Soft tissue response in orthognathic surgery patients treated by bimaxillary osteotomy: cephalometry compared with 2-D photogrammetry

Abstract

Purpose: Since improvement of facial aesthetics after orthognathic surgery moves increasingly into the focus of patients, prediction of soft tissue response to hard tissue movement becomes essential for planning. The aim of this study was to assess the facial soft tissue response in skeletal class II and III patients undergoing orthognathic surgery and to compare the potentials of cephalometry and two-dimensional (2-D) photogrammetry for predicting soft tissue changes.

Material and methods: Twenty-eight patients with class II relationship and 33 with class III underwent bimaxillary surgery. All subjects had available both a traced lateral cephalogram and a traced lateral photogram taken pre- and postsurgery in natural head position (median follow-up, 9.4 ± 0.6 months).

Results: Facial convexity and lower lip length were highly correlated with hard tissue movements cephalometrically in class III patients and 2-D photogrammetrically in both classes. In comparison, cephalometric correlations for class II patients were weak. Correlations of hard and soft tissue movements between pre- and postoperative corresponding landmarks in horizontal and vertical planes were significant for cephalometry and 2-D photogrammetry. No significant difference was found between cephalometry and 2-D photogrammetry with respect to soft to hard tissue movement ratios.

Conclusions: This study revealed that cephalometry is still a feasible standard for evaluating and predicting outcomes in routine orthognathic surgery cases. Accuracy could be enhanced with 2-D photogrammetry, especially in class II patients.

Fig. 1

Hard and soft tissue landmarks and reference lines for tracing cephalograms. N nasion, S sella, A point A, B point B, L1 lower incisor, U1 upper incisor, Gn gnathion, Pg pogonion, ANS anterior nasal spine, Pn pronasale, Sn subnasale, Ls labrale superius, Li labrale inferius, Si labiomental sulcus, Pg′ soft tissue pogonion, RF HOR horizontal reference line, RF VER vertical reference line

Fig. 2

Soft tissue angles and distances for tracing cephalograms and photograms. 1 Facial convexity, 2 nasolabial angle, 3 labiomental angle, 4 upper lip length, 5 lower lip length

Fig. 3

Soft tissue landmarks and reference lines for tracing photograms. TV true vertical, TH true horizontal, Trg tragus. Further abbreviations as given in Table 1

Fig. 4

Screenshots of traced lateral photograms. Pre- to postsurgical changes of lower lip length (LL) and labiomental angle (LM) in class II patients (a presurgery and b postsurgery) and changes of facial convexity (FC) in class III patients (c presurgery and d postsurgery) revealed high significance