| The foot is an essential component for human gait and begins the propagation of forces in the lower extremity of the body. One of the most common conditions that produce forefoot pain is hallux valgus (HV). HV alters or restricts normal body kinematics, influences physical mobility and increases the risk of falling. The root cause of HV has not been fully determined. While the principal kinematics are known and understood, the etiology still remains unclear. Clinically standard planar radiographs are employed but cannot accurately capture first metatarsal pronation, which is known to occur in the onset of hallux valgus. Previous research has also shown changes occur in bone density near the midfoot of cadavers with hallux valgus. Plantar pressure models have shown patients with hallux valgus have increased loading at the big toe and metatarsal head. In this study, we analyzed the forefoot of normal and HV patients to measure in vivo density and bone orientation. We also developed patient specific threedimensional finite element models of the first and second rays of the foot to develop predictions of stress on the metatarsal in the progression of the HV. We found changes in the density profile in patients with hallux valgus. We quantified pronation in the first metatarsal and found differences in the patients with hallux valgus. The pronation reported here is the first true three-dimensional measurement of metatarsal rotation due to the hallux valgus deformity. We found differences in contact forces at the metatarsal head and metatarsal base due to hallux valgus. This study is the first to report an estimate of pressure at the metatarsal sesamoid interface. We found increased pressure due to the altered kinematics as a result of HV, which can lead to pain and erosion at the metatarsal head. |
