Effect Of Soft Orthotics On Tibial Shock And Rearfoot Motion

Introduction: Foot Orthotic Devices (FODs) are often prescribed as a means of decreasing rearfoot motion and/or lower extremity shock. The materials used in construction of the orthoses vary depending on the intended function: rigid devices are used primarily for rearfoot stability, compliant orthoses are thought to provide cushioning, and some devices attempt to achieve both. The effect of orthotic devices on rearfoot stability has been studied extensively. In addition, there are several investigations concerning shock reduction in flat insoles of varying materials. There are no studies, however, that have assessed the effect of custom molded orthotics on tibial shock. Therefore, the purpose of this study was to compare the effects of a semirigid orthotic device designed for rearfoot control to a soft device designed for both rearfoot control and shock attenuation. Methods: Three-dimensional kinematic and tibial accelerometry data were collected on 15 recreational runners. Comparisons between the no orthotic (control), the semirigid (subortholene), and the soft orthotics (EVA) were analyzed in subjects running in the same model shoes. The kinematic variables of peak eversion (PEV), eversion excursion (EXEC), and eversion velocity (EVEL) were evaluated, while tibial shock was determined by the peak positive acceleration (PPA). Results were analyzed using a one-way repeated measures ANOVA to test for significance. Results: (SeeTable) Neither a semirigid nor a dual purpose designed soft orthotic significantly reduced tibial shock or rearfoot motion. Both orthotic devices showed a trend toward a decrease in peak eversion, but the reductions were small (less than 2 degrees). Conclusions: Based on the results of this study, the soft orthoses designed for both rearfoot control and shock reduction did not provide the intended biomechanical function. Therefore, it may not be possible to obtain both shock attenuation and rearfoot control from the same orthotic device.Table