Background: Hallux valgus deformity has been reported to be associated with increased postural sway. However, the direction and magnitude of postural sway associated with hallux valgus remain inconclusive. We assessed the association between hallux valgus deformity and postural sway using a force plate.
Methods: The subjects were 169 healthy volunteers, > 40 years old (63 males, 106 females, average age: 66.0 ± 12.4 years old), who took part in an annual medical examination. We investigated the photographic hallux valgus angle (°), total trajectory length of the gravity center fluctuation (mm), area of the center of pressure (mm2), mediolateral and anteroposterior postural sway (mm) in a standing position with 2-legged stance and eyes open, hallux pain (Numerical Rating Scale), trunk and lower limb muscle mass (kg). We classified the subjects into a hallux valgus group (n = 44, photographic hallux valgus angle of 1 or both feet ≥ 20°) and a no hallux valgus group (n = 125, photographic hallux valgus angle of both feet < 20°) and analyzed the relationship between hallux valgus and postural sway.
Results: The anteroposterior postural sway in the hallux valgus group (6.5 ± 2.8) was significantly greater than in the no hallux valgus group (5.4 ± 2.2, p = 0.014), and the lower limb muscle mass in the hallux valgus group (12.4 ± 2.2) was significantly smaller than in the no hallux valgus group (13.5 ± 3.2, p = 0.016). The total value of the photographic hallux valgus angle on both feet was positively correlated with the anteroposterior postural sway (p = 0.021) and negatively correlated with the lower limb muscle mass (p = 0.038). The presence of hallux valgus (p = 0.024) and photographic hallux valgus angle (p = 0.008) were independently related to the magnitude of anteroposterior postural sway.
Conclusions: Hallux valgus deformity and its severity were positively associated with the magnitude of the anteroposterior postural sway.
Trial registration: 2017 - 135. Registered 22 August 2017.
Keywords: Anteroposterior postural sway; Force plate; Photographic hallux valgus angle.