Abstract: BACKGROUND: Long’s traction orthopedic method has demonstrated clear clinical efficacy in cervical spondylotic radiculopathy and is widely applied; however, its biomechanical mechanism of action has not been clearly reported. 
OBJECTIVE: To explore the biomechanical basis for how Long’s traction orthopedic method improves cervical intervertebral foramen deformation using three-dimensional finite element analysis. 
METHODS: Based on a previously developed and validated finite element model coupling the musculoskeletal system of the head and neck, the model was imported into LS-DYNA software to simulate classical cervical traction and three manipulative techniques of Long’s traction orthopedic method: the pushing technique, the pulling technique, and the shaking technique. C5 was designated as the target segment, with relevant boundary conditions set under a traction force of 200 N. Forward and downward leftward pulling forces, as well as left axial rotation torque, were sequentially applied to simulate the techniques. The relative displacement, angle, and lateral bending displacement of the cervical intervertebral foramen, direction of intervertebral disc displacement, and strain were recorded and analyzed. 
RESULTS AND CONCLUSION: (1) The pushing technique produced the most significant effect on the relative displacement of the intervertebral foramen, with C5 displacement reaching up to 15.6 mm, resulting in an increased intervertebral foramen volume. Additionally, relative angle changes in the foramen were more pronounced, with a peak value of 22.9°. (2) In terms of relative displacement during lateral bending of the overall segment, the shaking technique was 2.4 times more effective than the pulling technique, while pushing technique and classical cervical traction showed minimal changes in lateral bending displacement. (3) In all orthopedic method, the direction of intervertebral disc displacement showed a forward tendency, with Y-axis displacements of 11.56 mm (pushing), 9.94 mm (pulling), and 7.73 mm (shaking), respectively. (4) The orthopedic method induced forward sliding strain in the intervertebral disc, which released the compressed intervertebral foramen volume in the posterior segments. (5) In comparison, classical cervical traction was less effective in achieving these changes and could not reach the same degree of alteration. (6) Therefore, Long’s traction orthopedic method is more effective than classical cervical traction in increasing the cervical intervertebral foramen gap and improving foramen deformation. Biomechanically, this is attributed to the increased relative displacement, angle, and lateral bending displacement of the cervical intervertebral foramen, as well as greater disc displacement and forward strain, thereby relieving nerve compression in the affected segments, alleviating symptoms, and achieving a positive therapeutic effect.

Key words: Long’s traction orthopedic method, cervical spondylotic radiculopathy, intervertebral foramen volume, finite element analysis, biomechanics, relative displacement, relative angle, intervertebral disc strain