A 3D Morphology Index of TMJ OA

Method: Cone beam CT (CBCT) scans were acquired for clinical purposes for 28 patients with long-term history TMJ OA (39.9 ± 16 years), 12 patients at initial consult diagnosis of OA (47.4 ± 16.1 years) and 11 healthy controls (41.8 ± 12.2years) recruited through advertisement. All participants underwent a comprehensive exam by an oral and maxillofacial pain specialist and a diagnosis of healthy, OA, or indeterminate was made using the research diagnostic criteria. These CBCT datasets were used to construct 3D models of the condyles for each healthy control and OA subject. 3D Shape Correspondence was used to establish homologous correspondent points on each model. The statistical framework included a multivariate analysis of covariance corrected for false discovery rate at 0.05, and Direction-Projection-Permutation (DiProPerm) for testing statistical significance of the healthy control and the OA group determined by clinical and radiographic diagnoses.

Result: Condylar morphology in OA and healthy subjects varies widely.  The OA average model was smaller in all dimensions except its anterior surface, with the areas of statistically significant largest variance indicative on bone resorption being localized along the articular surface, particularly in the lateral pole. 1000 permutation statistics (i.e., t-stat = 7.2114) of DiProPerm support a significant difference in the healthy control group and the OA group with empirical p-value = 0.0016.

Conclusion: This study has expounded the present knowledge regarding the morphologic variability in TMJ OA and elucidated that even at initial diagnosis the condylar lateral pole already presents osteoarthritic destruction and the anterior surface of the condyle presents reparative bone apposition.  This new evidence will aid the development of more targeted statistical classifications of this condition than previously possible.