Analysis of condylar positioning in the temporomandibular joint following mandibular reconstruction: Introduction of a new classification system and assessment of influencing factors on displacement.

Objective: This study investigates the unsatisfactory outcomes observed in mandibular reconstruction procedures attributed to improper condylar positioning in the Temporomandibular Joint. It also proposes a systematic classification for post-reconstruction condylar positioning dissatisfaction.

Methods: A retrospective analysis was conducted on 337 patients who underwent tumor removal and mandibular reconstruction with vascularized osteocutaneous flaps. Reconstruction techniques included conventional surgery (43.3%) and 3D technology-guided procedures (56.7%). Evaluation utilized preoperative and postoperative CT scans to assess mandibular vertical ramus length (V) and condylar alignment in both sagittal (S) and coronal (C) planes. Accordingly, a classification system for condylar positioning was developed and abbreviated as VSC. It includes four classes: Class I, proper condylar reconstruction; Class II, short ramus length; Class III, one or two aspects of sagittal/coronal condylar positions dissatisfaction; and Class IV, two or three aspects dissatisfaction.

Results: The overall success rate for condylar reconstruction was 85.16%. Though not statistically significant, the success rate was marginally higher in the 3D-assisted group (85.86%) compared to the conventional group (84.25%). In terms of the VSC classification, the distribution of cases across Class I, II, III, and IV were 287, 4, 9, and 37 cases, respectively. Notably, condylar dislocation was significantly associated with the defect site, particularly the body and condyle (p < 0.001, OR = 49.734, 95% CI 12.995-190.342), and the number of reconstructed segments (p = 0.025, OR = 3.480, 95% CI 1.173-10.328).

Conclusion: The findings highlight the importance of accurate reconstruction methods and reveal implications of the defect site and the number of reconstructed segments in condylar dislocation. Consequently, we propose a classification system to refine condylar positioning assessment and enhance surgical outcomes in mandibular reconstruction.