Medical imaging in management of mandibular asymmetry

Abstract

Mandibular asymmetry secondary to unilateral condylar hyperplasia (UCH) or asymmetric mandibular hyperplasia (AMH) is common in Hong Kong. The aims of this study are to investigate the roles of medical imaging (single-photon emission computed tomography (SPECT) and conebeam CT (CBCT)) in: (1) investigation of the condylar activity in mandibular asymmetry secondary to UCH and AMH; (2) surgical planning in patients presented with complex asymmetry; and (3) evaluation of the association between asymmetry and patients’ quality of life (QoL) and psychosocial well-beings, and the changes at 1-year after surgery. (1a) A retrospective study on mandibular asymmetry by planar scintigraphy was performed in 109 patients to compare UCH and AMH. (1b) A prospective study on a separate 62 patients with UCH or AMH to compare the condylar activities of each side using SPECT scintigraphy. The quantitative analysis included condylar activity percentage (CA%) and condylar activity ratio (CAR). (1c) 21 patients with valid cone-beam CT (CBCT) data were selected for correlation analysis with the scintigraphic findings. The results from the 3 studies are summarized as follows: A significant difference in CA% between UCH and AMH in both planar and SPECT scintigraphy. Serial analysis of the scintigraphic data in patients with initially active mandibular asymmetry showed an increase in CAR followed by reduction once the asymmetry had become inactive, while CA% percentile difference showed minimal change. The serial change in CAR was corresponding to the change in condylar activity. Correlation analysis revealed significant association between scintigraphic activity and condylar dimensions. Obvious difference was found between UCH and AMH: UCH showed differences in condylar dimensions and posterior ramus height; and AMH showed morphological differences between the left and right posterior ramus including condyles but without non-significant difference in dimension. (2) An new treatment strategy was developed for patients with complex mandibular asymmetry with the use of steroemodel planning and surgical navigation. A case was used to illustrative this technique achieving excellent result. This combination has greatly facilitated the correction of complex mandibular asymmetry with severe occlusal disharmony . (3) Thirty-two patients who were ready for surgical correction of mandibular asymmetry were recruited for evaluation of the patients’ reported outcome measures. The evaluation was conducted before surgery, 1- & 6- week, 3-, 6- and 12-month after surgery using a set of self-administered quality of life and psychosocial questionnaires including SF-36, OHIP-14, Orthognathic Quality of Life (OQLQ), Hospital anxiety and depression scale (HADS), Satisfaction with life scale (SWLS) and Hope scale. 20 patients with valid pre-surgical CBCT were selected for the correlation analysis. Results showed that patients with mandibular asymmetry were more anxious, depressed and had poor QoL. CT correlation analysis revealed both dental midline deviation and occlusal canting had significant association with OHIP, OQLQ and HADS. Surgical correction could bring significant improvement of QoL (in OHIP 14 and OQLQ) but not the psychosocial well-beings.