ObjectiveTo discuss the effectiveness of free croin flap in repairing defects of donor after toe or feet tissue flap transplantation. MethodsBetween March 2010 and May 2015, 23 cases of defects of donor after toe or feet tissue flap transplantation were repaired with free croin flap and followed up for more than 6 months, and the clinical data were retrospectively analyzed. There were 15 males and 8 females, with an age range from 17 to 52 years (mean, 25.6 years). All finger or soft tissue defects were caused by trauma. Defects were repaired in emergency operation with toe or feet tissue flap transplantation in 18 cases, defects were secondarily reconstructed at 3-8 months after injury in 5 cases. The defect area at the feet donor site ranged from 3 cm×3 cm to 10 cm×6 cm, all accompanied with exposure of bone, and tendon. The area of free croin flap was 3.5 cm×3.5 cm-11.0 cm×6.5 cm, the vessel of flap was anastomosed with artery and vein of foot. The inguinal donor site was sutured directly. ResultsThe operation time was 3-9 hours (mean, 4.5 hours); the intraoperative blood loss was 50-300 mL (mean, 120 mL). Vessel crisis occurred in 1 case postoperatively; mild and moderate swelling occurred in 3 cases, with small sporadic blisters formation; free croin flap survived completely in the other cases, and primary healing was obtained at feet wound and inguinal donor sites. Twenty-three cases were followed up 6-24 months (mean, 9 months). The color and texture of the croin flaps were similar to that of the adjacent skin, no obvious scar contracture and pigmentation were observed; the patient could walk with weight loading, the two-point discrimination was 18-35 mm (mean, 26 mm) at 6 months after operation. The color, texture, and shape of reconstructed finger was good; the function of grasping and pinching recovered well; the two-point discrimination was 5.5-11.0 mm (mean, 6.5 mm) at 6 months after operation. According to upper extremity functional evaluation standard by Chinese Medical Association, the results were excellent in 18 cases and good in 5 cases. ConclusionFree croin flap can effectively repair skin and soft tissue defects of donor after toe or feet tissue flap transplantation, and good function and appearance of feet can be obtained.