Flatfoot in children and adolescents. Analysis of imaging findings and therapeutic implications.

INTRODUCTION: Pes planovalgus (PPV) is a complex three-dimensional deformity of which routine radiographs provide only a two-dimensional analysis.

HYPOTHESIS: Angles and other radiographic parameters of the foot in children and adolescents, when studied on both the dorsoplantar and the lateral view, can be used to establish a radiographic classification system for PPV that provides useful therapeutic guidance in clinical practice.

MATERIALS AND METHODS: A retrospective single-centre study was conducted on 65 feet in 35 patients aged 7 to 18 years and having adequate ossification. All patients had a clinical diagnosis of idiopathic or neurologic PPV and available weight-bearing dorsoplantar and strict lateral radiographs. We excluded pes planus due to tarsal coalition, congenital bone deformities, or overcorrection of talipes equinovarus (n=25). All possible axes were drawn and angles measured after an evaluation of interindividual agreement.

RESULTS: We identified four patterns of PPV: subtalar pes planus (n=16) with marked subtalar valgus and longitudinal sag predominating at the talonavicular joint, midtarsal pes planus (n=12) without subtalar valgus but with marked midtarsal abduction and sag predominating at the cuneonavicular joint, mixed pes planus (n=28) with subtalar valgus, midtarsal abduction, and sag at both the talonavicular and cuneonavicular joints, and pes planocavus (n=9) with sag of the medial arch and cavus deformity of the lateral arch.

CONCLUSION: This original classification system provides therapeutic guidance by helping to match the surgical procedure to the nature and location of the deformities.

LEVEL OF EVIDENCE: Level IV.