Radial polydactyly: putting together evolution, development and clinical anatomy

Evolutionary developmental pathology, a new biological field, connects the study of evolution, development and human pathologies. In radial polydactyly, traditional studies have focused mainly on skeletal anomalies. This study examines anatomical and operative records of 54 consecutive cases of radial polydactyly to investigate whether there is a consistent spatial correlation between muscles, tendons and bones and whether this reflects a link between the mechanisms that generate these structures. The data are explored in the context of two current models of limb development: the modularity and topology models. Autopod (hand) tendons and muscles are more predictable in terms of insertion site, supporting both topology and modularity models. Zeugopod (forearm) tendons are less predictable. Neither model universally predicts the anatomy in radial polydactyly. These observations provide evidence for the complexity of anatomy in radial polydactyly and the difficulty in predicting operative findings based on the level of skeletal duplication alone.