# How do ankle passive intersegmental moments of spastic adults differ from normative curves?

Simon Hinnekens, Sacha Guitteny, Alexandre Naaïm, Raphael Dumas,
Sébastien Mateo, Yoann Lafon

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Simon Hinnekens, Sacha Guitteny, Alexandre Naaïm, Raphael Dumas, Sébastien Mateo, et al.. How do ankle passive intersegmental moments of spastic adults differ from normative curves?. Multidisciplinary Biomechanics Journal, 2025, 50th congress of the.., 10.46298/mbj.16218 . hal-05191772v2

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Submitted on 23 Oct 2025

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# How do ankle passive intersegmental moments of spastic adults differ from normative curves?

Simon Hinnekens<sup>a*</sup>, Sacha Guitteny<sup>a</sup>, Alexandre Naaïm<sup>a</sup>, Raphaël Dumas<sup>a</sup>, Sébastien Mateo<sup>b, c</sup>, Yoann Lafon<sup>a</sup>

a Univ Eiffel, Univ Lyon 1, LBMC UMR T_9406, F-69622 Lyon, France

b Hospices Civils de Lyon, Hôpital Henry Gabrielle, Plateforme Mouvement et handicap, F-69230 Saint Genis Laval

c Univ Lyon 1, CNRL Equipe Trajectoires UMR 1028, F-69500 Bron, France

* Corresponding author: simon.hinnekens@univ-lyon1.fr

Received date: 04/04/2025

Accepted date: 27/06/2025

Publication date: 27/10/2025

**Keywords:** spasticity, reflex activity, passive moments, lower limb, literature models

© 2025 The Authors

Licence CC-BY 4.0

Published by Société de Biomécanique

## 1. Introduction

For gait analysis, biomechanical parameters of patients are widely compared to reference values or ranges of values from literature (Schwartz & Rozumalski, 2008), i.e. normative curves. In parallel to gait analysis, biomechanical parameters are increasingly assessed during passive joint mobilizations for spastic patients (Bar-On et al. 2013). The spasticity of a muscle can be assessed by physiotherapists using the Modified Ashworth scale (MAS score). However, its inter-operator reliability is moderate for the lower limb (Ansari et al. 2008). To limit this variability related to the operator's estimation, passive intersegmental moments computed from motion capture and dynamometer data could be relevant as objective biomechanical parameters to characterize spasticity. However, conversely to gait analysis, the comparison of these biomechanical parameters to reference values is not common.

The objective of the study is to analyze the passive intersegmental moments for different MAS scores for the ankle compared to normative curves from the literature.

## 2. Methods

### 2.1 Subjects

Data presented in this study were selected from a database of 15 patients with lower limb spasticity. The tibialis anterior, triceps, soleus, quadriceps and hamstring muscle groups were assessed by at least one physiotherapist.

To avoid confounding factors, this study only presented data from the assessment of only one experienced physiotherapist (15 years of regular spasticity assessment). The study focused on the ankle joint and extracted the MAS score of the triceps muscle from 4 typical patients with spasticity of 0, 1, 1+ and 3, respectively. Their features are summarized in Table 1.

<table><caption>Table 1. Features of the patients.</caption><thead><tr><td>MAS score</td><td>Height (m)</td><td>Mass (kg)</td><td>Sex</td><td>Pathology</td></tr></thead><tbody><tr><td>0</td><td>1.75</td><td>57.0</td><td>M</td><td>Tetraplegia</td></tr><tr><td>1</td><td>1.77</td><td>63.0</td><td>M</td><td>Hemiplegia</td></tr><tr><td>1+</td><td>1.61</td><td>49.3</td><td>M</td><td>Stroke</td></tr><tr><td>3</td><td>1.80</td><td>79.0</td><td>M</td><td>Encephalopathy</td></tr></tbody></table>

Credit: Hinnekens.

### 2.2 Apparatus

A 6-axis dynamometer (Sensix, Poitiers, France) was used to measure forces and moments applied by the physiotherapist. Each patient was equipped with 17 reflective markers. Kinematics was recorded using ten optoelectronic cameras (Qualisys Miqu M3 300 Hz), and processed with Qualisys Track Manager to compute patient's joint angles and velocities by inverse kinematics. Passive intersegmental moments were computed by
inverse dynamics. Electromyography (Delsys) was used
to record muscle activity and to determine the EMG
onset of the involuntarily muscle contraction (Arami
et al. 2017).

## 2.3 Normative curves

The reference behavior for the joint ankle was built
from two sets of equations of passive intersegmental
moments (denoted M1 and M2) established on healthy
participants, and adapted to the joint coordinate sys-
tems standards of the ISB by Gasparutto et al. (2018).
The flexion-extension knee angle was set to 0 for both
models, and the inversion-eversion ankle angle was also
set to 0 for the M2 model to build normative curves as
function of ankle plantar-dorsi flexion.

In this first exploratory study, the comparison between
experimental and normative curves is limited to a qual-
itative description of differences.

## 3. Results and discussion

Regarding passive intersegmental moments as functions
of ankle plantar-dorsi flexion (Fig. 1), none of spastic
patients were close to the normative curves, even if
the patterns were similar. Resistive (negative) passive
intersegmental moments of spastic patients were of
greater magnitude than the ones of the normative
curves. Besides, for these patients with spasticity, it was
not possible to reach ankle angles greater than 0°, value
at which M1 and M2 models differ more distinctively
(in a same way as they differ for angles lower than -50°).

The MAS3 patient stood out by showing greater
passive intersegmental moments and a smaller ankle
dorsiflexion at the end of the motion, as well as an
epileptoid tremor of the foot (visible in Fig. 1) caused
by the rapid contraction of the triceps.

MAS0 and MAS1 patients showed similar moment-an-
gle curves. The MAS1+ patient had the smallest passive
intersegmental moment magnitude of all the spastic
patients.

It was expected that the passive intersegmental
moments of patients with spasticity would approach
the normative curves as the MAS score decreased.
Thus, the curve pattern for MAS0, 1 and 1+ was close
to the literature models M1 and M2 but shifted towards
more resistive moments. Also, it was not surprising to
have similar curves for MAS0 and MAS1, as the last
describes a slight increase in muscle tone at the very
end of the range of motion. If the MAS1+ curve was

<figure><img src="image_2.png" /><figcaption>**Figure 1.** Normative curves and ankle passive intersegmental moment for different MAS scores. PF=plantarflexion, DF=dorsiflexion.</figcaption></figure>

Credit: Hinnekens.

expected to be similar to the MAS0 and MAS1 ones,
with moments of greater magnitude when the angle
reached -10°, it was not the case in this study.

It must be noted that spasticity is assessed from rapid
joint mobilization. Therefore, models M1 and M2 are
not fully representative as the viscous term is missing.

## 4. Conclusions

To the best of the author's knowledge, this study was
the first to assess how ankle passive intersegmental
moments of spastic adults differ from normative curves.
Moment-angle spastic patterns were expected to differ from literature models established for healthy subjects. Both models M1 and M2 agree with each other between -50° and 0°. Patients' ankle joints were mobilized in this range of motion. However, the distribution of the curves did not fully match the order of the MAS scores. These results highlight the variability between the MAS score and the biomechanical parameters, possibly due to the moderate inter-operator reliability of the MAS score for the lower limb. Gathering data from more patients might improve the present analysis.

## Acknowledgements

The authors would like to thank the ANR (French National Research Agency) for funding the HASPA project (ANR-22-CE33-0016).

## Conflict of Interest Statement

None.

## Contributor Roles

Conceptualization and Writing-review & editing for all the authors. SH: Data curation, Formal analysis, Software, Visualization, Writing-original draft; SG: Data curation, Investigation, Methodology, Software; AN: Methodology, Resources; RD: Software; SM: Investigation; YL: Funding acquisition, Project administration.

## References

Ansari, N. N., Naghdi, S., Arab, T. K., & Jalaie, S. (2008). The interrater and intrarater reliability of the Modified Ashworth Scale in the assessment of muscle spasticity: limb and muscle group effect. *NeuroRehabilitation, 23*(3), 231-237. https://doi.org/10.3233/NRE-2008-23304

Arami, A., Tagliamonte, N. L., Tamburella, F., Huang, H. Y., Molinari, M., & Burdet, E. (2017, July). A simple tool to measure spasticity in spinal cord injury subjects. In *2017 International Conference on Rehabilitation Robotics (ICORR)* (pp. 1590-1596). London, UK. https://doi.org/10.1109/ICORR.2017.8009475

Bar-On, L., Aertbeliën, E., Molenaers, G., Bruyninckx, H., Monari, D., Jaspers, E., Cazaerck, A., & Desloovere, K. (2013). Comprehensive quantification of the spastic catch in children with cerebral palsy. *Research in Developmental Disabilities, 34*(1), 386-396. https://doi.org/10.1016/j.ridd.2012.08.019

Gasparutto, X., Jacquelin, E., & Dumas, R. (2018). Contribution of passive actions to the lower limb joint moments and powers during gait: A comparison of models. *Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 232*(8), 768-778. https://doi.org/10.1177/0954411918785661

Schwartz, M. H., & Rozumalski, A. (2008). The Gait Deviation Index: a new comprehensive index of gait pathology. *Gait & posture, 28*(3), 351-357. https://doi.org/10.1016/j.gaitpost.2008.05.001