Analyzing the morphological and functional changes of the temporomandibular joint (TMJ) post L-shaped reduction malarplasty. And evaluating the surgical safety.

The female cosmetic patients who underwent L-shaped reduction malarplasty in the Department of Maxillofacial Surgery, Plastic Surgery Hospital, Chinese Academy of Medical Sciences from December 2015 to March 2019 were recruited as the study object. Three-dimension models of pre-operation and post-operation were created by the analysis of computed tomography (CT) data via Materialise ProPlan CMF 3.0. Seventeen groups of data relating to the length and angle of the TMJ were measured in the axial plane, coronal plane and sagittal plane. These measurements included condylar anteroposterior diameter in the axial plane and condylar anterior space, superior space and posterior space in the sagittal plane. Data were analyzed via SPSS 22.0 statistical software.

Thirty female cosmetic patients who underwent L-shaped reduction malarplasty were included. Patient age ranged from 21 to 36 years and the mean age was (26.19±4.08) years. Fifteen patients were less than 25 years old, and other fifteen patients were more than or at least 25 years old. The condylar anteroposterior diameter post-operation was significantly longer than pre-operation in the axial plane [(9.406±1.241) mm vs.(9.259±1.276) mm], and the difference was (0.146±0.388) mm. The condylar anterior space, superior space and posterior space post-operation were all significantly smaller than pre-operation in the sagittal plane [(1.080±0.537) mm vs.(1.193±0.533) mm/(1.598±0.591) mm vs.(1.907±0.755) mm/(1.239±0.568) mm vs.(1.670±0.926)mm], and the differences were (0.113±0.409) mm, (0.309±0.711) mm, and(0.431±0.786) mm, respectively. Other thirteen measurements showed none significant differences when compared to pre-operation and post-operation (P>0.05).

L-shaped reduction malarplasty could trigger slight morphological changes to the TMJ. However the TMJ could adapt these changes and reach to a new balance due to compensated adaptation. The normal physiological function would not be impacted. Surgery itself could be considered as a safe contour cosmetic surgery.

L-shaped reduction malarplasty; Temporomandibular joint; Occlusal function; Compensated adaptation; Digital technology