Biomechanical responses of the femur-prosthesis-tibia complex after tumor-type total artificial knee replacement / 医用生物力学

ABSTRACT

Objective By studying biomechanical responses of the femur-prosthesis-tibia complex under normal standing condition after tumor-type hinged knee arthroplasty, to investigate the cause of femoral perforation in patients after knee arthroplasty, so as to provide a theoretical basis for optimal design and manufacturing of tumor-type hinged artificial knee prosthesis. Methods By coupling CT and 3D optical scanning, the finite element model of the subject-specific femur-prosthesis-tibia complex was established and was validated regarding its availability, so as to analyze stress distribution and stress shielding phenomenon of the complex in standing position. Results (1) Under the loading state of standing, the stress on the femur was significantly larger than that on the tibia, and presented an evident concentration phenomenon. The proximal 1/3 of femoral shaft presented a larger stress, with a stress shielding effect. (2) As the model was based on geometry and bone characteristics of the patient in clinic, the location of femur stress concentration was close to that of femur perforation in the patient, which indicated that femur injury behavior might occur when its own gravity was applied such as the patient condition. Conclusions After implantation of the tumor-type hinged artificial knee prosthesis, the prosthesis marrow needle goes deep into marrow cavities, which brings certain pressure to the marrow cavities even under normal standing condition. The produced stress shielding effect and the match of the prosthesis marrow needle to the marrow cavity are all likely to cause stress concentration on the femur, even make femur crack or perforation, and eventually affect the surgery quality. Thus, the prosthesis design should be carefully optimized before surgery in order to reduce or avoid such phenomenon that is related to the postoperative complication rate.