Polydactyly of the foot: an analysis of 265 cases and a morphological classification.

Three hundred and thirty feet in 265 patients with polydactyly of the foot were classified on the basis of ray involvement and the level of duplication. Anatomic differences in bony structures according to x-ray and operative findings, external appearance of involved digits, associated anomalies, and familial incidence were studied. In medial-ray polydactyly, bilateral occurrence was common, and a higher frequency of associated anomalies was detected. Each involved foot with even the same level of duplication usually had a different morphologic pattern. In central-ray polydactyly, all patients except one had duplications of the second toe, commonly with unilateral involvement. Both components were underdeveloped, with delay in appearance of ossification areas. In two patients, each member of duplication had syndactyly with the neighboring toe, resembling the pattern of polysyndactyly-cleft hand complex. Lateral-ray polydactyl was classified into two new major groups based on ossification pattern and bony alignment: (1) fifty-ray duplication, referring to the medially duplicated supernumerary fifth toe, and (2) sixth-ray duplication, referring to the laterally duplicated supernumerary sixth toe. Fifth-ray duplication was much more frequent than sixth-ray duplication in the Japanese population. Many differences were noted between the two groups of lateral polydactyly. Syndactyly between the fourth and fifth toes was associated only with fifty-ray duplication. Ulnar polydactyly was associated only with sixth-ray duplication. In lateral polydactyly, every patient with bilaterally involved feet had similar groups of polydactyly bilaterally. All the patients in the same family also had similar groups of anomalies. These facts suggest independent etiologic mechanisms for each.