Letter to the Editor: Alignment Goals in Adult Spinal Deformity Surgery

Letter to the editor

Letter to the Editor regarding: Javier Pizones, Jeffrey Hills, Michael P. Kelly, Fatemeh Alavi, Susana Nuñez-Pereira, Zeeshan M. Sardar, Lawrence G. Lenke, Stephen J. Lewis, AO Spine Knowledge Forum Deformity. Alignment Goals in Adult Spinal Deformity Surgery. Global Spine J. Volume 15 Issue 3_suppl, July 2025, Special Issue: Adult Spinal Deformity: Understanding the Controversies and Looking to the Future. ¹

I read this extraordinary publication about Alignment Goals in Adult Spinal Deformity Surgery, which clearly and thoroughly explained the spinal parameters currently used for an adequate assessment of adult spinal deformities, for proper surgical planning, and how they would impact not only patients’ quality of life but also mechanical complications. However, after reviewing the article thoroughly, I have two observations on pages 116 and 117 of the article:

1. The article discusses the Roussouly Classification, where it states: “The downside of his classification (and any other) is that it categorizes patients by PI when PI describes a continuum”. ¹ However, the fundamental disadvantage of the classification is that it uses the Sacral Slope (SS) to categorize patients into four spinal shapes initially. However, due to the degenerative changes that the spine undergoes, this parameter is affected, which can lead to errors in patient classification. ² This is where Sebaaly et al., ³ in their article, clarify these degenerative changes that the spine undergoes and make a classification of the degenerative evolution of the Roussouly classification, clarifying this difficulty.

2. Furthermore, the article mentions: “The reciprocal relationships between sacral orientation and spinal sagittal shape characteristics were well described in the study by Laouissat et al, which illustrated that as an undercountoured rod induces a pelvic retroversion, an overcountoured rod causes postoperative hyperlordosis leading to postoperative iatrogenic anteversion of the pelvis”. ¹ But I believe that the significant contribution of Laouissat et al. ⁴ in this regard was the refounding of the Roussouly classification, initially using Pelvic Incidence (PI) as a parameter to recategorize patients, dividing them into two groups: PI < 50° and > 50°. Then, using SS, they facilitated the recategorization of spinal shape and found a new group: type 3 Anteverse Pelvic (3AP). It was characterized by a PI < 50° and SS between 35° - 45° and Pelvic Tilt (PT) < 8° (Anteverse). ⁴

The article is truly a masterpiece, encompassing all current concerns and the evolution of spinal sagittal alignment in adult spinal deformities. I can only say congratulations on such magnificent work.

I hope that my explanations and observations will be helpful to readers of this valuable journal.