Progressive condylar resorption after mandibular advancement.

Progressive condylar resorption is an irreversible complication and a factor in the development of late skeletal relapse after orthognathic surgery. We have evaluated cephalometric characteristics, signs and symptoms in the temporomandibular joint (TMJ), and surgical factors in six patients (one man and five women) who developed it after orthognathic surgery. The findings in preoperative cephalograms indicated that the patients had clockwise rotation of the mandible and retrognathism because of a small SNB angle, a wide mandibular plane angle, and a "minus" value for inclination of the ramus. There were erosions or deformities of the condyles, or both, on three-dimensional computed tomography (CT) taken before treatment. The mean (SD) anterior movement of the mandible at operation was 12.1 (3.9)mm and the mean relapse was -6.4 (2.5)mm. The mean change in posterior facial height was 4.5 (2.1)mm at operation and the mean relapse was -5.3 (1.8)mm. Two patients had click, or pain, or both, preoperatively. The click disappeared in one patient postoperatively, but one of the patients who had been symptom-free developed crepitus postoperatively. In the classified resorption pattern, posterior-superior bone loss was seen in three cases, anterior-superior bone loss in two, and superior bone loss in one. Progressive condylar resorption after orthognathic surgery is multifactorial, and some of the risk factors are inter-related. Patients with clockwise rotation of the mandible and retrognathism in preoperative cephalograms; erosion, or deformity of the condyle, or both, on preoperative CT; and wide mandibular advancement and counterclockwise rotation of the mandibular proximal segment at operation, seemed to be at risk. The mandible should therefore be advanced only when the condyles are stable on radiographs, and careful attention should be paid to postoperative mechanical loading on the TMJ in high-risk patients.