Static and dynamic stabilometric force platform study of spinopelvic anterior sagittal imbalance

Abstract

Background data: Anterior sagittal imbalance (ASI) is a severity factor in spinal pathology. Stabilometric study of the dynamic position of the center of pressure (CoP) assesses orthostatic control. These analyses provide the energy expenditure used for this control.

Hypothesis: Stabilometric signs are associated with ASI indicate increased energy expenditure.

Patients and methods: Healthy male volunteers were subjected to reversible ASI induced by wearing a kyphotic thermoformed thoracolumbar corset. The deformation was assessed by C7 tilt on EOS whole-spine views. Static and dynamic posturographic force platform study was performed under conditions of anteroposterior and mediolateral instability. Mean CoP position (X_mean, Y_mean) was studied on statokinesigram, with scatter assessed as confidence ellipse (CE). Path length according to CE surface (LAS) indicated energy expenditure. The stabilogram quantified displacement over time as lengths (L_x, L_y) and amplitudes (A_x, A_y).

Results: The corset significantly increased C7 tilt (p<0.0001). This did not significantly change mean CoP positions (X_mean and Y_mean), but LAS was significantly increased (p=0.003). Static tests showed changes in L_y (p=0.0008) and A_x (p=0.003), and dynamic tests showed changes in L_y (p<0.0001), L_x (p<0.0001), A_x (p<0.0001), A_y (p<0.05) and CE (p<0.004).

Discussion: Posturographic parameters were impacted by inducing ASI in healthy subjects. Significant differences were seen in stabilography, CE and LAS, were greater on dynamic testing, and correlated with radiologic sagittal balance. Force platforms can reveal increased energy expenditure in maintaining posture.

Level of evidence: II; Single-center prospective study involving healthy volunteers.

Keywords: Center of pressure; Force platforms; Posturography; Spinal sagittal alignment; Stabilogram.