Background Polydactyly of the foot is one of the most frequent anomalies of the limbs.However, most classification systems are based solely on morphology and tend to be inaccurate and lessrelevantto surgical methods and results. The purpose ofthisstudy isto presentour newclassification of polydactyly ofthe foot,which can serve as a predictor oftreatmentand prognosis.Methods To find a correlation between the various morphologic traits of polydactyly ofthe foot and the treatment plan and outcomes,we reviewed 532 cases of polydactyly ofthefoot in 431 patients treated in our hospital, expanding on our previous study that describedpolydactyly based on the importance of metatarsal bone status and varus deformity. Therecords of patientswere evaluated and comparedwith previousstudies at other centers.Results Unsatisfactory results were seen in 36 cases, which included 5 cases of incompleteseparation due to syndactylism, 23 cases of axis deviation, and 8 cases ofremnants of extradigit metatarsal bones. The locus of the polydactyly, or the digit which wasinvolved, did notseemto affectthe final postoperative outcomesin ourstudy. Three factorssyndactylism, axisdeviation, and metatarsal extensionare the major factors related to treatment strategy andprognosis. Therefore,we developed a newclassification systemusing three characters(S,A,M)followed by three groups(0, 1, 2),to describe the complexity of polydactyly ofthe foot,suchas S1A2M2.Conclusions Our newclassification could provide a communicable description to help determine the surgical plan and predict outcomes
