Finite element study of the role of medial longitudinal arch in hallux valgus deformity

A better understanding of the function of the medial longitudinal arch (MLA) in hallux valgus (HV) may guide medical management strategies. The current study recreated 3D finite element foot models to assess the change in joint and soft-tissue stress in the MLA associated with different severities of HV. This study aimed to evaluate the relationship between flatfoot deformity (FFD) and HV.

All bones, cartilage, the plantar fascia (PF), the spring ligament (SL), the lateral and medial ligaments, the tibiofibular syndesmosis, posterior tibial tendon (PTT), and other tendons around the ankle were included, considering their anatomical distribution and biomechanical characteristics. The FE models, including the normal, mild, and severe HV with the PF attenuation, were constructed simulating flexible FFD. The foot plantar pressure distribution, the equivalent stress on the joint's articular surface of the MLA, and the maximum principal stress of the medial ligaments in the ankle were evaluated.

The plantar pressure distribution in the medial foot area increased with the severity of HV, and it elevated while combined with MLA collapse. The stress in the first metatarsal shaft and phalanx decreased, while the other metatarsal shafts and phalanxes increased with the severity of HV. The equivalent stress of all the joints in the MLA increased when the MLA collapsed in HV. All the medial ligaments increased when the MLA collapsed in HV.

These findings support the correlation between HV and FFD. A better understanding of the association between HV and FFD could lead to novel approaches for therapeutic management and prevention of disease progression. Future research should evaluate different levels of HV severity and investigate other intrinsic factors contributing to HV.