Objective: Thumb placement index >0.55
Subjective: The base of the thumb appears closer to the wrist than is typical
The technique for the thumb placement index is described in detail [Malina et al., ; Hall et al., ]. Briefly, the thumb placement index is the distance from the proximal crease of the index finger to the angle of the first interdigital space divided by the distance from the proximal crease of the index finger to the wrist flexion crease at the base of the thumb. This term should not be used with Preaxial polydactyly.