Finite element analysis of effect of softness of cushion pads on stress concentration due to an oblique load on pressure sores.

The concentration of mechanical stress in soft tissue can cause or worsen pressure sores. We have previously reported the results of analysis of stress concentration in soft tissue using a finite element model. In the present study, we hypothesized that even if a cushion pad was thin, it would effectively reduce horizontal loads that can increase stress concentration in soft tissue. To our knowledge, there have been no previous reports describing stress distribution in soft tissue attached to a thin cushion pad with a horizontal load. In the present study, we performed mechanical analysis of a model of a human seated on a thin cushion pad with a range of hardness values (i.e., Young's module). Two-dimensional finite element models were used to perform this analysis. Loads were applied at the upper edge of the model as oblique compulsory displacement. In all of the cushion pad models, the peak value of effective stress was less than that of the control model without a cushion pad. Also, the peak value of effective stress decreased as Young's module of the cushion pad decreased. These results suggest that use of a thin cushion pad is an effective way to prevent the development of pressure sores.