Contact pressure distribution of the hip joint during closed reduction of developmental dysplasia of the hip: a patient-specific finite element analysis

Zhiqiang Zhang,Hai Li,Dashan Sui,Ziming Zhang,Haiyi Qin

doi:10.1186/s12891-020-03602-w

Abstract

BackgroundDevelopmental dysplasia of the hip (DDH) is the most common deformity of the lower extremity in children. The biomechanical change during closed reduction (CR) focused on cartilage contact pressure (CCP) has not been studied. Thereby, we try to provide insight into biomechanical factors potentially responsible for the success of CR treatment sand complications by using finite element analysis (FEA) for the first time.MethodsFinite element models of one patient with DDH were established based on the data of MRI scan on which cartilage contact pressure was measured. During CR, CCP between the femoral head and acetabulum in different abduction and flexion angles were tested to estimate the efficacy and potential risk factors of avascular necrosis (AVN) following CR.ResultsA 3D reconstruction by the FEA method was performed on a 16 months of age girl with DDH on the right side. The acetabulum of the involved side showed a long, narrow, and “flat-shaped” deformity, whereas the femoral head was smaller and irregular compared with the contralateral side. With increased abduction angle, the stress of the posterior acetabulum increased significantly, and the stress on the lateral part of the femoral head increased as well. The changes of CCP in the superior acetabulum were not apparent during CR. There were no detectable differences in terms of pressure on the femoral head.ConclusionsSevere dislocation (IHDI grade III and IV) in children showed a high mismatch between the femoral head and acetabulum. Increased abduction angle corresponded with high contact pressure, which might relate to AVN, whereas increased flexion angle was not. Enhanced pressure on the lateral part of the femoral head might increase the risk of AVN.

Highlights

Developmental dysplasia of the hip (DDH) is the most common deformity of the lower extremity in children
This study aimed to provide insight to identify biomechanical factors potentially responsible for the success of closed reduction (CR) or post-treatment complications by using finite element analysis (FEA)
The corresponding affected femoral head had an irregular shape, which further increased the difficulty of matching the acetabulum when performing CR. (Fig. 5)

Summary

Introduction

Developmental dysplasia of the hip (DDH) is the most common deformity of the lower extremity in children. Thereby, we try to provide insight into biomechanical factors potentially responsible for the success of CR treatment sand complications by using finite element analysis (FEA) for the first time. Developmental dysplasia of the hip (DDH) is the most common developmental malformation affecting children’s hips. The principle of treatment is to establish a stable, concentric reduction of the hip to enable the subsequent hip development as early as possible, given the well-established correlation between residual dysplasia and the age of reduction [1, 2]. Closed reduction (CR) of the hip is indicated in patients who failed to achieve stable reduction with Pavlik harness, and or as the primary treatment option for patients with late diagnosis [4, 5]. Finite element analysis (FEA) is especially useful in bioengineering and biomechanical modeling. FEA can replace biomechanical experiments to some extent, and can control the experimental conditions and simulate the biomechanical conditions of the human body [6]

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