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Title: Effects of transtibial prosthetic malalignments on socket reactions
Authors: TAN CHI WEI
Keywords: Transtibial prosthetic malalignments socket reactions pylon transducer
Issue Date: 28-Jul-2009
Citation: TAN CHI WEI (2009-07-28). Effects of transtibial prosthetic malalignments on socket reactions. ScholarBank@NUS Repository.
Abstract: The effects of transtibial prosthetic malalignments on socket responses during the stance phase of gait was measured in six-directions in terms of the anterior-posterior shear force, medial-lateral shear force, the axial force, the coronal moment, the sagittal moment and the axial torque. Altogether, 16 different alignment perturbations were studied based on a predefined reference plane of a nominally aligned prosthesis established using the traditional method of dynamic alignment. 2 subjects took part in the study.Analysis of results using ANOVA (one-sided) demonstrated that socket malalignments had very significant effects on socket reactions in the sagittal and coronal planes under a statistical condition that p < 0.05. The overall results for two subjects demonstrated that the mechanical moments in the coronal plane are most sensitive to coronal translation of the socket with 65 variables (out of a maximum of 80) satisfying the condition for statistical significance. Sagittal translational perturbations of the prosthetic socket also produced the strongest effects on the sagittal moments with 64 variables. In terms of angular misalignments, the results were not as strong as translational ones in both the sagittal and coronal planes (59 variables). Coronal angulations had the largest effect on medial-lateral shear forces followed by sagittal angulation while anterior-posterior shear forces are most sensitive to malalignments in the anterior-posterior plane. In the orthogonal planes, axial torques and medial-lateral shear forces were highly sensitive to sagittal angular perturbations. The former was supported by 51 variables and the latter 48 variables with p < 0.05. . From the physical sense, malalignment of the prosthetic socket in one plane should not affect the results in the other. This could, perhaps, be explained through the b screw-home mechanismb of the knee joint. Thus, even though malalignments were carried out in one plane, three dimensional kinematic changes were actually taking place during amputee gait. Among the six parameters of forces and moments studied, the axial forces were the least sensitive to any malalignment perturbations.When relating lower limb joint kinematics and socket reaction moments, the socket reaction moments in the sagittal plane could not effectively relate to the biomechanics of gait. This was because a differentiation of socket reaction moments plots were not particularly evident due to malalignments. The plots of socket reaction moments due to coronal plane translational malalignment could effectively evaluate the biomechanics of coronal plane stability. Under all circumstances, it was not possible to determine the relationship between interface pressures and socket reaction moments because of a lack of data in this aspect.
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