Three-dimensional analysis of changes of the malar-midfacial region after LeFort I osteotomy and maxillary advancement.

AIM

It has been the objective of the present prospective study to assess visible volume changes of the facial soft tissue after LeFort I osteotomy with advancement and to determine the soft-tissue-to-hard-tissue ratios of advancement.

PATIENTS AND METHODS

Twenty adult patients (ten female, ten male, mean age 33.9 +/- 14.9 years) received a LeFort I osteotomy with advancement because of a maxillary protrusion. Lateral skull radiographs and optical three-dimensional (3D) scans of the facial surface were assessed preoperatively and 12 months after surgery. The lateral skull radiographs were used to carry out standard linear and angular cephalometric measurements. The pre- and postoperative optical 3D surface scans were registered. A well-defined area in the malar region was used to determine the visible volume changes for each side separately. The mean accommodation vector that transforms the preoperative into the postoperative surface was assessed for each facial half separately. The soft-tissue-to-hard-tissue ratios between the incision superius and the labrale superius, the maximal parasagittal advancement of soft tissue, and the accommodation vectors were calculated.

RESULTS

A mean advancement of the incision superius of 5.3 +/- 2.1 mm was accompanied by a volume increase of 5.2 +/- 4.1 cm(3) in the right malar-midfacial region and 4.6 +/- 4.7 cm(3) on the left side, respectively, revealing a symmetrical volume change (p = 0.370). The soft-tissue-to-hard-tissue ratios were 80 +/- 94% for labrale superius and incision superius, 56 +/- 79% (right) and 51 +/- 56% (left) for accommodation vector and incision superius and 97 +/- 79% (right) and 98 +/- 89% (left) for maximal parasagittal advancement of soft tissue and incision superius.

DISCUSSION

The determination of volume changes and accompanying accommodation vectors complete the cephalometric analysis during the follow-up of patients undergoing LeFort I osteotomy. The data show that maxillary advancement leads to a more pronounced shifting of the soft tissues in the malar-midfacial area than of the upper lip. The new parameters will help to assess normative soft tissue data based on 3D imaging with a view to an improved three-dimensional prediction of the operative outcome of orthognathic surgery away from the midline.