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

Introduction: Radiographic 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 question: To determine the most clinically and functionally relevant global alignment parameters in ASD. Material and methods: ASD 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. Results: 124 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 conclusion: Among 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.

Assessing the predictive power of the GAP score on mechanical complications: a comprehensive systematic review and meta-analysis.

PURPOSE: The prevention of mechanical complications (MC) is a major concern in adult spinal deformity (ASD) correction surgery; thus, the global alignment and proportion (GAP) score was developed to assess MC risk. Numerous studies have clarified the validity of the GAP score, but their contradictory results have prevented researchers from reaching compelling conclusions. This study aimed to analyze the predictive power of the GAP score on MC via a meta-analysis. METHODS: A total of 1,617 patients were included in the meta-analysis. Studies relevant to the GAP score and MC were identified in PubMed, EMBASE, and Cochrane CENTRAL and screened according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The GAP score categories of the patients and their MC/revision surgery status were collected. The data collected for the meta-analysis of odds ratios (OR) included the number of patients in the GAP score subgroups and their MC/revision surgery status. To calculate the OR, three GAP score subgroups were combined into two groups; hence, the analysis was conducted twice (gap proportioned [GAP-P] and higher groups, and gap severely disproportioned [GAP-SD] and lower groups). RESULTS: Eleven studies were collected; of them, revision surgery data were available for seven. The proportion of MC in the studies was 27.7-60.6%, while that of revision surgery was 11.7-34.9%. In the meta-analysis of the GAP-P and higher score groups, the difference in MC ratio was significant (OR = 2.83; 95% confidence interval [CI] = 1.20-6.67; P = 0.02), whereas that for revision surgery was not. For the GAP-SD and lower score groups, the GAP-SD group had significantly higher proportions of both MC (OR = 2.65; 95% CI = 1.57-4.45; P < 0.001) and revision surgery (OR = 2.27; 95% CI = 1.33-3.88; P = 0.003). Publication bias was significant only in the latter MC analysis. CONCLUSION: The GAP score offers predictive value for the risk of mechanical complications.

Sagittal alignment of diverse mechanical complications following adult spinal deformity surgery.

PURPOSE: To compare the sagittal alignment of patients with diverse mechanical complications (MCs) following adult spinal deformity (ASD) surgery with that of patients without MCs. METHODS: A total of 371 patients who underwent ASD surgery were enrolled. The sagittal spinopelvic parameters were measured preoperatively and at the 6-month and last follow-up, and the global alignment and proportion (GAP) score was calculated. The subjects were divided into non-MC and MCs groups, and the MCs group was further divided into rod fracture (RF), screw breakage (SB), screw dislodgement (SD) and proximal junctional kyphosis (PJK) subgroups. RESULTS: Preoperatively, the RF group had greater thoracolumbar kyphosis (TLK) and relative upper lumbar lordosis (RULL); the SB group had the largest pelvic incidence (PI) and lumbar lordosis (LL); the SD group had the least global sagittal imbalance; and the PJK group had the highest thoracic kyphosis (TK), TLK and RULL. At the last follow-up, the RF and SB groups featured a large PI minus LL (PI-LL), while the PJK group featured a prominent TK; all the MCs subgroups had sagittal malalignment and a higher GAP score, and the SB group had the most severe cases. Logistic regressions showed that the relative spinopelvic alignment (RSA) score was correlated with RF, SB and SD, while the RSA and age scores were associated with PJK. CONCLUSION: Each patient with MCs had individual characteristics in the sagittal plane following ASD surgery, which may be helpful to understand the pathophysiology of poor sagittal alignment with its subsequent MCs and guide an eventual revision strategy.

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.

Clinical significance of relative pelvic version measurement as a predictor of low back pain after total hip arthroplasty.

PURPOSE: To evaluate the association between the preoperative global alignment and proportion (GAP) score and low back pain (LBP) after total hip arthroplasty (THA). METHODS: This was a retrospective case-control study of 200 patients who underwent primary unilateral THA for hip osteoarthritis. The following variables were compared between individuals with (n = 76) and without (n = 124) LBP after THA over a mean follow-up of 2 years: age, sex, GAP score, and patient-reported outcome measures. Logistic regression and receiver operating characteristic curve analyses were used to detect predictive factors. RESULTS: The following parameters were predictive of post-THA LBP: relative pelvic version (RPV) <-7° (odds ratio, 1.43; 95% confidence interval, 1.10-1.72; P = 0.032) and relative lumbar lordosis <-15° (odds ratio, 1.13; 95% confidence interval, 1.04-2.13; P = 0.041) preoperatively. Using an RPV cutoff value of - 7° (specificity 61/64 = 0.953; sensitivity 121/136 = 0.890), there were significant between-group differences in LBP visual analog scale (P = 0.020), Oswestry Disability Index (ODI, P = 0.014), EuroQol 5-Dimension (P = 0.027), Hip Disability and Osteoarthritis Outcome Score Joint Replacement (HOOS JR, P = 0.012), patient satisfaction (P = 0.024). There was clinically meaningful improvement for LBP visual analog scale (P = 0.001), ODI (P = 0.004), and HOOS JR (P < 0.001). The RPV before THA was correlated with HOOS JR (r = 0.773, P = 0.012) and ODI (r = - 0.602, P = 0.032) postoperatively. CONCLUSION: Among the GAP score, a moderate-to-severe pelvic retroversion was significantly associated with LBP post-THA. The RPV measurement may be a useful predictor of THA outcome, which may influence patient satisfaction.

External Validation of the Global Alignment and Proportion Score as Prognostic Tool for Corrective Surgery in Adult Spinal Deformity: A Systematic Review and Meta-Analysis.

BACKGROUND: Since its proposal, the Global Alignment and Proportion (GAP) score has been the topic of several external validation studies, which have yielded conflicting results. Given the lack of consensus regarding this prognostic tool, the authors aim to assess the accuracy of GAP scores for predicting mechanical complications following adult spinal deformity correction surgery. METHODS: A systematic search was performed using PubMed, Embase, and Cochrane Library for the purpose of identifying all studies evaluating the GAP score as a predictive tool for mechanical complications. GAP scores were pooled using a random-effects model to compare patients reporting mechanical complications after surgery versus those reporting no complications. Where receiver operator curves were provided, the area under the curve (AUC) was pooled. RESULTS: A total of 15 studies featuring 2092 patients were selected for inclusion. Qualitative analysis using Newcastle-Ottawa criteria revealed moderate quality among all included studies (5.99/9). With respect to sex, the cohort was predominantly female (82%). The pooled mean age among all patients in the cohort was 58.55 years, with a mean follow-up of 33.86 months after surgery. Upon pooled analysis, we found that mechanical complications were associated with higher mean GAP scores, albeit minimal (mean difference = 0.571 [ 95% confidence interval: 0.163-0.979]; P = 0.006, n = 864). Additionally, age (P = 0.136, n = 202), fusion levels (P = 0.207, n = 358), and body mass index (P = 0.616, n = 350) were unassociated with mechanical complications. Pooled AUC revealed poor discrimination overall (AUC = 0.69; n = 1206). CONCLUSIONS: GAP scores may have a minimal-to-moderate predictive capability for mechanical complications associated with adult spinal deformity correction.

Relationship between pelvic incidence-adjusted relative spinopelvic parameters, global sagittal alignment and lower extremity compensations.

PURPOSE: In response to sagittal malalignment, compensatory spinal and lower extremity mechanisms are recruited. Thoracolumbar realignment surgery has been shown to yield reciprocal changes in these compensations. Thus, whole-body radiographic assessment has come to the fore. This study aimed to evaluate the relationship between spinopelvic parameters and lower extremity compensation angles and to examine their coupled change with deformity correction. METHODS: This was a multicenter retrospective analysis of patients who had ≥ 4 levels posterior fusion, whole-body radiographs, and ≥ 2 years follow-up. Relative Pelvic Version (RPV), Relative Lumbar Lordosis (RLL), Relative Spinopelvic Alignment (RSA), Femoral Obliquity Angle (FOA), Knee Flexion Angle (KFA) and Global Sagittal Axis (GSA) were measured preoperatively and 6 week postoperatively. Kruskal-Wallis tests were performed to assess the relation of relative spinopelvic parameters to global sagittal alignment and lower extremity compensation angles. Spearman's correlations were performed to assess correlations of pre-to-postoperative changes. RESULTS: 193 patients (156F, 37 M) were included. The mean age was 57.2 ± 16.6 years. The mean follow-up duration was 50.6 (24-90) months. On average, 10.3 ± 3.8 levels were fused. Among the cohort, 124 (64.2%) had a sacral or sacroiliac fixation, and 43 (22.3%) had 3-column osteotomies. Preoperative FOA, KFA and GSA significantly differed between RPV, RLL and RSA categories. Significant weak-to-strong correlations were observed between spinopelvic parameters, global sagittal alignment and lower extremity compensation angles (rho range: - 0.351 to 0.767). CONCLUSIONS: PI-adjusted relative spinopelvic parameters significantly correlated with measurements of the lower extremity compensation. Postoperative changes in RPV, RLL and RSA reflected changes in FOA, KFA and GSA. These measurements may serve as a valuable proxy for surgical planning when whole-body imaging is not available.

A Physical Model to Describe the Motion Behavior of BNNSs under Nanosecond Pulses.

This paper presents a physical model that provides a comprehensive understanding of the motion behavior of boron nitride nanosheets (BNNSs) immersed in ultrapure deionized water and subjected to a series of nanosecond pulses. In a study conducted by Y. Mi et al. The authors explored the global alignment behavior of BNNSs and fitted the experimental data with an exponential decay function. However, this function lacks clear physical mechanisms and the significance of the fitting parameters remains unclear. To address this issue, we have developed a kinetic model that explicitly describes the underlying physical mechanisms. Furthermore, we propose a simplified mathematical model that not only predicts the displacement of BNNSs but also estimates the total time, velocity, and acceleration of the motion process.

Mechanical complications and reoperations after adult spinal deformity surgery: a clinical analysis with the GAP score.

PURPOSE: Adult spinal deformity (ASD) surgery is prone to postoperative complications, leading to high reoperation rates. The global alignment and proportion (GAP) score is a novel method to predict mechanical complications (MC) based on the optimal parameters related to individual pelvic incidence. The aim of this study was to determine the cut-off point and the predictive value of the GAP score for those MCs that require reoperation. A secondary aim was to investigate the cumulative incidence of MCs requiring reoperation during a long follow-up period. METHODS: In total, 144 ASD patients were operated at our institution due to marked symptomatic spinal deformity between 2008 and 2020. The cut-off point and the predictive value of the GAP score for the MCs that required reoperation and the cumulative incidence of reoperated MCs after index surgery were determined. RESULTS: A total of 142 patients were included in the analysis. The risk for having an MC that required reoperation was significantly lower when the postoperative GAP score was < 5 (HR = 3.55, 95% CI: 1.40-9.02). The discriminative power of the GAP score to predict MCs that require reoperation was good with an AUC of 0.70 (95% CI: 0.58-0.81). The cumulative incidence of reoperated MCs was 18%. CONCLUSION: The GAP score was associated with the risk for MCs that require reoperation. The best predictive value for surgically treated MC was with the GAP score [Formula: see text] 5. The cumulative incidence of the reoperated MCs was 18%.

T1 pelvic angle is associated with rapid progression of hip arthrosis.

PURPOSE: To evaluate the association between global spinal malalignment and rapid progression of hip arthrosis. METHODS: This was a retrospective, case-control study including 90 patients, contributing 90 hips, who underwent hemi- or total hip arthroplasty at our institution. For analysis, hips were classified into a rapid progression group, defined as ≥ 2 mm destruction of the femoral head or loss of the hip joint space within a 12-month period (n = 30), and a non-rapid progression group, defined by no observable hip disease progression over a period more than 12 months (n = 60). Logistic regression analysis identified factors that predicted rapid progression, with a receiver operating characteristic curve analysis used to confirm factors. RESULTS: Significant between-group differences were identified for the following parameters: pelvic tilt (P = 0.002, PT), sagittal vertical axis (P = 0.002, SVA), and T1 pelvic angle (P < 0.001, TPA). On multiple logistic regression, PT (P = 0.002), SVA (P = 0.002), and TPA (P < 0.001) were predictive of a rapid progression on hip arthrosis, with the area under the curve being greater for TPA than PT (P = 0.035). CONCLUSION: Global spinal alignment is associated with rapid progression of hip arthrosis. TPA could assist in identifying patients at risk for rapid progression of hip arthrosis, allowing for time management.

Use of the Global Alignment and Proportion score to predict postoperative health-related quality of life in adult spinal deformity surgery.

OBJECTIVE: The purpose of this study was to validate the Global Alignment and Proportion (GAP) score as a predictor of health-related quality of life (HRQOL) outcomes for patients undergoing adult spinal deformity (ASD) surgery. METHODS: This was a retrospective cohort study of patients with ASD undergoing long-segment spine fusions (≥ 5 vertebrae fused) at a single institution over a 2-year period (n = 85). Radiographic parameters were measured at preoperative, 6-week postoperative, 1-year postoperative, and 2-year postoperative visits. GAP scores were calculated using 4 sagittal parameters: relative pelvic version, relative lumbar lordosis, lordosis distribution index, and relative spinopelvic alignment. Patients were stratified into 3 GAP categories at each time point: proportioned (score 0-2), moderately disproportioned (score 3-6), and severely disproportioned (score ≥ 7). HRQOL outcomes were collected at preoperative, 1-year postoperative, and 2-year postoperative visits; these measures included patient self-reported outcome measures (i.e., PROMIS), Scoliosis Research Society-22 spinal deformity questionnaire (SRS-22), and Oswestry Disability Index (ODI) scores. RESULTS: Overall, 42% of cases were revision surgeries and 96.5% of patients underwent fusion to the sacrum. The mean preoperative GAP score significantly improved from preoperative (7.84) to immediate postoperative (3.31) assessment (p < 0.001). Similarly, the percentage of patients categorized as proportioned improved from 9.4% at preoperative to 45.9% at immediate postoperative evaluation. The preoperative GAP score or category was not significantly associated with any preoperative HRQOL outcome metrics. The immediate postoperative GAP score was not correlated with any 1-year HRQOL outcomes. However, the immediate postoperative GAP score was significantly associated with 2-year SRS-22 outcomes, including SRS-22 function (r = -0.35, p < 0.01), self-image (r = -0.27, p = 0.044), and subtotal (r = -0.35, p < 0.01) scores. As compared to severely disproportioned patients, proportioned patients had better SRS-22 pain (4.08 vs 3.17, p = 0.04), satisfaction (4.40 vs 3.50, p = 0.02), and subtotal (4.01 vs 3.27, p = 0.036) scores. The immediate postoperative GAP score was also significantly associated with 2-year PROMIS outcomes, including PROMIS pain (r = 0.31, p = 0.023) and physical function (r = -0.35, p < 0.01) scores. As compared to severely disproportioned patients, proportioned patients had better PROMIS pain (53.18 vs 63.60, p = 0.025) and physical function (41.66 vs 34.18, p = 0.017) scores. Postoperative GAP score or category did not predict any ODI outcomes. CONCLUSIONS: The postoperative GAP score is a predictor of long-term HRQOL outcomes following ASD surgery, and proportioned patients are more likely to have less pain and be satisfied with their surgery. However, the postoperative GAP score does not predict outcomes as measured by ODI.

Analysis of Mechanical Failure Using the GAP Score After Surgery With Lateral and Posterior Fusion for Adult Spinal Deformity.

STUDY DESIGN: A retrospective observational study. OBJECTIVE: The purpose of this study was to evaluate the Global Alignment and Proportion (GAP) score and mechanical failure (MF) following corrective fusion surgery with planned 2-stage surgery using lateral lumbar interbody fusion in patients with adult spinal deformity (ASD). METHODS: Fifty-four patients (2 men, 52 females, aged 70.3 years) were included. MF, proximal junctional failure (PJF), and rod breakage (RB) occurred in 46.3% (25/54), 22.2% (12/54), and 29.6% (16/54) of patients, respectively. The immediate postoperative GAP scores were compared between patients with MF and without MF (MF+ and MF-, respectively). GAP scores in groups with and without PJF or RB were also compared. RESULTS: Patients were grouped according to the GAP score for spinopelvic alignment: 23 (42.6%) as proportioned, 22 (40.7%) as moderately disproportioned, and 9 (16.7%) as severely disproportioned. The pre- and postoperative spinopelvic parameters did not differ significantly between the MF- and MF+ groups except pelvic incidence. Postoperatively, the mean pelvic incidence-lumbar lordosis changed to <10° in both groups. The GAP score and 3 categories of GAP scores did not differ significantly between the PJF- and PJF+ groups or between the RB+ and RB- groups. CONCLUSION: Multiple factors can cause PJF and RB, and the patient's background may affect the ability to use the GAP score to predict MF. Further research may be needed in the future using modified GAP scores with additional factors in ASD patients.

An Analysis of Whether a New Formula Can Predict Proximal Junctional Failure in Adult Spinal Deformity Patients with Global Kyphosis.

OBJECTIVE: A new formula containing terms for age and sagittal curvature reported by the International Spine Study Group is ideal lumbar lordosis (iLL) = pelvic incidence - 0.3 thoracic kyphosis - 0.5Age + 10. However, there are no reports of whether proximal junctional failure (PJF) can be predicted using this formula. We assessed the utility of this formula in PJF in patients with adult spinal deformity with global kyphosis using the Roussouly classification. METHODS: Forty-four patients with adult spinal deformity global kyphosis (mean age 70.0 years) who underwent multiple levels of lateral lumbar interbody fusion combined with posterior instrumentation were included. Patients were divided into 2 groups: PJF and non-PJF. Demographic, surgical, and radiological parameters were compared. The iLL was calculated according to the new formula, and spinal parameters were compared preoperatively, immediately after, and at the final follow-up. RESULTS: PJF occurred in 11 of 44 (25.0%) patients. Patients with PJF had a large preoperative and postoperative TK, but there was no statistically significant difference in iLL between PJF and non-PJF patients (33.4° vs. 30.2°, P = 0.357). In addition, there was no statistically significant difference in LL and iLL changes (ΔiLL) immediately after surgery (19.0° vs. 23.4°, P = 0.379). Furthermore, there was no correlation between ΔiLL immediately after surgery and at the final follow-up and the proximal junctional angle at the final follow-up. CONCLUSIONS: The results of ΔiLL suggest that overcorrection needs to be addressed but that this new formula, including age adjustment, may not predict PJF.

Challenges and Limitations of Biological Network Analysis.

High-Throughput technologies are producing an increasing volume of data that needs large amounts of data storage, effective data models and efficient, possibly parallel analysis algorithms. Pathway and interactomics data are represented as graphs and add a new dimension of analysis, allowing, among other features, graph-based comparison of organisms' properties. For instance, in biological pathway representation, the nodes can represent proteins, RNA and fat molecules, while the edges represent the interaction between molecules. Otherwise, biological networks such as Protein-Protein Interaction (PPI) Networks, represent the biochemical interactions among proteins by using nodes that model the proteins from a given organism, and edges that model the protein-protein interactions, whereas pathway networks enable the representation of biochemical-reaction cascades that happen within the cells or tissues. In this paper, we discuss the main models for standard representation of pathways and PPI networks, the data models for the representation and exchange of pathway and protein interaction data, the main databases in which they are stored and the alignment algorithms for the comparison of pathways and PPI networks of different organisms. Finally, we discuss the challenges and the limitations of pathways and PPI network representation and analysis. We have identified that network alignment presents a lot of open problems worthy of further investigation, especially concerning pathway alignment.

Reciprocal Changes in the Whole-Body Following Realignment Surgery in Adult Spinal Deformity.

The idea of the global balance of spine stems from Jean Dubousset, who first introduced the concept of cone of economy. Through the compensatory mechanisms, the human body maintains an upright posture and horizontal gaze in the setting of the spinal malalignment. Compensation takes place not only in the mobile spine segments, but also in the pelvis and lower extremities. Patients with a malalignment exhibit compensatory changes in the cervical hyper-lordosis, posterior pelvic shift, knee/ankle flexion, hip extension, and the pelvic retroversion. The advent of whole-body stereo radiography has yielded an improved understanding of global changes among the patients. Deformity-induced compensatory changes in the sagittal alignment could be resolved reciprocally after the surgical correction of the malalignment. Thoracolumbar realignment surgery restores the pathologic compensatory changes in the unfused spinal segments, pelvis, and the lower extremities. Similarly, reciprocal changes in the thoracolumbar spine may harmonize global sagittal alignment after the cervical reconstruction. This study reviews the compensatory mechanisms and reciprocal changes in global sagittal alignment caused by the surgical correction and highlights, the factors that should be considered while assessing a patient's compensatory status.

Relationship Between Hounsfield Units of Upper Instrumented Vertebrae, Proximal Junctional Failure, and Global Alignment and Proportion Score in Female Patients with Adult Spinal Deformity.

STUDY DESIGN: This was a retrospective observational study. OBJECTIVES: The purpose of this study was to evaluate bone mineral density using Hounsfield unit (HU) values at the upper instrumented vertebrae (UIV), UIV+1, and UIV+2 and to investigate the association with proximal junctional failure (PJF) in female patients with adult spinal deformity (ASD). We also evaluated the relationship between the global alignment and proportion (GAP) score and the HU value of patients after ASD surgery. METHODS: Fifty-two patients (52 females, mean age =70.2 years) who underwent multiple-level lateral lumbar interbody fusion combined with posterior instrumentation for ASD were included. The patients were divided into 2 groups, PJF and non-PJF. The demographics, surgical characteristics, and radiographic parameters were compared. Vertebral HU values at UIV, UIV+1, and UIV+2 using preoperative computed tomography scans and immediate postoperative GAP scores were also compared. RESULTS: PJF was found in 13 of 52 patients (25.0%). Preoperative and postoperative thoracic kyphosis was large in PJF patients. Based on the total GAP score, there was no significant difference among the categories of GAP scores (P = 0.514). The statistically significant difference in mean HU values (116.6 ± 28.1 vs. 141.8 ± 41.8, P = 0.049) between the two groups at UIV. Further correlation analysis showed that the mean HU values in UIV and UIV+1 showed a significantly negative correlation coefficient with the total GAP score. CONCLUSIONS: Our study suggests that preoperative HU values at UIV may affect the development of PJF for female ASD patients. HU evaluation by preoperative computed tomography may help reduce the incidence of PJF.

The impact of lumbar alignment targets on mechanical complications after adult lumbar scoliosis surgery.

PURPOSE: The purpose of this study was to determine the discriminatory ability of age-adjusted alignment offset and the global alignment and proportion (GAP) score parameters to predict postoperative mechanical complications. METHODS: Surgical patients from the Adult Symptomatic Lumbar Scoliosis cohort were reviewed at 2 year follow up. Age-adjusted alignment offsets and GAP parameters were calculated for each patient. A series of nonlinear logistic regression models were fit, and the odds of mechanical complications were calculated. The discriminatory ability of the GAP score, GAP score parameters, and age-adjusted alignment offsets were determined plotting receiver operative characteristic (ROC) with the C statistic (AUC). RESULTS: A total of 165 patients were included. A total of 49 mechanical complications occurred in 41 patients (21 proximal junctional kyphosis and 28 pseudoarthrosis). The GAP score had no discriminatory ability in this cohort. Relative lumbar lordosis 15 degrees greater than ideal lumbar lordosis was associated with greater mechanical complications. A lumbar distribution index of 90% was associated with fewer mechanical complications compared to a lumbar distribution index of 65%. Age-adjusted offset alignment targets had no discriminatory ability to predict mechanical complications. CONCLUSION: Radiographic alignment targets using either age-adjusted alignment target offset or GAP score parameters had minimal ability to predict mechanical complications in isolation. Mechanical complications following adult spinal deformity surgery are complex, and patient factors play a critical role. Clinical trial registeration This study was registered at ClinicalTrials.gov (number NCT00854828) in March 2009.

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.

Low-Cost Algorithms for Metabolic Pathway Pairwise Comparison.

Metabolic pathways provide key information for achieving a better understanding of life and all its processes; this is useful information for the improvement of medicine, agronomy, pharmacy, and other similar areas. The main analysis tool used to study these pathways is based on pathway comparison, using graph data structures. Metabolic pathway comparison has been defined as a computationally complex task. In a previous work, two new algorithms were introduced to treat the problem of metabolic pathway pairwise comparison. Here we provide an extended analysis with more data and a deeper analysis of metabolic pathway comparison as listed in the discussion and results section.

Reciprocal Changes Following Cervical Realignment Surgery.

Over the last few decades, the importance of the sagittal plane and its contour has gained significant recognition. Through full-body stereoradiography, the understanding of compensatory mechanisms, and the concept of global balance and reciprocal change has expanded. There have been a few reports describing how cervical realignment surgery affects global spinal alignment (GSA) and global balance. Despite the research efforts, the concept of reciprocal change and global balance is still perplexing. Understanding the compensatory status and main drivers of deformity in a patient is vital because the compensatory mechanisms may resolve reciprocally following cervical realignment surgery. A meticulous preoperative evaluation of the whole-body alignment, including the pelvis and lower extremities, is paramount to appreciate optimal GSA in the correction of spinal malalignment. This study aims to summarize relevant literature on the reciprocal changes in the whole body caused by cervical realignment surgery and review recent perspectives regarding cervical compensatory mechanisms.