Extremely proximal fractures of the fifth metatarsal in the developmental age.

BACKGROUND: Numerous studies document the high incidence of this type of fracture of the foot in childhood due to the presence of the growth plate of the apophysis of the fifth metatarsal. Our aim in this study was to evaluate the presence and morphology of the growth nucleus and correlate its presence with fractures of the apophysis of the fifth metatarsal.

MATERIALS AND METHODS: Between 2001 and 2003, we reviewed the radiographs of 481 patients (558 feet) between 6 months and 16 years that were diagnosed with a fracture. We evaluated for the presence and morphology of the growth nucleus of the base of the fifth metatarsal in the 7- to 16-year age group because this is the time interval in which the nucleus becomes visible radiographically.

RESULTS: We identified the nucleus of the base of the fifth metatarsal in 115 patients for a total of 132 feet. A fracture of the fifth metatarsal was found in 12.8%. A misdiagnosis had been made in 47%. Misdiagnosis was strictly related to the presence of the growth nucleus of the apophysis except two cases where an accessory bone was present.

CONCLUSIONS: Our study demonstrated a much higher incidence of the presence of the growth nucleus than documented in previous reports and that its morphology varied widely in relation to the stage of maturity of the patient and the radiographic technique. Its presence led to a high rate of misdiagnosis of a fracture.