Complex tibia nonunions and defects caused by tumor, trauma, and congenital abnormality are difficult to treat. The tibiofibular synostosis procedure is a treatment option. Fifteen patients with complex diaphyseal tibia fractures (4 segmental, 11 comminuted; 10 open, 5 closed) were managed with this procedure. Mean time between injury and procedure was 20.3 weeks. Mean healing time was 16 weeks (acceptable); 14 of 15 cases showed healing by final follow-up (36 months). At final follow-up, each patient's knee range of motion (ROM) and ankle ROM were acceptable. Knee ROM varied from full extension to 150 degrees of flexion for 13 patients and from full extension to 120 degrees of flexion for 2 patients. Ankle dorsiflexion ranged from 0 degrees to 40 degrees for 10 patients, from 0 degrees to 30 degrees for 3 patients, and from 0 degrees to 20 degrees for 2 patients. There were no radiographic arthritic changes in any case. The tibiofibular synostosis procedure is effective in treating complex nonunions and defects.