Embryology

Abstract

Developmental biology has greatly contributed to the understanding of upper limb development. Whereas early understanding of limb development centered on morphological change during organogenesis, current emphasis is on discovery of molecular signaling mechanisms that drive the remarkable transformation of single cells into fully functioning limbs and the human body. These discoveries have laid a foundation for fundamental embryology-based concepts that have reshaped the way congenital limb differences are conceptualized, with the ability to trace a phenotype back to single genes, and, conversely, the ability to predict developmental differences from single-gene mutations. Not only do these discoveries advance understanding of limb development, but clinical benefits are also realized. Clinicians are provided with the information they need to adequately inform patients and their families about the nature of limb differences, the hereditary implications, and the downstream developmental needs and challenges that the patient may face. Pediatric upper limb surgeons, standing at the interface between clinical care and genetic research, play a unique role in this field. Through recognition of novel human variants, pediatric upper limb surgeons act as gatekeepers by referring patients for appropriate work-up, facilitating research that offers novel insights into human limb development. The goal of the discussion that follows is to provide the pediatric upper limb surgeon with the fundamentals of limb embryology that have implications both clinically and academically.