Biomechanical Study of Stability and Wear of Total Hip Prosthesis under Dynamic Gait Load.

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Purpose There were few reports of stress analysis in total hip arthroplasty (THA) under dynamic load based on human gait. In this study, we calculated dynamic resultant forces of the hip based on gait analysis of a patient undergone THA and performed serial analysis of polyethylene wear under this dynamic load using a nonlinear 3-dimensional finite element method (FEM).Materials and Methods 1) We performed 3-dimensional computer simulation of a normal human gait using the SIMGAIT and ADAMS software based on data taken from gait analysis using a VICON, and calculated the dynamic resultant forces of the hip. These values were compared with those in the previous in vivo studies using a telemetric prosthesis. 2) We calculated dynamic resultant forces of the hip of a patient before revision THA by the same method. These dynamic forces during one gait cycle applied on the 3-dimensional FEM model of the acetabular component that were precisely constructed using the CT and radiograph of this p … More atient. The amount and rate of volumetric polyethylene wear were calculated using a nonlinear 3-dimensional FEM software (ADINA), based on the number of gait cycles per year measured by a pedometer that the patient had kept throughout a year. The total amount and rate of volumetric wear at revision surgery by the FEM analysis were compared with those in the retrieval study.Results 1) The magnitude and direction of our dynamic resultant forces of the normal human gait were consistent with those in the previous in vivo studies. 2) Our results calculated by FEM analysis were very similar to those directly measured from the retrieved acetabular component in total amount and rate of volumetric wear.Discussion The results of this study suggested that our method would be useful to predict the serial wear performances of total hip prosthesis. Although our method did not take the condition of hydrodynamic lubrication and initial polyethylene wear into consideration, it was anticipated that this method could predict more true and more detailed wear performances in vivo by modifying based on the data of many cases. Less