This little girl was polydactyly and developed a secondary deformity after surgery at an outside hospital, and when she came to us we found that there was significant lateral deviation of the thumb. The reason for the lateral deviation was twofold: first, the interphalangeal joint was not adjusted during the first surgery, and second, the stopping point of the flexor tendon of the thumb was not adjusted. The stopping point of the flexor tendon of this little girl’s retained thumb rests on the lateral side of the thumb, not on the palmar side of the thumb in a median position, so it should have been corrected at the time of the surgery, and if it was not corrected, the lateral deviation would have easily occurred after the surgery. After seeing such a situation, we told the little girl’s mother about the idea of the surgery, and the parents understood very well, so we performed the surgery according to this idea. During the surgery, what we saw was consistent with the preoperative prediction, so the little girl’s postoperative recovery was relatively satisfactory. The only problem is that the flexion of the thumb has not reached a completely normal angle, which is related to the development of the thumb joint and the overall structure of the thumb, but this problem does not have a great impact on the functionality of the thumb, so we do not need to intervene excessively and let the thumb move normally and continue to grow and develop. If there are problems in the future, we will address them then.