Effects of Parameter Combinations in Cervical Rotation-Traction Manipulation on Intervertebral Foramen Opening and Biomechanical Responses: A Finite Element Study.

BACKGROUND

To investigate, using a finite element model, the effects of different combinations of rotation, flexion, and re-rotation parameters in cervical rotation-traction manipulation (CRTM) on intervertebral foramen opening and biomechanical distribution, and to provide a basis for segment-specific parameter optimization.

METHODS

A validated C2-T1 finite element model, derived from CT images of a healthy adult male volunteer, simulated CRTM by sequentially applying rotation, flexion, re-rotation, and upward traction. Rotation angles: 60°, 65°, 70°, 75°; flexion: 20°, 30°, 40°; re-rotation: 5°, 10°, 15°, with rotation+re-rotation sum ≤80°, yielding 27 combinations. Vertical diameter changes at C3/4-C7/T1 were measured, and stresses in vertebrae, discs, and facet cartilage were analyzed via stress cloud maps.

RESULTS

Foraminal opening showed segment-specific characteristics; increased flexion promoted opening, with flexion 40°being most effective. Optimal combinations were: C3/4 with axial rotation of 70°, re-rotation of 10°, and flexion of 40° (AR70-10_FL40); C4/5 with AR65-15_FL40; C5/6 with AR60-15_FL40; and C6/7 and C7/T1 with AR60-10_FL40. Peak vertebral stress generally corresponded to the segments showing maximal foraminal opening. Stress trends in the vertebral bodies, discs, and facet articular cartilage were consistent, following the order AR60-10_FL40 < AR65-15_FL40 < AR60-15_FL40 < AR70-10_FL40. High-stress regions were mainly located in the upper and middle cervical spine, with differences reflected primarily in stress magnitude rather than stress location.

CONCLUSION

CRTM effects appear parameter-dependent and segment-specific. Flexion may be key in promoting opening, with segment-specific responses to rotation/re-rotation. Parameter adjustments affect both opening and stress distribution, suggesting segmental controllability. However, as these findings derive solely from a finite element model, they are preliminary biomechanical evidence, not directly applicable clinically. Further clinical and cadaveric studies are warranted.