Trajectory-based analysis of spinal kinematics during forward bending in non-specific chronic low back pain subgroups: A smartphone 2D video tracking

BackgroundSimple range of motion measurements in individuals with non-specific chronic low back pain (NSCLBP) during forward bending provide limited information about the directional characteristics of spinal movements.PurposeTo examine the horizontal and vertical displacement trajectories of thoracolumbar regions (T12 and L2 levels) during forward bending using smartphone-based 2-dimensional video analysis, and to compare kinematics among NSCLBP subgroups classified as the flexion pattern (FP) and extension pattern (EP), and healthy controls.MethodsA total of 185 participants were recruited (58 healthy, 87 FP, 40 EP). Two markers were positioned over the spinous processes of T12 and L2. Marker trajectories were tracked using Kinovea software, and displacements along the <i>x</i>- (anterior-posterior) and <i>y</i>-axes (superior-inferior) were measured.ResultsThe EP group showed significantly greater anterior displacement at the T12 and L2 levels than the FP group, and at the L2 level than healthy controls. No significant differences were found between FP and healthy groups or in vertical displacement of the two markers.ConclusionsHorizontal displacement trajectories effectively differentiated NSCLBP subgroups, particularly identifying a distinct movement strategy in the EP group. Smartphone-based video analysis may offer a clinically useful and accessible tool for subgroup-specific assessment.