Introduction: Postural balance assessment may help diagnosis, planification and follow up in cases of spine disorders. This paper explores the interest of quantifying postural balance in clinical routine, using 3D reconstruction from biplanar X‐ray device in combination with a force plate.
Methods: 82 patients were enrolled consecutively, divided into three groups (Scoliosis, Kyphosis and Other) and compared with 22 asymptomatic subjects. Head to knee X‐rays were taken while the subject was on a force plate in free standing position. Head position was controlled using a mirror at eyes' level. Merging of the gravity line (GL) with 3D reconstruction yielded the relative position of the center of acoustic meati (CAM) and T1 vertebral body. The inclination of the axis linking the CAM to the hip axis center (HAC) on the sagittal plane was also calculated. Pearson correlation coefficient between the postero‐anterior offset of the CAM to GL and the sagittal inclination was calculated for each group.
Results: Observing the position of the CAM with respect to the gravity line highlighted different pattern according to several kind of pathology. The distance of CAM to GL was inferior to 40mm by asymptomatics while it could reach respectively 90mm and 130mm by scoliotic and hyperkyphotic patients. The mean distance from T1 to GL is similar in the ‘Asymptomatic’, ‘Scoliosis’ and ‘Other’ groups with 25±15mm. The sagittal CAM‐HAC inclination is correlated with the position of the CAM in all pathological groups (‘Scoliosis’‐r=0.90, ‘Kyphosis’‐r=0.81 and ‘Other’‐r=0.80) but not by ‘Asymptomatic’ (r=0.51).
Conclusion: Transversal distance from CAM to GL has never been assessed in free standing position but highlights more postural trouble than the distance from T1 to GL. The correlation between the sagittal CAM‐HAC inclination and the CAM‐GL sagittal offset by patients may allow a similar analysis without force plate. Observing postural balance in 3D with respect to the gravity provides clinically relevant information and may help better understand the mechanisms related to specific pathologies. Either CAM position with respect to the gravity line or CAM‐HAC inclination could help in assessment of postural balance.