Purpose: The purpose of this investigation was to determine the prevalence of bone marrow signal abnormalities in patients referred for temporomandibular joint (TMJ) magnetic resonance imaging (MRI). This investigation was done because of prior studies suggesting that condylar marrow signal abnormalities indicate avascular necrosis.
Subjects and methods: Retrospective review was done of 449 consecutive TMJ MR examinations in 415 patients from 1991 to 1994. Examinations were obtained with a surface coil at 1.5 T with routine T1, T2, and T2* images. Condylar marrow signal abnormalities were reviewed and classified into either a bone marrow edema pattern (hypointense T1, hyperintense T2) or a sclerosis pattern (hypointense T1 and hypointense T2). Patients with typical findings of osteoarthritis were excluded from the sclerosis category.
Results: Condylar marrow signal abnormalities were present in 37 patients (9%). Twenty-six patients (6%) had the edema pattern, 14 patients (3%) had the sclerosis pattern, and 3 patients had both. Two patients with the edema pattern had a history of surgery; five patients with the sclerosis pattern had a history of surgery. The only follow-up MRIs obtained in the 37 patients were on one patient with edema at 8 months and on one patient with sclerosis at 10 months. MRI demonstrated a stable appearance of these patterns.
Conclusion: It was concluded that condylar marrow signal abnormalities are not rare in patients referred for TMJ MRI. The clinical significance of the changes is uncertain.