Altered cervical intervertebral motion in chronic neck pain: evidence from biplane videoradiography

Chronic neck pain is prevalent and disabling, and routine examinations offer limited insight into vertebral-level motion abnormalities. This study aimed to quantify intervertebral cervical kinematics in chronic neck pain using biplane videoradiography and to compare them with asymptomatic controls. Twenty-three adults (13 with chronic neck pain, 10 controls) completed three trials of flexion-extension, lateral bending, and axial rotation while seated in a custom biplane videoradiography system integrated with optical motion capture. Vertebral kinematics from C4-C7 were derived from computed-tomography-based models using semi-automated shape-matching. Nonparametric bootstrapping produced 90% confidence intervals for total range of motion, the percent contribution to global head-to-torso motion, and trial-to-trial variability. Compared with controls, participants with chronic neck pain showed reduced axial-rotation motion and contribution at C5-6 with increased contribution of head motion relative to C4. During flexion-extension, there was a greater contribution from C4-5 and greater trial-to-trial variability in the percent contribution of head-relative-to-C4. No group differences were observed for lateral bending. These findings identified localized deficits at C5-6 and altered motion distribution at other levels, suggesting segment-specific biomechanical changes with compensatory mobility in chronic neck pain. Intervertebral kinematic analysis may improve biomechanical assessment and inform individualized management strategies.