Analysis of the morphologic differences of the second toe and digits of the hand, and evaluation of potential surgical intervention to minimize the differences using computer-aided design technology.

Abstract

Toe "narrow neck" augmentation and pulp-plasty are two aesthetic surgical refinements that are performed to minimize the visual differences between the transferred toe and digit following a second toe-to-hand transfer. To improve the aesthetic refinements in a second toe transfer, the authors investigated the real shape of the flap and factors affecting the flap design using computer-aided design technology. The plaster models of the right first through fourth digits and right second toes from 20 volunteers were scanned by spiral computer tomography to obtain three-dimensional reconstruction data. Computer-aided design software was used to analyze the data and simulate narrow neck augmentation and pulp-plasty. Next, the three-dimensional shapes of the transferred and excised flaps were created by Boolean calculation. The simulated transferred flaps were classified into two types in terms of their shape: crab claw and cross. The simulated excised pulp flaps could also be divided into two types-water drop and elliptic. There were individual variations and gender differences in the second toe morphology that resulted in different flap shapes. The flap shapes in narrow neck augmentation and pulp-plasty were determined using the location of the palmar protruding part and contour of the distal margin of the toe tip, respectively. Accurate three-dimensional shapes of the flap could be obtained by computer-aided design, and there were individual variations and gender differences. The authors suggest that the affected factors should be considered, and computer-aided design could be used to improve the accuracy of flap design before surgery.