Radiographic characteristics of epiphyseal ossification centres of the thumb in patients with radial polydactyly.

This study aimed to evaluate the radiographic characteristics of the epiphyses (secondary ossification centres) in patients with radial polydactyly (RP). Radiographs of 2108 children with RP (2300 thumbs) were retrospectively reviewed. The pathoanatomy of the polydactyly was correlated with the radiographic characteristics of the epiphyseal ossification centres on plain radiographs and compared with the normal children population. The epiphyses of the thumb in patients with RP ossify sequentially from the distal phalanx, proximal phalanx and metacarpal (26 months, 36 months and 37 months, respectively), and their appearance is delayed compared with children with normal anatomy (15 months, 18 months and 25 months, respectively) (p < 0.001). Anatomical features, gender, polydactyly degree and age were found to be associated with epiphyseal ossification of the thumb in general. However, anatomic features of polydactyly such as ulnar deviation of the interphalangeal joint were found to correlate with atypical distal phalanx epiphyses in 5.5% of cases, which may delay surgery until the thumb is large enough for corrective osteotomy in cases of hypertrophic epiphysis.Level of evidence: III.