Visual and statistical modeling of facial movement in patients with cleft lip and palate

Abstract

Objective: To analyze and display facial movement data from noncleft subjects and from patients with cleft lip and palate by using a new dynamic approach. The hypothesis was that there are differences in facial movement between the patients with cleft lip and palate and the noncleft subjects.

Setting: Subjects were recruited from the University of North Carolina School of Dentistry Orthodontic and Craniofacial Clinics.

Patients, participants: Sixteen patients with cleft lip and palate and eight noncleft "control" subjects.

Interventions: Video recordings and measurements in three dimensions of facial movement.

Main outcome measures: Principal component (PC) scores for each of six animations or movements and dynamic modeling of mean animations.

Statistics: Multivariate statistics were used to test for significant differences in the PC mean scores between the patient groups and the noncleft groups.

Results: No statistically significant differences were found in PC mean scores between the patient groups and the noncleft groups; however, the variability of the effect of clefting on the soft tissues during animation was noted when the noncleft data were used to establish a "normal" scale of movement. Compensatory movements were seen in some of the patients with cleft lip and palate, and the compensation was not unidirectional.

Conclusion: Measures of mean movement differences as summarized by PC scores between patients with cleft lip and palate and noncleft subjects may be misleading because of extreme variations about the mean in the patient group that may neutralize group differences. It may be more appropriate to compare patients to a noncleft normal scale of movement.

Figures

FIGURE 1

A grid of 38 landmarks on the facial and circumoral regions was established relative to the following landmark locations. 1 and 7, right and left lateralciliary points located above most lateral aspect of eyebrows; 2 and 6, right and left superciliary points located above most superior aspect of eyebrows; 3 and 5, right and left interciliary points located above medial aspect of eyebrows; 4, midnose point located on midline of nasal bridge in line with medial canthi; 8 and 10, right and left lateral alar points located on lateral alar rims; 9, nasal tip point located on the tip of the nose in the facial midline; 11 and 12, right and left commissure points located on the right and left commissures; 13 and 14, right and left upper-lip points located on peaks of Cupid’s bow; 15, mid–lower-lip point; and 16, midchin point located 2 cm below point 15.

FIGURE 2

Relative increase in a landmark-pair distance during a smile animation. Five phases of movement: 1 = at-rest phase, 2 = movement phase to the maximum position, 3 = holding phase at maximum position, 4 = relaxation movement phase from the maximum position, and 5 = at-rest phase. Transition times are represented by points a, b, c, and d.

FIGURE 3

Selected relative change from rest for a smile. Left: 13 to 14 (upper lip). Center: 4 to 5 (eyebrow). Right: average of pairwise distances. Transitions selected are shown by the broken lines.

FIGURE 4

B-spline basis functions corresponding to transitions in Figure 3. Knot locations are shown on the horizontal axis. Note the zero values at the two endpoints.

FIGURE 5

Schematic providing a flow chart and summary of the steps in both the numerical and the graphical analyses.

FIGURE 6

Plots of PC1, PC2, and PC3. For each animation, the baseline scale and quartiles were based on the noncleft PC scores. Each patient’s scores, numbered 1 to 16, were then superimposed on the noncleft scale for comparison. CP = cheek puff; GR = grimace; LP = lip purse; MO = mouth opening; NS = natural smile; SM = smile.

FIGURE 6

Plots of PC1, PC2, and PC3. For each animation, the baseline scale and quartiles were based on the noncleft PC scores. Each patient’s scores, numbered 1 to 16, were then superimposed on the noncleft scale for comparison. CP = cheek puff; GR = grimace; LP = lip purse; MO = mouth opening; NS = natural smile; SM = smile.