Unilateral hallux valgus: is it true unilaterality, or does it progress to bilateral deformity?

BACKGROUND: This study was undertaken to determine whether unilateral hallux valgus progresses unilaterally and to evaluate the demographics, etiologies, and radiographic findings associated with symptomatic unilateral hallux valgus deformities. METHODS: Patients treated for hallux valgus between January 2004 and December 2008 were identified, and of these, 33 patients with unilateral deformities were enrolled. Progression of deformities in normal feet were evaluated at last follow-up visit, and the clinical information and radiographic measurements of those with a deformed normal foot or an unchanged normal foot were compared. RESULTS: Thirty-three patients (3.4%) had a unilateral hallux valgus deformity on preoperative radiographs. The mean length of follow up was 4.7 years (range, 2.4-11). Twenty-four cases had no deformity of the normal foot at last follow-up (the unchanged group), but 15 cases had developed hallux valgus deformity (the deformed group). No significant intergroup differences were found in terms of metatarsus adductus angle (P = .412), Meary angle (P = .771), talocalcaneal angle (P = 1.000), or calcaneal pitch angle (P = .267). However, members of the deformed group were significantly younger at disease onset (P = .045), exhibited a curved first metatarsal head (P = .046), and had a larger initial hallux valgus angle (P < .001). CONCLUSIONS: The frequency of bilateral symptomatic hallux valgus was found to be over 97.3%, and significant differences were found between the deformed and unchanged groups in terms of age of onset, metatarsal head shape, and hallux valgus angle.