• Louis Boissière, Mitsuru Takemoto, Anouar Bourghli, Jean-Marc Vital, Ferran Pellisé, Ahmet Alanay, Caglar Yilgor, Emre Acaroglu, Francisco Javier Perez-Grueso, Frank Kleinstück, Ibrahim Obeid, and European Spine Study Group (ESSG).
• Spine Unit 1, Bordeaux University Hospital, Place Amélie Raba-Léon, 33076 Bordeaux, France. Electronic address: boissierelouis@yahoo.fr.
• Spine J. 2017 Apr 1; 17 (4): 480-488.

Background ContextMany radiological parameters have been reported to correlate with patient's disability including sagittal vertical axis (SVA), pelvic tilt (PT), and pelvic incidence minus lumbar lordosis (PI-LL). European literature reports other parameters such as lumbar lordosis index (LLI) and the global tilt (GT). If most parameters correlate with health-related quality of life scores (HRQLs), their impact on disability remains unclear.PurposeThis study aimed to validate these parameters by investigating their correlation with HRQLs. It also aimed to evaluate the relationship between each of these sagittal parameters and HRQLs to fully understand the impact in adult spinal deformity management.Study DesignA retrospective review of a multicenter, prospective database was carried out.Patient SampleThe database inclusion criteria were adults (>18 years old) presenting any of the following radiographic parameters: scoliosis (Cobb ≥20°), SVA ≥5 cm, thoracic kyphosis ≥60° or PT ≥25°. All patients with complete data at baseline were included.Outcome MeasuresHealth-related quality of life scores, demographic variables (DVs), and radiographic parameters were collected at baseline.MethodsDifferences in HRQLs among groups of each DV were assessed with analyses of variance. Correlations between radiographic variables and HRQLs were assessed using the Spearman rank correlation. Multivariate linear regression models were fitted for each of the HRQLs (Oswestry Disability Index [ODI], Scoliosis Research Society-22 subtotal score, or physical component summaries) with sagittal parameters and covariants as independent variables. A p<.05 value was considered statistically significant.ResultsAmong a total of 755 included patients (mean age, 52.1 years), 431 were non-surgical candidates and 324 were surgical candidates. Global tilt and LLI significantly correlated with HRQLs (r=0.4 and -0.3, respectively) for univariate analysis. Demographic variables such as age, gender, body mass index, past surgery, and surgical or non-surgical candidate were significant predictors of ODI score. The likelihood ratio tests for the addition of the sagittal parameters showed that SVA, GT, T1 sagittal tilt, PI-LL, and LLI were statistically significant predictors for ODI score even adjusted for covariates. The differences of R2 values from Model 1 were 1.5% at maximum, indicating that the addition of sagittal parameters to the reference model increased only 1.5% of the variance of ODI explained by the models.ConclusionGT and LLI appear to be independent radiographic parameters impacting ODI variance. If most of the parameters described in the literature are correlated with ODI, the impact of these radiographic parameters is less than 2% of ODI variance, whereas 40% are explained by DVs. The importance of radiographic parameters lies more on their purpose to describe and understand the malalignment mechanisms than their univariate correlation with HRQLs.Copyright © 2016 Elsevier Inc. All rights reserved.

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