Scientific Paper: Targeted Insole Intervention Strategies for Hallux Valgus: Biomechanical and Fatigue Resistance Benefits of Medial Forefoot Wedge versus Arch Support Designs

Objectives
Hallux valgus, characterized by lateral deviation of the great toe, impairs gait stability, propulsion efficiency, and load distribution, often exacerbated under fatigue. This study aimed to compare the biomechanical and fatigue-resistance benefits of two customized functional insoles—a medial forefoot wedge and an arch support—against normal insoles in adults with mild to moderate hallux valgus. Specifically, the research sought to evaluate changes in ground reaction force components, joint angle coordination, and muscle activation patterns during both non-fatigue and fatigue states. By integrating kinematic, kinetic, and EMG analyses, the objective was to determine which design more effectively stabilizes lower limb mechanics, sustains propulsion consistency, and supports balanced muscle recruitment over prolonged exertion. Findings from this study are expected to guide targeted clinical prescriptions, contribute to optimizing orthotic design for hallux valgus patients, and enhance functional recovery strategies in rehabilitation settings, ultimately improving mobility, comfort, and long-term joint health.
Design
A repeated-measures within-subject design enrolled 15 adults with mild to moderate hallux valgus (mean age 23±2.5 years), confirmed by X-ray and 3D foot scanning. Participants completed treadmill walking and fatigue trials in randomized conditions: medial forefoot wedge, arch support, and normal insoles, separated by standardized rest. Lower limb kinematics, joint moments, ground reaction forces (GRF-X: lateral stability; GRF-Y: propulsion/deceleration; GRF-Z: vertical support), and electromyographic activity of key muscles were recorded using a 3D motion capture system synchronized with force plates and EMG sensors. Data were analyzed via repeated-measures ANOVA with post-hoc paired t-tests. Individual differences and pre-test activity were controlled, and all equipment was calibrated to ensure reliability. The laboratory-based design provided robust short-term biomechanical data but had limited generalizability due to modest sample size.

Results
The medial forefoot wedge showed superior biomechanical stability for hallux valgus patients, especially under fatigue. It maintained knee joint moment variation within ±3%, reduced mediolateral GRF fluctuation to ±3.5% (vs. ±9.8% arch support, ±6.7% normal), and improved forward propulsion with GRF-Y variation at ±4.2% (vs. ±11.3%, ±9.1%). Vertical load support stayed below 5% under fatigue, outperforming others.

Kinematically, it preserved knee–hip and ankle–hip coordination post-fatigue, with only slight push-off adjustments. Arch support showed increased post-fatigue knee valgus (~5.2°), irregular joint trajectories, and imbalanced muscle activation. Normal insoles suffered greater GRF variability, reduced coordination, and unstable gait patterns.

Overall, the medial forefoot wedge maintained kinetic/kinematic stability, minimized GRF fluctuations, and supported balanced muscle activation, making it the optimal choice for hallux valgus patients.
Conclusions
This study establishes that medial forefoot wedge insoles significantly outperform both arch support and normal insoles in preserving knee joint dynamics, minimizing GRF variability, and sustaining propulsion efficiency under fatigue in individuals with hallux valgus. Arch support insoles offer moderate benefits but may exacerbate joint angle changes under fatigue, potentially impairing gait stability. Normal insoles performed worst, underscoring the necessity for condition-specific orthotic interventions.

The findings support medial forefoot wedge design as a preferred targeted prescription for hallux valgus patients, especially for activities involving prolonged or high-intensity gait cycles. Future work should expand sample sizes, investigate long-term effects, and explore adaptive insole technologies to further optimize biomechanical outcomes and fatigue resistance in foot deformity populations.