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. 2024 May;14(4):1110-1115.
doi: 10.1177/21925682221133748. Epub 2022 Oct 7.

Quantifying the Spinal Lordosis Ratio Unique to the Type of Spinal Sagittal Alignment in a Normal Population

Thomas Chevillotte  1 , Sook-Kwan Chan  2 , Pierre Grobost  1 , Fethi Laouissat  3 , Alice Darnis  1 , Clément Silvestre  1 , Pierre Roussouly  4
Affiliations

Quantifying the Spinal Lordosis Ratio Unique to the Type of Spinal Sagittal Alignment in a Normal Population

Thomas Chevillotte et al. Global Spine J. 2024 May.

Abstract

Study design: Data collection of radiological parameters in non-pathological adult spines.

Objectives: Establishing a baseline database for measurements of the spinal lordosis ratio between upper and lower arcs of the lumbar spine unique to each type of spine described by Roussouly's classification. Illustrating the importance of correct rationing of the upper and lower arcs.

Methods: Standardised standing true lateral plain radiographs of the spine (including base of skull and proximal femurs) from 373 adult volunteers were obtained. Exclusion criteria : any history of disease involving the spine, pelvis, hips or lower limbs. Incidental detection of any spinal deformity on radiography also excluded further participation in this study. Sacro-pelvic parameters data collected : Pelvic Incidence (PI), Pelvic Tilt (PT), Sacral Slope (SS), location of Inflection Point, number of vertebras in the spinal lordosis and type of Roussouly's spine. Values of upper arc, lower arc and spinal lordosis ratio (SLR) was determined.

Results: Bivariate analysis revealed statistically significant (P < .0001) correlation between the types of sagittal spinal alignments based on Roussouly's classification and the SLR. Type 1: SLR .76 ± .17, Type 2: SLR .60 ± .18, Type 3 with anteverted pelvis: SLR .53 ± .11, Type 3: SLR .49 ± .12, Type4: SLR .41 ± .11.

Conclusion: With this data we are able to quantify the ratio of lumbar lordosis unique to each type of Roussouly's spine. It functions as a guide when planning lumbar spine surgeries in order to restore the SLR correctly and thus prevent post-op complications such as proximal junction kyphosis.

Keywords: Roussouly’s classification; lower lumbar arc; pelvic incidence; sacral slope; spinal lordosis ratio; spine sagittal alignment; upper lumbar arc.

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Conflict of interest statement

Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Figures

Figure 1.
Figure 1.
Inflection point is where lordosis turns into kyphosis, Upper lumbar arc (θ) which is usually constant at 20°, Lower lumbar arc (β) which is equivalent to sacral slope (SS) angle.
Figure 2.
Figure 2.
Distribution of SL ratio according to SS by Roussouly’s Classification (type 1 = black, type 2 = red, type 3 AP = yellow, type 3 = green, type 4 = blue).
Figure 3.
Figure 3.
Distribution of SL ratio according to PI by Roussouly’s Classification (type 1 = black, type 2 = red, type 3 AP = yellow, type 3 = green, type 4 = blue).
Figure 4.
Figure 4.
Linear regression between PI and spinal lordosis ratio (SLR).
Figure 5.
Figure 5.
Linear regression between PT and spinal lordosis ratio (SLR).
Figure 6.
Figure 6.
Linear regression between SS and spinal lordosis ratio (SLR).
Figure 7.
Figure 7.
Illustration demonstrating each type of spine according to Roussouly’s classification and its corresponding LL, lower arc and SL ratio.
See this image and copyright information in PMC

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