The effect of forefoot varus on postural stability

Study Design: Counterbalanced experimental design study comparing a group of subjects with greater than or equal to 70 of forefoot varus (MFV) to a group with less than 70 of forefoot varus (LFV). Objectives: To investigate the effect of forefoot varus on single-limb stance postural stability (PS). Background: Impaired PS has been implicated as a potential risk factor for sustaining acute foot and ankle injuries. The identification of variables that deleteriously affect PS may be important in the prevention or future injuries. Methods and Measures: Postural stability of the MFV group (n = 20) and the LFV group m = 12) was assessed during right and left single-limb stance and eyes-open and eyes-closed conditions. Standard deviations of the x-axis and y-axis ground reaction forces measured via a force platform were used to represent anteroposterior (AP) and mediolateral (ML) PS, respectively. The mean of 3 successful 5-second trials of each testing condition was calculated and used for subsequent data analysis using 3-way mixed-model ANOVAs with 1 between-subject and 2 within-subject factors. Results: The AP PS scores of the MFV group were significantly greater than those of the LFV group (P<.05). ML PS scores, although higher in the MFV group, were not significantly different from those of the LFV group. Both groups had significantly greater AP and ML PS scores during the eyes-closed versus the eyes-open condition (P<.05). Conclusions: The results suggest that the presence of greater than or equal to 7degrees of forefoot varus may significantly impair AP PS. The decreased stability associated with increased forefoot varus may be due to decreased joint congruity and consequently an increased reliance on soft tissue structures for stability.