Evaluation of rocker sole by pressure-time curves in insensate forefoot during gait

The rocker sole reduces plantar pressure in the insensate forefoot during gait, but the reasons have remained unclear. This study aimed to derive new variables descriptive of the effects of the rocker sole. We measured plantar pressures in eight forefoot areas in the insensate feet of ten diabetic subjects and performed stepwise regression of pressures as cubic functions of time in patients wearing shoes without and with prefabricated rocker soles. Pressure-time curves were all sigmoid in shape, but inflected at different time points, and were regressed by different variables in different forefoot areas in shoes without rocker soles. The rocker sole reduced peak pressures and pressure-time integrals and made pressure-time curves more concave. Inflections occurred at 15% or 16% of the gait cycle time and reached peak pressure later with the rocker. The more anterior the forefoot areas, the more concave their curves and the greater their regression parameters became. To evaluate the effectiveness of a rocker sole, physiatrists may regress sigmoid pressure-time curves as cubic functions of time in the insensate forefoot, check simultaneous inflections of the curves in areas rotated by the rocker sole, and compare their concavity and regression parameters in areas rotated at different distances from the axis of rotation. By doing so, physiatrists may be better able to improve the design of rocker sole and other forms of forefoot orthoses.