Objective:To compare the clinical effects between the homodigital radial flap of the dorsal cutaneous branch of radial palmar proper digital artery (PPDA) and the homodigital reverse island flap of the ulnar dorsal digital artery (DDA) on reconstruction of defects in thumb-tip or thumb-pulp.Methods:The retrospective case-control study method was used. From January 2016 to August 2022, a total of 65 thumb-tip or thumb-pulp defects were treated in the Department of Hand Surgery of the Second Hospital of Tangshan. Thirty-five defects of thumbs were reconstructed with the homodigital radial flap pedicled with dorsal cutaneous branch of radial PPDA (PPDA group) and the other 30 thumbs were treated by the homodigital ulnar reverse island flap pedicled with ulnar DDA (DDA group). Sizes of the wounds and flaps in PPDA group were 1.9 cm×1.5 cm to 2.9 cm×2.4 cm and 2.1 cm× 1.7 cm to 3.1 cm×2.6 cm, respectively, and the dimensions of the wounds and flaps in DDA group were 2.0 cm× 1.7 cm to 2.9 cm×2.5 cm and 2.2 cm×1.9 cm to 3.2 cm×2.8 cm, respectively. The wounds of donor site in both groups were all directly closed. Survival of the flaps and wound healing of donor sites were observed in both groups. The time of surgery and duration of follow-up of the 2 groups were recorded. Postoperative follow-up included outpatient clinic visits, telephone reviews and WeChat video-clips. At the final follow-up, record of total active motion (TAM) of the injured thumbs, angle of first web of the affected hands, static TPD of the flaps, patient satisfaction of the appearance of flaps and donor sites were taken. According to the Michigan Hand Function Questionnaire (MHQ) evaluation criteria, the patient satisfaction of the appearance of flaps and donor sites were evaluated. The measurement and count data acquired from both groups were compared by independent sample t-test and χ2 tests or Fisher's exact test, respectively. P<0.05 was considered statistically significant. Results:All 35 flaps in PPDA group and 26 flaps in DDA group survived primarily, except 4 flaps in the DDA group that showed blisters and healed with dressing changes. The primary survival rate of flap in PPDA group (100%) was higher than that of DDA group (87%), and the difference was statistically significant ( P<0.05). Donor sites of both groups healed primary. The time of surgery and duration of follow-up in PPDA and DDA groups were 59.11 minutes±5.42 minutes and 15.37 months±3.32 months, and 61.27 minutes±5.96 minutes and 16.17 months±3.60 months, respectively. There was no statistically significant difference between the 2 groups ( P>0.05). At the final follow-up, the thumb TAM and angle of thumb web in PPDA and DDA groups were 135.14°±10.04° and 90.29°±4.36° and 132.17°±11.04° and 89.00°±4.81°, respectively. There was no statistically significant differences between the 2 groups ( P>0.05). The static TPD, patient satisfaction of the appearance of flaps and donor sites in PPDA group were 7.11 mm±1.21 mm, 4.69 point±0.47 point and 4.43 point±0.50 point, which were better than DDA group [8.20 mm±1.47 mm, 4.40 point±0.50 point and 4.13 point±0.57 point, respectively] with a statistically significant difference ( P<0.05). Conclusion:The homodigital radial flap of the dorsal cutaneous branch of radial PPDA and the homodigital ulnar reverse island flap of the ulnar DDA are both suitable for reconstruction of defects in thumb-tip or thumb-pulp. Compared with the homodigital reverse island flap with the DDA, a homodigital radial flap with the dorsal cutaneous branch of PPDA has advantages in higher primary survival rate, better flap sensation and appearance at both of recipient and donor sites.