Maxillomandibular advancement (MMA) or orthognathic surgery, also sometimes called bimaxillary advancement (Bi-Max), or maxillomandibular osteotomy (MMO), is a surgical procedure or sleep surgery which moves the upper jaw (maxilla) and the lower jaw (mandible) forward.The procedure was first used to correct deformities of the facial skeleton to include malocclusion. In the late 1970s advancement of the lower jaw (mandibular advancement) was noted to improve sleepiness in three patients. Subsequently, maxillomandibular advancement was used for patients with obstructive sleep apnea.