ObjectiveTo investigate the effectiveness of double osteotomy and lengthening of proximal phalanx and metacarpal with Ilizarov technique in treatment of thumb defect. MethodsBetween February 2017 and June 2019, 6 patients with traumatic thumb defects were treated with double osteotomy and lengthening of proximal phalanx and metacarpal by Ilizarov technique. There were 5 males and 1 female. The age ranged from 28 to 57 years, with an average of 41.5 years. There were 3 cases on the left side and 3 cases on the right side. All patients were admitted to the hospital in emergency department after injury, and the stump of the thumb was trimmed and sutured. The osteotomy plane was the distal part of the proximal phalanx in 4 cases and the interphalangeal joint in 2 cases. The interval between injury and osteotomy was 20-245 days (median, 34.5 days). After minimally invasive osteotomy and placement of a semi-circular external fixator, the lengthening began on the 5th day. The proximal phalanx and metacarpal were lengthened by 0.5 mm every day, once every 12 hours. The thumb of the affected side was distracted to the middle of the distal phalanx of the healthy thumb, and the fixator was removed after the bone healed. ResultsThe distraction time was 14-23 days, with an average of 18.8 days. The osteotomies were healed with healing time of 91-147 days (mean, 120.2 days). The total distraction length of the proximal phalanx and metacarpal was 1.40-2.25 cm, with an average of 1.86 cm; healing index was 51.0-72.2 days/cm, with an average of 64.9 days/cm. All patients were followed up 5-12 months (mean, 8.2 months). At last follow-up, the two-point discrimination was 5.3-8.5 mm with an average of 6.98 mm. According to the evaluation standard of the upper limb part of the Chinese Medical Association, the score was 10-14, with an average of 12.5. Among them, 4 cases were excellent and 2 cases were good, with an excellent and good rate of 100%. All patients were satisfied with the function and appearance of thumb after operation. The Quick Disabilities of Arm, Shoulder, and Hand (Quick-DASH) score was 2.3-9.1, with an average of 6.1. ConclusionThe double osteotomy and lengthening of proximal phalanx and metacarpal with Ilizarov technique is an effective method for the treatment of thumb defects.