In silico analysis on sacroiliac joint fixation during normal walking

According to medical statistics, sacroiliac joints (SIJs) appear to be the source of low back pain in 15–30% of cases. The SIJs are located at the junction between the sacrum and the ilium, supported by strong ligaments and with low mobility. Due to unexpected external force or repeated impact, pain may arise from the SIJ region (SIJ dysfunction). The treatment to cure SIJ dysfunction includes nonsurgical approaches as well as surgery with implants (SIJ fixation). Previous studies have assessed the consequences of SIJ fixation, but no simulation study so far has been performed during walking. The SIJ is burdened with variant loads during walking. In this given study, walking conditions were replicated in a finite element model of the pelvis combined with 3D walking analysis data. The simulation mimicked two types of unilateral SIJ fixation: anterior fixation with a plate implant and screws (model A) and posterior fixation with a rod, a cage and screws (model P). Equivalent stress of the SIJ and the loading of the SIJ ligaments decreased in the fixed models. In these fixed pelves, the slight motion on the SIJ decreased. The reduction rates on equivalent stress, ligament loads and equivalent stress were low during the swing phase. In addition, the efficiency of fixations was mostly same on anterior and posterior fixations. It can be concluded that the stronger fixation reduces the loading but also may have a greater impairment effects on walking. © 2024 The Japan Society of Mechanical Engineers. This is an open access article under the terms of the Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0/).