Measurement and evaluation of the alar base in unilateral secondary lip nasal deformities by three-dimensional computed tomography.

Objective : This study aimed to analyze the asymmetry of the pyriform aperture and alar base in patients with unilateral secondary nasal deformities by three-dimensional computed tomography (3D-CT). Methods : 3D-CT images of the subject group of 101 adult patients and of a control group of 65 normal adults were examined. Sixty-nine patients without alveolar bone grafting (ABG) were classified as Group A, and 32 patients with ABG were classified as Group B. Seven landmarks (INM, LPA, IPA, Gbase, Gsup, Glat, and Sbal) were measured for both the subject and control groups, and comparative analyses were done to assess the degree of asymmetry in the subject group. Results : For over 95% of Group A and 80% to 85% of Group B, the index of LPA and IPA showed asymmetry or marked asymmetry. The index of Gbase, Glat, Gsup, and Sbal showed symmetry for around 50% of Group A and about 60% of Group B. In Group A, dorsal, lateral, and caudal translocation was found on the cleft side in LPA and IPA, while all soft landmarks showed dorsal translocation. In Group B, caudal translocation was found in both LPA and IPA, but only LPA appeared dorsal on the cleft side, while Glat showed dorsal and caudal translocation. Conclusion : The results indicated that the degree of asymmetry of hard tissue landmarks far exceeded that of the soft tissue landmarks, and the degree of asymmetry of pyriform aperture was higher than expected for patients after ABG.