Correlation Between Condylar Displacement and Remodeling Changes Following Orthognathic Surgery
Objectives: This study investigated whether condylar-displacement changes after counterclockwise maxillomandibular advancement and disc-repositioning surgery (CMMA-Drep) may predict condylar-remodeling in the follow-up period.
Methods: 75 condyles from 41 female patients treated with CMMA-Drep had cone beam computed tomography (CBCT) scans taken pre-surgery, immediately after surgery and, on average, 16 months post-surgery. Pre- and postsurgical 3D models were superimposed using automatic voxel-based registration on the cranial base to evaluate condylar displacements after surgery, and regional registration to access condylar remodeling in the follow-up period. Shape correspondence analysis (SPHARM-PDM) was applied to quantify the changes. Statistical framework included Pearson product–moment correlations to identify the relationship between condylar translational/ rotational displacement changes and condylar remodeling.
Results: Weak statistically significant associations were observed between the magnitude of condylar displacement and remodeling changes in the follow-up period. Upward condylar displacement correlated with greater condylar resorption at the posterior pole (r=0.26, p≤.05). Lateral and anterior condylar displacement correlated with greater condylar resorption at the lateral (r=0.3, p≤.01) and anterior poles (r=0.29, p≤.05), respectively. Lateral roll and medial yaw correlated with greater condylar resorption at the posterior (r=-0.26, p≤.05) and lateral poles (r=-0.26, p≤.05), respectively. On average, CMMA-Drep causes the condyles to translate slightly downward (1mm ± 1.3), medially (1.5mm ± 1.8) and rotate in a medial (medial roll, 5.2° ± 7.3), lateral (lateral yaw, 4.5° ± 6.0), and counterclockwise direction (upward pitch, 7.5° ± 8.0).
Conclusions: Displacement changes generated by CMMA-Drep did not seem to be associated with greater condylar resorption in the follow-up period. Such changes showed, on average, opposite direction from the ones correlated with greater risk of condylar resorption. Moreover, positional changes were only weakly associated with remodeling in the follow-up period, suggesting that other risk factors may play a role in condylar resorption.