Global Alignment And Proportion Scores Research Articles

Characteristics of Spinal Morphology According to the Global Alignment and Proportion (GAP) Score in a Diverse, Asymptomatic Cohort: Multi-Ethnic Alignment Normative Study.

Multi-Ethnic Alignment Normative Study (MEANS) cohort: prospective, cross-sectional, multicenter. To analyze the distribution of GAP scores in the MEANS cohort and compare the spinal shape via stratification by GAP alignment category, age, and country. The GAP score has been used to categorize spinal morphology and prognosticate adult spinal deformity surgical outcomes and mechanical complications. We analyzed a large, multiethnic, asymptomatic cohort to assess the distribution of GAP scores. Four hundred sixty-seven healthy volunteers without spinal disorders were recruited in five countries. Sagittal radiographic parameters were measured via the EOS imaging system. The GAP total and constituent factor scores were calculated for each patient. Kruskal-Wallis rank sum test was performed to compare variables across groups, followed by the post hoc Games-Howell test. Fisher exact test was used to compare categorical variables. The significance level was set to P <0.05. In the MEANS cohort, 13.7% (64/467) of volunteers were ≥60 years old, and 86.3% (403/467) were <60 years old. 76.9% (359/467) was proportioned, 19.5% (91/467) was moderately disproportioned, and 3.6% (17/467) was severely disproportioned. There was no significant difference in the frequency of proportioned, moderately, or severely disproportioned GAP between subjects from different countries ( P =0.060). Those with severely disproportioned GAP alignment were on average 14.5 years older ( P =0.016), had 23.1° lower magnitude lumbar lordosis (LL) ( P <0.001), 14.2° higher pelvic tilt ( P <0.001), 13.3° lower sacral slope ( P <0.001), and 24.1° higher pelvic-incidence (PI)-LL mismatch ( P <0.001), 18.2° higher global tilt ( P <0.001) than those with proportioned GAP; thoracic kyphosis and PI were not significantly different ( P >0.05). The GAP system applies to a large, multiethnic, asymptomatic cohort. Spinal alignment should be considered on a spectrum, as 19.5% of the asymptomatic volunteers were classified as moderately disproportioned and 3.6% severely disproportioned. Radiographic malalignment does not always indicate symptoms or pathology. 3.

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

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. 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. 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 58.55years, with a mean follow-up of 33.86months 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). GAP scores may have a minimal-to-moderate predictive capability for mechanical complications associated with adult spinal deformity correction.

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

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. 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. 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. 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.

Does the Global Alignment and Proportion score predict mechanical complications in circumferential minimally invasive surgery for adult spinal deformity?

The Global Alignment and Proportion (GAP) score was developed to serve as a tool to predict mechanical complication probability in patients undergoing surgery for adult spinal deformity (ASD), serving as an aid for setting surgical goals to decrease the prevalence of mechanical complications in ASD surgery. However, it was developed using ASD patients for whom open surgical techniques were used for correction. Therefore, the purpose of this study was to assess the applicability of the score for patients undergoing circumferential minimally invasive surgery (cMIS) for correction of ASD. Study participants were patients undergoing cMIS ASD surgery without the use of osteotomies with a minimum of four levels fused and 2 years of follow-up. Postoperative GAP scores were calculated for all patients, and the association with mechanical failure was analyzed. The authors identified 182 patients who underwent cMIS correction of ASD. Mechanical complications were found in 11.1% of patients with proportioned spinopelvic states, 20.5% of patients with moderately disproportioned spinopelvic states, and 18.8% of patients with severely disproportioned spinopelvic states. Analysis with a chi-square test showed a significant difference between the cMIS and original GAP study cohorts in the moderately disproportioned and severely disproportioned spinopelvic states, but not in the proportioned spinopelvic states. For patients stratified into proportioned, moderately disproportioned, and severely disproportioned spinopelvic states, the GAP score predicted 6%, 47%, and 95% mechanical complication rates, respectively. The mechanical complication rate in patients undergoing cMIS ASD correction did not correlate with the calculated GAP spinopelvic state.

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

This was a retrospective observational study. 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. Fifty-two patients (52 females, mean age=70.2years) 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. 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 groupsat 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. 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.

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

BACKGROUNDThe 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. PURPOSETo 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 DESIGNA prospective cross-sectional radiographic study. PATIENTS SAMPLEOf 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 MEASURESThe 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. METHODSSubjects 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. RESULTSThe 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. CONCLUSIONSThe 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.

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

A retrospective observational study. 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). Fifty-four patients (2 men, 52 females, aged 70.3years) 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. 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. 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.

Does change in focal lordosis after spinal fusion affect clinical outcomes in degenerative spondylolisthesis?

ABSTRACTStudy Design:Retrospective cohort study.Objective:The objective of this study is to determine the effect of focal lordosis and global alignment and proportion (GAP) scores on patient reported outcome measures (PROMs) after posterior lumbar fusion for patients with 1- or 2-level lumbar degenerative spondylolisthesis (DS).Summary of Background Data:In patients with DS, improvements in spinopelvic parameters are believed to improve clinical outcomes. However, the effect of changing focal lordosis in patients with 1-or 2-level degenerative lumbar spondylolisthesis is unclear.Materials and Methods:Postoperative spinopelvic parameters and perioperative focal lordosis changes were measured for 162 patients at a single academic center from January 2013 to December 2017. Patients were divided into three groups: >2° (lordotic group), between 2° and −2° (neutral group), and −2°° (kyphotic group). Patients were then reclassified based on GAP scores. Recovery ratios (RR) and the number of patients achieving the minimal clinically important difference (MCID) were calculated for PROMs. Standard descriptive statistics were reported for patient demographics and outcomes data. Multiple linear regression analysis controlled for confounders. Alpha was set at P < 0.05.Results:There was no significant association between change in focal lordosis and surgical complications including adjacent segment disease (P = 0.282), instrumentation failure (P = 0.196), pseudarthrosis (P = 0.623), or revision surgery (P = 0.424). In addition, the only PROM affected by change in focal lordosis was Mental Component Scores (ΔMCS-12) (lordotic = 2.5, neutral = 8.54, and kyphotic = 5.96, P = 0.017) and RR for MCS-12 (lordotic = 0.02, neutral = 0.14, kyphotic 0.10, P = 0.008). Linear regression analysis demonstrated focal lordosis was a predictor of decreased improvement in MCS-12 (β = −6.45 [−11.03- −1.83], P = 0.007). GAP scores suggested patients who were correctly proportioned had worse MCID compared to moderately disproportioned and severely disproportioned patients (P = 0.024).Conclusions:The change in focal lordosis not a significant predictor of change in PROMs for disability, pain, or physical function. Proportioned patients based on the GAP score had worse MCID for Oswestry Disability Index.Level of Evidence:III

P87. Global alignment and proportion (GAP) score with modified RSA parameter: GAP-R score

P87. Global alignment and proportion (GAP) score with modified RSA parameter: GAP-R score

Evaluation of global alignment and proportion score in an independent database

Background ContextSagittal spinopelvic alignment has been associated with patient-reported outcome measures and mechanical complication rates. Recently, it was claimed that linear numerical values of pelvic tilt and lumbar lordosis measurements may be misleading for patients that have different magnitudes of pelvic incidence. The use of “relative” measurements embedded in a weighted scoring of Global Alignment and Proportion (GAP) was proposed. PurposeThe purpose was to evaluate the GAP scorein an independent database. Study Design/SettingRetrospective Cohort Study Patient SampleAdult spinal deformity patients who underwent ≥7 levels posterior fusion to the pelvis between 2004 and 2014 were included. Outcome MeasuresMechanical Complication Rates. MethodsDemographic, clinical, surgical and radiographic patient characteristics were recorded. Cochran-Armitage tests were used to compare mechanical complication rates in GAP categories. Uni and multivariable logistic regression analyses were used to obtain crude and adjusted Odds Ratios, of predictor (GAP categories) and the outcome (mechanical complication), and Risk Ratios were calculated. The diagnostic performance of the GAP score was tested using the area under the receiver operating characteristic curve, sensitivity, specificity, positive predictive value, negative predictive value and accuracy in predicting mechanical complications. ResultsA total of 322 patients (285F, 37M) with a mean age of 58.2±9.6 were analyzed. Mean follow-up was 69.7 months (range 24 to 177). Mechanical complications occurred in 52.2% of the patients. Mechanical complication rates in proportioned (GAP-P), moderately (GAP-MD) and severely disproportioned (GAP-SD) patients were 21.8%, 55.1%, and 70.4%, respectively. AUC for the GAP score, at 2 years, was 0.682 (95% CI, 0.624 to 0.741, p<.001). AUC at minimum 5 years follow-up was similar at 0.708, while AUC at minimum 7- and 12-year follow-up were 78.5 and 90.7, respectively. Having a postoperative spinopelvic alignment of GAP-MD and GAP-SD resulted in 2.5 and 3.2 folds of relative risk in incurring a mechanical complication when compared to having a proportioned spinopelvic state, respectively. ConclusionsThis study reports an association between the GAP Score and mechanical complications in an independent database. Increased association was noted as the years of follow-up increased. Aiming to achieve proportionate GAP Score postoperatively seems to be a viable option as lower GAP scores were associated with lower rates of mechanical complications, and vice versa.

Optimal Reconstruction of Sagittal Alignment According to Global Alignment And Proportion Score Can Reduce Adjacent Segment Degeneration After Lumbar Fusion.

A retrospective study. The aim of this study was to investigate the ability of Global Alignment and Proportion (GAP) score to predict the occurrence of adjacent segment degeneration (ASD) after fusion surgery for lumbar degenerative diseases. The recently developed GAP score was applied to predict postoperative complications for adult spinal deformity, as well as to facilitate future outcome-based research on optimal treatment for various spinal conditions. However, it remains unclear whether reconstruction of alignment according to GAP score can reduce the ASD rates. This study retrospectively reviewed 126 consecutive patients who had undergone lumbar fusion and had been followed over 2 years. Pre- and postoperative radiographs and MRI were analyzed for ASD. GAP scores were calculated based on the early postoperative spinopelvic parameters. Cochran-Armitage test of trend was performed to investigate the association between GAP score and the occurrence of ASD. Receiver-operating characteristic curves were used to analyze the predictive accuracy of the GAP score for ASD. Radiographical ASD (R-ASD) and symptomatic ASD (S-ASD) were diagnosed in 44 (34.9%) patients and in 13 (10.3%) patients, respectively. The patients with a proportioned spinopelvic state according to the GAP score had significantly lower rates of ASD (R-ASD and S-ASD) or S-ASD than those with a moderately or severely disproportioned spinopelvic state. The area under curve for the GAP score predicting ASD and S-ASD was 0.691 (95% confidence interval [CI]: 0.596∼0.785, P < 0.01) and 0.865 (95% CI: 0.771∼0.958, P < 0.01), respectively. Our study revealed a significant association between postoperative GAP score and occurrence of ASD after lumbar fusion surgery. Setting surgical goals according to the GAP score may help reduce the occurrence of ASD, especially for S-ASD.Level of Evidence: 4.

129. GAP score with modified relative pelvic version (RPV) parameter: GAP-V score

BACKGROUND CONTEXT The global alignment and proportion (GAP) score was thus developed to predict such mechanical complications following spinal correction surgery. The GAP score is a pelvic-incidence based method of analyzing the sagittal plane. GAP scores of 0∼2 are classified as proportioned, 3∼6 as moderately proportioned, and >=7 as severely disproportioned. GAP parameters include relative pelvic version (RPV), relative lumbar lordosis, lordosis distribution index, age factor of 60, and relative spinopelvic alignment. RPV categories include: 5° receiving a score of 1. PURPOSE The aim of the study was to adjust the RPV parameter in calculation of GAP scores among US adult volunteers with no prior spinal pathology, in order to compensate for high GAP scores in otherwise healthy individuals. STUDY DESIGN/SETTING Retrospective review of prospectively collected data. PATIENT SAMPLE This study included 87 healthy volunteers were included in the study. Mean age was 54.9±15.1 (20-84) years. Exclusion criteria included any major spinal pathology or surgery, terminal illness, morbid obesity, or any significant comorbid condition. OUTCOME MEASURES GAP scores with RPV parameter removed and GAP-V scores. METHODS Preliminary GAP scores with the RPV parameter removed were assessed in 87 healthy volunteers that met inclusion criteria. The preliminary GAP scores were grouped based on the original GAP system's RPV parameters, and these scores were analyzed to search for discrepancies from the baseline trend. Original GAP scores were calculated for the same 87 healthy volunteers. GAP-V scores were calculated with the same parameters as the GAP score, with the exception of the RPV factor. In GAP-V scores, the number of points were subtracted from each RPV group in the same amount that showed discrepancies in the preliminary GAP score trend. The percentages of Proportioned, Moderately Disproportioned, and Severely Disproportioned volunteers were then compared between the two scoring systems. RESULTS Preliminary GAP scores show a 1-point and 5-point discrepancy point in the -15°∼ -7.1° and CONCLUSIONS Our study examined the RPV parameter in calculation of GAP scores in a healthy US population. In this study, we analyzed how the GAP score system may be attributing a high score to otherwise healthy individuals. We found the percentage of proportioned volunteers increases in the original GAP score by subtractions at RPV groups -15°∼ -7.1° and FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

P93. The global alignment and proportion (GAP) score needs a modified LDI parameter: creating the GAP-D score

BACKGROUND CONTEXT Proximal Junctional Kyphosis has been a well-known complication following adult spinal deformity correction surgery. The Global Alignment and Proportion (GAP) score was thus developed to predict such mechanical complications following spinal correction surgery. The GAP score is a pelvic-incidence based method of analyzing the sagittal plane. GAP scores of 0∼2 are classified as proportioned, 3∼6 as moderately proportioned, and >=7 as severely disproportioned. GAP parameters include relative pelvic version, relative lumbar lordosis, lordosis distribution index (LDI), age factor of 60, and relative spinopelvic alignment. LDI categories include: 80% receiving a score of 3. PURPOSE The aim of the study was to adjust the LDI parameter in calculation of GAP scores among US adult volunteers with no prior spinal pathology, in order to compensate for high GAP scores in otherwise healthy individuals. STUDY DESIGN/SETTING Retrospective review of prospectively collected data. PATIENT SAMPLE A total of 87 healthy volunteers were included in the study. Mean age was 54.9±15.1 (20-84) years. Exclusion criteria included any major spinal pathology or surgery, terminal illness, morbid obesity, or any significant comorbid condition. OUTCOME MEASURES GAP scores with LDI parameter removed and GAP-D scores. METHODS Preliminary GAP scores with the LDI parameter removed were assessed in 87 healthy volunteers that met inclusion criteria. The preliminary GAP scores were grouped based on the original GAP system's LDI parameters, and these scores were analyzed to search for discrepancies from the baseline trend. Original GAP scores were calculated for the same 87 healthy volunteers. GAP-D scores were calculated with the same parameters as the GAP score, with the exception of the LDI factor. In GAP-D scores, the number of points were subtracted from each LDI group in the same amount that showed discrepancies in the Preliminary GAP score trend. The percentages of Proportioned, Moderately Disproportioned, and Severely Disproportioned volunteers were then compared between the two scoring systems. RESULTS Preliminary GAP scores shows a 1-point and 4-point discrepancy point in the 40∼49% and CONCLUSIONS Our study examined the LDI parameter in calculation of GAP scores in a healthy US population. In this study, we analyzed how the GAP score system may be attributing a high score to otherwise healthy individuals. We found the percentage of proportioned volunteers increases in the Original GAP score by subtractions at the LDI groups 40∼49% and FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

292. Global Alignment and Proportion (GAP) score with modified age factor: GAP-A score

BACKGROUND CONTEXT The Global Alignment and Proportion (GAP) score is a PI-based method of analyzing the sagittal plane, developed to predict the risk of mechanical complications following spinal correction surgery. Our study examined the age factor of 60 as a parameter for GAP score calculation in a healthy US population. Modifying the age factor with score substractions at the cut-offs of age 65 and 70 creates the Global Alignment and Proportion with Modified Age Factor (GAP-A) Score, which better compensates for the sagittal imbalance that occurs naturally with increasing age and affects the healthy elderly population. The GAP score was developed to predict mechanical complications following spinal correction surgery. It is a pelvic-incidence based method of analyzing the sagittal plane. The GAP parameters include relative pelvic version, relative lumbar lordosis, lordosis distribution index, relative spinopelvic alignment (RSA), and an age factor of 60. An age >= 60 years old receives a score of 1, while age PURPOSE The aim of the study was to adjust the age factor in calculation of GAP scores among healthy United States adult volunteers with no prior spinal pathology, in order to compensate for the natural age-related sagittal imbalance among the elderly population. STUDY DESIGN/SETTING Retrospective review of prospectively collected data PATIENT SAMPLE A total of 87 healthy volunteers were included in the study. Mean age was 54.9±15.1 (20-84) years. Exclusion criteria included any major spinal pathology or surgery, terminal illness, morbid obesity or any significant comorbid condition. OUTCOME MEASURES GAP scores with the age factor removed and GAP-A scores. METHODS Preliminary GAP scores with the age factor removed were assessed in 87 healthy volunteers that met inclusion criteria. The preliminary GAP scores were grouped based on age groups in increments of 5 or 10 years, and these scores were analyzed to search for discrepancies from the baseline trend. Original GAP scores were calculated for the same 87 healthy volunteers. GAP-A scores were calculated with the same parameters as the original GAP scores, with the exception of the age factor. In GAP-A scores, in addition to the age factor of adding 1 point if age>60, the number of points were subtracted from each age group in the same amount that showed discrepancies in the Preliminary GAP score trend. The percentages of Proportioned, Moderately Disproportioned, and Severely Disproportioned volunteers were then compared between GAP scores and GAP-A scores. RESULTS Preliminary GAP scores show a 2- and 4-point discrepancy after age 65 and age 70 respectively. After adjustment those two age groups by subtraction of 2 and 4 points from original GAP scores, the percentages of Proportioned and Moderately Disproportioned increased in GAP-A scoring systems. Conversely, Severely Disproportioned groups decreased in GAP-A scoring system. Proportioned volunteers changed from 47.1% to 52.9%, Moderately Disproportioned volunteers changed from 39.1% to 37.9%, and Severely Disproportioned volunteers changed from 13.8% to 9.2% CONCLUSIONS Our study examined the age factor parameter in calculation of GAP scores in a healthy U.S. population. We found proportioned percentage from Original GAP scores increases by subtractions at age cut-offs of 65 and 70, which was the discrepancies found from Preliminary GAP scores. We called this system the Global Alignment and Proportion with Modified Age Factor (GAP-A) scoring system. This system can be proposed as a better alternative in compensating for the natural sagittal imbalance affecting the healthy elderly population. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

P94. Global alignment and proportion (GAP) score with modified RLL parameter: GAP-L score

BACKGROUND CONTEXT The Global Alignment and Proportion (GAP) score was thus developed to predict such mechanical complications following spinal correction surgery. The GAP score is a pelvic-incidence based method of analyzing the sagittal plane. GAP scores of 0∼2 are classified as proportioned, 3∼6 as moderately proportioned, and >=7 as severely disproportioned. GAP parameters include relative pelvic version, relative lumbar lordosis (RLL), lordosis distribution index, age factor of 60, and relative spinopelvic alignment. RLL categories include: 11° receiving a score of 3. PURPOSE The aim of the study was to adjust the RLL parameter in calculation of GAP scores among US adult volunteers with no prior spinal pathology, in order to compensate for high GAP scores in otherwise healthy individuals. STUDY DESIGN/SETTING Retrospective review of prospectively collected data. PATIENT SAMPLE A total of 87 healthy volunteers were included in the study. Mean age was 54.9±15.1 (20-84) years. Exclusion criteria included any major spinal pathology or surgery, terminal illness, morbid obesity, or any significant comorbid condition. OUTCOME MEASURES GAP scores with RSA parameter removed and GAP-L scores. METHODS Preliminary GAP scores with the RLL parameter removed were assessed in 87 healthy volunteers that met inclusion criteria. The preliminary GAP scores were grouped based on the original GAP system's RLL parameters, and these scores were analyzed to search for discrepancies from the baseline trend. Original GAP scores were calculated for the same 87 healthy volunteers. GAP-L scores were calculated with the same parameters as the GAP score, with the exception of the RLL factor. In GAP-L scores, the number of points were subtracted from each RLL group in the same amount that showed discrepancies in the Preliminary GAP score trend. The percentages of Proportioned, Moderately Disproportioned, and Severely Disproportioned volunteers were then compared between the two scoring systems. RESULTS Preliminary GAP scores shows a 3-point discrepancy point in the CONCLUSIONS Our study examined the RLL parameter in calculation of GAP scores in a healthy US population. In this study, we analyzed how the GAP score system may be attributing a high score to otherwise healthy individuals. We found the percentage of proportioned volunteers increases in the Original GAP score by subtractions at RLL group FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

106. Predictive probability of the global alignment and proportion score for the development of mechanical failure following adult spinal deformity surgery in Asian patients

BACKGROUND CONTEXT The global alignment and proportion (GAP) score is a recently established risk stratification model for mechanical failure (MF) following adult spinal deformity (ASD) surgery. However, the predictive ability of the GAP score is not well studied. PURPOSE This study aimed to validate the predictive probability of the GAP score in an Asian ASD patient cohort. STUDY DESIGN/SETTING This is a multicenter retrospective review of surgically treated ASD patients. PATIENT SAMPLE This study included 257 surgically treated ASD patients who had a minimum of 5 fused segments, completed a 2-year follow-up, and were selected by consecutive sampling (53 ± 19 years, females: 236 [92%]). OUTCOME MEASURES Development of MF (PJK, PJF, rod breakage, DJK, etc. Variables included age, gender, BMI, BMD, frailty, comorbidities, fusion level, UIV and LIV, revision, PSO, LIF, postoperative neurological deficit, spinal alignment, GAP score, Schwab-SRS type, surgical time, and blood loss). METHODS Comparisons of the immediate postoperative GAP scores between MF the and MF-free groups were performed. We evaluated the discriminative ability of the GAP score based on the area under the receiver operating characteristic curve (AUROC). The Cuzick test was performed to determine whether there is a trend between the GAP score and the incidence of MF or revision surgery. Univariate logistic regression analyses were performed to explore the associations between the GAP score and the incidence of MF or revision surgery. RESULTS No difference was observed in the GAP score between the MF and MF-free groups (MF vs MF-free; GAP: 5.9±3.3 vs 5.2±2.7, p=0.07). The Cuzick analysis showed no trend between the GAP score and the risk for MF or revision surgery. Likewise, the MF rate was not correlated with the GAP score, as shown by the ROC curve (AUC of 0.56 [95% CI 0.48–0.63], p=0.124). Univariate logistic regression confirmed no associations between the GAP score and the incidence of MF or revision surgery (MF; MD [moderately disproportioned]: OR: 0.6 [95% CI: 0.3-1.2], p=0.17, SD [severely disproportioned]: OR: 1.2 [95% CI: 0.6-2.3], p=0.69, revision surgery; MD: OR: 0.8 [95% CI: 0.2-2.8[, p=0.71, SD: OR: 1.2 [95% CI: 0.9-8.7], p=0.08). CONCLUSIONS In this multicenter study, in an Asian ASD patient cohort, the GAP score was not associated with the incidence of MF or revision surgery. Additional studies on the predictive ability of the GAP score in different patient cohorts are warranted. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

291. Adjustment of the global alignment and proportion scores accounting for frailty in adult spinal deformity surgical patients

BACKGROUND CONTEXT Frailty is a baseline measure of disability that transcends age alone and has been determined a strong predictor of outcomes following adult spinal deformity (ASD) surgery. This postop impact calls for investigation of unique adjustment of Global Alignment and Proportion (GAP) scores accounting for frailty. This adjustment in spinal proportion may help surgical planning for individualized, optimal postop outcomes. PURPOSE Modify the GAP score with frailty to optimize outcomes in surgical ASD patients. STUDY DESIGN/SETTING Retrospective review of a single-surgeon comprehensive ASD database PATIENT SAMPLE A total of 140 ASD patients OUTCOME MEASURES Frailty-adjusted GAP scores; Health Related Quality of Life scores (HRQLs): ODI, SRS-22 METHODS Surgical ASD patients (SVA≥5cm, PT≥25°, or TK ≥60°, >3 levels fused) ≥18 years old with available baseline (BL) radiographic data were isolated in the single-center Comprehensive Spine Quality Database (Quality). Patients were dichotomized by the ASD frailty index, F (Not Frail, Frail). Linear regression analysis established radiographic equations for frailty-adjusted GAP Scores at baseline and 2-years involving relative pelvic version, relative lumbar lordosis, lordosis distribution index, relative spinopelvic alignment, and an age factor to formulate a sagittal plane score. Patients were restratified into frailty-adjusted proportionality groups: Proportional ( 7). Frailty-adjusted GAP proportionality at 2-years were compared to adjusted-BL to determine whether patients improved, deteriorated or remained the same in their spine proportion. RESULTS A total of 140 patients were included (55.5±16.4 yrs, 77.5% female, 25.2±4.7 kg/m2). BL frailty: 32.8% not frail, 67.2% frail. Primary analyses demonstrated correlation between BL frailty score and BL and 2-year GAP scores(P 33.5%) compared to Proportional (12.8%), p=0.015. SD 2-year patients developed increased PJK at the 1-year mark (40%, Proportional: 13.9%, MD:7.1%, p=0.003), as well as had worse 2-year ODI and SRS-22 satisfaction scores(p CONCLUSIONS Significant associations exist between frailty and spinal proportion. By adjusting the GAP proportionality groups accounting for baseline frailty contributed to improved outcomes and minimized reoperations. The adjusted GAP groups appeal for less rigorous spine proportion goals in severely frail patients. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Global alignment and proportion (GAP) scores in an asymptomatic, nonoperative cohort: a divergence of age-adjusted and pelvic incidence-based alignment targets.

To investigate GAP scores in an asymptomatic cohort of adults, including older adults with age-expected changes in spinal alignment. One hundred and twenty asymptomatic volunteers underwent full-body radiographic scans. Demographics and sagittal radiographic parameters (pelvic incidence, sacral slope, L1-S1 lordosis, L4-S1 lordosis, and global tilt) were measured and GAP scores calculated ( www.gapcalculator.com ). Mann-Whitney U test compared groups. Eighty-five individuals (65 female, average age 48 ± 16 years, BMI 27 ± 6kg/cm2) were analyzed. The median GAP score was that of a proportioned spine (0, range 0-10). 20% were moderately disproportioned and 6% were severely disproportioned. The mean relative pelvic version, relative lumbar lordosis (RLL), lumbar distribution index (LDI), and relative spinopelvic alignment were all considered aligned, although the mean RLL and LDI scores were both greater than 1. When categorized by age (< 60 years, ≥ 60 years), the median GAP score of the younger group was 0 (normal), while the median GAP score of the older cohort was 1 (normal) and different from the younger group (p < 0.001). Most patients in this asymptomatic, nonoperative cohort were normally proportioned. However, a large percentage of asymptomatic volunteers were moderately or severely disproportioned. Older patients had higher scores, indicating some disproportion. There was also a small number of severely sagittally misaligned and poorly proportioned, yet asymptomatic, volunteers. Further refinement of individualized targets is needed to determine the effect on mechanical complications and quality of life given the divergent recommendations of age-adjusted targets and GAP targets.

Predictors of Poor Global Alignment and Proportion Score After Surgery for Adult Spinal Deformity.

Retrospective observational study of a cohort of consecutive patients. To determine 1) the correlation between clinical and radiographic outcomes and Global Alignment and Proportion (GAP) score, and 2) which preoperative parameters predominantly influence the risk for poor GAP scores. Although numerous investigators have indicated their criteria for sagittal correction, it is still not unusual to observe poor outcome or complications even after ideal correction. The recently developed GAP score indicates spinopelvic alignment and setting surgical goals according to the score might decrease the prevalence of mechanical complications. However, there is no clear evidence of correlation between the GAP score and clinical outcomes, or which patient factors are preoperative predictors of poor postoperative GAP score. We included 128 consecutive patients treated with spinal correction surgery who had a minimum 2-year follow-up. The correlations between clinical outcomes, increased proximal junctional angle, and GAP score were determined. Univariate and multivariate logistic regression analyses were conducted to clarify potential preoperative risk factors for poor GAP score. Based on total GAP score, 32 (25%) patients were grouped into proportioned, 50 (39.1%) into moderately disproportioned, and 44 (34.3%) into severely disproportioned spinopelvic alignment. Our present study showed a significantly positive correlation between Oswestry Disability Index, increased proximal junctional angle 2 years after surgery, and total GAP score. Uni and multivariate regression analysis showed a large global tilt was a risk factor for a poor GAP score and that the risk for a poor GAP score increased with ageing. Because GAP score correlated with Oswestry Disability Index and increased proximal junctional angle 2 years after surgery, GAP score might define targets for sagittal spinopelvic alignment for favorable outcomes of corrective spinal surgery. A large preoperative global tilt is a potential predictor of poor postoperative GAP score. 3.

321. Evaluation of global alignment and proportion score in an independent adult spinal deformity database

BACKGROUND CONTEXT Sagittal spino-pelvic alignment has been associated with patient-reported outcome measures and mechanical complication rates. Linear numerical values of pelvic tilt and lumbar lordosis measurements with different pelvic incidences may be misleading. The use of “relative” measurements embedded in a weighted scoring of Global Alignment and Proportion (GAP) has been described. The purpose of our study was to evaluate the validity of the GAP score in an independent database. PURPOSE The purpose of our study was to evaluate the validity of the GAP score in an independent database. STUDY DESIGN/SETTING Retrospective review of an independent adult spinal deformity data base from a single center. PATIENT SAMPLE Adult spinal deformity patients from a single center who had >5 level fusion to the pelvis between 2004-2014. OUTCOME MEASURES Demographic, clinical, surgical and radiographic parameters. METHODS ASD patients who underwent ≥5 levels fusion to the pelvis between 2004 to 2014 were included. Demographic, clinical, surgical and radiographic patient characteristics were recorded. Cochran-Armitage tests were used to determine mechanical complication trends across GAP categories. Uni /multivariable logistic regression analyses were used to obtain crude and adjusted odds ratios of predictor (GAP categories) and the outcome (mechanical complication). The diagnostic performance of the GAP score was tested using the area under the receiver operating characteristic curve, sensitivity, specificity, positive predictive value, negative predictive value and accuracy in predicting mechanical complications. RESULTS A total of 338 out of 657 patients (295F, 43M) with a mean age of 58±9.6 met the inclusion criteria. Mean follow-up was 55 months (24-138). Every mechanical complication was included from minor proximal compression fracture and iliac screw disengagement. Most common complications were rod failure in 25.4% (86/338) patients, 23 patients (6.8%) implant complication at the L-S junction, PJF in 45 patients (13.3%) and PJK in 20 pts (5.9%). Mechanical complication in proportioned (GAP-P), moderately (GAP-MD) and severely disproportioned (GAP-SD) patients were 23.8%, 55.7% and 66.1%, respectively. AUC for the GAP score was 0.653 (95% CI, 0.59 to 0.71, p CONCLUSIONS This study validates the efficacy of GAP Score in predicting mechanical complications in an independent database. A trend was observed in which lower GAP scores were associated with lower rates of mechanical complications. Both the crude and adjusted odds ratios were high, showing the extent of effectiveness of this predictive tool. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.