Abstract
The sacroiliac joint (SIJ) is burdened with variant loads. However, no methods have allowed to measure objectively how the SIJ deforms during bipedal walking. In this study, in-vivo walking conditions were replicated in a kinematic model combining the finite element method with 3D walking analysis data divided into five phases in order to visualize the load transition on the SIJ and clarify the role of the SIJ. Both models with and without inclusion of the SIJ were investigated. In models with bilateral SIJs, the displacement differed greatly between the sacrum and both hip bones on the SIJ as the boundary. The movements of the sacrum involved a nutation movement in the stance phase and a counter-nutation in the swing phase relative to the ilium. In models without SIJs, the displacement of the pelvis and loads of pelvic ligaments decreased, and the equivalent stress of the SIJs increased compared to the model with SIJs. The walking loads cause distortion of the entire pelvis, and stress concentration at the SIJ are seen due to the morphology of the pelvic ring. However, the SIJs help dissipate the resulting stresses, and the surrounding ligaments are likewise involved in load transmission.
Highlights
The sacroiliac joint (SIJ) is burdened with variant loads
Regarding the maximum equivalent stress of the right SIJ cartilage, the values at phase 2, when the maximum equivalent stress was highest, averaged 41.2 MPa in the bone model, i.e., in phase 2 the values of the bone model increased to approximately 700% of the cartilage model
Given the left and right SIJ showed separate movements, it was possible to walk on a human bipedal walking with a standing leg and a free leg alternatively. This suggests that the SIJs plays an important role in the human bipedal walking mechanism, but very little information is to date available on the nutation and counter-nutation during walking, and these findings need to be substantiated further. This simulation was performed for the first time by implementing actual 3D walking data into a finite element model of the pelvis elaborated from large-scale anatomical studies
Summary
The sacroiliac joint (SIJ) is burdened with variant loads. no methods have allowed to measure objectively how the SIJ deforms during bipedal walking. In-vivo walking conditions were replicated in a kinematic model combining the finite element method with 3D walking analysis data divided into five phases in order to visualize the load transition on the SIJ and clarify the role of the SIJ. Both models with and without inclusion of the SIJ were investigated. Previous research made attempt to quantify the SIJ motion by three-dimensional computed tomography (3D-CT) and by loading tests on cadavers, reporting that the SIJ moves less than 1 mm and does function as a joint[5] These trials were conducting under static conditions. This finite element model included both femora, and simulations can be performed with walking data
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