Full-body Postural Alignment Analysis Through Barycentremetry

Abstract

Study Design. A multicentric retrospective study. Objective. The study of center of mass (COM) locations (ie, barycentremetry) can help us understand postural alignment. The goal of this study was to determine relationships between COM locations and global postural alignment x-ray parameters in healthy subjects. The second objective was to determine the impact on the spinopelvic alignment of increased distance between the anterior body envelope and spine at the lumbar apex level. Summary of Background Data. Unexplored relationship between COM location and spinopelvic parameters. Methods. This study included healthy volunteers with full-body biplanar radiographs, including body envelope reconstruction, allowing the estimation of COM location. The following parameters were analyzed: lumbar lordosis (LL), thoracic kyphosis (TK), cervical lordosis (CL), pelvic tilt (PT), sacro-femoral angle (SFA), knee flexion angle (KFA), and sagittal odontoid-hip axis angle (ODHA). The following COM in the sagittal plane were located: whole body, at a thoracolumbar inflection point, and body segment above TK apex. The body envelope reconstruction also provided the distance between the anterior skin and the LL apex vertebral body center (“SV-L distance”). Results. This study included 124 volunteers, with a mean age of 44±19.3. Multivariate analysis confirmed the posterior translation of COM above TK apex with increasing LL (P=0.002) through its proximal component and posterior shift of COM at the inflection point with increasing TK (P=0.008). Increased SV-L distance was associated with greater ODHA (r=0.4) and more anterior body COM (r=0.5), caused by increased TK (r=0.2) and decreased proximal and distal LL (both r=0.3), resulting in an augmentation in SFA (r=0.3) (all P<0.01). Conclusions. Barycentremetry showed that greater LL was associated with a posterior shift of COM above the thoracic apex, while greater TK was correlated with more posterior COM at inflection point. Whole-body COM was strongly correlated with ODHA. This study also exhibited significant alignment disruption associated with increased abdominal volume, with compensatory hip extension. Level of Evidence. Level—II.