Cutting the bone is called osteotomy and in case of performing the surgery on the two jaws at the same time it is called a bi-maxillary osteotomy (two jaws bone cutting) or a maxillomandibular advancement. The bone cutting is traditionally done using special electrical saws and burs, and manual chisels. Recently a machine that can make the bone cuts using ultra-sound waves has been introduced; this is yet to be used on a wide scale. The maxilla can be adjusted using a "Lefort I" level osteotomy (most common). Sometimes the midface can be mobilised as well by using a Lefort II, or Lefort III osteotomy. These techniques are utilized extensively for children suffering from certain craniofacial abnormalities such as Crouzon Syndrome