Abstract
Thank you to our esteemed colleagues for their engagement with this article. Our team appreciates your insight and will provide further comments below.
Firstly, you stated that a reason for the mismatch between the current and theoretical Roussouly Type 3 classification is that the Type 3AP subtype was not included in this manuscript. We chose not to include Type 3AP because there is no definition of Type 3AP spine morphology in the literature of current Roussouly types by Passias et al and Pizones et al, whose system of classifying current Roussouly types we based this manuscript on.1,2 A future project is to collaborate with our colleagues in defining a Type 3AP morphology, particularly for the current Roussouly type system.
Secondly, you noted that the discrepancy in spinal morphology parameters between the current and theoretical Roussouly classifications could be due to the subjects’ degenerative process and that if asymptomatic people were studied, there would be no difference in their classifications. Indeed, in our Discussion section, we have considered this degenerative process, as you pointed out, as a factor underlying the discrepancy between the current and theoretical Roussouly classifications. However, our cohort contains solely asymptomatic individuals, and we cannot exclude the possibility that the observed current-theoretical mismatch is physiologic. Because our analysis is cross-sectional, a longitudinal cohort study, where volunteers are tracked throughout their lives, is needed to understand the complexity behind spinal degenerative change and how it affects the current-theoretical mismatch. We believe the idea of this longitudinal study is in the same vein as your suggestion on incorporating Le Huec et al. 3 ’s formulas to define spinal degeneration’s effect on spine morphology.
