Global Alignment And Proportion Score Research Articles

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.

Characterization of Patients with Poor Risk for Clinical Outcomes in Adult Symptomatic Lumbar Deformity Surgery.

Retrospective review of 159 surgically treated consecutive adult symptomatic lumbar deformity (ASLD) (65 ± 9 years, female: 94%) from a multicenter database. The aim of this study was to provide a comprehensive analysis of the risk of a poor clinical outcome in ASLD surgery. Poor-risk patients with ASLD remain poorly characterized. ASLD was defined as age >40 years with a lumbar curve ≥30° or C7SVA ≥5 cm and Scoliosis Research Society 22 (SRS22) pain or function <4. Poor outcome was defined as 2y SRS22 total <4 or pain, function or satisfaction ≤3. The outcomes of interest included age, sex, body mass index, bone mineral density, Schwab-SRS type, frailty, history of arthroplasty, upper-instrumented vertebral, lower-instrumented vertebral, levels involved, pedicle subtraction osteotomy, lumbar interbody fusion, sagittal alignment, global alignment and proportion (GAP) score, baseline SRS22r score, estimated blood loss, time of surgery, and severe adverse event (SAE). Poisson regression analyses were performed to identify the independent risks for poor clinical outcome. A patient was considered at poor risk if the number of risks was >4. All SRS22 domains were significantly improved after surgery. In total, 21% (n = 34) reported satisfaction ≤3 and 29% (n = 46) reported pain or function ≤3. Poisson regression analysis revealed that frailty (odds ratio [OR]: 0.2 [0.1-0.8], P = .03), baseline mental-health (OR: 0.6 [0.4-0.9], P = .01) and function (OR: 1.9 [1.0-3.6], P < .01), GAP score (OR: 4.6 [1.1-18.7], P = .03), and SAE (OR: 3.0 [1.7-5.2], P < .01) were identified as independent risk for poor clinical outcome. Only 17% (n = 6) of the poor-risk patients reached SRS22 total score >4.0 at 2 years. The overall clinical outcome was favorable for ASLD surgery. Poor-risk patients continue to have inferior outcomes, and alternative treatment strategies are needed to help improve outcomes in this patient population. Recognition and optimization of modifiable risk factors, such as physical function and mental health, and reduced SAEs may improve overall clinical outcomes of ASLD surgery.Level of Evidence: 3.

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.

Are Higher Global Alignment and Proportion Scores Associated With Increased Risks of Mechanical Complications After Adult Spinal Deformity Surgery? An External Validation.

BackgroundThe Global Alignment and Proportion (GAP) score, based on pelvic incidence-based proportional parameters, was recently developed to predict mechanical complications after surgery for spinal deformities in adults. However, this score has not been validated in an independent external dataset.Questions/purposesAfter adult spinal deformity surgery, is a higher GAP score associated with (1) an increased risk of mechanical complications, defined as rod fractures, implant-related complications, proximal or distal junctional kyphosis or failure; (2) a higher likelihood of undergoing revision surgery to treat a mechanical complication; and (3) is a lower (more proportioned) GAP score category associated with better validated outcomes scores using the Oswestry Disability Index (ODI), Scoliosis Research Society-22 (SRS-22) and the Short Form-36 questionnaires?MethodsA total of 272 patients who had undergone corrective surgeries for complex spinal deformities were enrolled in the Scoli-RISK-1 prospective trial. Patients were included in this secondary analysis if they fulfilled the original inclusion criteria by Yilgor et al. From the original 272 patients, 14% (39) did not satisfy the radiographic inclusion criteria, the GAP score could not be calculated in 14% (37), and 24% (64) did not have radiographic assessment at postoperative 2 years, leaving 59% (159) for analysis in this review of data from the original trial. A total of 159 patients were included in this study,with a mean age of 58 ± 14 years at the time of surgery. Most patients were female (72%, 115 of 159), the mean number of levels involved in surgery was 12 ± 4, and three-column osteotomy was performed in 76% (120 of 159) of patients. The GAP score was calculated using parameters from early postoperative radiographs (between 3 and 12 weeks) including pelvic incidence, sacral slope, lumbar lordosis, lower arc lordosis and global tilt, which were independently obtained from a computer software based on centralized patient radiographs. The GAP score was categorized as proportional (scores of 0 to 2), moderately disproportional (scores of 3 to 6), or severely disproportional (scores higher than 7 to 13). Receiver operating characteristic area under curve (AUC) was used to assess associations between GAP score and risk of mechanical complications and risk of revision surgery. An AUC of 0.5 to 0.7 was classified as “no or low associative power”, 0.7 to 0.9 as “moderate” and greater than 0.9 as “high”. We analyzed differences in validated outcome scores between the GAP categories using Wilcoxon rank sum test.ResultsAt a minimum of 2 years’ follow-up, a higher GAP score was not associated with increased risks of mechanical complications (AUC = 0.60 [95% CI 0.50 to 0.70]). A higher GAP score was not associated with a higher likelihood of undergoing a revision surgery to treat a mechanical complication (AUC = 0.66 [95% 0.53 to 0.78]). However, a moderately disproportioned GAP score category was associated with better SF-36 physical component summary score (36 ± 10 versus 40 ± 11; p = 0.047), better SF-36 mental component summary score (46 ± 13 versus 51 ± 12; p = 0.01), better SRS-22 total score (3.4 ± 0.8 versus 3.7 ± 0.7, p = 0.02) and better ODI score (35 ± 21 versus 25 ± 20; p = 0.003) than severely disproportioned GAP score category.ConclusionBased on the findings of this external validation study, we found that alignment targets based on the GAP score alone were not associated with increased risks of mechanical complications and mechanical revisions in patients with complex adult spinal disorders. Parameters not included in the original GAP score needed to be considered to reduce the likelihood of mechanical complications.Level of EvidenceLevel III, diagnostic study.

Does the Global Alignment and Proportion score overestimate mechanical complications after adult spinal deformity correction?

The goal of this study was to validate the Global Alignment and Proportion (GAP) score in a cohort of patients undergoing adult spinal deformity (ASD) surgery. The GAP score is a novel measure that uses sagittal parameters relative to each patient's lumbosacral anatomy to predict mechanical complications after ASD surgery. External validation is required. Adult ASD patients undergoing > 4 levels of posterior fusion with a minimum 2-year follow-up were included. Six-week postoperative standing radiographs were used to calculate the GAP score, classified into a spinopelvic state as proportioned (P), moderately disproportioned (MD), or severely disproportioned (SD). A chi-square analysis, receiver operating characteristic curve, and Cochran-Armitage analysis were performed to assess the relationship between the GAP score and mechanical complications. Sixty-seven patients with a mean age of 52.5 years (range 18-75 years) and a mean follow-up of 2.04 years were included. Patients with < 2 years of follow-up were included only if they had an early mechanical complication. Twenty of 67 patients (29.8%) had a mechanical complication. The spinopelvic state breakdown was as follows: P group, 21/67 (31.3%); MD group, 23/67 (34.3%); and SD group, 23/67 (34.3%). Mechanical complication rates were not significantly different among all groups: P group, 19.0%; MD group, 30.3%; and SD group, 39.1% (χ2 = 1.70, p = 0.19). The rates of mechanical complications between the MD and SD groups (30.4% and 39.1%) were less than those observed in the original GAP study (MD group 36.4%-57.1% and SD group 72.7%-100%). Within the P group, the rates in this study were higher than in the original study (19.0% vs 4.0%, respectively). The authors found no statistically significant difference in the rate of mechanical complications between the P, MD, and SD groups. The current validation study revealed poor generalizability toward the authors' patient population.

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.

25. The collective influence of lumbopelvic mismatch and proportional shape on clinical outcomes and proximal junctional kyphosis following adult spinal deformity corrective surgery

BACKGROUND CONTEXT The age-adjusted alignment ideal alignment was proposed in order reduce the occurrence of proximal junctional kyphosis (PJK) in an adult spinal deformity (ASD) population. The normative postoperative age ideal value for the mismatch between pelvic incidence and lumbar lordosis (PI-LL) has yet to be related to the global alignment and proportion (GAP) score postop proportionality. PURPOSE To assess the impact of normative age-adjusted PI-LL and proportionality via GAP score on postoperative patient-reported outcomes. STUDY DESIGN/SETTING Retrospective review of single-surgeon adult spinal deformity (ASD) database PATIENT SAMPLE 140 ASD patients. OUTCOME MEASURES Health-related quality-of-life (HRQLs); SRS-22r; PJK. METHODS ASD patients with baseline (BL) and 2-year postoperative (2Y) radiographic and HRQL data were included. Age-adjusted correction groups generated at postoperative follow-up for actual alignment compared to age-adjusted values for PI-LL-adjusted ideal values (matched, overcorrected, undercorrected). GAP Score in the literature includes the four parameters, and an age factor to formulate a sagittal plane score out of 13 (proportional, moderately disproportional [MD], severely disproportional [SD]). GAP improvement scores were noted as less at 2Y compared to BL. Patients were grouped by age-adjusted and 2Y GAP results: Match PI-LL/Proportional GAP, Match PI-LL/Disproportional GAP, Unmatch PI-LL/Proportional GAP, Unmatch PI-LL/Disproportional GAP. Means comparison and chi-squared ANOVA analyses assessed the outcomes between age-adjusted and GAP groups. RESULTS Included: 140 ASD patients (55.5±16.4 years, 81% female, 25.2±4.7kg/m2). At BL, mean sacral slope: 30.7°, pelvic tilt: 23°, pelvic incidence: 53.5°, PI-LL: 13.3°, SVA: 61.6 mm, and L1-S1: 40.4°. BL GAP proportionality: 17.8% proportional, 27.1% MD, 55% SD. PI-LL by baseline GAP proportionality groups: -6.4° Proportional, -4.6° MD, 26.8° SD, p CONCLUSIONS Collectively over or undercorrecting in age-adjusted mismatch pelvic incidence and lumbar lordosis and becoming disproportional in spinal shape at 2 years led to increased postoperative proximal junctional kyphosis and significantly worse patient-reported outcomes. Surgeons should be wary of the double mal-correction when utilizing these complex realignment schemas. 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.

Identification of Predictive Factors for Mechanical Complications After Adult Spinal Deformity Surgery: A Multi-Institutional Retrospective Study.

A retrospective multicenter observational study. To investigate correction surgeries that were performed in relatively aged patients in terms of mechanical complications (MCs) and their predictive factors. The risk factors associated with MCs have not yet been well examined, especially in aged populations. We retrospectively reviewed 230 surgically treated ASD patients with an average age of 72.2 years. Twenty-eight patients with ASD caused by vertebral fractures were excluded. The minimum follow-up was 2 years. Postoperative MCs were defined as proximal junction kyphosis, distal junction kyphosis, pseudoarthrosis, rod breakage, and vertebral fractures. We divided all the ASD patients into two groups: patients with MC (the MC (+) group) and patients without MC (the MC (-) group). Radiographic parameters were evaluated before and immediately after surgery. The SRS-Schwab ASD classification and global alignment and proportion (GAP) score were also evaluated. Of the 202 patients, 91 (45.0%) had MCs. The age at surgery was significantly higher in the MC (+) group than in the MC (-) group. Regarding radiographic parameters, postoperative global tilt (GT), pre- and postoperative thoracolumbar kyphosis (TLK), and postoperative thoracic kyphosis were significantly higher in the MC (+) group than in the MC (-) group. Other parameters, such as the proposed ideal alignment target of PI-LL<10, did not significantly affect MC rates. The GAP score was high in both groups and not significantly related to a higher rate of MC. Forward stepwise logistic regression indicated that the age at surgery, postoperative GT, and preoperative TLK were significant risk factors for MCs. Older age, higher postoperative GT, and higher pre and postoperative TLK can be risk factors for MCs. The GAP score was high in both groups and not significantly related to a higher rate of MC. 4.

Indications and limitations of minimally invasive lateral lumbar interbody fusion without osteotomy for adult spinal deformity.

The global alignment and proportion (GAP) score was recently developed to consider proportional analysis of spinopelvic alignment and has been indicated for setting surgical goals to decrease the prevalence of mechanical complications. The goal of this study was to clarify the limitations and problems with spinal corrective surgery with minimally invasive lateral lumbar interbody fusion (LLIF) without osteotomy using GAP score, and to establish a preoperative radiographical evaluation to understand the necessity for three-column osteotomy. We included data from 57 consecutive patients treated with spinal corrective surgery with LLIF and without Schwab grade 3-6 osteotomy for ASD. To evaluate flexibility of the pelvis and lumbar spine, we examined full-length lateral radiographs with patients standing and prone. Correlations between pre- and postoperative radiographic parameters and GAP score were determined. Most patients achieved a sufficiently ideal lumbar lordosis (87.7%), but ideal sacral slope (SS) was achieved in only 50.8% of patients. Preoperative prone SS showed a significant positive correlation with postoperative SS and a significant negative correlation with GAP score. Patients whose preoperative prone SS was larger than pelvic incidence × 0.59-7.5 tended to achieve proportioned spinopelvic alignment by using LLIF. The cause of poor outcome of GAP score for ASD corrective surgery with LLIF without osteotomy is a postoperative small SS. Preoperative prone SS is useful for predicting postoperative SS. When preoperative SS in prone patients is relatively small to ideal as calculated using PI, osteotomy or other correctors should be considered to achieve satisfactory spinopelvic parameters. III. These slides can be retrieved under Electronic Supplementary Material.

Prediction of mechanical complications after corrective surgeries in adult degenerative scoliosis: modification and validation of the global alignment and proportion (GAP) score

Objective To modify the global alignment and proportion (GAP) score according to the spinopelvic alignment of healthy volunteers and to validate the reliability of the GAP score and the modified GAP (M-GAP) score in the prediction of mechanical failure after corrective surgeries in adult degenerative scoliosis (ADS). Methods Clinical and radiographical data of 66 ADS patients undergoing correction surgeries in our center between January 2014 and January 2017 were retrospectively reviewed. The average age of the cohort was 60.2±7.1 years, including 13 male patients and 53 female patients. The predictive ability of GAP score to the mechanical failure was validated with Fisher's exact test and Linear-by-linear association test. Sagittal spinopelvic parameters were measured on lateral full-spine X-rays of 67 healthy volunteers aged between 50 and 70. The average age of these subjects was 58.2±5.4 years. Values of spinal and pelvic parameters including pelvic incidence (PI), sacral slope (SS), lumbar lordosis (LL), global tilt (GT) and sagittal vertical axis (SVA) were measured. Simple linear regression analysis was conducted between PI and SS, LL and GT, respectively. The equations of regression analysis were used to calculate patients' ideal SS, LL and GT, and to establish the modified GAP (M-GAP) score. The predictive ability of M-GAP score to the mechanical failure was also validated. Results Sagittal spinal and pelvic parameters of healthy subjects were measured and illustrated. The correlations between SS, LL and PI were SS=0.40×PI+12, LL=0.46×PI+22 and GT=0.46×PI-5. According to the GAP score, the postoperative sagittal spinopelvic alignment was proportioned in 16 (24.2%) cases, moderately disproportioned in 32 (48.5%) cases and severely disproportioned in 18 (27.3%) cases according to the original GAP score, and the occurrence of mechanical complication was 18.8% (3/16), 12.5% (4/32) and 22.2%(4/18) respectively. The GAP categories were not significantly correlated with the prevalence of mechanical failure (P=0.633), and no significant linear correlation was found (χ2=5.022, P=0.822). After re-evaluation of M-GAP score, the postoperative sagittal spinopelvic alignment was proportioned in 32 (48.5%) cases, moderately disproportioned in 25 (37.9%) cases and severely disproportioned in 9 (13.6%) cases, and the occurrence of mechanical failure was 6.3% (2/32), 24.0% (6/25) and 30%(3/9), respectively. The prevalence of mechanical failure was statistically different between proportioned, moderately disproportioned and severely disproportioned spinopelvic alignment patients classified by M-GAP score (P=0.048), and there was a statistically significant linear association between the M-GAP categories and the occurrence of mechanical complications (χ2=0.093, P=0.034). Conclusion Poor predictive ability of the original GAP score to the mechanical failure was detected in ADS patients. However, the modified GAP score seemed to be a reliable predictor for mechanical failure in ADS patients. Key words: Adult; Lumbar vertebrae; Intervertebral disc degeneration; Scoliosis; Postoperative complications

Modified global alignment and proportion scoring with body mass index and bone mineral density (GAPB) for improving predictions of mechanical complications after adult spinal deformity surgery

BACKGROUND CONTEXTThe global alignment and proportion (GAP) score for predicting mechanical complications of adult spinal deformity (ASD) surgery has limitations due to its lack of bone quality and patient characteristics such as obesity, which has a significant impact on surgical outcome, especially in the elderly population with ASD. PURPOSEThis study aimed to improve the predictability of GAP score after ASD surgery by adding body mass index (BMI) and bone mineral density (BMD). DESIGNA retrospective comparative study. PATIENT SAMPLEBetween January 2009 and December 2016, 203 consecutive patients with ASD underwent corrective fusion of more than 4 levels and were followed up for more than 2 years. OUTCOME MEASURESThe ability of the Scoliosis Research Society (SRS)-Schwab classification, age-adjusted alignment goals, GAP score, and modified global alignment and proportion scoring with BMI and BMD (GAPB) to predict mechanical failure was compared by calculating the area under the receiver operating characteristic curve (AUC). METHODSThe GAPB was developed and validated in patients randomly assigned to derivation (n=125, 61.6%) and validation (n=78, 38.4%) cohorts. Considering multicollinearity, a multivariable logistic regression model with BMD, BMI, and the GAP score was constructed. RESULTSPatients’ average age was 66.8±12.28 years, and they were followed for an average of 30.54±10.25 months. Fifty-five patients of the derivation cohort (44%) and 34 patients of the validation cohort (43%) had mechanical complications after ASD surgery. AUCs of the SRS-Schwab classification, GAP score, age-adjusted alignment goals, and GAPB were 0.532 (95% confidence interval [CI], 0.463–0.602), 0.798 (95% CI, 0.720–0.877), 0.568 (95% CI, 0.495–0.641), and 0.885 (95% CI 0.828–0.941), respectively. CONCLUSIONSThe GAPB system, which includes BMI and BMD, showed improved predictability for predicting mechanical complications compared to the GAP score. Given these results, surgeons should keep in mind the importance of bone quality and BMI as well as proportional alignment.

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.