Adam Ciszkiewicz1, Józef Knapczyk2. 1. Division of Experimental Mechanics and Biomechanics, Institute of Applied Mechanics, Cracow University of Technology, Poland. 2. State Higher Vocational School in Nowy Sącz, Poland.
Abstract
PURPOSE: The aim of this paper is to develop a model of the patellofemoral joint by considering the linear displacement along axis of cylindrical joint and to use this model in the analysis of the femur spatial displacements caused by the quadriceps muscle force. METHOD: The linear displacement along the axis of cylindrical joint of the patellofemoral joint is computed using optimization methods - minimization of the difference between the modeled and measured spatial displacements of the femur with respect to the tibia over the full range of the knee flexion. Then, the instantaneous screw displacements of the femur with regard to the tibia and corresponding muscle forces are computed for the model developed. The moment of the force arm with respect to the vector of screw displacement is used to evaluate the effectiveness of the acting force. RESULTS: The simulation results for the model developed show significant improvement of the modeled linear coordinates of the femur reference system with respect to tibia reference system. The displacement analysis of the femur loaded by quadriceps muscle force can be used to describe the patellofemoral dislocation problem. CONCLUSIONS: The model of the patella- femur joint where the linear displacement along axis of the cylindrical joint is considered can reproduce the actual patella displacements more accurately. It seems expedient to study elasto-statics problem of this mechanism. The model can be used to study some medical conditions such as patellofemoral dislocation.
PURPOSE: The aim of this paper is to develop a model of the patellofemoral joint by considering the linear displacement along axis of cylindrical joint and to use this model in the analysis of the femur spatial displacements caused by the quadriceps muscle force. METHOD: The linear displacement along the axis of cylindrical joint of the patellofemoral joint is computed using optimization methods - minimization of the difference between the modeled and measured spatial displacements of the femur with respect to the tibia over the full range of the knee flexion. Then, the instantaneous screw displacements of the femur with regard to the tibia and corresponding muscle forces are computed for the model developed. The moment of the force arm with respect to the vector of screw displacement is used to evaluate the effectiveness of the acting force. RESULTS: The simulation results for the model developed show significant improvement of the modeled linear coordinates of the femur reference system with respect to tibia reference system. The displacement analysis of the femur loaded by quadriceps muscle force can be used to describe the patellofemoral dislocation problem. CONCLUSIONS: The model of the patella- femur joint where the linear displacement along axis of the cylindrical joint is considered can reproduce the actual patella displacements more accurately. It seems expedient to study elasto-statics problem of this mechanism. The model can be used to study some medical conditions such as patellofemoral dislocation.