In Silico Pelvis and Sacroiliac Joint Motion: Refining a Model of the Human Osteoligamentous Pelvis for Assessing Physiological Load Deformation Using an Inverted Validation Approach

Abstract

Introduction. Computational modeling of the human pelvis using the finite elements (FE) method has become increasingly important to understand the mechanisms of load distribution under both healthy and pathologically altered conditions and to develop and assess novel treatment strategies. The number of accurate and validated FE models is however small, and given models fail resembling the physiologic joint motion in particular of the sacroiliac joint. This study is aimed at using an inverted validation approach, using in vitro load deformation data to refine an existing FE model under the same mode of load application and to parametrically assess the influence of altered morphology and mechanical data on the kinematics of the model. Materials and Methods. An osteoligamentous FE model of the pelvis including the fifth lumbar vertebra was used, with highly accurate representations of ligament orientations. Material properties were altered parametrically for bone, cartilage, and ligaments, followed by changes in bone geometry (solid versus 3 and 2 mm shell) and material models (linear elastic, viscoelastic, and hyperelastic isotropic), and the effects of varying ligament fiber orientations were assessed. Results. Elastic modulus changes were more decisive in both linear elastic and viscoelastic bone, cartilage, and ligaments models, especially if shell geometries were used for the pelvic bones. Viscoelastic material properties gave more realistic results. Surprisingly little change was observed as a consequence of altering SIJ ligament orientations. Validation with in vitro experiments using cadavers showed close correlations for movements especially for 3 mm shell viscoelastic model. Discussion. This study has used an inverted validation approach to refine an existing FE model, to give realistic and accurate load deformation data of the osteoligamentous pelvis and showed which variation in the outcomes of the models are attributed to altered material properties and models. The given approach furthermore shows the value of accurate validation and of using the validation data to fine tune FE models.

Sacrospinous and sacrotuberous ligaments influence in pelvis kinematics

“…A FE model of a pelvis previously developed and refined (Ramezani et al, 2019 ; Toyohara et al, 2020 ; Venayre et al, 2021 ) was deployed to analyze the deformation of the pelvis as a response to different load force representing upper body part and different elastic properties of the SS and ST ligaments. Bone geometries were extracted from the computed tomography scan of a healthy male (29 years, body height 185 cm, body weight 69 kg).…”

“…Points where the deformations were measured are shown in Figure 2. Those points were previously shown to be good indicators of pelvis ring deformation and stability and served as validation points in computer-cadaveric studies (Hammer, Scholze, et al, 2019;Ramezani et al, 2019). Point S M was defined in the ventral center of the sacrum or the left (S L ).…”

“…The aim of this given numerical study was to assess the influence of three different configurations for the SS and ST ligaments on pelvis kinematics. For this purpose, a detailed and previously validated model of the osteoligamentous pelvis was used (Hammer, Scholze, et al, 2019 ; Ramezani et al, 2019 ), which has been extended to include the hip joint to allow for a more realistic motion of the sacrum relative to a movable innominate bone. It has been hypothesized that (A) lowering material stiffness for the SS and ST ligaments improves the accuracy of in silico with in vitro kinematics for the osteoligamentous pelvis.…”

“…The results of the computer model were compared with experimental results from the authors' previous study (Hammer, Scholze, et al, 2019 ; Ramezani et al, 2019 ). In addition, a sensitivity analysis of the pelvic deformation with respect to the load from the upper body was performed using the finite element (FE) method.…”

Finite element analysis of load transition on sacroiliac joint during bipedal walking

“…In this study, computer simulations were performed using finite element analysis during normal walking, resembling the five walking phases of a living body. The finite element model of the pelvis used in this experiment has reproduced the SIJ and the surrounding ligaments by previous anatomical studies [9][10][11][12][13] . In addition, this finite element model included both femora, and simulations can be performed with walking data.…”