Floating thumb is actually type 4 thumb hypoplasia, where the thumb lacks the metacarpal bones and has a floating thumb. There are two types of thumb dysplasia, type 4 and type 5, and if the pregnancy test determines that the baby has only four metacarpals, one of these two types may be suspected. However, in the actual pregnancy test, the baby’s hand may be blocked and not visible due to the uncontrollable movement and state of the baby, and it will not be checked. If the baby is found to have a floating thumb after birth, parents should not be too anxious. There are currently two surgical options for floating thumb to preserve the fifth finger, metatarsal reconstruction and hemimelia reconstruction, although I personally prefer the latter. Metatarsal reconstruction is to take the metatarsal bone of the foot to reconstruct the first metacarpal, while hemimelia reconstruction is to take part of the bone from the second metacarpal to reconstruct the first metacarpal, which is the biggest difference between the two surgical approaches. This is the biggest difference between the two surgical methods. Because of the different places where the bone is taken, there is a big difference in the chance of bone resorption, necrosis, and the impact on the baby’s life in the future. The metatarsal bone reconstruction is to reconstruct the first metacarpal bone in the hand using part of the metatarsal bone of the foot, and the metatarsal bone transplanted in the past may be absorbed or necrotic. In contrast, hemi-metacarpal bone graft is used to reconstruct the bone on the second metacarpal bone adjacent to the first metacarpal bone, so the chance of bone resorption and necrosis is greatly reduced. 2, the difference in the impact on the baby’s future life, because the floating thumb is missing the metacarpal bone, so we prefer to operate only on the hand, rather than to destroy other parts of the baby’s body, because taking the metatarsal bone will bring some scars on the foot, the baby grows up to wear sandals will not be beautiful, and after all, it is moving the bones of the foot, more or less will cause some impact on the foot.