THE EFFECT OF KNEE POSTURES AND CUSHIONS IN THE LOAD TRANSMISSION OF IMPACT LOADING - AN IN VITRO BIOMECHANICAL PORCINE MODEL
Abstract
Degenerative osteoarthritis is the consequence of impact force applied to articular cartilage that results in surface fissuring. Soft cushions and flexed posture are two important factors to reduce the impact force; however, no quantitative information of how soft should the cushion be to prevent the injury and the mechanism of force attenuation of knee joint at neutral and flexed posture was not well documented yet. The objective of current study is hence to find the quantitative shock attenuation of knee joint using different stiffness of cushions when the knee is at neutral posture and flexed posture. A “drop-tower type” impact apparatus was used for testing. Nineteen fresh porcine knee joints were divided into two posture groups, i.e. neutral and flexed posture. All specimens were tested using stiff, medium, and soft cushions. The axial reaction force, anteroposterior shear force, and flexion bending moment were recorded for analysis. We found the flexed posture decreased the axial reaction force and anterior shear force but increased the flexion bending moment. The effect of stiffness of cushions on the mechanical response of knee joint during impact loading was significant for neutral posture but not for flexed posture.