The Relationship Between Forefoot Structure And Rearfoot And Midfoot Mechanics

Abstract

It is often suggested that foot structure and foot mechanics are related.For example, forefoot varus is purported to be associated with midfoot and rearfoot pronation. However, there is little scientific evidence for these relationships. PURPOSE To assess the relationship between forefoot structure and midfoot and rearfoot pronation. It was hypothesized that as forefoot varus increased, medial midfoot pressures and calcaneal eversion during walking would increase. METHODS Subjects were healthy individuals (16 males, 16 females) aged 28.8 (+/− 8.8 yrs). Forefoot structure was measured by a single experienced physical therapist (ICC (2, k)=0.95). Subjects then underwent an instrumented gait analyis focusing on plantar pressures and rearfoot kinematics. Retro-reflective markers were placed on the tibia and calcaneus. Kinematics were collected with a 3D motion analysis system (120 Hz) and plantar pressures were collected with a pressure mat (70 Hz). The peak pressure of the medial midfoot area (MMPP) was used as an indication of midfoot pronation, and rearfoot eversion excursion (EvExc) was used to indicate rearfoot pronation. Linear regressions between forefoot varus and MMPP, as well as between forefoot varus and EvExc were performed. In addition, feet were subdivided into low, normal and high forefoot varus, based on the mean and standard deviation of a reference population of 102 feet. A one-way ANOVA was used to compare results between the foot categories. RESULTS A significant relationship was found between forefoot position and MMPI (r=0.59, r 2 =0.35, p<0.01) and EvExc (r=0.65, r 2 =0.42, p<0.001). In addition, MMPI was significantly different (Fig. 1a) between all three forefoot groups (p<0.05). EvExc was significantly different (Fig. 1b) between the low and high forefoot varus groups (p<0.05). These data support the suggestions of a relationship between forefoot varus and dynamic midfoot and rearfoot pronation.Figure 1CONCLUSIONS Based on these results, it appears that as forefoot varus increases, both medial midfoot pressures and rearfoot eversion increases.