Lateral Sesamoid Position Relative to the Second Metatarsal in Feet with and without Hallux Valgus.

To determine if the sesamoids migrate laterally in the feet with hallux valgus or if they only appear to move, maintaining their relationship with the other forefoot structures.  Anteroposterior radiographs of 80 patients (94 feet, all weight-bearing), from the period between 2015 and 2016, were evaluated. Forty-eight had a valgus hallux angle greater than 15° (hallux valgus group) and 46 presented a hallux valgus angle lower than 15° (control group). The distances from the first metatarsus head and the lateral sesamoid bone to the second metatarsus axis were measured. Subsequently, the coefficients of these distances were determined by the length of the second metatarsus to adjust it for different foot sizes.  Both the absolute and the relative measures from the first metatarsus head to the second metatarsus axis were significantly different between the groups, with a positive correlation with hallux valgus and intermetatarsal angles. However, neither the absolute nor the relative distance of the lateral sesamoid bone to the second metatarsus was different between the groups, as they did not correlate with hallux valgus or intermetatarsal angles.  Despite the medial deviation of the first metatarsus in hallux valgus, the sesamoid bone maintains its relationship with the second metatarsus in the transverse plane. This apparent lateral displacement may lead to misinterpretation of these radiographs. This fact is of paramount importance in the pre-, intra-, and postoperative period of patients with hallux valgus.