[Biomechanical finite element analysis of American Chiropractic intervention on the third lumbar transverse process...

To explore the displacement and pressure distribution of American Chiropractic in a model of third lumbar syndrome based on finite element analysis.

On March 2021, CT and MRI images of a 23-year-old male patient with right third lumbar syndrome were selected. A 3D stl model was established using Mimics and CATIA, and the data was imported into Hypermesh, Abaqus & ANSYS. The elastic modulus and Poisson's ratio of the affected side material were adjusted to establish its finite element model. Based on the comparison of the operating positions and routines of the American Chiropractic and the lumbar spine oblique pull method, but with differences in the focus and direction of force, the experimental group simulated the American Chiropractic with the healthy side (left side) lying position of the model. The upper endplate of L₃ and the lower part below L₃ twisted accordingly with the body position, we applied a vertical forward thrust of 246 N to the plane formed by the L₄, L₅ spinous processes and L₄ upper articular processes;The control group simulates the oblique pull method of the lumbar spine, requiring the model to lie on the healthy side (left side), fix the upper endplate of L₄, and perform a horizontal rotation along the longitudinal axis of L₃ vertebral body. At this time, the contact force in the upward direction is also set to 246 N. Compare the displacement and stress differences between the L₁-L₅ intervertebral bodies, intervertebral discs, articular processes, and transverse process muscles in two intervention models.

① Under safe load conditions, a test force of 246 N was applied to the model, and the maximum vertebral displacement occurred on the right side of the L₃ vertebral body (1.197 mm) after manual intervention in the control group. The vertebral displacement between L₁-L₅ induced by manual intervention in the experimental group was smaller than that of the control group's manual intervention (P<0.05). ② The maximum vertebral body stress occurred on the right side of the L₃ vertebral body after manual intervention in the control group (98.425 MPa). The stress on each vertebral body formed by the experimental group's manual intervention was lower than that of the control group's manual intervention (P<0.05). ③The maximum intervertebral disc stress occurred on the right side of the L_2,3 intervertebral disc (6.282 MPa) after manual intervention in the control group. ④ The maximum joint process stress occurred on the right side of the L₄ upper joint process after manual intervention in the experimental group (1.587 MPa). The joint process stress on the left side below L₁ and the left side above and below L₂ induced by manual intervention in the experimental group was lower than that of the control group (P<0.05). ⑤The maximum stress on the intertransverse process muscle was observed at the right lateral L₃ process end (31.960 MPa) of L_3,4 in the control group after manual intervention. The stress on the L_2,3 and L_4,5 segments of the intertransverse process muscle induced by manual intervention in the experimental group was lower than that of the control group's manual intervention (P<0.05).

The mechanical feedback of the L₁-L₅ vertebral body, the lower left side of the articular process L₁, the upper and lower left side of the articular process L₂, and the L_2,3 and L_4,5 segments of the transverse process muscle in the model indicates that performing American Chiropractic for the treatment of third lumbar transverse process syndrome can accurately hit the target pain point and allow the patient's tissue to form a low stress and low tension state after manual operation, thereby reducing the possibility of tissue damage caused by hypertonia after intervertebral joint movement, making it relatively safe. The application of American Chiropractic will be a new supplement to the traditional treatment plan for third lumbar transverse process syndrome.