Parallelogram Law Of Forces Experiment Pdf Download __EXCLUSIVE__
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For lateral bending, we conclude that the specific behavior of the construct is largely caused by the boundary conditions of the biomechanical test setup: in our case, the setup allows for coupled motion in the translational plane orthogonal to the loading axis, which prevents the build-up of relevant lateral shear forces and which results in pure bending moments around the loading axis. Without the generation of relevant lateral shear forces, only small parallelogram deformation is generated, which explains the small parallelogram deformation in our results. However, in a setup that does not allow coupled motion in the translational plane orthogonal to the loading axis (constrained lateral bending), relevant lateral shear forces can occur, which can, in turn, result in larger parallelogram deformation. In such a situation, crosslink-augmentation could result in an increase in construct stiffness by reducing this parallelogram deformation.
We evaluate the screw rotation during axial rotation to be the direct result of the parallelogram deformation in this loading direction. Crosslink-augmentation is able to reduce parallelogram deformation and, thereby, also screw rotation by about 60%. The remaining 40% of screw rotation can be explained by elastic deformation of the screw-rod construct and the vertebral bodies under the acting loads, as no signs for plastic deformation of the instrumentation and no signs of screw loosening in the bone were observed.
In the present study, the investigated novel crosslink was able to reduce in vitro screw rotation and in-vitro parallelogram deformation in axial loading and in vitro screw rotation in lateral bending by about 60%. This is in general agreement with the in-vivo results published by Hohmann et al3 and confirms the positive effect of the new crosslink on screw-rod construct stability. This effect of the crosslink is most likely due to the increase of crosslinking stiffness by the addition of linker material.
To graphically find the dot product using the parallelogram method we would first find the dotproduct of the horizontal and vertical components of the vectors. Then we draw two parallellines that are connecting the point of intersection of the vectors to the origin. Afterthat we find the dot product of each vector to the origin. We find the dot product of thetwo vectors to the origin using the equation: (a*b)+ (b*c)+ (c*a) = (a*c)+(b*c)=0.
Based on the results, we would not recommend crosslink-augmentation for axial rotation. The screw rotation is generated by the instrumentation, regardless of the effectiveness of the crosslink in reducing parallelogram deformation. However, parallelogram deformation was reduced by about 60% by the crosslink-augmentation in lateral bending. This effect is known from literature3 and can be explained by the reduction in the loads acting on the spinal instrumented segments due to the stiffer construct under lateral bending. We would recommend crosslink-augmentation in lateral bending to reduce construct-related failure, especially in those cases, where large construct-related motions like in-transient instability or construct-related nonunion are likely to occur. For this purpose, early-stage constructs can be instrumented with a crosslink to limit construct-related failure at later stages. 827ec27edc