Method: The sample consisted of Cone-Beam Computed Tomography (CBCT) scans of 36 patients. The across subject comparisons included 12 controls, mean 41.3 ±12.0 years, and 12 patients with temporomandibular joint osteoarthritis, (TMJ OA) mean 41.3 ± 14.7 years. The individual longitudinal assessments included 12 patients with TMJ OA, mean 37.8 ±16.7 years, followed at pre-operative jaw surgery, immediately after and one-year post-operative. Surface models of all condyles were constructed from the CBCT scans. Two previously calibrated observers independently performed all registration methods. A landmark-based approach was used for registration of across subject condylar models, and TMJ OA versus control group differences were computed with shape analysis. A voxel-based approach used for registration of longitudinal scans calculated x, y, z degrees of freedom for translation and rotation. Two-way random intraclass correlation coefficients (ICCs) tested the inter-observer reliability.
Result: Statistically significant differences between the control group and the OA group were consistently located on the lateral and medial poles for both observers. The inter-observer differences were ≤ 0.2 mm. For individual longitudinal comparisons, the mean inter-observer differences were ≤ 0.6mm in translation errors and 1.2° in rotation errors, with excellent reliability (ICC >0.75).
Conclusion: Condylar registration for across subjects and longitudinal assessments is reliable, and can be used to quantify subtle bony differences in the 3D condylar morphology.