Cleft Skeletal Asymmetry: Asymmetry Index, Classification and Application.

OBJECTIVE: To quantitatively measure the extent of 3D asymmetry of the facial skeleton in patients with unilateral cleft lip and palate (UCLP) using an asymmetry index (AI) approach, and to illustrate the applicability of the index in guiding and measuring treatment outcome.

METHOD: Two groups of subjects between the ages of 15 and 20 who had archived CBCT scan were included in this study. Twenty-five patients with complete UCLP were compared with 50 age-matched noncleft subjects. The CBCT scans were segmented and landmarked for 3D anthropometric analysis. An AI was calculated as a quantitative measure of the extent of facial skeletal asymmetry.

RESULTS: For the control group, the AI ranged from 0.72 ± 0.47 at A point to 4.77 ± 1.59 at Gonion. The degree of asymmetry increased with the increasing laterality of the landmark from the midsagittal plane. In the UCLP group, the values of AI significantly increased compared to the control group at nearly all measured landmarks. The extent of the asymmetry to involve the upper, middle, and lower facial skeleton varied widely with the individual patient with UCLP.

CONCLUSION: The asymmetry index is capable of capturing the 3D facial asymmetry of subjects with UCLP and as a basis for classification of the extent of the asymmetry. We found the index to be applicable in surgical planning and in measuring the outcome in improving the symmetry in patients who have undergone orthognathic surgery.