Surgical advancement of the retrognathic mandible in growing children

Orthodontists and surgeons may occasionally decide that there are compelling reasons for correcting a retrognathic mandible surgically before facial growth is completed. The literature implies that there will be no untoward effects. This study on twenty-two growing children demonstrated that there are severe growth disturbances after surgery. The response varied with the amount of surgical correction: Type A cases (those advanced more than 10 mm.) showed either resorption of the condyle, bizarre bony outgrowths in the posterior symphysis, or both. Relapse may continue in these cases for several years. Once condylar resorption occurred, there was no recovery. Type B cases (those advanced less than 9 mm.) had a milder response. Even in Type B cases, however, there was no clinically significant increase in mandibular length subsequent to surgery. There is a one-year recovery period, after which further growth and remodeling of the condyle are directed (if our hypothesis is correct) towards achieving an equilibrium of forces and a return to the preoperative growth pattern. We found that movement of the Y point (intersection of the posterior surface of the symphysis with the inferior border of the mandible) reflected a stable growth pattern prior to surgery and returned to the same pattern, usually within 2 years after surgery.