A physics-based computational model of neonatal Developmental Dysplasia of the Hip (DDH) following treatment with the Pavlik Harness (PV) was developed to obtain muscle force contribution in order to elucidate biomechanical factors influencing the reduction of dislocated hips. Clinical observation suggests that reduction occurs in deep sleep involving passive muscle action. Consequently, a set of five (5) adductor muscles were identified as mediators of reduction using the PV. A Fung/Hill-type model was used to characterize muscle response. Four grades (1-4) of dislocation were considered, with one (1) being a low subluxation and four (4) a severe dislocation. A three-dimensional model of the pelvis-femur lower limb of a representative 10 week-old female was generated based on CT-scans with the aid of anthropomorphic scaling of anatomical landmarks. The model was calibrated to achieve equilibrium at 90° flexion and 80° abduction. The hip was computationally dislocated according to the grade under investigation, the femur was restrained to move in an envelope consistent with PV restraints, and the dynamic response under passive muscle action and the effect of gravity was resolved. Model results with an anteversion angle of 50° show successful reduction Grades 1-3, while Grade 4 failed to reduce with the PV. These results are consistent with a previous study based on a simplified anatomically-consistent synthetic model and clinical reports of very low success of the PV for Grade 4. However our model indicated that it is possible to achieve reduction of Grade 4 dislocation by hyperflexion and the resultant external rotation.
This study utilized a computational biomechanical model and applied the least energy path principle to investigate two pathways for closed reduction of high grade infantile hip dislocation. The principle of least energy when applied to moving the femoral head from an initial to a final position considers all possible paths that connect them and identifies the path of least resistance. Clinical reports of severe hip dysplasia have concluded that reduction of the femoral head into the acetabulum may occur by a direct pathway over the posterior rim of the acetabulum when using the Pavlik harness, or by an indirect pathway with reduction through the acetabular notch when using the modified Hoffman–Daimler method. This computational study also compared the energy requirements for both pathways. The anatomical and muscular aspects of the model were derived using a combination of MRI and OpenSim data. Results of this study indicate that the path of least energy closely approximates the indirect pathway of the modified Hoffman–Daimler method. The direct pathway over the posterior rim of the acetabulum required more energy for reduction. This biomechanical analysis confirms the clinical observations of the two pathways for closed reduction of severe hip dysplasia. The path of least energy closely approximated the modified Hoffman–Daimler method. Further study of the modified Hoffman–Daimler method for reduction of severe hip dysplasia may be warranted based on this computational biomechanical analysis. © 2016 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 35:1799–1805, 2017.
The aim of this paper is to develop a modeling method in order to predict the rebounce distance of a small size unmanned aerial system (sUAS) after collision with the ground. This distance would be useful to determine the safe range on the ground when operating the UAS. A two-step strategy is developed to model this procedure. In step one, numerical simulations are performed to model the first impact and predict the rebounce angle and impact velocity. Based on the information obtained, in step two, an analytical model is employed to calculate the rebounce distance without running numerical simulations, to save the computational time. Based on the model predictions, a non-linear function (known as a Meta model) is established to describe the rebounce behavior as a function of impact parameters, i.e. impact velocity, angle, and friction coefficient between the vehicle and ground. A correlation analysis is further performed to analyze the effect of these parameters on the response. The results show that the maximum rebounce range could be greater than 10 m. Compared to impact angle and friction coefficient, impact velocity is the most significant factor influencing the rebounce range. The larger velocity, smaller impact angle, and smaller ground friction coefficient would lead to the large rebounce range. The established Meta model would be useful to estimate safety range when operating sUAS platforms.
A physics-based computational model of neonatal Developmental Dysplasia of the Hip (DDH) following treatment with the Pavlik Harness was developed to obtain muscle force contribution in order to elucidate biomechanical factors influencing the reduction of dislocated hips. Clinical observation indicates that reduction occurs in deep sleep and involves passive muscle action. Consequently, a set of five (5) adductor muscles, namely, the Adductor Brevis, Adductor Longus, Adductor Magnus, Pectineus, and Gracilis were identified as mediators of reduction using the Pavlik Harness. A Fung-type model was used to characterize the hyperelastic stress-strain muscle response. Four grades (1–4) of dislocation as specified by the International Hip Dysplasia Institute (IHDI) were considered. A three-dimensional model of the pelvis-femur-lower limb assembly of a representative 10 week-old female was generated based on CT scans of a 6-month and 14-year old female as well as the visible human project with the aid of anthropomorphic scaling of anatomical landmarks. The muscle model was calibrated to achieve equilibrium at 90° flexion and 80° abduction. The hip was computationally dislocated according to the grade under investigation, the femur was restrained to move in an envelope consistent with Pavlik Harness restraints, and the dynamic response under passive muscle action and under the effect of gravity was resolved using the ADAMS solver in Solidworks. Results of the current model with an anteversion angle of 50° show successful reduction IHDI Grades 1–3, while IHDI Grade 4 failed to reduce with the Pavlik Harness. These results are consistent with a previous study based on a simplified anatomically-consistent synthetic model and clinical reports of very low success of the Pavlik Harness for Grade 4. However, our model indicates that it is possible to achieve reduction of Grade 4 dislocation by hyperflexion. This finding is consistent with clinical procedures that utilize hyperflexion to help achieve reduction for patients with severe levels of DDH for whom the Pavlik Harness fails.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.