title: Squatting-related tibiofemoral shear reaction forces and a biomechanical rationale for femoral component loosening.
abstract: Previous gait studies on squatting have described a rapid reversal in the direction of the tibiofemoral joint shear reaction force when going into a full weight-bearing deep knee flexion squat. The effects of such a shear reversal have not been considered with regard to the loading demand on knee implants in patients whose activities of daily living require frequent squatting. In this paper, the shear reversal effect is discussed and simulated in a finite element knee implant-bone model, to evaluate the possible biomechanical significance of this effect on femoral component loosening of high flexion implants as reported in the literature. The analysis shows that one of the effects of the shear reversal was a switch between large compressive and large tensile principal strains, from knee extension to flexion, respectively, in the region of the anterior flange of the femoral component. Together with the known material limits of cement and bone, this large mismatch in strains as a function of knee position provides new insight into how and why knee implants may fail in patients who perform frequent squatting.
authors: Department of Chemical and Materials Engineering, University of Auckland, 20 Symonds Street, Auckland 1142, New Zealand.
authors: Ashvin
authors: A
authors: Thambyah
authors: Auckland Bioengineering Institute, University of Auckland, 70 Symonds Street, Auckland 1010, New Zealand ; Department of Engineering Science, University of Auckland, 70 Symonds Street, Auckland 1010, New Zealand.
authors: Justin
authors: 0000-0001-7721-8698
authors: J
authors: Fernandez
mesh_terms: D001696:Biomechanical Phenomena; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008962:Models, Theoretical; D013314:Stress, Mechanical; D016474:Weight-Bearing