Abstract: BACKGROUND: The oblique pulling manipulation has good therapeutic effects on cervical spondylosis, but its biomechanical mechanism of action on intervertebral discs with different degrees of degeneration is not clear.
OBJECTIVE: To explore the biomechanical mechanism of the oblique pulling manipulation on the discs with different degrees of degeneration through three-dimensional finite element model.
METHODS: The motion capture system was used to measure the kinematic parameters of the key steps during the oblique pulling manipulation, and a three-dimensional finite element model of the whole cervical spine of the C5/6 mildly, moderately, and severely degenerated intervertebral discs was established. The kinematic parameters were converted into moments and loaded onto the whole cervical spine of the mildly, moderately, and severely degenerated intervertebral discs in a step-by-step manner, so as to obtain the biomechanical parameters of the stress-strain of each structure during the simulated oblique pulling manipulation. 
RESULTS AND CONCLUSION: (1) In the simulation of the oblique pulling manipulation to the right side, with the increase of disc degeneration, the Von-Mise stress of the annulus fibrosus gradually increased, and the stress was concentrated on the right outer side of the annulus fibrosus. The stress of the nucleus pulposus decreased and the stress was concentrated at the junction of the nucleus pulposus and the annulus fibrosus. The overall displacement of the intervertebral disc decreased; the stress of the left facet joints decreased; the Von-Mise stress of the spinal cord increased, and the stress of the spinal cord was concentrated in the upper cervical spine. (2) In the simulation of the oblique pulling manipulation to the right side, with the increase of disc degeneration, the overall strain of the C5/6 segment disc, the pressure inside the nucleus pulposus, and the stress of the left nerve root decreased; the disc shear force increased; the relative distance between the left nerve root and the disc increased, and the relative distance between the right nerve root and the disc did not change significantly. (3) These results indicate that the cervical oblique-pulling manipulation improves biomechanical imbalances in mild-to-moderately degenerated intervertebral discs by modulating facet joint stress and increasing the distance between nerve roots and intervertebral discs. However, its application in severely degenerated discs requires caution due to a sharp rise in annulus fibrosus stress and potential spinal cord compression risks.

Key words: oblique pulling manipulation, radiculopathy, intervertebral disc degeneration degree, finite element analysis, motion capture, biomechanics