Theoretical discrimination index of postural instability in amyotrophic lateral sclerosis

Rodolphe Vallée,Annabelle Couillandre,Pierre-François Pradat,Jean-Noël Vallée,Nicolas Termoz,Malek Abidi,Alexandre Vallée,Giovanni De Marco

doi:10.1038/s41598-022-06471-6

Abstract

To assess the usefulness of a theoretical postural instability discrimination index (PIth) in amyotrophic lateral sclerosis (ALS). Prospective regression analyzes were performed to identify the biomechanical determinants of postural instability unrelated to lower limb motor deficits from gait initiation factors. PIth was constructed using a logit function of biomechanical determinants. Discriminatory performance and performance differences were tested. Backward displacement of the pression center (APAamplitude) and active vertical braking of the mass center (Braking-index) were the biomechanical determinants of postural instability. PIth = − 0.13 × APAamplitude − 0.12 × Braking-index + 5.67, (P < 0.0001, RSquare = 0.6119). OR (APAamplitude) and OR (Braking-index) were 0.878 and 0.887, respectively, i.e., for a decrease of 10 mm in APAamplitude or 10% in Braking-index, the postural instability risk was 11.391 or 11.274 times higher, respectively. PIth had the highest discriminatory performance (AUC 0.953) with a decision threshold value ge 0.587, a sensitivity of 90.91%, and a specificity of 83.87%, significantly increasing the sensitivity by 11.11%. PIth, as objective clinical integrator of gait initiation biomechanical processes significantly involved in dynamic postural control, was a reliable and performing discrimination index of postural instability with a significant increased sensitivity, and may be useful for a personalized approach to postural instability in ALS.

Highlights

anticipatory postural adjustment (APA) result in a backward shift in the center of pressure (CoP)[19] toward the swing leg side, which allows the propelling of the center of mass (CoM) toward the stance leg side prior to the swing heel-off[21,22]
APAs create the conditions which act to propel the CoM forward contributing to body forward progression to reach the intended gait speed at the first step e nd[19,23], and the optimal conditions needed to maintain the stability of the whole body during step execution[24–26]
The decrease in APAamplitude was significantly associated with a decrease in step length (L) and CoM forward progression velocity (Vm) (P = 0.0041 and < 0.0001, respectively)

Summary

Introduction

Predominance, as reported by our team[5,11] and o thers[10,12,13]. Extrapyramidal stiffness is correlated with postural and balance disorders in ALS patients[5]. Gait initiation is an interesting pattern to investigate dynamic postural instability related to different neurological disorders such as ALS. It is the motor transition from standing position to walking. Clustering is a multivariate technique of grouping individuals sharing similar values across several variables in which the data is usually not scattered evenly through n-dimensional space but instead forms clusters. To assess the intermethod reliability between the pull test and clustering of subjects, across the gait initiation and postural instability variables, in order to highlight clusters of data in relation to postural instability

Objectives

Methods

Results

Discussion

Conclusion