Three-dimensional Finite Element Biomechanical Analysis For Cam-type Femoroacetabular Impingement

Objective:To improve our understanding of intra-articular hip contact mechanics, three-dimensional finite element models of the normal and cam-type FAI hip joint were developed. The differences in cartilage contact mechanics are quantified and analysed between normal and cam-type FAI hip joint.Methods:The Computer Tomography(CT) images of a healthy female adult’s hip joint were obtained. Three-dimensional geometry models of normal and cam-type FAI joints with varied Alpha angle, which included the bony structure and articular cartilage, were constructed using Mimics and Hypermesh software. After smoothing and meshing, these hip models were imported into LS-DYNA analysis system, then dynamic loads and motions for normal walking, standing up and sitting down were applied to all joint models. Intra-articular cartilage contact pressures and stresses were calculated and crosscompared to evaluate the influence of morphology.Results:The established three-dimensional hip joint model were in good agreement with the real hip morphology. The cartilage contact mechanics predicted by finite element models were similar to those. reported in previous researchs. Peak contact pressures were found at the anterosuperior region of the acetabular rim during sitting down and standing up. The peaks of cam-type FAI were substantailly higher in comparison with the normal hip joint.Conclusion:The three-dimensional finite element hip joint model which developed based on CT dataset can accurately delineate the real geometry, providing an effective modeling protocol for further research. Abnormal cartilage contact pressures found in cam-type FAI hip models during standing up and sitting down, indicating occurrence of impingement changed the mechnical environment. Peak pressures at the anterosuperior area of acetabular cartilage maybe the main reason causing degeneration of cartilage and eventually leading to osteoarthritis.