Head-trunk kinematics during high-velocity-low-amplitude manipulation of the cervical spine in asymptomatic subjects: helical axis computation and anatomic motion modeling.

Objective: This study aimed to analyze the in vivo 3-dimensional kinematics of the head during cervical manipulation including helical axis (HA) computation and anatomic motion representation.

Methods: Twelve asymptomatic volunteers were included in this study. An osteopathic practitioner performed 1 to 3 manipulations (high-velocity and low-amplitude [HVLA] multiple component technique) of the cervical spine (between C2 and C5) with the patient in the sitting position. During manipulation, head motion was collected using an optoelectronic system and expressed relative to the thorax. Motion data were processed to analyze primary and coupled motions and HA parameters. Anatomic motion representation including HA was obtained.

Results: During manipulation, average maximal range of motion was 39° (SD, 6°), 21° (SD, 7°), and 8° (SD, 5°) for lateral bending (LB), axial rotation (AR), and flexion extension, respectively. For the impulse period, magnitude averaged of 8° (SD, 2°), 5° (SD, 2°), and 3° (SD, 2°), for LB, AR, and flexion extension, respectively. Mean impulse velocity was 139°/s (SD, 39°/s). Concerning AR/LB ratios, an average of 0.6 (SD, 0.3) was observed for global motion, premanipulation positioning, and impulse. Mean HA was mostly located ipsilateral to the impulse side and displayed an oblique orientation.

Conclusion: This study demonstrated limited range of AR during cervical spine manipulation and provided new perspectives for the development of visualization tools, which might be helpful for practitioners and for the analysis of cervical manipulation using HA computation and anatomic representation of motion.