Abstract:[Objective] To introduce the surgical technique and preliminary clinical outcomes of the tendon-bone graft harvested from the fifth metacarpal base used for repair composed defect of the proximal phalangeal base. [Methods] A total of 6 patients received surgical repair for composed defect of proximal phalangeal base. As the X-ray examination was conducted to measure the area of the bone defect at the proximal phalangeal base preoperatively, osteotomy was designed on the fifth metacarpal base. A longitudinal incision was made on the dorsal side of the fifth metacarpocarpal joint with protection of the dorsal branch of the ulnar nerve, and then the tendon-bone graft with part of the extensor carpi ulnar tendon and the base of the fifth metacarpal was cut according to the osteotomy designed preoperatively. Fi- nally, the graft was trimmed to meet the phalangeal base defect, implanted on the receipt site and fixed with Kirschner wires or screws. [Results] All patients had operation completed successfully without serious complications, such as vascular and nerve injury, whereas with the stable and painless repaired metacarpophalangeal joints after operation. The fracture healing of receipt site achieved from 2.7 to 3.4 months on the standard of X-ray, with a stable donor fifth metacarpocarpal joint. At the latest follow-up lasted for 6~12 months, the clinical out- comes were marked as excellent in 4 cases and good in 2 cases according to the hand function criteria of Hand Surgery Society of Chinese Medical Association. [Conclusion] The tendon-bone graft harvested from the fifth metacarpal base is effectively used to repair the com- posed osteochondral defect, involving the extension tendon insertion, on the proximal phalanx base.