Computed tomographic features of synovial chondromatosis of the temporomandibular joint with a few small calcified loose bodies.

Objectives: The present study aimed to clarify the characteristic computed tomography (CT) features that indicate synovial chondromatosis (SC) with a few small calcified bodies or without calcification on panoramic images, and to discuss their differences from the features of temporomandibular disorder (TMD).
Methods: Panoramic and CT images from 11 patients with histologically verified SC of the temporomandibular joint were investigated. Based on the panoramic images, the patients were classified into a distinct group (5 patients) with typical features of calcified loose bodies and an indistinct group (6 patients) without such bodies. On the CT images, findings for high-density structures suggesting calcified loose bodies, joint space widening, and bony changes in the articular eminence and glenoid fossa (eminence/fossa) and condyle were analyzed.
Results: All 5 distinct group patients showed high-density structures on CT images, while 2 of 6 indistinct group patients showed no high-density structures even on soft-tissue window CT images. A significant difference was found for the joint space distance between the affected and unaffected sides. A low-density area relative to the surrounding muscles, suggesting joint space widening, was observed on the affected side in 2 indistinct group patients. All 11 patients regardless of distinct or indistinct classification showed bony changes in the eminence/fossa with predominant findings of extended sclerosis and erosion.
Conclusion: Eminence/fossa osseous changes including extended sclerosis and erosion may be effective CT features for differentiating SC from TMD even when calcified loose bodies cannot be identified.