Are condylar head and neck inclinations associated with condylar volume changes following maxillomandibular advancement surgery?

The aim of this study was to analyse the association of condylar head and condylar neck inclination with condylar volume changes 2 years following maxillomandibular advancement surgery (MMA) for prediction purposes. A novel method for assessment of the condylar head and neck inclination from cone-beam computed tomography (CBCT) was proposed and its reliability was assessed. The intra- and inter-observer reliability of the method was excellent, intraclass correlation coefficient >0.99, with mean absolute differences ranging from 0.7 to 1.5°. Pre- and postoperative CBCT (2 weeks and 2 years) of 47 patients (31 female, 16 male; mean age 21.72 years) was assessed. The mean preoperative condylar head inclination in the right and left sides was 9.55 ± 9.62° (anterior) and 9.23 ± 10.51° (anterior), respectively, while the mean preoperative condylar neck inclination was -10.62 ± 6.81° (posterior) and -8.33 ± 8.07° (posterior), respectively. The condylar volumes showed a mean decrease in the right and left sides of 9.98 ± 21.14% and 11.14 ± 20.96%, respectively. Condylar neck inclination was identified as a statistically significant prediction factor for condylar volume loss (P = 0.004), while condylar head inclination was not (P = 0.42). Mandibular condyles with progressive condylar resorption had a significantly more posterior condylar neck inclination preoperatively compared to those without (P < 0.001). In conclusion, a more posteriorly inclined neck preoperatively was statistically significantly associated with a larger condylar volume loss 2 years following MMA. No statistically significant association between condylar head inclination and condylar volume loss was found.