We investigated the role of first metatarsal head shape in the etiology of hallux valgus. By pedobarographic analysis, we evaluated whether first metatarsal head shape causes an alteration in plantar pressure values that would result in metatarsalgia.
Referrals to our clinic for metatarsalgia, plantar fasciitis, and calcaneal spur were scanned retrospectively. Patients with severe hallux valgus, pes planus, gastrocnemius stiffness, generalized joint laxity, neuromuscular disease, or a history of lower-extremity orthopedic surgery were excluded. Sixty-two patients with plantar pressure assessment and radiographic evaluation were included. These patients were invited for reassessment after 10 years. Feet were divided into three groups by metatarsal head shape: round, square, and chevron. On anteroposterior radiographs, the hallux valgus and intermetatarsal angles, relative first metatarsal length, lateral sesamoid subluxation, and presence of bipartite sesamoid were noted. Plantar pressure was assessed with pedobarography.
Feet with round-shaped first metatarsal heads had a statistically significantly greater progression in hallux valgus angle than the other shapes. Plantar pressures under the first, second and third, and fourth and fifth metatarsals increased with time. This can explain the mechanism of transfer metatarsalgia and painful callosities under the first metatarsal in hallux valgus. There was no correlation between hallux valgus angle, relative metatarsal length, and lateral sesamoid subluxation.
We found a strong relation between round-shaped first metatarsal head and hallux valgus angle progression. No patients had a risk factor responsible for hallux valgus. In other words, this study gives approximately 10-year natural history results in nearly normal feet.