ObjectiveTo investigate the operative method of repairing soft tissue defect of the thumb with modified radial dorsal fasciocutaneous flap and its effectiveness.MethodsBetween June 2015 and December 2016, 15 patients with volar or dorsal defects of the thumb were treated with modified radial dorsal fasciocutaneous flaps which distal pedicles were cut off. Of 15 cases, 11 were male and 4 were female, aged 35-70 years (mean, 46 years). The causes of injury included crush injury in 12 cases and avulsion injury in 3 cases. Because all patients had volar or dorsal defects of the thumb which were accompanied by tendon or bone exposure, they had no condition or desire to replant. There were 12 cases of volar defect of thumb and 3 cases of dorsal defect. The area of defects ranged from 2.0 cm×1.2 cm to 3.0 cm×2.5 cm. The time between injury and operation was 16 hours to 2 days (mean, 30.4 hours). The radial dorsal fascio-cutaneous flaps of 2.3 cm×1.5 cm to 3.3 cm×2.8 cm in size were adopted to repair defects. The donor sites were directly sutured.ResultsAll flaps survived, and no severe swelling or tension blister occurred. The donor sites and wounds healed by first intention. All patients were followed up 3-12 months (mean, 6 months). The color and texture of the grafted flaps were similar to those of normal skin, with no bloated appearance. According to total active motion standard at last follow-up, the finger function was excellent in 8 cases and good in 7 cases.ConclusionModified radial dorsal fasciocutaneous flap of the thumb is a reliable flap with easy dissection and less trauma in repair of soft tissue defects of the thumbs, and satisfactory clinical outcome can be obtained.