Internationale Zeitschrift für Physikalische Medizin und Rehabilitation
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Finite Element Analysis of the Efficacy of Shelf Acetabuloplasty for Acetabular Dysplasia

Nozomi Kaga, Takehiro Iwami, Kimio Saito, Komatsu Akira and Yoichi Shimada

Objective: Shelf acetabuloplasty is a type of joint-preserving surgery. There are only a few cases of studying the mechanical evaluations of shelf acetabuloplasty. The objective of this study was to investigate the biomechanical effects of acetabular dysplasia on the acetabular margin and the efficacy of shelf acetabuloplasty using a threedimensional musculoskeletal model and finite element analysis.
Methods: Subjects were five adult female patients with hip osteoarthritis and acetabular dysplasia who underwent the shelf procedure. Using the data of 4 healthy adult women, joint reaction force in the hip joint during static standing was estimated using Any Body Modeling System. From the CT images of each subject, finite element models of the pelvis and the right femur were constructed using Mimics and then converted to a three-dimensional finite element model using 3matic. Stress analysis was carried out using Marc Mentat 2011 1.0 finite element analysis software. In this study, all areas other than soft tissue were considered to be hard bone. In the boundary conditions, the iliac bone and pubic symphysis in the pelvis were fully constrained. Estimated hip joint reaction force was applied as a concentrated load from the distal end of the femur, and von Mises-equivalent stress in the acetabulum was analyzed. The stress distribution, the maximum stress value and the acetabular area applied to the acetabular surface of the acetabulum during resting stance were evaluated before and after the operation.
Results: In the stress distribution of the acetabulum during static standing, the stress was dispersed after the operation, and the maximum stress was decreased. The area of acetabular area was significantly increased after the operation. The maximum stress value was significantly decreased after surgery.
Conclusion: In all cases, the stress distribution of the acetabulum at the time of standstill standing after the operation of shelf acetabuloplasty was significantly dispersed and decreased as compared with the preoperative state.