A Finite Element Analysis of Sacroiliac Joint Displacements and Ligament Strains in Response to Three Manipulations

Background: Clinical studies have found that manipulations have a good clinical effect on sacroiliac joint (SIJ) pain without specific causes. However, the specific mechanisms of manipulations are still unclear. The purpose of this study was to investigate the effects of three common manipulations on the pressures and displacements of SIJ, and the strains of the surrounding ligaments. Methods: : A three-dimensional finite element model of the pelvis-femur was developed. The manipulation of hip and knee flexion (MHKF), the manipulation of oblique pulling (MOP), and the manipulation of lower limb hyperextension (MLLH) were simulated. The pressures and displacements of SIJs, and the strains of the surrounding ligaments were analyzed under the three manipulations. Results: : The MOP produced the greatest pressure on the left SIJ, at 6.6 MPa, while the MHKF could produce the lowest pressure on the right SIJ, at 1.5 MPa. The displacements of SIJs were all less than 1mm in the three manipulations. The three manipulations could cause different degrees of the strains of ligaments around the SIJs, and the MOP could produce the largest strain of ligaments. Conclusion: The three manipulations all produced small displacements of SIJs, while they caused different degrees of ligament strains, which might be the reason for relieving the SIJ pain. The MOP may be a more effective manual therapy. Key words: Manipulation, Sacroiliac joint, Displacement, Ligament strain, Finite element analysis.