Dynamic compensation in spinopelvic alignment and its relation to symptom severity in patients with lumbar spinal...

Patients with symptomatic lumbar spinal stenosis (sLSS) often experience more pain when standing and walking than when sitting or lying, suggesting a functional link between symptoms and spinopelvic alignment. However, standing radiography, which is the current standard for assessing alignment, only captures static parameters and does not account for dynamic compensatory mechanisms during movement. To address this limitation, a method was developed to transfer static radiological parameters into dynamic motion analysis and investigate changes in posture between stance and gait using the concept of dynamic compensation.

First, this study aimed to investigate associations between spinopelvic alignment parameters in stance and their respective dynamic compensation. Secondly, this study aimed to assess the associations between spinopelvic alignment parameters in stance, gait, dynamic compensation and symptom severity. Finally, the incidence of segmental instability was determined, and potential effects on the association between spinopelvic alignment in stance, dynamic compensation and symptom severity were explored.

Cross-sectional single center observational study.

Patients with sLSS scheduled for decompression surgery.

Self-report measures: Oswestry disability index (ODI) total score, Swiss spinal stenosis questionnaire function/symptom sub score, core outcome measure index score, EQ-5D index, Tampa scale of kinesiophobia score, numeric pain ratings at rest and daily activities. Physiologic measures: radiologic spinopelvic alignment assessed using EOS radiography; severity of central canal stenosis (Schizas) and foraminal stenosis (Lee) rated using magnetic resonance imaging. Functional measures: static and dynamic spinopelvic alignment derived from offset-corrected motion-capture marker data.

All patients underwent EOS radiography, magnetic resonance imaging and motion analysis and completed the patient-reported outcome questionnaires. T9 inclination, pelvic tilt, sacral slope, spine inclination and spinosacral angle derived from marker-based motion capture were offset-corrected using EOS radiography to reflect the true anatomical spinopelvic alignment. The dynamic compensation of a given parameter was defined as the difference between the average angle over 6 left gait cycles and the angle during stance. Relationships between spinopelvic alignment in stance, average during gait, range of motion, dynamic compensation and symptom severity were assessed using Spearman's rho (ρ) and ρ adjusted for age and body mass index (BMI, ρ adj.).

A total of 119 patients with sLSS (59M/60F; median age 72 years [interquartile range (IQR) 65-78]; median BMI 26.5 kg/m² [IQR 24-30]) were included in this study. Significant weak to moderate relationships between static and dynamically compensated alignment parameters were found for T9 inclination (ρ adj. = -0.49, p < 0.001), pelvic tilt (ρ adj. = -0.25, p = 0.007) and spine inclination (ρ adj. = -0.38, p < 0.001). There were no correlations between ODI and the absolute values of alignment parameters during stance or gait. However, weak but significant positive and negative relationships between dynamic compensation and ODI were found for pelvic tilt (ρ adj. = 0.19, p= 0.044) and spinosacral angle (ρ adj. = -0.20, p = 0.034), respectively.

The results of this study showed that dynamic compensation in spinopelvic alignment in patients with sLSS is moderated by the alignment during stance. While none of the parameters during stance or gait showed associations with patient-reported outcome, dynamic compensation involving the pelvis was associated with symptom severity. Notably, patients with more pelvic retroversion in gait compared to stance had greater disability. Overall, the findings of this study highlight the high clinical relevance of the pelvic region in patients with sLSS and illustrate the value of dynamic compensation as an objective method capable of linking kinematic information to patient-reported outcome measures.