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

Abstract

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.