Type III dysplasia of the thumb presents with dysplasia of the metacarpal portion of the thumb, especially the proximal part of the metacarpal. The median and ulnar nerves innervate the greater trochanteric muscles, which are significantly affected, and this is accompanied by limited motion of the metacarpophalangeal joints and interphalangeal joints, leading to significant hypoplasia and instability of the thumb, as well as a thin and small appearance. In type IV dysplastic thumb, also known as floating thumb, there is no metacarpal bone or only remains of metacarpal bone, which is connected to the palm by a loose skin tube, and the size of the thumb varies considerably, but it is mostly located at the radial or distal end. Compared with the two, the thumb dysplasia of IV is more severe in both appearance and intrinsic anatomical abnormalities, and more difficult to operate on. In the beginning, such a thumb could not be preserved, and it could only be excised and then moved to the thumb position to be used as a thumb, i.e., bunionization of the thumb. After the operation, the child was left with only four fingers, which was unacceptable to many parents, as they considered five fingers to be sound. Under this demand, the metatarsal reconstruction to preserve the five fingers was proposed, which takes part of the metatarsal bone from the child’s foot to reconstruct the first metacarpal bone, so that the thumb, which originally lacks the metacarpal bone, can have a better shape. The postoperative results were fine and did preserve the five fingers, but since the bone was taken from the foot, there was some chance of bone resorption and necrosis when reconstructing the first metacarpal. Even if the metatarsal reconstruction surgery is successful, the child’s foot will still have new scars, and wearing sandals in the summer will not be very aesthetically pleasing. Moreover, the foot has to bear weight for a long period of time, and removing the bone from the foot will have some impact on the child. Although all surgeries have certain risks and trauma cannot be avoided, we hope to minimize the chances of bone resorption and necrosis, and make the postoperative trauma less traumatic, so that the child will suffer less. After years of research and clinical practice, we have realized a method of treating floating bunions with semimetacarpal bone graft reconstruction (SMRT Floating Bunion Reconstruction). In other words, a portion of the second metacarpal bone is taken from the affected hand to rebuild the first metacarpal bone, which has a much lower chance of bone resorption and necrosis. On the other hand, since the first metacarpal is reconstructed from the affected hand, there is no additional trauma to other parts of the body and the impact of the surgery is minimized. Most importantly, the hemimetacarpal bone grafting technique can help advance the age of surgery to around 6 months to 1 year, which is the age when the child’s thumb is being established, and with the floating bunion cured, the child’s thumb can be established without being forced to develop the habit of using the index and middle fingers to hold objects. In the clinic, I often come across some big children with floating bunions. Since they cannot use their thumbs for a long period of time, they have developed the habit of pinching objects with their index and middle fingers, and they rely on pinching to write and hold things in their daily life, which will deform their index fingers over time. Therefore, if possible, we suggest that the child should undergo surgery earlier.