High risk of falling in elderly with hallux valgus evaluated by muscle and kinematic synergistic analysis.

Background: Musculoskeletal disorders often present with abnormalities in neuromuscular control. Hallux valgus (HV) is considered a risk factor for falls in the elderly, and it is one of the foot conditions most associated with falls. The onset of falls is associated with neuromuscular modulation of the lower extremity. However, there is a lack of clarity regarding the muscle and kinematic synergy patterns i.e., neuromuscular control in elderly HV.

Research Question: How the changes in neuromuscular control in elderly HV based on muscle and kinematic synergies analysis?

Methods: The study included three groups: young controls (YC), elderly controls (EC), and elderly hallux valgus (HVE). All participants were assessed for gait at their natural walking speed. Data were analyzed using non-negative matrix factorization (NNMF) for electromyography (EMG) and joint motion to compare muscle and kinematic synergies across the groups. The center of plantar pressure (COP) was used to evaluate self-balancing ability.

Results: The EC group demonstrated the additional activation of calf muscle groups accompanied by decreased ankle motion and increased hip abduction. Compared to the EC group, the HVE group required more thigh flexor muscle groups to compensate for the lack of function of the ankle movements during gait and showed decreased hip abduction but increased knee flexion. During gait, the COP were significantly large than YC and EC groups (P < 0.05) in the HVE group.

Significance: Our finding indicate that the elderly individuals with hallux valgus exhibit under-activated calf muscles around foot joints, and despite compensations from thigh muscles, they maintain an imbalance and increased risk of falls. This study will help to evaluate HVE control strategies and provide personalized treatment based on these vulnerabilities to reduce the risk of HVE falls.