Mobility of the First Ray in Feet with and Without Hallux Valgus

Background: This study aimed to describe the dorsiflexion and plantarflexion motion of the first ray in feet with and without hallux valgus. Methods: Eight hundred feet were examined and classified into normal feet without hallux valgus (n = 227) and feet with hallux valgus (n = 387). Dorsiflexion and plantarflexion of the first ray were quantified with a handheld ruler. Univariate comparisons of the first ray mobility were made between feet with and without hallux valgus. A two-stage cluster analysis was performed to define the range of dorsiflexion and plantarflexion values in both groups. Odds Ratios were obtained to determine whether dorsiflexion or plantarflexion showed more influence on hallux valgus. Multinomial logistic regression was used to predict the probability of having or not having hallux valgus, given dorsiflexion and plantarflexion of the first ray as independent variables. Results: Dorsiflexion showed statistically significant differences between groups (p = 0.011) but with a small effect size (Rosenthal's r = 0.10). Plantarflexion showed statistically significant differences between groups (p < 0.001) with a larger effect size (r = 0.71). Range of dorsiflexion was between 6 and 7 mm in both normal and hallux valgus feet. Range of plantarflexion in normal feet was 6-7 mm, and in hallux valgus feet 4-5 mm. Logistic regression showed that plantarflexion of the first ray had higher influence on HV than dorsiflexion. Conclusions: In hallux valgus feet, plantarflexion of the first ray was significantly lower than in normal feet, suggesting that a decreased range of plantarflexion is strongly related to hallux valgus.