Spine Journal - 2026-09-01 - Journal Article; Observational Study
The impact of structural damage and muscle properties on spinal mobility in axial spondyloarthritis: a sensor-based analysis from the Córdoba Axial Spondyloarthritis Task Force Registry and Outcomes registry.
Moldovan DMM, Aranda-Valera IC, Ladehesa-Pineda L, Ábalos-Aguilera MDC, Puche-Larrubia MÁ, Escudero-Contreras A, González-Navas C, Garrido-Castro JL, Fodor D, Collantes-Estévez E, López-Medina C
Topics
Key Takeaway
In 98 axSpA patients, mSASSS structural damage and paraspinal muscle stiffness/elasticity were independently associated with reduced spinal mobility, with the strongest effects observed in the cervical spine.
Summary Depth
Choose how much analysis to show on this article page.
Summary
This cross-sectional study from the CASTRO registry evaluated whether structural damage (mSASSS) and paraspinal muscle mechanical properties independently predict cervical and lumbar mobility in 98 ASAS-criteria axSpA patients. Inertial measurement units quantified 3-plane range of motion; MyotonPRO quantified muscle stiffness and elasticity. Adjusted generalized linear models and Gradient Boosting Machine models with SHAP values both identified mSASSS, stiffness, and reduced elasticity (higher logarithmic decrement) as top independent predictors of mobility loss, most prominently in the cervical spine.
Key Limitation
Cross-sectional design prevents establishing whether increased paraspinal muscle stiffness is a cause or consequence of reduced mobility and structural damage, making causal inference impossible.
Original Abstract
BACKGROUND CONTEXT
The loss of spinal mobility remains one of the most debilitating consequences of axial spondyloarthritis (axSpA). Despite therapeutic advancements, many patients still have limited mobility. Structural damage is a recognized contributor, but the role of paraspinal muscle properties in determining spinal mobility is less studied.
PURPOSE
To evaluate the relative contribution of structural damage and paraspinal muscle mechanical properties to cervical and lumbar spinal mobility in axSpA patients.
STUDY DESIGN/SETTING
Cross-sectional observational study.
PATIENT SAMPLE
A total of 98 axSpA patients from the Córdoba axSpA Task Force Registry and Outcomes (CASTRO) who met ASAS criteria.
OUTCOME MEASURES
Cervical and lumbar range of motion; paraspinal muscle stiffness and elasticity parameters.
METHODS
Spinal mobility in the cervical and lumbar regions was measured in 3 planes using inertial measurement units. Paraspinal muscle stiffness and muscle elasticity (logarithmic decrement) were quantified with the MyotonPRO device. Structural damage was assessed with the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS). Associations between structural damage, muscle properties, and mobility were explored using generalized linear models adjusted for age, sex, body mass index, and C-reactive protein. A sensitivity exploratory analysis was conducted using Gradient Boosting Machine models.
RESULTS
Structural damage, as quantified by mSASSS, was significantly associated with impaired spinal mobility. In adjusted generalized linear models, both structural damage and paraspinal muscle properties, including muscle stiffness and reduced elasticity (higher decrement), were independently associated with decreased range of motion, most notably in the cervical spine. Gradient Boosting Machine models supported these findings, with Shapley additive explanations values consistently identifying mSASSS, stiffness, and elasticity among the top predictors of mobility outcomes.
CONCLUSIONS
Structural damage and paraspinal muscle properties were independently associated with reduced spinal mobility in axSpA. Digital tools such as inertial measurement units and MyotonPRO may support objective functional assessment and targeted rehabilitation strategies. However, the cross-sectional design limits conclusions regarding temporal relationships.