Foot arch height and rigidity index associated with balance and postural sway in elderly women using a 3D foot scanner

Background: The maintenance of balance is a complex phenomenon that is influenced by a range of sensorimotor factors. Foot arch height index (AHI) and arch rigidity index (ARI) may also influence balance and postural sway. According to the literature, measurement of foot posture is widely considered to be an important component of musculoskeletal examination in clinical practice and research. On the other hand, the recent use of 3D foot scanners allows a large number of subjects to be scanned quickly and easily and helps to reduce the patient’s radiation exposure from xrays. Purpose: The purpose of this study was to determine whether AHI and ARI are associated with balance and postural sway by examining a large community sample of elderly women using recent 3D foot scanner technology. Methods: This cross-sectional study included 140 community-dwelling elderly women (73.9 ± 5.1 years) recruited in Kasama City, Japan. We assessed static and dynamic balance using one leg stance (OLS) and timed up & go (TUG). Postural sway variables, total path length (TPL) (cm), and area (cm) were measured by force plate. We measured AHI and ARI with DreamGP Incorporated’s 3D foot scanner (Osaka, Japan). In this study, AHI was defined as the linear distance (mm) from the instep, defined by the foot scanning machine, to the supporting surface while sitting and while standing with 50% weight bearing on each foot, divided by truncated foot length. ARI was the ratio of AHIstand/AHIsit. Results: After adjusting for potential confounders, univariate analyses revealed that AHI is significantly associated with OLS (P = 0.010), TPL (P= 0.031), and area (P = 0.024) in the sitting position. However, there was no association between standing AHI and balance or postural sway tests. Area (P= 0.024) was also associated with ARI. Conclusion: Our findings suggest that sitting AHI is associated with balance and postural sway, while ARI is associated with area in elderly women. Therefore, AHI and ARI might play important part in defining balance control in elderly women.