A Case Report of Congenital Hallux Valgus from an Incomplete Preaxial Polydactyly without a Supernumerary Digit

INTRODUCTION: While hallux valgus is a common deformity occurring in adults and adolescents, congenital hallux valgus is rare. There is a paucity of information available about the deformity and even less information about its cause. In fact, discrepancies exist within literature as to its etiology. This is a case report of bilateral congenital hallux valgus that appears to have been caused by preaxial polydactyly of the great toe, without a supernumerary digit, which to date has not been reported in literature. Markedly increased intermetatarsal and hallux valgus angles were present in both feet. Furthermore, bilateral interval improvement of the angulation occurred spontaneously without operative or non-operative intervention. This case reveals another potential cause of congenital hallux valgus not previously described. Our patient demonstrates that preaxial polydactyly could be another possible etiology of congenital hallux valgus. This case also demonstrates that magnetic resonance imaging (MRI) may be required for accurate diagnosis. CASE REPORT: The subject of this case report is a 6-month-old boy who presented with what appeared to be severe bilateral congenital hallux valgus. However, an MRI was suggestive of preaxial polydactyly without a supernumerary digit. At 26 months of age, clinical follow-up demonstrated that the deformity had improved and the patient was doing well clinically without intervention. CONCLUSION: Congenital hallux valgus is an uncommon deformity. Our patient demonstrates that the etiology may be incomplete preaxial polydactyly without a supernumerary digit. Overtime, even without treatment, the deformity appeared to improve, and the patient had no clinical complaints. The lack of an accessory ossicle or supernumerary digit makes our patient’s case unique.