The most common of these defects include those deformities associated with Down's Syndrome or other similar trisomies. Single gene or Mendelian defects may include upper extremity developmental anomalies that have resulted from specific inherited traits passed from one generation to the next. Many of these congenital limb defects have no known etiology. Some are felt to be a result of a combination of both environmental and genetic factors. The development of the upper extremity progresses through multiple stages beginning with the formation of the small arm bud 26 days after conception.
Further development includes are bud enlargement, neurovascular ingrowth, and cartilage formation.
By the 33rd day, the hand appears as a paddle which forms a basis for individual, separated digits through the death of interdigital tissue by the 54th day. The upper limb is completely formed by the eighth week. Most limb deformities must occur during this early period of rapid embryological development. At The Indiana Hand Center the treatment goal for children with congenital hand deformities is to enhance their upper limb function. Not all children require reconstructive surgery.