Mandibular dysmorphology in patients with unilateral cleft lip and cleft palate.

BACKGROUND: Conventional studies of the cleft lip/palate (CLP) dysmorphology have mainly focused on deformities of the lip, nose, and maxilla, while ignoring the mandible. Reasons for that were the lack of well-defined mandibular deformity and restriction from the research methodology. METHODS: This study used 3-dimensional computed tomography (CT) imaging data from 35 patients with unilateral CLP. The 3-dimensional images were rotated into a neutral position. Eight cephalometric landmarks were recorded: the pogonion (PG) and the infradentale (ID) from the frontal view; and the condylion (CO), the tip of coronoid process (CP), and the gonion (GO) from both sides of lateral views. The nasion was used as a reference point for the facial midline. Nine linear distances and four angular measurements were calculated from these landmarks. Each mandible was segmented into two hemi-mandibles for volume measurements. The image manipulation and measurements were performed using a personal computer running Analyze' program. Landmark deviation from the facial midline was computed, and comparisons were made between the cleft and non-cleft sides. RESULTS: The results showed that the precision and accuracy of landmark localization was high with an average error of 0.4%. Deviation from the midline of the ID and PG points, and spatial distances between bilateral CP, CO, and GO points varied without a specific pattern. The average differences were within 2 mm. The volume of the cleft side hemi-mandible was consistently larger than that of the non-cleft side (p < 0.0001). Among linear and angular measurements, CP-GO-PG, CO-ID, CP-ID, and CP-GO showed significant difference between the two sides. CONCLUSION: This study demonstrated that mandibular asymmetry and deformity existed and was measurable in patients with unilateral CLP. The influence of CLP to the mandibular development was expressed by the significant differences of hemi-mandible volume and some of the linear and angular measurements between the cleft and non-cleft sides.