QUENTIN ANDERSON a99

J Oral Maxillofac Surg 57:899, 1999

Discussion

Osteonecrosis of the Temporomandibular Joint: Correlation of Magnetic Resonance Imaging and Histology

Quentin Anderson, MD Chief, Department of Medical Imaging, Associate Professor of Radiology, Universiiy of Minnesota, Minneapolis, Minnesota

This report of 44 patients (50 temporomandibular joints) is interesting reading but, as reported by the authors, has only a predictive value of 54% (ie, a 50/50 chance). The study construct is also flawed (ie, no randomization of patients, no normals for biopsy, no localization of biopsy relative to magnetic resonance imaging [MRI] findings, no longitudinal data [no imaging before clinical failure], and the reported cases are all intermediate to late stage [closed lock to potential perforation]).

The findings of MRl bone marrow edema are nonspecific (ie, conditions such as transient osteopenia osteomyelitis, tumor, or stress response need to be ruled out). The case reports show no specific findings, such as a crescent sign or double-line sign, as seen in osteonecrosis of the hip.

The core biopsy techniques are inconclusive in that they were not site-specific. The biopsy sites were not correlated with the MRI findings, nor were there any supportive studies to validate marrow pressure or marrow flow pattern. Also, there are no secondary studies to validate increased venous pressure.

When the blood supply fails, bone marrow cell death

occurs in hours to a few days. None of the 44 patients had time-related MRl studies. Only treatment failures were entered into the study, with no prelongitudinal or postlongi- tudinal images for documentation of the MRI findings.

In addition, the patients’ symptoms should not and cannot be correlated with marrow edema or the presence of joint fluid. Pam production relative to chemical mediators within the joint fluid has been documented. However, in this study, no joint fluid analysis was done. Marrow edema is not a predictor for joint pain.

The authors do point out that none of the patients in the study group had risk factors for osteonecrosis. There were no patients on steroid therapy, and no cases of vasculitis, alcoholism, significant trauma, coagulation problems, and so on. As a general rule, osteonecrosis is rarely seen in healthy patients.

In summary, those cases with positive biopsy and positive MRl findings correlate with altered bony morphology (degen- erative changes, remodeling). The disc position was also abnormal in all of these cases and, as such, joint mechanics and function were at risk. The positive bone biopsies that were obtained are probably a reflection of ongoing remodel- ing, or a stress-load relationship secondary to altered tempo- romandibular joint biomechanics.

The merit of this study can only be validated if longitudi- nal data, a 3- to 5-year data collection, is obtained. Without longitudinal data and correlation with preimaging and postimaging studies, assumptions are not validated beyond a 50/50 random chance occurrence. The supposition that osteonecrosis preceeded alteration of bony morphology is not substantiated by this study.