Morphologic and radiographic characterization of fibular dimelia.

Fibular dimelia accompanied by complete tibial agenesis is a rare developmental anomaly that has been reported in the anatomic and clinical literature as both a dimelia and a diplopodia. Previous reports have offered variable descriptions of structural aberration and possible modes of altered embryologic development. We present a clinical and radiographic history of the progressive development of this anomaly, and a detailed postsurgical dissection and histopathologic examination. The specific mirroring of the separate components in this case has not been previously reported, and suggests that a reestablishment of limb polarity may have occurred during embryogenesis. Our detailed morphologic investigation strongly suggests a central role for the mesenchymal precursor from which chondro-osseous morphology subsequently emerges, and the relevance to establishing muscular attachments.