To investigate the effect and application value of transplantation of the free cutaneous fibular flap combined with antibiotic-loaded calcium sulfate artificial bone graft for the treatment of antibrachial chronic osteomyelitis of Cierny-Mader type IV. Methods From August, 2013 to May, 2017, 12 cases of ulna or (and) radius chronic osteomyelitis of Cierny-Mader type IV were treated by transplantation of the free cutaneous fibu-lar flap combined with antibiotic-loaded calcium sulfate artificial bone graft. There were 7 males and 5 females, with an average age of 36.3 (21-47) years.Pure ulnar osteomyelitis in 7 cases, radius osteomyelitis in 4 cases, and both ul-nar and radius osteomyelitis in 1 case. The average range of osteomyelitis lesions was 6.3 (3.0-9.0) cm. The area of soft tissue defect (including bone scar) ranged from 8.0 cm×2.0 cm to 15.0 cm×5.0 cm. The area of the flap was 10.0 cm×3.5cm-17.0 cm×7.0 cm.The average length of the fibular flap was 8.8 (5.0-12.0) cm.Locking plate internal fixa-tion was used in 9 cases, external fixator in 2 cases, and plate combined with external fixator in 1 case. Vancomycin/gentamicin, an effective component of calcium sulfate artificial bone, averaged 0.64 g/102.7 kU (0.4 g/64 kU-1.0 g/160 kU).Routine postoperative treatment.And monthly outpatient review in the first half year after operation, and outpatient review every 3 months after half a year.One year after operation, comprehensive evaluation of elbow, forearm and wrist function with Mayo Elbow Function Index, Anderson Forearm Double Fracture Evaluation System and Cooney Wrist Function Score. Results Vascular crisis occurred in 1 case after operation, prompt surgical exploration, and ultimately all flaps survived completely.The donor sites healed well in all cases.The lower extremity functions of donor sites had no change compared with that before operation.Followed-up of an average of 22.7 months, there were 2 cases who had sen-sory disturbance in the ulnar nerve innervation area and returned to normal 3 months after operation. The fibular flaps healed satisfactorily with an average healing time of 4.7 (3-6) months.No calcium sulphate artificial bone granules were seen on X-ray at 3 months after operation.One year after operation, bone healing, forearm appearance and wrist function recovered well, but elbow and forearm motor function recovered unsatisfactorily. Conclusion On the basis of master-ing the applied anatomy and vascular anastomosis techniques of microsurgery, this method of transplantation of the free cutaneous fibular flap combined with antibiotic-loaded calcium sulfate artificial bone graft for the treatment of an-tibrachial chronic osteomyelitis of Cierny-Mader type IV has achieved satisfactory results.The recipient area is beautiful. The bone healing is reliable.And it has little influence on the recipient area and the donor area.It is worthy of clinical application.