Oblique osteotomy and coronoidectomy in extreme prognathism of Apert syndrome.

We report a case of oblique osteotomy and coronoidectomy for correction of extreme prognathism in Apert syndrome.A 16-year-old girl presented with a prognathic mandible. A prototype model was formed using computed tomography. After a mock bilateral oblique osteotomy of the mandible, the distal segment did not overlap the proximal segment, and it caused bony impingement between the coronoid process and the subcondyle of the proximal segment. An oblique osteotomy of the mandible was done through a submandibular approach, and bilateral coronoidectomy followed. After surgery, mandibular parameters were reviewed. The mandibular plane-Frankfort horizontal (MP/FH) angle decreased from 44 to 11 degrees; and the mandibular plane-sella nasion (MP/SN) angle, from 52 to 17 degrees. The mandible rotated backward and caudally after the surgery.It is predictable that there will be a bony impingement between the coronoid process and the subcondyle of the proximal segment before surgery, and so an oblique osteotomy and coronoidectomy are planned ahead through an external approach.