The Effect of Foot Structure on 1st Metatarsophalangeal Joint Flexibility and Hallucal Loading

摘要

The purpose of our study was to examine 1^st metatarsophalangeal (MTP) joint motion and flexibility and plantar loads in individuals with high, normal and low arch foot structure. Asymptomatic individuals (n=61), with high, normal and low arches participated in this study. Foot structure was quantified using malleolar valgus index (MVI) and arch height index (AHI). First MTP joint flexibility was measured using a specially constructed jig. Peak pressure under the hallux, 1^st and 2^nd metatarsals during walking was assessed using a pedobarograph. A one-way ANOVA with Bonferroni-adjusted post-hoc comparisons was used to assess between-group differences in MVI, AHI, Early and Late 1^st MTP joint flexibility in sitting and standing, peak dorsiflexion (DF), and peak pressure under the hallux, 1^st and 2^nd metatarsals. Stepwise linear regression was used to identify predictors of hallucal loading. Significant between-group differences were found in MVI (F2,56=15.4, p<0.01), 1^st MTP late flexibility in sitting (F2,57=3.7, p=0.03), and standing (F2,57=3.7, p=0.03). Post-hoc comparisons demonstrated that 1^st MTP late flexibility in sitting was significantly higher in individuals with low arch compared to high arch structure, and that 1^st MTP late flexibility in standing was significantly higher in individuals with low arch compared to normal arch structure. Stepwise regression analysis indicated that MVI and 1^st MTP joint early flexibility in sitting explain about 20% of the variance in hallucal peak pressure. Our results provide objective evidence indicating that individuals with low arches show increased 1^st MTP joint late flexibility compared to individuals with normal arch structure, and that hindfoot alignment and 1^st MTP joint flexibility affect hallucal loading.