Muscle activity and postural sway during standing balance tasks in adults with hallux valgus reporting low levels of foot pain: A case-control study.

BACKGROUND

Hallux valgus is a common foot deformity potentially impacting balance, however previous studies report conflicting findings, and further exploration of postural sway mechanisms in hallux valgus is warranted. This study investigated the impact of hallux valgus on abductor hallucis muscle activation and postural sway during balance tasks, and correlations between foot characteristics and postural sway in hallux valgus.

METHODS

Thirty adults with hallux valgus (mean age 53.7 ± 19.3 years) and 20 controls (mean age 50.0 ± 20.1 years) performed two static standing balance tasks: bipedal and single limb stance. Centre of pressure (COP) excursion was recorded using an AccuswayPLUS balance platform (AMTI), and surface electromyography was recorded using a MA300 system (Motion Lab Systems Inc.). Age, height, weight, self-reported foot pain, Foot Posture Index, foot mobility, hallux flexion strength and intrinsic foot muscle morphology (via ultrasound imaging) were measured.

FINDINGS

There were no significant between-group differences in muscle activity or postural sway during balance tasks. The hallux valgus group had a more pronated Foot Posture Index compared to controls (P < 0.01) and larger cross-sectional area of the abductor hallucis muscle (P = 0.02). Both groups reported low levels of foot pain. In hallux valgus participants, increased anteroposterior sway was associated with reduced foot mobility (r = -0.45, P = 0.02), and greater COP path excursion was associated with reduced abductor hallucis cross-sectional area (r = -0.45, P = 0.04).

INTERPRETATION

Adults with hallux valgus reporting low levels of foot pain and showing no substantial intrinsic foot muscle atrophy or weakness, may demonstrate static postural control equivalent to age-matched controls.