Ulnar-Sided C-shaped Composite Flap of the Index Finger for Replantation of Avulsed Thumb

Background: To evaluate the clinical outcomes of a C-shaped composite flap harvested from the ulnar aspect of the index finger for reconstruction of thumb avulsion amputations with associated soft-tissue defects. Methods: A retrospective review was conducted of 12 patients with thumb avulsion amputations accompanied by soft-tissue defects who were treated between January 2023 and June 2025. All patients underwent one-stage reconstruction using an ipsilateral ulnar index finger C-shaped composite flap to simultaneously restore arterial circulation, sensibility, and soft-tissue coverage. Flap survival, postoperative complications, and functional outcomes were assessed during follow-up. Results: The patients were followed up for 12 to 24 months, with a mean of 16.5 months. All replanted thumbs and composite flaps survived. At the final follow-up, the mean static 2-point discrimination (S2PD) was 7.8 mm. The mean total active motion (TAM) ratio of the replanted thumbs was 83% compared with the contralateral side. The mean Disabilities of the Arm, Shoulder and Hand (DASH) score was 11.5, and the mean Michigan Hand Outcomes Questionnaire (MHQ) score was 86.8. No major donor-site complications were observed during follow-up. Conclusions: By simultaneously restoring vascular continuity, sensibility, and soft-tissue coverage while preserving thumb length, this technique achieves satisfactory functional and aesthetic outcomes without significant donor-site morbidity.