Global Alignment Parameters Research Articles

The Implications of Sacralized Transitional Vertebra on Spinal Alignment.

Retrospective study of a multicentric prospective database. This study aimed to determine, in a cohort of healthy volunteers, the impact of sacralized lumbo-sacral transitional vertebra (LSTV) on spinal alignment according to its grade, particularly regarding lumbar lordosis magnitude and distribution, and the implications for spinopelvic parameters measurement. There is little data regarding spinopelvic alignment assessment in LSTV patients. 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- 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 No-LSTV group and on L5 in High-grade were compared. 713 subjects were included, of whom 23 Low-grades and 27 High-grades. Mean pelvic incidence was 51.0±11.0° and 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. 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.

Analysis of the reliability of KEOPS version 2 for the measurement of coronal and sagittal parameters in spinal deformity.

The purpose of the study is to evaluate the updated version of this software in patients with various spinal deformity. Sixty patients were included in this study and were divided into three categories: 20 patients with AIS, 20 patients with ASD, and 20 patients having undergone corrective surgery for spinal deformity. The measurements were performed by two senior and two junior orthopedic surgery residents, and were done at two points in time separated by a 3-week interval with the cases being randomized every time to reduce the risk of memory bias. Measured parameters included coronal, sagittal, global alignment parameters, andpelvic parameters. When assessing the inter- and intra-observer reliability across all the groups of patients, none of the coefficients was smaller than 0.8 with a very high level of agreement. The standard error ranged from 0.7° to 1.5° demonstrating a high level of accuracy. Fairly similar results were seen when the groups were divided into the three categories except for the post-operative groups where a strong and not perfect level of agreement was reported. This is the first study to assess the reproducibility of the new version of KEOPS, showing a very high agreement in all measurements. In the post-operative group, although it showed a strong agreement, the lower performance can be explained by the presence of surgical material making it harder to identify the anatomical landmarks accurately. Nevertheless, we can recommend the usage of this software in a clinical setting.

Artificial Intelligence Assistance for the Measurement of Full Alignment Parameters in Whole-Spine Lateral Radiographs

BackgroundMeasuring spinal alignment with radiological parameters is essential in patients with spinal conditions likely to be treated surgically. These evaluations are not usually included in the radiological report. As a result, spinal surgeons commonly perform the measurement, which is time-consuming and subject to errors. We aim to develop a fully automated artificial intelligence tool to assist in measuring alignment parameters in whole-spine lateral radiograph (WSL X-rays). Material and MethodsWe developed a tool called Vertebrai that automatically calculates the global spinal parameters (GSP): Pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), L1-L4 angle, L4-S1 lumbo-pelvic angle, T1 pelvic angle (TPA), sagittal vertical axis (SVA), cervical lordosis (CL), C1-C2 lordosis, lumbar lordosis (LL), mid-thoracic kyphosis (MTK), proximal thoracic kyphosis (PTK), global thoracic kyphosis (GTK), T1 slope (T1S), C2-C7 plummet (cSVA), spino-sacral angle (SSA), C7 tilt (C7T), global tilt (GT), spinopelvic tilt (T1SPi) and hip odontoid axis (OD-HA). We assessed human-AI interaction instead of AI performance alone. We compared the time to measure GSP and inter-rater agreement with and without AI assistance. Two institutional datasets were created with 2267 multilabel images for classification, and 784 WSL X-rays with reference standard landmark labeled by spinal surgeons. ResultsVertebrai significantly reduced the measurement time comparing spine surgeons with AI assistance and the AI algorithm alone, without human intervention (3 minutes vs 0.26 minutes; p < 0.05). Vertebrai achieved an average accuracy of 83% in detecting abnormal alignment values, with the SS parameter exhibiting the lowest accuracy at 61.5% and T1SPi demonstrating the highest accuracy at 100%. Intra-class correlation analysis revealed a high level of correlation and consistency in the global alignment parameters. ConclusionsVertebrai's measurements can accurately detect alignment parameters, making it a promising tool for measuring GSP automatically.

Global Sagittal Angle and T9-tilt seem to be the most clinically and functionally relevant global alignment parameters in patients with Adult Spinal Deformity

IntroductionRadiographic analysis is necessary for the assessment and the surgical planning in adults with spinal deformity (ASD). Restoration of global alignment is key to improving patient's quality of life. However, the large number of existing global alignment parameters can be confusing for surgeons. Research questionTo determine the most clinically and functionally relevant global alignment parameters in ASD. Material and methodsASD and controls underwent full body biplanar X-ray to calculate global alignment parameters: odontoid to hip axis angle (OD-HA), global sagittal angle (GSA), global tilt (GT), SVA, center of auditory meatus to hip axis (CAM-HA), SSA, T1-tilt and T9-tilt. All subjects filled HRQoL questionnaires: ODI, SF-36, VAS for pain and BDI (Beck's Depression Inventory). 3D gait analysis was performed to calculate kinematic and spatio-temporal parameters. A machine learning model predicted gait parameters and HRQoL scores from global alignment parameters. Results124 primary ASD and 47 controls were enrolled. T9 tilt predicted the most BDI (31%), hip flexion/extension during gait (36%), and double support time (39%). GSA predicted the most ODI (26%), thorax flexion/extension during gait (33%), and cadence (36%). Discussion and conclusionAmong all global alignment parameters, GSA, evaluating both trunk shift and knee flexion, and T9 tilt, evaluating the shift of the center of mass, were the best predictors for most of HRQoL scores and gait kinematics. Therefore, we recommend using GSA and T9 tilt in clinical practice when evaluating ASD because they represent the most quality of life and functional kinematic of these patients.

Functional assessment using 3D movement analysis can better predict health-related quality of life outcomes in patients with adult spinal deformity: a machine learning approach.

Adult spinal deformity (ASD) is classically evaluated by health-related quality of life (HRQoL) questionnaires and static radiographic spino-pelvic and global alignment parameters. Recently, 3D movement analysis (3DMA) was used for functional assessment of ASD to objectively quantify patient's independence during daily life activities. The aim of this study was to determine the role of both static and functional assessments in the prediction of HRQoL outcomes using machine learning methods. ASD patients and controls underwent full-body biplanar low-dose x-rays with 3D reconstruction of skeletal segment as well as 3DMA of gait and filled HRQoL questionnaires: SF-36 physical and mental components (PCS&MCS), Oswestry Disability Index (ODI), Beck's Depression Inventory (BDI), and visual analog scale (VAS) for pain. A random forest machine learning (ML) model was used to predict HRQoL outcomes based on three simulations: (1) radiographic, (2) kinematic, (3) both radiographic and kinematic parameters. Accuracy of prediction and RMSE of the model were evaluated using 10-fold cross validation in each simulation and compared between simulations. The model was also used to investigate the possibility of predicting HRQoL outcomes in ASD after treatment. In total, 173 primary ASD and 57 controls were enrolled; 30 ASD were followed-up after surgical or medical treatment. The first ML simulation had a median accuracy of 83.4%. The second simulation had a median accuracy of 84.7%. The third simulation had a median accuracy of 87%. Simulations 2 and 3 had comparable accuracies of prediction for all HRQoL outcomes and higher predictions compared to Simulation 1 (i.e., accuracy for PCS = 85 ± 5 vs. 88.4 ± 4 and 89.7% ± 4%, for MCS = 83.7 ± 8.3 vs. 86.3 ± 5.6 and 87.7% ± 6.8% for simulations 1, 2 and 3 resp., p < 0.05). Similar results were reported when the 3 simulations were tested on ASD after treatment. This study showed that kinematic parameters can better predict HRQoL outcomes than stand-alone classical radiographic parameters, not only for physical but also for mental scores. Moreover, 3DMA was shown to be a good predictive of HRQoL outcomes for ASD follow-up after medical or surgical treatment. Thus, the assessment of ASD patients should no longer rely on radiographs alone but on movement analysis as well.

Associated factors and effects of coronal vertebral wedging angle in thoracic adolescent idiopathic scoliosis

BackgroundAdolescent idiopathic scoliosis (AIS) causes vertebral wedging, but associated factors and the impact of vertebral wedging are still unknown. We investigated associated factors and effects of vertebral wedging in AIS using computed tomography (CT). MethodsPreoperative patients (n = 245) with Lenke types-1 and 2 were included. Vertebral wedging, lordosis, and rotation of the apical vertebra were measured by preoperative CT. Skeletal maturity and radiographic global alignment parameters were evaluated. Multiple regression analysis was performed on associated factors for vertebral wedging. Side-bending radiographs were evaluated using multiple regression analysis to calculate the percentage of reduction of Cobb angles to determine curve flexibility. ResultsThe mean vertebral wedging angle was 6.8 ± 3.1°. Vertebral wedging angle was positively correlated with proximal thoracic (r = 0.40), main thoracic (r = 0.54), and thoracolumbar/lumbar curves (r = 0.38). By multiple regression, the central sacral vertical line (p = 0.039), sagittal vertical axis (p = 0.049), main thoracic curve (p = 0.008), and thoracolumbar/lumbar curve (p = 0.001) were significant factors for vertebral wedging. In traction and side-bending radiographs there were positive correlations between curve rigidity and the vertebral wedging angle (r = 0.60, r = 0.59, respectively). By multiple regression, thoracic kyphosis (p < 0.001), lumbar lordosis (p = 0.013), sacral slope (p = 0.006), vertebral wedging angle (p = 0.003), and vertebral rotation (p = 0.002) were significant factors for curve flexibility. ConclusionsVertebral wedging angle was found to be highly correlated to coronal Cobb angle, with larger vertebral wedging indicating less flexibility.

Impact of the preoperative nutritional status on postoperative kyphosis in geriatric patients undergoing cervical laminoplasty.

This study aimed to determine the association of preoperative malnutrition with an increased risk of cervical kyphosis after laminoplasty in geriatric patients with cervical spondylotic myelopathy (CSM). Geriatric patients who underwent cervical laminoplasty were included. Malnutrition was defined as a geriatric nutritional risk index < 98 before surgery. The C2-7 angle and the global alignment parameters were analyzed on standing radiographs. The postoperative kyphosis was defined as a C2-7 angle < 0° during a 2-year follow-up. Ninety patients without preoperative kyphotic alignment were enrolled (mean age, 73.5years old; 41.1% female). Twenty-one patients (23.3%) had malnutrition status (74.2years old). Preoperatively, the global alignment parameters were comparable between the malnutrition and normal nutrition groups (SVA, 43.3mm vs. 42.4mm; T1S, 29.7° vs. 28.4°; TPA, 21.4° vs. 17.8°), with no significant difference in the C2-7 angle (15.1° vs. 15.2°). At 2years postoperatively, the malnutrition group showed a significantly lower C2-7 angle than the normal nutrition group (9.3° vs. 15.8°, P = 0.03). Postoperative kyphosis was more prevalent in the malnutrition group (33.3% vs. 7.2%, P = 0.005). The preoperative nutritional status and C2-7 angle were independent predictors of postoperative kyphosis. The predictive C2-7 angles differed by preoperative nutritional status (malnutrition group, 11°; normal nutrition group, 7°). Among geriatric CSM patients, preoperative malnutrition was closely associated with the increased occurrence of cervical kyphosis after laminoplasty. Our results underscore the importance of preoperative nutritional assessment and management in geriatric populations undergoing cervical spine surgery, as malnutrition is a perioperative modifiable risk factor.

What are the most clinically and functionally relevant global alignment parameters used in the assessment of spinal deformity?

What are the most clinically and functionally relevant global alignment parameters used in the assessment of spinal deformity?

Does the asymmetry and extension function of the preoperative cervical paraspinal extensor predict postoperative cervical sagittal deformity in patients who undergo modified laminoplasty?

BACKGROUND CONTEXTA previous study found that the cross-sectional area (CSA) of the preoperative cervical paraspinal extensors (CPEs) was associated with loss of cervical lordosis after laminoplasty, while a recent study found that CPE asymmetry was associated with symptoms of degenerative cervical myelopathy. Whether preoperative CPE asymmetry can predict cervical sagittal deformity (CSD) after laminoplasty is unknown. PURPOSETo assess whether asymmetry, degree of degeneration, and extension function of the CPE can be used as predictors of postoperative CSD in patients who undergo laminoplasty. STUDY DESIGNA retrospective study. PATIENT SAMPLEFrom January 2017 to December 2019, 55 patients with multilevel cord compression and myelopathic symptoms were enrolled. OUTCOME MEASURESThe visual analog scale (VAS), neck disability index (NDI), and modified Japanese Orthopedic Association (mJOA) were used to assess cervical spinal function and quality of life. METHODSFrom January 2017 to December 2019, 55 patients undergoing modified laminoplasty were included. The following parameters were measured preoperatively and 24 months postoperatively on X-ray: (1) C0–C2 Cobb angle; (2) C2–C7 Cobb angle (CL); (3) T1 slope (T1S); (5) C2–C7 sagittal vertical axis (SVA); (6) T1S minus CL; (7) Preoperative extension function: Extension CL minus Neutral CL (EF). Preoperative global alignment parameters: (8) spino cranial angle, (9) C7-S1 sagittal vertical axis (C7 SVA), (10) pelvic incidence, (11) lumbar lordosis, (12) thoracic kyphosis. (13) Preoperative CPE parameters: Summation of bilateral total cross-sectional area (STCSA), summation of bilateral total cross-sectional area ratio (STCSAR), total cross-sectional area asymmetry, summation of bilateral functional cross-sectional area of muscle (SFCSA), summation of bilateral functional cross-sectional area of muscle ratio (FCSAR), and functional cross-sectional area of muscle asymmetry (FCSAA). The VAS, mJOA, and NDI were used to evaluate cervical spine function and quality of life. Patients were divided into the CSD group and the non-deformed group (N-CSD) group postoperatively, and the parameters between the two groups were compared. The Pearson correlation coefficient was used to evaluate the relationship between the parameters, and multiple regression analysis and ROC curve analysis were used to determine the predictors and key values. RESULTSCompared with functional scores, mJOA in the CSD group was significantly lower than that in the N-CSD group, while NDI and VAS were significantly higher. Postoperative CL was significantly correlated with EF, SFCSA/STCSA (C3–C6), SFCSAR (C4 and C6), STCSAR (C6), and FSCAA (C6). T1S minus CL was significantly correlated with EF, SFCSA/STCSA (C3–4 and C6), SFCSAR (C4 and C6), STCSAR (C6) and FSCAA (C6). C2–7 SVA was significantly correlated with EF, SFCSAR (C4 and C6), STCSAR (C6), and FSCAA (C6). Multiple regression analysis showed that FCSAA (C6), SFCSAR (C6), SFCSAR (C4), and EF were significant predictors of postoperative CSD. ROC curve analysis showed that the optimal cutoff points were 18.405, 2.95, 4.47, and 11.96. CONCLUSIONSThe present study found that preoperative extension dysfunction of CPEs, asymmetry at the C6 level cervical extensors, and cervical extensor CSAs without fatty infiltration at the C4 and C6 levels were associated with cervical sagittal imbalance after modified laminoplasty. These factors can be considered when future spine surgeons formulate surgical plans.

Variation of Global Sagittal Alignment Parameters According to Gender, Pelvic Incidence, and Age.

Retrospective cross-sectional study. The aim was to describe existing global sagittal alignment parameters across ages and to analyze differences according to gender and pelvic incidence (PI). Variability with age has been reported. It remains unclear how gender and spinopelvic morphology could additionally influence global alignment parameters. Radiographs of 2599 individuals (5-93 y) were analyzed. Translation parameters were: Sagittal Vertical Axis (SVA)-C7, SVA-C2, SVA-Center Acoustic Meatus (CAM), C7/Sacrofemoral Distance (SFD) ratio. Inclination parameters were: C7-Vertical Tilt (VT), T1-VT and T9-VT, Odontoid-Hip Axis (OD-HA), OD-CAM. Pelvic compensation parameters were: T1-Pelvic Angle (TPA), Global Tilt (GT), Spino-Sacral Angle (SSA). Global sagittal alignment (GSA) was considered among formulae. The distribution of parameters was analyzed using a Bayesian inference. Correlations with spinopelvic parameters were investigated. SVA-C7, SVA-C2, SVA-CAM were larger in males and high PI, and increased significantly after 50 years (Pr>0.9999). C7/SFD decreased during growth and was larger in low PI (Pr=0.951). There was no correlation with spinopelvic parameters. Age-related variations of inclination parameters were nonsignificant. T1-VT and T9-VT increased with PI and were significantly larger in high PI (Pr>0.95). C7-VT was significantly larger in low PI (Pr>0.9999). OD-HA and OD-CAM were constant and increased after 80 years. TPA and GT increased with PI (Pr>0.9999) and age after 35 years (Pr>0.9999). SSA decreased nonsignificantly after 50 years. TPA correlated with PI (ρ=0.6130) and pelvic tilt (PT) (ρ=0.8375). GT correlated with PI (ρ=0.5961) and PT (ρ=0.8996). SSA correlated with sacral slope (ρ=0.9026). GSA was larger in high PI (Pr>0.9999) and increased after 35 years (Pr>0.9999). GSA correlated with PT (ρ=0.7732). Translation parameters increase with age, more prominently in males and high PI. Variations of inclination parameters are smaller. Pelvic compensation parameters and GSA increase with age and are closely related to PT and spinopelvic morphology. Level III.

Variation of cervical sagittal alignment parameters according to gender, pelvic incidence and age.

The aim was to describe radiographic cervical sagittal alignment variations according to age, gender and pelvic incidence (PI) and to investigate relationships with thoracic alignment. A total of 2599 individuals (5-93years) without spinal deformity were studied. Cranial cervical parameters were: McGregor slope, occipita-C2 angle, McGregor-C2 lordosis and C1-C2 lordosis. Caudal cervical parameters were: C2-C7, cranial arch and caudal arch lordosis and C7- and T1-slope. A Bayesian inference compared parameter distributions. Correlations with spinopelvic and global alignment parameters were investigated. Among cranial cervical parameters, variations of McGregor slope were non-significant. McGregor-C2 lordosis and C1-C2 lordosis were smaller in males and increased significantly during growth, whereas the occipito-C2 angle decreased (Pr > 0.95). The occipito-C2 angle was larger and McGregor-C2 lordosis was smaller in low PI (Pr > 0.95). Among caudal cervical parameters, C2-C7 lordosis and C7- and T1-slope were larger in males and increased after 50years (Pr > 0.95). Lordosis changes were non-significant in the cranial arch, whereas values increased in the caudal arch after 35years (Pr > 0.95). Caudal parameter differences were non-significant between PI groups. Strong correlations existed between C2-C7, caudal arch lordosis, C7-slope, T1-slope and thoracic kyphosis. The sagittal vertical axis C2 correlated with caudal arch lordosis and T1-slope (ρ > 0.5; Pr > 0.95). Cervical alignment parameters vary according to age, gender and PI. In the cranial cervical spine, changes occur mainly during growth. In the caudal cervical spine, lordosis increases in the caudal arch, which is related to thoracic kyphosis increase with age. The caudal cervical arch acts as a compensatory segment by progressive extension, allowing horizontal gaze.

What are the most clinically and functionally relevant global alignment parameters?

What are the most clinically and functionally relevant global alignment parameters?

Institution-wide shape analysis of 3D spinal curvature and global alignment parameters.

The spine is an articulated, 3D structure with 6 degrees of translational and rotational freedom. Clinical studies have shown spinal deformities are associated with pain and functional disability in both adult and pediatric populations. Clinical decision making relies on accurate characterization of the spinal deformity and monitoring of its progression over time. However, Cobb angle measurements are time-consuming, are limited by interobserver variability, and represent a simplified 2D view of a 3D structure. Instead, spine deformities can be described by 3D shape parameters, addressing the limitations of current measurement methods. To this end, we develop and validate a deep learning algorithm to automatically extract the vertebral midline (from the upper endplate of S1 to the lower endplate of C7) for frontal and lateral radiographs. Our results demonstrate robust performance across datasets and patient populations. Approximations of 3D spines are reconstructed from the unit normalized midline curves of 20,118 pairs of full spine radiographs belonging to 15,378 patients acquired at our institution between 2008 and 2020. The resulting 3D dataset is used to describe global imbalance parameters in the patient population and to build a statistical shape model to describe global spine shape variations in preoperative deformity patients via eight interpretable shape parameters. The developed method can identify patient subgroups with similar shape characteristics without relying on an existing shape classification system.

Effect of age-adjusted alignment goals and distal inclination angle on the fate of distal junctional kyphosis in cervical deformity surgery

Background:Age-adjusted alignment targets in the context of distal junctional kyphosis (DJK) development have yet to be investigated. Our aim was to assess age-adjusted alignment targets, reciprocal changes, and role of lowest instrumented level orientation in DJK development in cervical deformity (CD) patients.Methods:CD patients were evaluated based on lowest fused level: cervical (C7 or above), upper thoracic (UT: T1–T6), and lower thoracic (LT: T7–T12). Age-adjusted alignment targets were calculated using published formulas for sagittal vertical axis (SVA), pelvic incidence-lumbar lordosis (PI-LL), pelvic tilt (PT), T1 pelvic angle (TPA), and LL-thoracic kyphosis (TK). Outcome measures were cervical and global alignment parameters: Cervical SVA (cSVA), cervical lordosis, C2 slope, C2–T3 angle, C2–T3 SVA, TS-CL, PI-LL, PT, and SVA. Subanalysis matched baseline PI to assess age-adjusted alignment between DJK and non-DJK.Results:Seventy-six CD patients included. By 1Y, 20 patients developed DJK. Non-DJK patients had 27% cervical lowest instrumented vertebra (LIV), 68% UT, and 5% LT. DJK patients had 25% cervical, 50% UT, and 25% LT. There were no baseline or 1Y differences for PI, PI-LL, SVA, TPA, or PT for actual and age-adjusted targets. DJK patients had worse baseline cSVA and more severe 1Y cSVA, C2–T3 SVA, and C2 slope (P < 0.05). The distribution of over/under corrected patients and the offset between actual and ideal alignment for SVA, PT, TPA, PI-LL, and LL-TK were similar between DJK and non-DJK patients. DJK patients requiring reoperation had worse postoperative changes in all cervical parameters and trended toward larger offsets for global parameters.Conclusion:CD patients with severe baseline malalignment went on to develop postoperative DJK. Age-adjusted alignment targets did not capture differences in these populations, suggesting the need for cervical-specific goals.

Impact of Spinopelvic sagittal alignment on the surgical outcomes of dropped head syndrome: a multi-center study

BackgroundMost of the previous studies about the surgical treatment of dropped head syndrome (DHS) are small case series, and their primary outcome measures were cervical alignment parameters. Therefore, little is known about the associations between pre- and postoperative global sagittal alignment in the whole spine and the clinical outcomes of the surgical treatment of DHS. In this study, we investigated the surgical outcomes of DHS, including correction of cervical and global spinal sagittal alignment.MethodsThis study was a retrospective observational study. Fifteen patients with DHS who had undergone correction surgery were enrolled. Surgical outcomes, including complications and implant failures, were investigated. We assessed cervical alignment parameters as well as spinopelvic global alignment parameters, including pelvic incidence (PI), lumbar lordosis (LL), and C7-sacral sagittal vertical axis (SVA). We examined the changes in these parameters using pre- and posoperative whole spine lateral radiographs. The parameters were compared between the failure and nonfailure groups.ResultsRecurrence of sagittal imbalance and horizontal gaze difficulty was observed in 6 cases (40%). In all, 3 cases (20%) exhibited a distal junctional failure and required multiple surgeries with extension of fusion. Of all the radiographic parameters compared between the failure and nonfailure groups, significant differences were only observed in pre and postoperative SVA and PI-LL.ConclusionsOur results suggest that the global sagittal alignment parameters, including PI-LL and SVA, were different between the patients with failure and non failure, and these parameters might have notable impacts on surgical outcomes. Surgeons should consider PI-LL and SVA while determining the surgical course for patients with DHS.

A review of cervical spine alignment in the normal and degenerative spine.

With recent advancements in surgical spine technology and techniques, the importance of regional and global spine alignment has become an important factor in surgical planning. Our review aims to consolidate the current literature on cervical and global alignment parameters and its relationship to cervical symptomatology, quality of life (QOL), requirements for surgery, potential surgical complications and health-related quality of life (HRQOL) outcomes.

The Impact of Adult Thoracolumbar Spinal Deformities on Standing to Sitting Regional and Segmental Reciprocal Alignment.

Regional and segmental changes of the lumbar spine have previously been described as patients transition from standing to sitting; however, alignment changes in the cervical and thoracic spine have yet to be investigated. So, the aim of this study was to assess cervical and thoracic regional and segmental changes in patients with thoracolumbar deformity versus a nondeformed thoracolumbar spine population. This study was a retrospective cohort study of a single center's database of full-body stereoradiographic imaging and clinical data. Patients were ≥ 18 years old with nondeformed spines (nondegenerative, nondeformity spinal pathologies) or thoracolumbar deformity (ASD: PI-LL > 10°). Patients were propensity-score matched for age and maximum hip osteoarthritis grade and were stratified by Scoliosis Research Society (SRS)-Schwab classification by PI-LL, SVA, and PT. Patients with lumbar transitional anatomy or fusions were excluded. Outcome measures included changes between standing and sitting in global alignment parameters: sagittal vertical axis (SVA), pelvic incidence minus lumbar lordosis (PI-LL), pelivc tilt (PT), thoracic kyphosis, cervical alignment, cervical SVA, C2-C7 lordosis (CL), T1 slop minus CL (TS-CL), and segmental alignment from C2 to T12. Another analysis was performed using patients with cervical and thoracic segmental measurements. A total of 338 patients were included (202 nondeformity, 136 ASD). After propensity-score matching, 162 patients were included (81 nondeformity, 81 ASD). When categorized by SRS-Schwab classification, all nondeformity patients were nonpathologically grouped for PI-LL, SVA, and PT, whereas ASD patients had mix of moderately and markedly deformed modifiers. There were significant differences in pelvic and global spinal alignment changes from standing to sitting between nondeformity and ASD patients, particularly for SVA (nondeformed: 49.5 mm versus ASD: 27.4 mm; P&thinsp;< .001) and PI-LL (20.12° versus 13.01°, P < .001). With application of the Schwab classification system upon the cohort, PI-LL (P = .040) and SVA (P = .007) for severely classified deformity patients had significantly less positional alignment change. In an additional analysis of patients with segmental measurements from C2 to T12, nondeformity patients showed significant mobility of T2-T3 (-0.99° to -0.54°, P = .023), T6-T7 (-3.39° to -2.89°, P = .032), T7-T8 (-2.68° to -2.23°, P = .048), and T10-T11 (0.31° to 0.097°, P = .006) segments from standing to sitting. ASD patients showed mobility of the C6-C7 (1.76° to 3.45°, P < .001) and T11-T12 (0.98° to 0.54°, P = 0.014) from standing to sitting. The degree of mobility between nondeformity and ASD patients was significantly different in C6-C7 (-0.18° versus 1.69°, P = .003), T2-T3 (0.45° versus -0.27°, P = .034), and T10-T11 (0.45° versus -0.30°, P = .001) segments. With application of the Schwab modifier system upon the cohort, mobility was significant in the C6-C7 (nondeformed: 0.18° versus moderately deformed: 2.12° versus markedly deformed: 0.92°, P = .039), T2-T3 (0.45° versus -0.08° versus -0.63°, P = .020), T6-T7 (0.48° versus 0.36° versus -1.85°, P = .007), and T10-T11 (0.45° versus -0.21° versus -0.23°, P = .009) segments. Nondeformity patients and ASD patients have significant differences in mobility of global spinopelvic parameters as well as segmental regions in the cervical and thoracic spine between sitting and standing. This study aids in our understanding of flexibility and compensatory mechanisms in deformity patients, as well as the possible impact on unfused segments when considering deformity corrective surgery.

Cervical spine alignment following surgery for adolescent idiopathic scoliosis (AIS): a pre-to-post analysis of 81 patients

BackgroundSeveral studies have emphasized the importance of restoring thoracic kyphosis (TK) in the setting of AIS, but very few have discussed changes in cervical spine alignment following surgery. Aim of this study was to evaluate reciprocal cervical alignment change after modification of global and regional thoracolumbar alignment with surgery in the setting of adolescent idiopathic scoliosis (AIS).MethodsBaseline and 2-yrs follow-up radiographs of AIS patients (n = 81) were analysed measuring cervical parameters (upper cervical: C2-C0, McGregor Slope; lower cervical: C2-C7, C2-C7 sagittal vertical axis (SVA), C2-T3, C2-T3SVA, C2-T1Harrison (C2-T1Ha), T1 Slope (T1S)), thoracic, lumbar, pelvic and global alignment parameters. Post-operatively, patients were grouped twice; based on changes in TK and SVA. Cervical alignment was compared between groups. Pearson correlation was conducted to examine the relationship between changes in TK, SVA, and cervical alignment.ResultsStratification by change in TK, revealed significant alteration of lower cervical alignment T1S [p < 0.001]), C2-T3 [p = 0.019], C2-T1Ha [p = 0.043]), but there was no reciprocal change in the upper cervical spine. Stratification by SVA revealed a significant coexisting change in the lower cervical spine (T1S [p < 0.001], C2-C7SVA [p = 0.034], C2-T3 [p = 0.023], C2-T3SVA [p = 0.001]). SVA change was not associated to a change in the upper cervical spine. The correlation analysis showed that with a post-operative increase in TK, the cervical spine became more lordotic. Changes in TK were significantly correlated with: ΔT1S, ΔC2-C7, ΔC2-T3, and ΔC2-T3SVA. Similarly, increased cervical kyphosis was found when SVA was decreased post-operatively. Furthermore, there was a significant correlation between change of SVA and both ΔC2-T3 and ΔC2-T3SVA.ConclusionsIn surgically treated AIS patients, changes in global and regional alignment of the thoracolumbar and cervical spinal segments exhibit interdependence. Thus, surgical planning with regard to sagittal deformity in AIS patients should account for the post-operative impact on cervical alignment.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters: P83. Development of a novel cervical deformity surgical invasiveness index

BACKGROUND CONTEXT A surgical invasiveness index exists for general spine surgery and adult spinal deformity, but a cervical deformity (CD) index has not been developed. PURPOSE The aim of this study was to develop a novel surgical invasiveness index for CD surgery that incorporates CD-specific parameters. STUDY DESIGN/SETTING Retrospective review of a multicenter prospective CD database. PATIENT SAMPLE Eighty-five CD patients with complete baseline demographic, clinical, and surgical details and 1-year data. OUTCOME MEASURES Cervical and global alignment parameters: cSVA, cervical lordosis, C2 slope, C2-T3 angle, C2-T3 SVA, TS-CL, PI-LL, PT, and SVA. METHODS CD was defined as at least one of the following: C2–C7 Cobb>10°, CL>10°, cSVA>4 cm, CBVA>25°. Consensus from experienced spine and neurosurgeons selected weightings for each variable that went into the invasiveness index. Linear regression was used to predict operative time, EBL, and length of stay using the newly developed CD-specific invasiveness index, controlling for age, sex, and Charlson Comorbidity Index score. Binary logistic regression predicted high operative time (>338 minutes), high EBL (>600 cc), or high length of stay (>5 days) based on the median values of operative time, EBL and length of stay. Significance was set at P RESULTS Eighty-five CD patients were included (61.35±10.7years, 65.9% female). The variables included in the newly developed CD invasiveness index with their corresponding weightings were: history of prior cervical surgery (3), ACDF (2 per level), corpectomy (4 per level), levels fused (1 per level), implants (1 per level), posterior decompression (2 per level), Smith–Peterson osteotomy (2 per level), three column osteotomy (8 per level), fusion to upper cervical spine (2), absolute change in TS-CL, cSVA, T4-T12 thoracic kyphosis and SVA from baseline to 1-year follow-up. The newly developed CD invasiveness index was a significant independent predictor of estimated blood loss (R2=0.132, P=.042). This CD-specific index was also a significant independent predictor of operative time (R2=0.171, P=.004). CD-specific invasiveness index strongly predicted a hospital length of stay greater than 5days (R2=0.310, P CONCLUSIONS Extended length of stay, operative time, and high blood loss werestrongly predicted by the newly developed CD invasiveness index, incorporating surgical factors and radiographic parameters clinically relevant for patients undergoing cervical deformity corrective surgery.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters: P17. Regional and segmental changes of the spine from standing to sitting: a chain of compensation

BACKGROUND CONTEXT Regional and segmental changes of the lumbar spine have previously been described as patients transition from standing to sitting, however alignment changes in the cervical and thoracic spine have yet to be investigated. PURPOSE The aim of this study was to assess cervical and thoracic regional and segmental changes in patients with normal spinal pathologies. STUDY DESIGN/SETTING Retrospective review of a single center database of full-body stereoradiographic imaging and clinical data. PATIENT SAMPLE A total of 207 patients with nondegenerative, nondeformity spinal pathology. OUTCOME MEASURES Global alignment parameters: sagittal vertical axis (SVA), PI-LL, PT, TK. Cervical alignment: cSVA, C2–C7 lordosis (CL), T1 slope minus CL (TS-CL). Segmental changes in alignment from C2 to T12 between standing and sitting radiographs. METHODS Patients age >18years old with nondegenerative, nondeformity spinal pathologies. Patients with lumbar degenerative conditions or thoracolumbar deformity were excluded. Sub-analysis was performed of patients with cervical and thoracic segmental measurements. RESULTS A total of 207 patients were included (age 51±16years, BMI 26.7±6 kg/m2). As patients transitioned from standing to sitting, there was an increase in pelvic tilt of 12.2° (11.9°–24.2°), an increase in PI-LL by 22.8° (−7.1°–15.7°), and increase in SVA by 53.3 mm (−4.2 mm to 49.2 mm, all P CONCLUSIONS In this cohort of nondegenerative and nondeformity spine patients, the greatest amount of regional changes occur for cervical lordosis, C2–T3 angle, TK, SVA, and PI-LL as patients transition from standing to sitting position in order to maintain global spinal alignment, with C4–C5 and C5–C6 having the greatest mobility.