title: Validation of in vivo assessment of facial soft-tissue volume changes and clinical application in midfacial distraction: a technical report.
abstract: The purpose of this study was to validate the assessment of visible volume changes of the facial soft tissue with an optical three-dimensional sensor and to introduce new parameters for the evaluation of the soft-tissue shape achieved from three-dimensional data of selected cases of midfacial distraction. Images of a truncated cone of known volume were assessed repeatedly with an optical three-dimensional sensor based on phase-measuring triangulation to calculate the volume. Two cubic centimeters of anesthetic solution was injected into the right malar region of 10 volunteers who gave their informed consent. Three-dimensional images were assessed before and immediately after the injections for the assessment of the visible volume change. In five patients who underwent midfacial distraction after a high quadrangular Le Fort I osteotomy, three-dimensional scans were acquired before and 6 and 24 months after the operation. The visible soft-tissue volume change in the malar-midfacial area and the mean distance of the accommodation vector that transformed the preoperative into the postoperative surface were calculated. The volume of the truncated cone was 235.26 +/- 1.01 cc, revealing a measurement uncertainty of 0.4 percent. The injections of anesthetic solution into the malar area resulted in an average visible volume change of 2.06 +/- 0.06 cc. The measurement uncertainty was 3 percent. In the five patients, the average distance of maxillary advancement was 6.7 +/- 2.3 mm after 6 months and 5.4 +/- 3.0 mm after 2 years. It was accompanied by a mean visible volume increase of 8.92 +/- 5.95 cc on the right side and 9.54 +/- 4.39 cc on the left side after 6 months and 3.54 +/- 3.70 cc and 4.80 +/- 3.47 cc, respectively, after 2 years. The mean distance of the accommodation vector was 4.41 +/- 1.94 mm on the right side and 4.74 +/- 1.32 mm on the left side after 6 months and 1.62 +/- 1.96 mm and 2.16 +/- 1.52 mm, respectively, after 2 years. The assessment of visible volume changes by optical three-dimensional images can be carried out with considerable accuracy. The determination of volume changes and accompanying accommodation vectors completes the cephalometric analysis during the follow-up of patients undergoing midfacial distraction. The new parameters will help to assess normative soft-tissue data on the basis of three-dimensional imaging with a view to an improved three-dimensional prediction of the operative outcome of orthognathic surgery.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Univesity of Erlangen-Nuremberg, Germany. emeka.nkenke@mkg.imed.uni-erlangen.de
authors.forename: Emeka
authors.initials: E
authors.lastname: Nkenke
authors.forename: Astrid
authors.initials: A
authors.lastname: Langer
authors.forename: Xavier
authors.initials: X
authors.lastname: Laboureux
authors.forename: Michaela
authors.initials: M
authors.lastname: Benz
authors.forename: Tobias
authors.initials: T
authors.lastname: Maier
authors.forename: Manuel
authors.initials: M
authors.lastname: Kramer
authors.forename: Gerd
authors.initials: G
authors.lastname: Häusler
authors.forename: Peter
authors.initials: P
authors.lastname: Kessler
authors.forename: Jörg
authors.initials: J
authors.lastname: Wiltfang
authors.forename: Friedrich Wilhelm
authors.initials: FW
authors.lastname: Neukam
mesh_terms: D000293:Adolescent; D000328:Adult; D002508:Cephalometry; D002648:Child; D005145:Face / Q000033:anatomy & histology*; D005147:Facial Bones / Q000002:abnormalities*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008297:Male; D008437:Maxilla / Q000002:abnormalities* / Q000601:surgery*; D019857:Osteogenesis, Distraction; D019340:Osteotomy, Le Fort / Q000534:rehabilitation; D010781:Photography / Q000295:instrumentation* / Q000379:methods