Increased horizontal angle of the mandibular condyle in abnormal temporomandibular joints. A magnetic resonance imaging study.

The horizontal condylar angle was measured in axial magnetic resonance images of normal and abnormal temporomandibular joints (TMJs). The average condylar angle in the normal joints was 21.2 degrees. In joints with disk displacement with reduction it was 29.7 degrees; joints with disk displacement without reduction, 33.5 degrees; and in joints with degenerative joint disease, 36.5 degrees. There were statistically significant differences between all four groups. Thus the condylar angle seemed to be increasingly larger with more advanced pathologic changes related to internal derangement and degenerative disease in the joint. The reason for the larger condylar angle in the abnormal joint was unclear. Joints with a larger condylar angle might have a greater tendency for internal derangement and degenerative joint disease to develop. Another possible explanation could be that remodeling associated with internal derangement and degenerative joint disease might result in a larger condylar angle. Further studies with longitudinal observations are needed to determine whether a causal relationship exists between the changes of the joint and a large condylar angle.