Objective:To explore the effect of hallux nail flap design assisted with 3D printing in reconstruction of thumb defect in degloving injury.Methods:From January 2020 to March 2022, 16 patients with thumb defect caused by degloving injury with intact digit flexor and extensor tendons were treated. The patients were 11 males and 5 females, aged 20 to 52 years old, with an average age of 31 years old. The injured patient's hands were firstly scanned by CT and the 3D models were created to map the profile of the tissues required for reconstruction. Photopolymer templates for the defects in thumb were then 3D printed. The printed templates were put on the great toes and accordingly the hallux nail flaps were designed and harvested. The degloving wound of thumb was repaired by the hallux nail flap. Donor sites were repaired with artificial dermis in 6 patients and with ilioinguinal flaps in 10 patients. The effect of surgery was observed at outpatient clinic during postoperative follow-up. The survival of the hallux nail flap and the recovery of the donor site were observed. Function recovery were evaluated according to the Evaluation Standard of Finger Replantation and Reconstruction of Hand Surgery Society of Chinese Medical Association.Results:All the harvested hallux nail flaps matched with the profiles of recipient sites. All the hallux nail flaps survived over 4 to 30 months of follow-up, in an average of 16 months. Appearance of all hallux nail flaps was similar to normal thumbs, with good fingerprint and nails. Sensation recovery were S 3-S 4, with TPD at 4-7 mm. According to the Evaluation Trial Standards of Upper Limb Partial Functional of Hand Surgery of Chinese Medical Association, 15 thumbs were excellent and 1 was good. Conclusion:Application of 3D printing assisted hallux nail flap transfer in reconstruction of defect of thumb in degloving injury can precisely design and harvest the required tissue and minimise a damage to the donor great toe. It improves the appearance of thumb as well as patient satisfaction. It is practical in reconstruction of the defect of thumb in degloving injury.