Global Alignment And Proportion Score Research Articles

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.

P92. Preventing rod failure in pedicle subtraction osteotomy revision surgeries for sagittal deformity with a satellite rod technique

BACKGROUND CONTEXT Pedicle subtraction osteotomy (PSO) is used to treat rigid sagittal deformities. The traditional 2-rod PSO technique has resulted in high instrumentation failure rates. We investigated the use of a multiple rod satellite configuration for PSO. PURPOSE Demonstrate that a multiple rod satellite configuration for PSO will result in substantial improvement in sagittal parameters and global alignment and proportion (GAP) score with a low instrumentation failure rate. STUDY DESIGN/SETTING Case series. PATIENT SAMPLE Patients who underwent PSO with a multiple rod satellite rod technique during revision surgery for sagittal plane deformity by a single surgeon. OUTCOME MEASURES Instrumentation failure and sagittal parameters including PSO angle, proximal junctional kyphosis, sagittal vertical axis (SVA), pelvic incidence – lumbar lordosis (PI-LL) mismatch and GAP score. METHODS Independent observers collected demographics, surgical variables, and radiographic measurements from 40 patients who underwent revision surgery for sagittal deformity with a PSO. Procedures were performed by a single surgeon at two different centers. Student's t test compared groups. RESULTS A total of 40 patients underwent PSO with satellite rod technique. Eight were smokers and 7 were diabetic. The most common level was L3 (91%), with 9% at L4. Low dose BMP (1-2 large kits) was distributed over all segments and supplemental allograft was used in all patients. No intradiscal fusion was performed with PSOs, but all patients were previously fused. Mean PSO angle was 28.7±7.6°. Two out of 40 patients had rod fracture necessitating revision surgery at 32 and 34 months. One patient developed an infection requiring replacement of instrumentation. Three patients developed proximal junctional kyphosis, none required revision. Mean preoperative SVA was 13.5±7.3 cm, which significantly decreased to 4.8±7.3 cm (p = 0.002). Mean preoperative PI-LL mismatch was 35.9±16.6, which significantly improved to 11.8±14.6 post-op (p CONCLUSIONS Despite a high rate of comorbid conditions and severely disproportioned postoperative GAP scores, rod failure rate after PSO with the multiple rod satellite configuration was very low (5%) compared to previous reports. SVA and PI-LL mismatch were significantly improved. GAP score was also significantly improved, but still considered severely disproportioned, most likely due to the high rate of PSO's at L3 in previously fused spines, which did not correct low lumbar lordosis. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Sagittal spinal parameters after en bloc resection of mobile spine tumors

Background contextEn bloc resection and reconstruction (EBR) in patients with spinal malignancy aims to achieve local disease control. This is an invasive procedure with significant alterations of the physiological anatomy and subsequently, the spino-pelvic alignment. Sagittal spinal parameters are useful measurements to objectively identify disproportionate alignment on a radiograph. In the field of spinal deformities, there is increasing evidence for a relationship between sagittal alignment and patient reported outcomes. PurposeTo determine sagittal spino-pelvic alignment after EBR in patients with spinal malignancies and the effect of these parameters on surgical and patient reported outcomes. Study DesignA retrospective case series. MethodsWe included 35 patients who underwent EBR for spinal malignancies between 2000 and 2018. Radiographic measurements were performed using semi-automatic software; the parameters included were pelvic incidence (PI), sacral slope, pelvic tilt (PT), global tilt and lumbar lordosis. We calculated PI-based Global Alignment and Proportion (GAP) scores and prospective patient reported outcome scores Patient-Reported Outcome Measurement Information System–Physical Function (PROMIS-PF) were used. ResultsTwenty-one (60%) patients filled out the PROMIS-PF score at a median of 16 months (Interquartile Range (IQR) 4–108) after surgery with a median score of 39 (IQR 32–42), the median GAP score was 7 (IQR 5–9). Bivariate analysis showed no statistically significant relationship between GAP score and instrumentation failure or need for revision surgery. Multivariable analysis of GAP score and PROMIS-PF score corrected for local disease recurrence showed a statistically significant correlation coefficient of −1.721 (p=.026; 95%CI=−3.216, −0.226). ConclusionIn this cohort, all patients had a moderate or severe disproportioned spinal alignment after EBR and reconstruction surgery. The degree of sagittal spino-pelvic misalignment after EBR for spinal malignancies seems to be associated with patient reported health status in terms of PROMIS-PF scores. Further research with a larger patient cohort and standardized imaging and follow-up protocols is necessary in order to accurately use sagittal alignment as a predictive value for instrumentation failure and revision surgery.

Ability of the Global Alignment and Proportion Score to Predict Mechanical Failure Following Adult Spinal Deformity Surgery—Validation in 149 Patients With Two-Year Follow-up

Study DesignRetrospective analysis of prospectively collected data. ObjectivesTo validate the Global Alignment and Proportion (GAP) score in a single-center cohort of adult spinal deformity (ASD) patients. Summary of Background DataSurgical treatment for ASD is associated with a high risk of mechanical failure and consequent revision surgery. To improve prediction of mechanical complications, the GAP score was developed with promising results. Development was based on the assumption that not all patients would benefit from the same fixed radiographic targets as pelvic incidence is an individual, morphological parameter that greatly influences the sagittal curves of the spine. MethodsIn a validation study of the GAP score, patients undergoing ASD surgery with four or more levels of instrumentation were consecutively included at a tertiary spine unit. Patients were followed for a minimum of two years. Pre- and postoperative GAP score and categories were calculated for all patients, and the association with mechanical failure and revision surgery was analyzed. ResultsA total of 149 patients with a mean age of 57.4 years were included. Overall, the rates of mechanical failure and revision surgery were 51% and 35% respectively. The area under the curve (AUC) using receiver operating characteristic was classified as “no or low discriminatory power” for the GAP score in predicting either outcome (AUC = 0.50 and 0.49, respectively). Similarly, there were no significant associations between GAP categories and the occurrence of mechanical failure or revision surgery when using Cochran-Armitage test of trend (p = .28 for mechanical failure and p = .58 for revision surgery). ConclusionsIn a consecutive series of surgically treated ASD patients, we found no significant association between postoperative GAP score and mechanical failure or revision surgery. Despite minor limitations in similarities to the original study cohort, further validation studies or adjustments to the original scoring system are proposed. Level of EvidenceLevel II.

Prediction of mechanical complications in adult spinal deformity surgery—the GAP score versus the Schwab classification

Background contextSurgery for adult spinal deformity is a challenging and complex procedure with high reported complication (8.4%–42%) and revision rates (9%–17.6%). Failure to achieve or maintain adequate postoperative sagittal alignment has been reported to be the main cause of mechanical complications. In order to define appropriate surgical targets, the Scoliosis Research Society-Schwab classification and the Global Alignment and Proportion (GAP) score were established. In the literature, no study has yet compared these classification systems with respect to the risk of developing mechanical complications. PurposeTo assess and compare the ability of the Schwab classification and the GAP score to predict mechanical complications following adult spinal deformity surgery. Study designTwo-center, retrospective cohort study. Patient sampleThirty-nine patients suffering adult spinal deformity who underwent long segment spinal fusion (≥4 levels), minimum follow-up of 2years. Outcome measuresThe ability of the Schwab classification and GAP score to predict mechanical failure was determined by computing the Area Under the receiver operating characteristic curve. MethodsFull-spine pre- and postoperative radiographs of all patients were analyzed for mechanical complications. Subsequently, the pre- and postoperative Schwab and GAP score were determined. Logistic regression analysis was used to assess the ability of both systems to determine which was the most appropriate for the prediction of mechanical failure. Correlations between the various factors constituting the GAP score and Schwab classification were estimated using the Spearman rank order correlation coefficient. ResultsThe results demonstrated that both classification systems are capable of predicting radiographic evidence of mechanical failure; however, the GAP score proved to be significantly better (p=.003). The relative pelvic version of the GAP score serves a similar role as the pelvic tilt modifier from the Schwab classification (ρ=−0.84, p<.01). The relative lumbar lordosis from the GAP score functions much like the PI-LL modifier from the Schwab classification (ρ=−0.94, p<.01). The GAP score is most significantly dependent on relative spinopelvic alignment, relative lumbar lordosis, and relative pelvic version (ρ=0.85, ρ=0.84, and ρ=0.84, respectively, p<.01). Correlation with the lordosis distribution index was also significant but was not as strong (ρ=0.65, p<.01). Age, on the contrary, showed poor correlation with the GAP score (ρ=0.17, p=.300). ConclusionsBoth the Schwab classification and the GAP score are capable of predicting mechanical complications. The GAP score proved to be significantly more appropriate. This difference is probably attributed to the fact that in the GAP score all parameters are related to the patient's individual pelvic incidence.

Global Alignment and Proportion (GAP) Score: Development and Validation of a New Method of Analyzing Spinopelvic Alignment to Predict Mechanical Complications After Adult Spinal Deformity Surgery.

The restoration of normal sagittal alignment is a critical goal in adult spinal deformity surgery to achieve favorable outcomes and prevent mechanical complications. Schwab sagittal modifiers have been accepted as targets for appropriate alignment, but addressing these targets does not always prevent high mechanical complication or revision rates. This may be because the linear absolute numerical parameters do not cover the whole pelvic incidence spectrum and the distribution of lordosis, pelvic anteversion, and negative malalignment are not considered as potential causes of failure. The aim of the present study was to develop and validate a score based on pelvic-incidence-based proportional parameters to better predict mechanical complications. Two hundred and twenty-two patients (168 women and 54 men) followed for ≥2 years after posterior fusion at ≥4 levels were included in the study. The mean age (and standard deviation) was 52.2 ± 19.3 years (range, 18 to 84 years), and the mean duration of follow-up was 28.8 ± 8.2 months (range, 24 to 62 months). The global alignment and proportion (GAP) score was developed and validated in groups of patients randomly assigned to derivation (n = 148, 66.7%) and validation (n = 74, 33.3%) cohorts. GAP score parameters were relative pelvic version (the measured minus the ideal sacral slope), relative lumbar lordosis (the measured minus the ideal lumbar lordosis), lordosis distribution index (the L4-S1 lordosis divided by the L1-S1 lordosis multiplied by 100), relative spinopelvic alignment (the measured minus the ideal global tilt), and an age factor. Proximal and distal junctional kyphosis and/or failure, rod breakage, and other implant-related complications were considered mechanical complications. The predictive accuracy of the GAP score was analyzed using receiver operating characteristic (ROC) analyses. Associations between GAP categories and mechanical complications and revisions were analyzed using Cochran-Armitage tests. In the validation cohort, 32 patients (43%) experienced mechanical complications and 17 (23%) underwent mechanical revision. The area under curve for the GAP score predicting mechanical complications was 0.92 (standard error [SE] = 0.034, p < 0.001, 95% [confidence interval [CI] = 0.85 to 0.98). Postoperatively, patients with a proportioned spinopelvic state according to the GAP score had a mechanical complication rate of 6% while those with a moderately or severely disproportioned spinopelvic state had rates of 47% and 95%, respectively. The GAP score is a new pelvic-incidence-based proportional method of analyzing the sagittal plane that predicts mechanical complications in patients undergoing surgery for adult spinal deformity. Setting surgical goals according to the GAP score may decrease the prevalence of mechanical complications.

188 - Global Alignment and Proportion (GAP) Score Better Correlates to HRQoL Scores and Better Predicts Mechanical Complications Compared to Schwab Sagittal Modifiers

BACKGROUND CONTEXT: Schwab modifiers were established on the basis of patient-reported outcomes. Their impact on mechanical complications has not been tested. Schwab sagittal modifiers may be useful for average PI sizes but it may be insufficient or misleading for the patients who have upper and lower normal PI values, since they rely on given absolute values. Global alignment and proportion (GAP) score comprised PI-based parameters of relative pelvic bersion (measured minus ideal sacral slope), relative lumbar lordosis (measured minus ideal lumbar lordosis), lordosis distribution index (L4-S1 lordosis/L1-S1 lordosis x100), relative spinopelvic alignment (measured minus ideal global tilt) and age factor. GAP score of 0–2 is proportioned, while 3–6 is moderately disproportioned and ≥7 is severely disproportioned. GAP score quantifies spinopelvic shape and alignment on a given person's respective realignment needs for every PI size.