.0 years in the ASD cohort, with 77.2% of females. Mean baseline TK was -37.4 +/- 19.9 degrees, with a significant increase after surgery (-15.6 +/- 15.3 degrees, P<0.001). There was 46.2% of PJK according to Glattes' versus 8.7% according to Lovecchio's and 22.9% of kyphotic PJA compared with normative values (P<0.001). Conclusion. This study provides normative values for segmental and regional alignment of thoracic spine, used to describe abnormal values of PJA for each level. Using level-adjusted PJA values allows a more precise assessment of abnormal proximal angles and question the definition for PJK.

Background/Objectives: The American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) and SpineSageTM risk calculators are automated online tools to predict short-term complications for surgical procedures. The objective of this study was to assess the validity of ACS-NSQIP and SpineSageTM risk calculators to predict short-term complications after adult spinal deformity (ASD) surgery. Methods: We included ASD patients who had surgery between 2017 and 2020 (≥5 levels, single-stage, posterior-only). Patient factors were entered into the risk calculators to generate probabilities for 30-day outcomes. Calibration and discrimination were assessed using Brier scores and C-statistics, respectively. Results: A total of 198 patients were included (67 male, 131 female) who underwent posterior spinal fusion for ASD surgery. The ACS-NSQIP risk calculator had strong calibration for all complications (Brier score < 0.09) except non-home discharge (Brier score 0.2). Discrimination was poor for all complications except surgical site infection (C-statistic 0.86), venous thromboembolism (C-statistic 0.84), and readmission (C-statistic 0.7). The SpineSageTM risk calculator had strong calibration for all complications (Brier score < 0.09) aside from the "any complications" subset (Brier score 0.36). The discrimination capacity was poor for all complications (C-statistic < 0.7). Conclusions: The ACS-NSQIP calculator had strong calibration and poor discrimination for most complications. The SpineSageTM calculator had strong calibration for most complications and a poor discrimination capacity for all complications. NSQIP calculation deficits may be due to the reliance on a single CPT code to calculate risk. The deficient discriminatory capacity of the SpineSageTM calculator may be due to the inclusion of common perioperative occurrences as complications.

STUDY DESIGN:A retrospective Cohort Study. OBJECTIVE:The aim of this study is to investigate the associations between posterior muscle health characteristics and disk geometry parameters between L1 and S1. SUMMARY OF BACKGROUND DATA:Paralumbar muscle changes have been associated with clinical outcomes. However, the relationship between disk geometry and paralumbar muscle changes has not been defined. METHODS:Axial T2 MRI was analyzed for paralumbar muscle measurements, and lateral radiographs were analyzed for disk geometry parameters in patients with disk degeneration. Associations between disk shape and muscle health at each individual lumbar level were evaluated using a partial correlation controlling for age and sex. Demographic data were compared between the listhesis groups, and an ANCOVA analysis controlling for significant demographic parameters was conducted to evaluate differences in muscle characteristics. RESULTS:In all, 435 patients were included (age: 55.6±15, BMI: 29.5±6, 60.9% female, 41.3% White). Muscle health median characteristics were CSA/BMI=140, LIV=13, and Goutallier Classification of 1. Partial correlations between focal disk parameters and muscle health controlling for age and sex showed moderate significant positive associations between focal lordosis and lumbar indentation value (LIV) at every level L1-S1 (mean r =0.264 between L1 and L5, P <0.001), weak positive association between focal lordosis and CSA/BMI (mean r =0.113 at L2-L5, P <0.03), and weak negative associations between disk height and Goutallier Classification (mean r =0.158 at L1-L5, P <0.03). Listhesis at L4-S1 was stratified, and ANCOVA controlling for sex and age demonstrated no significant association between S and R groups and CSA/BMI, LIV, or Goutallier classification ( P >0.1). CONCLUSIONS:Posterior muscle health was significantly associated with disk shape, especially disk height and disk lordosis, with larger and more lordotic disks being associated with better muscle health. Disk listhesis was not significantly associated with muscle quality when controlling for demographic characteristics, and no differences in muscle health parameters were observed in patients with spondylolisthesis versus retrolisthesis. Overall, the results highlight important associations between lumbar compensation, disk geometry, and posterior muscle health.

Study Design Retrospective cohort study. Objectives To evaluate whether different radiographic clusters of adult spinal deformity identified using artificial intelligence-based clustering are associated with distinct surgical outcomes. Methods Patients were classified based on the results of a previously conducted analysis that examined clusters of deformity, including Moderate Sagittal (Mod Sag), Severe Sagittal (Sev Sag), Coronal, and Hyper-Thoracic Kyphosis (Hyper-TK). The surgical data, HRQOL, and complication outcomes of these clusters were then compared. Results The final analysis included 1062 patients. Similar to published results on a different patient sample, Mod Sag and Sev Sag patients were older, more likely to have a history of previous spine surgery, and more disabled. By 2-year, all clusters improved in HRQOL and reached a similar rate of minimal clinically important difference (MCID). The Sev Sag cluster had the highest rate major complications (53% vs 34-40%), and complications leading to reoperation (29% vs 17-23%), implant failures (20% vs 8-11%), and operative complications (27% vs 10-17%). Coronal patients had the highest rate of pulmonary complications (9% vs 3-6%) but the lowest rate of X-ray imbalance (10% vs 19-21%). No significant differences were found in neurological complications, infection rate, gastrointestinal, or cardiac events (all P > .1). Kaplan-Meier survival curves demonstrated a lower time to first complications for the Sev Sag cluster. Conclusions All clusters of adult spinal deformity benefit similarly from surgery as they all achieved similar rates of MCID. Although the rates of complications varied among the clusters, the types of complications were not significantly different.

Previous work comparing ASD to a normative population demonstrated that a large proportion of lumbar lordosis is lost proximally (L1-L4). The current study expands on these findings by collectively investigating regional angles and spinal contours. 119 asymptomatic volunteers with full-body free-standing radiographs were used to identify age-and-PI models of each Vertebra Pelvic Angle (VPA) from L5 to T10. These formulas were then applied to a cohort of primary surgical ASD patients without coronal malalignment. Loss of lumbar lordosis (LL) was defined as the offset between age-and-PI normative value and pre-operative alignment. Spine shapes defined by VPAs were compared and analyzed using paired t-tests. 362 ASD patients were identified (age = 64.4 ± 13, 57.1

BACKGROUND CONTEXT Predicting postoperative changes in thoracic kyphosis (TK) and anticipating reciprocal changes in the unfused thoracic spine is challenging in adult spinal deformity (ASD) surgery. Little is known about TK morphology in ASD patients before and after surgical correction. PURPOSE This study aimed to quantify iatrogenic and reciprocal changes in TK between pre and post-surgery and identify influencing parameters, assess the maintenance of unfused thoracic curvature between early and 2-year follow-up, and identify parameters affecting proximal failure. STUDY DESIGN/SETTING Retrospective analysis of prospective data. PATIENT SAMPLE A total of 362 ASD patients with no previous thoracic/thoracolumbar fusion were treated with posterior instrumentation with upper instrumented vertebra (UIV) from T9-11 to the pelvis, with a minimum 2-year follow-up. OUTCOME MEASURES Thoracic sagittal curvatures (global, regional, and segmental) at early and late follow-ups. METHODS After describing preoperative information, corrections performed, and early postoperative alignment, independent parameters associated with TK changes were identified using multilinear regression analysis. Thoracic kyphosis values and distribution were reported and compared to normative values. Thoracic relaxation between 6 weeks and 2 years was assessed. Multilinear hierarchical regression was used to investigate postoperative lumbar parameters associated with reciprocal change. The rate of thoracic failure was reported, and logistic regression was used to investigate associated risk factors. RESULTS In this cohort (65±9 yo, 73.5% female), most of the deformities were either pure sagittal (48.6%) or with a lumbar curve (42.0%). The median preoperative T1-T12 TK (median 34°) was normal for 59.7% and hypo-kyphotic for 39.3% of patients. Early postop, 88.3% of patients with normal preop TK remained normal, and 79.1% of hypo-kyphotic patients normalized their TK. There was a reciprocal increase in kyphosis across T5-T10 (+7°) and iatrogenic increase across T10-L1 (+7°). In a multilinear regression analysis, the increase in postoperative TK was significantly associated with an increase in L1-S1 lordosis (beta -0.481 p<0.001) and a decrease in postoperative L4-S1 lordosis (beta 0.152 p<0.012) (r-square 0.69 std error 8.7°). From early postop to 2-years, 9.1% experienced a global TK decompensation greater than 15° and 9.4% sustained a proximal extension due to junctional issues (collectively coined thoracic failures = 17.1%). Multivariate analysis showed early postop thoracic alignment was a significant predictor of 2-year thoracic failure based on T10-L1 <15° and T5-T10 contribution to TK < 38%. CONCLUSIONS Following ASD surgery with the UIV at T9-T11, deviations in thoracic kyphosis within nonfused segments increase the likelihood of revision surgery. Despite achieving thoracic kyphosis normalization in most cases, postoperative spinal shape often strays from the norm. Accurate postoperative thoracic kyphosis estimation is possible with preoperative alignment and lumbar correction. A two-year failure trend is associated with early postoperative lower kyphosis and the distribution of thoracic curvature, emphasizing the importance of meticulous preoperative planning. FDA Device/Drug Status This abstract does not discuss or include any applicable devices or drugs.

Study design. Multicentric retrospective study of prospectively collected data. Objective. On the basis of normative data from a cohort of asymptomatic volunteers, this study sought to determine the rate of abnormal values of proximal junctional angles (PJA) in adult spinal deformity (ASD) surgery patients, and compare it with PJK rate. Summary of Background Data. Proximal junctional kyphosis (PJK) definition does not take the vertebral level into account. Patients and Methods. This study included 721 healthy volunteers and 824 ASD surgery patients with two-year postoperative follow-up. Normative values for each disc and vertebral body between T1 and T12 were analyzed, then normative values for PJA at each thoracic level were defined in the volunteer cohort as the mean±2SD. PJA abnormal values at the upper instrumented vertebra (UIV) were compared with Glattes’ and Lovecchio’s definitions for PJK in the ASD population at two years. Results. Mean age was 37.7±16.3 in the volunteer cohort, with 50.5% of females. Mean thoracic kyphosis (TK) was -50.9±10.8°. Corridors of normality included PJA greater than 20° between T3 and T12. Mean age was 60.5±14.0 years in the ASD cohort, with 77.2% of females. Mean baseline TK was -37.4±19.9°, with a significant increase after surgery (-15.6±15.3°, P<0.001). There was 46.2% of PJK according to Glattes’ versus 8.7% according to Lovecchio’s and 22.9% of kyphotic PJA compared with normative values (P<0.001). Conclusion. This study provides normative values for segmental and regional alignment of thoracic spine, used to describe abnormal values of PJA for each level. Using level-adjusted PJA values allows a more precise assessment of abnormal proximal angles and question the definition for PJK. Level of evidence: Level II.

Study DesignRetrospective cohort.ObjectiveDetermine effects of bracing on proximal junctional kyphosis (PJK) after adult deformity correction.MethodsPatients were identified from a single-surgeon dataset of posterior-only fusions for ASD (pelvis to UIV of T9-12) with a minimum of 1-year follow up. Starting in 2021, all lower thoracic fusions were braced using a hyperextension brace. Patients wore the brace at all times (unless in bed) for the first 6 weeks after surgery. A 1:1 propensity-match was performed based on age, number of levels, 3 column osteotomies, and magnitude of correction to identify a comparative non-braced cohort.Results141 patients (113 non-brace, 28 brace) were evaluated. After matching, 56 patients were identified to form similar cohorts. Non-matched and matched groups had no statistically significant differences in demographics, comorbid conditions, surgical characteristics (except shorter operative time and lower EBL in the braced group), and preoperative radiographic parameters. For the overall cohort, the change in proximal junctional angle at 1-year was higher in the non-braced group (7.6° vs 8.1°, P = .047), and non-braced patients had a higher incidence of PJK at 1-year in both the overall cohort (36% vs 14%, P = .045) and matched cohort (43% vs 14%, P = .038). There was no difference in proximal junctional failure between groups.ConclusionThis pilot study shows that our protocol for extension bracing may reduce rates of PJK. These findings can form the basis for future multi-center trials examining the effect of extension bracing on junctional complications.

Study Design. This is a multicenter, prospective cohort study. Objective. This study tests the hypothesis that the elimination of lower limb compensation in patients with adult spinal deformity (ASD) will significantly increase the magnitude of sagittal malalignment. Summary of Background Data. ASD affects a significant proportion of the elderly population, impairing functional sagittal alignment and inhibiting the overall quality of life. To counteract these effects, patients with ASD use their spine, pelvis, and lower limbs to create a compensatory posture that allows for standing and mobility. However, the degree to which each of the hips, knees, and ankles contributes to these compensatory mechanisms has yet to be determined. Methods. Patients undergoing corrective surgery for ASD were included if they met at least one of the following criteria: complex surgical procedure, geriatric deformity surgery, or severe radiographic deformity. Preoperative full-body x-rays were evaluated, and age and pelvic incidence -adjusted normative values were used to model spine alignment based upon three positions: compensated (all lower extremity compensatory mechanisms maintained), partially compensated (removal of ankle dorsiflexion and knee flexion, with maintained hip extension), and uncompensated (ankle, knee, and hip compensation set to the age and pelvic incidence norms). Results. A total of 288 patients were included (mean age 60 yr, 70.5% females). As the model transitioned from the compensated to uncompensated position, the initial posterior translation of the pelvis decreased significantly to an anterior translation versus the ankle (P.Shift: 30 to −7.6 mm). This was associated with a decrease in pelvic retroversion (pelvic tilt: 24.1–16.1), hip extension (SFA: 203–200), knee flexion (knee angle: 5.5–0.4), and ankle dorsiflexion (ankle angle: 5.3–3.7). As a result, the anterior malalignment of the trunk significantly increased: sagittal vertical axis (65–120 mm) and G-SVA (C7-ankle from 36 to 127 mm). Conclusions. Removal of lower limbs compensation revealed an unsustainable truncal malalignment with two-fold greater SVA.

Study Design. This is a multicenter, prospective cohort study. Objective. This study tests the hypothesis that the elimination of lower limb compensation in patients with adult spinal deformity (ASD) will significantly increase the magnitude of sagittal malalignment. Summary of Background Data. ASD affects a significant proportion of the elderly population, impairing functional sagittal alignment and inhibiting the overall quality of life. To counteract these effects, patients with ASD use their spine, pelvis, and lower limbs to create a compensatory posture that allows for standing and mobility. However, the degree to which each of the hips, knees, and ankles contributes to these compensatory mechanisms has yet to be determined. Methods. Patients undergoing corrective surgery for ASD were included if they met at least one of the following criteria: complex surgical procedure, geriatric deformity surgery, or severe radiographic deformity. Preoperative full-body x-rays were evaluated, and age and pelvic incidence -adjusted normative values were used to model spine alignment based upon three positions: compensated (all lower extremity compensatory mechanisms maintained), partially compensated (removal of ankle dorsiflexion and knee flexion, with maintained hip extension), and uncompensated (ankle, knee, and hip compensation set to the age and pelvic incidence norms). Results. A total of 288 patients were included (mean age 60 yr, 70.5% females). As the model transitioned from the compensated to uncompensated position, the initial posterior translation of the pelvis decreased significantly to an anterior translation versus the ankle (P.Shift: 30 to −7.6 mm). This was associated with a decrease in pelvic retroversion (pelvic tilt: 24.1–16.1), hip extension (SFA: 203–200), knee flexion (knee angle: 5.5–0.4), and ankle dorsiflexion (ankle angle: 5.3–3.7). As a result, the anterior malalignment of the trunk significantly increased: sagittal vertical axis (65–120 mm) and G-SVA (C7-ankle from 36 to 127 mm). Conclusions. Removal of lower limbs compensation revealed an unsustainable truncal malalignment with two-fold greater SVA.

STUDY DESIGN:This is a retrospective case-control study. OBJECTIVES:The objectives of this study are to identify (1) risk factors for delayed ambulation following adult spinal deformity (ASD) surgery and (2) complications associated with delayed ambulation. METHODS:One-hundred and ninety-one patients with ASD who underwent posterior-only fusion (≥5 levels, LIV pelvis) were reviewed. Patients who ambulated with physical therapy (PT) on POD2 or later (LateAmb, n = 49) were propensity matched 1:1 to patients who ambulated on POD0-1 (NmlAmb, n = 49) based on the extent of fusion and surgical invasiveness score (ASD-S). Risk factors, as well as inpatient medical complications were compared. Logistic regressions were used to identify risk factors for late ambulation. RESULTS:Of the patients who did not ambulate on POD0-1, 32% declined participation secondary to pain or dizziness/fatigue, while 68% were restricted from participation by PT/nursing due to fatigue, inability to follow commands, nausea/dizziness, pain, or hypotension. Logistic regression showed that intraoperative estimated blood loss (EBL) >2L (OR = 5.57 [1.51-20.55], P = .010) was independently associated with an increased risk of delayed ambulation, with a 1.25 times higher risk for every 250 mL increase in EBL (P = .014). Modified 5-Item Frailty Index (mFI-5) was also independently associated with delayed ambulation (OR = 2.53 [1.14-5.63], P = .023). LateAmb demonstrated a higher hospital LOS (8.4 ± 4.0 vs 6.2 ± 2.6, P < .001). The LateAmb group trended toward an increase in medical complications on POD3+ (14.3% vs 26.5%, P = .210). CONCLUSIONS:EBL demonstrates a dose-response relationship with risk for delayed ambulation. Delayed ambulation increases LOS and may impact medical complications.

Study Design/Setting: Retrospective review of a prospectively collected database. Objective: The objective of this study was to determine the relationship between paracervical muscle area, density, and fat infiltration and cervical alignment among patients presenting with cervical spine pathology. Background Context: The impact of cervical spine alignment on clinical outcomes has been extensively studied, but little is known about the association between spinal alignment and cervical paraspinal musculature. Methods: We examined computed tomography scans and radiographs for patients presenting with cervical spine pathology. The posterior paracervical muscle area, density, and fat infiltration was calculated on axial slices at C2, C4, C6, and T1. We measured radiographic parameters including cervical sagittal vertical axis, cervical lordosis, T1 slope (T1S), range of motion of the cervical spine. We performed Pearson correlation tests to determine if there were significant relationships between muscle measurements and alignment parameters. Results: The study included 51 patients. The paracervical muscle area was higher for males at C2 (P=0.005), C4 (P=0.001), and T1 (P=0.002). There was a positive correlation between age and fat infiltration at C2, C4, C6, and T1 (all P<0.05). The cervical sagittal vertical axis positively correlated with muscle cross-sectional area at C2 (P=0.013) and C4 (P=0.013). Overall cervical range of motion directly correlated with muscle density at C2 (r=0.48, P=0.003), C4 (r=0.41, P=0.01), and C6 (r=0.53. P<0.001) and indirectly correlated with fat infiltration at C2 (r=−0.40, P=0.02), C4 (r=−0.32, P=0.04), and C6 (r=−0.35, P=0.02). Muscle density correlated directly with reserve of extension at C2 (r=0.57, P=0.009), C4 (r=0.48, P=0.037), and C6 (r=0.47, P=0.033). Reserve of extension indirectly correlated with fat infiltration at C2 (r=0.65, P=0.006), C4 (r=0.47, P=0.037), and C6 (r=0.48, P=0.029). Conclusions: We have identified specific changes in paracervical muscle that are associated with a patient’s ability to extend their cervical spine.

Study Design Retrospective cohort study. Objectives Investigate a composite score to evaluate the relationship between alignment proportionality and risk of distal junctional kyphosis (DJK). Methods 84 patients with minimum 1 year follow-up were included (age = 61.1 ± 10.3 years, 64.3% women). The Cervical Score was constructed using offsets from age-adjusted normative values for sagittal vertical axis (SVA), T1 Slope (TS), and TS minus cervical lordosis (CL). Individual points were assigned based on offset with age-adjusted alignment targets and summed to generate the Cervical Score. Rates of mechanical failure (DJK revision or severe DJK [DJK> 20° and ΔDJK> 10°]) were assessed overall and based on Cervical Score. Logistical regressions assessed associations between early radiographic alignment and 1-year failure rate. Results Mechanical failure rate was 21.4% (N = 18), 10.7% requiring revision. By multivariate logistical regression: 3-month T1S (OR: .935), TS-CL (OR:0.882), and SVA (OR:1.015) were independent predictors of 1-year failure (all P < .05). Cervical Score ranged (−6 to 6), 37.8% of patients between −1 and 1, and 50.0% with 2 or higher. DJK patients had significantly higher Cervical Score (4.1 ± 1.3 vs .6 ± 2.2, P < .001). Patients with a score ≥3 were significantly more likely to develop a failure (71.4%) with OR of 38.55 (95%CI [7.73; 192.26]) and Nagelkerke r2 .524 (P < .001) Conclusion This study developed a composite alignment score predictive of mechanical failures in CD surgery. A score ≥3 at 3 months following surgery was associated with a marked increase in failure rate. The Cervical Score can be used to analyze sagittal alignment and help define realignment objectives to reduce mechanical failure.