Arch Height Index, Arch Rigidity Index, and Arch Stiffness Values in a Symptomatic Population

Studies of arch height index (AHI), arch rigidity index (ARI), and arch stiffness have primarily focused on healthy populations. Normative values of the aforementioned measurements in a pathologic sample may be useful in identifying relationships between arch structure and pathology.

AHI was obtained bilaterally at 10% and 90% weightbearing conditions using the AHI measurement system. ARI and arch stiffness were calculated using AHI measurements. Dependent t tests compared right and left, dominant and nondominant, and injured and noninjured limbs. Dominant feet were compared between sexes using independent t tests. Relationships between arch stiffness and subcategories were examined using the coefficient of determination (R2). One-way analyses of variance determined differences between arch structure and number of pathologies or body mass index (BMI).

A total of 110 participants reported one (n = 55), two (n = 38), or three or more (n = 17) pathologies. Plantar fasciitis (n = 31) and hallux valgus (n = 28) were the most common. AHI, ARI, and arch stiffness did not differ between limbs or sexes for any comparisons. Between subgroups of BMI and number of pathologies, BMI influenced AHI (10% weightbearing) and arch stiffness (P < .05). Arch stiffness showed a weak relationship to AHI, where a higher AHI was associated with a stiffer arch (R2 = 0.06).

Normative arch structure values were established in a pathologic sample with a large incidence of plantar fasciitis and hallux valgus. Understanding relationships between arch structure and pathology is helpful for clinicians and researchers.