Nasolabial Volumetric Symmetry Following SARPE

Abstract

Surgically-assisted rapid palatal expansion (SARPE) widens the maxilla to correct transverse maxillary deficiencies; however, it also enlarges the nasal base, paranasal and cheek regions.Nasolabialvolume changes associated with SARPE theoretically follows its corresponding bony distraction. If transpalatal distraction is symmetrical, the related soft-tissue changes should also be symmetrical. Most studies quantifying symmetry in nasolabial volume focus on cleft patients rather than on orthognathic patients. The purpose of this study was to assess symmetry in the volumetric expansion of nasolabial soft tissue following SARPE using 3D stereophotogrammetry. Forty-three patients with an average age of twenty-four underwent SARPE by the same surgeon (LRC) between July 2006 and July 2010. Sixteen patients with pre- and postoperative 3D photography were included in this retrospective study. The standardized surgical protocol involved a combination of Le Fort I and paramedian osteotomies with pterygomaxillary separation as well as V-Y closure. Pre- and postoperative (at least six months postop) 3D photographs were captured in repose with 3dMDface™ System—a 3D stereophotogrammetric camera setup with an integrated software program modular system. Pre- and postoperative images of each patient were superimposed with a 3D editing software (3dMDpatient V3.0.1), using bilateral exocanthion as registration reference points. Nasolabial region measured was defined by reproducible surface landmarks. Volume differences of nasolabial soft tissue between the superimposed pre- and postoperative surfaces on both left and right sides were then individually computed by the 3D editing software. Non-parametric statistical analysis was performed. Within each patient's 3D photograph set, left or right volume changes were assigned to either “larger expansion group” or “smaller expansion group” based on the magnitude of expansion. Mann-Whitney U test was used to determine if the volume change of nasolabial soft tissue was significantly symmetrical. The range of volume change of nasolabial soft tissue due to SARPE ranged from +0.15 to +4.49 mm3. The mean volume changes in “larger expansion group” and “smaller expansion group” were 2.29 mm3 (SD 1.06 mm3) and 1.61 mm3 (SD 0.91 mm3), respectively. Mann-Whitney U test demonstrated that the volume change of nasolabial soft tissue was asymmetrical (U=77; P = .028). There was an asymmetrical volumetric expansion of nasolabial soft tissue following SARPE. Asymmetrical expansion of nasolabial soft tissue might be secondary to asymmetrical osteotomies, soft tissue management or palatal distractor placement. 3D stereophotogrammetry is a non-invasive, safe, and sensitive technique for evaluation of subtle surgically-induced facial volume changes.