Method: Twenty patients with clinical research diagnostic criteria of TMJ OA had CBCT scans taken for radiographic diagnosis of OA. Upon diagnosis, the treatment of choice was condylar resection and total joint prosthetic replacement. Construction of 3D models for the right and left condyles from CBCT datasets were performed with ITK-SNAP. After generating all 3D models, left condyles were mirrored to form right condyles. Registration among subjects used surface-to-surface rigid registration focused on the mandibular ramus region, as a reference structure to assess condylar morphological variability specifically tailored for computing a TMJ OA severity index. A 3D sample-based condylar morphology index was used to quantify the extension of bone defect, flattening, width, depth of erosions and bone overgrowth.
Result: Shape analysis assessed morphological variation between individual condylar models and the constructed sample-based composite. Color-coded maps showed the surface distance and differences vector between the individual and composite models. Individual comparisons of the TMJ OA condyles to the composite model revealed that 20% of the condyles had close to normal 3D morphology, 15% showed severe index of bone degeneration, 30% presented bone growth projections in the medial pole and flattening of the lateral pole, and the remainder of the condyles presented remarkable variability in the pattern of bone degeneration and/or proliferation.
Conclusion: A broad spectrum of condylar morphology was observed among patients who underwent TMJ total joint replacement. Supported by NIDCR DE 018962.